Bafang motor weight reduction

[Mathurin]

Looking for ways to make a weight weenie bafang motor. Thoughts? Here's what I got so far:


Going sensorless would eliminate hall cables and they can be removed from inside the motor. I bet that would more then make up for the sensorless module's weight.

Motor phase lead length could perhaps be reduced a few cms by making them exit inside the frame kinda like Link did(?)

New spoke holes for normal quality spokes could be made in the flange with drillium installed where the oversized spoke holes are. The inside of the outer shell could perhaps be bored out.

Freewheel seems to be made out of thick heavy stuff, dunno what it looks like inside but I bet there's quite a bit of excess material here. Anyone have a pic of the freewheel taken apart?

Motor cog plate that screws onto the magnet basket looks like it could use quite a bit of drillium as well.

Axles are a few cm too long for nothing so they could be shortened, also the side without a wire coming out could be hollowed. Kinda like the guy on this forum that turned a 4X clyte into quick release.

Not sure what could be done with laminations, I know most of the weight is probably there.

Magnet holding basket looks like it could use some drillium as well, in the spokes, near the centre where the cog goes, and on either side near the magnets the metal goes further then it needs to. Special attention to good balance here since it seems fairly heavy and spins ~5X wheel speed.

If they can be found, the screws could be replaced with Ti ones. Ti axle nut?

Any guess how much it would cost having this machining done by a shop? I'm guessing about the same as motor purchase cost?

 

[docnjoj]

Why? The motor is already light! Sounds like there are cheaper, easier ways to lighten a bike overall.
otherDoc

 

[Mathurin]

Yes it's light and fairly powerful, that's why I ended up going in more detail over it.

I've come to accept that ebikes are inherently heavy and that to get one that rides like a bike will require going over every detail and spending a fair amount of money to control weight. For now I have a lot of free time and no income, what with having fallen off a cliff and such. So I'm getting a good idea what's realistic and where I'm going. Then when I get money, it will happen.

Also, wheels are a place where weight really matters, heavier tires somehow make the whole bike feel a good bit more heavy. Although at hub level I doubt it would make so much difference, but still. And yes there are cheaper ways, for example 170$ would nuke 905g off my wheels without compromising durability or puncture resistance, that's 0.19$/g. I'd expect more around 1-2$/g for the motor.

 

[docnjoj]

I forgot about the cliff thing! How are you doing?
otherDoc

 

[Mathurin]

Well it's been 5 months and it's still painful to walk, I need crutches to do it. Can't wait to get around with a pimp cane, shit is gonna be sooo cash!

 

[Digitalworm]

Hi.
Can you help me, please...
How can i remove detail #4?
I'm talking about the big gear in the picture 3
This thing is screwed on the thread?
maybe she just stuck?
Can it be heated to remove?
Sorry for my bad english...

 

[dogman dan]

Will run crappy sensorless, and you save a very few ounces removing halls and the wire for them.

 

[neptronix]

The only thing i would recommend is shortening the axle and axle wire lengths.

I don't recommend drilling things for weight loss. You will lose structural integrity. These motors are already fairly optimized for low weight.

If the covers are steel, then there is a place to lose weight right there.

The gear assembly has a freewheeling mechanism in it, i would not touch that. geared hub motors tend to have weak freewheel mechanisms in the first place that aren't reliable. Whatever you do to it would make it even worse.

 

[FMB42]

In my case, it would be far cheaper for me to lose some pounds than to spend money trying shave ounces of weight from my bikes.

 

[wineboyrider]

If you are riding a street bicycle try Keplers friction drive? They are super light and can use tiny 5s and 6s batteries, plus they remove quick and the bicycle is still a bicycle!

 

[dogman dan]

Exactly, for lightest weight, a friction drive is the clear winner.

 

[jbond]

The photos are of an older Bafang with the bolted on end plate. The current SWX motors have a screw on plate. They're only 3Kg. They run fine sensorless below about 20A controller limit.

With the new motors, I think you'd be better off trying to reduce battery weight than trying to reduce the motor weight. For short distances something like a 36v 12s2p or even 12s1p A123 pack. If you're up for it, then RC Lipo. The latest ECitypower LiNiCoMn batteries (from BMSBattery) are impressively light but the low C means you really need at least 10AHr for an SWX motor.

 

[dogman dan]

I may have had the wrong controller to use a gearmotor sensorless. Mine had a tendency to not know which way to spin, forward or back. Aotema controller. Would have worked fine with one with the freewheel locked.