@matroosoft4589 3 ай бұрын
Sir I was the one of the people asking for an update video (asked in the last video). Thanks for the response there and now here to the other person asking. If you're feeling you're close, yeah I understand it's better to focus on finishing it. I decided I took some time to watch the livestream and want to comment on the capstan. I agree that it is engineering wise a very neat solution. But in regards to inprinting the syncromesh into the capstan, I think that will introduce a problem. If you look at the threaded capstan, the wire moves up and down a lot. The same will happen when imprinting the syncromesh because that can only be done in a spiral I think? And that's because the cyncromesh cable isn't symetric along it's axis Something you could try is to use dog tag chains/ball chains, which are symetric along their axis. Then you can simple design long grooves along the axis of the capstan. This is probably easier to print too.
@harrisonlow 3 ай бұрын
Good idea! I'm not sure the main 'string' inside dog/ball chains would be inextensible enough to not cause issues with stretching, but a similar string would be great for this application! As it happens, the synchromesh cable actually wasn't too tricky to model in a spiral (check out the "working session" stream that I did after this one) so I think synchromesh would work fine here if I decided to stick with that design.
@DavePetrillo 3 ай бұрын
This reminds me of a mechanism I saw from a company called rise robotics. They make different style actuators now, but 10 years ago their first one was called a "differential conical drive." It's similar but overcomes the issue with the capstan slipping.
@harrisonlow 3 ай бұрын
Very interesting! That was a very cool rabbit hole to dive into. I can see how my design here reminded you of that one! Cheers for mentioning it here 😊
@harrisonlow 3 ай бұрын
Also for anyone else interested in this, the Rise Robotics design is often referred to as a "Cyclone Muscle" and you can find the patent for it (or something similar?) under patent # US9121481B2
@jonbeno9926 3 ай бұрын
Very cool! I've been thinking that a variable radius spool would be one method to optimize the throw height for a constant stroke and motor.. is that what they are doing with this design, but mapping it to improve load capacity where needed for the mechanism kinematic it is driving?
@harrisonlow 3 ай бұрын
@@jonbeno9926 I think this sort of variable radius spool could potentially work as you describe for this application, though I think what the Rise Robotics group are doing is slightly different; the tapered spool introduces linear motion to the rails that the 'guide' pulleys are attached to, leading to an output of (massively geared down) linear motion. The stroke of one of their designs was only ~ 75 mm but I'm sure it has a huge max force output!
@DavePetrillo 3 ай бұрын
@@harrisonlow the way I understand it, the displacement is ultimately created by the change in the pulley radius. It causes the length of the loop to grow or shrink because the helical paths changed in total length. The carriage slides up and down the spool just to help guide the cord on and off the helical path but does not cause any of the linear motion itself.
@DennisBouw 3 ай бұрын
Just wrap around the string multiple times. Friction for string around a drum increases exponentially with contact angle. This will fix your issue with this design
@harrisonlow 3 ай бұрын
Interesting! I'll give this a go. I feel that the opportunity for slippage would still be there though, even if it's massively reduced 🤔I think the next version will resolve all of these issues in a (finally!) robust way 😁
@synapsomorphy 3 ай бұрын
Your spool problem seems like a great option to try SLA. Resin printers are cheap these days and can make fantastically small features, could help you in other future areas where you need very good tolerances.
@harrisonlow 3 ай бұрын
Yeah I agree about this. I've been wanting an SLA printer for a while but I'm really put-off by the nastiness of the resin and I don't really have a great space for it... I reckon if I ever model a part that would really benefit from SLA printing (like this one, if I were to commit to the design) I'll get them SLA printed from some online service just to get a feel for it before buying a resin printer of my own
@johnbush8224 3 ай бұрын
I haven't read thru all the comments yet but, what about a mini ball chain instead of synchro-mesh?
@harrisonlow 3 ай бұрын
This could possibly work, though the next design takes this even further and aims to do things the "proper" way - using belts 😊