The Dinah robot is coming along well. I modeled the full steel skeleton in CAD to match the dimensions of the Dinah base mesh and created a human bones variation as well to compare that to the steel simplified skeleton and make sure all the joint pivots matched the locations of the human skeleton joints pivot points. With this CAD, I will be able to modify the proportions of the steel skeleton I have on hand. I also added several key additional joints using reference photos of a skeleton I found online. For example I now have 2 pivot points for the knee joint instead of one which gives more clearance when knee bends back. I also gave a few more degrees of freedom to the neck and shoulder area. Note also that I am well on my way to finishing up printing ABS solid infill fingers and wrist bones which I will retrofit onto the steel skeleton so that I can have full 27 degrees of freedom robot hands and wrists to match perfectly the dexterity of the human hand, which is a must. I have decided that once I finish the arm and head, I will not go on to complete the building of the rest of the robot's body but instead will switch my focus to the AI entirely from there forward. I will code the AI to cause that arm and head to build the rest of its own body.

>>34016 > I will code the AI to cause that arm and head to build the rest of its own body. This is a pipe dream, and completely unfeasible. If you go down developmental road your project will never progress behind a tote of printed parts, a used masturbation skeleton and a half-baked, incomplete attempt at code. Be more pragmatic. There is zero (0) chance of you being able to get a simple robotic arm and hand to assemble anything close to as complex as itself. Think about the wire routing, the fasteners hell, think about literally any point during the assembly of the arm in which you were required to use both of your hands simultaneously. Assemble the robot seeing as how you've already made progress on that front. That's the easy part. After that, get to work on the software side. Even if you only have a fancy animatronic, any effort made after that will have a ready test platform. Set smaller goals for yourself and you'll make progress.

I have absolutely zero use for or interest in a robot that cannot build the rest of its own body with one arm/hand and a head. Therefore stopping all further building after the bare minimum hardware of one arm and one head are completed is the only reasonable path. It saves the time of me doing future building myself which the robot could’ve done for me. It also acts as the final conclusion of the project accepting total failure if my AI does not bring about the building of the Robó body using just that one arm. I would accept defeat at that point. There would be no purpose in building the rest of the body, shy of an AI that can do that. This is where the rubber meets the road. If I fail the AI, then I had no business building a robot to begin with because the only robot I would ever be interested in is a robot sophisticated enough to build its own body with a single arm and head. For times where it needs that second hand to be able to do something, I obtained the necessary extra robotic helping hand simple pincher toy to fill in the gaps where this fully dexterous human hand needs a little bit of help. Also, it can use the usual vise or electronics helping hands for additional options for it to hold things while it works on them. If I had those options, I could build the robot one handed.

>>34019 You're setting yourself up for failure. This isn't "where the rubber meets the road" this is "where the project stops making progress". I get you have ambitions, but you're jumping ahead too far; no proof of concept, no prototype hardware or software, no practical understanding of the problem. Even if you were to go down this path with all of your effort, you would still need to take smaller steps that you seem to be unwilling to take. For instance: a small goal of getting your robot arm to assemble a simple structure. Say, screwing six fasteners of various size in to a block, and routing a wire into a channel of extruded aluminum; things that will be analogous to assembly of your completed design. Make that happen and sure, you're on the road towards what you want to do. But you're either grossly underestimating the difficulty of that problem or willingly abandoning your project with the inbuilt excuse of "I'm working on the AI, and until that's perfect this project is meaningless." Also this doesn't save you any assembly time. Printing and assembling the parts will take a small fraction of the time that programming and troubleshooting even the above example experiment would take. You're shooting yourself in both feet.

I managed to get Dinah's hand bones printed out in ABS (100% infill) on my Anet A8 3d printer the past couple days. I also cleaned up the prints, removed the supports, and sanded down high points. They are ready for attaching them together with cloth tape which will act as artificial ligaments. You'll note I fused the ulna and radius bones together to use as a rotational joint for the wrist to function like a human wrist. The actual pronation and supination of the forearm though will happen by way of the steel skeleton having a rotating pivot point unlike the human body where the radius rotates and twists over the ulna in a criss cross. Note: in this photo the middle finger is missing the distal tip which I was reprinting as the time of this photo.

>>34016 >That skeleton and metal frame Been there, tried to do that, one of the worst mistakes in my life. Your steel bones were never meant for a robot. They will never be meant for a robot. I say this as someone who truly wants you to succeed, this is a dead end. I failed already, you don't have to repeat my mistakes. You may have many arguments on how you can still move a high mass frame. You may have arguments on how its movements are good for a robot actually. They won't hold up to reality. You're free to ignore my warning. I'll just be sad to see you wasting time. >Using AI to have the machine complete itself after just an arm and a head. I'm unsure on how you could possibly think this makes sense in anyway. The level of dexterity and complexity needed is beyond what anyone on earth has ever built. I say this as someone who works with arms in manufacturing, they cannot build themselves. It requires many specialized machines working together in perfect sync with human help. There is no AI that can out think a man, and no man can build an arm that can build a humanoid on its own. >>34019 >If robot cannot build itself; Then no interest You're either operating under a tremendous burden of hubris or delusion. Please, scale back your your project. You could still build something that benefits humanity. It's depressing to see a bright mind waste itself on a project with a scope that eclipses all reason and sanity. >>34020 I dislike their tone but, they are correct. >>34021 >ABS >Cloth tape ligaments That's going to fall apart. Cloth tape won't securely adhere to ABS long term. Using fasteners such as screws would keep things together long term. It's plastic, you just need to place the right sized hole and the screws will self tap. It's an easy fix. Frankly, your hand should be one peice with flat sections for living joints. That would be far more functional, easier, and last a heck of a lot longer. Please, take a step back and think of how to kit is simple smartly. https://hackaday.com/2023/05/01/hinges-live-inside-3d-prints/

Just weighed the steel skeleton - it’s 8lb 11oz

>>34022 >I dislike their tone but, they are correct. That's me. I'd like to clarify, if there's any ambiguity, that I am not wishing this project or its designer any ill will. I'd like to see everyone on this board accomplish what they set out to do. I mentioned it before in my embassy post, but I truly believe that great strides in the world of humanoid and companion robotics can and will be made by very talented, passionate and bright people like those found here. I'm not trying to be negative, I am trying to clearly express that this ultimatum that the designer has set for himself is a mistake. Progress is seldom made in tremendous leaps, and things like this require iteration. Look at the minds behind some of the most impressive robots out there and examine their design paths. Skipping directly from "first iteration robotic arm and head" directly to "self-assembling sentient automaton" is entirely unfeasible and tantamount to abandoning the project entirely. OP, look to your peers on this board alone. We've seen many projects fall by the wayside after more progress than has been made on this one as a consequence of much more benign factors. You should do everything you can to avoid sharing their fate. If I were to offer more direct advice, it would be to set a flowchart of goals for yourself: head and arm -> object tracking with head -> reaching for tracked object with arm -> simple manipulation of object with arm -> construction/refinement of second arm and existing arm -> integration to torso and beginning form factor -> simple integrated AI system (speech recognition, LLM support, facial recognition etc.) -> enhanced object tracking and utility capabilities -> refine form factor -> locomotion (first iteration: wheeled dolly with skirt or similar)->.... so on and so forth. The fact that you've made this much progress shows that you have the capability to make something remarkable. It'd be a tremendous disappointment to yourself and this community to see your efforts come to nothing. Honestly, I want to see you succeed.

