magneic braking for bicycle 1

[xsloth]

hi all,

I need a device similar to that found on exercise bikes that applies torque to the wheel to create resistance for the user. I believe the device is a magnetic brake of some type. Some use the trademark 'MAGNTEC'. I just can't seem to locate the device anywhere.

Any ideas?

thanks
-lp

 

[Lewish]

It is most properly called an eddy brake. Do a search on that description. Lots of info available.

 

[busbar]

A ~1/3HP capstan-coupled PMDC motor and incandescent lamps work well. [Hot doggers have burned out series pairs of 150W lamps in 30 seconds.]

 

[gcaudill]

I think you will want a magnetic partical brake (clutch) vs. an eddy current brake (clutch) due to the fact that the torque is mostly independant of speed.

 

[andrewg85]

You could use an electric motor strapped to the back wheel with the appropriately rated variable load connected to the terminals. They serve as both motors and generators so that should work without any problem. Could also use some truck batteries to power the motor and disconnect the variable load when you want to get around on the quick and cheap
Andrew

 

[jbartos]

Suggestion: An electromagnet aligned with the wheel brake disc might be the solution. A proper control of the electromagnetic force on the brake disc is necessary.
Please, notice that the non-abrasive braking has been applied to light rail vehicles in Europe for more than 40 years. The abrasive braking principle might also be used. The most of rail vehicles in USA are still using it. It produces slip-slides, sqeeeeaking noises, etc.

 

[TwnB]

I am an engineer who designs exercise equipment in Taiwan (I am an American). Lewish was correct in pointing out that the eddt current brake is most often as a resistance mechanism. I would not suggest a particle brake as it takes too much current to operate. jbartos had an interesting idea using the disk with an electromagnet. This would basically be an eddy current brake as long as the disk is either aluminum or copper. I would use permanent magnets in the disk application and mechanically move them closer or further away from the disk to change resistance. A bicycle brake cable works for this. I would not use an electromagnet because of current considerations.

 

[jbartos]

Suggestion: The electromagnetic braking system would have to be designed as an autonomous system. It means that the electrical energy (current, voltage, time) would have to be produced from the bicycle dynamics and applied to the electromagnetic breaking system, not based on the Eddy Current braking principle, but magnetic North-South pole force principle (which is used for non-abrasive light-rail vehicle braking, as well as in magnetically levitated trains in China and at Airport magnetically levitated transportation).

 

[rodar]

Investigate the construction of a "Faraday Generator"
Just a conducting disk with magnets on each side.
Its true the torque required to pedal will not be linear
with speed. But it seems to me this would be a good thing.
As you pedel faster it gets progressively harder to pedal.
If you use electromagnets a current control could be
mounted on the handlebars to allow user to tailor the resistance.
Rodar

 

[jbartos]

Suggestion: Visit

http://www.phys.ufl.edu/demo/mainlist.html

for: Eddy Brake 1 and Eddy Brake 2
Apparently, this is what is mentioned in gcaudill (Electrical) Apr 3, 2003 posting.

http://www.usc.edu/CSSF/History/2002/Projects/J02.pdf

for Anthony Y. Chong Project J0208 Electromagnetic Brakes