I've re cast the bobweights, made them thinner but same diameter. Down from 840g to 760g. I can't even get it up to the 1300rpm before it wants to jump off. The aim is to get the bobweights down to 710g and make it balance correctly. 760 is part of the way there so if I mess up the balance too bad, I can fix it and then go lighter. The difference between a 44% balance factor and a 50% balance factor is about 40g so at 760g will be about 10g heavier than a 50% balance factor job done on this.
The cheap china vibration meter I use, it measures peak acceleration and the magic number there is 9.8 because that's gravity. From that, when it gets to the speed where it wants to jump up and down as well as side to side, that's a lot of extra forces on the bearings when it's in an engine. That's at maybe 1000 rpm. The total weight of the crank plus the bobweights Just over 23 Kgs. What about at 9000 rpm?
No, it's the cranks that aren't strong enough. You've got to go out and buy a billet crank.
29 сен 2024