In these photos you can see the progression of going from the stock wrist to an axial rotating wrist assembly acting as a plain bearing. Pardon the Orgrimmar welding its a cheapo welder. The process involved cutting the bolt head off then grinding smooth the threads and then sliding on a stack of washers and welding the last couple washers into a mushroom head end stop then welding the other washers to eachother and these ones are to spin freely. They will do the pronationa and supination. This replaces the need for a ulna and radius for that purpose, simplifying the skeleton some. The metal outcroppings I left on the washers were meant to jut out significantly to give the fiberglass something to bite onto well for a dependable attachment. Note: The stock skeleton does rotate already at a spot just near the elbow but that rotation is stiff and requires significant force to get it to move and loosening it is something I don't know how to do. I don't even know how it works at all. Advice on that for future reference would be helpful. Note: There is too much clearance on the stack of washers so they can slide distally or proximally a good 8mm which is not okay - too much play. I need to fill that gap and lube it all with white lithium grease. Note: I'm planning to probably just go fiberglass wraps over and over onto the stack of washers to grip it tightly and build outward from it and then go out and around the welded mushroom cap and then wrap onto the ABS wrist ulna/radius fused section that the little wrist bones will attach and rotate/roll on. Also note that I have reconsidered adding a dual hinge to the elbow joint and lean now toward just leaving it stock. I think the double hinge would add complication to the bicep attachment and cause some issues I'd rather avoid. A single hinge is easier to deal with IMO. And leaving it as stock as possible is a time saver. Of course, when I say leave it stock, that just refers to the overall design of the joint. I still have to loosen the joints to allow for free rotation.

So I finally got the wrist done. And aside from grinding off welds on bolts and backing off the bolts to allow for free movement at joints, I'm mostly going to try to keep this skeleton stock for the most part. So I may be attaching the hand and going immediately into electronics rather than fiddling with the skeleton adding more range of motion here and there. I can always add that later anyways. And in fact the poseable joints that are fairly stiff I'm finding is actually pretty convenient while working on it so I may only free joints on an as needed basis for testing electronic actuation of that joint. Until then I'll leave them alone. Also note: I was planning to have the wrist rotate axially around the location of the wrist for the pronation and supination. However, I realized this will not look right since you can visibly see the forearms move and the muscles there moving when you pronate and supinate your arm. So I have to have the pronation and supination be where the skeleton was originally doing this near the elbow. This will allow for much more natural looking pronation and supination. So the wrist location will not rotate AT ALL after all. This made it all the easier to make the ulna and radius distal wrist joint where the little wrist bones and hand will attach to and rotate on. I sculpted it all in fiberglass and super glue with some nails and some ABS plastic pieces and epoxy to build up the shape. I used my ABS 3d print of this part as reference only. This thing needed to be very strong as it's likely going to the point of failure as the rest of the arm is steel. So I wanted to make sure it was maximally solid and didn't fully trust just going with a 3d print there.

I predict this is all going to be amazing in the end, Artbyrobot. KEEP.MOVING.FORWARD. Cheers, Anon. :^)

I'm currently working to sew all the finger and wrist bones together for the Dinah robot and mount them to the arm. I wanted to show how I'm doing this process. First, I tape the bone with adhesive transfer tape 3M 300 LSE. Note that I leave space on either end of the bone to allow some free fabric which is necessary to allow for elasticity as the bones need to rotate after all. Have to have enough free fabric to stretch as the joint rotates, allowing the rotation. But not so much free fabric that the joint is loose either. Has to be just right and snug. Next I wrap the compression workout shirt fabric onto the tape and cut it to size. The sewing is done with nylon upholstery thread and a curved suturing needle and a surgical pliers using a suturing technique.

Okay, so I finally got the Dinah robot hand sewn in and it is looking pretty good. The fingers could use some tweaking but overall I'm quite happy with how it came out. It's solid and fully articulated. Now that out of the way, I want to announce I'm officially rerouting the Dinah project as far as its current goals and here's why: so basically I was thinking it would be nice to just crank out a working robot using some shortcuts and just do something quick and dirty as a learning experience side quest to get something going. It seemed reasonable at the time. Plus I could pace myself to match the build pace of a fellow roboticist and loosely follow his project's designs. But some things I missed in this decision: #1) I'd be lowering my commitment to excellent quality with no shortcuts - ignoring the adage "do it right the first time" #2) by cutting down on workmanship maxing, I'd be inviting harsh criticism on the new lowered bar of build quality which is the last thing I need when already inviting heavy criticism for a extremely ambitious set of goals to begin with #3) I'd be going against my outspoken commitment to campaign against loud metal gear noise based robots that are completely impractical for home use due to sounding like a construction site #4) it would take away from the focus on my "real" robot projects by creating a "ghetto" side quest robot that could have just been skipped altogether. #5) this would in turn delay me truly solving downgearing by pulleys and actuating the robot arm silently once and for all, proving it can be done and proving that achieving a fully human level DOF human body while maintaining a human form factor and making all of this silent can and should be done for humanoids. So is Dinah robot just trash now? No. I still plan to have this project be done, but only while using the best methods I have including silent BLDC motors with silent pulley based downgearing.

Here is a progress update on the silent pulley downgearing system I came up with using thumb tacks and a #2 fishing crimp sleeve and little plastic discs. It is some tiny fine precision necessary work but I'm getting it done and things seem to be looking pretty good so far. For now, I ended up just using 401 glue to glue the thumb tacks down onto post it note paper. I then put another coat of the glue over the tops of the thumb tack heads to secure it further. I am planning to use nylon upholstery thread lashings to lash all the tacks down onto the top of the 2430 bldc motor tightly and glue the lashings down as well in order to make the thumbtacks even more solidly set into place. Now I'll grant welding them down would be ideal, however, not having a micro tig welder made yet (future project), I just wanted to get going fast and I thought with enough care, it is possible these can be constructed solidly enough with composite material techniques to function reliably. I'm crossing my fingers. We'll see.

>>34087 >while using the best methods I have including silent BLDC motors with silent pulley based downgearing. Good choice. The noise problem is generally one of the big concerns I have.

>>34087 Remarkably meticulous work, Anon. Cheers. :^)

I got done cutting out the pulley discs and drilling them and mounting them to the thumb tacks and gluing them in place with 401 glue using a sewing needle tip as the applicator. They all are reasonably square and solidly in place I think. Everything is moving freely. Everything seems lined up okay. I then mounted them all to the 2430 bldc motor. These thumb tack based pulleys still need to be lashed down well and the lashings (upholstery thread) need to be coated in 401 glue to make them stiff and solid. I also need to add pulley discs to the 2430 bldc motor that are to line up well with the pulley disc slots the string is to go to. I then need to wind up the string sections themselves, loading up the system in preparation for actual testing.

I wound up my 6lb test Hercules PE braided fishing line onto the previous pulley system setup only to find out that the pulley could only handle about 21 inches of fishing line wound onto it before it started to come dangerously close to overfilling the pulley. The aim is to have plenty of the plastic disc overlapping the fishing line even when it is wound up fully to one side because that plastic disc acts as the guide to keep the line in its proper channel. I want at least 32:1 mechanical advantage out of this downgearing so if I want my final output to be 1" then the first pulley has to be able to wind 32" of fishing line onto it comfortably. So I realized at least the first pulley has to be a few more millimeters increased in diameter. So I had to rebuild the thumb tacks arrangement to accommodate these changes and make that first pulley bigger. With this increased size first pulley, I realized I'm getting what looks to be 7:1 mechanical advantage from just the first pulley alone! At least initially when it starts. As the fully wound up pulley gets winched in by the motor, the relative size differential gets smaller which means it will speed up and the torque will be less than the starting torque and increasingly so as the size differential decreases. This will create a natural sort of acceleration effect and high initial power and gradually less power. I think these side effects of this system seem to be quite good but I'll know for sure in testing. The next steps will be to wind up the reverse direction of the first pulley and start connecting the first pulley to the second pulley and so on. I may not even need all 5 pulleys but we'll see. With the first pulley being already 7:1, if the remaining 4 are 2:1 say, then we'd have 7:1, 14:1, 28:1, 56:1, 112:1 so 112:1 would be the final output. That seems quite overkill and perhaps will be too slow. Although very strong. The motor outputs about 0.42 lb on average so .42*112= 47lb! Now the lever of the joint itself makes you lose mechanical advantage due to the fulcrum location etc so it would drop down to say 15lb but my finger individual joint flexion power is only like 5-7lb so that's double mine. So a bit overkill. So I might skip using one of the 5 pulleys. Having it there is nice though just in case we wanted to trade speed for power for some of them we'd then use that one as an optional strength boost we can tap into in the future if we want to trade speed for strength so I might just leave it in the design even if I don't use it just yet. In testing I may find I prefer to use it afterall. Nice to have that option if needed.

