Help finding a solution to Bafang gear stripping

[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.

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.

$5 was to install a bearing in the gear Knuckles sent me. I'm sure stainless would cost more than the "Tylon" quote I got, but I think I understood correctly that some type of metal could be cheaper. Sorry but after 11 years my spanish still sucks. The only way we're going to find something cheap is if we find a place that has some old stock that just happen to be exactly the size we need. One of those surplus outfits could prove to be a real bonanza.

John

 

[docnjoj]

Hey folks! Lets not get carried away with "cheap". I have seen Puma steel gears go for up to $60 a set. Granted its a more expensive motor, but its our folks putting in the time and testing to make this work. They should make some to cover cost etc. if this solution proves successful. Just MHO!
otherDoc

 

[John in CR]

Hey folks! Lets not get carried away with "cheap". I have seen Puma steel gears go for up to $60 a set. Granted its a more expensive motor, but its our folks putting in the time and testing to make this work. They should make some to cover cost etc. if this solution proves successful. Just MHO!
otherDoc

Doc,

I couldn't agree more. I too need to resist the urge to look at this purely from a cost standpoint, and instead look at it in terms of value. Durability is "worth" a lot to me, and even if it takes $100 in mods plus a couple of hours of my time to turn this economical, lightweight, high torque motor into a solid performer that can deliver years of reliable service without worrying about nursing the throttle, then I'm definitely game. Metal gear(s) should start to make a sonic warning before they go, which I like much better. I just want something I can trust, because the idea of peanut butter gears on the other side of a mountain 20 miles from home simply isn't acceptable.

Are there other mods we should look at while we have it open? Yes the leads are a bit spindly, but at 72V+ I really don't want to run high amperage through it anyway. That's just asking for heat problems. I will examine the interior wire connections while I have it open, since one guy did have a loose phase connection. What about bearings...is that something we should look at too?

John

 

[docnjoj]

I too gave it a lookover, and compared to a P2A it is much cheaper construction! Not only rivits where screws and bolts are used, but generally designed not to be reused, except for the gears! It also has a much higher gear ratio (about 5:1) than the P2A (about 10:1) so its a little like apples and oranges. The reason I conpare the two is that they are almost the same size and use the same spoke length.P2A has helical gears of very hard plastic and one metal! I'll try to provide pictures tomorrow, but the point is that Bafang is made OK for the money! It just isnt "top of the line" quality, and is priced as such! Lets solve the gear thing and let Bafang upgrade the rest of it! These motors can last a long time! My P2A got 3000 miles over 4 years before it ate its gears!
otherDoc

 

[docnjoj]

Actually, Brett White still has pictures of P2A internals on his website here: http://www.users.bigpond.com/solarbbq/P2-A.htm Check out the gear quality!
otherDoc

 

[voicecoils]

...It also has a much higher gear ratio (about 5:1) than the P2A (about 10:1) so its a little like apples and oranges....Lets solve the gear thing and let Bafang upgrade the rest of it!

Bafang is 4.3:1

Another thing to look at would be the freewheel assembly that the nylon gears mount to. It may have a limited life as well. Nogwin is nearing 2k miles however, so he's our best torture tester yet IMO. The freewheel assembly cannot be disassembled from what I could see, so a bit hard to check the construction quality.

 

[John in CR]

nt

 

[TPA]

Voicecoils says the bearing is the 608zz. I am considering making some gears out of 6061 aluminum. Can the bearing 608zz be confirmed with absolute certainty? And should they be shielded or sealed?

Can anyone say whether it would be a good idea to increase the o.d. of the gear slightly to cut out the slop?

 

[voicecoils]

Voicecoils says the bearing is the 608zz. I am considering making some gears out of 6061 aluminum. Can the bearing 608zz be confirmed with absolute certainty? And should they be shielded or sealed?

Can anyone say whether it would be a good idea to increase the o.d. of the gear slightly to cut out the slop?

The bearings on the gears I've got are 608Z. The replacements I've got on hand are 608ZZ, I don't actually know what the difference is myself. Same size though.

Here's the gear again as a refresher:

I think it could be a good idea to increase the o.d. slightly to make up for poor manufacturing tolerances but you'd really need a bafang motor in hand to test with. A more snug fit could increase friction significantly.

 

[voicecoils]

nt

I'll assume you found the freewheeling mechanism

 

[TPA]

my intention is to supply someone with 3 drop in replacements to test for strength and wear. I'm not making any promises, because I'm in school until dec 18th, and time is a premium until then. I've ordered the tooling, but still need to get the aluminum and bearings (I'm assuming shielded is ok looks like whats in the picture). I will try to make many (60?) at one time, but can't promise when they will be ready.

