Hey everyone! I hope you enjoyed this deep dive into the design process of the high-performance linear actuators for my juggling robot. I'd love to hear your thoughts on the design! What improvements would you suggest? Have you ever built or used linear actuators in your own projects? Share your experiences and tips in the comments below! 😃🤖🔧

@IncendiaryMedia

Жыл бұрын

this is slick! have you considered routing the cables through the actuator arm itself?

@paint4pain

Жыл бұрын

As others have mentioned, one or two PTFE or Rulon J linear sleeve bearings would be lighter and probably stiffer than 6 6001RS steel bearings. You could also swap to acetal plastic ball bearings instead of steel to lighten them up and reduce wear. Other than that you could replace the push and pull strings with a single string and have a tensionning spring at one end to remove backlash. You could also have the pulleys be tensioned against each other to acheve the same result but that sounds clunkier.

@Alrion1704

Жыл бұрын

14:20 use a ceramic eye from a fishing rode for strung position 😉

@MartinDxt

Жыл бұрын

u can use the bike/bicycle brake tubes those are quite tough instead of the ptfe

@BlackHeartScyther

Жыл бұрын

I would put bearings on the 3 rods, back end of the extending arm, just for a bit more stabilization.

For the string you might also look into braided uhmw, commonly used for high performance kites. It is not degraded by UV (if your robot has to perform outdoors) doesn't absorb water, and has far better abrasion resistance and has less friction than kevlar, also has nearly zero stretch for low backlash. Pretty cheap too. Excellent vid. Thanks for posting!

@cgln8760

11 ай бұрын

I was thinking the same but with Braided monofilament as used in fishing, for the same reasons.

@timotay22

11 ай бұрын

UHMWPE does have problems with creep, though. So you'd want to be sure that it's not stored under tension when not in use. Otherwise slack will creep in, and you'd need to re-tighten everything before you restart

@genixia

Ай бұрын

Use SK99 for the lowest stretch and creep.

You could probably fit the ptfe tubes inside the brake cable housing for a bicycle. Alternatively, you could design an print a modular reinforcement part that surrounds the tube and can carry the compressive load. This is a great design, very cool project!

@harrisonlow

Жыл бұрын

Thanks for the kind words! Re. PTFE ideas: a big consideration for these actuators in this project is that they need to be able to move around fairly freely, and I'm worried that bike brake sheaths would be too stiff, and I can't visualise how a printed support structure would be both flexible (in bending) and stiff (in compression). I would love to know if you have any suggestions on that front! FWIW, a few people have suggested trying brake cables and I'll be testing that (and a few other) ideas soon. I'm sure we can eventually find the perfect tube! (or completely get rid of them, as Eric McGraw suggested in another comment. So many options!)

@NUeB_net

Жыл бұрын

@@harrisonlow Maybe Jagwire Elite Link can do the job.

@James02876

Жыл бұрын

I was thinking about this while falling asleep last night, and I realized that simple beads-on-a-string will provide resistance against compression, but still allow flexibility while not under compression. Anything that allows the tube to freely pass through it, with a rounded edge to allow flexibility, would probably work. However, if it needs to remain flexible _while under compression_ it may be more of a challenge.

@NUeB_net

Жыл бұрын

@@James02876 "beads-on-a-string" is basically the idea behind Elite Link and similar products. They allow smaller radius than conventional bowden tubes and at least one of such (of which I just can not remember the name) claims to be flexible under load… so further investigation may be worth it. I never used such myself because on all of my vehicles, classic bowden works just fine.

@feiter

Жыл бұрын

Of you go down the bicycle cable option. Try with gear cable and gear cable housing rather than brake cable (thinner diameter cable and come with far more housing and connector options)

Nice project! One little trick for getting strings (and wires) through tubes is to use a hoover to simply suck the string through! Works incredibly well ime 🙂

@SeanLavery

Жыл бұрын

Damn, that's a good trick

@chrisBruner

11 ай бұрын

You can also use pressurized air and it will blow it right though. My wife has an embroidery machine and that's how she loads the threads.

Really nice. I wonder if it would be possible to route the Bowden string directly inside two of the carbon rod... This would make it looks like it's moving magically.

@nemesis1588

11 ай бұрын

If two of the bearings that holds the shaft straight had a channel in it to guide the string this could be done easily.

@Anonymous-ex3wq

11 ай бұрын

exactly what i was thinking

@GnuReligion

11 ай бұрын

@@nemesis1588 Maybe turn the whole system inside out, where the actuator is a large tube on the outside, and the bearings are on the inside mounted on a smaller rod. Hide everything. Meh ... may make it too heavy.

