Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing king pin bushes

Arwyn,

You may not have had any trouble with welding causing distortion on the KP tube but MMC have had, my first Morgan (a 07 reg +4) was such a car. When I renewed the KP bushes (at 15K miles) the first axle went without issue but the second one did not. On checking the axle in the lathe there was over 15 thou TIR runout at the lower end of the tube.
Fortunately Peter M at Mulfab helped me out with the supply of some bar ends of the material he used for the bushes. I made my own bushes and left the I/D small to allow for the machining. I bored the bushes in one setting and left a thou or two for final reaming. This covered your point of accuracy. Your other point about balancing is valid and was solved by bolting weights to the axle, not using a fast spindle speed also helped.
The hardest part of the whole job was cutting the lubrication grooves!!

Just seen your last post, time is not money to me so I push out one bush at a time.


Rog, Your elliptical plate will work, just as my round with flats on did. Using a press is just easier than using a draw bolt.

Well that's very interesting and prompts more thoughts. If Arwyn is correct and they start life as true, I've never needed to handle/inspect a new item, And they are in-line and accurate circumferentially, is it possible that the insertion of the bushes has distorted the tube alignment. Assuming that the tubes are supplied in tube form rather than being turned from solid bar stock they will have a weld line which will be harder than the rest if the tube. Thus any stretch distortion will not be equal throughout the total circumference of the tube and this could shift the bushes out of line with each other. and necessitate the need for them to be line reamed for final sizing and to bring them back into alignment for best function. There are a couple more options that may cause this misalignment through installation of the bushes and are we sure that MMC had issues form the welding process/assy of the hub or did it occur when the bushes were installed!

Just a suggestion but why not make the bush a clearance fit in the tube and float the bushes in position using an engineering grade adhesive? Use the pins to align the bushes whilst the adhesive cures, thus overcoming any weld distortion annoyances. Plenty of suitable adhesives out there with various gap filling capabilities and no reaming required

Whatever is going on, it's annoying that the new bushes slide perfectly over the new kingpin, then after fitting, don't!

Sounds to me like the act of pressing them in reduces the internal diameter. If there's no issue with stub axle tube alignment, would it be feasible to reduce the outer diameter to a tight sliding fit and then bond them in place using loctite or similar?

Not that it's particularly an issue these days. Back when the king pins were mild steel it was a regular job, but now everyone's switched to hard chrome pins, it's a once on a lifetime job I would think. I did mine in hard chrome back in 2006 and they've not needed doing since, about 50 or 60k miles ago.

Unfortunately your assessment falls down Sewin - the kingpin tubes are CDS (cold drawn seamless) so no weld line and therefore no distortion!

Would need to be a good grade of glue to hold the bushings in with the loads on the stub axle.

Can't see what the problem is with pressing them in and reaming them to size! It's been that way since 1910.

Interestingly, I've a Manx Norton swinging arm on the work bench at the moment, rider wants phosphor bronze swinging arm bushes making and pressing in because he feels the previous iso-elastic bushes aren't precise enough at speed....

Arwyn

Here is a used bottom bush. You can see the weld line by more marking on the top half of the bush, the left hand end in the pic. You can also feel it when using a press to put the bushes in.

No matter who welds it I would think there must be some distortion but I would assume that the chap welding the axle parts together for MMC is in a bit more of a rush than Arwyn making a repair.

Job all done and wolf hard king pins now installed. Took the opportunity to fit BRBs at the same time. They interfere with the brake flexies so I’ve had to lash up some extra protection. I’ll think I’ll give Cain a message to see what he thinks.

The job is made a whole lot easier and somewhat safe by using my home made spring compressors

All in all not too bad

Test drive later and then get the MOT booked in

I wonder if back in the day when stub axle construction was first considered, the act of line reaming the kingpin bushes solved any, within reason, distortion and runout issues of the tube, reflected in the softer bushes. Hence less need for concerns with same.

Yes I think you are spot on there Richard, I'll bet that initially they thought that installing the correct size bushes was job done! However when they discovered varying levels of binding the solution was to install oversize bushes and line ream them for fit in both diameter and alinement.