# Balancing my rotor (or a flywheel)



## Bogstandard (Mar 11, 2008)

I was going to put this in with my turbine build, but thought it might do better here.

Due to mass demand, one really, I am going to show how I do a Heath Robinson balance on this rotor I have made. It should and does work equally well for flywheels.

I make no excuses to anyone about how I do it. All I know, is it works very well for me. If it works for you, great, if it doesn't, I'm sorry. You will have to find an easier or better way if you can.

I start off with the bit to be balanced with its bearings on (if free enough) dropped into a pair of v blocks that are totally parallel and at the same height, and hopefully near enough level that it isn't worth bothering about. Then I just give it a couple of spins and it usually stops at the same place. This means that the heavy spot is at the bottom, so mark the top to indicate the light spot.








Now get a lump of play dough (didn't someone mention about playing with this stuff when he was making an elbow engine, shame on you Cedge) or blutack and stick it at the light mark that you have made, and spin the rotor. If the dough ends at the top again, you haven't got enough on, if at the bottom, too much. Now play about, adding or taking away until the rotor stops in no particular position. Now we do a test. Spin it a couple of dozen times and mark the top position it stops at. If you are lucky you will have a complete ring of marks. If you notice after doing this test, there is a little bare patch with no marks, put a tiny amount of dough directly opposite the bare patch, and do a few more trial spins to see if the patch is starting to get dots in it by stopping at the top. Adjust the tiny bit until it does. You should now be able to clean the marks off and do the trial spins all over again and you should get marks all round. You now have a balanced rotor, and you can use it like that if you can guarantee the dough is never going to come off, otherwise go to the next step.







Mark the rotor in a bright colour directly opposite where your little blobs have ended up. A big mark for the big bit and a little one if needed.







Now comes the really technical bit. Raid a crack house or mug the local drug dealer and pinch their drug weighing scales. But be careful some of them can be real naughty boys. If you already have a set, I won't ask.
This is the really, really technical bit now. Pop the biggest bit of dough into one side of the scales, and balance it out using the chips from when you were machining the flywheel.







Pour the pile of chips out and have a look at them when heaped up. Thru experience I can look at the pile and say roughly how much material is in there (approx half the volume you are looking at). We are not going to be drilling holes, but only the points of the drill. I broke mine down into four seperate piles and decided that there were about two drill points worth in each pile. Not wanting to drill a ring of eight dimples, I decided I would put four on each flange end, directly in line with each other. This might seem that my rotor is way out, not so, even a couple of thou difference in depth on a few of the buckets can cause this amount of out of balance. If you have got just a tiny amount, you might get away with just one dimple.







Now by eye I transferred the bright mark to the other flange and put a mark either side of it, these are going to be my first drill pimples. Only two at each end at first, it is easy to take off, harder to put back. I used my rotary table because it was already set up for holding the rotor, but it can be done freehand on the press or miller. Just cut the dimples at your marks and retest the balance (still with the little blob of dough on there). If it goes nowhere near, put another mark either side and put very shallow dimples in. Retry for balance. It is a matter now of just a tiny bit out of a dimple, then try it. once you start to get very close, remove the bit of dough, drill a tiny amount out of the dimple nearest the mark for the opposite of the tiny bit of dough, and try again.







Now is the time to start marking the ends by spinning them again. Spin it up, mark the high point, repeat a dozen or so times. If your notice my pic you will see that there was a gap starting to form in the blue marks. If this shows up like this, drill a tiny amount out of the holes nearest to the gap. Change colour and retest, keep removing tiny amounts until you get your latest colour giving a full, but repeating random circle. When this is achieved, it is balanced (or good enough in my case).







Clean it up and smile. A job well done.







It took me longer to write this article than it did to balance the rotor. It took about an hour to do the rotor and my material to remove calculations weren't far out either.

Your little friend the engine will thank you for doing this to it's flywheel, it will purr with satisfaction.

John


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## tattoomike68 (Mar 11, 2008)

That post is great ,thank you for taking the time to show part of the great things you do. :bow:

Bog you impress me to no end, keep up the good work.


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## Bogstandard (Mar 12, 2008)

Mike,

You are welcome. I just hope it was not too complicated to follow. But I couldn't find an easier way to describe it.

John


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## steamer (Mar 12, 2008)

Very Clever John

I'll keep that in mind.....


Dave


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## Mcgyver (Mar 13, 2008)

nice post John, I like the weighing of the chips, far more scientific that drill a little bit and check it again! I made a balance to assist with a Kub Car competition once, complete with weights, this is a great application to save it from lifetime of being stuck under the bench.


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## Bogstandard (Mar 13, 2008)

Actually, my grandson bought these scales for me from a boot sale for about 50p ($1). but I have found numerous uses for them over the years. This method might look a bit like alchemy, but it does get you very close to what is needed.

John


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## DickDastardly40 (Mar 13, 2008)

On the subject of balances (sometimes called scales), I vaguely remember 'a helicopter is born' on the discovery channel and the guy used a steel ruler (also sometimes called scales) balanced on a knife edge pivot as a rudimentary balance (or scale) which worked quite well.

Al


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## Bernd (Mar 13, 2008)

Bogstandard  said:
			
		

> Actually, my grandson bought these scales for me from a boot sale for about 50p ($1). but I have found numerous uses for them over the years. This method might look a bit like alchemy, but it does get you very close to what is needed.
> 
> John



What? Your not turning lead to gold.  

 :big: :big: :big:

Bernd


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## Bogstandard (Mar 18, 2008)

Bernd,

The impossible I do at once, miracles take a little longer.

An old saying from somewhere in the distant past, but a sign to put in your workshop, just to let people know you are trying your hardest.

John


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## snowman (Apr 5, 2008)

that is AWESOME


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