by Skywatcher » Sat Jan 18, 2020 1:55 pm
Hi J
What I have done before, although I told the customer that there would be no warranty expressed or implied on the repair, was to epoxy the loose magnet back onto the flywheel. If you can see exactly where the magnet came from and what its orientation was (sometimes they will have a factory mark like a white line indicating this side out), the magnet can be re-attached to the flywheel. The backside of the magnet and the inside of the flywheel must be thoroughly cleaned with emery tape and washed down with brake cleaner before proceeding to the next step.
Here's where I strongly recommend the use of a non filled slow curing 2 part epoxy resin like Devcon 2-ton Epoxy in the two 1/2 ounce tubes, one tube of resin and one tube of hardener. (J.B. Weld is a filled epoxy and behaves more like a very hard filler putty as opposed to a high strength glue). Back in England, the go-to brand of epoxy resin was Araldite with the resin in the blue tube and the hardener in the black tube (if memory serves me correctly). Make sure you have a method of securely clamping the magnet to the flywheel during the gluing process. Prepare the epoxy resin following the directions on the packet to the letter, apply the mixed resin to both surfaces and clamp tightly. A little bit of squidge out isn't going to matter as there's adequate room and let the glue cure for 24 hours.
Once the glue has fully cured, check the clearance between the stator and the magnets. Set a single layer of electrical tape over laminations of the stator. install the flywheel and rotate the crankshaft, the magnets should not touch the tape. Add a second layer of tape onto the stator and repeat, you should see scuff marks on the top layer of tape. If no scuff marks on the second layer, add a third layer and repeat. The top layer of tape should be peeled off by the magnets. Most electrical tape is about .005" thick and I believe the stator to magnate clearance specification is .008" to .012". Hope this points you towards a possible repair option.
If the repair doesn't work, you haven't lost much. If the repair does work, you've just saved your customer's snow blower. All the best,
Sky
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A person who cares about what he sees and does is a person who's bound to have some characteristics of Quality.
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