Help finding a solution to Bafang gear stripping

[voicecoils]

I've done 60-70km now without stripping my gears. Just checked them an hour ago. I'm starting testing again at 80v but limited to 9-10A, I've done about 5km like this but need do more.

The nylon gears have slung off much of the moly grease from the tooth faces but still look fine. I wiped off excess grease but did not pack in more as the ring gear still seemed quite well greased.

I noticed two other things:

* The piece that holds the three gears only sits flat if you carefully position and seat it flatly. Otherwise the nylon gears will sit askew from the ring gear. I don't know if it's forced into the correct position when everything is bolted down, but if it doesn't sit flat that's clearly a danger to the gears.

* Spinning the three nylon gears around the ring gear (with the motor and pinion gear out of the way) I notice that there's a 'sticky spot' in one position. I couldn't find the cause however. It could be that the ring gear is not perfectly round, the ring gear faces are rough in spots, the nylon gears are slightly deformed, or that the posts that hold the nylon gears are not perfectly equidistant in an equilateral triangle. Lots of possibilities but at any rate a 'sticky spot' could accelerate any opportunities for gear stripping.

 

[voicecoils]

Gearheads,

I've posted an some youtube videos of no load testing with and without the gear assembly on the motor at both 40v and 80v.

Have a look here:
http://www.endless-sphere.com/forums/viewtopic.php?f=6&t=4925&p=110590#p110590

The search for peanut butter avoidance measures continues!

 

[johnrobholmes]

I am still working on it, I think we may have found a supplier in china to make them for a very reasonable price.

 

[John in CR]

This morning I dropped off the metal gear I got from Knuckles to have a bearing inserted. I also left one of the plastic ones for the machinist shop to come up with a price to fabricate copies using better materials, so I should have some quotes on Monday. While I was there the boss proudly showed off a gearset they just finished that was very similar to Bafang's, but this has a ring gear about 30" in diameter with 6" or so planetary gears. He loved the idea of a bulk order of gears, because it's almost as easy to many as doing a few. First they cut the teeth into round bar stock, and then slice it into individual gears. Their labor is pretty cheap, so we may have another source for some reasonably priced gear upgrades.

Over the weekend I hope to finish my 80V konion batt pack and run my 2wd rig with a Bafang rear and direct drive front. I'll take it easy at first and progressively stress the stock gears of the Bafang to try and duplicate the cause of failure. If a minor gear mod gets the Bafang to a point of high reliability then I'd love to use it in a 2wd alignment for hill climbing duty on my 180 mile on a single charge coast-to-coast (Caribbean to Pacific) ride that I'm planning for January or February.

John

 

[set]

guys,

Im not sure if this was ever mention before but has anyone ever considered using helical gears? They would reduce noise making it possible to run metal gears and it would feel smoother. I used to be a big car enthusiast and almost all car transmissions use helical gears. When I saw a video where someone was grinding in all gear, I think it was in a skyline, I asked, "why was he grinding? He must be a bad driver." Someone told me that that particular car had straight gears and explained to me that they are stronger because they engage at 100% at once but are louder, and they don't last as long as helical gears.

Why haven't these gears transfered onto the ebike scene?

 

[Ben]

Why haven't these gears transfered onto the ebike scene?

With helical gears you get some axial thrust because the gears are cut at an angle.

They're also a lot harder to manufacture that straight cut gears and therefore more costly.

Having said that, some motors use them. The main one I can think of is the P2a motor, which has very high quality gears.

Helical should be stronger than straight cut because you get more than one tooth engaging at any given time. They're quieter too.

 

[voicecoils]

It might be a better mechanical approach for this application, I agree. Thanks for the suggestion.

As ben points out, harder to manufacture though. The motors are low cost production to the extreme IMO in mechanical design, materials, and assembly. With that in mind, it is not surprising that the manufacturer went for simple strong straight cut.

It's not something that could be retrofitted either. A new pinion and ring gear would be required and neither are removable unless I am mistaken.

 

[docnjoj]

I was about to take a picture of my P2A motor that broke after about 3000 miles. Surprisingly, it was the steel gear that threw the bearing rather than one of the two nylon planetaries. Absolutely best motor I ever owned! Too bad Brett cant get them any more!
otherDoc

 

[docnjoj]

Uh oh! Houston, we have a problem! On my maiden voyage of my new Ping 48 volt 20 ah battery, we have a Bafang p-nut butter crisis! 6 miles out I hit a bump and the motor just ground around and stopped turningm making really horrid sounds! So here is a first gear destruction of a Bafang on 48 volts! I will order a set from Knuckles, but it seems there really is a problem with gear longevity. Too bad, cause its otherwise a great motor!

