Friction Drive Formula For Two Rollers In Contact

[shearstrength]

I am currently designing a drive system that involves two rubber rollers to come into to contact with each other. One roller is directly connected to my drive system while the other roller is free turning. I need to transmit the torque from the drive roller to the driven roller.

I would like to know the formula that will allow me to calculate the downward force and the roller width I would need to transmit the required torque to the driven (output shaft) based on the type of rubber and coefficient of friction?

Any response will be greatly appreciated!

 

[Neilmo]

Hello shearstrength,

Take a look in Machinery's Handbook under `Friction Wheels for Power Transmission`.

I think your biggest difficulty will be in estimating your coefficient of friction between your rubber drive roller and whatever material you make your driven roller. Again Machinery's gives some information on this. But, for instance it gives the coefficient of friction between `solids and rubber` as anything between 1.0 & 4.0.

Regards,
Neilmo

 

[diamondjim]

I would make the system adjustable.
Whatever you start with will have to
change as the rubber will harden and change.
What diameter rollers are you using? I would
not rely on friction alone but want some
compression between the two
curved surface to increase the contact area.
Best guess on my part. What durometer rubber
are you using ie how hard, what kind of atmosphere
will it be operating in?

 

[ornerynorsk]

I am currently working on a project using a rubber roller and a steel roller to drive a small eddy current generator. You must make one roll adjustable, as diamondjim suggested. We are using a cheap rubber covered caster wheel as the driver (natural rubber) with a steel roller machined to approximately 32 or better surface finish with output being 8X the input. We have found the frictional characteristics to be excellent, and no problems so far. We use a slight amount of preload to increase the grip on the rolls, and we found that it is difficult to use a precise formula, as your power loss depends on bearing quality and amount of pre-load. Good luck.

 

[chicopee]

I would estimate a range of coefficient of friction between rolling surfaces from .01 to .05 ; however, I probably would not go any higher than .05 and perhaps I would go below .01 depending on surface condition.
Assuming no slippage between rolling surfaces and knowing downward force from driver as P, tangential force (F) between rollers is estimated as the coefficient of friction times downward force (F= u X P ). So far width is not tanken into consideration.

You have not stated what the driven roller is used for, so it is not possible at this point for me to present a formula with width as one of the variables.

But if bearing friction of the driven roller is the only variable then the torque from F must be greater than torque from friction.

During start up you must also consider the inertia (I x alpha) to be additive to torque from friction of the driven roller.
Good Luck!!