Seeing that new design in action made me realize that this would also work well for a different kind of machine...

Lots of great comments and ideas on this project here in the comments. So impressed by the ingenuity of this design. Can’t wait to see future versions of this as you keep developing this.

@harrisonlow

Жыл бұрын

I agree! My notepad is rapidly filling up with suggestions. So good!

Wow this project presentation was EXCELENT! Besides the design being impressive, the presentation was beyond what you can expect from the average engineering video. It was very easy to follow, well paced, and most crucially it covered all* your design constraints which produced the end design. That piece of context is so incredibly important to make the listener understand. It demonstrated a deep understanding of the issue, it's multiple solutions, and that your design really *is* near the ideal design for your particular use case. I felt like I actually understood the design, I didn't just observe it. That level of maturity in design presentation just blew me away. Personally I think you outdid "Stuff Made Here", which in my eyes is the gold standard of engineering videos on youtube. Although the comparison is nto entirely fair to "Stuff Made Here", as he obviously targets a more casual viewer.

@harrisonlow

Жыл бұрын

Wow! Thanks for the great feedback!

This is absolutely brilliant work. I came up with a similar mechanism for my vacuum former. I needed to plunge the part piston rapidly to create a sort of surrounding bubble of soft plastic, before activating the vacuum. I'm surprised there aren't commercial products using this technique. Keep up the good work, I love your projects!

@harrisonlow

Жыл бұрын

Cheers for the kind words! I agree that it's remarkable that this mechanism doesn't seem to exist on the internet anywhere else (at least not that I could find). Hopefully anyone else in the future who needs to build themselves a speedy actuator can now save themselves the ~1.5 yrs of development that I had to go through to get these working!

Wow man, it's so rare to find a channel this small with your level of production, presentation and co tent quality. Really amazing stuff. Seriously, not many channels with 4k subs who as articulatly and succinctly get complex stuff across like you. Keep going and you won't be small much longer. :):)

@harrisonlow

Жыл бұрын

Cheers!

Great concept! An easy fix for the string getting pinched would be a small screw eyelet. Have you considered using Bowden cables? That would likely need you to change from spools to cams to drive it though.

Really nice job inventing such a fast-moving linear actuator system! I learned a lot of cool techniques, especially your ingenious way to handle the critical alignment requirements of the 3D-printed end parts with the custom spacers!

Harrison, great job! Suggestion; instead of using the PTFE tubes for cable guides, why not incorporate the cables into the carbon fiber structure tubes?

@Traqr

Жыл бұрын

You'd still want cable guides (shifter cable housing seems like the best bet) into the bottom block but yes, using the structural tubing as part of the string guide is a great idea.

@harrisonlow

Жыл бұрын

Cheers! Routing the strings through the CF tubes would probably work well for many applications, but I'm using these actuators (there will be 6 of them) to power a Stewart Platform and they need to move around quite a bit. Having the strings routed through the PTFE tubes means that the strings don't get in the way of the actuator moving around

@sandorkonya

Жыл бұрын

@@harrisonlow i had the same idea, why not routing the strings through the CF tubes. I don't exactly undestand why would the strings get in way of the actuator?

Bicycle shifter cable and housing is super cheap and cand stand up to A LOT of tension. You could even include a barrel adjust in the system and easily adjust the tension of the cable on the fly.

For the string running between the bearing and the slide, I would suggest 'v-groove' bearings, which as the name implies, have a groove along the face of the bearing. Maybe someone already suggested it, but just my 2 cents (or pence) :)

This was very enjoyable, I really liked seeing the evolution of your designs, thanks for sharing.

Consider mounting one bearing of each triplet on a small flexure preload spring. That way you don't need to adjust each guide. Stiffness up-to the preload will be determined by the remaining four fixed bearings. :)

@harrisonlow

Жыл бұрын

Interesting idea! I think this might have the same issue as what Charlie Wynn was suggesting in another comment - the central tube should be perfectly centred in the actuator for what I'm using it for. Precision will be very important for Jugglebot and I want to try and keep everything as concentric as possible. Thankfully the spacers/guides are really easy to swap out and once you find a size that works, there's no need to change them again

@MONEYMAN5811

Жыл бұрын

@@harrisonlow if you’re worried about accuracy, I would adjust your attachment points on the rod for your strings. They look like they are at an angle in your video. Combined with the fact you’re only measuring distance on your motor, you’ve introduced potential backlash in the system, AND you’re measuring the change of the hypotenuse of the triangle you create with the string instead of the actual linear, parallel distance. It is probably not a lot at all, but in belt driven systems that need accuracy, the small angle can definitely throw off measurements.

