Lotus Elan

Track Rods - Post '72 MG Midget

PostPost by: AlfaLofa » Wed Mar 13, 2013 12:00 pm

I remember a posting which suggested that the track rods from a post '72 Midget would fit an Elan.

I thought I would find out.

I bought a '73 rack for a tenner on Ebaaay and then compared the track rods with those on an old Herald rack I had lying around.

The measurements:

Herald
Overall Length 185mm
Ball Diameter 26.4mm
Ball Centre to Rod end 175mm

Midget
Overall Length 162mm
Ball Diameter 26.4mm
Ball Centre to Rod end 152mm

The thread of the Midget rod takes a new track rod end I had bought from SJSportscars - and the track rod end screws onto the track rod to give the prerequisite Workshop Manual distance of 7.59" between the centres of the two balls.

The photos show the Herald and Midget track rods side by side.
Attachments
002.jpg and
003.jpg and
Steve
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PostPost by: john.p.clegg » Wed Mar 13, 2013 1:19 pm

so are you happy with the amount of thread in the ball joints??

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PostPost by: AlfaLofa » Wed Mar 13, 2013 1:38 pm

About 35mm of thread (1.4") is in the ball joint - which judging by the residual rust is the same as when the track rod was fitted to the midget.
Steve
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PostPost by: ricarbo » Wed Mar 13, 2013 3:24 pm

According to Brian Buckland, the Elan rod has an overall length of 6 and 5/16 inches, which I make 160.3375 mm., very close to the Midget size you quote. Perhaps the important thing is whether or not there is enough of the rolled thread to allow the lock nut to be fully on the thread when the tracking is set right.
Looks to me like it's a great solution to the apparent non availability of original rods.
I have just converted a new old stock Herald rack and reused the rods from my original rack, due to this non availability. Unfortunately for me the Lotus rack I had was a rebuilt unit and the spacers were wrong, giving me tyre clearance problems (MOT failure), and I found it hard to find anyone who would make me some - one joker quoted ?200 to ?300. Eventually got it done for ?40.
I recollect Mini rods were said to be suitable, but don't know the details.
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PostPost by: AlfaLofa » Wed Mar 13, 2013 4:10 pm

Richard,

The total length of the thread on the midget track rod is about 46-47mm - so there is still about 10-12mm left for the lock nut.

It's rather tight, but I've just measured the lock nuts I have and they are about 7mm deep - so a bit of leeway, but not much.

Perhaps the thread needs extending (non rolled) a couple of mm or so.

Also,

I was thinking about having a tubular spacer made for a spare rack.

I presume ?40 was just for the tube - was it a perfect fit?
Steve
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PostPost by: ricarbo » Wed Mar 13, 2013 9:03 pm

Well, if there's enough rolled thread for the locknut, that sounds an ideal solution. I can't see a problem with an extra bit of cut thread for, say, half the locknut thickness, maybe somebody more expert can. Perhaps it weakens the rod to cut extra thread?
After four month's of fruitless enquiries and false starts. I eventually found a retired engineer to make the spacers, via pals in the Caterham 7 club. He remains an enthusiast. Interesting chap, used to work for Caterham and was responsible for getting the bump steer down to the minimum for them. He was happy to make the spacers and made them to fit my rack. The internal bore was smaller than Brian Buckland's figures, to give a closer fit. A sliding fit over the rack, rather than a very loose fit. He also lapped the old rods to the new rack's rod housing nuts, to ensure a long lasting result.
I found it very difficult to find anyone who is prepared to make a simple bit on a lathe, for a reasonable price. It's all CNC stuff today with prices to match. Hard to find anybody with a machine in the shed at the end of the garden. At one point, I was semi seriously thinking of looking to buy a lathe to solve the problem. I suppose if you bought one second hand and sold it after you'd used it, you might lose nothing or even make a profit, but you'd spend some long time learning how to use it, and it would be a lot of bother.
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Richard
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PostPost by: Quart Meg Miles » Fri Mar 15, 2013 10:18 am

ricarbo wrote:Well, if there's enough rolled thread for the locknut, that sounds an ideal solution. I can't see a problem with an extra bit of cut thread for, say, half the locknut thickness, maybe somebody more expert can. Perhaps it weakens the rod to cut extra thread?
Richard


A rolled thread work-hardens the material whereas a cut thread creates potential fatigue failure points. But the light steering of a road-going Elan is going to provoke that.

