# Maximizing the Coefficient of Friction Between Two Surfaces

I am new to this site so please let me know if I can improve my question. A component of a robot I am designing includes a four-wheeled carriage that travels linearly on an aluminum surface. The wheels must be 3.5 inches in diameter, 0.5 inches thick and be able to bear 130 lbs of load together. Beyond that, I have complete freedom to select the wheel material and can surface the sheet aluminum however I want. I can replace the wheels every 10000 rotations and they need to be water resistant. Cost is pretty irrelevant.

How do you recommend maximizing the coefficient of friction between the wheel and surface? Is there a database which shows different wheels on different materials? Are there resources which outline the affects of different surfacing techniques on friction?

I am considering a pretty simple approach using 'off-the shelf' directional tread tires and aluminum oxide anti slip tape like what you see on some commercial stairs. Other ideas include using studded tires and roughing the aluminum surface. The overall goal is to make sure that the carriage does not slide when the wheels are not spinning using mechanical, not electronic/motorized means.

• if the robot always travels in a straight path between point A and point B, then maybe a rack and pinion gears would be appropriate ... or something similar, like toothed belts glued to the aluminum sheet Apr 21, 2020 at 17:22
• Thanks for the comment, but I did consider that option. There is a tradeoff there because a geared track is difficult to fabricate in this specific context (I didn't specify the whole robot for brevity) and also because the rubber allows us a tiny bit dampening. I want to know the maximum coefficient of friction I can engineer so these tradeoffs can be weighed. Apr 22, 2020 at 22:30
• i was talking about these ... glue down with teeth facing up ... duckduckgo.com/… Apr 23, 2020 at 1:16
• I did not know about these, definitely a possibility I will consider; thank you for mentioning them! I am curious what other options there only because this track will be bearing about 130 lbs and might wear down too quickly... Apr 24, 2020 at 15:57
• i don't actually know how long they would last in your application .... you could try using the ones that are used as timing belts in race cars Apr 24, 2020 at 16:15