Mark/Foggy Posted September 21, 2009 Report Share Posted September 21, 2009 Well the crank that snapped at the Bol D'Or has now been stripped out of the bike. So we've heard of occasional failure, but there doesn't appear to be a batch problem. This engine was boxed and delivered to the circuit in Suzuka, one let go at Croft and there was a pre-season failure for some Irish lads. From here on in we'll be radiographing a known crank and building off that. The failure was straight across the main bearing web outside of number 4, shearing away the gear to the balance shaft and alternator on the LHS of the engine. Now I've not seen the carnage yet, but when I do I'll want to be able to pinpoint where the failure propogated from. The one that let go at Croft left a grain patern that was readable, with this one I want to be able to trace exactly what happened, highlight it/stain it? Anybody help, I can get the small bit over to anybody if they've got access to any toys that I could use. And when I was joshing about that Inconol crank maybe I shouldn't - karma Link to comment Share on other sites More sharing options...
tootall Posted September 21, 2009 Report Share Posted September 21, 2009 PM on its way. Link to comment Share on other sites More sharing options...
morepower Posted September 25, 2009 Report Share Posted September 25, 2009 Well the crank that snapped at the Bol D'Or has now been stripped out of the bike. So we've heard of occasional failure, but there doesn't appear to be a batch problem. This engine was boxed and delivered to the circuit in Suzuka, one let go at Croft and there was a pre-season failure for some Irish lads. From here on in we'll be radiographing a known crank and building off that. The failure was straight across the main bearing web outside of number 4, shearing away the gear to the balance shaft and alternator on the LHS of the engine. Now I've not seen the carnage yet, but when I do I'll want to be able to pinpoint where the failure propogated from. The one that let go at Croft left a grain patern that was readable, with this one I want to be able to trace exactly what happened, highlight it/stain it? Anybody help, I can get the small bit over to anybody if they've got access to any toys that I could use. And when I was joshing about that Inconol crank maybe I shouldn't - karma Post me a picture of the damaged crank.... I used to work for DKE and I designed and made the Yamaha R7 cranks used by Virgin Yamaha, Belgarda yamaha and Yamaha moto Germany... It could be only one of 2 or 3 places that it will let go. Usually the fillet radius on the pin or main that it is usually in pins 2 or 3 not 1 or 4 or mains 2, 3 or 4.. There are also usually signs on the rods or thrust face in the engine cases of a running engine if the crank has too much flex and is liable to break. Getting them balanced does help but it is a case of making sure the pin tops are not too heavy which was a problem with the R7. I think with the cross plane crank you also need a set of bob weights making to get the thing balanced correctly... PM me and I may be able to help..... Also I know it may be a bit outside the rules but getting it plasma nitrided for an extra 45 to 90 hours may help....Normal nitirde it not going to work as it leaves too much residue which usually has to be ground on a billet crank. Plasma will just take a bit of lapping to finish it... Link to comment Share on other sites More sharing options...
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