Can a roller be fitted off-center?

[mifletz]

Does a roller have to be centered exactly in the middle? Can it be displaced to the side, or is centering critical?

 

[professor]

Think about it. Why would it need to be centered? Looks fine to me.

 

[vegaspaddy]

i have a roller driving a cambered wheel on the rear of a trike, pain in the butt...

put so long as the roller makes contact with the tire its going too roll

http://www.motoredbikes.com/showthread.php?t=13441&page=10

 

[Esteban]

I have seen plenty of friction drives working well with the drive roller up to 1/3 off center.

 

[Happy Valley]

As long is it's not at an angle off-center.....IOW the drive spindle should remain parallel to the rear axle.

 

[Esteban]

I would believe that if is too much off center, outboard [ engine hanging farther away from bike ] it would cause more stress on the spindle & bearings.

 

[loquin]

You'll get somewhat increased friction (and associated wear) by having it tilted away from 90 degrees from the plane of the wheel. (On an angle, the tire in contact with the roller on the 'high' side is further away from the axle than the point in contact at the 'low' side. Essentially, you have two different radiuses...(radii?) Since both points on the tire HAVE to rotate at the same RPM, the 'High side' of the tire will be moving past the roller (relative to the roller axis of rotation) faster then the 'Low side' of the tire. This will lead to a scrubbing action, increased heat in the tire and roller, and increased wear.

That being said, if there was a 1/4 inch difference between the two radiuses, it would result in approximately 2% 'speed' difference between the two points. The more 'grip' the roller has on the tire, the more power you'll lose.

This difference in radius of contact is the reason why it's a bad idea to have a concave shaped friction roller.

 

[mifletz]

To what sort of pressure should a tyre for friction drive be inflated?

How deep should the roller be depressed on to the tyre: lightly or firmly?

 

[darwin]

I had that same issue with my BMP/Titan kit and used washers to space it correctly with the u hanger. Tire should be towards the max psi that the sidewall says and the roller should depress the tire 1/4 to 3/8ths of an inch.

 

[mifletz]

The sidewall of my Continental "Town & Country" tyre says "inflate 35-65 psi". For normal pedalling 50 was enough for me. Will taking it to 60 bring any advantage when the roller is engaged?

Any disadvantages with a psi near the limit?

At what sort of psi will the tube blow?!

Staton in his instructions says "depress the roller 1/8" on to the tyre". Maybe that is not enough?