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when the eddy brake inevitably fails
How's this going? I had a quick look at eddy current braking as a way of adding drag to rollers, but it seemed like I'd need a huge magnet to do anything useful if the the brake rotor was only travelling as fast as the road speed (as would be the case for the surface of a roller). Magnetically braked "turbo" trainers have the periphery of the brake going at about 2-3 times the road speed, and nobody cares how heavy the rotor is so you can have 2kg of magnets spinning next to a stationary rotor/heat sink. With a hub mounted rotor of normal size, the peripheral speed is only about ¼-⅓ of the road speed. IIRC drag on an eddy current brake is proportional to velocity, so the power dissipation would be proportional to the square of velocity. With only 1/6 to 1/12 of the velocity on your tandem compared with a mag turbo, I'm sure you can see where this is going.
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gbj_tester
@deleted
Tubes have been ordered and this is getting started THIS MONTH after 5 months of chat. Below is the pretty much finalised geo however I'm not sure the cad programme could handle the rocker dropouts so the seat stays will join higher up the dropout giving one continuous top tube line. Matt's also managed to find some black 40H Mavic ceramic rims (for a rim brake when the eddy brake inevitably fails :)) so I'm pretty stoked about that.