Electric Bike v1.0

Background

This is the first step towards a low power transport vehicle.
A guess is that the average bicyclist delivers 150W of energy.
So I use a 200W 12V Radiator fan. rpm @ optimal load > 2500.
First I thought about using chains, but Simon suggested wheel to wheel.
Let's try to run 30 km/h: 30 km/h / 3.6 = 8.33 m/s
2500 rpm / 60 = 42 rps
8.33 m/s / 42 rps = 0.2 m circumference should the white-red wheel have.
0.2 / Pi = 6.3 cm in diametre.
I guessed maby the motor will turn much slower under load?
And I found a high friction rubber wheel with a diametre of 10 cm.
(10 cm equals 47 km/h, and later tests revealed it was a little to large)

A 60 Ah car-battery might give upp to 60*12/200 = 3.6 h of power cruising :-)

Construction

Cut the 10 cm wheel to fit the engine. Made a hinge on the aft-side of the engine, and a long iron-stick on the other side, to allow the driver to control the friction.
Taped the battery to the parcel carrier :-).

First ride

To my and Fredrik's big surprise, it started right of from standstill, when we connected the wires and I pushed down on the lever. I picked up more speed by every second, untill I was riding at between 20 to 30 km/h. (a guess). Pretty Cool! I took it for a spin around the block :-)

After first ride

As you can see, the 10 cm rubber-wheel shows severe wear. I think this happened before take-off, spinning against the frame. I think making a mechanical stop, that makes it impossible to lathe it against the frame, and let the engine turn at "to low" rpm's during takeoff will solve this.
The wires got hot, have to get thicker ones

Thoughts for the Future

It is certainly possible to make good vehicles with similar technology. I'd like to run this in a streamliner-body. There is much much better engines out there, we have brushless RC-plane engines which can deliver a lot of power e.g. 300, 500, 600, 1000, 2000 W. They typically have 80% efficiency, and one claims 93%. If we make our own controller, we can motor-brake and use the energy to recharge the battery. Gearbox / chains is the way to go. Whatever that has the least amount of losses.

Project Cost
Bicyckle	1400 SEK
Engine	300 SEK!
60Ah Battery	150 SEK!
10cm wheel	15 SEK
Cable	30 SEK
Tape	20 SEK
Sum: 1915 SEK (about 275 USD)

How good is this?

Energy in a car-battery: 60 Ah * 12V = 720 Wh
Typical long jorney = 500km. 500km/20km/h = 25h traveltime
720/25 = 28.8 W for each car-battery if we travel at 20km/h.

Will we benefit from adding this system?

Engine package Systemweight
Battery (a guess) 22kg
Engine (guess) 8kg
Sum 30kg/28.8W
Contribution: 1W/kg on the trip above.

Human + Bicyckle 80 + 20 = 100 kg
Output: 150-200W
Contribution: 1.5 - 2 W/kg

The system adds very little air resistance.

Can we build a bike that travels at 20km/h at 30W? or 60W?
How much weight can our wheels sustain?
60 km/h at 90, 180, 270 or 360 Watt? (1-4 batteries)

After this we clearly see a new design goal:
Carry a lot of weight

Low air resistance
Low rolling resistance

An streamliner with good wheels

Last modified: Wed Jun 21 03:04:08 W. Europe Daylight Time 2006