Lotus Elan

alignment

PostPost by: Lotus 50 » Mon Feb 11, 2019 12:29 am

My Plus 2 has very little self centering in the steering. Is this normal or is my alignment off? The alignment was last done 20 years ago when I had my chassis replaced. I have a vague memory of being told that the alignment was set to the 'limit' and still not quite right. I suppose it's possibly my replacement chassis was not perfect.

In the spring when I take my Plus 2 out of storage, I'm going to buy new tires, and I should get an alignment.

If they can't get it right, am I stuck or are there easier options than removing the chassis and trying to bend it.
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PostPost by: mbell » Mon Feb 11, 2019 1:01 am

Self centring is related to caster that isn't adjustable. Likely either chassis isn't quite right it maybe have an issue with the suspension arms.

What type of chassis is it? Galvanized?
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PostPost by: Lotus 50 » Mon Feb 11, 2019 2:07 am

It's a pre galvanized Lotus chassis.
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PostPost by: vincereynard » Mon Feb 11, 2019 7:56 pm

4 wheel tracking is the only way to get an idea what may be wrong.

As mbell has stated it is generally to do with front wheel castor. Which is not easily adjusted. You can pach the top wishbone/trunnion joint but it is a bit of a bodge.
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PostPost by: JonB » Mon Feb 11, 2019 8:38 pm

A few points:


  • You can make minor improvements to the castor by packing the top ball joint and lower arm with washers like this http://www.lotuselan.net/forums/lotus-suspension-f42/oversteer-corners-t41214-120.html#p290617. This will not make much difference in terms of castor angle and it puts extra stress on the king pins - but it should improve it.
  • If the rear is riding high it will reduce the castor angle very slightly. Check the rear ride height.
  • Put the right sized tyres on it (diameter). This will mean the existing castor angle has more effect, if your present tyres are too low profile. (Due to the distance between the pivot point and the contact patch being longer, there should be more leverage.)
  • Check tyre pressures. If they are too low the steering is heavy and the self centring has more force to overcome.
  • Make sure the car is tracking right (front and rear suspension - rears need adjustable A arms to alter tracking). This will help steering greatly.
  • Get a 4 wheel alignment check so you know what the suspension parameters are.
  • Get the front alignment set, then see how it drives.

These tips may or may not help your self centring, but will help your steering if the alignment check shows something is out of kilter. I have exactly the same problem with the Spyder chassis on my +2, with low profile tyres (too small a diameter) and rear tracking out of spec. I am waiting for Spring before making my A arms adjustable (too cold in the garage right now!).

Let us know how you get on!

Cheers
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PostPost by: 69S4 » Mon Feb 11, 2019 9:13 pm

Any plans on how you’re going to go about the adjustable wishbones project Jon? I’ve got a set I want to do the same with but I’m holding back on picking up the hacksaw until I’ve got a better idea about the process.
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PostPost by: Esprit2 » Mon Feb 11, 2019 9:52 pm

With upper & lower ball joints, using washers to shim the upper A-arm assembly back, and the lower A-arm assembly forward, will increase the caster. In turn, more caster will help the steering self-return to straight ahead; and it will also result in heavier steering feel.

However, the Elan +2 (Seven, Elan, Europa) doesn't have a lower ball joint, and the trunnion has zero ability to accommodate changes in caster. The steering axis must remain inline with the trunnion's designed-in/ built-in steering axis. The 'design' caster angle is built into the chassis by tilting the front cross-member/ tower assembly back, off-vertical at an angle equal to the intended caster angle, then welding it to the chassis. From that point onward, caster is built in, correct or incorrect, and not adjustable. If the chassis was built wrong, there isn't an easy adjustment fix.

Forcing a caster change by shimming A-arms forward & back just puts the trunnion in a bind, increasing stress on it, and shortening service life.

Of course, if the chassis was built correctly, but the suspension arms were incorrectly installed off-center, with the upper A-arm forward and the rear A-arm back, then the error would reduce the caster. That would result in less pronounced self-centering, and would introduce it's own bind on the trunnion in the process. IF that's the case, then correcting that caster error would involve removing the upper and lower A-arms, and re-installing them correctly. That would have the additional benefit of removing the bind that has been on the trunnions. If you get that lucky, then you should immediately head for a casino.

Do get the alignment checked in the Spring... at 20 years, it's past due. But don't expect the alignment shop to be able to do anything about built-in caster that is out of spec.

*~*~*~*
Pulling to one side or the other isn't the same as not self-centering. Pulling can be the result of other out-of-alignment issues that might be correctable through adjust... even a dragging brake can pull to one side. But you specifically mention the steering not self-centering, and that's a caster issue.

Good luck,
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PostPost by: Mick6186 » Tue Feb 12, 2019 7:55 am

I assume you have checked that the trunnion are lubricated and rotate freely,
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PostPost by: JonB » Tue Feb 12, 2019 11:18 am

69S4 wrote:Any plans on how you’re going to go about the adjustable wishbones project Jon? I’ve got a set I want to do the same with but I’m holding back on picking up the hacksaw until I’ve got a better idea about the process.