@LimitedWard

Жыл бұрын

​@@harrisonlow as long as the system is stiff enough, can't you compensate for the lack of concentricity through software?

@harrisonlow

Жыл бұрын

@@MONEYMAN5811 Good thinking! Something I didn't explicitly say in this video is that these actuators (there will be 6 of them) are being used to power a Stewart Platform, so the actuators need to move around quite a bit. The PTFE/string attachment points are angled to (hopefully) lessen the degree to which the PTFE inhibits the platform from moving around

@harrisonlow

Жыл бұрын

@@LimitedWard Yeah, probably! Though I want to limit the amount of hard-coding of this sort of physical "defect" that I need to do

Hello, one of the string could go through the center of the other red printed part (the one attached to the base of the printer at the bottom of the 3 small carbon tubes), and go through the big carbon tube to the top. It shoud fix your issue with the string under the bearing, and use a more direct path :)

@harrisonlow

Жыл бұрын

Good thinking! The main reason I haven't done that is that these actuators (there will be 6 of them) will be powering a Stewart Platform, so the actuators need to move around quite a bit, meaning it's tricky to route the string through the central tube since the central tube moves so much. I love the idea though, and it'd certainly make the design a lot cleaner. Cheers!

Now make this into a 3d printer.

@williamchamberlain2263

Жыл бұрын

Keep it as a juggler, but add a blob of PLA on each bounce - print times would be really long, but the time lapses would be insane

@absalomdraconis

Жыл бұрын

Never heard of a 3d printer that needed this kind of speed.

@tinkeringengr

Жыл бұрын

@@absalomdraconis Speed is a game changer for manufacturing 3D printed parts.

@jamesyeoman794

Жыл бұрын

FLSun wants to know your location

@angrydragonslayer

Жыл бұрын

​@@absalomdraconis i'm considering building a VZbot because my SK-GO died after i tried to hit 1.2 m/s (burned the servos and maybe the board) The VZ prints viably at 1.5 and (i might remember wrongly but) he's planning to hit 2 with usable quality.

This video was such a joy to watch. Persistence has paid off. What a clever idea.

@harrisonlow

Жыл бұрын

Thanks for the kind words 😊

Awesome stuff! Your robot is mesmerizing to watch!

This is so interesting! People like you are the future of technology, not big corporations. Thank you for sharing this! Subscribed!

@harrisonlow

Жыл бұрын

Thanks for the support!

Super awesome! Another alternative to the bearings are igus drylin type r bearings. They are a split sleeve that rides very nice on carbon tubes and are reasonably affordable at around 5 dollars. We use them all the time at work for that purpose. If you put a slot and adjusting bolt in the 3d printed part you can set the preload/slop. You could probably even make a 3d printed spring feature to auto set it

Wow, amazing project! Thanks for share it

Heat the CF tubes up to the glass transition temperature of the filament you used (e.g. PETG = ~85°C), then push them in slow and steady. That should make things less violent! ;-) Instead of the 6 axial bearings, maybe look into using just one linear ball bearing (like LM8UU, but with larger inner diameter)? That should save a lot of weight, as you'll only need one. Centering it could be done via 3 bolts then. Use PTFE tubes with a smaller inner diameter and more wall thickness, they should get fairly rigid.

@MONEYMAN5811

Жыл бұрын

I wouldn’t recommend standard bearing or bushings on CF. You could go with a plastic bushing like the IGUS ones though and they seem to work okay, but there’s a bit of friction that needs to be overcome to get them moving. They also have to be preloaded quite heavy for tolerances to be good unless you go for their bushings that are already preloaded with a metal housing, which will add a bit more weight.

