Nylon Gears in Ebike motors. Why?

[Ghost1951]

Is there some important technical reason why companies like Bafang use a nylon gear in the BBS01 for the first stage gear reduction system between the rotor and the rest of the drive system? Or is it just a matter of cost cutting?

I know there are other nylon gears in hub gears too.

It seems to me that these must be weak points for wear and tear as far as durability goes.

Thanks.

 

[sjpt]

I think there are two reasons. (1) Quieter. (2) Safe point of failure if anything does go wrong, cheap to replace and potentially avoiding more complicated and expensive failures.

I'm sure the experts will be replying soon ... I look forward to their opinion.

 

[flecc]

Noise is the biggest factor in hub motors, the nylon gear(s) being much quieter. For example Heinzmann used nylon on their 200W model but steel gears in their higher powered hub gears, having to put up with the noise then.

Noise is probably a big factor in the primary higher operating speed position in crank motors.
.

 

[guerney]

BBS01

There are steel gears available for the BBS01B, and although they'd be noisy, I bet the sturdy Bafang motor case or something else, won't collapse like the puny TSDZ2 would

Steel Gear for Bafang BBS01B BBS02B BBSHD G320 G340 Mid-motor Upgrade Version Metal Gear Long Life Bafang BBS Motor Nylon Gears - AliExpress 18

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www.aliexpress.com

Noise!

 

[Az.]

You can buy brass replacement gears for Tongsheng motors. People say they are not more robust than nylon gears and when people use their motors incorrectly, then they get shredded too.

 

[Ghost1951]

Thanks for the replies all.

That noise in Guerney's link is ridiculous, but the motor is NOT a BBS01, because it is putting out well over 2hp to accelerate like that and drive the bike to forty miles an hour. I wonder if running the steel gear in an ep90 oil bath would remove that shriek? I'm thinking you could drill a small hole in the top of the appropriate compartment and insert a few ml of EP80 or 90. If you tapped the hole and used a short screw to seal it, maybe with a soft washer, it might be a whole lot quieter.

I have an old SRF 3 speed that I did that with, but I used a very light oil. It still works if I ever dig the bike out from behind a load of junk. That bike did over 4000 measured miles before I retired it. Probably would have done the same just with the original grease though.

EDIT:

In my experiment with the SA SRF 3, the amount of oil inside had to be very little or it soon 'adjusted' its own level by coming out all over the spokes. No oil seals in that cheaper hub, unlike my original SA 3 speeds.

 

[Ghost1951]

Is it really true that the nylon gear needs a special type of grease?

If it is, why?

 

[saneagle]

Is it really true that the nylon gear needs a special type of grease?

If it is, why?

Nylon absorbs oil based grease and swells slightly.

 

[Ghost1951]

Nylon gear failure in BBSHD

 

[Ghost1951]

Nylon absorbs oil based grease and swells slightly.

Thanks.

 

[saneagle]

Is there some important technical reason why companies like Bafang use a nylon gear in the BBS01 for the first stage gear reduction system between the rotor and the rest of the drive system? Or is it just a matter of cost cutting?

I know there are other nylon gears in hub gears too.

It seems to me that these must be weak points for wear and tear as far as durability goes.

Thanks.

I guess you're talking about crank-drive motors. Hub-motors have nylon gears too, but failure is extremely rare, except when the motor has been substantially over-powered or jammed by rust.

 

[Az.]

Tongsheng Autopsy - Need Input

Please see below & attached pic. Has anyone encountered similar? I've moved on from Tongsheng to ToSeven & Bafang. But i wanted to open up my ild TSD's just for learning purposes and found this mess. My questions: What is the gold / copper dust in the motor? What causes it? What do I do...

endless-sphere.com

 

[Ghost1951]

Tongsheng Autopsy - Need Input

Please see below & attached pic. Has anyone encountered similar? I've moved on from Tongsheng to ToSeven & Bafang. But i wanted to open up my ild TSD's just for learning purposes and found this mess. My questions: What is the gold / copper dust in the motor? What causes it? What do I do...

endless-sphere.com

Wow. Horrific damage there. No sign of any lubrication. Bone dry metal gears. Not good. Also possibly some misalignment issue - worn bearings perhaps. Mainly though, I'd say some naive person put that together bone dry after removing the nylon gear and replacing it with one made of brass.

Edit: on a Youtube channel I used to watch about Royal Enfield motorcycles, there was a case in which the steel gears of an old Albion gearbox were worn to shreds like that when it had no lubrication. Those boxes were sometimes packed with grease (early Indian made ones) and in this particular case, the bike was run in a spell of very cold weather here in England (rather than Delhi) and the grease hardened and was thrown to the edges of the box, leaving the gears dry.

 

[guerney]

Some brass alloys are self-lubricating, which is why many locks are brass - whoever manufactures these brass gears must have considered the puny ickle TSDZ2, and reasoned strong steel wasn't necessary.

 

[flecc]

Is it really true that the nylon gear needs a special type of grease?

If it is, why?

According to a plastics expert I was chatting with a few years ago, the best lubricant for nylon gears is water. Difficult to arrange for them to run immersed in water in our motors though.
.

 

[Ghost1951]

Some brass alloys are self-lubricating, which is why many locks are brass - whoever manufactures these brass gears must have considered the puny ickle TSDZ2, and reasoned strong steel wasn't necessary.

To be honest, I don't see that there is much in common with the loads applied to a lock and an un-lubricated skew gear in a half kilowatt drive system. That is a very harsh environment and is a recipe for failure in my opinion. Steel on brass at these power levels is a guaranteed fail. Suitably greased up, or lubed with hypoid type oil is a world apart from what we see in those photos. Gearboxes in cars use special extreme pressure sulphur based additives for a reason.

 

[Ghost1951]

Early Bafang BBS series had that covered.

Water got in naturally through the pedal shafts.