clacking noise from hub motor mounted as mid-drive

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All,

I have a hub motor mounted as a mid-drive, to a left-side crank (Stokemonkey). I was tightening the chain from the motor to the left chainring yesterday and after tightening, noticed the cap-head screws that hold the motor cover on were hitting the frame when I tested it. This was with enough force to gouge the (aluminum) frame. I had to take a couple of links out of the chain to shorten it and then re-tightened. It was not terribly tight. Now, I have a clacking noise coming from either the motor or the freewheel when it is under any strain. When running with the tire off the ground or peddling backward, there is no noise. It is at a pretty high frequency, many times per revolution. I think it is either the freewheel or something in the motor is hitting many time per revolution. I did not ride the bike when the allen screws were hitting the frame. Just ran it with the wheel off the ground and when I saw the problem, adjusted immediately. The fact that it gouged the frame, however, indicates it was more than simply brushing the frame.

Any ideas? How to troubleshoot? Have looked closely and nothing external is hitting now.

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If anyone is following this thread, I talked to the manufacturer and the most likely problem is the freewheel. They indicated I have gotten many times the normal use out of the one I have, which is the original. The noise doesn't seem to be coming from there but I have found that second guessing a good mechanic is a bad idea. I will probably replace the freewheel and see what happens.

[John in CR]

Undo the chain and spin the motor to see if the sound disappears.

[itchynackers]

Bearing?

[d8veh]

It could be the chain jumping on the sprocket, which is what I had. It did it even after I added a chain tensioner. I guess there was a mismatch between chain and sprocket. It isn't as easy to see as you think. It's easy to check - just remove the chain and slow the motor down with your hands to put it under load.

[Warren]

You need a new chain, and a new freewheel. Buy a quality, 1/8" freewheel, and 1/8" heavy duty, BMX chain. Buy a chain checker.

http://www.parktool.com/product/chain-checker-cc-2

[Philistine]

What type of hubmotor is it?

I am interested in this thread because I am having the exact same problem with a hubmotor. This is a HS3540 mounted in a 26inch wheel, running on 12S.

I previously had this motor in my Greyborg on 20S@50amps, and never had an issue.

I then moved it into my daily commuter, and after getting all the torque solutions right, everything worked, but what happens is, after a ride of perhaps 5km, the motor starts "clacking". But it only does it under power (never without power). It is a mechanical clacking noise that occurs rythmically with the rotation of the motor under power (when no throttle is applied, the noise never happens). At first I thought perhaps the disc brake caliper was somehow banging against the hub when under power, but I removed the caliper completely, and it still does it.

Although I have not taken the motor apart, the bearings seem fine in terms of waggling the motor side to side produces no movement (ie the bearing seem to be pretty tight).

My only guess is that one of my bearings are damaged, and what is happening is that when I apply power, the stator is being pulled sideways and the sound is the stator banging against the inside case of the motor?

What is most weird, is that it doesn't do it for the first half of my commute, but at almost the very same point everyday (in terms of my commute) the clacking starts up. It is clearly a mechanical noise (and feel), so in my opinion it has to be either the bearings failing and causing the axle to rotate in a non-level way, or the stator banging against the case, I can't work it out otherwise.

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One of the posts (JohninCR) gave me an idea. Since until the motor was strained, there was no clacking, running the motor with the wheel off the ground or turning the motor by hand or spinning it backward with the pedals did not result in the symptom. However, reading John's post, it occurred to me all I needed to do was to load the motor without loading the freewheel. So with the chain still on the freewheel, I used a narrow board to wedge between the motor and the bike frame and put strain on it. No matter how much or where on the motor I loaded it up, it was as smooth as silk.

There is still a possibility that loading it via the chain (which is far off the center of the motor) might cause a bad bearing to catch or a stator to hit a rotor and that I could not replicate this with my experiment. However, I did lever against the motor in several positions off the motor centerline to add torque to the bearings and housing and I pushed pretty hard so I am reasonable sure it is not in the motor itself.

If I can get a freewheel locally, I will try replacing it this evening. If not, it will be several days.