@boonjabby

Жыл бұрын

Linear bearing is a top idea, I would recommend a Teflon bushing though as it will work well with CF

@jangrewe

Жыл бұрын

Sure, igus are great, i used them on one of my 3D printers (Prusa, got rid of that damn bed slinger). I didn't notice the friction, though - but maybe that was because they were on steel rods, not CF tubes, and had only a small contact surface at the top. But yeah, anything other than those axial bearings, or: any kind of a linear bearing, would be the perfect application for this - because that's what they're made for! 🥳

@harrisonlow

Жыл бұрын

@@jangrewe Great ideas! Some thoughts: 1) I love the idea of heating up the CF tubes. I wish I saw this comment before I built the remaining actuators; some of them developed cracks from my... enthusiastic... hammering 😅Doesn't seem like anything structural was damaged, but heating would certainly be better. Cheers! 2) I previously tried a linear bearing instead of the 6 radial bearings, but the carbon fiber tubes that I'm using aren't specced for that level of tolerance; one manufacturers tubes had a loose fit, another didn't fit at all. Linear bearings would be awesome (smaller, lighter, more elegant) but I don't have the cash to get high tolerance, light tubes... yet 😉 3) Good idea for PTFE with larger wall thickness. Very obvious but never came to mind! I'll see if I can find any. Cheers for the ideas!

@jangrewe

Жыл бұрын

@@harrisonlow cheers, 2 out of 3! ;-) I'll let you know if i can think of anything else...

Loving the progress! You can get rid of the bowden tubes and also stiffen your transmission coupling by guiding the cable around pulleys which rotate coaxially with your gimbal joints. The two cables need to wrap in opposite directions so that the total cable length remains constant. Normally this would slightly kinematically couple your linear motion with the rotation, but you can cancel this geometrically by offsetting the linear axis from the gimbal axis by the same radius as the pulleys. You can duplicate this concept rotated 90 degrees to get the other DOF of rotation. If you need help visualizing/designing the pulley layout, let me know, but I think it should be a feasible way of getting well-constrained cable motion to the actuator with almost zero flex/compliance or motion coupling. The pulleys could actually be a single, dual groove pulley since they will rotate in tandem, but you can also just use 2 parallel pulleys or one on each side of the joint itself.

@harrisonlow

Жыл бұрын

Thanks! Hmm, I'm having difficulty visualising what you're describing. Do you know of any real-world systems that use something similar? I do quite like the sound of a tighter transmission 😁

@ericcmcgraw

Жыл бұрын

@@harrisonlow Skyentific has shown a mechanism using pulleys co-axial with arm rotation, but for the purpose of actuating the arm itself. kzread.info/dash/bejne/p6h4w8mopduzZbg.html The idea I'm suggesting simply uses such pulleys to guide the cable onto and back off of the rotating body. I will try drawing the idea a little later and sending a picture if you would find that helpful.

@harrisonlow

Жыл бұрын

​@@ericcmcgraw Very interesting! I just watched that video and I think I have a better idea of what you're describing. I have a few thoughts: 1) I'm quite averse to shifting the linear axis away from the centre of rotation as that makes the inverse kinematics for the stewart platform (what these actuators will be used for) significantly more difficult. I don't know exactly *how* much more difficult, but I started working through it a while ago and after a while decided to just make the joint axes coincident with the linear axis 😅 2) This design looks like it'd require quite a few parts, and at the scale I'm working at, they'd have to be fairly small. I'm trying to cut down on complexity as much as possible (especially where it concerns manufacturing). 3) As a slight (maybe) spoiler, I'm actually thinking I'll change the lower universal joint for a magnetic joint, in a similar fashion to the upper joints (this video if you haven't seen it already: kzread.info/dash/bejne/c3edxsOtj6i3Y7Q.html ). I'm not sure if this would affect the design you're describing, but it seems relevant to mention. Again, thanks for the idea! I'm interested to know what you think about the above points 😊

@harrisonlow

Жыл бұрын

@@ericcmcgraw Grr, I think KZread may have removed your last comment. I can see some of it in my notification, but nothing past a "small error" re. shifting the linear axis. Did you include any links? KZread seems to dislike links to external sites 😡

@ericcmcgraw

Жыл бұрын

@@harrisonlow Yep, I tried obfuscating the link by spelling it out, but still no luck. Here's the comment with the link removed: 1) I thought of that too, so I played around in Geogebra and found that you could still assume the linear axis rotates through a single point and you'd have relatively small error compared to reality. Assuming ±45 degree range of rotation, and 10mm diameter pulleys, the actual length error would only be ±0.1 mm throughout the range of motion. Here's the Geogebra file if you want to play around with it: (redacted) There do exist solutions which would cancel this error exactly, but the complexity is higher still. Let me know if you're interested in them. 2) I've found some design possibilities which add only a few additional pulleys to the part count you already have. Complexity is a little higher, yes, but the benefits are: no sliding friction in bowden, no risk of bowden buckling, higher tension and higher stiffness capability. It's up to you whether it's worth it. 3) Yes I saw those ball joints, it's a pretty elegant solution and I like how it makes the actuators detachable and modular. Of course the only drawback, as you mention, is the pulling force capability. As you start to push the limits of acceleration (how many balls can it juggle at a time, etc.) you may want to be able to apply high forces in both directions without worrying about the joints falling apart. Again, it's up to your own judgement (and level of ambition 😁)

Wanted to give a Hard Congratulations for hitting this milestone through your Project. 👏👏👏 Looking forward to see where it goes

@harrisonlow

11 ай бұрын

Cheers!