 

[voicecoils]

Sorry to hear docnjoj

Here's a list of Endless-Sphere members who've stripped their gears:

Voicecoil: 80V setup twice in a 26" front wheel
Docnjoj: 48V setup once in a 20" rear wheel
Knuckles: 72V setup at least twice in a 26" wheel
(once from accelerating 'shock' once from a friend applying the brake while accelerating)
dazzassj6: 60V setup once in a 26" rear wheel
others?

I'm further convinced that a more robust solution is truly needed.

 

[John in CR]

The machine shop quoted me a price of about $12/ea to make better plastic gears including the bearing. He called the material what sounded to me like "tylon", and said it would perform far better than the nylon gears. He said he could do metal gears for a bit cheaper. I don't know about you guys, but over $40 with shipping for 3 little plastic gears plus the work involved, all to fix what is essentially a $50 motor, doesn't seem to make a lot of sense.

Maybe I'll be more amenable after I give mine some rough treatment and strip the gears, though I do already have a backup set, including 1 metal one with a bearing.

Let me know if you guys want to look further into the fabrication, and find out exactly the material he wants to use.

John

 

[docnjoj]

Hey John ! Thats dirt cheep! If they work out, maybe a group buy would be in order! SDP wants $30 for gears like them, and I believe it doesnt include bearings!
Anyway, the low retail on those motors is about $150-200!
otherDoc

 

[voicecoils]

The machine shop quoted me a price of about $12/ea to make better plastic gears including the bearing. He called the material what sounded to me like "tylon", and said it would perform far better than the nylon gears. He said he could do metal gears for a bit cheaper. I don't know about you guys, but over $40 with shipping for 3 little plastic gears plus the work involved, all to fix what is essentially a $50 motor, doesn't seem to make a lot of sense.

Maybe I'll be more amenable after I give mine some rough treatment and strip the gears, though I do already have a backup set, including 1 metal one with a bearing.

$12/ea is reasonably cheap considering there is gear stock material, sealed bearing, and machining time involved. Maybe your guy was saying "torlon"? See HERE from this thread.

Yes, the motor is not an expensive motor, especially if bought in bulk but its value is in the use it can provide. If it can't work reliably for any distance or any serious power then the value is extremely low. If you plan to do a long distance trip, the low weight of the bafang would be great but who wants stripped gears on the road? My interest in replacement options, ranked, are:

* 3 composite gears impregnated with metal like the new BMC 'thunderbolt' is using
* 1 metal gear (if it can do the job alone) and 2 stock nylon gears
* 3 metal gears
* 3 better plastic gears

How did you get the bearing machined into the metal gear you've got? I don't think it's a matter of 'if you strip the gears' more a case of when.

 

[fechter]

The machine shop quoted me a price of about $12/ea to make better plastic gears including the bearing. He called the material what sounded to me like "tylon", and said it would perform far better than the nylon gears. He said he could do metal gears for a bit cheaper. I don't know about you guys, but over $40 with shipping for 3 little plastic gears plus the work involved, all to fix what is essentially a $50 motor, doesn't seem to make a lot of sense.

When the alternative is a $500 motor, then it makes much more sense. I'd say go for the metal gears.

 

[John in CR]

When the alternative is a $500 motor, then it makes much more sense. I'd say go for the metal gears.

I consider that a fleecing, not an alternative. I can probably find a decent used engine for a car that's good for a whole lot more miles for that price, or there are also a number of multi-kilowatt durable brand new electric motor choices in that price range.

At least it only takes one gear going with metal, so I'll take your advice.

John

 

[Knuckles]

I am reluctant to order any more Bafang motors until a supply of metal gears is available.
I am still riding my "bearing-less" metal gear (same as I sent to John in CR).
But John’s approach to fabrication of an exact replica in metal is correct.

The Bafang is a great motor for it's weight but the plastic gears are clearly a weak link.
Gear failure can occur under normal riding conditions.

Two modifications to the Bafang motor ...
1) One or more metal gears
2) Thicker phase wires (no hall sensors) on a sensor-less mod Infineon.

 

[Rassy]

Hi Knuckles. Just a dumb question, but I didn't think you could use a sensorless controller on a free-wheeling motor. For the record, I have no understanding of how the motor/controller work together.

I am just in the process of testing a couple of Bafang's that I plan to play nice with at 48V, but am following closely what you and John in CR are doing with metal gears. Thanks.

