What motor/controller for a montague paratrooper?

[arcticfly]

Hi guys!

Thinking of building a Montague folding bike for easy transportation. I get my speed fix with my Stealth Bomber @ 10.000 watts peak, and my commuting needs are met with my Merida with a MAC 8t @ 50V.

So this build is all about getting a stealthy most miles per AH kind of thing. I will use this to get into the mountains using closed roads that are open to biking. I will bring it on trains so lightness is important and torque is more important than speed.

What motor should I choose that is smallest possible, 10-12t, 48-50V, max 1500-1800W and most important are very durable? Should I get another MAC? or Bafang BPM2? Or is there anything smaller?

Is the small bms sinewave controllers any good?

In short: What to get for a lightweight durable bike?

edit: Oh yeah I forgot, motor needs to be ok to pedal if I run out og battery in the mountains, so i guess it needs to be geared.

 

[mlt34]

You are definitely looking at geared, and so your main options are mac or bafang, like you said. Probably one of the slower speed versions to fit your needs better.

For either of those I would NOT use one of the little 6fet BMSbattery controllers. They would likely work for a while, but you'll blow the fets when you need it most going up a big hill pulling full power. I've used their KU93 controller with a Bafang BPM and it works great. I assume you're going rear motor, right? Front would be fairly torquey, so you'd need a good torque arm.

If you don't mind taking a small torque hit, even a Q100 motor, or perhaps dual Q100 motors could be great @48V, especially if you're planning to pedal along with it. SUPER stealthy and small, just great little motors. If you really want the torque though, those motors will leave you a little disappointed.

Where do you plan to put the battery? I like that frame and want to do a conversion on it, but without the main triangle, I feel pretty limited by battery placement. I'd probably modify a triangle bag to hang under the top tube (only tube?) and put it there, that way I don't have to put it over the rear wheel on a rack.

Good luck, keep us posted.

 

[PRW]

have a look at the duty cycle, very neat battery solution....
http://endless-sphere.com/forums/viewtopic.php?f=3&t=51612

 

[mlt34]

have a look at the duty cycle, very neat battery solution....
http://endless-sphere.com/forums/viewtopic.php?f=3&t=51612

I think I just got a little bit aroused by that battery box

Very nice. That's sort of what I meant by my triangle battery bag idea above, but obviously that's done in a much more professional way. Kudos to him.

 

[arcticfly]

Dual motors could be an option I suppose, but it is so much easier with one on the back. Is bafang less durable than a Mac?

Regarding battery placement I was thinking maybe Cellmans bottle battery mounted like this:

But seeing the link above, that looked absolutely awesome. But then I have to build a battery my self...

 

[mlt34]

Cellman's battery like that would do it, and would keep the battery real low which is great for CG.

Are you against the battery bag option from the top tube? That way you don't have to build anything custom, other than maybe lengthening the straps for the top tube, and you could go with a cheaper heat shrink battery instead of a hardcase battery. Or use RC lipo if you're into that.

I think the Mac, BMC and Bafang are all sort of on the same level for reliability. They're all good motors.

 

[arcticfly]

Not against triangle bag at all, and if I could get a slim battery like the duty bike, I would be all for that. But full size triangle batteries is much larger I guess. Not sure how that would fit. I will have to investigate. I´m really keen to copy the duty bike. Not sure on the dual motor part, but if 2x q100 is pulling better than one Mac 10t It could be interesting.

 

[Ykick]

Folding and mixed mode commuting I would probably go Bafang crank drive. Battery can be pretty small and easier to mount in many locations.

 

[arcticfly]

They do seem to be nice, but 750W? Sounds like lots of pedalling. I will usually bring about 20 kg of photo equipment on my trips into the mountain, so is 750W enough I wonder...

 

[Ykick]

750W through the bike gearing is very significant and efficient.