izeman
1 GW
i guess this was a joke. there are a lot of ebikes in CA. and none i saw had automatic transmission. what should that be for anyhow?
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Converting a hubmotor to a middrivemotor
- Thread starter crossbreak
- Start date
crossbreak
1 MW
played around with phase amps and battery amps settings to find the limits of the EB312 controller with the Bafang BPM @74V. Since it was easier for me doing this on my commuter, I just tested the controller on that bike, it has a Bafang CST Code 10 which is (i thought) almost the same as the BPM code11.
Well, it's not. I didn't hook up LCD/temp-sensor for this test, since I just drove down the street once, i thought even a hub can't heat up so fast. I programmed 40amps battery and 60amps phase current and drove down the street (300meters). On my way up it suddenly stopped. Short circuit
I could feel it blocking when moving the bike backwards. When looking on the Wattsup (on the Battery), is saw the reason: Watts_Peak: 5050W something got wrong with programming here, it should have been 77V x 40A = 3000W
I used the same setting in the converted BPM2 which never got too warm. Here is the result.. on the left you see the CST stator, on the right a BPM stator. Notice the difference in copper and thickness of the back-iron of the CST. Both smaller.
Well, it's not. I didn't hook up LCD/temp-sensor for this test, since I just drove down the street once, i thought even a hub can't heat up so fast. I programmed 40amps battery and 60amps phase current and drove down the street (300meters). On my way up it suddenly stopped. Short circuit
I could feel it blocking when moving the bike backwards. When looking on the Wattsup (on the Battery), is saw the reason: Watts_Peak: 5050W something got wrong with programming here, it should have been 77V x 40A = 3000W I used the same setting in the converted BPM2 which never got too warm. Here is the result.. on the left you see the CST stator, on the right a BPM stator. Notice the difference in copper and thickness of the back-iron of the CST. Both smaller.
Attachments
AH! sorry for the damage, one of the most valuable things about this forum is that we can compare notes and everyone can find out how many volts/amps a particular motor can actually survive...
crossbreak
1 MW
yep, for my commuter i will use a BPM2 now as well.. Just not converted. The max power will be the same: 1200W peak for the commuter, 3600W I use in the converted middrive. Just 1/3 when not converted... still I will ALWAYS connect the temp probe 
Everything bad has something good... my Suzuki DR650 Enduro i drove only 4000km in the past 2 years will be used more frequently till i got a new hub for the commuter
I would drive one of my other bikes (converted hub), but they are all way too illegal for the road
Everything bad has something good... my Suzuki DR650 Enduro i drove only 4000km in the past 2 years will be used more frequently till i got a new hub for the commuter
I would drive one of my other bikes (converted hub), but they are all way too illegal for the road
crossbreak
1 MW
Some more info about the CST:
It has 0.3mm laminations (BPM+BPM2 are 0.5mm)
It has 125mm stator dia, 18.2mm width (BPM has 130mm and 17.0mm)
-> The stator surface is about equal, BPM: 6943mm², CST has 7147mm²
Windings: 6 Strands 0.5mm dia for both, BPM is 11T / Code11, the CST is 10T/36V_205rpm, which gives the BPM 10% more copper mass
It has 0.3mm laminations (BPM+BPM2 are 0.5mm)
It has 125mm stator dia, 18.2mm width (BPM has 130mm and 17.0mm)
-> The stator surface is about equal, BPM: 6943mm², CST has 7147mm²
Windings: 6 Strands 0.5mm dia for both, BPM is 11T / Code11, the CST is 10T/36V_205rpm, which gives the BPM 10% more copper mass
SolarRay
100 mW
This implies that, cst more suitable for use as a one-speed middrive. Hmm.crossbreak said:
crossbreak
1 MW
yes,exactly what i thought asw well... but i didn't spin it to 4000rpm yet and measure no load current (ok I wont EVER do anymore with this one ). In theory it should be below 2amps.
Dont forget than you need around 88V or 24s lion for such rpm, even with a fast wind.
). In theory it should be below 2amps. Dont forget than you need around 88V or 24s lion for such rpm, even with a fast wind.
LowkeeRider
100 mW
- Joined
- Jul 17, 2012
- Messages
- 49
Hi Crossbreak,
I followed your thread closely. I like this idea because I can match the cadence speed. I have a BPM2 48v500w(328 rpm) motor that I want to convert to middrive but I don't have many tools. Could you list what tools are needed to complete this convertion? Could you also comment on the advantages of left vs. right crank wheels? Would it be safe to put 35amp through this motor to get 1750 watts?
I followed your thread closely. I like this idea because I can match the cadence speed. I have a BPM2 48v500w(328 rpm) motor that I want to convert to middrive but I don't have many tools. Could you list what tools are needed to complete this convertion? Could you also comment on the advantages of left vs. right crank wheels? Would it be safe to put 35amp through this motor to get 1750 watts?
izeman
1 GW
3 arm puller, screwdriver, file, drill, tap cutter
crossbreak
1 MW
iceman is right. You also need someone to turn down your shaft on a lathe ( the big stator holder has to go)... or grind it yourself, if you are good with the angle grinder:You could also grind it. The part where the the old stator holder is just has to be grinded away... it does not have to be 100% round. The just has to be enough clearance between new stator holder and shaft. I can make pics and post as soon as I convert my 3rd BPM2.
