Motor upgrade suggestions (more speed needed)

[mcstar]

I'm looking to upgrade to a faster motor. My setup is currently a 26" mountain bike with a WE-BL motor. It's running the stock motor controller but it's been modified to put out about 38amps (instead of the original 20). I've got 16 BMI LiFePo4 cells in series giving me a little more than 50V at the terminals. I'm currently able to cruise at 27-32mph, but I want to go at least 37-40. I'd like to keep everything the same except the motor. At 27mph on the flats with no pedelling, I'm pulling about 550watts. I believe that what I need is a motor that's pulling about 1200 watts at 27mph, that should get me enough power to accelerate to > 35mph. Does anyone here know what motor I should buy? I've looked at the Crystalite 404 or 405 both of which seem to have power curves that would get me there, but they only come in 16" rims???? Is this true? Who else has a faster bike on 26" rims? What motor do you use? If you're going to say "add more batteries", please don't bother. I know I've go more head room in the power department from the pack I've got. I just want a motor that can go faster at the same voltage.

 

[jondoh]

you can put a 40x series crystalyte on any size rim you want if you know how to do it. i don't but my bike mechanic Chuck knows.

but it seems to me the better way to eek out a few more mph would be to bump up the voltage to 72 v.

 

[mcstar]

I've already got > 20lbs of LiFePo4 batteries on board. These cells are made to dump current. I don't want more bulk to carry around. The batteries I have can put out 100++ amps, but at 27mph with the current motor, I'm only using about 10amps. Plus, for the commute I've got, I only really use about 50% of the pack's capacity, thus I really do have a lot of head room on the existing battery pack. What I really need is a motor that can draw more power at 48volts to maximize the utility of my current setup.

I suppose I could buy one of the 16" 404's from ebikes-CA and then restring it. Does anyone know how to determine what size spokes to buy?

 

[ZapPat]

You could keep your motor and just change it's windings from a Wye to a Delta connection, like DocBass is going to do, but without the relays if you want to keep it simple and one speed. You hall signals are going to be off by 30o or something like that I think though, you would have to check what needs to be done to adjust these. You may have to flip one of the halls over or something at the same time you reconnect your three phases inside the motor. I believe Dirty's controller build thread had some info about this a few months back...

This would give you 1.7X more RPM's if I understand it right...

Pat

 

[jondoh]

Does anyone know how to determine what size spokes to buy?

this is a problem. Chuck takes the hub and the rim he wants to lace it to and then calls a specialist to measure the distance and give him spoke lengths. Chuck then cuts the spokes to length (he has a cutter). Sorry, i wish it were easier. The problem is that there are a number of styles of rims and they don't all have the same spoke length.

 

[recumbent]

I think your "WE" motor is equivalent to a 408, if you go to a faster motor, you reach the point where torque is sacrificed for speed. With wind resistance trying to slow you down, your not going to have enough power to push your bike any faster.

You reach the point where your unloaded wheel speed may indeed be very fast, but you won't be able to power-up your bike to your wishfull speed because of your lack of torque. If that makes any sense.

My bike for example uses a 406 motor and 48volts (only 15 batteries though) in a smaller 20 inch wheel. I doubt i'd be able to reach any faster speed with a 404 because of the lack of power to breach the wind barrier, or resistance.

Point being, don't go any lower than 405 or 406 because you'll just bog down, besides not having enough pick-up, and hill climbing ability.

What about the "Nine Continents" motor, more poles, smoother finish and cheaper price If you choose the faster winding count designed for the 20" wheel, it will be very fast indeed i would think. Check them out on Justins simulator first, to see if the fast count will pull your bike with your 26 inch wheel.

 

[voicecoils]

Look at bmc hubmotors.

400w and 600w nominal brushless geared (~10lbs)
1000w nominal direct drive.

All three are aimed towards high speed at lower voltages (36-60v nominal).

Highpoweredcycles and cycle9 or "knuckles" on e-s are north american sellers / points of contact.

Contact them with your requirements.