Help finding a solution to Bafang gear stripping

[John in CR]

Knuckles,

Don't forget who asked first for metal gears back in July...That is once you have any to share.

John

[fechter]

F-N-A!

spill it!

I need a "you so crazy factor" on a scale of 1 - 10

You get at least a 9 for scoring metal gears. Walk-in no less.
Let Mr. Gear Dude ride the F'N bike around (like with 72volts) and then talk special order. How many gears can you get in trade for a motor? Hey if it's a special order, then they make'em with the right size bore for the bearings.

[johnrobholmes]

Alright, I have three sources that can get gears for me, and one machine shop that will call me back about obtaining gear stock. Another machine shop can cut the gears in brass, but it may be expensive since they wouldn't start with gear stock.


So we have a choice of stainless, delrin, Steel 9 SMn 28K, and brass construction. The Delrin will be very affordable, next is stainless, and the brass may be most expensive.


I am leaning to using the delrin first to see if it works. I bet it would hold up much better than the stock nylon and still be very quiet. My next choice is the stainless, since it is decently soft.


Expected price points would be $20 each delrin with bearing, and $35 each stainless with bearing-but this is low quantity pricing. Brass I haven't gotten a quote yet. I will run my bike on 72v and ruin the gears to see where the limit is once I get replacements.

[Miles]

I am leaning to using the delrin first to see if it works. I bet it would hold up much better than the stock nylon and still be very quiet.

It would wear better but there's not much difference between them strength wise - impact strength of Delrin is a bit better. I would go for metal, I think.

[Knuckles]

First test run of metal gear is success.

So it is now firmly established that the gear size is M1.25-28 w/ 8mm bore ...
The original nylon gear has a 10mm face.
My steel test gear has an 8mm face.

I replaced the existing washer with a thinner washer to make up the difference.
Just added a few drops of oil as lubricant.

Only a slight increase in noise level and a very solid feel.
Time will tell if the gear post wears out.

Of course a metal gear with bearing is the way to go.
(These test gears cost me $10 ea btw and can still be special ordered).

gear_post.jpg (67.71 KiB) Viewed 814 times

metal_gear.jpg (43.01 KiB) Viewed 746 times

[Knuckles]

i cant wait until knuckle comes back with the test results lol will it work?!

if it does work, maybe knuckles can stock a few of these for all of us hehe.

maybe bafang would start supplying them too if this works.

i totally agree with kurt, im worried knuckles might wear the post out.

So far the gear is working fine. Sounds good and feels great. But just one day of local riding.
This is more a "proof of concept" endeavor. But I do like the one steel gear combined with the two
original nylon.

I can either buy more of these 8mm face gears or I can go back to the gear dudes and ask for a version at 10mm with bearing.
But knowing Dr. Holmes I am sure he is already on it. (Go John Go!)

Of course it would be nice if CHINA (A hem) would just do this so that the Western World could buy it.

[lawsonuw]

@johnrobholmes: I'm going to agree with Miles on this, and say skip delrin as it will perform about the same as the nylon gears. If you want to stay with plastic, Torlon or a graphite fiber filled Nylon/Delrin is my guess at the best bet. Of the metal choices brass will be most tolerant of running dry, though bronze would be better. Any of the steel options should work just fine though. My two cents says go with whatever metal gear is cheapest.

Marty

[johnrobholmes]

I have some 10mm face gearblanks with 4-6 week lead time available, and the rest would be custom machining (if we are just considering metal). $10 is cheaper than I have found for the blanks, but the ones I found were USA made. Add in machine time and bearing cost on top of blank cost.

[johnrobholmes]

Blam Ba Lam! Just got an email from a company that will make 10ft of spur stock for me (200ish gears), but only in steel. 8-9 week lead time, and totally worth it. Gonna go for this one! I will probably have to get another company to part and bore each one.

[voicecoils]

Blam Ba Lam! Just got an email from a company that will make 10ft of spur stock for me (200ish gears), but only in steel. 8-9 week lead time, and totally worth it. Gonna go for this one! I will probably have to get another company to part and bore each one.

Cool, only downside is I want to be blasting around NOW

Seriously though, the bearings are $0.50 each so that is just a small concern. To bore and press the bearings will certainly cost more, but hopefully less then the cost of the sliced up spur stock.

It's looking good

[Freddyflatfoot]

I'm gonna keep an eye on all this!
Even though I don't intend to go over 36v at this stage, I might be tempted to add a metal gear, just to improve the longevity and reliability of the gearing system.
Sounds like the one metal gear is a good option!

