Lotus Elan

Broken rear shock mount

PostPost by: seniorchristo » Wed Aug 28, 2019 3:50 pm

Driving to LOG 39 I broke the right rear shock mount. My guess is the D shaped hole in upper spring pan enlarged allowing shaft to push through. Shouldn't there be a washer beneath or something to prevent this? The shocks are Spax 9010 from Dave Bean. Is this a common occurrence? Thanks
Chris
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PostPost by: MarkDa » Wed Aug 28, 2019 8:44 pm

The short answer is no - there is no washer.
The spring seat hole is supposed to a close enough fit and thick enough to do the job.
I don't know if it's a common failure.
It is possible that your damper rod was on the small size and the hole already slightly worn.
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PostPost by: seniorchristo » Wed Aug 28, 2019 10:36 pm

MarkDa
Yeah, I guess that's a possibility. I'm going to take apart in the next few days to find out :)
Chris
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PostPost by: snowyelan » Wed Aug 28, 2019 11:04 pm

Hi
If you're using a setup with smaller coils and adjustable shocks then there should be a washer in there somewhere. I can't recall the exact stackup but I think it was washer (not D shaped) on the shock shoulder, spring perch, lotocone, stepped nut.

Sorry just looked at your pic again. I see an adjustment nut but not a stepped nut so I assume standard springs with adjustable dampers. Best guess is you've sheared the d bit out of the hole in the perch.
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PostPost by: seniorchristo » Thu Aug 29, 2019 12:09 am

snowyelan
I have the narrow 2 1/4" springs so maybe there was supposed to be a washer of which you speak.
Chris Herr :)
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PostPost by: snowyelan » Thu Aug 29, 2019 12:26 am

I bought the dampers and perches from DB. Too long ago to find the receipt but I still have the low lockouts supplied with the dampers in a bin somewhere. They were definitely replaced with stepped nuts supplied from DB in their adjustable perch kit. Just put it all back together a month ago. I'll see if I can snap a pic or 2 for you. Stay tuned.
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PostPost by: snowyelan » Thu Aug 29, 2019 12:41 am

Pics I think?
20190828_203805.jpg and
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PostPost by: snowyelan » Thu Aug 29, 2019 12:47 am

20190828_203835.jpg and
Oops. Looks like the blurry washer pic only came thru. Nut pic above I hope. Its hard anodized aluminium. About an inch long with 2/3 turned off the OD to suit the lotocone ID.
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PostPost by: RichardHawkins » Thu Aug 29, 2019 8:04 pm

The top spring mounting disc with the D shaped hole sits immediately beneath the Lotacone. On my car (1968 S4 Elan FHC with standard springs) the hole was beaten out of shape by the damper rod on both sides of the car. I collected several of these top spring mounting discs, until I found two that were not damaged. I concluded that damage was common.

After further inspection with new dampers and new Lotacones I noticed that there is a void between the top of the mounting disc and the bottom of the Lotacone. The damper shaft has a slightly smaller diameter (3/4" where it passes through the D shaped hole) than the rest of the damper shaft (7/8") diameter. My opinion is that the damper forces, over time, are sufficient to force the 7/8" shaft through the 3/4" D shaped hole. This is made more easy by the void between disc and Lotacone and also how difficult it is to tighten the top nut securely.

My solution is a spacer that fills the void between top mounting disc and the Lotacone. Unfortunately I will never put enough miles on the car to find out if I am correct.

Hope this helps,

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PostPost by: seniorchristo » Thu Aug 29, 2019 11:48 pm

Hi Richard
Upon close inspection I see what you mean. The upper spring pan (mounting disc ?) is also a fairly thin gauge metal and I can see it wallowing out if not clamped tightly. What did you use for a spacer?
Thanks
Chris :)
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PostPost by: rgh0 » Fri Aug 30, 2019 10:05 am

The original Lotocones had a full support for the spring support cap so the rod would not push through. Current Lotocones have the larger diameter opening that does not support fully the inner edge of the D shape cut out hence the tendency for the rod to push through over time.

it is thus wise to look at how to better support the cap. I use a thicker material than originally used in the small diameter spring caps i use.

cheers
Rohan
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PostPost by: MarkDa » Fri Aug 30, 2019 10:58 am

Similar discussion 10 years ago with pictures and solutions.

viewtopic.php?f=42&t=18744&start=

It does seem strange that the design has changed - I'd assumed that nowadays must be bespoke rather than from another car.
In which case they ought to be right.

A good plug for Susan Miller - I hope she's still sticking to her guns.

I will admit to replacing the half height head set screws many years ago - I didn't realise the significance but haven't been aware of harshness - another job for the winter!
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PostPost by: Certified Lotus » Fri Aug 30, 2019 6:07 pm

Picture to tell the story
7dbf67bc-6f4b-49c0-ba31-15bb6c1d322b.jpeg and
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PostPost by: RichardHawkins » Fri Aug 30, 2019 7:17 pm

Chris,

I made my spacers from brass to fit the shape between the upper Spring mount disc and the Lotacone.

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PostPost by: seniorchristo » Sat Aug 31, 2019 6:07 pm

The old spring pan was indeed "wallowed " out. The new spring pan (pictured) and my locatone have different conical shapes and there is a substantial gap where the D shaped hole matches up. Not being able to machine spacers of the correct shape I am going to use some softer aluminum washers to help maintain the D shape when tightened.
Chris :)
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