Wow...brialliant!!! Thank you for sharing your inspirational work!!

With the encoder for leg length measurement: it's going to be slightly non-linear due to the changing diameter of the bobbin/spindle, do you think it would need correction? If so, a simple lookup table could work well.

@harrisonlow

Жыл бұрын

Haha I remember a question in high school math on this exact topic! Something about a toilet roll being unwound and dealing with the changing radius. I would be very interested to know how big of an effect that would have; my intuition says not much, but I've been wrong before 🤔

@rymannphilippe

Жыл бұрын

Ben you are a smart thinker.

@TheFogmachine803

Жыл бұрын

You can use a badge reel that winds and unwinds really small wire/string to measure linear travel without the same issue of the radius changing that you have using that CF spring. A commercially available sensor product that does this is a string potentiometer.

What if the spacers were eccentric so you could rotate them for a perfect fit? Might not work with a 3d printed part. Seems like your solution with a few sizes works great already though 🙂

@harrisonlow

Жыл бұрын

That's a very interesting idea! One potential issue I can see with that is that it'd make straightening the extending rod a little tricky. I didn't explicitly mention this in the video but I've been keeping each "set" of spacers (ie. top three or bottom three) the same size so that the central rod is kept centred. Having the spacers be eccentric might make this a little difficult. Very cool idea though and I'll keep that in mind if I need to do anything similar in the future. Cheers!

@charliewynn3210

Жыл бұрын

@@harrisonlow ooh, very good point about wanting to put the same spacers around so it stays centered!

Fascinating project, thanks for the video

Nice work! Inspiring! I had issues with PTFE tubing buckling (from compression) when I used them as bowden cables. I've wanted to try the small coils (smaller than bicycle kind) but I never got around to it (and project had already met its goals).

Excellent design. Thanks very much for sharing!

what a great design, thank you for sharing. i'd go for cheap brake cables with a teflon liner, that way you get rid of the backlash and its essentially friction free.

Great build. Just found your channel so excited to see what is next. In addition to the hoover method for string, I have used a can of compressed air to blow the string through. This works well on small strings in tubes too small to use the suction method. (Saved our butts at a robotics competition when rubber tubing began to stretch- we blew string through and tied it tight and it got us through.)

@harrisonlow

Жыл бұрын

Great idea! Never heard of that and I've got a can of compressed air on hand. Cheers!

Awesome design! I keep thinking of all the possibilities.

Skyentific did a video a few months ago exploring different bowden tube types for cables. I found it very helpful.

Sweet man. I watch Skyentific all the time and just now I get your video recommended.

Very well done. Genius I should say. Thank you

This is super cool! Thanks so much for sharing this!

This is just a simple idea, but you could keep the PTFE tubes and make some sort of either hard plastic or TPU sleeve to brace that goes around the tube to prevent buckling, just the parts that curve up to where the string meets the PTFE adapters/nuts so that the only part of the tube that has not bracing is just the straight-away section to the motor. Cool project nevertheless, some pretty cool innovation here! I always thought regular linear actuators were slow so this is the perfect design for some practical applications!

Great work, great editing, very clear

That’s really amazing thank you so much for the video! Have a look at synchromesh cables if you need more precision

Great video and walkthrough! Well done. I'm so impressed by your design. I have thing for string pulley systems.

@boonjabby

Жыл бұрын

.. so you like puppets ?

@gerarddantel5931

Жыл бұрын

@@boonjabby 😁 only those that have pulley systems... Not just strings!

If you do decide on another iteration, you could use the three linear actuators to make a very large and potentially fast delta printer. Edited to add: Think Bike cables for the cable issues. The tubes have a twisted wire inside to ensure flex and length of housing unlike PTFE tubes that can ' crush ' under stress. You may be able to find similar gauge wires as the string or at least close enough for your purposes.

