>>24984 Here's a quick paper on the subject, with picrel as an excerpt [doi: 10.1016/j.epsr.2017.08.003] Guess the whole push for green energy can be useful after all lmao You probably know more about this than me, but I've heard that certain types of piston pumps use a series of chambers with different compression cycles, trying to flatten the impulse as much as possible-- sounds like that's what your tractor has? btw, topic unrelated, but I might need to pick your brain on keyshafts+key installation down the road-- my coworkers are great for engineering stuff, but we're kinda spoiled when it comes to equipment and doing stuff the "right" (expensive) way, since it's on company dime. I'm guessing you've installed em before? >>24986 Not sure how practical that is tbh-- at least for hydraulics, it's a non-starter, since we're talking less than 0.5% volume changes per 1000psi. Pneumatics is a bit more doable, but without a massive tank, I just don't think we'll be able to store sufficient volume, passively, unless we do something crazy like putting it through a state change and storing it as a liquid. ... Actually, that could be worth looking into. Not gasses that need cryogenic temperatures, mind you, but if we could find a liquid that phase changes near enough room temperature, that ~1:1000 expansion ratio is looking sexy as hell. Anyway, a rule of thumb for hydraulics is that the system's pressure is effectively the pressure exerted by the system's load, You can get away with stuff like a buffer (think reverse retard chamber to "store" force), but that usually kills efficiency unless you have some very fancy valves that disengage the buffer unless the system is drawing from it, or idle (and thus "charging" it)

>>24990 >You probably know more about this than me Apparently not because that chart surprised me. Why is a screw type pump so low in efficiency? I don't know. It's not that way for air. You would think a steady flow of a screw type pump would be far more efficient than a pulsating piston. Even regular gear pumps they say are better. I wonder. I can't find that paper from that number. There's mass of links. Whats the actual name of the paper? The reason I said use peristaltic pumps is while they don't have the best of anything they are fairly quite and when you stop them they hold pressure. They do pulse but with more rollers this becomes less and you will need some sort of air spring to had a reservoir for pressure. I think they would be cheap and good enough. But maybe not. >keyshafts+key installation...I'm guessing you've installed em before? Yes but I don't design them just use what came with it. If I remember correctly, and I may not, electric motors generally have straight shafts and pump type stuff has beveled shafts to press it on tight. >we're talking less than 0.5% volume changes per 1000psi Ehhhh...I don't necessary follow that but I'm surprised about the pump efficiency also. The storage is only to get the pump started. Instantaneous. It may well be that if you are right we will have to go all electric. My ideas about hydraulics has to do with low cost manufacturing. Not any love for hydraulics. In fact I hate them and have said so earlier. I rebuilt the pump on my backhoe/tractor, that wasn't the problem. Turns out there's a little reed valve spring type thing in the power steering column that when you twist the steering wheel inside the steering column this little spring loaded valve would let more fluid into the power steering. A seal in that drained my pressure. You have no idea how long it took to figure that out. I hate hydraulics but...if that makes it cheaper then, hydraulics it is. Look up this article. You don't need as high a pressure as you think. "Fluid-driven origami-inspired artificial muscles" A good way to visualize this is an accordion or a scissors jack. Low pressure, large area.

Another interesting pump that can also be used as a motor. https://en.wikipedia.org/wiki/Progressing_cavity_pump

>>24990 It's important to note that I wouldn't claim that it makes sense to use that for everything. I just want to keep it on the table for at least smaller movements or as additional actuators. Keep in mind: I want to build a gynoid with a soft body. Should I fill the soft parts with some filler, or rather use it for some soft muscle?

Mirroring>>25099

>>25114 Expanded I want to use wipers or similar dc motors with gearboxes over servos due to them being powerfull, having 90 degree gearbox (tho large gearboxes should be avoided doe to mass added) which allows for better space management & power transmition (belts/steel cables/chains) where large and blocky steppers/normal servos that lead to compromises of power over fembot form. I was looking up how other people make custom servos outta salvaged motors and they either rip control boards from cheap/broken servos or equip fairly inexpensive assemblies with crazy expensive encoders and drivers. Have any one of you build your own custom piece that can be hooked up to SBC?