 

[voicecoils]

my intention is to supply someone with 3 drop in replacements to test for strength and wear. I'm not making any promises, because I'm in school until dec 18th, and time is a premium until then. I've ordered the tooling, but still need to get the aluminum and bearings (I'm assuming shielded is ok looks like whats in the picture). I will try to make many (60?) at one time, but can't promise when they will be ready.

Sounds great. I would be happy to be a guinea pig but wouldn't be able to do any testing till the first week of December. After that I'd be happy to give them a go at progressively higher current and voltage to see how they fare.

I've got 4 spare bearings too that could be pressed in locally if need be.

Cheers!

 

[Knuckles]

Another thing to look at would be the freewheel assembly that the nylon gears mount to. It may have a limited life as well. Nogwin is nearing 2k miles however, so he's our best torture tester yet IMO. The freewheel assembly cannot be disassembled from what I could see, so a bit hard to check the construction quality.

The freewheel mechanism in the Bafang looks well machined and durable. I have no concern about its durability thus far.

Voicecoils says the bearing is the 608zz. I am considering making some gears out of 6061 aluminum. Can the bearing 608zz be confirmed with absolute certainty? And should they be shielded or sealed? Can anyone say whether it would be a good idea to increase the o.d. of the gear slightly to cut out the slop?

I would stay with the 1.25 module 28-tooth standard for now. With metal it is good to have a little play for thermal expansion.
The existing nylon gear is exactly a 1.25 module 28-tooth gear.

Also any bearing would do fine. It just needs an 8mm bore. It doesn't have to be a 608. But a sealed bearing is always preferred.

Just hearing today that a Chinese gear manufacturer (same as makes the metal gear for the PUMA) will make orders of 500 metal gears for the Bafang.
However, I would encourage a smaller startup batch and more testing first.

 

[johnrobholmes]

Shielded bearings have lower rolling resistance as compared to sealed. 608z should be single shield, and 608zz should be double shield.

 

[Knuckles]

John,

Are you planning to get a dozen or so metal "test" gears for the Bafang any time soon?

 

[johnrobholmes]

I have access to either 10ft of gears or none right now. I have not gotten the gearblanks cut yet.

I am working harder to get the motors built with consistent phase and hall wires so that we can predict how to hook em up. I already had a customer burn one up. Otherwise I have been very pleased with the construction. I may even see if I can get the inner workings of the motor separate for a divorced driveline system.

 

[docnjoj]

So when can I get my Bafang back on the road? I need 2 Nylon and 1 steel combo, at least at first! To whom do I send money to? And how much? Sorry to be so insistant, but I kinda like the motor!
otherDoc

 

[Knuckles]

John in CR may be the best bet for a batch gears with bearings. Three metal gears will also work btw.

Maybe I need to work out some "trade" with John (controllers for gears perhaps?).

Then I can distribute the gears out to folks.

 

[docnjoj]

Noise level with three metal gears will probably be too high for my sensitive ears!
otherDoc

 

[Knuckles]

I'll test all metal gears (3) for noise myself. John in CR could do the same.

 

[docnjoj]

I'll pay money for the winning combo! Still have a little bit left!
otherDoc

 

[docnjoj]

One would think that Bafang would have more than a passing interest in all this activity. The Chinese dont overvolt like we do, but they sure overload their bikes as true means of transport and commerce. I'll bet their gears also fail from heavy loads!
otherDoc

 

[johnrobholmes]

But the motor can only provide so much power on 36v. I have beat the snot out of mine on 36v with zero issues. Even my 16" build on 72v does well, but I baby the throttle to ensure I don't fly off the back. :lol:


Except for this issue I still really like the Bafang motors.

 

[docnjoj]

Quite true, JohnRob. But they dont use little teeny wheels either. They have those 26-28 cart wheels on their bikes! Remember the 155 mm dropout clearance for the rear ones?
otherDoc

 

[John in CR]

I only have the one metal gear, which is now installed. I'm finishing my Konion packs and wiring today, so I should finally be on the road with my 2wd tomorrow. I agree with Doc, Bafang needs to be resolving this issue. In the meantime, don't count on me as a source for gears any time soon. I only have the one Bafang, and I want to give the alignment some thorough testing before buying into the "Bafang solution". Plus I've got a dozen different motors and kits in route, which should start arriving later this week, so my plate is full. I have to come up with a drivetrain and then build a bike that is efficient through the wind carrying 4-5kwh of batts for my coast-to-coast on a single charge ride. The Bafang may be part of that if the large motors I'm getting prove inadequately efficient on the flats, and the 1 steel geared Bafang holds up to my abuse.

Assuming it does hold up, I'll order 100 Bafangs as a low cost solution for the hilly terrain down here, so I'd need gears too, but the earliest would be January.

John