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Dave B
Joined: 10 Jan 2004
Posts: 4511
Location: Pittsburgh, PA3/21/13 8:56 AM |
Dyno Brake
Today's (3/21) Bike Rumors site has a piece on a combined generator/disc brake unit where magnets are built into the brake rotor and a induction pickup coil is in the caliper. It generates electricty while riding like a dyno hub.
The unit they describe is a design exercise and includes lights in the brake levers, etc but could be used like a regular dyno hub to run any lights, recharge smart phones, etc. Comments?
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Andy M-S
Joined: 11 Jan 2004
Posts: 3377
Location: Hamden (greater New Haven) CT3/21/13 9:25 AM |
Hmmm
I thought about something like this a while ago, but IIRC, someone else (Mark?) pointed out that it would take some powerful magnets and heavy-duty windings to make this work effectively.
Think about it. A conventional hub dyno puts out on the order of 3-6 Watts or so. Shorting across it does cause a free-spinning wheel to come to a halt pretty quickly, but add 200# of bike and rider (and let's not forget a battery to store all that extra energy), and you have a lot more energy to deal with. Of course I haven't seen the article, and if the caliper is mechanical
in addition to
electrical, it might work a bit better.
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Andy M-S
Joined: 11 Jan 2004
Posts: 3377
Location: Hamden (greater New Haven) CT3/21/13 9:34 AM |
Ah.
Went and looked. These are two distinct systems, and the dyno has nothing to do with the braking function. D'oh.
My only complaint with the system is that the rotor is likely to be on the costly side...that and the fact that heat can damage magnets, so unless they're well-insulated from the braking surface, there could be an issue with light fade as well as brake fade.
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Dave B
Joined: 10 Jan 2004
Posts: 4511
Location: Pittsburgh, PA3/21/13 9:51 AM |
Yeah
Right, the dyno function has nothing to do with the braking function, it just, uh, goes along for the ride. I wonder if they could incorporate regenerative braking as a drag brake for long downhills to reduce the load on the pads.
I was also wondering if the heat buildup would damage the magnets and the article said nothing about that potential problem. as to cost, i expect it wouldn't be any more expensive than the total of a set of disc brakes plus a separate dyno hub, and perhaps a bit less.
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KerryIrons
Joined: 12 Jan 2004
Posts: 3236
Location: Midland, MI3/21/13 7:21 PM |
Regnerative braking
if you're descending/coasting at 30 mph gravity is "giving" you about 500 watts. If you had a regenerative braking system that burned up 50 watts it would slow you a little more than 1 mph. And where would that energy go? That is certainly way more than your battery charger needs.
You'd have to either have a big heat sink or some big batteries (or maybe a big cooling fin) to get any functionality at all from a regenerative brake on a bike.
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