>>25179 cont. Basically, if i get it right, it should be as easy as hooking encoder (soemthing dirt cheap as 10k linear potenciometr) to analog input on SBC, from there send PWM signal to driver that can control speed and direction )again something dirt cheap as L298N). Connect it to your DC, afix encoder, test & set movement range and it's done. Anything major imma missing?

>>25040 https://doi.org/10.1016/j.epsr.2017.08.003 "Direct driven hydraulic drive for new powertrain topologies for non-road mobile machinery" To be clear, I'm not an expert on hydraulics (far from it, in fact-- haven't seen em since college), so a lot of the questions you're asking I'd have to research in order to answer. Plus, I'm pretty sure the "why is it inefficient?" question would be worth a published paper or fifty.... If I were to "shoot from the hip" to answer (which means I'm 99% wrong), I'd say the different efficiency cases comes down to the properties of the fluid (or gas) that you're moving, especially viscosity and compressibility-- imagine trying to pump honey with a "propeller", vs. a screw pump (which I imagine would work quite well) Intuitively (so now I'm 99.9% wrong), if we think of a piston pump, the only real "wasted motion" is retracting the piston and refilling the void it's about to pump. Valves would cut the piston of from the system any time it's not contributing energy, and thermal losses from momentary compression aren't a big issue for stuff with such low compressibility. That's just my 2c tho, and it's worth noting that the paper I referenced is specifically for small-scale, direct-driven pumps with commercial hydraulic fluid. > (re: driveshafts) Thanks, man. I’ll need to come up with a mechanism that allows a keyed gear to slide along the keyshaft’s axis, while not allowing rotation. Thankfully, a bit of slop (backlash) is tolerable, but if you have any ideas to minimize it, let me know. (rel >>24744) > (re: hydraulic volume change under pressure) I think we had a bit of a miscommunication there, I was referring to NoidoDev's idea of a passive, compressed storage system for active operation. The compressed-gas hydraulic bladders you mentioned will work, of course, but in that case, it's not the water "storing" that pressure, just transmitting it. Bottom line with "incompressible" stuff is you'll never get more volume out of it than the tank displaced in the first case, no matter how much pressure the tank has (both by-definition and purely theoretical, I know) As I understand it, the easiest way to understand how much energy there is "in" a compressed system is to think of the ratio between compressed and uncompressed densities. (multiplied by the force exerted at each particular pressure, of course) For example, let's take two pistons exerting (the equivalent of) 1000lbs on a 1in plunger (say 1000psi inside), one full of compressed water, the other with compressed air, and say they're each at "100% volume" (not yet extended). Now, as they extend, the volume the compressed medium fills will increase, so the pressure exerted by the piston will decrease. Once the piston full of compressed air extends to 101,103, 105...% volume, the force it exerts (and internal pressure) will have decreased a little, but there's still plenty of Work (physics-def.) it can do. The piston full of water, on the other hand, no longer exerts any force once it reaches 100.2% volume (since water's compressibility is ~0.2% per 1000 psi), and the internal pressure (ignore gravity for a bit) is now ambient, so "zero". In this example, the density ratio of water was 1.02 @ 1000psi, but air has a density ratio over 69.1 at the same pressure (see https://www.engineeringtoolbox.com/air-temperature-pressure-density-d_771.html -- I was incorrect with the 5% factor, that was the compression ratio at the bottom of the ocean lol >>24990 ) (Formal explanation of it: https://www.sciencedirect.com/topics/earth-and-planetary-sciences/compressibility)

