Lotus Elan

Autobushes

PostPost by: davidj » Thu Jun 06, 2019 7:50 pm

Good evening,

I am in the process to fitting Autobush poly bushes, starting at the front suspension. The bushes push into the wishbones (spider) ok but the top hat section does not pop out fully out of the eye. The pictures explain it better. On the side I pressed the bush in, it is flush with the edge of the boss. On the side it pops out from it is not.

Is this a concern, or am I worrying about nothing? ( I have not even got to the rear suspension yet which appears to cause most problems from reading posts over the years.)

Thanks in advance for any comments. .


img_20190606_201904.jpg and
pressed out side

img_20190606_20185.jpg and
pressed in side




David
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PostPost by: miked » Fri Jun 07, 2019 6:12 am

David,
It needs to pop out the same as the other side. The bushes are designed and made to fit Lotus bones. You may well find that Spyder bones are not dimensionally accurate. Longer bush tubes which are forgiving with rubber bushes. Even the paint within the tube and on the edges will influence the final fit of the poly bushes.
I suggest you get back in hot water and pop back out. Then find the measurements of original Lotus bones and compare. I had this problem with Spyder bones and had to have the internal bore reamed by 20 thou or so. Yes, that made them extrude and wider than the crush tube. Also had to file the width of the tube to get to Lotus width. If you do not the crush tube will not sit slightly proud and the bush side will bind on the side washers.
If you loook back in my very old posts there is "war and peace" about front and back.
When peolpe make these bushes themselves on the lathe they go to great lengths to ensure the crush tube sits proud by the correct amount. When building up you need to work on bone pairs nipped up to ensure they move correctly. Correct lubrication.
Also final build check with no shocker to ensure free movement of the assembly.
Checking spacing at top ball joint and trunnion. The washers can mess this up. I am shimmed up on my top ball joint (sounds painful) to give perfect squareness of the bushes and there side washers.
Cheers Mike
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PostPost by: davidj » Fri Jun 07, 2019 8:21 am

Thanks for such a such a comprehensive reply! Do you think they are worth the effort? I am fitting them as I got a set when I brought the car. However, not only were the old bushes a pain the remove, but the new ones may not fit with the spyder wishbones!

Also I am not convinced about their operation. The old ones flex the rubber; these move on the tubes, making the chassis/washers a bearing surface!

Frustrated autobush fitter!
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PostPost by: miked » Fri Jun 07, 2019 9:19 am

I think they are worth the effort, as you say, they become bearings rather than flexing bushes which tend to degrade and rip and also require that setting up procedure to ensure you get as neutral as possible at ride height allowing flex in droop and bump.
You've got to ask yourself the question about having the patience to fiddle and fettle. I think you get better suspension geometry since they are held somewhat captive between the washers. Where as if you look at rubber bushes they migrate one way or the other. An advantage on badley fitting or bent A frames when working at the rear.
I will probably get stoned by the purists. :D One thing that gets said is that they are more harsh. That depends upon the material and i know the blue stuff that Autobush use is not hard. I have fitted them about 4 times.
The worst are the mods to the outside A frame ones. Requires some work on the strut alloy. Again a lot of measuring and fettling to get stainless washers in and correct tension. Worst part of the car imo are those little bushes. Flexing to and fro under acceleration and braking.
These outside poly bushes are easy to chew up on the top hat section if they move about. Plus 2 with more weight gives them a harder time.
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PostPost by: davidj » Fri Jun 07, 2019 1:16 pm

Thanks again. I will persist for a bit longer as I have the bushes. However, you mention stainless washers? No mention on the Autobush site. I guess you need them between the bush and the alloy rear strut face? Where else? I would not expect there is space to sandwich between the bush and the chassis?

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PostPost by: miked » Fri Jun 07, 2019 1:39 pm

David,
Washers go either side of each of the bobbins on the front bones for them to bear on. Some just do the outside of both bones but I do inside. Hence comment about shims on top ball joint.
Nothing in the rear inboard A frames. They work against the chassis bracket mountings.
The late Mick Miller came up with the design and then they were copied by others. Sue and Mick gave a dimension to trim back the strut alloy on the rear outboard bushes.
They recommended a stainless washer to sit between the top hat bush and the strut hole alloy. I have made these from plate in the past as the front one needs the edge trimming because of the Strut casting. I used their measurement to give a guide and trimmed the alloy to give a nip on the two washers and top hats. I made it tight enough that I need to bar the A frame with a protective cloth to slip the last washer in. I drew it first with the intended sandwich of parts.
If you look Ceejay is the expert as I recall. He has all the info about making them on his site. The important of the crush tubes and lubrication etc.
Cheers Mike
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PostPost by: davidj » Fri Jun 07, 2019 2:49 pm

Thanks again Mike. I came to a similar conclusion, as the boss on the chassis is only (approx) 0.75" and for the design to work a large mating face is required. As you said, this will require shimming the top ball joint. Trimming back the struts will also be required at the rear, unless you wish the bushes to run on the alloy casting. This would worry me more, as the struts are very expensive, a pain to fit and once the material has been removed, the original bushes will no longer fit. Plus how do you accurately remove a few mm from the strut without access to a milling machine? A hand held file would not be very accurate.

All in all, it is not quite as simple as it would first appear!

For future reference, a managed to get the bush to fit correctly by warming it first.

David.
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PostPost by: miked » Fri Jun 07, 2019 4:25 pm

I know where you are coming from David. I have painstakingly sat with a file, engineers blue and a collar on a close fitting rod to shave some off. Hard work. I suppose the gaps can be made uo with spacer washers if reverting back. Most of these struts have crush tube damage from having no washer against to protect.
Cheers Mike
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PostPost by: RichardHawkins » Fri Jun 07, 2019 5:57 pm

David,

I certainly would not call myself a purist, however, I was pusuaded by the argument that vehicle manufacturers don't use polyurethane. On the other hand repro rubber, such as engine mounts is awful. In the end we all have to make our own decision.

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