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Discussion Starter #1
Hi all, just joined up as I'm attempting to put together a EV bike to take to work every day (as opposed to the two and a half tonne 4WD I currently use) and this forum looks like a great resource and place to start:)

No specific questions yet - just thought I'd introduce myself and my project. If anyone has any hints tips or suggestions, I'd be very appreciative. The bike would need to travel 23 km (15 miles) each way and I'd like to do it in around 1/2 an hour to 40 minutes. The route I'd take is well serviced with bicycle tracks and charging would be available at both work and home. Also, I've decided to go with a hub design (to keep it simple) and take the slight efficiency hit. I've set myself a budget of $1000 (AUS)

Anyway, that’s all from me for now - take it easy all
 

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Discussion Starter #3
Hi Coley. In answer to your query, I have and unfortunately the current spate of nanny state laws we have had thrust upon us over here has been extended to the realm of EV Bikes - a poultry 200 W (1/4 hp) is all that is allowed to protect us from ourselves...:(

With that constraint in mind, a 30 to 40 minute commute over 23 km becomes a bit of a design challenge, hence the reason for joining...

Take it easy and thanks for the reply...
 

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Hi Punk

You need to average 23mph (40 minutes)
A fit bugger (not me) would do that on a straight push bike!

An unfit guy can do about 50 watts which gives about 18 mph, 200 watts should easily achieve 25 - 30 mph

This is assuming a motorized bicycle - not an electric motorbike!

The more it looks like a bike - and you keep pedaling - the less likely you are to be pulled over!
 

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Discussion Starter #5
Hi Duncan - thanks for the reply.

Once upon a time I could have generated 200 watts - but not these days!!!

I'm in about the same boat as you, I could probably maintain 50 watts, however combined with an additional 200 watts from the motor, I'd only make that out to be around 30 km/h (~20mph), based on some fairly basic calculations and what the stated performance of similarly powered bikes on the net are achieving.

Still, I've never actually built one and I hope the assumptions you've made for your estimation are more accurate than mine!!!

Cheers...
 

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Hi Punk

I used to cycle at 20 mph - and I could keep up 17 mph for 50 miles and I am not a fit guy!

I will have a look at my Bicycling Science book tonight but I an fairly sure 200 watts is close to 30 mph

You are allowed a 200 watt motor -hmmm

My car (not yet complete) has a 10Kw motor - I am expecting to be getting more than four times that

A bike with a 12 volt 200 watt motor is probably geared to run out of speed - so the top speed may only represent 100 watts

I would be thinking about a 12 volt 200 watt motor (yes officer it says 200 watts) at a slightly higher voltage, 24 volts? and keep an eye on the temperature

You can think of a electric motor as a device that turns current into torque, as the revs rise back EMF increases so the current reduces as does the torque
You can start with a higher voltage - which depending on your controller- may give a higher current but which should enable you to produce the torque at higher revs
 
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