OK engineers, good idea or bad...

Highlander179 · 02-17-2006, 08:08 AM

Invention: Counter-Rotating Brake Rotors

http://www.reverserotatingrotors.com/index.html

Xa3 · 02-17-2006, 08:11 AM

Let Rossi test it out and see what he says...

-ChaZ

Highlander179 · 02-17-2006, 08:15 AM

why? is his opinion that only one that matters?

wswartzwel · 08:34 AM

I would like an explanation of how rotating mass is going to have less force because it is spinning the opposite direction.I partied my way out of phsyics, so if an engineer has an answer I would love to know..... I was under the impression that newtons 1st law about an object in motion would hold true regardless of which way the rotors are turning....

smells like smoke and mirrors to me....

timf · 02-17-2006, 08:45 AM

I'm the wrong kind of engineer, structural not mechanical, but it seems to me that the intent is to eliminate or greatly reduce gyroscopic precession by having a mass spinning opposite of the wheel. Gyroscopic precession is the main factor (IMO) in countersteering. (lots of controversy expected here). Personally I would be skeptical that eliminating precession is a benefit. Seems that it could introduce a whole new can of worms just when we were getting used to the old worms. Better the worms you know than the ones you don't.

On the other hand it could be a great thing.

On the other other hand it's just more mechanical moving parts to wear out, require maintenance and use up some of the horsepower that we all respect and love.

Anton · 02-17-2006, 08:54 AM

It does work, well sort of.

http://science.howstuffworks.com/gyroscope1.htm

Read the part about precession.

A wheel with a counter rotating disk will weigh more than a whell with a bolted disk. You still have more rotating inertia. In a straight line it will be the same as having a heavier wheel. In corners, you will act as though you have a lighter wheel, but heavier forks.

Xa3 · 02-17-2006, 08:57 AM

Quote:

Originally posted by Highlander179
why? is his opinion that only one that matters?

Because he is a professional tester, that's why.

Better let the professional have fun with new things and better to have it blow in their face than have that happen to us.

-ChaZ

wswartzwel · 02-17-2006, 09:01 AM

Anton, Thanks for that link... Helped me understand how it works!!!

still unsure I would want my brakes to be connected to the wheel via some reverse gearing though.

roger albert · 02-17-2006, 09:34 AM

Then engineering seems incomplete.
Good high school first order approximation.

But,

Not clear that reduced rotational MOI more than offsets necessary increase in unsprung mass

Not clear that reduced rotational MOI more than offsets necessary increase in complexity and reduction in reliability

Not sure how lash in system is accounted for and it's affect on grip near the limit is handled.

It is NOT true that gyroscopic precession is the only factor in tank slappers. It is a pendulum operating around a pivot. Mass and momentum. Regardless of procession

The idea is damn cool. Very skeptical of practical implementation.

Will watch with interest anyway. At least they're trying.

SCOTTinNJ · 02-17-2006, 09:40 AM

Quote:

Originally posted by wswartzwel
still unsure I would want my brakes to be connected to the wheel via some reverse gearing though.

yea, what happens what that bolt at 42 breaks? You freewheel the disk and lose braking I suppose?

markjenn · 02-17-2006, 09:42 AM

The reversing could easily occur with some kind of planetary gear set. Not sure how this would affect braking though.

There is an interesting idea here. As I understanding it (and this guy's site BADLY needs some graphics), they're trying to reduce gyroscopic forces by having the rotors turn in the opposite direction.

I don't think it would be a good idea to totally eliminate gyroscopic forces and I don't think, with reasonably-sized rotors, it would be possible. Gyroscopic precession is a vital part of motorcycle steering - when you counter-steer into a corner, there is a pro-lean gypscopic force that tends to lean the bike the way you want it, so the countersteer causes two valuable things to happen - the contact patches of the tires are steered out from under the CG of the bike AND the bike is pushed into a lean.

What you could potentially do is dramatically reduce gyroscopic forces similar to the benefits you'd get from lighter wheels and tires. There would be a couple of downsides though: higher unsprung weight for whatever the rotors and gears would cost you above and beyond a coventional rotor, and less straight-line stability. The bike potentially would be easier to flick through transitions and more nervous in a straight line.

I'm skeptical this whole thing is practical, but I wish the inventor the best.

Someone who knows graphic arts needs to help him out with that web site though.

