07-07-2019, 08:55 AM
(06-07-2019, 11:22 PM)Jamie Wrote: Happy as ever to show my ignorance. How does welding the outside of the eye shrink it? Does the heat of the welding expand the metal in such a direction that the eye reduces in diameter? Or am I barking up the completely wrong tree?
Jamie.
It's the shrinkage on cooling that closes the kingpin eye. My first photo isn't great quality as the camera has focussed on the background, so maybe it's not clear that the weld beads run vertically. the beads partially overlap, alternatively running top to bottom and then bottom to top. The aim is to have the eye properly red hot at the end of each run without the metal burning; wait for the eye to cool a bit before the next run. The current I have used was about 160A with my MIG welder or about 130A with my DC stick welding setup. I've done this process on a fair few axles without any issues, I got the technique from a blacksmith who did this process (using huge current) to shrink truck axle eyes with a stick welder. I've never had any problem of pins shooting loose after doing this. Not sure whether that's because I finish ream the eye to be quite a tight fit on the pin after welding, or whether it's because the welding adds a fair bit of material to the kingpin eye, so increasing it's rigidity; I suspect it's a bit of both.