and those 4 holes won't weaken the crank nose too much??? looks really interesting... that thing isn't going anywhere!! :lol:
I did a similar repair, but with just two holes. As long as the key can't start moving due to the pins it should be fine. Four holes looks like overkill to me.
Quote from: "commuter boy"I did a similar repair, but with just two holes. As long as the key can't start moving due to the pins it should be fine. Four holes looks like overkill to me.I thought that originally too...but then I read other people's stories. First they tried one, then two. Finally by the third it seemed to be OK. There is a LOT of force that causes them shear in the first place - because on the one hand you have the crank bolt which is supposed to be around 77ft/lbs + 1/4 turn and THEN you have the 7mm key. It takes a lot of force to shift the cog and shear off the key. And I do agree with you partly. The cog must not be permitted to move even a little. I don't know if you've ever tried it but on a clean nose and new cog, there is very very little movement maybe one quarter of one degree. Unfortunately that is why we're here. Even that little amount of movement could not overcome those forces I mentioned earlier. The idea behind using 4 pins is pretty simple really. Take equal loads across the geometric span of the cog - not in one or two places.Though we'll see. Believe me I don't want to be proven wrong here, not because of my ego - but because I just rebuilt everything and another failure would mean 3 cylinder heads. :roll:
The other thing to look at is making sure the end of the crank is perfectly flat to mate with the gear when it's bolted down tight. My dad's been noticing some of them aren't exactly flat, which might cause more wobble, especially if a less than perfect torquing procedure is used on a new bolt.If you're going to this much trouble, and you're that risk adverse I would have thought you'd pull the crank and machine a TDI shaped D on the end of the crank nose matched to a gear to a light press fit.Do keep up posted as to how the fix works though, I'm curious.
That is just a pulley, not a harmonic balancer as there is no rubber or mass to dampen out the harmonics.