Yes. I will follow miked's technique:

lotus-suspension-f42/frame-adjuster-t30315.html

I already have the turnbuckles and a spare set of arms. The main issue seems to be the threads locking up when welding the turnbuckle ends into the tube. And machining them to fit the tube if you have no lathe (like me). So I propose to machine them with a pillar drill and file (will be very rough) and use three puddle welds per end (i do not know what those threaded sleeves on the turnbuckle are called). Then try to turn the "buckle" to free up the threads. If that works I will let it cool down then weld around the joins bit by bit, allowing the assembly to cool between successive welds. Also, clamp it in a vice so as to provide an additional heat sink.


Regarding castor changes and shimming round the ball joint: I do agree with Esprit2's comments which is why I have not done mine yet. I meant to add to my list above that you should renew all the suspension bushes before attempting this as it may improve matters. Anything you can do to remove unknown factors. But even if you do end up shimming the top joints, the bushes have some give in them so trunnion stress will not be as bad as it appears, IMHO.

Having said that, I have done my bushes and it has not improved straight line stability - and the old bushes were demonstrably bad.
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PostPost by: vincereynard » Tue Feb 12, 2019 11:38 am

Expensive option could be to replace the dreaded trunnion with a ball joint kit as supplied by Triumph specialists.

Then you could shim without a problem. The shims are available from the same source.

Naturally there's not much point in doing all the tracking without having all the other bits OK and the car loaded as it will be used.
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PostPost by: 69S4 » Tue Feb 12, 2019 1:22 pm

JonB wrote:
69S4 wrote:Any plans on how you’re going to go about the adjustable wishbones project Jon? I’ve got a set I want to do the same with but I’m holding back on picking up the hacksaw until I’ve got a better idea about the process.


Yes. I will follow miked's technique:

lotus-suspension-f42/frame-adjuster-t30315.html

I already have the turnbuckles and a spare set of arms. The main issue seems to be the threads locking up when welding the turnbuckle ends into the tube. And machining them to fit the tube if you have no lathe (like me). So I propose to machine them with a pillar drill and file (will be very rough) and use three puddle welds per end (i do not know what those threaded sleeves on the turnbuckle are called). Then try to turn the "buckle" to free up the threads. If that works I will let it cool down then weld around the joins bit by bit, allowing the assembly to cool between successive welds. Also, clamp it in a vice so as to provide an additional heat sink.




I didn't realise you could buy the complete turnbuckle assembly on eBay. That simplifies matters. Like you I don't have a lathe (and don't know anyone who has) so machining the collars is going to present a challenge. Welding is within my skill set and I've done plenty of stuff where a screw has to subsequently rotate within a welded nut - a flywheel puller for one of my motorcycles most recently - and not had an issue with the screw binding. Is there something unusual about this setup that would cause it to bind?

I've tended to shy away from mission critical (i.e. structural) welding though and this one rings all the warning bells. The thought of it coming apart on the road ... There must be some local qualified welders. I'll have to have a look.
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PostPost by: vincereynard » Tue Feb 12, 2019 1:37 pm

69S4 wrote: There must be some local qualified welders. I'll have to have a look.


My engineering chap is in Chesham! Not that far from Thame.
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PostPost by: JonB » Tue Feb 12, 2019 1:39 pm

Apart from the "mission critical" nature of this modification, there is also the question of turnbuckle quality. "Is it suitable for this application?" is the question that is nagging me. The eBay listing does say it can be used like this but with little specification detail of the parts, there's not much to go on.
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PostPost by: miked » Tue Feb 12, 2019 2:28 pm

Jon,
I never had a problem with the welding locking up threads on the turnbuckle. I have done it on at least 6 sets. As regards suitability that is for each individual. My simple thinking was the amount of cross section of metal on the turnbuckle is greater than the very thin A frame tube, i believe. I will work it out when i get back in the garage to measure. You will be quite amazed how thin the wall thickness is. Also some people have blasted the living daylights out of rusty A frames making the wall thickness less. I have scrapped quite a few found like this. Orange peel with corrosion.
The proper mechanical engineers should know more about this but isn't the turnbuckle in compression or tension depending what the car is doing on the road. So, based upon csa, must have more strength than the tube.
Unless somebody (MOTwilly) jacks right in the middle, might cause damage. Saying that you would not do that without these fitted. How many of us have straighten bent A frames. The beauty of the long recessed collars is that they add strength with the weld if turned closely. Or even if brazed. :D
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PostPost by: 69S4 » Tue Feb 12, 2019 2:55 pm

vincereynard wrote:
69S4 wrote: There must be some local qualified welders. I'll have to have a look.


My engineering chap is in Chesham! Not that far from Thame.


Indeed. Who do you use? A recommendation, like a picture, is worth a thousand adverts.
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