Philistine, it is whatever motor Stokemonkey uses, which I have been told is a 400 series Xlyte. The noise is not like I would expect a bad freewheel to sound; it is louder, more of a clacking than a ticking, and I can also feel it in the pedals. I also originally assumed it was something in the case hitting, like one of the magnets, but from my experiment and after talking to the technician at Clever Cycles, I think the freewheel is the most obvious choice. Will report when it is replaced. If I can get it apart, it will be interesting to see how it failed.

As far as removing the freewheel, the technician indicated that using a freewheel removal tool doesn't work well because you can't get enough torque on it to get it off. They use a drift in the splines to knock it loose. I suspect that if I could hold the motor well and if I used an impact wrench, it would come off, however. I have removed a freewheel before (not from a hub motor) and I can verify that they can be SOBs to get off. I suppose 5000 miles of screwing one on makes it hard to screw off.

[Philistine]

Thanks PDF, for me it is not the freewheel, it is definately in the hub itself. I will just have to pull it apart and have a look. I suspect it is stator against case, but I could be wrong.

[d8veh]

What type of hubmotor is it?



I then moved it into my daily commuter, and after getting all the torque solutions right, everything worked, but what happens is, after a ride of perhaps 5km, the motor starts "clacking". But it only does it under power (never without power). It is a mechanical clacking noise that occurs rythmically with the rotation of the motor under power (when no throttle is applied, the noise never happens).

It sounds like a faulty phase wire connection - especially if you have the bullet type, which can spread and lose tension. That's also a possible cause for PDF's problem.

[Harold in CR]

I think Warren has it figured out. When I was building my mixed breed POS, I had that same clacking noise. I had built a home made sprocket out of a 10" sawblade. I had it looking REAL close to perfect, but, it would try to ride up a tooth and then slam back down into the bottom of the gullet, between teeth.

Your chain is under much tension and riding up the teeth just a bit, then slamming back, same as what Warren explained. Need new chain and sprocket-freewheel. MAYBE.

[Philistine]

It sounds like a faulty phase wire connection - especially if you have the bullet type, which can spread and lose tension. That's also a possible cause for PDF's problem.

No it is definately not electric related. It is definately mechanical. I have thought hard about this. The only reason I might entertain it being phase wire related is the fact that it increases after a ride(possible because the wires are becoming hot, and hence splitting further if that is the case?). But the sound very much sounds and feels mechanical.... Having said all of that, as you say, that would explain the delayed onset. Maybe there is damage to the phase wires and as the magnetic force builds, the interference starts?

Very strange, I igive up

[pdf]

You need a new chain, and a new freewheel. Buy a quality, 1/8" freewheel, and 1/8" heavy duty, BMX chain. Buy a chain checker.

Never seen a chain checker before. I have just used a tape measure, but the chain checker would be nice.

I know when the CleverCycles people replace the stock freewheel, they use a different brand than the original, which is a Shimano. On the other hand, the original went pretty far.

[d8veh]

It sounds like a faulty phase wire connection - especially if you have the bullet type, which can spread and lose tension. That's also a possible cause for PDF's problem.

No it is definately not electric related. It is definately mechanical. I have thought hard about this. The only reason I might entertain it being phase wire related is the fact that it increases after a ride(possible because the wires are becoming hot, and hence splitting further if that is the case?). But the sound very much sounds and feels mechanical.... Having said all of that, as you say, that would explain the delayed onset. Maybe there is damage to the phase wires and as the magnetic force builds, the interference starts?

Very strange, I igive up

I had it on my bike. It started after I tried to go up a very steep hill without pedalling. After that it did it after about 30 secs of riding. Switching on and off seemed to reset it for another 30 secs. I was convinced my motor was broken because it made a loud mechanical clacking noise and juddered at the same time. After crimping the phase wires a bit tighter, it runs like new. Just before the first event
, I had been experimenting with my controller and disconnected it several times which is what loosened the connecctors.

[John in CR]

Philistine, your problem sounds like a loose magnet.

