I Problem with Friction

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1. Feb 4, 2017

Cire Venn

Background: I'm building a treadmill for VR that moves in any direction but I need to figure out if it's worth building or not because of a problem a friend pointed out to me.
Problem: I need to figure out if there's a way to calculate how hard it would be to move this tread by walking on it considering all the forces of your weight and steps are on the rollers which the tread rests between.

Last edited by a moderator: Feb 4, 2017
2. Feb 4, 2017

Staff: Mentor

Seems pretty simple to build it and try it. Go for it!

3. Feb 4, 2017

rumborak

A much more interesting question is, how are you creating a treadmill that can go in any direction?

4. Feb 5, 2017

Cire Venn

@rumborak the picture in my post is a side-view, everything is actually circular, allowing the tread to rotate in any direction around the rollers that encircle it in the way shown.

5. Feb 5, 2017

6. Feb 5, 2017

Cire Venn

@rumborak the tread has to be flexible, but not stretchy or elastic at all.

7. Feb 5, 2017

Cire Venn

Ten of those rollers for the design cost 20 dollars, it's going to cost at least 400.0 dollars to build this thing. I can't just build it before knowing if it'll work or not.

8. Feb 5, 2017

Staff: Mentor

Scale model prototypes are often used for that reason...

9. Feb 5, 2017

Cire Venn

How would I downsize the weight of a running person?

10. Feb 5, 2017

fpsulli3

I'm still not able to picture it. What does the top view look like?

11. Feb 5, 2017

jbriggs444

12. Feb 5, 2017

sophiecentaur

Before going any further you need to consider the structure and topology of the surface you walk on. For it to move in any direction, it needs to be continuous in all directions. A sort of deflated sphere with balls inside it, resting on the drive mechanism; more balls or rollers. It's hard to visualise how to drive and control it. It would also need to slope in all possible directions.
You could have a simple low friction surface and servo'd restraints on the user's feet to give the illusion of walking forward without the base actually moving

13. Feb 5, 2017

jbriggs444

The picture I have in mind is the same as that of @sophiecentaur -- something like an inflated track ball, flattened on top. The more elastic the fabric, the bigger the flattened area can be relative to the complete sphere.

14. Feb 5, 2017

Cire Venn

The top view is a circular closed tread surrounded by rollers. The inside along the edge has rollers too.

15. Feb 5, 2017

sophiecentaur

B ut if it is circular, what do the rollers roll on? You have an enclosed surface with rollers inside it or an infinitely stretchable membrane???
Have you tried a a 3D picture of your design?

16. Feb 5, 2017

Cire Venn

Dude, look at the picture in the post, the rollers inside the round track roll on the rollers underneath and around it.

17. Feb 5, 2017

DaveC49

18. Feb 5, 2017

DaveC49

Why would you need to? The point is to build a scale model of the actual device. You can use a couple of fingers to simulate your running person. You have much more serious geometric problems with the shape of the tread than anything else, particularly if as you suggest it is an inelastic material.

19. Feb 6, 2017

sophiecentaur

We can all see that but what keeps the rollers up if, as I understand, the walking surface needs to move in all directions? The membrane has to get underneath everywhere.
You might be able to use a tray full of extremely small balls and no membrane. That would allow movement in all directions. Steel balls and strong magnets to keep them in place on the tray?

20. Feb 6, 2017

sophiecentaur

. . . . or a massive sphere to walk on - >2m radius.