>>24882 Sorry man, I missed this first read-through. Staggered mounting holes/"Staggered Connections" are intended to maximize the Fracture Path length (or, for the forces we're working with, it's more "deformation length", especially with materials like thin aluminum) while minimizing Sheer Lag. I know, that means jack shit unless you're already an ME (and I'm not), and I'll spare you the textbook copypasta, so have a couple diagrams that do a pretty good job explaining it intuitively. Basically, maximize the amount of material that has to be sheered/displaced for your mount ("connection") to fail (Fracture Length), and minimize the amount of material that isn't bearing any force (Sheer Lag). >>25190 That link shouldn't end with a ")", oops. real link is: https://www.sciencedirect.com/topics/earth-and-planetary-sciences/compressibility)

>>24990 Thanks for the paper. So I look at this thing and I admit I'm fairly suspicious about this efficiency chart that shows screw pumps as next to useless. So I'm looking at all sorts of web pages on pump efficiency and a lot of them talk about "volumetric efficiency" as being a key performance figure. Look at the chart again and you see one side is efficiency and the other is "change in pressure". Now where that chart came from according to the paper is H. Kauranne, J. Kajaste, M. Vilenius, Hydraulitekniikan perusteet. [Fundamentals in Hydraulic Technology], WSOY, Helsinki, 2006 (in Finnish) now I can't read Finnish so...I'm going to have to guess. Screw pumps DO NOT have a high pressure rise like other pumps. They explicitly talk about staging them to get higher pressure. So I think this chart may be right but it's not measuring what I care about which is mostly actual efficiency as measured by power out based on power in. I think that chart in terms of efficiency is just how much pressure you can get from that type pump in a stage. Not saying it doesn't exist but it's hard to find a graph of total pump efficiency for all different types of pumps on one graph. I suspect it's because all these pumps have different uses and pressures so they feel that it's not correct to show them all under one condition. Now for what I see the paper saying. They are saying to get rid of valves, and yes normal hydraulic valves are totally expensive pieces of shit. They say drive a pump electrically and, I would have to guess, use a electric motor driving each hydraulic pump for each cylinder. For a big machine I expect you might save money like this. Traditional hydraulic valves are last time I checked about $100 USD per valve and have to be precision machined to high tolerances to keep all the fluid from leaking out. In fact mine right now are wore out. But on a waifu...I think this would be a lot of trouble. On second thought...maybe not. Let's say you have a bunch of printed gear type pumps run by switched reluctance motors AND you make a huge system of blood vessel type connections to all the muscles. So you start the motor and it pumps up the muscle.Maybe that would work. So I started out thinking this was horrible but, maybe it would work. Have to think about it. It's also possible some combination of direct pumps going to large muscles, but using one pump for many actuators with valves could be done for stuff like fingers and smaller muscles. Now because it's not really clear and we should think about these things. IF you are driving an electric motor for most every muscle, and you drive a pump for most every muscle, then wouldn't it be more efficient and cheaper just to drive the damn muscle with all electricity in the first place? I mean you now have all this wasted power going through pumps. (read the paper on all the losses you quoted) The only advantage I can see is maybe you could have a pressure accumulator, basically a solid tank, with bladder that has gas on one side and fluid to be used on the other. The gas is just a spring to accumulate power. For myself the only reason I would consider hydraulics is if I could make some sort of accumulator and could come up with a cheap valve. I know a pump can be made cheaply and be run by one or a few motors. Having large castible bladders for all the power systems where fluid runs through castible pipes and bladders could save a lot of time and money compared to building a lot of electric motors for each actuator. PS after looking around I do not think the graph above is the actual total efficiency of a screw pump. Screw pumps they say are very efficient and that they do not have the turbulence problems (turbulence causes inefficiencies) of other pumps. https://www.linquip.com/blog/parts-of-screw-pump/#Advantages_and_Disadvantages_of_Screw_Pumps

>>25190 >Bottom line with "incompressible" stuff This is probably of little use but...it's not true that fluids are ncompressable. Mostly, but not all. There's a guy who invented all kinds of stuff based on this and has a lot of damn near incomprehensible books and papers on this. Very interesting fellow though. https://en.wikipedia.org/wiki/George_Constantinescu http://www.rexresearch.com/constantinesco2/constantinesco.htm