 

[docnjoj]

Agreed! I don need no steenkin thicker wires! I just need gears that can stand up to 48 volts! Also think quiet. I hate to bring this up at this critical juncture, but the squishey nylon was really quiet. My P2A with 1 steel and 2 nylon was also very quiet. But it had helical gears! I hope we dont end up throwing the baby out with the bath water. Thanks Knuckles!
otherDoc

 

[Freddyflatfoot]

I'll keep following this thread with interest!
At this point, I am still more than happy with my Bafang @ 36v. As it also an overvolted motor anyway, up from 24v, the performance is still respectable in hybrid mode (me!) I have done over 3500 k's on mine, and its still going strong.
However, I am concerned that there have been a few motors stripping their gears.
Knuckles, hang in there with theses motors! I would buy another, should I need to.
If I ever strip my gears,I would want to know that replacements, or a solution is available. If you guys come up with a suitable replacement gear, I think I would be tempted to 'upgrade', just to ensure the longevity of my existing motor.
On the other issue of wiring, is it worth doing that, or going sensorless?
Can I upgrade my Ananda controller to sensorless?

 

[voicecoils]

Knuckles,

Can you take a youtube video of the bafang no load with the metal gear so we can here how it sounds? I've got videos of the bafang noload at 40v and 80v in a 26" wheel as well as just the motor itself as a baseline. (http://www.youtube.com/voicecoils)

I've removed the bafang wheel and other ebike bits from my bike for now and returned it to it's original pedal only state. I'll keep an eye on this tread for any progress towards a more robust solution.

 

[voicecoils]

On the other issue of wiring, is it worth doing that, or going sensorless?
Can I upgrade my Ananda controller to sensorless?

The only point would be to way overpower motor, in which case the existing phase wires just don't have the copper for sustained high power draws.

Sensorless means no longer needing your hall sensors which is nice from a reliability point of view as they can fail (water, overheating, etc) and then the motor will no longer be operable. Sensorless also means you can't apply the throttle from a stop. The motor must be spinning first before it can be controlled.

I don't know about the Ananda controller, hopefully someone else will.

 

[docnjoj]

Ditto on awating some gerared solution! I can go to my brushed systems which are fine, but not geared. I think the 16" wheel wil have immense power off the line, but it runs out of oomph way before the Bafang did! Meantime I will hold off with gears , maybe, since progress seems to be occurring. Thanks everyone!
The unbreakable MY1018 and 3 speed rear must go for grandkid Christmas presents, and its just plain too noisy for grownups!
otherDoc

 

[Knuckles]

To summarize my findings ...

1) There is absolutely no increase in noise (72V) with the metal gear in the Bafang. My Bafang is still more quiet than my Direct Drive hub motors (but it will never be faster). My only issue is the single metal gear I have has no bearing. If I could get the metal gears with bearings (at under $15 each) I would be selling the Bafangs right now.

2) I tested the sensor-less module on the Bafang. It works fine AND from a dead stop. It also works WITH the hall sensors connected. The (Keywin) sensor-less module is designed to spin a BLDC (rotor) in only one direction. The only issue with the sensor-less module is the "jitter" at low rpm when BEMF from the phase wires is low. In a geared motor this effect should be reduced. Testing is (of course) needed to prove this is the case. Same applies to the PUMA and BMC geared motors with the sensor-less module Infineon mod.

3) The Bafang at 72V just barely does 30 MPH (26" wheel). 30 MPH is my benchmark for performance. The torque at start-up is phenomenal, however, and the motor stays cool.

4) I hate thin phase wires. Hate Hate Hate Them. If eliminating the hall sensors and beefing up the phase wire gauge works then it is a winner. The only issue would be starting from a dead stop while on a step uphill incline. This could still cause jitter even on a geared motor with the sensor-less module.

So who will be first to step up to the plate and provide metal gears with bearings for the Bafang?

 

[John in CR]

I have a bearing in the one you sent me. Cost me just over $5 plus the bearing. I can get them made for under $15, but I'm not sure of min order qty. What metal do we want to use? I think maybe we should "prove" them some more. I'll go ahead and install mine and then really test it.

I tried the sensorless on my Erato 2 speed and it kicks the shifter out of gear, because that "jitter" is back and forth movement of the motor. Since it is noisy, it can't be good for the motor, so I wouldn't intentionally switch to using it unless it's "pedal first". No load it works perfect, so maybe just some fine tuning is needed in the programming.

John

 

[voicecoils]

I have a bearing in the one you sent me. Cost me just over $5 plus the bearing. I can get them made for under $15, but I'm not sure of min order qty. What metal do we want to use? I think maybe we should "prove" them some more. I'll go ahead and install mine and then really test it.

How 'bout 304 grade stainless steel with the sealed bearing pressed in. A set of 3 gears bored out to the correct size for US$15 would make me very happy. I've got spare bearings of my own but it would be even better to have a ready to go, drop in solution. The bearings should not cost more then $0.50 each.