Modifying Store bought E Bike R Martin 12a

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georgefromvt   1 kW

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Modifying Store bought E Bike R Martin 12a

Post by georgefromvt » Jul 04 2010 10:14pm

Recently I purchased a R Martin 12 a. Very nice bike. Excellent quality but I want more torque. Thinking of putting a 250 W brushless motor on the front,independent of the bikes controller and battery, the added on motor hub would have it's own controller/battery. Anyone out there modify a store bought e bike? Also anyone have experience with this brand: V Power? My bike is powered by a 36 V Lipoly battery, might just upgrade the battery to a 48 V. Any suggestions? I really like my new bike but want more torque. Thanks. ... 4aa24236ed ... cycle.html
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jondoh   1 kW

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Re: Modifying Store bought E Bike R Martin 12a

Post by jondoh » Jul 04 2010 11:55pm

Hi George,

I think just about everyone on these boards were once where you are at now:
"... yeah the bike is nice but i want more power..."

Just a word about your bike. I see it has front shocks. Normally a front hub motor is not recommended for forks with shocks because the material is usually some kind of aluminum alloy. The issue is that aluminum doesn't give like steel and if it breaks, it will without any warning. Steel will bend first-- not only that but I had some cheap steel forks that made a creaking noise as the dropouts got spread out. I've heard that high quality forks will withstand front hubs without problems but still, if they break, it will happen fast and not gradually like steel.

Before anyone can recommend a motor, voltage, etc, one would have to know what kind of performance you're looking for. How fast do you want to go? What is your weight? What grade of hill do you need to climb?

My feeling is that 48v with the typical hub motor will give you a pretty good boost. The main issue is the battery. I suspect that your R12 performs the way that it does to keep the amps down which will allow your battery to last longer. It seems to me that in order to get any kind of performance from a hub motor, you will draw between 25 and 30+ amps during hard acceleration. For a cheaper or smaller lithium battery that's 3C+ which is hard do do over the long haul.

If you are going to go with a hub motor, you might as well just go with a new, used mountain bike from craig'slist for $50 and keep the R12 as a 2nd bike (truth is, most of us have more than one electric bike anyway). Start saving your money for a nice lithium battery.
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alswiseowl   100 W

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Re: Modifying Store bought E Bike R Martin 12a

Post by alswiseowl » Jul 05 2010 3:41am

HI George..

i agree with jondo
if you want more torque,with decent topspeed and range aswell..
probably go for either a goldenmotor1000watt hbs motor,or a ninecontinent motor,with a lyen 9fet or 12fet controller..
with either some lipo,but if you new to it,get the 48v 15ah-20ah headway cells battery pack...

running either motor with 48v and 40amps=1920watts thru the controller should be sweet i think..

funny tough the r10martin is suppose to be built for torque,but i didnt think to much with 250watts
have you tried adding another 12v thru it?

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liveforphysics   100 GW

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Re: Modifying Store bought E Bike R Martin 12a

Post by liveforphysics » Jul 05 2010 4:14am

If the motor and controller aren't getting excessively hot with the way it is now, just slather some solder over the current measurent shunt in the controller, and enjoy the extra power. While you're inside the controller, take a look at the FET type and cap voltage rating, and if it's all good to 50v, add a 12v pack in series with your 24v pack to give a 36v setup.

If your current motor isn't over-heating, then there is no reason at all to add another motor, just feed the one you've got more power, which is easy-peasy to do.
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LI-ghtcycle   1.21 GW

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Re: Modifying Store bought E Bike R Martin 12a

Post by LI-ghtcycle » Jul 05 2010 8:39pm

I like both ideas, but one thing I wanted to mention, if you DID go with a separate motor, controller, battery for the front wheel, where are you going to put all this stuff first off, and do you really want to have to worry about getting them to work in sync? If one is more powerful than the other one with be slowed or bogged down while the other is fighting it, and neither motor will be happy.

I think I would just try modifying what I had like LFP suggested first, but if your not comfortable modifying the controller, do the craigs list bike with a different kit.

Remember it's almost always easier, cheaper and more fun if you buy something designed to do the speed/power you want than taking something less powerful and make it perform more.

When I used to ride a 500cc motorcycle, I had dreams of taking my 50 HP bike and turning it into a sleeper that might give a 750cc bike a run for it's money on the track/red green lights.

THEN I learned about a guy who had done just that, he was pushing nearly 80HP out of the little 500cc twin I had! :D I was excited until I learned it ONLY cost him $11,000 to have the motor built that way and that he expected to have to rebuild the motor after a week of racing. :shock:

He could have had the same results if he just had bought a larger motorcycle for half the money. (granted this was racing, and he wanted to stay in the 500cc class :wink: I was just looking to have more power than the average guy when the light turned green at a stop light :twisted: )

I'd suggest that if you want 48v 750W + performance, get a kit/bike designed for it rather than pushing something smaller too hard.

This is coming from a guy who over-volts his current bike, but I have lots of information on my particular motor, and know that it has been successfully pushed much harder than I will, so don't get me wrong, I'm not against pushing it beyond the "factory" limits. :)
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georgefromvt   1 kW

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Re: Modifying Store bought E Bike R Martin 12a

Post by georgefromvt » Jul 05 2010 9:38pm

My idea was to use the new brushless hub for the front wheel, activated by the throttle. And use the original pedelc for the main, original motor. The added brushless hub is free wheeling so would only use it for additional torq and speed when necessary. I have a spare 37 v 10 amp LI battery from my old EBIKEKIT sitting around. ... 4aa24236ed
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dnmun   100 GW

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Re: Modifying Store bought E Bike R Martin 12a

Post by dnmun » Jul 06 2010 2:31am

you have an motor and battery and controller? and you are still pedelecing? this is hard to comprehend.

if you still pedelec out of concerns for the law then the extra motor would put you over the limit, no matter what, along with overweight and overcomplicated.

luke speaks from knowledge of the force. use his wisdom. buy a big controller and can the pedelec. go to 48V if you can and see how hot the motor gets on your runs.

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