>>25184 This link here on fiber optic sensors for encoders is likely one of the cheapest and most brilliant ideas ever. >>22032

A repeat from prototypes that belongs here. Low cost printable gear train for motors. I talked about George CONSTANTINESCO. The guy has one of the most brilliant transmissions ever invented and it would be very suitable for 3D printing. Here's two links on it. http://www.rexresearch.com/constantinesco2/constantinesco.htm http://www.rexresearch.com/constran/1constran.htm It's difficult to describe. It uses two long levers. Basically in parallel. They are mounted on sprags. A sprag is gears that allow you to pedal a bicycle then coast. Hear the ticking when you coast. That's the sprags rotating. When you pedal they lock up and force the wheel to move. So imagine two long bars that are mounted on a wheel like the petals and main gear on a bicycle. The size of the gear and in this case where the bar is grabbed determines the stroke of the bar. So if you want high power the drive bar is gripped low and the driven bar higher. So the drive bar moves a small distance pushing the driven bar forward but only a little. When it goes backwards the sprag lets it coast. So it drives a small amount on the long post output. Meaning lots of power. If the driven gear is farther up it will drive the output driven post/gear very far for each rotation, so higher speed output. It's really ingenious. The guy was a major genius. Since the force is over a broad area, it's just like a combustion engine crank and piston rod, you can have a sturdy system with light parts. And best of all it's continuously variable. So if the waifu wants to move fast, but with low force, then it can be adjusted so. If lots of force needed it can also do this but at a lower speed. Here's a random 3D printed sprag video. https://www.youtube.com/watch?v=UIhCPl8eb7s random link to files. I have no financial interest in this it's just a link for show. https://www.makersmuse.com/roller-clutch

>>25197 Looks promising, especially part where you use single camera to replace all your encoders, but for now it is out of scope of my project. I'd rather use some magnetic encoder that tells movement & position and gives me output i can use in normalcircuitry. Some thing like AS5600.

Under the category of brushless DC motors, what seems to have been a completely overlooked source of great robot parts: !!!HOVERBOARDS!!! My searches didn't turn up a single mention of them on this board. It's not just anons here, even the Masiro Project could have saved a lot of money if they built their robot's bases using old hoverboards. They were built to carry adults so they are way overbuilt for what they and we want to do. Each board comes with 2 hub motors, 2 gyros, the motor control motherboard and a battery. The motherboard can easily be hacked to flash it with new firmware. The motors can also be run by a hobby esc. Use controllers for cars that have the same speed in reverse as forward, and a braking function and you guys who like tachicomas are halfway home. So if you are like me and planning to run my waifu around on a base until she can walk you could do a lot worse than to investigate the use of hoverboards. Here are some links to a few of the hundreds of videos about hacking hoverboards for many uses including robots, and a couple of threads from the Synthiam site. (Disassembling) what's inside Hoverboard https://www.youtube.com/watch?v=xnCp-DJUCt8&t=15s Hoverboard parts explained for robotics use https://www.youtube.com/watch?v=-VIRlurVht4&t=63s Hoverboard Robotics Tutorial Part 1: Hardware Overview and Hacking https://www.youtube.com/watch?v=bIHjRTG7ilU hoverboard driver hack https://www.youtube.com/watch?v=IL4xcSQ6_rU Driving hoverboard wheel-motor with RC model ESC https://www.youtube.com/watch?v=LJzoy2TJXFk RoboDog Part 3 | Using Hoverboard Motors for RoboDog https://www.youtube.com/watch?v=_VUtfK4bCl8 https://synthiam.com/Community/Robots/Untitled-Hoverboard-Project-17760/comments https://synthiam.com/Community/Questions/Hoverboard-control-18833

>25783 Crap, I forgot the picrel.

