slippery surface Teflon? 1

[greg_smith]

Hello engineers,

Newbie here. I need is a suggestion for materials. I'm building a prototype for a device which consists of a foot operated pedal that must move freely around a roughly 24"x12" horizontal plate. The key to its success will be to reduce friction between the pedal and the surface to an absolute minimum. I'm thinking some sort of teflon for the plate and a soft padded cover for the underside of the pedal might work. It also needs to be very durable, to withstand repetitive forces (foot stomping) and continuous free horizontal movement of the pedal (and foot).
I don't know enough about materials to make an informed decision, so I'm hoping someone out there has some insight. Maybe there's something slipperier and/or cheaper than teflon. and maybe a hard plastic instead of a soft pad for the pedal bottom. I'm also wondering if static buildup would be an issue.
Thanks in advance. I appreciate any ideas.

 

[btrueblood]

Yes you will get static buildup if both parts are insulators. Make one piece teflon, the other a smooth piece of metal, it will give you the lowest static friction coefficient without lubrication. But why not add lubricants of some type? Or use air bearings between the pad and the floor.

 

[greg_smith]

I think lubricants are out of the question because the device needs to be portable, dry, and maintenance free. Also it has to be as low as possible. I thought of just a metal plate with some sort of roller bearings under the pedal, but it might raise the pedal too much to be useful.

 

[btrueblood]

Dry lubricants, e.g. talcum powder (like they use on dance floors), graphite, molybdenum disulfide?

Maintenance free? Gotta at least keep the surfaces clean, can you shroud the setup to prevent dirt/dust accumulation? Otherwise, run a vacuum over the floor/pad regularly...or use air bearings.

 

[robyengIT]

instead of teflon (expensive) you can use polyuretane hardness 95 °S (wear resistant and cheaper)

 

[3DDave]

HDMWPE and polished steal to rub against. Its available in thin sections with sticky backing; usually identified as simply HDMW

 

[greg_smith]

Thanks everyone for all of the ideas. I have some studying to do.

 

[hydtools]

Or UHMWPE.

Ted

 

[3DDave]

That's the one - It is a little higher in friction than TELFON, but because it is so much harder nothing gouges in creating resistance. (just got out from surgery a couple of days ago so my typing is off. Pain meds are not fun.)

 

[MintJulep]

Slippery Coating.

 

[dvd]

Rolling element linear bearings have a much lower coefficient friction than teflon or UHMW on metal - order of magnitude. Also, depending on the application, thermal expansion is really mismatched between metals and teflon or UHMW.

 

[hydtools]

Maybe a grid of roller ball bearings like those used on transfer tables.

https://omnitrack.us/product/ld19-3...hudwVSGXbzVemanWMPTK6apbgrTsa-ZBoCEO0QAvD_BwE

Ted

 

[greg_smith]

Thats the best idea yet. I'll look for even smaller ones

 

[EdStainless]

Or, but the roller balls on the bottom of the foot rest and make the plate just nice smooth plain steel.
There are miniature ones that are only about 6.5mm tall and they will support 20lbs each.
So put 20 of them recessed into the bottom of the foot pad.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[hydtools]

Aww EdStainless, I was leaving that as an exercise for greg_smith.

Ted