Cromotor issue... bad sound and lack of power

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brumbrum
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Cromotor issue... bad sound and lack of power

Post by brumbrum » Jan 19, 2018 10:57 am

Here’s the low down
Cromotor, all good for past 2 years until now. added ferrofluid And hubsink, took for test ride, ok for 15 minutes doing hard start stops up to 120 amp to help heat motor and check temps. All good and then the sound came along. It happens with any sudden amp increase but not so if very gently upping amps, there is also loss of power when the noise happens as if a clutch is slipping. It also makes the noise when using regen braking. I think adding the ferrofluid is just a coincidence and not the cause. I had to take one side panel off the motor to add the ff, but it was the side that does not have the phase wires, just the spare set of halls.
Is it a phase wire issue? Or something else?
Two 30 second videos (ignore the footage)
first with sine wave....
https://youtu.be/f0UwjVRRer0
Then with sensorless activated on the adaptto....
https://youtu.be/Gzv24CltOcs

I will have to crack open the phase wire side of the motor to check.

Any help pointing me in right direction, or any experience with same symptoms is much appreciated in replies.
Thanks
Andrew

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Re: Cromotor issue... bad sound and lack of power

Post by Buk___ » Jan 19, 2018 11:04 am

brumbrum wrote:
Jan 19, 2018 10:57 am
Here’s the low down
Cromotor, all good for past 2 years until now. added ferrofluid And hubsink, took for test ride, ok for 15 minutes doing hard start stops up to 120 amp to help heat motor and check temps. All good and then the sound came along. It happens with any sudden amp increase but not so if very gently upping amps, there is also loss of power when the noise happens as if a clutch is slipping. It also makes the noise when using regen braking. I think adding the ferrofluid is just a coincidence and not the cause. I had to take one side panel off the motor to add the ff, but it was the side that does not have the phase wires, just the spare set of halls.
Is it a phase wire issue? Or something else?
Two 30 second videos (ignore the footage)
first with sine wave....
https://youtu.be/f0UwjVRRer0
Then with sensorless activated on the adaptto....
https://youtu.be/Gzv24CltOcs

I will have to crack open the phase wire side of the motor to check.

Any help pointing me in right direction, or any experience with same symptoms is much appreciated in replies.
Thanks
Andrew
Could the ferrofluid be causing the clutch rollers (or sprags) to stick?

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Re: Cromotor issue... bad sound and lack of power

Post by skeetab5780 » Jan 19, 2018 11:23 am

No clutch in a bldc direct hub

Did you mark the side cover and make sure to install it in the same manner?

Sounds like maybe a magnet broke loose

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Re: Cromotor issue... bad sound and lack of power

Post by brumbrum » Jan 19, 2018 11:49 am

skeetab5780 wrote:
Jan 19, 2018 11:23 am
No clutch in a bldc direct hub

Did you mark the side cover and make sure to install it in the same manner?

Sounds like maybe a magnet broke loose
Yeah , i know theres no clutch, just has sensation like clutch slipping.
Yeah i marked the side covers and installed the same.
Yeah, did occur to to me it could be loose magnet caused by the ferrofluid and high temp.

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Re: Cromotor issue... bad sound and lack of power

Post by fechter » Jan 19, 2018 3:21 pm

It sounds like all the magnets broke loose. They can spin around on the inside of the hub, only held on by magnetism. If the glue gets hot enough, it weakens significantly. Ferrofluid could possibly be a factor, but most glues used to stick magnets to the motor should be compatible with it. It would have a tendency to lubricate the interface once the glue fails.
"One test is worth a thousand opinions"

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Re: Cromotor issue... bad sound and lack of power

Post by ridethelightning » Jan 20, 2018 1:51 am

same happened to me. all loose magnets.
glued back with locktight speedbond epoxy, so far so good, ~2 years later.

