R975 help

[45jim]

Perry, I'll have to check the manual (I think I lent it to you in the past) on the radial to see if there's anything unique there, but the balance for all reciprocating engines is a basic two-step process. Individual components are "statically" balanced and then the assembly is "dynamically" balanced.

I can't help feeling you already know more than I here, but a flywheel is almost always located by keyway, dowel, bolt pattern or splines so that it indexes in only one position. Low rpm engines may be exempt from this, however.

Most production engines are not dynamically balanced and merely assembled from parts that have been statically balanced and/or sorted by weight so that the engine builder can select parts to achieve a "close enough" balance. I can't say that applies to aircraft engines, I just have no experience there except with the RR meteor.

As an aside, I wonder who would be able to balance a crank like that in London, the bob weight to replace all those pistons, pins and rods would be significant and it would have to be spaced out equal to the stroke, not the type of parts you see in your local engine shop used to balancing short stroke V8's.

The only item I think you would have to be cautious of is the pressure plate, these are often not indexed and the machinist would have to mark this alignment for you after balancing.

Really I'm surprised your not doing it yourself with an electric drill, some chewing gum and a dial gauge suspended from the tailgate of your pickup. I am always amazed with what you accomplish in that garage of yours.

[45jim]

To be more clear, I don't think its advisable to balance just the flywheel/clutch assembly statically or dynamically until you can establish the balance factor. I would have to agree that the flywheel is either "neutral" or contributes to the overall balance of the assembly.

[Andrew]

When you have it balanced, they will take everything that moves into consideration, you should have no worries at all.

I have had many engines balanced, never once had a problem

[45jim]

Perry, the manual gives no information on balancing of components or assemblies at all. The only specifications are "run-out" at different levels of assembly of the crank and when the crank is mounted on "V" blocks or in the actual crankcase. There is some wording of "by selection" in the build up and I think this refers to the engine builder picking from a stock of rods, pins and crank sections. This must mean there is another manual or document that gives the refinishing tolerance for each component.

You are welcome to add the manual to your collection anytime if you would think it helpful.

[Perry Kitson]

I have the ordanance rebuild manual for the R975 C4. It does not mention any balancing procedures or checks at all.
The crank has all surfaces machined and polished, with no signs of balancing. The master rod is considerably heavier than the articulated rods, which adds to the dilemma.
I still need to know if the flywheel/clutch assembly is "neutral" before I proceed.

Perry

[Bob Phillips]

Perry,
you should be able to jerry rig up a shaft to see if your flywheel/ clutch assy is heavy on one side. I would be reluctant to have it balanced until it was checked first. Once the snow is melted you are welcome to compare your results with some extra flywheels/clutches I have here.
On aircraft engines the same crankshaft is uesed in 5, 7 and 9 cylinder engines and the only apparent difference is the size of the counter weight. Unfortunately I do not have a book telling the weights of each particular engine so don't know how it compares to tank engine....Bob

[45jim]

http://www.antiqueairfield.com/featu...arner_165.html

[Jesse Browning]

Perry. I recall when rebuilding my clutch that the different pieces were supposed to be match marked, and reassembled accordingly. Some of my pieces also had grouped holes like would be drilled durring the balancing process. Wouldent hurt to have it done again with todays better technology. Jesse.