Lotus Elan

Hopping Rear

PostPost by: smo17003 » Wed Jul 20, 2022 8:00 am

Not relevant to the body movement but I would also take a look at your caliper mounting bolts. Service and parts manuals have no mention of washers under the bolt heads but the service manual does say to lockwire the bolts after torquing up. If they're the correct bolts they should be drilled through the heads for that purpose.
Unless of course you have used a thread lock like Loctite?
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PostPost by: Elanman99 » Wed Jul 20, 2022 8:22 am

As per the last reply (mike), some of the things visible in your pictures raise alarm bells.

Its worrying to see bodges on the caliper and rotoflex bolts. They certainly would not have been assembled like that by anyone familiar with Elans.

What is the car history?

If you give your (rough) location it may be someone near you will be able to assist.

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PostPost by: alanr » Wed Jul 20, 2022 8:35 am

As others have said you have some really serious bodges going on to that inner doughnut which obviously needing sorting before you attempt drive the car again!
The way the caliper bolts have washers that shouldn't be there is also of concern however I think it would be very interesting to see some photos of the outer doughnut and its bolt fixings?

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PostPost by: smo17003 » Wed Jul 20, 2022 9:37 am

Regarding the caliper bolt lockwire I found this method on a YouTube video to be really helpful when I did mine. If it's good enough to stop a light aircraft's wheels falling off it's probably got to be OK for my Elan :D

https://youtu.be/96EM1JvvZ8s
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PostPost by: SENC » Wed Jul 20, 2022 12:41 pm

For videos, easiest to upload to YouTube then link here.

The blue nut and washer are definitely a concern, and I can't tell what is going on with the red one - is the head broken off, or? Definitely need to remove the entire donut and shaft assembly for complete inspection. This makes me wonder if the arms on the shaft are bent/out of alignment, and these unexpected mountings there just to make it fit?

IMG_20220720_083639.jpg
IMG_20220720_083639.jpg (104.39 KiB) Viewed 274 times
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PostPost by: Andy8421 » Wed Jul 20, 2022 12:49 pm

smo17003 wrote:Not relevant to the body movement but I would also take a look at your caliper mounting bolts. Service and parts manuals have no mention of washers under the bolt heads but the service manual does say to lockwire the bolts after torquing up. If they're the correct bolts they should be drilled through the heads for that purpose.
Unless of course you have used a thread lock like Loctite?

With apologies to the OP for the slight thread drift, and agreeing that the parts manual does not show washers, I thought you always put a steel washer against a soft material to avoid a bolt head galling and 'digging in' as it was tightened. The manual shows every nut and bolt on the engine with a washer where it is up against aluminium.

Is it possible that the parts diagram is in error?
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PostPost by: smo17003 » Wed Jul 20, 2022 1:29 pm

Andy8421 wrote:
smo17003 wrote:Not relevant to the body movement but I would also take a look at your caliper mounting bolts. Service and parts manuals have no mention of washers under the bolt heads but the service manual does say to lockwire the bolts after torquing up. If they're the correct bolts they should be drilled through the heads for that purpose.
Unless of course you have used a thread lock like Loctite?

With apologies to the OP for the slight thread drift, and agreeing that the parts manual does not show washers, I thought you always put a steel washer against a soft material to avoid a bolt head galling and 'digging in' as it was tightened. The manual shows every nut and bolt on the engine with a washer where it is up against aluminium.

Is it possible that the parts diagram is in error?


I must admit that I did wonder that myself. Definitely no mention of washers in the re-assembly instructions in the manual though. However, the drawing for the front calipers in the service manual does show (spring) washers and yet once again no mention of the washers in the re-assembly instructions. I believe there's already threads on here discussing the merits of washers under the caliper bolts. Always more questions than answers with Lotus.
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PostPost by: SENC » Wed Jul 20, 2022 1:34 pm

The metal inserts (and interleaves) in the rotoflex are steel, not aluminum, I thought/assumed (incorrectly?).

The metalastic literature on the rotoflex doesn't seem to show any washers, either, for what that is worth.