So it turns out that when the forward and reverse directions portions of the thumb tack pulley downgearing system are doing their thing, they won't always have the same mechanical advantage and so will be moving at different speeds. Therefore, I have to treat the forward and reverse pulley systems as entirely separate systems that have to be completely decoupled and handled independently, each pretending like the other one doesn't even exist. They can share the same thumb tack, but have to be decoupled. So I cut the #2 fishing crimp sleeve in half using my miter saw and have to redo the plastic discs phase. Each half #2 fishing crimp sleeve will have 3 plastic discs, one for outside of the larger diameter pulley and one for the outside of the smaller diameter pulley and one to split the two. Three total. And so with 3 plastic discs on each half crimp sleeve we have 6 total discs per thumb tack. We only had to deal with 5 before so things will be even tighter but it's fine. We have enough room. Next, since both sets of pulleys have different speeds that vary over time, the one that is not being actively winched in at any given time will be randomly releasing slack in a chaotic way. This can lead to tangling and all sorts of problems. To resolve this, we need a automatic slack tensioner system to aid the pulley system by keeping this releasing group of pulleys in a state of good tension at all times. This I will resolve by the pictured method. So basically a tension spring connected to a metal eyelet will at all times be trying to pull the fishing line out of alignment and draw slack out of it. So as looseness is detected, it will immediately draw that in removing it from the system maintaining taughtness everywhere at all times. This will prevent the pulleys from getting tangled or anything like that. This setup can be placed anywhere in the path between the pulley system and the joint the pulley system is to actuate.

I hardly know where to start commenting on your work, Anon. You've already done much research, and have what I consider a very innovative plan. I'm very-much enjoying watching the progression of your many ideas into reality, Artbyrobot. Please keep up the good work, and also please keep us here all up to date with your adventures in developing these two robots of yours. Cheers, Anon. :^)

I started some testing on just the first pulley and lots of things went wrong: Twice I had to increase the pulley size because I wasn't able to use enough line winding onto said pulley for my total line draw need after accounting for the 32:1 downgear ratio. I calculated 27" as the very least it has to winch in at the motor shaft to get 0.84" total draw at the joint of the index finger which is perfect (27/32=.84). The pulleys were too small to accommodate 27" winched onto them so I had to increase the size - which meant removing everything, increasing size, then rewinding everything by hand for an hour plus! Just so tedious and annoying! Another failure was one time, the string was too loose on a pulley and a tighter wrap got under the looser wraps and then the looser ones snugged against it binding it down like someone said would happen - which made it all stuck. Also I had many derailments where the string came off the pulleys and started wrapping up on the axle off all the pulleys and getting things quite stuck that way. I've been dealing with carefully untangling and rewinding tangled messes over and over. It's been a disaster. I thought of scrapping the whole thing a couple times. However, after taking a step back, it occurred to me that the tangling issues were largely due to forgetting to put the final outlet of the system under load to tension the whole system which would keep every pulley winding nice and tight and aligned well. So this was user error and oversight, not the fault of the basic concept of the system then. I just forgot to do those parts in my rush to start testing things. I planned to only add that stuff at the very end once the whole system was done and did not think I needed to do that just to start initial testing on a single pulley. That was a faulty assumption and an oversight. The whole system always has to be under tension to work right. My bad. Lesson learned and a valuable one at that. I did not fully grasp until I saw with my own eyes the disasters the importance of keeping it all under tension at all times. Yes I knew theoretically it was needed eventually, but I did not realize the whole thing was absolutely doomed instantly every time if it is not immediately under tension even for a first set of simple tests. That was revelatory for me. I'm glad I got to see the failures first hand though because it enabled me to study what failures can be expected when tension is not placed and know intimately first hand the importance of tension and how lack of tension causes the failures specifically. Valuable to see it with my own eyes instead of only imagining it. This has helped me come up with some cool derailment prevention and loss of tension prevention mechanisms to fool proof my system more - even beyond the tension spring drawing shown in my last post. Note: At the top of the motor output shaft, you can see two large pulleys where I have wound 2 pulleys for moving the motor axle clockwise and counter clockwise to simulate the motor moving. These are temporary windings just for testing manually without messing with electronics for now. These need to be fed in under tension at their inlet and their inlet needs to have a eye positioned in front of it that forces the string to stay in line and not feed in astray out of alignment. So also the pulleys for the main motor output shaft pulley for flexion I'm testing and the first pulley downgear I'm testing. Every place a string enters a pulley needs to have a small eye that guides the string onto the pulley perfectly in alignment with the plastic discs of the pulley and prevents it from derailing. I noticed that when feeding string into a pulley I intuitively hold the string between thumb and index finger and pull the string away from the pulley as its being fed into the pulley to apply tension on the line and tight wraps on the pulley. I also align the string with the center of the pulley and hold my fingers at a minimal distance away but not too close. You want the string to be able to easily angle up and down from your finger pinch point to ride up and down the height of the pulley creating layers of wraps evenly as opposed to all wrapping in one area and not having a well distributed wrapping. If you study how to wind a bobbin on the top of a sewing machine, you see the string take 3 turns and go through a metal wheel that places tension onto it and only then does it enter the bobbin which it then winches onto the bobbin rapidly to wrap up the bobbin with string. These are all designed to create tension from the otherwise loose and floppy string leaving the main spool of thread you are feeding into your empty bobbin. I need to create a similar type of tension system to feed onto my pulleys which are acting just like that bobbin and need the same type of setup to succeed. To create the eye that centers the string and forces it to neatly stay on the bobbin and not derail so easily, I plan to use 28 ga tinned copper bus wire. I will cut out a small section of that wire and glue it to the base platform the thumb tacks are glued to and then run it vertically and then form the eye shape that acts as a guide and derailment preventer. The eye will just be a oval with a couple legs glued down with 401 glue to hold that oval into position. For the tension maker, I'm planning to use just a couple windings of tension spring with two small square pieces of plastic which will sandwich together and be pinched together snugly by the tension spring and the fishing line will be fed through this. I will use the same produce container plastic I'm using for the pulley discs. The fishing line will not be abraded/damaged by this in theory but only some pinching force applied to it to give it some tension and cause its feeding action of winching onto the pulley to be tight and snug to help prevent derailments and tangles and loose wraps. This system is meant to emulate and replace holding the string snugly between thumb and index finger as it's fed into the pulley tightly.

