Very small torsion axles

[s_forbes]

This is a really neat process, thanks for posting it!

Are you using Buna-N type of o-ring material, or does it have to be some other exotic material for this process to work?

As for the die, how did you decide on the dimensions for the triangular shape and o-ring diameter to use?


Edit: apparently I can't hand out more green dots for your post, but have to say that I love these threads that document building processes!

[Lil' Lavery]

What made you opt for torsion axles over other suspension systems?

[cbale2000]

Would anyone care to explain what building this type of axle accomplishes? I think I'm missing something here.

[asid61]

Originally Posted by cbale2000

Would anyone care to explain what building this type of axle accomplishes? I think I'm missing something here.

I googled it, and it said that these can be used as suspensions for trucks and the like as opposed to the other method of using leaf springs. That being said I have no idea how these work, although they look really cool.

[RoboChair]

Originally Posted by asid61

I googled it, and it said that these can be used as suspensions for trucks and the like as opposed to the other method of using leaf springs. That being said I have no idea how these work, although they look really cool.

It's a small non-rotating square axle around which there is flexible rubber in a tube. The axle cannot rotate in relation to it's mounting hardware. The tube WOULD be able to move freely around the axle except that there is rubber preventing continuous rotation and providing a spring effect relative to the axle.

[sanddrag]

I wonder if it's possible to shove one of these together while soaked in alcohol or something, without needing to freeze anything.

[Tom Line]

I bet a pour-able molding urethane might accomplish this.

[Forhire]

Originally Posted by s_forbes

This is a really neat process, thanks for posting it!

Are you using Buna-N type of o-ring material, or does it have to be some other exotic material for this process to work?

As for the die, how did you decide on the dimensions for the triangular shape and o-ring diameter to use?

Thanks. Standard buna-n. Stiffness is dependent on the shore hardness of the
rubber. We modeled the parts in solidworks and then estimated space required. We ended up facing the die about 20 thou to get the compression just right. The V was a standard 90 degree cutter.

Originally Posted by Lil' Lavery

What made you opt for torsion axles over other suspension systems?

Lightweight, compact, no stops required.

Originally Posted by cbale2000

Would anyone care to explain what building this type of axle accomplishes? I think I'm missing something here.

This page may help explain everything:
http://www.lovejoy-inc.com/products/...uspension.aspx

Originally Posted by asid61

I googled it, and it said that these can be used as suspensions for trucks and the like as opposed to the other method of using leaf springs. That being said I have no idea how these work, although they look really cool.

Common on trailers. They are also used in track systems like on skid steers. I believe this video was part of the inspiration.
https://www.youtube.com/watch?v=dIImhJMbc88

Originally Posted by sanddrag

I wonder if it's possible to shove one of these together while soaked in alcohol or something, without needing to freeze anything.

No. We tried a bunch of methods... pulling, pushing, stretching, and etc. Rubber acts like a liquid under compression. Freezing worked. Liquid nitrogen came from the local welding supply.

Originally Posted by Tom Line

I bet a pour-able molding urethane might accomplish this.

After reading a few patents it was clear that potting the axle in rubber or urethane wouldn't accomplish the correct motion and tension. We made a very crude prototype from wood and learned exactly how they work. As the square rotates the rubber rods roll tighter and tighter into the corner. The rolling action was key.

[M. Mellott]

Originally Posted by Forhire

Thanks. Standard buna-n. Stiffness is dependent on the shore hardness of the
rubber. We modeled the parts in solidworks and then estimated space required. We ended up facing the die about 20 thou to get the compression just right. The V was a standard 90 degree cutter.

Thank you for posting this discussion and sharing the pictures of the process!

What durometer did you end up using on the O-ring material? Did you try other durometers to end up with your final choice?

[Forhire]

Originally Posted by M. Mellott

What durometer did you end up using on the O-ring material? Did you try other durometers to end up with your final choice?

We ordered some soft A50 and medium A70. We used the A50 because it was easier to work and appeared about right.