Lotus Elan and Lotus Elan Plus 2 Forums

Hi guys, I'm a bit confused by the pile of restored bits for the front uprights of my Elan. Everything is stripped.
Both uprights are in good condition and I have ordered new brass trunions, but I cannot work out which upright belongs on which side of the car. One Trunion has a left hand thread which goes into its brass trunion the other a right hand thread, Which is which? Seems a dumb question I know, so please make me feel worse!
Thanks.

I can't see what difference it makes, but I have always worked on the principle of left hand thread on the left and right hand thread on the right.

When you turn the steering the trunnions move up and down the vertical link depending on which way you turn. Swapping them over will just result in the up and down movement reversing

I have now fitted Canley Classics ball joint conversion so that all that trunnion play and movement has gone.

The Elan workshop manual states that the upright and trunnion with left hand threads are fitted to the left side and vice versa.

Gosh, I got it right

Can't see this in my manual, so it must be in the earlier ones.

stevebroad wrote:Can't see this in my manual, so it must be in the earlier ones.

I found this in the S1 workshop manual, it is not in the later manual for my +2.

But, does it actually matter? Would it matter if you fitted 2 left , or right, hand units?

stevebroad wrote:But, does it actually matter? Would it matter if you fitted 2 left , or right, hand units?

Well if you think about it, when you turn left, one side of the suspension shortens by about a half inch and the other side lengthens by that half inch. so the car tilts slightly to one side which might be beneficial or anti-beneficial when cornering. And it does the opposite when you turn right.

I raised this same question here last year, as to whether the designers had taken it into account, but no-one else seemed to think it would be noticeable. But suspension was one of Colin Chapman's own specialities, was it not? So I'll bet he took it into account in deciding which side to put the left-hand-thread.

If it didn't matter at all, I think they would be both right-hand threads. Or perhaps both one-hand for RHD cars and both the other-hand for LHD cars.

This topic raises a slightly different issue. I found my old used trunnions in a box here; how can I tell if they are less worn than the ones presently on my car?

Should I melt them down and so turn them into interesting bronze sculptures, instead of worrying.

billwill wrote:

stevebroad wrote:But, does it actually matter? Would it matter if you fitted 2 left , or right, hand units?

Well if you think about it, when you turn left, one side of the suspension shortens by about a half inch and the other side lengthens by that half inch. so the car tilts slightly to one side which might be beneficial or anti-beneficial when cornering. And it does the opposite when you turn right.
.

Half an inch? The thread pitch is 10 to the inch. So, lock to lock the suspension will turn about a 1/4 of a revolution of the trunnion so around 1/40th of an inch, which is why I ask if it matters about having handed uprights.

Chapman may have been a great designer but he didn't deisgn the Elan front suspension, Triumph did that. He just modifed it to suit the Elan

billwill wrote:Should I melt them down and so turn them into interesting bronze sculptures, instead of worrying.

Or, clean, polish, chrome and mount as an ornament or lamp

stevebroad wrote:

billwill wrote:Should I melt them down and so turn them into interesting bronze sculptures, instead of worrying.

Or, clean, polish, chrome and mount as an ornament or lamp

Why would one want to put chrome bling on beautiful bronze???

stevebroad wrote:

billwill wrote:

stevebroad wrote:But, does it actually matter? Would it matter if you fitted 2 left , or right, hand units?

Well if you think about it, when you turn left, one side of the suspension shortens by about a half inch and the other side lengthens by that half inch. so the car tilts slightly to one side which might be beneficial or anti-beneficial when cornering. And it does the opposite when you turn right.
.

Half an inch? The thread pitch is 10 to the inch. So, lock to lock the suspension will turn about a 1/4 of a revolution of the trunnion so around 1/40th of an inch....

...which is ? mm, so Bill has thought in mm but quoted in inches. The Americans made the same sort of mistake and missed Mars.

>

which is ? mm, so Bill has thought in mm but quoted in inches. The Americans made the same sort of mistake and missed Mars.

Nah, I thought it moved more than that. I'm not sure that pitch is 10 per inch, I think it is multi-start thread with a coarser pitch, but I won't know for sure until I take a look at an upright and a trunnion some time in the near future.

Thanks to everyone for the advice.

With the pitch of the thread measured and confirmed at 10TPI and the maximum rotation of the steering at a generous estimate of 90 degrees, it would change the front suspension level by plus and minus 0.635mm x 2 or 1.27 overall (as one side goes down the other rises by a similar amount). That has always work on the Spitfires and the like, so no problem there.

From my perspective, I like to do things by the book and with advancing years I find the simple things easier to remember, so for me it is going to be LH thread on LHS and RH thread on RHS.

I certainly hope that after all the effort and parts put into the front suspension I will not need to strip this again once the car is back together. Not in my lifetime anyway!

AFRICAELAN007 wrote:
From my perspective, I like to do things by the book and with advancing years I find the simple things easier to remember, so for me it is going to be LH thread on LHS and RH thread on RHS.

Just the same as the hubs....easy ain't it..

John