>>34224 >Valuable to see it with my own eyes instead of only imagining it. You have a great analytical mind, Artbyrobot. You're able to dream up good ideas, and then figure out how to approach implementing them. But nothing matches experiencing when "the rubber meets the road". Imagination is by far the most important, but as they say 'experience is the worst teacher', and 'hindsight is 20/20'. You're making progress, Anon. Keep it up! Cheers. :^)

I managed to implement a friction device for both main manual input pulleys for manually turning the motor shaft and one for creating tension on the system at all times. The former I made by just running the fishing line through a tension spring between the coils which pinched the fishing line enough to provide friction and feed it snugly into the motor shaft as it winches it. This successfully replaced the need to feed it in by hand between thumb and index finger with snug pinching action to get it to winch in tightly. For the tension on whole system need, I ended up just hanging a bolt from the final output string which put the whole pulley system under light tension. You can see the tension springs sewn into the bone fabric on the left hand of the pulley system in the attached photo. You can also see the thread going through those if you look carefully. You can also see the output pulley on the right hand side of the system and see the little metal 28ga wire eyelet I made and the string being fed through that eyelet as it heads toward the camera lense shooting the photo. It then drops down out of sight. So you have to visualize it tied to a bolt. The bolt is currently taped off to a piece of bone since I removed the tension after testing to do some repairs. So to the results: with these little modifications, the testing went much better. It was fairly reliable. The only times anything tangled up was when the bolt caught on something when I wasn't paying attention which relieved the pulley system momentarily of the tension created by the weight of the bolt pulling down by gravity and tensing up the system. As soon as the system lost that tension, it began to unravel and created a tangled mess. This happened a few times in testing and was user error. Although one time a pulley just stopped turning randomly despite the tension created by the bolt. That concerned me alot. I don't know if something got wedged in it or it was cockeyed just right or what but sometimes it gets stuck a bit. That cannot happen ever or the whole thing fails. Perhaps greasing the inside of the fishing crimp sleeve would prevent this from happening anymore. Also, the bolt is not THAT heavy. Using something with a bit more tension force placed onto the system could also help some more perhaps. I think using a tension spring as the tensioner - as shown in a drawing I posted previously - will be just the right amount of tension. I think it might pull a bit harder than the weight of the bolt was pulling. So between those two improvements I think this rare fluke will be avoided. And so far, as far as I've seen, as long as the pulleys spin freely and no tension is lost, everything appears to work perfectly. I was able to go back and forth with no issues many times besides the few screw-ups I already mentioned. So the system appears to be a success so far from testing. I can now move onto building pulley #2 and 3 and testing them thoroughly in conjunction with pulley #1. Also of note: I thought pulley #1 was a 3:1 ratio and perhaps it is at times, but the mechanical advantage ratio changes over the course of the winching process because the larger pulley gets smaller as it unwinds and the smaller pulley gets bigger as it winds up. So their relative diameters changes. Therefore, I guess we have to treat it as what is the average mechanical advantage it produces. Well in the final measurement, it cut down the original 27" of string being winched in to 13" of string on the final output. Trading down that distance of travel is the key to the creation of mechanical advantage. We want the final output to be around 0.84". We want 32:1 mechanical advantage in the end. So pulley #1 got us to 2:1 mechanical advantage only so far. The next pulley likely will get us to around 4:1 and the next one 8:1. I am considering just stopping there. I have room for two more pulleys, but at the moment I'm considering doing the last two down-gears with my Archimedes downgearing pulley design. I think that method might be a little more robust and I kind of just want to use both methods at this time. Both have their pros and cons. I feel using both methods can help me learn which one is superior and learn to perfect both as I see which one is more durable long term, which one has more incidents, which one tangles from time to time and why and resolving those issues if they come up. The great thing is this: the compact pulley method (thumb tack method) is giving us 8:1 downgearing roughly. Of the 27" of total draw, that brings output draw at that point down to 27/8=3.37". So the final two downgearing stages will be reducing 3.37" draw down to 0.84" draw. So 3.37"/2=1.68" then 1.68/2=0.84". So the Archimedes pulley system only needs TWO pulleys (down from whatever huge number we had before in our previous monstrosity of wraps and turns we had to do). To make just two pulleys is a piece of cake. Also, given 3.37" is all we are working with for the first pulley, and the pulley is equidistance in the center of that stretch, the total draw length of the two string halves wrapping around that first pulley is only 1.68". And the next pulley's total length is .84". So 1.68+.84=2.5" give or take is the total length of the pulley system for this. This edition of the Archimedes pulley system adds 4:1 downgearing to the compact thumb tack pulley system's 8:1 downgearing. Giving us a total of 8x4= 32:1 downgearing. That 2.5" total length Archimedes pulley system setup is so small compared to my original 16:1 Archimedes pulley system I published earlier that it is a lot more practical to use and we still save a ton of space.

Note: I could do the rotate in place style pulleys but just put them on the forearm instead of the motor as the motor is already getting quite cramped and tedious to work with. Or I can do Archimedes pulley system style with pulleys that move lengthwise along the forearm. Both styles are good. I lean toward the latter though at this time. Both would work though. I kind of just like the variety for learning purposes but I'm not 100% sure on this decision. Note: an advantage to completing the final 4:1 downgearing on the forearm closest to the finger joint is the total distance of string travel from the motor to the finger joint and the total bends it takes all adds friction and when that friction is placed with a large force on it, it is harder on the teflon guide tubing. But by only doing partial downgearing at the location of the motor and saving the next phase of downgearing for being closer to the finger joint in question, we avoid a lot of forces and frictions in the teflon guide tubing running longer distances to get to the finger. In some cases, I have motors intended to actuate finger joints placed in my CAD as far away from the finger joint as the upper spine area and some in the lower latimus dorsi area! That is a LONG travel to go across the torso, past the shoulder, down the humerus, past he elbow, down the forearm, and then FINALLY to the finger joint it is actuating. That is a LOT of friction and turns introduced. So to navigate such long distances, it is ideal to have it be just high speed low torque during that time-frame and only beef up the torque with downgearing NEAR the finger joint it is actuating. Note: the fishing line selected for downgearing while in the early phases of downgearing gets to be very fine low test strength fishing line like the 6lb test braided pe fishing line I'm using here. However, as the downgearing progresses, trading speed for torque, so also the fishing line selected for these sections needs to progressively get larger in diameter to accommodate the higher tensile forces involved. So we'll be graduating from 6lb test to 20lb test then 70lb test then 130lb test. So we'll be changing fishing line diameter 4 times in the routing from the motor output shaft to the joint itself! That said, keeping the downgearing near the motor minimal is best since it enables us to use the finer diameter fishing line for the long travel distance from the motor to the finger area. Then only once near the finger do we do the final downgearing stages and beef up to the larger diameter fishing lines. Then another advantage to all of this is the teflon tpfe guidance tubing we are using as guide tubing gets to be smaller diameter guidance tubing for those long fishing line runs. This saves space and enables us to make tighter turns without as much consequences in terms of wear and tear on those turns and tension/friction concentration at those turns. Also, when making turns AFTER full downgearing, the higher forces involved tend to want to crush and deform the TPFE tubing - which is why sometimes metal spring is used on the outside of the TPFE guidance tubing to make it into a Bowden cable and reinforce it to make it non-collapsible under the high tension forces that get involved by that point. We avoid all of this by keeping the downgearing at the location of the motor more minimal. Note: that all said, our downgearing at the location of the motor thus far is planned to be 8:1. The motor outputs .45lb at our distance from the center of the motor shaft roughly. So 8x.45= 3.6lb of tension force as the output at the motor then. This means we get to use our 20lb test fishing line for the long travel from the motor to the distal forearm where we will do the final 4:1 downgearing bringing us up to 32:1 downgearing. That 20lb test line is only 0.2mm diameter so it and the TPFE guidance tubing we pair with it is very fine and can easily weave its way past everything and get to the distal forearm without taking up too much space or having to be reinforced by metal spring to prevent crushing or distortion of the TPFE. At least not in theory. If this proves not true, I can always add metal springs to any sections that are getting crushed or distorted to reinforce the outer diameter of the TPFE guide tubing in those areas - probably areas near tight turns? We want to take as few turns as possible though and make the turn radius as large as possible to cut down on friction as much as we can during the fishing line routing runs.