[mickk]

I toast all of you that helped find a solution to a problem that a lot of us will eventually face I reckon.

[gogo]

I'd be in for two for sure and maybe more.

[voicecoils]

Turn peanut butter to vegemite



One small tub of vegemite posted worldwide to the first person who send me 3 metal gears, pressed w/ bearings to solve my peanut butter problem

[Gregory]

If metal gears are made, ready to drop in, I'd be in an Aussie order too.

[aquietstorm]

Turn peanut butter to vegemite



One small tub of vegemite posted worldwide to the first person who send me 3 metal gears, pressed w/ bearings to solve my peanut butter problem

Having tasted vegamite I have to pass.

[johnrobholmes]

is that stuff the leftovers from brewing beer?

[HornetB]

You'd be correct John.

Made from yeast extact, a by-product of beer brewing.

I have a jar myself that I brought with me over to the US, an Aussie bloke can't leave Australia without a jar of Vegimite. I have to ration it out for special occasions like AFL grand final day (go them Hawks!!! ).

Just one of those Aussie things, not fully appreciated by the rest of the world LOL!

[Miles]

Just one of those Aussie things, not fully appreciated by the rest of the world LOL!

Ahem... In the UK we have Marmite - a superior product that pre-dates the Aussie rip-off....

[HornetB]

Just one of those Aussie things, not fully appreciated by the rest of the world LOL!

Ahem... In the UK we have Marmite - a superior product that pre-dates the Aussie rip-off....

LOL!! Marmite! I bet that goes great with warm beer

Nah, kidding, jokes aside I do love a nice hand pumped cask ale and I dont mind a true bitter served at the correct temp.

Ok, enough off topic banter before I get in trouble.

[voicecoils]

gear health update. Traveled 20km two days ago and checked the gears. Nice and fresh looking. See those crisp teeth?
I'm down on 36v nominal (~40v actual). Accelerating while peddling of stop lights and steep hills the gears start to whine and make me nervous. This happens at around 15-20a according to the cycle analyst. I've briefly seen ~30A but only for a second, and my 30A fuse did not blow. Limiting to 10A just doesn't provide much assistance.

moly_gears.jpg

gears are packed with moly grease (3% was all I could find), hope it keeps them fresh :-)

(179.09 KiB) Downloaded 517 times

Today I traveled just under 30km. I will check on the gears again soon. Also, I plan to jump up to 72v nominal (~80v actual) and set the Cycle Analyst to 10A. I'm hoping this will be safe for the gears, but give me greater assistance at higher speeds. For the moment the bafang tops out at 25-30kph, which isn't too exciting.

Anyone have updates on beefy gear solutions?

[Kurt]

I am just thinking that perhaps the speed that the gears will be turning/meshing together at 72v will give you to much friction and the gears will fail again. Are you sure its the torque that is making them fail ?
kurt.

[voicecoils]

I am just thinking that perhaps the speed that the gears will be turning/meshing together at 72v will give you to much friction and the gears will fail again. Are you sure its the torque that is making them fail ?
kurt.

I'm not sure, no. I think both failures occurred on hills however. At 72v if I go WOT from a stop or up a steep hill I think I'll strip the gears even on 10A. I would have to be careful, but it may be possible to reliably operate it as such if I'm only winding it up all the way on the flat, downhill, or gentle inclines. With a bit more km's ridden with the hub I *think* I'm developing an ear for the sound of a straining gear. I'd much rather replicate Nogwin's setup with 66V ~30A but my batteries just don't have that flexibility.

gear speed, torque, heat, lack/loss of lubrication, mechanical shock, meshing issues (maybe gears care compressing under weight of the bike creating a gap between the nylon gear and ring gear at the top of the hub?).

All sorts of possibilities, and no easy way of knowing for sure.

[johnrobholmes]

I rode my bafang on 72v yesterday for an hour, laced to a 16" wheel. No gear stripping or noise. I suspect it is the torque and not the speed that causes the stripping.

[dazzassj6]

When my gears started to stuff up was when i started going up steep hills with WOT. Not from WOT at a stationary start.

Voicecoils, the reason your gears didnt strip this time is because it is rated for that voltage! My stock ebike came with that hub motor and no matter how you abuse the throttle even from start stop on a hill u cant strip the gears.

A theory i have for why it is stripping is because when you go up a hill at a slow speed, it puts more pressure on the bottom of the ring gear, leaving a slight gap on occasionally between the ring and gear. Meaning if you're going up a hill and its struggling the motor will give you more AMPs to compensate this however since there is a gap and the increase AMP will just strip it because its not fully in the ring gear.