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Re: Cromotor issue... bad sound and lack of power

Post by Buk___ » Jan 20, 2018 2:50 am

brumbrum wrote:
Jan 19, 2018 11:49 am
Yeah , i know theres no clutch, just has sensation like clutch slipping.
Sorry for the apparently dumb question.

I have a geared hub with a clutch, and have been wondering whether it would be compatible with ferrofluid.

I saw mention of "clutch slip" and didn't know a cromotor was a DD.

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Re: Cromotor issue... bad sound and lack of power

Post by brumbrum » Jan 20, 2018 7:05 am

ridethelightning wrote:
Jan 20, 2018 1:51 am
same happened to me. all loose magnets.
glued back with locktight speedbond epoxy, so far so good, ~2 years later.
Darn! What a pita. Looks like a complete strip down. Just as i am in the middle of building a new battpack with 30Q's.
Ferrofluid does not seem like such a good idea now.
@RTL, do you use ff with the locktite?

Cheers guys.

@Buk, not sure to be honest, but if you are getting a geared motor so hot that you need ff you are probably going to melt/chew up the nylon cogs, and are probably wildly over amping and overvolting the motor. Or you may have your wiring incorrect. My motor gets too hot to hold my hand on the surface... 130 degrees C

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Re: Cromotor issue... bad sound and lack of power

Post by Buk___ » Jan 20, 2018 7:56 am

brumbrum wrote:
Jan 20, 2018 7:05 am
@Buk, not sure to be honest, but if you are getting a geared motor so hot that you need ff you are probably going to melt/chew up the nylon cogs, and are probably wildly over amping and overvolting the motor. Or you may have your wiring incorrect. My motor gets too hot to hold my hand on the surface... 130 degrees C
At the moment I'm only using 20A @ 36V and the motor temp is staying pretty much at ambient.

But. I'm about to build a 48V pack and my controller is good for 40A(*); so I was just thinking about options for the future. The ferrofluid would cool the stator, and perhaps help stop the gears over heating; but I am concerned about its affect on the clutch. Hence my question if that was your problem.

But all that is off-topic in your thread now I know that you don't have a clutch. Sorry for the noise.

(*I'm not intending on using it all, but there are people who have been running my motor at 1200-1500W for extended periods without problems. If FF wasn't going to create other problems, I might have added it just as a preventative measure.)

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Re: Cromotor issue... bad sound and lack of power

Post by brumbrum » Jan 20, 2018 9:42 am

You'll find you dont need it. If for instance you have 500w rated motor, you will only see peaks of 1200+w for a couple of seconds even on hills when first accelerating. 500w is the constant power rating that it can handle continuously all day long. My cromotor is rated 6000w continuous and with peaks of twice that, its only used for off-roading and therefore lots of stop start accelerating and steep hills, therefore it gets hot as it does not do much 'cruising'.

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Re: Cromotor issue... bad sound and lack of power

Post by brumbrum » Jan 26, 2018 4:04 pm

Just an update to this thread. It turned out that all the magnets in my motor had come loose due to adding ferrofluid. This is not the fault of the ff but of the cromotor glue used on the magnets.

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Re: Cromotor issue... bad sound and lack of power

Post by fechter » Jan 26, 2018 8:24 pm

I've seen several reports of motors where the magnets all came loose. None of them were using ferrofluid. If you have good epoxy, the ferrofluid should not be an issue.

To re-glue the magnets, you need to really work at getting the surfaces clean since any oil residue will prevent good adhesion.
"One test is worth a thousand opinions"

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Re: Cromotor issue... bad sound and lack of power

Post by brumbrum » Jan 27, 2018 9:25 am

Sure, i do now have my work cut out for me cleaning the 46 magnets and the hub ring. Then time to rebuild and add new statorade.