- Mark

repoe3 · 02-17-2006, 09:52 AM

Quote:

Originally posted by SCOTTinNJ
yea, what happens what that bolt at 42 breaks? You freewheel the disk and lose braking I suppose?

and considering the sheer force applied to rotors when you grab hard. i dont see any significant method of attachment for the disk itself.

repoe3

Highlander179 · 02-17-2006, 09:52 AM

Quote:

Originally posted by Xa3
Because he is a professional tester, that's why.

I would value Jeremy Burgess' opinion a lot higher than VRs on this one.

wswartzwel · 02-17-2006, 09:53 AM

I also wonder how the calipers and mounting design of the forks, would be compatible with reversing the braking forces applied to them.

Xa3 · 02-17-2006, 03:49 PM

Quote:

Originally posted by Highlander179
I would value Jeremy Burgess' opinion a lot higher than VRs on this one.

One thing does make me wonder. I was looking at the patent picture and I noticed that the brake system is located behind the fork. I was thinking that the brake system are put behind the fork for a reason, to provide better braking.

But with the brake rotor counter-rotating, wouldn't it make sense to put the brake system on the front of the fork?

-ChaZ

Anton · 02-17-2006, 04:02 PM

Quote:

Originally posted by Xa3

But with the brake rotor counter-rotating, wouldn't it make sense to put the brake system on the front of the fork?

-ChaZ

If the brake had its choice it would be located at the top to the disk, in front of the fork. With more air flowing past it it would stay cooler. Trouble is, under hard cornering, the front rim, axle, and fork lowers all flex slightly, enough that when the caliper is mounted at the top of the disk, the brakes drag.

That what Cycle World told me anyway.

Xa3 · 02-17-2006, 04:05 PM

Quote:

Originally posted by Anton
If the brake had its choice it would be located at the top to the disk, in front of the fork. With more air flowing past it it would stay cooler. Trouble is, under hard cornering, the front rim, axle, and fork lowers all flex slightly, enough that when the caliper is mounted at the top of the disk, the brakes drag.

That what Cycle World told me anyway.

But what you just said is a reason why they don't put brakes in front FOR brake disc that doesn't counter-rotate.

So basically, you're saying having brake caliper in front of fork for counter-rotating brake disc would be a good idea?

-ChaZ

roger albert · 02-17-2006, 04:50 PM

In front is AWAY from the axis of rotation (steering stem) of the steering/fork assy, which is one of the main reasons they are behind now. In front greatly increases moment of inertia of said fork assy. To avoid an increase in propensity to oscillation (head shake, or in severe cases, the tank slapper) you then have to dial in more trail, and/or increased damping through other means (damper, bearing drag etc) That slows steering, and can make, in severe cases, weave more likely) Bad design. And this design will invariably have greatly increased for mass, so that last thing it needs is to move some of that mass ahead of the steering stem axis. That would be a double whammy. Sure wouldn't move the bike towards the stated design goal of non tank slapping (which I am nearly sure in an overstated/simplified premise anyway)

Moybin · 02-17-2006, 06:42 PM

It would be possible to dead-weight the rotors so that they had the same MOI as the wheel & tyre... End result would be ZERO gyroscopic effect = bike falls over. NO stabilization at ANY speed!

So it's just another engineered means to an end, in this case, how to build heavy wheels and make them act lighter. But as JRR noted, you have MORE overall mass to contend with.

I still think the right way to lighter wheels is a carbon fiber outer ring with individual carbon fiber spokes, just like a steel spoked wheel, but out of CF. THAT could be tested and proven safe, unlike the cast-as-one spoked CF wheels currently available.

PFFOG · 02-17-2006, 07:15 PM

Quote:

Originally posted by Moybin
It would be possible to dead-weight the rotors so that they had the same MOI as the wheel & tyre... End result would be ZERO gyroscopic effect = bike falls over. NO stabilization at ANY speed!

So it's just another engineered means to an end, in this case, how to build heavy wheels and make them act lighter. But as JRR noted, you have MORE overall mass to contend with.

I still think the right way to lighter wheels is a carbon fiber outer ring with individual carbon fiber spokes, just like a steel spoked wheel, but out of CF. THAT could be tested and proven safe, unlike the cast-as-one spoked CF wheels currently available.

BINGO!!!!