Re: Re: Re: electronic valve action tuba.


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Posted by Rick Denney on June 26, 2000 at 14:54:01:

In Reply to: Re: Re: electronic valve action tuba. posted by Chuck on June 23, 2000 at 20:01:08:

Yes, it's been done with bicycle caliper brakes, but not as effectively as the price tag would suggest. The Magura hydraulic brakes were a huge improvement over conventional cantilever brakes, but the so-called V-brakes are just as good, much cheaper, and mechanically simpler.

Remember also that hydraulic calipers do nearly the opposite of what valve actuators would need to do. They take a large motion of the brake lever and reduce that to a relatively small motion of the brake pad. If you "wired" the hydraulics (or a cable system) to do the opposite (or nearly so), the effort would be much higher. The force required to actuate the system is always the force required to accelerate the valve, times the mechanical advantage of the system, times the loss due to friction. Current rotary valves have about a 1:1 mechanical advantage (that is--a half inch of spatula travel equals a half inch of stop-arm travel at the connector), compared to a 4:1 advantage for bicycle brakes. So, either the effort will be four times as high, or the return spring must be one fourth as stiff, to retain the same force. The friction will be about the same (tiny). An electro-mechanical system can reduce the force required at the button and make up the difference in eletrical energy.

Rick "Bike Geek" Denney


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