Good research, Richard, good to find an alternate source. I believe there is a thread or link on this site to fettling new racks so that they are free and easy. I bought two brand new ones and they were unbelievably stiff and I took the spring out and shimmed it for minimal clearance but they didn't last long.

My present rack was second-hand from a +2 and (without the spacers) I can only just achieve the correct toe-in before the thread runs out, in fact I'm hard on it and have to wind the ball joint onto the locknut. Anybody know the source of the basic +2 rack, perhaps a BMC Spridget? However, it has done me 30 years and 100,000 miles and has just a tiny bit of play now.

GENERAL NOTE ON LOCK NUTS.

The normal double-nutting of lock nuts, using a half-nut (and not applicable here), is usually implemented wrongly: the half-nut should be fitted first and the whole nut fitted on top. The inner half-nut is more-or-less a washer as it bears the wrong way round on the bolt's threads, if at all, in order to jam the outer nut.
Meg

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PostPost by: ricarbo » Fri Mar 15, 2013 5:48 pm

Having got all excited about this, I looked on the Moss Europe site, but they show the track rods as 'no longer stocked'. Shame. Still, there must be more second hand ones around.
The credit for research goes to Steve, not me.
I have always understood there is no difference in Elan and plus 2 racks other than the plus 2 has an extension fitted on the track rod, but have no first hand experience. I believe they are both Herald units modified by the lock limiting spacers and track rod only. Otherwise standard and different from other Triumph racks, such as the TR4 etc, which are different length racks, therefore giving bump steer.

I've heard that comment on lock nuts elsewhere and am not sure if I can get my head round it when I ponder which of the two nuts you put the torque wrench on! I used to think - put the full nut on first, to the right torque and then the half nut just lightly nipped up. I wouldn't have thought that alters the force exerted by the two nuts very much.
If you put them on with the half nut first, then you can't torque it for fear of stripping the thread. You can't effectively torque the full nut to clamp the parts together either, because it will be stopped by the half nut, except for the tiny initial movement when the half nut stops acting to clamp via one side of the threads and becomes effectively a washer, floating, until it presses on the other side of the threads, whereupon it blocks the full nut. If you think my reasoning unclear, I'm not surprised.
Confused? yes, that's me!
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PostPost by: AlfaLofa » Fri Mar 15, 2013 6:01 pm

I did a quick search for used Midget spares earlier today:

http://www.mgcars.org.uk/andyjennings/m ... eering.htm

http://www.mgbreakers.com/Midget.html#Steering

Late racks seem to be ?20
Steve
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PostPost by: Quart Meg Miles » Sat Mar 16, 2013 11:15 am

Quite right, Richard, I had meant to credit Steve but had just read your post!

On lock nuts I had quoted from my memory of an info sheet by Zeus, I think it was, but even as I typed it I wondered about the torque setting.

If the half nut is first on the thread then some of the main nuts torque goes into pushing the half nut against the thread, but how do you judge that? The only need for a lock nut is if the load disappears and allows the nut to become loose on its thread. So a superimposed half-nut needs to be tensioned hard enough to push the whole-nut against the opposite side of the thread; how much torque is needed on the half-nut to do that?

I now reckon the only solution is to put on the main nut first, to the specified torque, then fit a spring washer before the half-nut which simply compresses the spring. If the load goes slack the spring washer takes up the thread movement of the main nut. So why not just fit the spring washer?

I think I'll start a thread for this (but not for a month as I'm away again)! Are there any lock nuts on the Elan, it seems to be built around Nylocs and Stovers?
Meg

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PostPost by: MickG » Sat Mar 16, 2013 12:39 pm

Clutch slave cylinder push rod springs to mind.

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