Large king pin eyes

[DavidL]

I'm 30 years out of date on Austin 7s but my godson has a front axle with this issue.  What are the options?   I've heard of forging them back to standard, sleeves, over size pins.  I've also heard of racing cars with pins made of different material.  How much of the chit chat is sensible and doable?  

David

[fatcatvera]

Various oversize kingpin sizes are available. I got a set from David Cochrane and used an adjustable reamer to open the axle and bearings to the correct size. 

Ray

[Dave Wortley]

I don't think sleeving is safe. The axle eye area hasn't enough metal round it. Ian Dunford might still be repairing axle eyes and other axle repair magic.

[Ruairidh Dunford]

I have now taken over the engine and axle repair side of the business, Ian continues with the other services however.

I offer axle eye repair to standard and lowering axles to original sports pattern, normal turn around is a couple of weeks from delivery to me.

See here for contact details: http://www.albaaustins.co.uk/

Ruairidh Dunford
Alba Austins

[Bob Culver]

Loose eyes have been a Seven attribute forever, esp here where many roads were endlessly corrugated metal.
With the pre Girling stubs oversize kingpins are inconvenient as a blind reamer is required.
The time honoured method for Sevens is to red heat the eye and forge smaller. The metallurgical aspects are dubious especially on the nth repeat. May contribute to cracking often evident where the H section begins. However sure to have been done at some time.
For other makes for modest stretch a bead of weld is used to shrink. Despite room for much more metal the eyes are very small for the later heavy cars. A general reinforcing with weld seems prudent.
(In NZ, despite the improved safety, welding is not allowed for 6 monthly w.o.f so has to be disguised)
 

[Stuart Giles]

As Bob says above if the kingpin eye isn't grossly oversize. stick or MIG welding around the otside of the eye will shrink it enough to be able to ream it to the original size.  Here's a couple of photos of a Big 7 axle I did a few years ago.
 this one is with the welds  dressed off prior to reaming back to standard size..



Edit: correct photo inserted above.

[Jamie]

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.

[Bob Culver]

One of the first things you discover when arc welding is the surprising distorton which occurs on cooling. The contracting metal exerts a very strong force. If a bead is laid along a heavy strip it will curl the strip toward the bead. At least with larger kingpins not too loose,  a bead around the eye is sufficent to contract the heat softened eye. (For quality repairs of general engineering items successive  beads were often peened after to expand the metal and reduce distortion and locked up stress)

[Stuart Giles]

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.

[Jamie]

Thank you for the explanations: it makes total sense, now. I have encountered warping and bending when welding sheet metal enough in the past that I should have realised how the shrinking would work.

Jamie.