Hello, try wrapping your ptfe tubes with a metal spring. will add some support about the length of the tubes in sections that demand a turn for fitment if you want to keep the cost low. otherwise you could consider a hybrid setup using metal cable bowden sections and then connecting the strings in the “interface” at the pushrod side and motor side. this should reduce stretch and keep the weight where it needs to be and where it shouldnt. keep in mind the material compatibility here, kevlar is strong and the ptfe will handle the abrasion for a little while, so periodic change outs may be required. nice job!

Genious man , thank you for sharing

Great job mate, I really love cable mechanisms. Just as a fun fact, engines use half-bearings with different thicknesses to compensate the manufacturing variations between parts, your solution really made me remember that, they're also diferenciated by color. Again, great job!

@harrisonlow

Жыл бұрын

Haha yep, colour differentiation helps so much. Got the idea from the adapters that came with the encoders to fit differently sized shafts. Such a simple solution! Cheers for the kind words 😊

Very nicely structured and well explained video! Keep up the good work! Edit: i really like the simplicity of the design with the range of motion it offers. Thinking outside the box work here!

@harrisonlow

Жыл бұрын

Cheers!

Man what a great design! gonna print one to test some ideas I have

Excellent work!

Bravo! Nice innovation!

Awesome!! So many ideas!! I had an idea regarding the string under the bearing, but then the person's comment about the Gothic Groove Bearing seemed better. I was going to suggest doing something where it uses two strings instead of just the one, a string on each side of the bearing somehow. Maybe something like that with the grooved bearings as well could work? Great stuff!!

These would work perfectly in my world-domination robots! Subscribed!

The ptfe tube buckling could be remedied with something like bicycle shift cable. The bending looks pretty high energy! Thats wild! Impressive machine youve built. Odrive looks amazing

They look amazing!

How to get rid of the bowden tubes? Why not use a flex shaft to relocate the drum from the motor shaft to the base of the actuator? This would also save space by allowing you to attach the pull cable to the bottom of the actuator shaft. The pull side of the drum would be centered under the shaft. The push cable would still need to run up to the pully and back down to the bottom of the shaft. No more strings running to the top. How to remove the backlash? Why not just add a spring to your newly relocated drum mount and turn it into a tensioner similar to a serpentine belt tensioner? A TEMO flex shaft is like $15.

@harrisonlow

Жыл бұрын

Interesting! I'm not sure I 100% understand what you're suggesting, but I have a few thoughts related to this: 1) I'm interested by the idea of flex shafts / push-pull cables (are these the same things?). I've seen people suggest them on the Wintergatan project but haven't had the time to look into them much. Are they particularly flexible? 2) For my application (Stewart Platform) it's somewhat useful to have the motor be physically separate from the actuator itself, as the actuator will be moving around and the motor would get in the way and just be more mass to move around. 3) An unintended boon to the way I have the strings routed now is that the end caps on the central tube are only ever pulled in towards the tube. This is rather nice as it means that they'll never get pulled off if the string pulls too fast/hard, since they're only connected via a not-super-strong interference fit. I could of course make that fit better, but that would be more effort! Re. backlash removal: Yes! I agree with your idea of the spring, and this is something that I will absolutely be adding if backlash becomes an issue for whatever reason. Cheers for the ideas!

Wow, that's an amazing mechanism! It's a bit like a hydraulic actuator, in some sense, because they typically (?) apply force through high pressure to one side of the piston at a time, rather than using pressure and vacuum on one side.

Great stuff ! looking forward to see your progress. you could look for some excentric nuts, these are often used in cheap cnc builds, this would add some weight but makes it easier to adjust fully assambled. Or borrow the idea and see if excentric 3d printed sleves on the bolts will work. Another option would be to use linear bearings commonly used in 3d printers, Im not sure how well they work with carbon tubes, but its is worth a try.

This is awesome! I recommend bike shifting cable lubricated with silicone spray, its thinner and has a lot less resistance than bike brake cable. The housing is reenforced to prevent buckling and you can easily refill it with silicone if it starts to stick

@conorstewart2214

Жыл бұрын

How would it hold up long term? When used in bikes those cables don’t need to move an awful lot compared to what they would in this application.

Amazing what you are doing.

Very nice solution! To make it more long-lasting, I strongly suggest to put an outer liner of hard PU on the bearings with a slight groove. Rolling friction will of course increase a little but the contact pressure and noise will decrease radically. Another alternative is to use really thin-walled stainless tubes with carbon inside for strength and stiffness and the bearings as is.

