Flywheel Balancing

[dtype38]

I've been doing a bit of machining work on my flywheel and clutch and wanted to get it all balanced again. The engine builder I took it to said that to do that he also needed the crank. I was surprised so he explained that he had no way of doing just a flywheel, but with the crank he could find the balance of that, then fit the flywheel/clutch and rebalance to the same readings.

Trouble is my crank is in the engine. He said any similar crank would do as he was only using that as a mount and he could allow for any imbalance in that. So I've taken my spare crank down, but to be honest I'm not completely convinced so I've asked him to fully balance the crank first before doing the flywheel/clutch.

It's not costing the earth so I'm prepared to give it a try, but I thought each part of the assembly was supposed to be balanced first before doing the whole thing. I sort of pictured them using something like a small car wheel balancer on the flywheel, clutch plates, damper etc. Anyone offer any advice suggestions about the right way to do it and if what I'm getting done is going to be any good.

[terence]

Crank.Flywheel and Clutch should all be done together,and marked up before taking apart so they can go back exactly the way they were before being ballanced.

[tristancliffe]

Each part in the assembly should be balanced individually even when done as an assembly - the crank is only really required at this stage because it's what is used to mount everything in the machine.

We use B+E Randall a lot, and they have said in the past they prefer the crank, but do have a fake crank onto which the flywheel/clutch can be mounted into the machine with. Give them a call and see what they say, but it sounds like your engine builder doesn't really know what he's talking about.

[dtype38]

Yup, fully understand that the whole thing "should" be balanced as an assembly. If money and time weren't an issue I'd be happy to. But in clubby racing, would you really strip your whole engine down and take the crankshaft out because you'd bought a new flywheel?

[GORDON STREETER]

I fitted a new flywheel on my engine in the car, as when I was fitting a new clutch I noticed a crack starting from one of the flange holes.
This was a spare that I had that was balanced, but not to that engine.
However I run a very light alloy flywheel unlike the Jag one that probably weighs as much as my complete Anglia !

[jerryk]

Hi Ken
can you not make an alloy boss for the centre and then check it statically on a point.
Gordon my flywheel is lighter than the bottle of beer you are holding , its the crankshaft that weighs 200lbs

[THR]

http://www.wdbltd.co.uk/
these guys are good... really good... Rolls Royce Engines use um!! and of course so do we... www.incotech.co.uk

[tristancliffe]

Originally Posted by dtype38

Yup, fully understand that the whole thing "should" be balanced as an assembly. If money and time weren't an issue I'd be happy to. But in clubby racing, would you really strip your whole engine down and take the crankshaft out because you'd bought a new flywheel?

But, by balancing as an assembly, you should be left with the individual components balanced on their own too. You don't want to be using the flywheel to correct a poorly designed crank's balance. So, by the same token, you should be able to fit a separately balanced flywheel and be left with a balanced assembly. Does that make sense?

Your engine builder should be able to balance a flywheel on it's own, but may need to use a fake crank to mount the flywheel in the big balancing machine of joy.

Give Randalls a ring - at the very least you get the opinion of people that do it, and the most you find someone to actually do it for you. Win-win really.

P.S. I don't work for, and nor am I affiliated, sponsored by or otherwise involved in Randalls commercially, privately or socially, other than we send them cranks, flywheels and the like for work occasionally.

[dtype38]

Originally Posted by tristancliffe

But, by balancing as an assembly, you should be left with the individual components balanced on their own too. You don't want to be using the flywheel to correct a poorly designed crank's balance. So, by the same token, you should be able to fit a separately balanced flywheel and be left with a balanced assembly. Does that make sense?

Er, not completely, but I see what your getting at. In the case of the builder I've gone to, at least he's saying he will balance the crank first, then add the flywheel and rebalance. So this would be as you describe. Problem is that if a flywheel has been balanced on a crank as an assembly, I don't think there's any way of telling if the two parts are individually in balance, or if they're just cancelling each other out.

Anyway, good point Jerry, I must admit I was looking at it at a bit of a loss as how to mount it to do the job myself. Alloy hub would do the job. Although holding the clutch cover would be rather more difficult. Would you say the flywheel/clutch assy was flat enough to do it statically?

Thanks for the links guys, I'll follow them up.

Weight wise though, my flywheel is rather lighter than standard....

[zefarelly]

std Ford stuff is reasonably well balanced as standard so for road engines with heavy flwheels I rarely bother balancing.

I always get race engines balanced, crank, flywheel, clutch, then assembly

Its quite easy to do a static balance of the flywheel and clutch assembly though, got to be better than doing nothing

[dtype38]

Originally Posted by zefarelly

Its quite easy to do a static balance of the flywheel and clutch assembly though....

In principle yes. Sorry to be a bit dense, but in practice... how exactly?

[zefarelly]

get it concentrically mounted , spin it on some good roller bearings until it stops . . . . the heavy bit should be at the bottom . . . . stick some bluetack on the top and try again . . . . then you know how much to take off . . .or something like that . . . .

http://www.eng-tips.com/viewthread.c...=129101&page=5

theres loads on the interweb to read