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Old 02-21-2012, 08:38 AM
datahar datahar is offline
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Default 125 or smaller conversion - Build started, pg3

I am about to start a conversion of a small motorcycle for my daily commute.

My base bike will be a 125 or smaller (currently got my eye on a honda h100)
I weigh 55kgs and my target range is 30miles. My commute has one hill that I see could be a problem, for 1/4 of a mile. Speed wise 60 would be nice, but will likely aim for 40mph. Lead acid batteries will be the batteries of choice, atleast to begin with.

I guess my question, (which is likely a very common and annoying one, so I apologise), is what sort of motor can I get away with for such a set up?

This is to be a budget bike, so I can save my fuel money to tackle a more financed build.
Ideally my motor budget would have been 100 (you can laugh don't worry)
I have been trawling ebay, but the only thing I have really found was only 620w Emoteq, which does not sound anywhere near the mark?

Aslong as I can (just) burn off a moped still I will be happy

Any suggestions / criticism would be appreciated

Many Thanks

Jimmy

Last edited by datahar; 03-03-2012 at 05:24 PM.
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  #2  
Old 02-21-2012, 12:58 PM
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frodus frodus is offline
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Default Re: 125 or smaller conversion

you'll need more of a budget for a motor. I'd suggest finding a forklift motor used somewhere (check forklift repair places, they might have one for cheap).

That's a small motorcycle so you won't need a huge motor to get 60mph, but with lead, the acceleration will be slow.
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Old 02-21-2012, 01:27 PM
datahar datahar is offline
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Default Re: 125 or smaller conversion

Thanks, I will keep a look out

spotted a newman 5hp single phase, AC would mean a design change a little but no biggie, just waiting back on it's V before I decide if it would be suitable.

I am right in thinking 5hp would suit my needs aren't I?
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Old 02-21-2012, 01:50 PM
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Default Re: 125 or smaller conversion

single phase AC motors won't work well. They have very low starting torque and I don't know of any single phase AC inverters widely available that can run off DC.

Get something made for an EV.
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Old 02-21-2012, 02:23 PM
datahar datahar is offline
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Default Re: 125 or smaller conversion

Right got it, stop being cheap
I will try and concentrate on prepping a bike and the batteries this month, keep motor money to one side and come back next month with double
That said there is a motor refurb spot in my town, will have to go have a word with them.

Thank you!
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Old 02-21-2012, 02:31 PM
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Default Re: 125 or smaller conversion

Absolutely go do that. Take your time and find a decent motor (DC is usually cheaper to start with). Look around for a series wound forklift or golf cart motor. With a golf cart motor, make sure it's not a female splined couple, it's a PITA to adapt to a motorcycle. Make sure it's got a shaft output.
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Old 02-21-2012, 04:41 PM
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Default Re: 125 or smaller conversion

Hi Jimmy
It's good to see someone local here. I definitely don't want to discourage you but getting 30 mile range won't be cheap unless you're good at scrounging for parts. I converted a Cagiva 125 a few years back using an Etek motor and lead acid batteries. I wanted to keep things as light as possible, i.e. no heavier than the original bike, and ended up with 15 miles range. The batteries died within a year because I was often discharging them close to their maximum capacity. To get 30 miles from lead acid you need to add a lot of weight in batteries, which makes the bike heavy and increases your torque requirements. It's a vicious cycle.
If you really need 30 miles range I'd suggest going as lightweight as possible to minimise motor and battery requirements and start looking at lithium batteries, which are about a quarter the weight of lead, but likely to be a good deal more expensive. The alternative, if you can find cheap lead acid batteries and a second-hand series wound motor, as Frodus suggested, is to look for a heavier bike capable of carrying a minimum of six 60Ah batteries, which obviously means a much heavier finished bike.

Malcolm
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Old 02-21-2012, 05:35 PM
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Default Re: 125 or smaller conversion

Hi Malcolm

wow that IS a staggering figure, here was me hoping 30miles was going to be easily achievable
My actual commute is 20miles almost exactly

A shame to hear the suggestion of a larger bike, I think I have just secured a 125 for pocket money
I will wing it I suppose, get the bike, find a motor then figure out what's going to be the best way to power the thing.
Controller I will be doing DIY along with a full replace of the bikes loom

Is there an obligation to keep the mechanical speed and odometer?
I was considering hacking up a sat nav to be my instrument panel and also keep sat nav mode functionality (another drain on the power ), though this luxury would come later on, I don't plan on getting lost on way to work.

Seeing as cheap and cheerful as a starting project doesn't seem possible, I guess I will have to keep dependant on the ICE for a little while longer and get this done properly.

Also one local man to another, would you recommend any sources that are UK friendly to find a suitable motor?

Thank you
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Old 02-21-2012, 05:48 PM
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Default Re: 125 or smaller conversion

Yeah, lead is not very power dense. I'll be getting a max of 40-50miles with my 5kwh pack of lithium, but I doubt you can fit over 2kwh of lead on that bike without it being super heavy. For 30 miles on a somewhat light motorcycle you'd need somewhere around 3kwh (100Wh/mile, 30 miles, 3kwh, from the batteries). Lead can put out maybe 75% of it's energy under load due to peukert effect + not being able to discharge completely without ruining them. That would mean you'd need close to 4kwh+ of lead acid batteries. Not small, and by the time you buy them, and replace them in 2-3 years, you could just save and get a ~3kwh lithium pack.

DIY controller? Do you have a background in power electronics? I don't suggest trying to do it on your own unless there's a kit you have in mind, it's far cheaper and easier to get an alltrax or curtis or something similar used. You'll spend more time, more money and more frustration building and designing one yourself.

To make it legal, there may be a requirement to keep the odometer with your department of motor vehicles (or uk equivalent). Check the regulations in your area.
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Old 02-22-2012, 05:15 AM
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Default Re: 125 or smaller conversion

If you're keen to keep the weight down and good at hacking stuff, I'd suggest looking at the brushless DC motors originally developed for RC applications. They're tiny and relatively cheap. The control side can be difficult, as the existing controllers have trouble running these motors at low rpm/high torque, but a number of people are working on it. Here's one project on Elmoto: http://www.elmoto.net/showthread.php...250-Conversion.

I've not found any good, cheap supplier of motors in the UK. Mine have all been ebay finds. The classified sections of the forums can also be a good source. If you have a fork lift breakers yard or motor rewinders nearby they can be worth checking out for series-wound motors, but these are heavy motors, 25-30 kg upwards.

There's no need to retain the mechanical speedo and odometer for the MOT. I just used a Cycle Analyst, which combines speedo and battery charge meter.
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