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Forum Index : EV's : Electric motor- rotor- cooling fin broken

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toppar11
Newbie

Joined: 26/12/2011
Location: United States
Posts: 5
Posted: 08:30pm 26 Dec 2011
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Hi, I need to repair a damaged rotor used in a Miele dishwasher water circulation pump. As you can see in the attachments one of the cooling fins is chipped and the other completely broken off, which I have. I think the fins are aluminum. This rotor is sitting on letter size paper to give scale.

Does anyone know if it is possible to repair this using some type of epoxy adhesive? I cannot find a replacement easily, the part is Miele and anyone who knows is hard to replace. I am repairing this motor pump for an older person. Thanks. Cheers.








 
Gizmo

Admin Group

Joined: 05/06/2004
Location: Australia
Posts: 5078
Posted: 10:29pm 26 Dec 2011
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The motor should work OK with that broken fin. Motors are designed with more cooling than is needed for normal operation, this allows for hot climates, dust build up, etc. So I dont think the missing fin will affect its ability to keep itself cool.

Vibration may be a problem though. If it had a even number of fins, I would break off the fin on the opposite side to give it some balance. But it looks like you motor has a odd number of fins, so you cant to that, as there are two fins on the opposide side to the broken fin. So you can either....

1. Gently file down the opposite two fins by half each. Easy but sacrificing more cooling ability.

2. Add weight to where the fin is missing.

I would go for number two. Find a small self tapping metal screw thats slightly heavier than the broken fin, then drill a hole to suit and screw in the self tapper, with some good 24hour epoxy on the thread.

Glenn
The best time to plant a tree was twenty years ago, the second best time is right now.
JAQ
 
toppar11
Newbie

Joined: 26/12/2011
Location: United States
Posts: 5
Posted: 04:39pm 27 Dec 2011
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Hi Glen, cheers for this reply. I actually have the broken fin. I should have shown it in the images.

I was wondering if anyone knew of an epoxy that is best suited to adhering the fin bake on. Surely there must be something for aluminum. I was told something like Loctite 680 may work but I wanted to check.

I would hate for the fin to dislodge if it was not properly fixed.
Cheers!
 
VK4AYQ
Guru

Joined: 02/12/2009
Location: Australia
Posts: 2539
Posted: 12:25am 28 Dec 2011
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Hi Topper

You could drill a hole in the fin and the base and dowel it together with a steel pin with epoxy in the hole, there is a product called Devcon alloy weld epoxy you could build up around the fin to reinforce it and put some opposite to balance the assembly.

All the best

Bob
Foolin Around
 
toppar11
Newbie

Joined: 26/12/2011
Location: United States
Posts: 5
Posted: 05:06pm 28 Dec 2011
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hi bob. cheers this is what i was thinking. i know its small but the miele pump is $1,045 brand new and the motor itself is 120v compared to uk-euro. i was revbuiding it with new rubber hosing etc. but the rotor was damged in the processs.

3m have an epxoy so ill try this method you suggest.




Thank you for contacting 3M, the Innovation Company. We have some epoxies that may be suitable for your application.

DP-460 is a two-part, room temperature curing epoxy. It has a 60 minute worklife and reaches handling strength in 4 hours. It comes in a cartridge and is dispensed through a hand-held applicator.

If you only need a small quantity of adhesive and don't want to invest in an applicator, you may want to try Scotch Weld 2216 Gray. This is another two-part, room temperature curing epoxy. It has a 90 minute worklife and reaches handling strength in 10 hours. It comes in a variety of bulk sizes, such as a two ounce tube kit. This product is mixed by hand.

The technical data sheets are attached. If you have any questions, please let me know.

Regards,


Barb S.
3M Customer Contact Center
Product and Application Support
Industrial Business
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Warpspeed
Guru

Joined: 09/08/2007
Location: Australia
Posts: 4406
Posted: 11:44pm 28 Dec 2011
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I would not worry about the broken fins, or the effect on balance.

You can feel the weight of that iron rotor, and the weight of the broken off fin, which is absolutely negligible in comparison to the weight of the rotor.

It is not going to dangerously overheat, the loss of a fin (or two) will hardly matter.
Most of those small motors have no fins at all, and work fine.
The pump only works for very short periods anyway.

Just put it back together and it will run for many more years, if the bearings are o/k.
Cheers,  Tony.
 
toppar11
Newbie

Joined: 26/12/2011
Location: United States
Posts: 5
Posted: 02:09pm 29 Dec 2011
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hi, great cheers this is what someone else recommended. it was concerning to think an epoxy may not be safe. i have ordered a new bearing and need to push down the shaft slightly as the back bearing was incorrectly replaced/damaged. thanks for your help
 
Tinker

Guru

Joined: 07/11/2007
Location: Australia
Posts: 1904
Posted: 02:13pm 29 Dec 2011
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I agree with Tony above, the pump is at most running around 3500RPM (60HZ). Not at all like the 10,000+ RPM's some power tools run at and which do require to be carefully balanced.
Having a glued on fin fly off while the pump is running might be much worse than a slightly unbalanced rotor.
Klaus
 
WindyMiller

Regular Member

Joined: 05/04/2011
Location: United States
Posts: 62
Posted: 10:01pm 30 Dec 2011
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Hi Toppar11, I would just put the thing back together and leave it at that. Like mentioned above, trying to reattach a fin to the rotor could result in serious damage to the stator if it comes apart while in operation. However if you are dead set on gluing the fin back on? I think JB Weld has something that would work? Would have to look in your local autoparts shop or online. JB Weld I do experiments with AC motors as Induction Generators and have had a few accidents in the past. Most of the time one missing fin is not going to make much difference as the rotor is a good flywheel and helps with keeping the rotor balanced.

RobertEdited by WindyMiller 2012-01-01
 
toppar11
Newbie

Joined: 26/12/2011
Location: United States
Posts: 5
Posted: 01:05pm 02 Jan 2012
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hey, great that has saved me a lot of worry. i was not happy about gluing the fin back on and was looking to purchase a new rotor which was difficult. thanks for your replies. happy new year
 
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