I have acquired a grinding wheel balancer and want to attempt to balance a flywheel. I am working on milling a mandrill for this, but have first started with using two transmission shafts to hold the flywheel. I would like to discuss the procedure for balancing. First I cleaned and lubed the balancer and made sure it rotated the best it could. I've been experimenting with a flywheel on the balancer and have found that it indeed has a heavy side. The flywheel is bare, no magnets or other hardware is attached to it. But the position that the flywheel stops in is not always the same. I spun the flywheel 10 times, each time the flywheel will slow down, down back up, stop and turn slightly in the first direction again. I marked each stopping position. You can see from the picture that the flywheel will stop in anywhere in an angle of about 90°. I figure that the heavy spot is on the opposite side of the average of these positions. I have not done any drilling yet. I will mimic the other balancing drills holes to accomplish this. Once the flywheel show a more random stopping position, the flywheel itself should be complete. Next I will weigh each magnet and grind material off the heavy magnets to equal the lightest one. I'll also check the other hardware for equal weight. the flywheel will then be assembled and tested again on the balancer. Hopefully the entire unit will be in balance. Does this sound like the proper method to balance the flywheel? Thanks Mike
Yes, that's how we do it. Your flywheel acts like it is very close to balance already. To get an idea of how much to drill you can stick small magnets on the light side to find neutral balance.
I would say you're on the right track, but when I do this, I do it with the magnets and triple gears on the assembly. I don't mess with trying to lighten or weigh magnets and always end up with a very satisfactory job of it.
I have several times balanced a flywheel with magnets using a regular wheel balancer (a flywheel is also awheel, right?).
The wheel balancer have among other fixtures a set of cones of which one of them whas big enough to fit in the center hole.
Theoretically I should be able to do both dynamic and static balancing, however, that would require drilling in the magnets - something I would not recommend, so I just did static.
(I once did both static and dynamic balancing of a Chevrolet flywheel).
BUT - that said - your approach seems right for static balancing.
Using small magnets or stick on weights is a good idea, I'll try that. The reason I want to balance the flywheel this way is, I figure if I drill the flywheel after it assembled with the extra hardware the chips will get stuck in the magnets. I am hoping that once the hardware has the same weight, including triple gears the unit will stay balanced. Although I will still check it. Let you know how it comes out. Thanks Mike
Mike: Get rid of the roll of tape and the marker. Make sure the bolts you use for the 2 shafts all weight the same, get a good set of scales. Be sure and install the dowel pins too. Make the triple gears all weight the same. The chips from drilling? That is what an air hose is for.
Do the wheels of your balance rig turn free? Be sure they do. Dan
I'm just curious - do you have a Scat crankshaft? Balancing a flywheel on a low-RPM engine that lacks crankshaft counterweights seems like an exercise in futility.
John, anyhow there is a lot of difference I can tell you!
No SCAT. I'm just attempting to improve what I have.I believe that I read somewhere on this Forum that the magnets etal should be within a gram? Mike
When drilling the flywheel I use a strip of duct tape covering the magnets and attached to the edge of the flywheel. The chips will gather on the tape and easily removed with the shop vac. This keeps them off the magnets. Remove the duct tape and continue the balancing process. FYI.
Mike, because the factory drillings are under the magnets, their balancing of the flywheel must have been done prior to the magnets being fitted. This explains why your flywheel is close to balance as it is.
My son likes to get the magnets reasonably close to the same weight before assembling, the rationale being that it all helps in the final balance.
Once the whole is assembled we balance it on knife edges, using two trans shafts as the axle. The drilling is done on the back side of the flywheel, with the assembly resting on a drill press table. The chips are easily blown off with air. The hardest part is the repeated transfer from the balancing jig to the drill press table.
Hope this helps.
Allan from down under.
Do not try to correct triple gear unbalance by removing mass from the flywheel. Balance the triple gears for equal weight and if your really anal, rotationally balance them as well but the equal weight is critical. I've seen triple gear sets with 20+ grams difference in weight. All the magnets do not need to weigh the same- match them for weight in pairs and mount 1 magnet from each pair on opposite sides of the flywheel!
Dan, I sent you a PM. Thanks, Mike
Well..... I needed about 1/2 oz of weight removal to get the flywheel to stop at random spots. One other item I noticed, is the the flywheel will now just come to a stop and will not oscillate at the end of turning. The next step was to fit the triple gear bushings (new) to the pins (also new). Each triple gear pin is 38 grams. After pressing the pins into the flywheel it's balance did not change. Next I weighted the triple gears. There is a 20 gram differential between them. How should I remove the weight from the heavist? I figure that I'd grind it off, due to the hardness of the gears. I also think that maybe I should try and take material from the entire circumference, so as not to unbalance the triple gear on it's own axis too much. I have the same question about the magnets. I want to weight and equalize the magnet weights. Again where should the material come off? Thanks Mike
On the riveted type triple gears I've balanced, I used a carbide bit with a lathe and took the material off the inside ledge below the teeth.
. Go slow. If you have a tool post grinder you might use that but the material will be tough to grind. I think you can take 20 grams off but that's about the limit. Easier to do with the newer style. BTW I personally wouldn't take stock off the outside of the teeth.
See this video at about 6:50.
Mark, I have watched those films a while ago and have forgotten about them. Thanks for bringing that back to me. Cutting off a little in this manner should not be hard. Mike
Mike, son Anthony takes weight off the end of the magnets and squares the ends up so they make good contact with the weight he uses to test their lifting power when re-magnetised.
It pays to have a couple of sets of magnets to choose from. Whack them against a vice or some such to see if they break. This will weed out the cracked ones. Then weigh all the ones you have left and work on the 16 that are closest in weight. This will reduce the imbalance in the flywheel, but you should still check the assembled flywheel balance when you have them mounted.
Hope this helps.
Allan from down under.
Allan that is what I had planned. I'm hoping to work on the magnets sometime today. I drilled the flywheel yesterday. Used a 1/2" bit (you can see the hole at the top of the flywheel) and first drilled in 1/4" (I calculated I needed 7/16" deep) tried the flywheel on the balance, then took another 1/8". I ended up with a 1/2" deep hole. Now the flywheel seems random where it stops. I also hope to face the triple gears a little later this week when I can get down to the shop. Here is a picture of the balanced flywheel stopping points, seems to be most anywhere. Thanks Mike.
I started to equalize the weight of the magnets this morning. The lightest magnet was 376 grams and the heaviest was 405. So nearly 30 grams different. The 376 gram magnet was an outlier. The next magnet was 385 grams. So I discarded this magnet and replaced it with a heavier one. This should save some grinding. In thing I learned was it is important where you setup your scale. I weighted all the magnets on my wooden work bench. Then moved the scale closer to the grinding wheel. I set it on a metal table. Al of a sudden all my magnets gained about 20 grams. The magnets were attracted to the table through the scale. So the scale was moved to a wooden table and magically they lost weight. Anyway, I used the grinding wheel to get the heavier magnets to within a gram or so of the lightest magnet, then fine tuned the magnet with my stationary belt sander. Another item I'm interested in will this grinding and heating change the magnetism of each magnet. I'll have to test them again later. Mike