Building a 57 DA10 bottom end. There should be about 3 thou float. Two questions. As the drive side is bolted up solid and shimmed, why worry about float clearance as it won't float anyway. If it does need shimming on timing side What shims do we use as none are shown in parts book and they would be bigger diameter than drive side. So should there be a thrust washer as A65? Any info gratefully received. Forgot to mention that it has had a new MB bush reamed to size. A solid brass one.
You only need to shim on the drive side, the reason for the clearance is the crank will grow in the cases (its believed the cases will grow faster than the crank, but I'd destroyed 2 needle roller bearings proving different) when you measure the crank for end float the roller bearing (which would have been standard on your A10) needs to be bolted up tight, you should measure .003" from this point.
Sorry can't comment on the thrust washer with the A10
[quote=Allan Gill]...when you measure the crank for end float the roller bearing ... needs to be bolted up tight, you should measure .003" from this point.
In "Building Budget Brits" Brown talks about doing this on an A65 by using a section of old fork tube and a washer to substitute for the rotor. But something in the back of my mind kept asking why? I've never quite understood where the play comes from in the first place. The light came on when I read your statement. Or at least I think it did.
Am I correct in thinking that the Crank and inner bearing are locked together by the rotor and nut on the drive side. So the TS Bush is really only supporting the weight of the crank.
Where is the play in the system, that shims limit to .001-.003?
Is this play within the roller bearing? Or play against the TS thrust washer? Both? Or am I missing the concept completely?.
Since thicker shims move the crank closer to the TS, some of the play must be the thrust washer/bushing interface. On the other side of the thrust washer is the bush with spiral grooves, oil directly from the pump, and the crank with oil groove and passage to center of crank. Is that why this tolerance is so critical, because if over .003 the risk is leaking oil directly to the case from the thrust washer thus starving the rest of the engine?
Shims are listed in the parts book. They are fitted between the inner race and the crankshaft. The drive side is not bolted up tight as the roller race just slides into the outer in the case. The inner race is bolted tight. The timing side of the crank has a thrust face which bears on the flange of the bush. You have to get the end float right, I try for around 0.001". It is a painful job setting it as you have to assemble, measure, then usually remove the inner race to shim then do it again.
I don't know where you find steel that grows faster than ally....................
Yes when both at at the same temp then the alloy will have expanded more and this is the case on a warmed up engine. Problem is during the warming up, if the heat gets to the crank before the cases eg piston to con rod to crank then for a short period the crank could be warmer and wider than a tightly shimmed crank in the cold alloy cases will allow without binding.
One thing I did not see mentioned in this string was OIL, DO NOT attempt to set end float with any oil on the face of the bearings. A film of oil can easily throw your measurements off at least one thou. I do not know where the .003" end float target came from. It is incorrect and should be .001. Definitely grows as the motor warms up.
Roller bearing came off nicely . Adding up all my shims comes to28 thou for a gap of 3 thou. or one 30 thou shim for a gap of one thou. I'm inclined to use the 30 thou shim and expect the sealant to give me another thou clearance. I also think with the roller bearing the shaft will be free to move as it does not bolt up tight. Thanks fro your forbearance. Merry Christmas and a happy new year.