This is a slow, careful hand test of the pulley. Everything looks good. Also, I did fast tests but didn't capture a nice shot of those with good hd closeup like this. In any case, this can show you some idea of how it all looks in action so far. The motor shaft is not turning electronically but is being turned by me pulling string wrapped around it to screen left is my hand pulling. To screen bottom is a hanging bolt that is being winched (not shown its cropped out of the image). I wanted to avoid working on the electronic actuation which is a rabbit hole in itself until I have the pulley system fully done and tested. THEN I will make it all work electronically as the next phase.

After further deliberation, I have concluded that I should put 4:1 downgearing on the motor's top with the turn in place pulleys and put 8:1 further downgearing located nearer to the joint being actuated - in this case the distal forearm. My reasoning for this is as follows: the routing from motor to near the joint is facing turns and friction etc and these become smaller factors when under lesser loads. So leaving things more high speed low torque initially during this phase of the routing is advantageous to lower friction and issues relating to deformation and compaction on the guidance tubing. This means less wear and tear and lower maintenance as well. Next, the turn in place pulleys are quite difficult to work with being very small and compact and lots of winding and whatnot is hard to deal with and tedious. Further, the turn in place style, when fully winched in has a much lesser downgear ratio compared to when fully extended due to the relative diameter size ratios of the pulley pairs involved changing in size during the winching. Whereas in the Archimedes pulley downgearing system the mechanical advantage is fixed and doesn't change during the entire flexion nor extension process. This makes it more reliable and limits our losses during the near end of the winching phase that are incurred in the turn in place technique. This ensures we retain adequate mechanical advantage during all times. Another important update is I have added axial rotation to the proximal finger joint in CAD. My index finger has a little bit of this type of control to it so I think it will be a nice boost to control and dexterity for the robot. Really maxing out the ability of the robot to finely manipulate its finger positions and improve performance of the fingers at all tasks. I added the necessary 4 additional motors to achieve this into the CAD as well. You can see the highlighted pair of axial rotation red indicator arrows which show the angle and location of the tendons from where they terminate to where they will exit the guidance tubing - the range of motion if you will. Yet another important update is I now plan to just use a spring for the extension actuation force rather than the reverse direction turning of the motor. This is admittedly going to give the extension less strength and the flexion less strength. The flexion will have less strength because it is now fighting against the extension spring to get the finger to flex. The extension will have less strength because a spring alone is making it happen rather than a strong motor making it happen. I don't mind either of these trade-offs though because it will greatly simplify the routing - cutting it in half, simplify the motor mounted pulleys, cutting it in half, and simplify the Archimedes pulley systems, cutting the amount of them we have to make in half. That is just a massive amount of time and effort saved. I just am not convinced that spending that level of time and effort just to have a stronger extension of the finger joints is worth it. Relatively passive spring powered extension of fingers is very common in hobby humanoid robot hands from what I've seen and although I've always viewed it as a lazy solution, I do see some merit in embracing more simplicity at times. Especially if you cannot JUSTIFY the added work of the alternative. The more I think about when I have needed finger extension to be very strong, the more I find that it seems to be a relatively rare occurrence. It just doesn't seem to happen often. Now as the robot grows more able with its AI and more sophisticated, and gets into more and more types of work, the occasional scenario where fully powered extension of fingers will start to crop up more and more as a need. So at that time, I am thinking we can revisit this and get the extension actuation installed. So I still plan to reserve space for it on the CAD and ensure it can be done without any major problems or redesigns needed. It should be a smooth and straightforward upgrade option. But for a minimum viable product that can meet all of my goals, it is not necessary to implement in this stage of development. In fact, it is also possible to just have the robot install these on himself once he's building the rest of his own body. Which means me doing it would be a waste of time if the robot could do it later instead of me. So in any case, this acts as a MAJOR shortcut and time-saver for me and will be a big game changer IMO. I'm excited about it. These types of big shortcuts really move the project forward in development very rapidly in large leaps saving countless hours and I love them. As long as they aren't shortcuts that will come back to bite us later, I'm okay with them. I don't think this one will bite us later so I say let's go with it! Note: it also just occurred to me that the robot could potentially have the extension actuation be in the form of geared n20 motors instead of reverse direction of the main 2430 bldc motors with pulley based downgearing. This would save alot of work but introduce noisy metal gearing to the robot. The reason I think this is okay to do is that these geared n20 motors would be slack lined and not interfere with fingers AT ALL nor be used on any way at all UNTIL the fingers need strong extension actuation - which as I said is incredibly rare. In this rare event, it tapping into these geared n20 motors for some extra oomph to get the extension to actuate harder would solve the problem and the little noise it created would be a rare occurrence type of noise. It would hardly be noticeable then and 99.999% of the time you'd never encounter this noise. The bigger issue would be noise in a common feature like blinking. Now THAT is annoying to hear gears EVERY TIME the robot blinks.

I have added the final pulley and rigged the guidance TPFE tube up to that pulley and routed that to the general vicinity of the Archimedes pulley downgearing system. As seen in the photo, I used super glue and post it note paper to form a TPFE guidance tube support structure to hold it in place as well as wrapped it in fabric tape and soaked that tape in super glue. I applied the super glue with the tip of a sewing needle as a precision application method. The next step will be to test the pulley system as is and make sure everything is working really well. If all testing passes, we will then modify the Archimedes pulley system on the forearm that we were using before to simplify it some since it now deals with only 7" or so of string compared to 27" of string it dealt with when we did not have the turn in place pulley system in place. So it will now be much more compact and fewer pulleys needed in it. So a bit of redesign and part recycling and we'll be good to go on that. Also, before, it was a 16:1 Archimedes pulley system whereas now it will just be a 8:1 system.

>>34260 >so I say let's go with it! I concur. Nice advance, Anon. Thanks for sharing it with us here. Cheers.

