Lotus Elan

Modifying Engine Mounts

PostPost by: pharriso » Mon Oct 03, 2016 11:01 am

My Carb side engine mount failed with less than 2000 miles in service, leaving the airbox bouncing against the passenger side footwell. The rubber/metal bond seem OK but the mount is permanently sagging.

Here's a picture of the failed mount against a new one:

img_5409.jpg and

img_5392.jpg and
yes I do know the mounts are upside down in this picture!


I modified the new engine mounts by filing all voids with Dow U-428 Urethane Glass adhesive. Sticks like S*** to a blanket & is quite stiff:

img_5310.jpg and

img_5308.jpg and


After replacing the engine mount I now have about 3/8" (10mm) between the airbox & footwell:
img_5393.jpg and


Let's see if this engine mount lasts any longer than the last :roll:
Phil Harrison
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PostPost by: Certified Lotus » Mon Oct 03, 2016 12:11 pm

Phil, I keep hearing the "new" engine mounts have a higher failure rate then the old ones. Your latest experience is confirming that. Where did you get the past versions and the new ones?
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PostPost by: pharriso » Mon Oct 03, 2016 12:54 pm

Old ones were fitted by Randal Fehr in Seattle so I suspect Dave Bean, new ones are from Paul Matty.
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PostPost by: david.g.chapman » Mon Oct 03, 2016 6:16 pm

I have wondered if a nut/bolt combination could be fitted to these mounts. Drill a 15mm hole though the entire mount (side to side), then fit a rubber bush to the hole (15mm OD, 5mm ID). The finish off with a 5mm x 40mm bolt, say

Lets see the mount sag after that mod!

The tricky bit of course, is to get the right degree of compliance in the mount. Too little and there will be too much vibration, and stress on the chassis mounts, too much and the clutch might judder/excessive engine movement.

The torque on the nut/bolt combination might give a little compliance adjustment.

The trouble is, I can't pluck up enough courage to try it on my only two engine mounts!

Has anyone else tried something like this?

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PostPost by: 1owner69Elan » Mon Oct 03, 2016 7:02 pm

If you look at the Tony Thompson "uprated" standard mounts, of which I have but not yet fitted, the weak gap has been completely filled, similar to the modification that was made above to the new Matty versions. The material is a very hard rubber that appears similar to the existing material.

The other alternative is racing type mounts, are mostly metal but that can include a bushing. But, I suspect those mounts might transmit more NVH. Acceptable for racing, but not as good for the street.
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PostPost by: pereirac » Mon Oct 03, 2016 8:51 pm

Kelvedon Motors do an interesting (is expensive) alternative mount with a single 'suspension style' bush.

http://www.kelsport.net/parts/product_details.asp?PartID=2686&categoryID=47&PartsectionID=66

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PostPost by: Certified Lotus » Tue Oct 04, 2016 12:11 am

I have TTR motor mounts in my 150HP Elan S1 and have had no problems in the past year of driving.
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PostPost by: RichC » Tue Oct 04, 2016 7:12 am

what's your view of the difference in vibration level between TTR mounts and standard pls?
I'm seriously thinking of changing as my standard ones are failing after just a few years
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PostPost by: rgh0 » Tue Oct 04, 2016 9:46 am

At idle I get significantly more vibration using the TTR racing mounts compared to standard mounts in my Elan. Above idle once moving the difference is not really noticeable. My race engine has a relatively short duration high lift race cam and also a lightweight flywheel and it idles well but certainly a bit rougher than a road car, so the TTR mounts would be better with a road tune I think.

The TTR mounts and Kelvedon racing mounts are similar in concept if different in execution details.

I have a friend who races a twin Cam Europa that uses the same mounts as an Elan The engine forms part of the Europa rear suspension location so you cant have it moving around to much. He drilled a clearance hole through the standard mount and put a bolt though the inner and outer sections so that with small deflections the engine can move on the rubber mount to absorb vibration but under high load such as during acceleration ( or cornering in a Europa) the bolt carries the load and prevents excessive movement. This seemed to work well for him

cheers
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PostPost by: Certified Lotus » Tue Oct 04, 2016 10:46 am

RichC wrote:what's your view of the difference in vibration level between TTR mounts and standard pls?
I'm seriously thinking of changing as my standard ones are failing after just a few years


To be clear, I do not have the race mounts. Just the normal engine mounts, but they seem to be better made than the original set that was on the car.

Tough to give a comparison. When I bought my S1 the motor mounts where on backwards (reversed). I replaced them right away with TTR as I didn't trust the original mounts that came with the car due to the way they were installed. Never the less, I don't have an excessive amount of vibration. (Truth be known, I was coming from a track Exige S where everything vibrated until I was at speed, so the S1 was smooth as silk from my point of view).
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PostPost by: CBUEB1771 » Tue Oct 04, 2016 2:16 pm

Kelvedon recently added a second version of their competition engine mounts. The new version uses a larger diameter Metalastic type of bushing, essentially the same as used on the inboard end of the rear control arms on the Elan and +2. This provides a bit more compliance than the original version which uses a bushing with smaller outer diameter.
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PostPost by: redcarandco » Tue Oct 04, 2016 2:47 pm

If it can help and gives some ideas this is what I use on a racing elan for more than 20 years without any trouble and has never been changed....... Photos are of the ""prototype "" we made in period...In fact a not at all scientific melt of original and slightely modified former TTR race ones...and can tell it does not generates any good or bad vibrations at all........
Attachments
001.jpg and
005.jpg and
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PostPost by: Quart Meg Miles » Tue Oct 04, 2016 10:05 pm

One time I had an engine mount break I temporarily jammed a piece of rubber, possibly cut from a previously failed mount, between the two bits of touching metal (after jacking the engine back up to proper height). I don't recall any undue vibration and this could be a reinforcing method for modern mounts.
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PostPost by: billwill » Wed Oct 05, 2016 1:36 pm

I was in Brent Cross shopping centre yesterday and Tesla have a showroom there.

There were two electric cars and a rolling chassis. The rolling chassis was huge; I reckon at least as big as my Renault Grand Espace 7-seater, but what was relevant to this topic was that the motor mounts at the front were rod and bush systems similar in essence to those shown above.

I was surprised to see a large double-size motor at the back (at least 10-12" dia and about 2 foot long and a single size such motor at the front. There were differentials at both back and front.

Somehow I had got it in my head that electric cars used one motor per wheel and therefore did not need diffs; clearly wrong of me.

Sorry I didn't think of taking any photos. :( But here is one from the Internet
Image

and more here:
https://www.google.co.uk/search?q=tesla ... 7gstYzM%3A
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PostPost by: john.p.clegg » Wed Oct 05, 2016 1:56 pm

Is that the one that had the top sliced off while going under a flat back trailor?

https://www.theguardian.com/technology/ ... rry-potter

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