Balancing my Verto clutch

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prop
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Joined: Fri Apr 23, 2010 2:28 pm
Location: Leeds

Balancing my Verto clutch

Post by prop » Sun Nov 04, 2012 3:17 pm

As I am rebuilding the engine I decided to have everything balanced as imbalance can cause a reduction in horsepower depending on the severity of that imbalance. As I am at the start of the engine rebuild then I thought it to be a good idea.
Everything went well until my engineer phoned me to say that he couldn't balance the verto clutch assembly as it was out of balance by 40 grams and that was too much to remove.
It could have been a bent crank but he didn't think so. I took the original assembly to him and he spun that and it was fine and when it was bolted to the crank it proved the crank was not bent. The clutch assembly was bought from Mini Spares and they asked me to send it back to them to check it out.
I got another from MED. I asked them to check it before they sent it, which they did and it was almost perfect. It needed only a little work to balance it. The result a nicely balanced bottom end that won’t soak up the horsepower
At 40 grams out of balance my engineer said it would put about 160kg extra force on the bearings. It wouldn't necessarily vibrate but would reduce the horsepower and shorten the life of the bearings.
Mini Spares sent the part back to their supplier and they sent it back to me with a report that said the Verto clutch assembly should be balanced only with the flywheel and metal only removed from the flywheel so the 40 gram out of balance was OK.
I spoke to MED about the balancing of the assembly and what I had been told and they said that if 40 grams was taken out of the flywheel it would make it unsafe. They don’t balance them together. It can be done all together but they don’t.
I spoke again to Mini Spares and to their credit they were on my side and they asked me to send it back for full credit.

I think it is an interesting story.
I am not an engineer but I would have thought that the correct way of balancing a bottom end is to balance the crankshaft and then bolt each component to it and balance that component, ending up with an assembled lump that spins within tolerance. The way MED do it and the way my engineer did.
I was thinking if you were to pick up a used flywheel that had been balanced with a verto clutch that was way out of balance, and metal taken off that flywheel. Using that flywheel with a new unbalanced verto clutch the imbalance could be tremendous.
Conclusion.
Allways get the spinning parts balanced by a reputable engineer.

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