Lotus Elan

Shock roll bar bolt angle for Elan ( and Plus 2)

PostPost by: rgh0 » Mon Sep 27, 2021 1:27 am

Put my Elan on the hoist for a check over prior to my next race meeting in November (hopefully :D ).

I discovered that the 3/8 unf threaded section of one of the shock lower bolts that secure the roll bar has broken off.

It appears easy enough to machine up and weld on a new bolt but I need to know the "correct" angle versus the shock axis. I cant find any references to this angle anywhere

I measured 15 degrees for the TTR shocks on my Elan. From the front suspension drawing in the workshop manual, I calculated 14.8 degrees with the lower wishbones horizontal. If anyone has ever seen any more "official" number for this angle it would be good to know. The Plus 2 has a larger angle and I would be interested in knowing this also if anyone has it.

The "bolt" welded onto to the bottom eye of the shock appears to be a 7/16 inch bolt with its end machined down with a 3/8 unf thread. It appears to be identical to the "bolt" welded on the top of the shock strut that mounts in the chassis. At this point I see no reason why the lower 'bolt" could not remain the full 7/16 unf diameter and not be machined down as this would reduce the risk of failure that I experienced when using larger roll bars like I do at 22mm diameter

cheers
Rohan
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PostPost by: mbell » Mon Sep 27, 2021 2:15 am

Don't have a protractor but this is a picture of the ttr +2 front shocks. Adding a few lines to it should allow you to get the angle.
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IMG_20210926_210927_compress44.jpg and
Ttr +2 front shocker
'73 +2 130/5 RHD, now on the road and very slowly rolling though a "restoration"
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PostPost by: rgh0 » Wed Sep 29, 2021 11:54 am

Thanks for the plus 2 shock photo. it saves me pulling one of my plus 2.

I have measured everything up and there appears no barrier to using a full 7/16 in bolt for the roll bar connection rather than the reduced 3/8 cut thread end on a plain 7/16 shaft . I have cut off the failed "bolt" and pressed out the bushing and will prepare the surface for the new bolt with rolled threads to be welded on at the 14.8 / 15.0 degree angle and then get one of the expert welders in the maintenance department in the plant where I work to complete the weld which will only take about 1 minute .... as my welding is crap :roll: .

The thread on the bolts is subject to oscillating rocking loads with each suspension movement hence the fatigue failure of the reduced diameter cut threaded connection under racing loads with a stiffer 22 mm roll bar

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Rohan
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