BMC Ticking, Suggestions?

[Alan B]

Here's a new BMC V4TT that's been sitting a year, now firing it up on a PhaseRunner FOC Controller. But it doesn't sound right. There's some ticking that appears to correspond to the motor RPM.

https://photos.google.com/share/AF1QipNe_ak1Dk4lHUuSfwujSKazg5YoB8O78VISyl0EYbK7GiTPsLrLNWwCJvR5eKCYWQ/photo/AF1QipPIjUvin0vArFJm37Q4wybiVSNofUwaiNeuPuIC?key=YnQ4S0FrVnZrLWRVTHJ0d3RSRWpWMmF1dFZiTkdR

Any suggestions? It sounds much noisier than my other BMC, and it is not the FOC control, it continues to make the noise when the power is released, at some point it falls to a much lower RPM than the wheel, I suspect the grease is dragging the motor along at lower speed, but who knows.

Is this something important?

There has been no load on the motor yet, other than accelerating this wheel on the test stand.

Thanks for your replies.

 

[amberwolf]

What noise does it make when wheel is spun in reverse (by hand)?

What noise does it make when wheel is spun forward (by hand)?

 

[teklektik]

It's almost certainly the clutch assembly rubbing on the case.
If this is the problem, you can see a bright circular area rubbed into the case opposite the clutch as soon as you open the case.

Sadly, BMCs began having these issues with the advent of the V4 series where the clutch assembly was made a fraction of a mm thicker than the original V1, V2, V3 clutches.

Because the entire assembly is thicker than the original V1-V3 clutches, the outer face that has the plastic sprag retainer can rub on the case. This can become a problem if the clutch is torque-slammed and the plastic retainer bulges or actually breaks. In that case it stays in place and continues to work, but it no longer lies completely flat -- the damaged bit that rises up over the face of the assembly ends up rubbing on the case. The problem can also occur because of minor outer circlip/shim wear or deformation. These failures don't happen too often, but the questionable 'Sunny Day' engineering gives so little clearance that it is not in the 'impossible' category that we would expect.



A way to fix this - short of replacing the clutch - is to remove the outer circlip and shim, pull the clutch, remove the inner shim and circlip, replace the inner circlip with a thinner one if you have one, replace the clutch without the inner shim, put both shims and possibly an extra shim on the outside, then squeeze in the outer circlip. This shifts the whole clutch assembly inwards a tiny fraction of a mm and the clicking goes away.

Another option is to use a MAC gear and clutch assembly. The gears are equivalent to the BMC gears in strength/durability and the clutch is just about as strong as the V4. Importantly, the MAC assembly is built to the original BMC V1-V3 clutch dimensions - they plop right in with no issue and have the original clearance. I would request some extra shims if ordering one of these to take up any extra slop behind the outer circlip of a V4 motor.

So - you may have some other issue, but this clearance thing has bit me more than once on the BMCs.

 

[Alan B]

What noise does it make when wheel is spun in reverse (by hand)?

Thanks for the excellent responses.

amberwolf:

What noise does it make when wheel is spun forward (by hand)?

Spun forward slowly, no noise.

Spun forward fast (still by hand), same as when it coasts in the above video, every few rotations that soft rubbing sound.

Spun reverse, lots of resistance, some quiet (probably gear) noise, not much else but hard to tell over the quiet noise.

Teklektik:

Thanks for the excellent detailed response. Sounds like I'll have to either have the dealer work on it, or tear into it myself. Would it make any sense to clamp the gear assembly into the lathe and take off a little material? If there are rub marks I should be able to see them and shave off a bit more than is touching. This wheel has never been powered except on the test stand, it should not be doing this. I even picked it up from the dealer so it hasn't experienced any shipping shock. They built the wheel but I don't know if they powered it. They haven't answered my emails yet.

It also sounds like running it this way is not particularly harmful. I don't like the noise, but a bit of testing won't make it worse.

I've never disassembled a BMC, I'll have to find info on doing that properly.

Thanks again.

 

[teklektik]

I don't know about turning the planetary carrier - you'll need to look at it yourself and decide what's possible with your lathe. I'm not optimistic, but then, I'm not a machinist either... The 'shim fixes' have all continued to work - there's something to be said for simplicity.

Since you're in SF I'm guessing you got it from Ilia. He's dealt with this exact issue and so could provide some authoritative assistance. He doesn't seem to carry BMCs anymore and appears to have made the jump to eZees instead. Somebody mentioned he was working on some sort of ebike self-assistance web thingie to lighten his email and phone burden, so you might just want to swing by instead. At worst you might get some advice and pick up a couple of shims - I'm sure he still has a boatload of BMC stuff to support past customers.

Here's a link to BMC gear replacement in my Mundo Thread. It's got stuff about tools with links to YouTube and Ilia vids on HowTo. I pretty much do all the same stuff as when that was written except I stopped sealing the covers and instead drilled a vent hole aligned with the inner case edge so water gets thrown out. I had flooded motors before, now they stay nice and dry. (Hmmm... Probably should update the build thread...)

 

[Alan B]

Thanks for the update!

We're not in SF, but not far from there. We only go there when we have to.

Yes, motor is from ilia, bought some motor phase connectors from him just last week. He hasn't replied on the motor issues yet, he may be busy. He's an excellent resource and glad to hear he's dealt with this before. I may just let him do it.

My lathe is about 10x24 so I think I can swing the part, but I would have to turn a shaft to support it. I'm not a machinist either but can do some things.

Off to another project right now, but thanks again!

 

[Alan B]

I did get a response from ilia, he suspects it is one of the planet gear mounting rivets contacting the clutch body. He suggests fixing it with a replacement gear or it might require the whole clutch be changed. He indicates it is not serious and may go away on its own.

Thanks for all the suggestions.

 

[teklektik]

Hmmm - haven't seen that one, but Ilia has seen just about everything in these motors... If that's what it is, it should be harmless, if not incredibly annoying.

I'm guessing he's talking about one of the rivets that hold the metal bearing retainer discs to the plastic gear. I don't know of a way to remove a gear without pulling it or levering it off which is NG for the gear bearing. That said, if you look at the image above, you can see that all those inner rivet faces can be exposed without removing the gear by rotating the gear to the proper position. If you get super unhappy with the racket, you might pull the clutch and either peen the rivet or dress it a bit with a Dremel to get the needed clearance. Shouldn't require pulling or replacing the gear or gear bearing.

Just a thought...