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Re: Cromotor issue... bad sound and lack of power

Post by ridethelightning » Jan 28, 2018 7:59 am

be VERY careful when handling the magnets- dont let them clack together, they will crack!
cracked magnets cannot be repaired.
always store them with cardboard/something soft between them, think carefully when handling them.
good luck.
RTL

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Re: Cromotor issue... bad sound and lack of power

Post by fechter » Jan 28, 2018 8:34 pm

If the magnets aren't marked, it's a good idea to mark them before removing them. Every other one is north. When replacing them you have to alternate between north and south.
"One test is worth a thousand opinions"

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Re: Cromotor issue... bad sound and lack of power

Post by brumbrum » Feb 01, 2018 2:58 am

ridethelightning wrote:
Jan 28, 2018 7:59 am
be VERY careful when handling the magnets- dont let them clack together, they will crack!
cracked magnets cannot be repaired.
always store them with cardboard/something soft between them, think carefully when handling them.
good luck.
RTL
Learned my lesson there when cracking the first magnet i moved. Realised straightaway that yoi must slide them in and out of position. Thankfully a friend had a couple of spares.
fechter wrote:
Jan 28, 2018 8:34 pm
If the magnets aren't marked, it's a good idea to mark them before removing them. Every other one is north. When replacing them you have to alternate between north and south.
I numbered them 1 to 46. Though i also noticed that they repel if trying to mount them the wrong way next to each other.
Its going to be a big job starting today as i finished my battery build last night. It may take a couple of days of patience.

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Re: Cromotor issue... bad sound and lack of power

Post by fechter » Feb 01, 2018 9:30 am

For sure it can be a messy job to glue in the magnets. Glue tends to squirt out when the magnet sticks to the rotor iron. I always use the slow setting kind of epoxy that gives lots of time to reposition things and wipe up excess before it hardens.
"One test is worth a thousand opinions"

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Re: Cromotor issue... bad sound and lack of power

Post by brumbrum » Feb 08, 2018 2:47 am

Just a quick update. Magnets all now re-glued. Spot the spare magnet,, the only one i snapped when first removing.
Image

Was good to service the stator whilst out.
Image

I refixed the temp wires and halls with refresh gasket sealant. No rust whats so ever. Put everything back together using threadlock for all screws and thin layer of sealant on covers. I have also added a small gauze pressure valve on one cover and added new statorade.

Still not out of the woods, need to do road test at high temp. I used a loctite speedbond adhesive with an activator spray to help strength and cure. Not too messy but was very quick drying. Luckily the last magnet was a snug fit.

My advice to anyone doing this is to have something plastic to push the magnets out of the hub ring so they slide out and also to slide them back into postion. They snap really really easily. When removing from the ring have something to slide them onto which is magnetic, i had a filing cabinet and lined them up about 2 inches apart sticking out from the edge of the cabinet so they could be easily pulled back off. Strong magnets have to be the weirdest objects i have ever worked with and will catch you out in unexpected ways.

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Re: Cromotor issue... bad sound and lack of power

Post by Lebowski » Feb 08, 2018 3:05 am

Congratulations with post nr 1000 !

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Re: Cromotor issue... bad sound and lack of power

Post by brumbrum » Feb 08, 2018 10:49 am

Lebowski wrote:
Feb 08, 2018 3:05 am
Congratulations with post nr 1000 !
Haah, yeah,, i seemed to have rounded things up quite nicely!

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Re: Cromotor issue... bad sound and lack of power

Post by skeetab5780 » Feb 08, 2018 12:09 pm

Good job man seems that Cromotor is getting its worth, every penny! How many miles on it?

Should be good for another season now

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Re: Cromotor issue... bad sound and lack of power

Post by brumbrum » Feb 09, 2018 2:44 am

skeetab5780 wrote:
Feb 08, 2018 12:09 pm
Good job man seems that Cromotor is getting its worth, every penny! How many miles on it?

Should be good for another season now
Got to be close to 1k miles, but only used for off roading on weekends. Its taken a beating for sure. As long as my adaptto maxe controller doesnt crap out again it should be good for some time yet.

Image

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