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Philistine, your problem sounds like a loose magnet.

Maybe a loose screw...

Just kidding; it was too easy.

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But seriously...

I had to order a 16t freewheel. Bikeshop said it should be in today. Will probably attempt weekend repair. Also am on the hook to build three bookcases for spouse. Anyone want to switch lives, Sat. and Sunday?

[lbz5mc12]

It is probably the freewheel. My freewheel on my 500W hub motor made a clacking noise and I could actually kind of wiggle it a little bit.

[hydro-one]

loose or cracked magnet........i second that , cause i think its happening to me too.... http://endless-sphere.com/forums/viewtopic.php?f=2&t=42253&p=617836&hilit=broken+magnet#p617836

strange i had some rubbing on my side bolts too.....mabye that broke magnet??

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Not the freewheel; replaced it this weekend. Getting the old one off was surprisingly easy. I am going to replace the motor-to-crank chain just because it is the only simple thing left. After that, it looks like bearings or the rotor and stator hitting are the only choices. Does not sound like a bearing issue.

Called Clevercycles after freewheel replacement did not help. Troubleshooting over the phone pretty much impossible. The Stokemonkey has been out of production since Oct. 2011due to parts issues and they have no parts to replace. I was told they have an agreement with a motor vendor for a new custom motor. If I can't fix this one and I can get a good deal on the new motor, I will go that way. However, I think I could find another motor to fit the bracket, as long as it would clear the downtube and seat stays in the rear triangle. However, unless my spatial reasoning is messed up, either the covers are swapped (freewheel mount on the left) or the Stokemonkey motor turns backward. Also, the axle is cut short so it doesn't stick out the sides of the bracket. It is also tapped for a cap-head screw to hold it in the bracket instead of an axle nut.

[John in CR]

A freewheel and normal right hand threading works properly as the driven sprocket on the right side. Flip it over to the left side for it all to work as the drive sprocket.

That's why you have to look out for the pedals with the chain on when trying new wiring combos for an in-wheel hubbie. If you happen upon a reverse, the freewheel isn't free and the pedals can whack the hell out of you.

[pdf]

You need a new chain, and a new freewheel. Buy a quality, 1/8" freewheel, and 1/8" heavy duty, BMX chain. Buy a chain checker.

Turns out Warren was spot on. Looks like the chain had worn to the point where it was making noise on the sprocket somehow. It was not jumping completely, which I've seen with a regular right side chain, but the rollers could have been riding up slightly and then popping down into the valleys on the sprocket. I got a new chain today and when I took off the old one, I laid it next to the new one. For the same length, the new one was 73 links and the old was more like 71. That is pretty severe chain wear. The rule of thumb for freewheel/chain issues is that they are usually changed at the same time, particularly when one is badly worn, since it can cause the other piece to wear more quickly if not caught soon.

Often in jobs like this, several things are changed when the symptom appears, and I sometimes don't focus on the correct change. In this case, apparently, it was tightening the chain that started the problem, but at the same time, I had the issue with the hex bolts hitting the frame and I assumed that could have caused a more serious problem.

What I have learned is that there are several problems that can cause noises of this sort. Unfortunately, my problem is only a problem for mid-mounts and doesn't apply to hubs in general.

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As an interesting followup, after changing the chain and the freewheel on the middrive, my energy use per mile has gone down noticeably. When I first got the bike, it would average between 16 and 18 Wh/mile. Before I changed the freewheel and chain, it had increase slowly over the last year to about 21 Wh/mile. Now is is under 18, around 15-16. Seems hard to believe a worn chain/freewheel would cause that and maybe it was a coincidence, but I didn't change anything else that I know of.

By the by, previous to changing the freewheel/chain, the Wh/mile would tend to creep up over time. I frequently don't bother to reset the CA until I have over 100 miles and with each trip, following the same route every day, the Wh/mile would creep up until I reset it. I haven't had enough trips since I changed the freewheel and chain to see if it still does that. At any rate, changing those components shouldn't change a short term steady state value for the energy use. Anyone else experience this?