Mini-Project: Bike Dynamo

[cprobertson1]

I was bored at the weekend, and decided to make a (mechanically) resistive load for my trail bike - so I made a little A-frame that lifts the rear wheel off the ground, and loaded the wheel with knurled bit of PVC pipe - I'll rubberise it in the near future - which is connected to a fire risk felt pad for resistance. I'll replace it with something that is less likely to ignite that will wear down slower and not generate as much heat.

So, I've turned my regular bike into a poor man's exercise bike - excellent.

About five minutes ago I thought to myself: "Hey! Why don't you replace the resistive (mechanical) load with a dynamo and hook it up to a battery!"

I liked this idea so much that I'm going to do exactly that! But, I lack a dynamo: time to improvise!

Am I correct in thinking that I can just hook the spindle from a DC (or I guess AC) motor up to it and use that to generate some power?

Obviously, the power I get out of it will depend upon the rate that I turn it, the size of the motor, the number of windings etc etc - I take it I will have to restrict that power to whatever the motor was originally rated for (i.e if it's a 12V, 1A motor, can I apply rotation up to the point that it generates 12W?)

Finally, to charge up, say, a sealed lead-acid battery - take it I just need to regulate the voltage down to where I want and rectify it if required?

[Zucca]

Put the R in a water bucket to save energy when you need to cook pasta.
Rember bullpark about 2KW are professional legs (tour de france), PEAK!

Generally you want do deal with <<250 W normal training pace.

How much W generates your legs?

240W on 12 V battery are 20A, a little bit steep in my eyes.
An old washer motor could do the trick...

Also a USB charger could be handy if you want to run a tablet with

https://zwift.com/

[cprobertson1]

Good question! I haven't calculated my energy output I'm afraid - though there is about a 1:20 reduction between the dynamo and the tyre - i.e for every rotation of the wheel, the load-axle will do ~20 rotations - but torque will be limited due to the small axle. I can add in a belt/pulley and a second wheel for the dynamo though to reduce that ratio to where I can drive a dynamo!

Good shout with a washing machine motor - I'll visit the dump at the weekend and see if I can scrounge anything useful!

[NiHaoMike]

Try an ECM motor without the drive for a commonly available high voltage alternator.