Supension legs -lack of!

Post by **bigginger** » Fri Aug 15, 2008 11:27 pm

Is that a sleeve that screws on to the trunnion which has a thread so worn that it's unsafe? I'm sure there's a flaw in that somewhere, just can't put my finger on it...

Post by **BMC1** » Fri Aug 15, 2008 11:36 pm

Nooo- this is a workshop job. The sleeve would be steel with a tight thread, then welded and ground back at the end. It'd be a permanent modification- not a baggy sleeve held on with glue.
The reason for even thinking about it would be if it was impossible to restore the existing thread. Which it isn't.....we hope.

Post by **Dean** » Fri Aug 15, 2008 11:37 pm

I'd cut off the old thread and shaft, bore a hole in the end where the thread once was. Turn a new thread section on a shaft that could be press fit into the bored hole. Dowel it at 90 degree for added security.

Thread could be replaced and replaced and replaced each time they wore out.

Post by **BMC1** » Fri Aug 15, 2008 11:44 pm

Not a half-bad idea!

Would have to bore up into the leg some way to be happy that the new section wouldn't part company from the leg. Will have to look at a live one to see if it's practical, but it's an attractive option.

Post by **Dean** » Fri Aug 15, 2008 11:47 pm

bmcecosse wrote: Seriously though - it must be possible to make new king pins from EN24 bar stock and just machine them to size. CNC once programmed would do it in minutes!

It is, I'd guess you could turn each one in about 15 minutes, another fifteen for the milling. Less if there was a big batch. Thirty minutes at £50 to £60 per hour (the approx charges for CNC rates). A one man band in a shed with a small set up £30 per hour.

Post by **aupickup** » Sat Aug 16, 2008 9:18 am

the company i work for charge cnc work at £125.00 per hour

Post by **Dean** » Sat Aug 16, 2008 9:37 am

aupickup wrote:the company i work for charge cnc work at £125.00 per hour

Wow, cheers for that, makes for a whole different story!

I take it you probably have some sophisticated, expensive machinery!

Post by **Dean** » Sat Aug 16, 2008 9:49 am

BMC1 wrote:Not a half-bad idea! Would have to bore up into the leg some way to be happy that the new section wouldn't part company from the leg. Will have to look at a live one to see if it's practical, but it's an attractive option.

Cheers BMC1, yes I agree the bore depth would probably have to be three or four times the shaft dia. This is also the reason why I suggested it was doweled. Like previously suggested a tough EN24 or EN24T material would prevent cracking. The only problem I could see is a potential for the original leg to be a bit weaker around the bored area. If it does weaken it, you could press some kind of sleeve over the outside of the leg to help support the leg more.

Another option could be instead of a press fit into the original leg with dowel, perhaps a screw thread? But you would need some kind of tommy bar hole in the thread that goes into the trunnion in order to get the thing in and to get it out when it wears? Hey hey I'm on a role now!!!

Post by **aupickup** » Sat Aug 16, 2008 9:53 am

well its a 5 axis cnc machine

but this one is for purpose made joinery

investment is very high

u can get 2, 3, 4 axix cnc machines so may be smaller engineering shops will charge less, but i would still reckon about £80.00 to £100.00 per hour

the club spares has some undersize legs and trunnions

i was lucky enough to have a couple of pairs of original legs, i bought a while back from an auto jumble, also some old stock trunnions

spares are particualy a problem with the poor morris minor

wonders how long this goes on for

i wonder how many cars, vans, pick ups, travellers , convertables are waiting for legs for the mot

i feel we must have an alternative approach to this, but how i dont know

saddened from eastbourne

Post by **MoggyTech** » Sat Aug 16, 2008 10:32 am

Given that BM used to have the old kingpins reworked surely that must have been re-metaling and new thread cut. It's a proven method that obviously works. OK your car may be off the road for a month or so while the work is done, but still better than waiting 8 months for new units.

Some good ideas put forward in this thread though.

Current spares situation is a bit of a worry. 5 years ago the only bit that was hard to get was a first motion shaft and 2nd gear assembly. Now even eyebolts are out of stock.

Post by **paulhumphries** » Sat Aug 16, 2008 10:48 am

Don't forget liabilty insurance for whoever reconditions legs for these therorectic ideas. They would need to submit them for inspection / tested to destruction before they could get cover and then probably pay a fortune in premiums which could substancially add to costs and therfore make it non viable.
After all one failing leg could kill and the potential payout by an insurance company could be enormous so suspect thet would be reflected in enormous premiums. I think that rules out the one man band in his shed.
I reckon the only people who would be prepared to undertake such recondtioning are the big companies who already do similar work on other components and have a "track record" of quality to be able to afford the insurance cover.
Maybe it's time the club approached such a company to see what they can offer ?

Paul Humphries

Post by **MoggyTech** » Sat Aug 16, 2008 10:49 am

Update:

Just spoke to one of my contacts at one of the major suppliers.
Recon kingpins should be available within a couple of weeks, delay on these was due to a tooling die for LH thread needed replacing.

New kingpins have been cast, and are back in the UK and have passed the crack test, so machining will start any day now.

Further, the suppliers are aware that the spares situation for critical items like this must be addressed.

So in the words of Captain Mainwairing Don't Panic.

Post by **alex_holden** » Sat Aug 16, 2008 10:55 am

As soon as new ones are available I'm going to buy a pair to stash away in case this happens again and they are unavailable for months when I need them.

Post by **millerman** » Sat Aug 16, 2008 11:09 am

As a non- specialist can anyone tell me if is there a good engineering/strength reason why there should be a left hand-thread on the left(?) leg?

The actual reason for this rather than a guess

Post by **Dean** » Sat Aug 16, 2008 11:54 am

Re-metaling, I have seen this done, it took ages though to add a few thou onto a job. It goes on like melted metal via what looked like a gas welding gun (similar to spraying). Good idea and would work.

Post by **minor_hickup** » Sat Aug 16, 2008 12:16 pm

This is how the king pins are reconditioned!

Post by **MoggyTech** » Sat Aug 16, 2008 1:04 pm

millerman wrote:As a non- specialist can anyone tell me if is there a good engineering/strength reason why there should be a left hand-thread on the left(?) leg?

The actual reason for this rather than a guess

Complete mystery from an engineering perspective. For example, if you turn the steering to right lock, the RH kingpin screws down into the trunnion, while the LH kingpin screws up the trunnion. The movement involved in the vertical plane is tiny so it wouldn't have geometry benefits such as raising the loaded side of the car to improve road holding.

Post by **millerman** » Sat Aug 16, 2008 4:04 pm

So, presumably, all recon/new kingpins could be manufactured at less cost by having right-hand threads??

Post by **bigginger** » Sat Aug 16, 2008 4:11 pm

Hmm - if it ain't broke... I'm pretty sure the designer will have done it for a reason, which I'd always guessed to be the height remaining constant during turning

Post by **bmcecosse** » Sat Aug 16, 2008 9:10 pm

It is the constant height thing - would show as heavy steering one way as it lifts the car and light the other as car goes down. But the effect must be tiny and i would say they should all the RH thread and then only one set of top and bottom trunnions would be needed! The stub axle should still be LH thread to prevent it trying to unscrew as the hub rotates.