Random ideas: Get a CF tube that the PTFE tube fits in, put it in there and now its stiff. Use as one kf the trio of stiffening buddies. take 3 of the stabilization bearings, and put them on the internal end of the big moving CF rod, instead of bearing in onto the central rod, bearing out onto the trio of kuter rods. Would increase the weight of the reciprocating mass, but perhaps will reduce wobble? IDK, thats all i got so far. Great work. I really hope to see this go somewhere awesome!

@harrisonlow

Жыл бұрын

I like the idea of bearings on the main push-rod! I hadn't thought of that before! Might be tricky for a few reasons: 1) While the CF tubes are stiff, having the central tube pushing against the outer tubes (via the bearing) might cause the outer tubes to flex a little 2) I think you've hit the nail on the head with respect to excess weight: if the actuator's moving at > 2m/s, I want to keep that as light as possible. Cheers for the suggestions, and I hope to see some more of these ideas in future designs!

Hi!!! You can use a V profile bearing, perhaps using TPU as a bearing cover. I think that will provide more stability (at least two contact points per bearing). This V profile can allow you to run the thread close to the apex of the V.

AWESOME PROJECT!!!

Ive just just read every suggestion and thought of the most mentioned one's. String in support legs, use of bike cable sheathing, different shaped bearings. But didn't see any suggestion of just running a rubber pully wheel at the top of the 3 CF legs that snugs up against the CF tube with a tension adjuster. So your motor would spin the rubber wheel instead Would save string going to top and bottom of main CF leg. Obviously there could be slippage, just a thought. Great idea thou. Im subscribing............. Now. Thanks for sharing 👍

Very cool reduction in moving mass! Fine Work

This is very cool. Great job

Yeah definitely I think other peoples of said bicycle cable and maybe some Kevlar string would work really well. very neat.

This was super cool! Subscribed.

this is a pretty brilliant design. I am curious to see what sort of loads it can move and sustain. I can see a lot of automotive applications for this sort of design.

the almighty algorithm has blessed this man

Phuk yeah! This is dope Bro Nice work.

Great work!!!!

Hi there. Great video. I have no need for actuators, never thought about them in my life... But sat and watched your video and now I kinda want to make some! Nice work! For the cable issues, I was going to suggest brake cables from a bike... I notice its been said a lot already so I guess its something you might try? Also, to stop the cable moving about and getting under the roller, perhaps add some kind of loop to hold the cable in place? Keep up the good work!

You have done a fantastic job 😀😀

Great attempt

Excellent work! Your solutions to inherently slightly sloppy FDM parts is very smart! Somebody get this guy a SLS printer ;)

@harrisonlow

Жыл бұрын

Oh man I've been dreaming of having some better tools; SLS printer being pretty darn high on that list 🤤

Amazing design! Nice one!

Really impressive performance! The bearings might be larger than needed.

I've had a similar problem with guiding tension lines. I ended up using endoscope grade coil pipes and I was able to get them fairly cheaply.

this is some seriously high quality stuff

You could make one of the bearings be in a tab that flexes a bit. You flex it out to fit the rod then the bearing will have tension against the rod. It's like making the bearing be pushed by a spring. I would recommend PC filament for this kind of thing as it retains its shape well when tensioned and is strong

This looks very nice and I can't wait to see this running. @11:57 - is exactly why kiting shops don't sell these kevlar lines over here any more. These lines cut fingers too so we are now allowed to only used kevlar with a braided cover. @James Petersen suggested the use of bicycle brake cables but this is the wrong type to use. Outer brake cables can be compressed. You could try to use the outer gear cables instead, a lot of them even already have a PTFE liner inside to reduce friction. But do go out to a bike shop, tell them why you need these and check yourself if these are flexible enough for your use. Original Shimano cables are most likely way too stiff.

@harrisonlow

Жыл бұрын

Cheers for the suggestions! That's interesting re. kevlar strings. Thanks for sharing that! Thankfully I'm pretty sure I have both brake and shifter sheathes lying around that came with cables for my bike. I'm planning on making a testing rig to test a bunch of the ideas that everyone has suggested, and I'll absolutely be trying shifter sheathes. Cheers!

Mountain Bike gear change cable outers would be perfect to replace your string guide pipe. Brake cables are just wound steel outer, but the gear change cables are not spiral bound and have a teflon/ptfe liner - they are designed for both push and pull actions with low friction.

For a cable system, just look for something like a bicycle brake cable or derailleur shift cable. They're usually braided steel cables with a solid shield tube and some kind of plastic (probably PTFE) lining. It's easy to cut with hand tools, and is intended for durability and longevity in some nasty environments. Have you tried using one of those constant-force springs inside the cable spool to take up backlash?

