I have a used Darex M4 drill grinder and the wheel flange assembly is a little odd, at least in my limited experience.
The clamping mechanism on the outside of each wheel consists of a dished flange which slips over the threaded motor arbor, a short collar, a large slotted washer, another semi-dished washer, and the arbor nut. The collar nests inside the the two washers and the nut forces that little assembly against the wheel flange. The manual available at the Darex web site shows a different clamping mechanism.
It looks like the slotted washer is intended to be adjusted to balance the wheel - does that make sense? If so, is there a procedure to use for balancing the wheel or is it just trial and error?
If anybody has a copy of a manual that depicts this assembly and/or instructions on how to adjust it, I'd love to get a copy of those pages.
If Harold reads this, I should note that both wheels have blotters on each side.
I bet the instructions are still current, though. Summarizing:
remove , outer and balancing washers and old wheel install new wheel, must have light side marked install balancing and outer washer, any screws should be firm not tight, move balance washer about 1/16" from center towards light mark then tighten screws mark where balance washer is located w.r.t. light mark assemble, test, if vibration loosen slightly, tap balance washer, tighten, reassemble .. repeat as needed
Or you can simply leave the balancing washer off and just true your wheels, maybe they'll run smoothly that way.
It is certainly possible to make a wheel balancing setup. I did one once for an eccentric (small armature) which I wrote up as:
I was recently able to largely balance a motor which had a bad static imbalance. I used a knife-edge setup as follows:
I started by leveling my surface plate carefully. If you don't have a surface plate, you can use the top of a table saw or some other flat surface you can level. I bought a piece of 1/8 by 1" O1 ground flat stock and machined a 45 degree bevel on one end. (I did this with a 12" disc sander with a tilting table - a milling machine may be much faster.) I cut the 18" beveled stock in half, giving me 2 roughly 9" pieces. I used 4 3/8-16 screws and washers as rough "clamps" on the sides of 1-2-3 blocks. I then clamped a block to the end of each knife. I lined up the knives so they were flat and parallel and level.
I then put the motor's armature (aka "rotor") on the knives. I saw that the two ends of the shafts were of different diameters. On one such motor there was a narrow area close to the rotor body where there were equal-sized shaft diameters. I used those. On another such motor I had to turn a suitable bushing in the lathe. Anyway, once on the knives the rotor with the static imbalance immediately tumbled to its position with the heavy side down. I drilled round the rim on both ends of the rotor to bring it as closely back into balance as I could, frequently checking the balance on the knives. Reassembled, that particular motor ran far more smoothly.
One more note on home balancing - it is possible to remove weight from the heavy side by drilling as just described. In a couple of cases I have not been able to remove enough weight this way and I have found a method that worked well for me, to add weight to the light side. Start with an old wheel weight. Then, on the light side, make a cone-shaped indentation with the drill (i.e. start a hole but don't penetrate through). Then take the whole thing to your kitchen, and pick your rattiest kitchen spoon. Cut off a chunk of the wheel weight about 1/4" cubic, and melt it in the old spoon, then pour it into the hole you drilled. It will not bond, but it will sit there and bead up on top and will exactly fit the indentation. Then, after everything is cool, put a drop of superglue into the indentation and then put the just-cast weight in, just as you poured it. Hold it there for 30 seconds or so. This glue worked just fine for me. I was able to make the light side just slightly heavy in this manner, and then hit the raised part of the weights with the belt sander a "kiss" at a time until the part came balanced on the knives.
Thanks - the directions on page 9 seem appropriate for the setup on this grinder and it looks like it is largely a trial and error proposition. That's fine - just didn't want to miss out on a trick that wasn't obvious.
For fine tuning, I suppose that the wheels could be mounted to a shop-made mandrel and balanced as you suggest below with balancing washer position marked so as to duplicate them on the grinder itself. That may make a lot of sense since there is a wheel on both ends of the arbor/motor shaft and trying to chase balance on both of them simultaneously could be tedious. For now, though, it seems to be running pretty well with just an eyeball adjustment on the washers. There's a small chip out of the periphery of one wheel and while the wheel seems to be otherwie solid, it should probably be replaced anyway.
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