Need more power - Will my cunning plan work?

[tallbloke]

Hi all,

It's a long time since I visited so I should re-introduce myself. My name is Rog and I built my first pedelec in 2006 after I was left in a tree with a broken spine by a hit and run driver. I'm 6' 8" and 15 stone and 250W doesn't get me up hills where I live in Yorkshire.

So I built my own using an american kit with a 450W motor. Which was ok but still struggled on inclines. So I'm thinking of going the Single Vehicle Approval route and building something with a bit more oomph.

Being insured and wearing a helmet is a good plan anyway, with so many numpty drivers about, so having accepted that, I'm realising that there is quite a lot of scope for MORE POWER.

I've been considering the best way to do this. More power means a lot more battery weight, and limited range, so I'm considering a novel solution.

One of the things I really like about pedelecs is that they are QUIET. But one of the things I really hate about pedelecs is BATTERY FAILURE. So here's my plan. I'm here to find out what the flaws are.

1) Get a sturdy bike with biggish tyre sections.
2) Attach my 750W motor to my ebay found worm drive gearbox (from an automatic car wash system)
3) Attach this assembly firmly to the bike frame
3) Run a chain from the gearbox output shaft to the inner chain wheel of the 10 speed bike.
4) Attach a throttle and wire in a hefty controller
5) Mount a 1KW 50cc silent generator on the back rack and run DC to the motor via the controller and throttle.
6) Pour in a pint of petrol and go for a nice long ride

So, feasible, or not? Over to you.

 

[oigoi]

I think this would work, looking at some of the machines people build on the endless sphere forum. I am also interested in the idea of a bike with more power that has been through the sva process. I think its now called iva for some reason, though flecc does know more about it, there's different categories of vehicle depending on their power / speed capabilities.

The main limitation in your design is the amount of power you will be putting through the bike's chain by driving the front chainwheel. Your chains might not last very long. You might be better off using a disc type rear hub (but having a rear rim brake) and bolting a sprocket onto the disc mounting holes on the rear hub and driving the rear hub directly

 

[flecc]

There is a low speed moped class which is intended for e-bikes with more power, i.e. bicycle based but with motor up to 1000 watts. The 16 mph assist limit still applies to this class and to get approval for a home build you will need Single Vehicle Type Approval (SVA). The IVA name variation hasn't reached two wheelers yet. It would be best to check with the nearest Vehicle Inspectorate location (VOSA) precisely what they require the bike to have in the way of extras, for example stop light, lighting, indicators, mirror and you will need a rear number plate mounting and licence holder.

The hybrid petrol electric nature means you will lose the free "road tax" (VED) benefit so that will cost you £16 a year currently. Again it's worth getting the inspectorate opinion on your petrol proposal, since it could greatly complicate getting approval, such things as petrol tank safety etc intruding, especially in a combined petrol-electric situation.

All the contact details are in this thread that I posted some while ago.
.

 

[eddieo]

OR buy a german S class 45kph bike that comes with a certificate of conformity and should be easier to register...but if you want a project, go for it!lol.There is an old boy on the site I am on down in Spain who rides around on a petrol push bike, they are legal here, has had it years and cost him £130

 

[tallbloke]

Thanks for the replies everyone. For a while I had a 1950's mobylette with a cute little direct drive 50cc motor. It was a pain having to stall and pedal start it at every set of lights though.

The quietness quotient is what I'm after, or I'd just buy a small motorcycle. I wonder if anything neat could be done with a catalytic gas heater and one of the stirling engines out of E-ons clever combined heat and power combi boiler. They make a kilowatt.

I guess that might take a while to get through an SVA though...

I'll keep thinking,

 

[flecc]

Stirling engines aren't very efficient so that could be expensive to run. Anyway I think the Vehicle Inspectorate would have a fit!