Great video! Can't wait for the next one! I don't have any experience with cabling systems either, but I have used pneumatic tubing like this for other projects (something like McMaster 9446K21) and it's considerably stiffer than bowden tubing. It won't be as slippery a ptfe, though, so it's possible the tubing could melt at high enough speeds.

@harrisonlow

Жыл бұрын

Thanks for the kind words 😊 Interesting! By stiff, do you mean in compression, or bending? Jugglebot needs fairly flexible tubes (in bending) to not restrict its range of motion. I WISH we had McMaster Carr in Australia. Honestly such a pain to source parts that are so easily available in the US 😭

@tategeiger5317

Жыл бұрын

​@@harrisonlow In compression - since the walls are thicker, it's much less likely to buckle. It might not be quite as bendable as a bowden tube, but I think it would bend just fine even at the speeds you're running. They should be pretty common, lots of home air compressors use similar tubing for their hose.

@harrisonlow

Жыл бұрын

@@tategeiger5317 Thanks for the suggestion - I will start the hunt for some pneumatic tubing! I agree re. bending stiffness: it wouldn't need to be as flexible as the PTFE to be a non-issue for my purposes

Awesome project and another excellent video! Have you looked into control cables? Just for info, not to replace anything. They're common for throttle, choke, clutches.. but the industrial versions can move hundreds of pounds. Steel wire core wrapped in a liner, inside a flexible but strong conduit. Optionally they have low friction inner coatings and come in push pull (very expensive over 7" of travel) or pull only configs. Thanks for sharing your info!

HarrisonLow, this is amazing education!!! Love it. Wish you were in the USA, so we can do an STARTUP... Wish you the best!!!

Id recommend looking into either spectra or dyneema line as its EXTREMELY strong, zero stretch, abrasion resistance is off the charts and its very affordable. As for the play in the bowden tube, you could probably route the ptfe tube through the carbon fiber tubes or... You could use some rigid brake/fuel line or copper condenser coil tubing to route the ptfe through which would remove any loss of motion there resulting in a more accurate and faster action.

Really impressive, I love the pneumatic tubing to protect the string. Did you consider using linear ball bearings for the slides as opposed to the radial ones? It makes packaging all the bearings so simple, we have used them in the past for linear motion in FRC which has similar design constraints as this.

You should consider a capstan style of transmission to the rope. Also, if you want to ba able to desassemble the tubes from the plastic, you can make a full cylinder, drill it in the center and screw in a slightly oversized screw to make it press fit

Great project! You could try grinding a small groove in the bearing to accommodate the string? Some bearings do come with a groove already in them.

@harrisonlow

Жыл бұрын

Yep, that's a really good idea! I bought some bearings of different shapes and sizes (U- and V-cut bearings, as well as some "gothic profile" ones) and I reckon they should work really well. Cheers for the suggestion!

Had a similar problem at work, use 1/4 in copper tube and a pipe flare tube. Decently slippery and much much more robust

As you said at the end the PTFE tubes will 'wear out' over time. Have you thought about using brake cable covers/sleeves from bicycles? If you can find something that has a proper inner diameter. Those are lined with either composite or metal weave which makes them much more wear and longitudinal compression resistant

@t1mmy13

Жыл бұрын

Totally forgot to say, this is a super cool project! Subscribed and exited to see more

Looks nice, would be interesting if you could use the same design to make an arm with 6dof, could be used as a platform for all kinds of things.

I'm a CS guy, not an electro one. The linear actuator I saw seemed difficult to use, so I made a simple "linear actuator" for a kinetic sculpture with a stepper motor, a string, a tube and a spring. Nothing compared to what you did, but this made me realise of what potential just a simple motor + a wire can have, you definitely extracted the full power of this mechanism :D

@harrisonlow

11 ай бұрын

Haha the potential isn't exhausted yet! I've been working on a improved version that is better in many ways. Will hopefully finish collecting data and putting the video together soon 😁

Brilliant

Bicycle brake cables have excellent compression strength while being somewhat flexible and light! Also, they're relatively cheap. They are usually lined with some softer plastic but they are designed to house steel cable under high tension. may be worth a check, but not sure if the diameter of your aramid string is small enough to encourage cutting into the plastic liner of those cable housings.

@mrmatthewking

11 ай бұрын

Came here to say this.

Also, the spring return could be a coil spring, or similar, in an assembly which rotates and makes contact with the actuator's shaft for its return.