What you also need of course: New, slightly smaller bearing for the cover (28mm x 15mm x 7mm). Bearing adapter. New stator/rotor carrier ( I can send you). 3 M5 bolts to mount it ( you have to shorten so they dont rub at the rotor). Maybe you want to mount a heatsink, then you need ~1mm thick thermal foil and a heatsink additionally. But you can add that later if you want, it also works good without.
And an adapter for a sprocket, I can send you as well.
What you also need of course: New, slightly smaller bearing for the cover (28mm x 15mm x 7mm). Bearing adapter. New stator/rotor carrier ( I can send you). 3 M5 bolts to mount it ( you have to shorten so they dont rub at the rotor). Maybe you want to mount a heatsink, then you need ~1mm thick thermal foil and a heatsink additionally. But you can add that later if you want, it also works good without.
And an adapter for a sprocket, I can send you as well.
LowkeeRider
100 mW
- Joined
- Jul 17, 2012
- Messages
- 49
That could be challenging, I don't know anybody with a lathe. So if I understand it correctly it is not to replace the existing shaft with a new one just grind it down. I will open it and see what it looks like. I will definitely need some parts from you crossbreak. Is this process reversible?
crossbreak
1 MW
no. the metal you grind away wont come back
it would be nice to make a new shaft. But the BPM shaft is quite complex (4-spline) in contrast to the other bafangs and the simple made MAC shaft
it would be nice to make a new shaft. But the BPM shaft is quite complex (4-spline) in contrast to the other bafangs and the simple made MAC shaft
I applied the new method to make shaft for Bafang BPM:
1. divide the shaft into 3 parts
2. drill a hole 17mm into rotor carrier
3. drill a hole 10х10mm into shaft part
4. make part of new shaft (steel round bar 16mm)
5. assemble two parts of the shaft with Loctite 638 (very strong retaining compound)
6. whittle the shaft on lathe for bearing of cover
It's most cheap way to make a changes inside Bafang BPM I found.
1. divide the shaft into 3 parts
2. drill a hole 17mm into rotor carrier
3. drill a hole 10х10mm into shaft part
4. make part of new shaft (steel round bar 16mm)
5. assemble two parts of the shaft with Loctite 638 (very strong retaining compound)
6. whittle the shaft on lathe for bearing of cover
It's most cheap way to make a changes inside Bafang BPM I found.
crossbreak
1 MW
LowkeeRider
100 mW
- Joined
- Jul 17, 2012
- Messages
- 49
"Is this process reversible?" by that I mean if I could convert it back to hub motor.
jateureka
10 kW
Looks like an IGH sprocket carrier.crossbreak said:
EDIT: nope, now that I looked again it needs to be the other way...
crossbreak said:Nice copy of my sprocket adapter
It is carrier for adapter (right top corner) for cut thread M30x1 on a lathe.crossbreak said:
I order adapter billets in laser cutting company (steel 14mm) and drill 6 holes and cut thread, it's most cheap way.
crossbreak
1 MW
just saw i never posted the pics of my other bike with converted BPM2... here they are.. Dual Freewheel Jackshaft at it's best
They are not up-to date either, i grind away the spoke flange... built another converted hub bike in the meantime (The BMC with Hammerschmidt instead of Dual Freewheel Jackshaft)
They are not up-to date either, i grind away the spoke flange... built another converted hub bike in the meantime (The BMC with Hammerschmidt instead of Dual Freewheel Jackshaft)
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Wonderful! it looks good...
izeman
1 GW
a very nice motor mount and a clever way to adjust primary chain tension!
cal3thousand
10 MW
For the guys that have done this conversion, how much work do you have to put in to keep your system working?
I hear many people putting down middrives due to the complexity and the amount of work required to keep them happy. How much work are you guys putting in after completion? maintenance.
I hear many people putting down middrives due to the complexity and the amount of work required to keep them happy. How much work are you guys putting in after completion? maintenance.
crossbreak
1 MW
not much. Change the chain more often.. that's it.. did not change sprockets yet.
cal3thousand
10 MW
crossbreak said:
That's what I'm hoping.... I hear comments about more fixing than riding, so I wanted to make sure.
crossbreak
1 MW
yet i did more fixing than riding, simply since it took so long to develop this whole mod. And since it is not my only bike. Just dont have enough time to ride it very often
waynebergman
100 kW
Hi cal3thousand--- I am sorry I can not really give a fair account for how long you can go trouble free as my set up is in storage right now as my battery pack has gotten wet and I have no battery for it. I am guessing I have only put about 500 miles on the hub conversion but not sure. The tinkering I had to do after first completing the hub motor conversion was more spacing issues of the various compoenents inside the motor itself to get rid of any rubbing noises. I think IF the conversion is done successfully with a SOLID MOTOR MOUNT to your frame and a properly working derailer it should be fairly trouble free. If a person could afford it, the ideal solution would be a clean chain line to a rohloff internal hub and a good solid mounting of the motor to the frame. Obviously the more power put through the system the more it is going to cause you grief. I think it could be a real nice system at under 2000 watts with a Rohloff IGH.
I highly recommend the "crossbreak style" left side pedal assist to the freewheel on the motor shaft. On my bike frame it was simple because it was a hard tail. This part of the conversion was the best surprise of all how well it works. With my gearing you can easily still give pedal input at 40MPH going down small hills.
I highly recommend the "crossbreak style" left side pedal assist to the freewheel on the motor shaft. On my bike frame it was simple because it was a hard tail. This part of the conversion was the best surprise of all how well it works. With my gearing you can easily still give pedal input at 40MPH going down small hills.
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