I just ran a test of the second turn in place winching pulley and ran into several problems. First I noticed my main lines turning the motor were not the full 27"+ which I thought they were but just remeasured and found they weren't. My bad. So I have to rewind those to fix that. Next, I noticed that just as we depart from the motor output shaft we experience mechanical advantage with each downgearing, so also when traveling from the downgeared area back to the motor output shaft we experience mechanical disadvantage. Up-gearing. Which means the bolt hanging as a load to place tension on the pulleys during a release cycle was not enough weight anymore (was barely enough before now clearly not enough). Now note that the bolt represents what a tension spring will normally be doing, tensing up the winch system to keep it all solid and tight. I don't want this to have to be much heavier than the bolt. I want the system to not need much pulling to remain good in tension. The friction of the teflon tubing plus mechanical disadvantage etc was causing the pulleys to not remain tense (and their not being lubed yet on the junction between fishing crimp sleeve and thumb tack. So my solution I'm now contemplating is either moving one of the turn in place winches down to the location of the Archimedes pulleys on the forearm area and putting the tensioner apparatus between it and the previous pulley mounted on the motor so that the tensioner apparatus does not suffer as much mechanical disadvantage due to up-gearing OR I get rid of the second pulley entirely and just have the winch in place be a single pulley 2:1 and the Archimedes system be 16:1. Which still works as we have then 32:1 which is great still. Under such a system, the original 27" winching would be reduced to 13.5" by the winch in place pulley attached to the motor. The Archimedes pulley system then needs to go down, around one pulley, back up, around another pulley, then down and around another pulley, then back up and tie off. The total travel for those one down, one up, one down, one up (4 trips) is 13.5/4 so 3.4". And we'd sit at 8:1 at that point. so adding two more pulleys beneath that first group would add another 4:1 for 32:1 total. And those two pulleys would add another half inch tops so that gives us around 4" total length of the Archimedes system and not too crazy many turns in that first system like we had in our first prototype. Still quite simplified comparatively speaking. So this is a very viable solution. And that 4" is around 10cm and we had 11cm already planned for this purpose in the CAD in the forearm from before. So we are still within that target and viable still without any change to the CAD at all which is great. Anyways, back to the test's issues discovered. Oh yeah, also, the load (in this case a bolt hanging) struggled to keep the turn in place winches under tension while the motor was releasing the bolt (loosening or unwinching itself) not only because of the mechanical disadvantage from the pulley upgearing itself and from the friction in the TPFE guidance tubing but also from the friction of yet another pulley and its friction between its fishing crimp sleeve and its thumbtack. So I was having to manually pull down assisting the bolt, pulling down fairly hard just to get the system to stay taught and release without becoming a derailed tangled mess. One other work around if I were insistent on going with more than one winch in place pulley would be to wind up extra line onto each turn in place winch pulley and have that directly attached to a tensioner spring placed wherever on the robot. This would always keep tension on just that winch in place pulley and be responsible for just that pulley and suffer no mechanical disadvantage beyond the TPFE guidance tubing it has to pass through to get there which shouldn't be too bad if the spring can be nearby. This is a valid solution but adds another layer of complexity to the winch in place pulleys and now more routing and string to deal with. It also means loads of extra springs to place. Attached is a drawing of the proposed tensioning mechanism for tensioning each pulley individually. In any case, were I to add this type of tensioning apparatus to each pulley and the necessary extra plastic disc and vertical spacing to glue string to the fishing crimp sleeve and wrap it up, that takes up even more vertical space in the system and we were already really lacking sufficient space as is. So to gain the extra space needed to do that, we'd have to extend the height of the fishing crimp sleeve to accommodate this which would then remove the option to add the reverse direction set of pulleys to the same thumb tack. Although that is probably fine now that we were planning to achieve that with just a tension spring as the actuator for extension of fingers instead of motor actuated extension and coupling that with a n20 gear motor for extra oomph in demand on a rare as needed basis for extension action when the tension spring is not strong enough to do it for the task at hand (rare). So yeah, this apparatus would work to solve the issues I'm having with my current test setup I think. But just going 16:1 on the Archimedes instead of 8:1 on the Archimedes pulleys and simply deleting the second winch in place pulley on the motor seems like the best option to me right now. Doing so means the Archimedes pulleys bumps up from 27/4 = 6.75" for Archimedes pulleys to deal with 6.75/4 (for up and down passes around first group of pulleys) so 1.68" in length then another pulley brings it to 2.1" total length compared to 27/2 (only one winch in place pulley) = 13.5" for Archimedes pulleys to deal with 13.5/4 (for up and down passes around first group of pulleys) so 3.4" then add 2 more pulleys so 4.2". So 2.1" vs 4.2". If we keep the second winch in place pulley we shave off 2.1" in Archimedes pulley system total length and shave off one pulley from its system too. Well I think just going 16:1 on the Archimedes is my move here.

>>30954 You have a problem with miniskirts? What, so you can't play Tennis? What about Star Trek?

>>34280 I hope you can devise a tiny & robust little tensioner mechanism that serves you well in keeping thing running smoothly through your spindles, Artbyrobot. This is clearly going to be an important function within your designs. <---> Otherwise, you're continuing to make incremental progress here. Please keep it up! Cheers, Anon. :^) >>34348 Please leave the man in peace. Alternatively, you could even help contribute something productive here on /robowaifu/ instead. :D Sound good, Anon? Cheers.

Okay so here is my latest iteration of my motor mounted winch in place pulley downgearing setup completed. I ended up doing a total overhaul of everything since my last iteration failed. In this iteration I made many small improvements. One thing I noticed is that the thumbtack shafts have a little bulbous section near their tip and I reasoned that perhaps this can catch on the #2 fishing crimp sleeve and impede it at times. So I sanded it off with a nail file so the whole shaft is now a cylinder with no protrusions. When I tested the rotation with the fishing crimp sleeve after this modification, it spun more freely than ever before by a long shot. So I think I'll do this every time going forward. Another improvement is I added more height to the sections of the pulley, taking up all the available vertical space that used to be planned to be used for reverse direction actuation which is now being done by a tension spring instead. The added vertical space on each pulley means that contiguous loops of string wrapping have more space and so the diameter taken up by the string as it winches doesn't change nearly as much as before which means it will have more consistent downgearing through the whole duration of the winching cycle. I prefer this. It is also easier to work with for gluing on the discs and whatnot with them more spread out. Another improvement is I added an extra pulley set on the top of the main winch in place pulley which I will use to attach a string which will be tensioned on one end by a spring and the purpose of this will be to put tension on the system to prevent derailments and ensure tight wrapping every time the winch releases its string (finger extensions). Now I may not actually need this extra tensioner pulley if the spring on the finger doing the extension actuation provides enough tension to the Archimedes pulley system and this winch in place pulley to cause them all to remain snug and tensioned, however, I think I probably should tension this winch with an additional tension spring dedicated to it exclusively even if it is just a redundancy just to play it safe and doubly ensure we get no derailments even when some issue may come up with the Archimedes pulley system. Last thing we need is a cascading of failures like Archimedes system fails so also winch in place pulley then derails and tangles so then we are really set back in the event of some unexpected issue. So better to have this redundancy. To provide constant tension on the winch in place pulley, I have considered using elastic thread used for making DIY necklaces, using a tension spring, and using a clock spring. The latter seems like it could be the best and most reliable option due to its constant tension. I bought a few sizes to experiment with from Aliexpress. Search terms to purchase such an item were "flat spiral coil constant force spring". They are around $2 each. Considering the motor is $24, $2 to have a extra spring isn't too bad. It could really make or break the reliability I think. Now the issue is the spring is suppose to provide tension for all 32" of travel of the winch. That is a long way. My mini tape measure surely has this type of spring in it and it has that tension spring the whole time and presumably uses the same type of spring I just bought. So it is possible for a tension spring to do this for this length of travel. So hopefully one of the ones I bought works for this. If not I may have to upgear it trading tension for more travel distance. I will have to fit these extra springs into the body which may be tough. Space is VERY constrained but hopefully we can pull it off without any issues. In any case, these are going to take a few weeks to arrive so I'll be testing without it at first. Another improvement is I made the diameter of the larger pulley of this turn in place winch bigger which means it will provide more downgearing. Not sure how much maybe an extra 5% or w/e but it's something. I have routed the final output string using the TPFE tubing around the side of the elbow this time and then across the forearm and over to where I have setup my Archimedes pulley system from before. This Archimedes pulley system is getting a total overhaul. Many improvements planned for it. So that is up next, overhauling that. And then I will be ready to connect the turn in place winch pulley and its 2.4:1 or so downgearing with the 16:1 Archimedes pulley downgearing to achieve around 38:1 downgearing in total.

>>34364 This all seems pretty amazing if you get it working. I thought the idea of your tape measure keeping a constant tension both in and out is a good idea.

>>34365 I was suggesting using the same type of coil spring mechanism found inside a tape measure, not using an actual tape measure itself with the measurements at all. Although the latter can be done, I suppose, it would not be as space efficient and it would be a lot more expensive as well.

