Tanaka 40cc PF-4000... now what?

5-7, no surprise on Staton not returning your box; I've had
some rather unpleasant dealings with the man myself. My
tire woes have ceased since I tooled my own slightly
concave roller with a semi smooth surface. It grips even in
the wet but can't chew a tire.
The pulley on my belt drive polished out, so I'm back to
friction. It's okay though with this roller, and I like being
able to just lift off & pedal on flat quiet back roads.
 
The trick is, by using a slightly concave arc to conform to the
tire profile, you get more surface contact than a straight roller
without the need for as much down pressure. The roller is smooth,
but has shallow lateral grooves with rounded edges at 1/4"
intervals. It grips without biting.
 
Otero,

I too would love to see some pics of the roller. I assumed that the quality rollers were actually concave out of the box for the very reason you mentioned. I work on race cars and tire dynamics /traction is such an important part of the sport. I always assumed around 90 deg wrap around the top of a tire would be a good friction/drag ratio.

Rob
 
I detract my comment about wrapping a concave roller around a tire. I overlooked the speed differentiation between the "inside" and "outside" portions of a concave roller.
 
It works, as do the different portions of a v-belt. Outside travels farther on
on the roller, but the outside dia. of the tire is less. They balance out.
A highly curved concave roller might work for skinny tires as well. It's
simply a beltless pulley.
 
Last edited:
I thought that too, but unlike the "give" in a pulley belt, the ratio of "scrub" is a lot more accentuated. ie: if the O/D of the roller is three times the diameter of the I/S, the comparative ratio is wrong compared to the wheel.
Replace the shoulder of the tire with a gear and the outside of the roller with a gear, do the same for the center of the roller and tire, and dive the "gear (roller) shaft" at one speed. See what happens.
 
Well, all I can vouch for is that the roller I'm using, which has about
30 degrees of arc over a 1.95" tire, works exceedingly well without
slipping or chewing the tire.
 
I think the extra contact area could be helpful as you noted. The tire has a bit of give in it too. Race cars and karts slick tires work best at certain slip angles: a degree a distortion/deflection, temperature/pressure and a small amount of slippage (skidding). You may have found a similar condition that works.
 
You must log in or register to reply here.
Back
Top