The first post in a series of posts on the different bicycles and their stages.
Bicycle #1 stage 1 was based on a BH Fitness ZTX exercise bike:
- removed the plastic covers, electrics that controlled the settings and the display,
- also removed the magnet to make sure that that doesn't cause any resistance
- 120W electric motor from ebay (24V, 3500 rpm, 66% efficient)
- very important to have a saddle you like: Brooks B66 saddle (
http://www.brookssaddles.com/en/Shop_ProductPage.aspx?cat=saddles+-+city+%26+heavy+duty&prod=B66)
- 80-90 revs gives approx 24V, the MPPT solar charger converts that to 5A @ 14V
- i'd prefer 60-70 revs, so 80-90 is hard work
- the motor would get quite hot after a couple of minutes so had to put a 0.84W, 12V fan on it
- to drive the motor i attached a wooden disk to the flywheel and screwed on a gear from one of my old bread making machines
- the belt from the bread machine also fitted the motor!
- not sure how long the plastic gear and tiny belt will last, have one more spare bread machine...
The combination of the high revs and the low energy output got me thinking of what i had to change.
So on to stage 2 with a new motor: 240W electric motor (MY1016, 24V, 2650 rpm, 75% efficient). The larger motor uses a different gear so i couldn't just swap the motors over. So got a new belt which ran directly on the flywheel, the benefit was a much better ratio. So finally more power at lower revs!
But it didn't work out that way: the belt was on pretty tight but still slipping a little bit, so after a couple of minutes the belt got warmer and larger and started slipping a lot. Makes sense: the outside of flywheel is a flat copper strip.
So i switched back to the first stage motor and built bicycle #2.
Status: no longer operational even though the gear and belt survived of stage 1 survived!
A couple of images of the bicycle in stage 2. Also shows the wooden disk with the bolted on gear for the stage 1 motor.