How do you Improve the Grip of a Drive Roller?

[rawly old]

Well Hap,
Let's just say Detroit wasn't ready for innovation.
I didn't have much luck trying to find backing for
my snowboard prototype back in '66 either. They
were banned at ski areas shortly thereafter.
Not easy being ahead of your time. Lesson, don't
make anything that threatens an intrenched industry.

 

[Richard H.]

With a curved drive roller, the 'larger' circumference is moving faster than the smaller, meaning that it moving faster, in MPH terms, for a given RPM. Where it meets the tire, the larger drive circumference is rubbing against a smaller rubber circumference, meaning that it (the rubber) moves slower for a given RPM. So, both the tire and the roller work towards increasing friction in this drive configuration.

There you go again, confusing the issue with applied mechanics, lol. Just kidding, though I know in reality it won't dissuade the idea from being recycled periodically.

 

[rawly old]

Though I've never made a dime I don't feel I've failed.
It's very gratifying every time I see today's products
starting to catch up with me. They may yet do so.



Anyone who thinks there is no such thing as a
perpetual motion machine need only look at
the night sky.

 

[Ludwig II]

When I was young, I asked questions, like why is there a tread pattern on a tyre, to be told "you have to have the gaps, that's where the grip is". I couldn't see that, and then a few years later, racers were using slicks in the dry because more rubber gave more grip. And I asked about why the wide slider was on the outside of the thin fork leg, to be told "they won't work the other way round". Now, only antiques use the old style forks, everything is the modern "upside down" pattern with a nice wide outer tube supporting a skinny inner one.

 

[rawly old]

Hap,
I've thought through the idea you sent me, and I'm sure it could be
made to work. Still, it's a bit complicated. I'm old and don't have
the time or energy for it. At this stage, I'm all about simplicity.
I am not saying give up, but, like the man said, invention is 1%
inspiration & 99% sweat.

 

[happycheapskate]

I still think tires with tread patterns or ridges are more effective generally, because they corner well and the siping or treads give way a little, allowing the tire to stay in contact instead of slipping at many occasions a bald tire would. Also, the old junk about bicycle tires not hydroplaning is bunk to anyone who's ever rode a bicycle on a blacktop road in Texas!

Does anyone here have a lathe? I have a great idea for a roller, needs to be made out of a steel or steel alloy, to fit on a Dax Friction drive (pretty sure it's 5/8'' across the axle).

 

[loquin]

Loq.
Still it works. consider the vbelt in your car; the
sides travel farther than the center. there's probably
extra friction there without signifigant detriment
to function. I wonder how rubber to rubber would
work for a roller?

I'm not saying it won't work - what I'm saying is that it will be less efficient than a straight roller, and because of the differences in roller diameter (which, in a small drive roller, result in higher percentage difference in diameter than the wheel differences, and a resulting greater speed difference at different points on the roller.)

A V-belt is a little different. The belt only stretches a tiny bit on the outside part of the circumference. On the inside portion of the belt, it is compressed somewhat more, lengthwise. But, as the inner part of the belt is contained within the V channel of the pulley, when the inner portion is compressed lengthwise, it tends to spread out and grip the inner faces of the V-Channel in the pulley.

As to friction - a V-belt IS less efficient that a chain. (because there is some flexing of the belt.) A new belt, properly aligned and tensioned, is about 95% efficient, whereas a well aligned chain is upwards of 98% efficient.

When using a very small diameter pulley, the heat buildup induced by this flexing can be significant. You can reduce heat/improve efficiency by using a notched V-Belt. Granted, this does reduce the grip somewhat, but in many cases, it won't be an issue.



Also, note that when you compare the two images, the toothed v-belt is a little 'flatter' than a standard v-belt. This will reduce the differences in diameter, from inner surface to outer surface a little, which also reduces the flexing and resultant internal friction losses.

 

[loquin]

... Also, the old junk about bicycle tires not hydroplaning is bunk to anyone who's ever rode a bicycle on a blacktop road in Texas! ...

We have the same problem in AZ. After a rain, it is REALLY slippery. It doesn't rain often, and when it does, for some time all the accumulated oil droplets that get dropped on the road surface floats to the top of the water as a thin, slippery oil film.

I think what you're talking about is not hydroplaning, but instead is the result of the tire getting a thin layer of lubrication between the rubber and the road.

 

[grinningremlin]

Yup, takes much speed for actual hydroplaning.Now you wanna talk slick, that black stuff that grew in the gutters where I lived in SoCal, you could spin your tire like it was salted ice.
I found my problem with roller grip was all too much CC's and the jumpy 2-stroke throttle.Since I moved to the EH035, no slip, about 500 miles on a new Schwalbe Marathon and it still has "new tire" flash/ridges.

 

[rawly old]

Just a thot Hap,
If you've no lathe, I cut the head off a 5/8" bolt and ground one end
to be threaded for the drum to make my belt drive. I had to sand it down
a bit to match the bearings. You could cut some shallow grooves in one
and build it up to shape by wrapping it with glass tape And J&B weld.
My belt drive works as well as my roller under power. It's just more
hassle to disconnect for pedaling or coasting. Belt drive below: