# custom electric sport bike



## monkeywraith (Feb 19, 2009)

i am looking at building a custom sport bike for commuting, so i need minimum 45mph, hopefully at least 70, and at least 40 miles on a charge. http://www.robotmarketplace.com/products/EMS-PMG132.html is the motor i was thinking about, though it is a tad expensive. i will likely go with l-ion or li-poly batteries, but not sure how many specifically. i want to stick with 72 volts for this motor for the speed, otherwise it will depend on the motor. aside from the motor, i would like to add other electronics as well, lights and a hud and such. also, i am tempted to custom build the entire thing out of carbon fiber for more freedom in design, though i may just get a chassis and make a few parts, possibly partially enclose it for aerodynamics.

with all of this in mind, i have a few questions. first and foremost, since i would like to start thinking about the body, any reason not to use carbon fiber on any particular part? i found sheets 50" wide for $51.50 a yard for .03" thick twill weave. the site says it is mainly for structural reinforcement, so i figure with 3 layers or so plus filler material it should be fine for the body, but i have also never done anything with carbon yet. second question, how difficult do you think it would be to add (if i build it out of carbon) or keep (if i use an old chassis) the 6 gear manual transmission? or would it even be helpful? can not think of any other questions at the moment, but any thoughts or suggestions are welcome, especially any suggestions on batteries or alternate motors and other components.


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## monkeywraith (Feb 19, 2009)

oh, oops ... mechanically i am not terribly experienced, but i am a genius and a quick learner  ... i would rather do this in under $2000 but i may end up having to hit 3, hopefully not 4 ... though i will end up trying to sell it in about 3 years anyway (unless i manage to ship the thing to japan, but it would probably be more cost effective to just strap a motor to a regular bike when i get there)


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## frodus (Apr 12, 2008)

Are you going to build this bike from the ground up? I'd recomend starting with a frame based on a decent bike, and do some custom fairings if you want a custom look. 

I doubt you'd need a transmission with that motor... the power band is wider than an ICE. Another thing is, that HP is HP, no matter the gearing..... if the motor doesn't have enough oooomphhhh to get to 70mph, then its just not gonna do it in 4th gear.

TORQUE however can be geared and is important for acceleration. The best thing to do is calculate your speed requirements. If your speed is too high the torque will be too low and you'll accelerate like poo.

$2000 is gonna be a tad on the low side for a motorcycle/perm132/controller/contactor/cables/DC-DC converter/charger and batteries. (I must note that all lipo are li-ion, just like humans are mammals.... lifepo4 is li-ion as well) Lipo are dangerous if overdischarged or overcharged. They're responsible for laptop fires and would prove to be dangerous in a vehicle. I'd recomend sticking with Lead if your budget is low. If you can afford a little more, go with lifepo4, but realize, you need a BMS system and special charger.


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## lorraine (Feb 11, 2009)

Hi,Travis Gintz,
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Lorain




frodus said:


> Are you going to build this bike from the ground up? I'd recomend starting with a frame based on a decent bike, and do some custom fairings if you want a custom look.
> 
> I doubt you'd need a transmission with that motor... the power band is wider than an ICE. Another thing is, that HP is HP, no matter the gearing..... if the motor doesn't have enough oooomphhhh to get to 70mph, then its just not gonna do it in 4th gear.
> 
> ...


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## major (Apr 4, 2008)

monkeywraith said:


> suggestions on batteries or alternate motors and other components.


Hi monkey,

I suggest you go with a wound field motor. Those PMs look good for package and specs, but don't tolerate overload well and often have durability problems. Try to find somebody that is pleased with that PM motor in an application like yours. 

Regards,

major


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## frodus (Apr 12, 2008)

major said:


> Hi monkey,
> 
> I suggest you go with a wound field motor. Those PMs look good for package and specs, but don't tolerate overload well and often have durability problems. Try to find somebody that is pleased with that PM motor in an application like yours.
> 
> ...


www.jozzbikes.co.uk

lithium aprillia, and he's building a ducati... elthough the ducati has 2 motors, they're PM motors. Agni are very good motors...

I like my series wound motor though.....


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## mattW (Sep 14, 2007)

Yeah almost all the TTXGP (isle of Man emission free GP) entries I have seen are using twin Agni motors, they have an awesome power to weight ratio and can handle much higher rpm than my mars 0709. They are a bit pricier but that would be what i'd be saving for if i hadn't already bought mine.


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