>>25783 Interesting, but they guy disassembling it seems to use it for making a regular robodog, not a humanoid on a hoverboard. Also, recycling old devices isn't something that can be shared easily, and I don't have a "hooverboard" (which is a misleading name anyways).

>>25790 >Interesting, but they guy disassembling it seems to use it for making a regular robodog, not a humanoid on a hoverboard I included that one for the anons who are interested in ponies or 4-legged monster girls.

>>25783 Good resources, though huge, they make excellent drive motors as they provide tremendous torque. 36 to 48 volt systems are recommended to ensure a highly responsivr motor.These motors come in many sizes but, usually are around 6.5 inches with 16kV. For hacking, you want to use old hoverboards. I have a new hoverboard which uses a cheap Chinese chip that no one has figured out how to hack yet. >>25790 Please try to open your mind. Information from a tutorial can have benefits outside of explicitly replicating their work. In this case, the tutorial provides beneficial information on the general characteristics of hoverboard motors and controlling them. >>25791 >Quadraped monsta grills Only as the end drive motors.(picrel) These motors are not built to maintain high holding forces. Using them as the base for servos will create a very hot system. You'd need to implement a gearbox which would end up with a gigantic and heavy servo.

>>25792 > a cheap Chinese chip that no one has figured out how to hack yet That's good to know, I'll have to check my boards to see if any are the same. While it would be best to be able to use the controller that they came with, in the worst case they can still be used with RC gear. I hope mine are all good, all of my ESCs are for aircraft- one direction and no brakes.

These seem promising (if not a scam): https://www.alibaba.com/product-detail/Special-price-Limited-Quantity-New-RMD_1600938534322.html I took a chance on these cheap motors so you don't have to. Normal price for about the same motor is 200+$. They'll arrive in the mail by the end of the month, and they can be used for a limb actuator.

>>25910 Thanks Anon! :^)

>>25923 Yw, expect me to post a guide if I figure out how to make them work or dissapointment otherwise. They got held up in shipping because the US needed an importer information form.

>>25910 >>25956 8 motors came in, they all turn so at least it's not a complete scam? I'll test them whenever.

>>26063 Woot woot! Thanks for the good clear shots Anon. Any chance you could give us a side profile pic too?

>>26064 canbus v2 arduino hat on the left, motor is as large as a coffee cup. >=== -minor edit

>>26081 Great scale information Anon. Looking forward to seeing what all you accomplish with them! Cheers. :^)

>>26081 this one works as it is supposed to with the debugging tool on the website: >https://files.catbox.moe/8piz07.mp4 does this tickle the fancy for any of you robot enjoyers?

>>26107 This video is kinda strange. What's going on there? The camera moves away...

>>26113 I tried recording a 10 rpm test but flinched because the motor started sliding on the desk. Stuff like this is dangerous and motors have fallen and broken before when I didn't secure them.

>>26115 Okay, now it's clear, and also a good reminder to be more careful.

3/8 motors are making a clacking noise every couple of revolutions when they go very fast, but it's more or less quiet, so probably fine for my purposes. One of the motors is a bit more clicky than the others. As long as they all move the robot it should be fine? >https://files.catbox.moe/7qze8r.mp4

>>26118 yeah balancing the rotor is ultra high precision stuff the smallest difference of weight on one side will make it vibrate, its fine if you havent attached it to anything when it has to actually work against something its not going to be able to go that fast

>>24328 >Isotropic Meshing Gear https://www.youtu.be/AZQcHOJwhKU

>>12810 Where can you buy a actuators for robowaifu movement?

>>26124 You mean bldc motors, servos in general or specialized robot servos? There are websites for this, I'm just buying cheap electric motors on AliExpress.

>>26131 >https://www.alibaba.com/product-detail/Special-price-Limited-Quantity-New-RMD_1600938534322.html 6/8 of these aren't bad and they were only 100$

>>26123 Excellent, thanks Anon. I see a bright future for these as Elbow/Knee joints.