Rotoflex-.pdf
(1.09 MiB) Downloaded 13 times


EDIT - sorry, I see you were referring to calipers, not rotoflex
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PostPost by: smo17003 » Wed Jul 20, 2022 1:50 pm

OP is the body lift on the same side that you had a problem with the strut earlier this year? You mentioned a loose inner bearing circlip. Perhaps this is an indication of a problem with the bearing or bearing housing.

viewtopic.php?f=19&t=51004&p=370991#p370991
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PostPost by: 2tmike » Wed Jul 20, 2022 3:25 pm

From where you have the car supported, for wheel rotation to lift the body my guess would be bent driveshafts/spiders perhaps evidenced by that bolt that hardly protrudes through enough to get the nut fully on. Maybe result of a previous rotoflex failure and a bodged repair ?
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PostPost by: Temmck » Wed Jul 20, 2022 8:08 pm

...And the donuts used on this side don't match the ones on the other side. The passenger (right) side appear to be original (round tube for the bolts) where this side appears to have been changed at some point and uses the newer two-piece bushing.
I will be changing the donuts next weekend (no driving in between) and will report out any differences.
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PostPost by: UAB807F » Thu Jul 21, 2022 5:33 am

Hi there,

Congratulations and well done, you've found a real puzzle there !

One thing that gets me is that if you're supporting the weight of the car on that wooden block underneath the A frame then I'm struggling to see how rotating the hub by hand causes the body to move. I certainly couldn't rotate the hub by hand and lift the body !

At first I thought a bent driveshaft or the spiders that locate the rotoflex but against that those rotoflex look in reasonable condition so I'd have thought they'd take up the movement given they're set at ride height and normally go from full bounce to droop.

Looking at the measurements it did make me wonder if the hub wasn't central because you're measuring hub->body and not body->ground. It'd be interesting to know if the same movement is seen measuring from body->wooden support ?

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PostPost by: Elanman99 » Thu Jul 21, 2022 8:34 am

Temmck

I dont think any Rotoflex couplings had 'round tube' moulded-in inserts. Early Rotoflex had inserts that were a solid steel part basically tubular but with two integral 'wings', I suppose at a casual glance they might appear to tubular just where they sit on the spider.

As the last reply stated it is difficult to see how you could generate enough force by hand rotating the hub to actually make the body lift. For bent shafts or distorted spiders would create eccentric forces but surely the diff would (try to) move on its flexible mountings long before the wheel suspension did.

As regards fitting new Rotoflex couplings, think by the time you have stripped down the rear suspension the cause of the problem will be apparent, whatever it is must be revealed by careful inspection of the components. Personally I dont see how it can just be the couplings themselves.

It is vitally important that the Rotoflex bolts and nuts are the correct items and if the ones visible in your pictures are anything to go by I suggest that you reassemble with a completely new full set. (Check the manual to make sure you orientate the high and low bosses correctly.)

Lastly, washers are not used on the caliper bolts. Its a horrible thought, but I wonder if someone put them on to disguise a damaged lug.

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PostPost by: rgh0 » Thu Jul 21, 2022 10:14 am

The donut has a significant spring rate effect as it is deflected from straight and undistorted. The suspension setup has the drive shaft sloping down to the outside at normal ride with just 1 up. With broken bolts or loose bolts the deflection of the actual donut will change as it is rotated leading to the the change in right height as the donuts contributes more and less to the overall spring rate as it rotates. The two wrong bolts in the photos will probably mean the donut is not properly and rigidly fixed to the spider arm of the drive shaft leading to the observed outcome.

This is what I observed many years ago when I had a donut bolt fail.
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PostPost by: Andy8421 » Thu Jul 21, 2022 11:55 am

Elanman99 wrote:
Lastly, washers are not used on the caliper bolts. Its a horrible thought, but I wonder if someone put them on to disguise a damaged lug.

Ian

Ian,

I would like to understand more about this. The rear caliper bolts pass through the aluminium lug at the bottom of the strut, and screw into a thread tapped into the cast caliper body. As I mentioned above, I believe it is usual practice to place a washer under a bolt head when a soft material is being clamped to avoid the bolt digging in to the soft material. The engine (for example) has a washer under every nut or bolt where it is up against an aluminium casting.

Do you have technical knowledge in this field, or are you basing your comments on the parts list diagram?

Thanks,

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