Ok so I've been now working toward creating the latest iteration of the Archimedes 16:1 pulley based downgearing system and as part of that I decided to remake some of the pulleys with grooved outer races as I had discussed previously wanting to do - in order to prevent the fishing line from walking to a corner of the pulley and wedging itself in between the bearing and the plastic disc sandwiching in the bearing and becoming jammed that way. Previously, we had glued in a very tiny piece of clear thread to block this gap anywhere I found the tendency for jams to happen, however, to create a grooved outer race from the outset is going to prevent this issue all together! So to do it, I took my little 1x3x1mm ball bearing and pinned it down with my left thumb against wax paper on top of a stack of post it notes, so holding it all with my left hand in the air. I used my highest zoom on my visor magnifier to see what I'm doing. I then loaded very tiny amounts of super glue onto my xacto knife with sewing needle tip instead of blade tip and using this sewing needle tip, very carefully placed super glue into the joint where the ball bearing outer race meets the wax paper. I did this for about 1/3 of the bearing then carefully lifted off the pressure of my left thumbnail pinning it down and rotated the whole thing then repinned the bearing down again with my left thumbnail and repeated the process of adding glue little by little. When one side was done, I was able to carefully peel it all up from the wax paper, flip, and do the other side. This needs to be carefully trimmed down still but the idea was a massive success. The bearing still spins freely and the grooved outer race is done! That fishing line can't go ANYWHERE now to jam anything! The photo is just the ball bearing and the glue. So the plastic discs will now be able to go over this and the fishing line won't be able to walk across the outer bearing surface and jam itself between the bearing and the plastic discs anymore! Note: my concern about this procedure was that the glue could potentially walk underneath the bearing and glue the outer race to the inner race and thereby ruin the bearing - but this did not happen! The gap between the underside of the bearing and the wax paper which were both firmly pressed together by my thumbnail was too tight for the glue to travel into there and ruin anything. So the glue only went where I wanted it - which is on the outer race of the bearing forming the intended groove on that outer race. A huge success. I used 401 glue btw.

>>34391 >This needs to be carefully trimmed down still but the idea was a massive success. >I used 401 glue btw. Great job, Anon! Glad to hear you successfully managed this process for such meticulous work. Will you need to repeat this for other pulleys? If so, can you think of some semi-automated way to perform the task to help reduce your load, and also to increase the likelihood of a quality job? Something like some kind of jig (or rig) is what I had in mind. <---> Regardless, glad to hear of the new progress Artbyrobot. Please keep it up! Cheers. :^)

Some more kind of automated way would be nice, however, it really didn’t take that long for this particular stuff at all. Maybe two minutes tops. In any case I wouldn’t start getting into jigs and automation type of stuff until I’ve proven out the entire system with extensive testing and I know for 100% sure I’ll be using this approach. There is still a tiny possibility pulleys fail for some unseen reason and I have to go with metal gears after all and just give up on the idea of a quiet robot. But I’m strongly hoping that will not be the case.

>>34406 >...and I have to go with metal gears after all and just give up on the idea of a quiet robot. But I’m strongly hoping that will not be the case. Yeah, me too Anon. Keep forging ahead, Brother! :^)

Here's a better image of the grooved outer race with more refinement. To refine it I cut away excess glue with an exacto knife and then sanded it with a nail file a bit to smooth it out.

>>34424 It's so tiny. Impressive work, Anon. I truly hope this approach works out -- for everyone's sake. Keep moving forward! Cheers. :^)

Ok so I was struggling to plan out how the flat spiral coil constant force spring would maintain constant tension on my first winch in place pulley the past couple days and I was studying how tape measures use these springs. Then it hit me when a colleague was mentioning belt pulley based downgearing that a belt pulley based downgearing for this first pulley would remove all the issues of derailment and need for constant tension during whole duration of travel a winch style would require in this design. Also, since its just .4lb-.8lb of force for the first pulley downgear, as long as the belt is reasonably tensioned and has some decent grip to it, I should not deal with a ton of slippage issues and the motor's output should be passed along well. So here is my beginning attempt at converting my first pulley to a belt based pulley instead of fishing line winch based pulley. This is made just using adhesive transfer tape applied to one side of a nitrile glove and cut out into a 1.1mm wide strip and applied to the two pulleys directly. Built in place. Early testing shows it needs more layers to have less stretchiness or needs to be reinforced internally with fishing line wraps between layers to prevent so much stretch to it which causes slippage. Also, the motor output shaft acting as the winch pulley is a combination of a bit too small in diameter and a bit too smooth to create a proper grip. So I'm thinking of thickening it up some and adding a grippy surface to it so that it grips the belt better with less slippage. I am considering using silicone rubber to coat the motor output shaft or several wraps of nylon upholstery thread and super glue to thicken it then coating that with carpet anti-slip paint. Or silicone. I'm considering making the belt from a cloth coated in silicone or carpet anti-slip paint and then sewn tightly into place over the pulleys - creating a sewn seam for a tight grip. I'm considering a tensioner pulley but I think that's overkill and should be avoided unless it proves absolutely necessary. I have not explored purchasing options at this time but of course I'm open to look into this in the future. The thing about a premade is it would have to be a perfect fit in both length and width and I'm not sure if that will be easy to find or not. This is all a very new approach so I can investigate that later. For now I'm happy to just move quickly on the prototyping with materials on hand.

Ok so my belt drive system from my last update just is not quite up to par in terms of grip and anti-slippage. So my new series of changes are planned out and underway now. First, I will be bumping up the height of each pulley to 2mm up from 1.1mm. This will double the surface contact area for way more belt grip in and of itself. So then I can use a 2mm wide belt. Next, I'll be increasing the drive pulley diameter to 1.5-2mm additional diameter. This will also greatly increase surface contact with the belt for more grip. Then finally, I'll be using a commercial belt that is said to have the highest grip of all belts - its called a polyurethane belt. It is a flat belt with 2mm width and .9mm thickness. It should be a huge upgrade to my current setup! The best part is you can customize the diameter of the belt by melting the two ends together! This was a key thing I did not know! So I can create just the right size and it should be perfect! I can also double these up by melting two belts layer by laer for a 1.8mm thick square shaped belt that is even less stretchy and so can be even more able to tightly grip my pulleys. I'm very excited about this and think it will take us to where we need to be *crossing fingers*.