>>26135 >6/8 of these aren't bad What do you mean? Two of eight of those you bought had issues?

>>26155 Yeah like 3/8. I'm pretty sure it's a scam but it's still cheaper than buying normal price 200/300$ motors so I'm still making the correct move on these. Also they're kind of being nebulous on if they want me to return the bad ones or not.

> How Does a Fluid Coupler Work? I 3D Printed one that Uses Vegetable Oil! https://www.youtu.be/wGw9sXhYEc8 >Today, I bring you my 3D printed fluid coupler. Out of curiosity, I wanted to know if I could 3D print a working fluid coupler that works on the same principals as one you would find in a car. The fluid coupler uses vegetable oil as its fluid much like how a transmission uses transmission fluid. I explain how a fluid coupler works in case you are curious yourself. https://drive.google.com/drive/folders/1KF00u7qUKaTI0XaQ2U0TaewtBtsG-btX?usp=sharing Not sure if it's going to be useful and the current design made in plastic will have heat issues after a while. >ChatGPT: Fluid couplers and gears serve different functions and typically cannot directly replace one another in most mechanical systems. Gears are mechanical devices that transmit power by meshing with one another, transferring rotational motion and torque between shafts. They provide a fixed speed ratio between the input and output shafts. On the other hand, a fluid coupling is a type of hydrodynamic device used to transmit rotational power from one shaft to another. It works by using hydraulic fluid to transfer torque. A fluid coupling doesn't offer the same precise speed control or fixed speed ratios that gears provide. In some applications, a fluid coupling might be used in conjunction with gears in a transmission system, particularly in situations where you need a smoother start or if you want to limit shock loads when starting or stopping machinery. However, in terms of directly replacing a gear with a fluid coupling or vice versa, it's not a straightforward swap as their functionalities and modes of operation are fundamentally different.

>>26280 It seems to me that we'd benefit if we could actually use fluid coupling because of the good resillience/wear dynamics. The problem is that the high rotational speeds needed to get good high-viscoscity transcoupling effects is prohibitive for our needs, I think.

Interesting actuators breakdown analysis video : https://www.youtube.com/watch?v=5MNz0YyqgLY of the Teslabot actuators promotional video : https://www.youtube.com/watch?v=1xChD-gv_pc

>>26780 Thanks, this might be very useful. Maybe rather long-term but nevertheless. These actuators look like one's without neodymium magnets, which could be interesting to be independent from that kind of supply. Unrelated Cute: https://www.youtube.com/shorts/HSDNFXXOThE

>>26782 >These actuators look like one's without neodymium magnets, which could be interesting to be independent from that kind of supply. Yeah, I've been thinking about that exact issue for a while now NoidoDev. Obviously China intends to restrict their hard-won environmentally so so-called 'Rare' Earth metals. It would behoove all robowaifuists to find/devise systems that are much less -dependent on them. >Unrelated Cute: https://www.youtube.com/shorts/HSDNFXXOThE Daww! I see the cousins are still visiting. I wonder if they have something special planned for Christmas & New Year? :D

Differential Swerve Drive for rolling platforms, it uses both motors for driving forward so it is more efficient: https://youtu.be/8RQmpUEgoYU Might be useful for a Gardevoir suit, waifu car or a waifu with wheels. Swerve drive means it can drive sideways, which is more similar to a bipedal creature that can move out of the way easily.

>>26857 >Might be useful for a Gardevoir suit, waifu car or a waifu with wheels. Very cool! I'm actually in the middle of a smol robotic cart->Tachikoma design for Sumomo-chan. This is very timely for me Anon, thanks! :^)

>>26118 >Cheap motor update: I cannot figure out how to use the CAN bus with the arduino can hat v2 and a program to move the motor with a joystick. I'm feeling extremely lazy so I think I need to cut all unnecessary idle tasks and try again.

OP, seems it's time for a new thread please These are some good ones, Anon. Thanks! :^)

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