Well that TD crankshaft would have quite a tale to tell if it were a sentient being. In addition to being marked .010/.010 on one side of the number one & two throw, it was marked .020/.020 on the other side , but it was an obviously welded-up crankshaft because the main and connecting rod bearings were standard size as previously mentioned, and a closer inspection revealed the center main thrust surface was also welded. Whoo-eee that’s a lot of welding and grinding. Of course it’s not the most radical crankshaft repair we’ve ever seen, because this one is:
Seeing is believing. What you’re looking at is a reconditioned Laystall crankshaft for a 14 HP Lea-Francis. It’s an archival photo from an earlier engine rebuild. Incredibly the rear main bearing journal and flange are spliced into the rear counterweight, and we have it on very good authority that it ran like this for many thousands of miles before the subsequent regrind that you’re seeing here. This is a remanufacturing tour de force, in my judgment.
We didn’t end up using it, but not out of disrespect for the anonymous engineer who managed to pull it off. It is recorded in the literature that about 15% of the strength of an XPAG crankshaft journal is imparted by the radius and in our experience many of the broken or soon to break cranks (as determined by a magnaflux inspection) we’ve seen have suffered at the hands of a machinist who was too lazy to dress his grinding wheel properly. The radius on this Laystall crankshaft is quite a nice one, I think, however if you click on the picture for a really close look you can see it must have been the Devil’s work to grind it, probably because of the neatly spigoted into the rear counterweight immediately ahead of it..
So let’s back up to XPAG wrist pin clamp bolts for a moment. These are not accessable with a normal socket wrench. There is a factory tool for the job (18G 327) which I’ve never seen, but a cut-down 3.8″ drive socket suffices pretty well. we actually have two, a 5/16″ BSF socket to take the old ones out, and a 13mm socket to put the new replacement bolts in. In the first photo above we have the piston clamped in the vice using a pair of aluminum spacers which hold the pin tightly without damaging the piston.
What we now know is last week’s con-rod bearing meltdown was probably a serendiptous event because the clamp bolts wern’t even tightened past about 15 foot pounds of torque out of the recommended 33 ft lbs. and when these let go the results are frequently catastrophic.
In other news, Butch got a move on today with the long dormant Spitfire 1500 which is recently arrived from Texas for some reconditioning.