I've had an epiphany. So in the winch in place pulley system I was working on before, my concern was that when winching in the string things would be taught and reliable but when the motor reverses and releases string, that is when any snags in the system could cause the string to not be taken up rigidly and tension on the system is then lost and the motor is then unspooling string which isn't being taken up which will result in a spaghetti mess of string spraying everywhere out of control and getting all tangled up. The solution I had was a constant tension spring attached to the turn in place pulley output that would ensure that always keeps the string in tension as the motor unwinds. However, that was a extra cost and complexity and volume taken up by yet another thing and when you multiply that out by 300+ motors that's a LOT of springs added taking up a ton of extra space. That is why I moved to a belt based system instead of string and winch based for the first pulley. So the epiphany was this: it hit me that I can simply have the spring that does the extension of the final finger joint be what puts tension on the whole system and then if at any point in the system a snag were to happen, rather than tension being lost as the motor blindly unravels, not detecting the snag, I could have the motor NOT actively unwind anything at any point! So the motor, when unwinding is to occur, will simply turn OFF, rather than actively drive the unwinding electronically. It can pulse width turn off just acting as a brake to moderate speed of extension but at no point do any counter clockwise release or unwinding of the string. This way, the system only itself pulls string off the motor output shaft and if the system at any point snags, the extension stops and the string is all still under moderate tension but just no further advancement takes place and the motor does nothing further but blindly turning on and off but not actually spraying out thread everywhere at all. Eventually, the potentiometer measuring the joint angle of the finger joint would detect things are not moving and the system would KNOW it has a snag somewhere and at that point it would perhaps try to contract then attempt extension again hoping to dislodge the snag. If this did not work, the system would go into a troubleshooting routine like notifying the user (myself) to fix it or fixing it itself or w/e. But no damage would occur in this setup involving a unraveling mess or tangled mess. Simply the snag itself would be discovered and addressed but no catastrophic series of failures would result in theory under this new setup. So with all of that said, and this solution in place, I am ready to return to the turn in place style winch style first pulley setup I had before and then the Archimedes pulley will do the rest. So the first pulley will be 2:1 downgearing and the Archimedes system will do 16:1 for a total of 32:1 downgearing. No constant tension spring needed anymore! Much simpler now. Everything I was concerned about is then solved now. The belt based system fix ideas I was going for may have worked but as of right now I'm abandoning that course. I prefer the winch style and think belts would be higher maintenance and slippage would perhaps be an issue even with all the changes I had mentioned to improve on it. The fact is, belts only have so much surface area to grip onto so they don't scale down too well to tiny pulleys IMO. Large pulleys are better due to large surface area and more for the belt to grip. So my super miniature belt idea was a bit doomed from the start even if it could have worked (and it may well have worked) it just isn't ideal theoretically and I'd rather go with something I trust more intuitively for now.

>>35302 So glad to see you embracing the 'simplicity first' motif, Artbyrobot. I pray you have good success with your new, control-driven approach to this particular problem subset. Looking forward to your soon good news/pics! Cheers. :^) BTW Merry Christmas, Anon!

Here's my latest progress on the winch in place pulley setup. I opted for 10lb test 0.12mm diameter PE fishing line (orange color) as the output that will interface into the first pair of downgearing pulleys of my archimedes pulley downgearing system. This turn in place pulley achieves 2.77:1 downgearing ratio now. The motor shaft reels in 32 inches of string that is 6lb test 0.08mm pe fishing line (black) and after the downgearing pulley, the final amount of orange fishing line reeled in is 11.55". That's a much more manageable amount of runout for the archimedes pulley system to deal with to keep it more compact. The archimedes pulley downgearing system will add an additional 16:1 downgearing to this which brings me to a total of 44:1 downgearing. The motor itself pulls at .5lb pulling force so after 44x that increases to 22lb of pulling power. After mechanical disadvantage is factored in, I estimate the finger can curl 5.5lb ideally which is about the same strength as my finger. So that's perfect and VERY strong IMO.

>>35496 Sounds like great news to start the new year off with, Artbyrobot. Thanks for the update! Cheers. :^)

Not the most substantial update but I wanted to share my top cap solution for the winch in place pulley. In this photo, you can see that I cut out a small piece of the clear plastic from strawberry container into a little square and poked a hole in it with sewing needle then pressed it onto the tack firmly till the tack jutted out a bit like 1mm. Then I glued the tack to the top cap with 401 glue. This keeps the pulley from coming off the winch when the motor is upside down which it is now. Another small update is I just ordered some plastisol to experiment with for robot skin making or even other parts of the robot like the artificial lungs or even ligaments perhaps. I ordered the hard and the soft versions which you can mix together to get medium variants. This is the stuff used to make fishing lures but the harder formulations make pvc medical skeletons. It is a thermal plastic so its like TPU but unlike TPU, not so fussy since you can microwave it for 3 minutes and use it - much easier and lower fumes. You can reuse it too by just microwaving it again. So that's a improvement over silicone. The worm fishing lures are quite durable. It comes in clear and you add pigment. I plan to add acrylic paint and may switch to dies or lacquer paints to see what works. I think using this as skin is being slept on. It seems like it could have huge potential. You can shoot it into a mold or apply it over a 3d model by spray or brush or knife application methods. Then peel off and use. I love that it can cure instantly in theory if you spray the hot surface of it with upside down compressed duster can - this is how I get hot glue to insta cure. A instant cure is amazing for fast results. I like super glue/401 glue because it insta cures with accelerator spray. Anything with no wait time for curing speeds up workflow and enables me to move quicker in getting steps done. This would make it superior to silicone due to no wait times. A power mesh backing fabric will give it the rip resistance it needs just like silicone mask makers use.

>>35682 Nice clever little hack, Artbyrobot. GG. >plastisol discussion Thanks! You might also check out the discussion in our general Robo Skin thread on this : ( >>35259, ...) . Keep up the good work, Anon.

I had a eureka moment recently that I wanted to share. So basically I was thinking that I may not need to read back emf from a BLDC motor in my custom motor controller. Instead, I can have it just mindlessly advance the motor at a fairly low power mode by default and a default speed of advancement of the rotating electromagnetic field. Without feedback, it may overshoot, rotating faster than the output shaft and thereby skipping some turns. That is the reason why people want to read the back emf to avoid that issue and instead only advance the electromagnetic field forward at just the right moment - the zero point crossing moment. But I was thinking about it and realized that is not really necessary. For this application, if skips start happening, it doesn't really matter. To the degree that skips are happening, the motor will stop advancing the load with its winch system and this will show up when readings are taken by the potentiometer measuring the final joint angle. If alot of skips were taking place, the advancement of the potentiometer would not match the angle it thought it would be at were no skips involved and this would tell the motor controller that it has been having skips and give it an idea of how many skips as well based on the divergence of projected joint angle by now and actual joint angle by now. So then it would turn down the speed a bit or turn up the amount of on time of its pwm and thereby put more force into the rotating magnetic field to give a bit more oomph to the motor. It would then track progress by way of the potentiometer again and see if that solved it. If it still is skipping a fair amount that could indicate the load is more than expected or there is a jam in the system or it just needs more power and it could turn up the power more and slow the speed down more on its rotating magnetic field overall speed and try again. Rinse and repeat until it finds the sweet spot or finds out it simply cannot lift the load because its too heavy or there's a jam in the pulleys or w/e. So in a way then this would give it collision detection as well as the ability to have an idea of how heavy loads are based on how much it had to slow down and add forces to get the joint to move. I then see no real need to implement ANY back emf reading NOR any need for hall effect sensors etc to monitor rotation progress. The potentiometer on the final joint the motor is actuating is enough clues to tweak the rotating magnetic field to our satisfaction. By eliminating the back emf circuitry we greatly simplify the schematic of the motor controller, suffer negligible performance hit, and eliminate a lot of processing for the microcontroller chip handling the logic of many bldc motors simultaneously which means it can handle more bldc motors by itself. It doesn't get bogged down so much by having to read in all the zero point crossings as part of its routine. This saves on processing demands and processing speed demands. Getting this all to work in real time and perfecting it will require a fair bit of trial and error but this is how I'm seeing it working out and my proposed solution for simplifying things. I think it should work great! I'm excited to have much more dumbed down circuitry like this and to get to working on this soon. Just have to finish making my pulleys and then this electronics development can get underway again. That's why I've been thinking ahead about it a fair bit since it seems I'm likely nearing the end of solving the pulleys situation soon.

>>35946 >I'm excited to have much more dumbed down circuitry like this and to get to working on this soon. >That's why I've been thinking ahead about it a fair bit since it seems I'm likely nearing the end of solving the pulleys situation soon. This sounds exciting, Artbyrobot. I hope you can prove your thesis about the simplified control approach soon. As Kiwi and others here have mentioned (in effect): The most reliable actuator is the one that isn't there! Cheers, Anon. :^) >=== -sp, minor edit