S1/S2 - My idea for improving the motor mounts

[Tony K]

S1/S2 owners:  I recognize that a quality upgrade to Turbo Esprit motor mounts is the best solution, but I've had an idea in my head for a while to improve the durability of the stock motor mounts that I haven't had the opportunity to implement, so I wanted to share it.  Regardless of what anyone thinks, I'm going to try it eventually . . . but maybe someone wants to try it sooner.

As most people know, the stock motor mounts don't last long, especially when the car frequently experiences hard acceleration.  The rubber gets cooked to a crisp by the exhaust manifold -- and that can be mitigated to an extent with heat shielding -- but after a while the bond between the rubber puck and metal disc still gives.  This is in part due to the fact that every time you accelerate, that engine is pulling upward on the motor mounts (drive with the engine cover off, and it can be shocking how much the engine lifts under acceleration).  

So my idea is, simply, to screw the metal plates to the rubber.  To give it something more than just whatever bond or adhesive is holding the metal to the rubber.

Tap several holes -- I'm thinking between 4 and 6 -- into each side of the motor mount, bevel the edges, and insert a screw.  Too few screws and it won't do much;  too many and you're eating away at too much rubber.  Do not run the screws all the way through;  that's effectively creating a solid mount and negating what little NVH reduction the rubber offers.  I'm thinking using screws that go about two thirds (2/3) the depth of the rubber, so there is some overlap to help prevent the shearing and "smearing" of the rubber itself, but not so much that the mount just becomes a stand of screws.

What kind of screws to use?   I'm thinking drywall screws or wood deck screws (not sure what they are called in the UK);  they sit flush and have wide threads that give good bite into softer substances.  

When I eventually get around to it, that's what I have in mind.  If this has already been done, I apologize, as I've been away for a while.  Open to your suggestions on how to improve it, or your thoughts on why it will or won't work.  If somebody tries it before I do, please share your experience here!   

 

[drdoom]

Hi Tony,

You make a valid case for concerns with the mounts, and the added screws may afford some improvement so worth a try I suppose. In sufficient numbers they may prolong life of the mounts and likely add some restraint to the excess movement seen in the originals. Interesting and with a simplicity that ACBC might have approved of.

[frb]

Hello Tony (and Steve).

 

Tony, the very modification you suggest has been done before by someone with a S2 or S2.2 on this forum (sadly, I don´t remember who it was). Inspired by that owner I tried this solution as well after I had terminal failure of both mounts simultaneously on my S2 . Two years after fitting the modified engine mounts function as they should, hold up well and have not caused any problems.

For EACH mount I used 6 countersunk screws ( i.e. 3 on the upside, 3 on the downside arranged in a regular 60 degree pattern ) and also added an industrial quality adhesive sealant (Innotec Adheseal) into the drilling holes before screwing the screws in. The engine mounts available today seem to be a little bit higher than the original mounts as specified by Lotus and also often lack a little "locating tab" to prevent the mounts from twisting. As a solution against twisting I added an additional little screw (NOT countersunk !) where the locating tabs should be.

Renn Ortenburger described a similar modification on his blog, which could be found here:

http://www.lotusespritrestoration.com/2010/05/preparing-lotus-esprit-s1-engine-mounts.html

 

I´d love to post some pictures but they sadly seem to have been lost during a computer crash .

Hope these experiences are at least of some help to you.

Greetings from Austria,

Georg

 

UPDATE: Found the post:

 

Edited November 14, 2023 by frb
Link added

[drdoom]

I concur with Georg on the use of adhesive, thinking the screws might otherwise be inclined to work themselves back out over time.

[LOTUSMAN33]

Adding the engine snubber helps prolong mount life holding the engine during hard acceleration.

I’ve used similar on classic minis for years to hold the engine firm.

Dave 🙂

[drdoom]

Dave, have you a way by which to have these made in numbers? I'd certainly be interested if fairly priced. As I enjoy hard driving in my toy there are 2 additional aspects which concern me: an alternative arrangement of ancillaries in order to accommodate a dry sump system, and minimising derangement of the rear suspension under cornering loads.

Cheers

[LOTUSMAN33]

I’ll ask the question Steve 👍🏻

[GavinT]

I’m in on the engine snubber / stabilizer 

[rgh0]

I used a commonly available industrial machinery mount to replace the orginal mounts. Did it around 35 years ago and no problems since. You can see a small cutout was required in the engine support arms to clear the way for the top bolt insertion. Metal plates and washers were added to support the alloy lower mount bolt ears that were slotted slightly and bolted to the orginal lower chassis bolt holes used for the bracket the orginal mount was bolted to.  The mounts came in two stiffnesses, I tried both and used the softer one.  The harder one transmitted to much engine vibration to the chassis.  These hold the engine much more stable and no need for an add on stabiliser bar. 

 

[pmth95]

@rgh0 would you happen to have the part number for those?

[rgh0]

This is the catalogue page for the mounts from Mackay Rubber which is an Australian company.  There will be something very similar made by European or US companies. I ended up using the softer of the 2 mounts

 

https://www.mackayrubber.com.au/_files/ugd/17eaaa_76b4be1c2af249399d39aebe08ec33a3.pdf

 

cheers

Rohan

[drdoom]

Something along these lines?

https://www.novibes.com/Products/Stable_Flex_Mounts

 

[CarBuff]

1 hour ago, drdoom said:

Something along these lines?

https://www.novibes.com/Products/Stable_Flex_Mounts

 

Is the Lotus engine/transmission assembly considered to be "lightweight"?

And who are you calling low speed??? 😄

 

 

You know what happens when we ASS-UME. 😮

 

Quote

Stable Flex Mounts have been specifically engineered to isolate light weight, low speed equipment.

 

[rgh0]

6 hours ago, drdoom said:

Something along these lines?

https://www.novibes.com/Products/Stable_Flex_Mounts

 

The -10 version has the same load rating as the one I used and dimensionally would fit. It is slightly shorter so would need a thicker spacer under it. Worth a try.

 

cheers

Rohan

[Finlandese]

On 27/11/2023 at 02:05, rgh0 said:

.... the alloy lower mount bolt ears that were slotted slightly...

 

 

 

 

Very interesting. Did slot the holes inward or outwards?

[rgh0]

The holes were slotted a few millimetres outwards to align with the existing chassis bolt holes

[Finlandese]

6 hours ago, rgh0 said:

The holes were slotted a few millimetres outwards to align with the existing chassis bolt holes

Thank you for your reply. I am very tempted to try your solution. 35 years with no issues is a pretty solid proof of success.

[Finlandese]

On 10/01/2024 at 06:29, rgh0 said:

The holes were slotted a few millimetres outwards to align with the existing chassis bolt holes

I guess I will start slotting them now, as I just got a delivery from AIMS for two mounts.. 🙂

Does anyone happen to have the exact measurement available for the attachment bolt distance? My Esprit is currently hibernating about 500km away from me. 

[rgh0]

The hole spacing on the orginal engine mount base plate that bolted to the chassis was 97.3mm centre to centre.  The replacement mounts i used came with 90mm centre to centre spacing so I had to slot them by about 3.7mm outwards at each end

[Finlandese]

9 hours ago, rgh0 said:

The hole spacing on the orginal engine mount base plate that bolted to the chassis was 97.3mm centre to centre.  The replacement mounts i used came with 90mm centre to centre spacing so I had to slot them by about 3.7mm outwards at each end

Well, that´s precise enough! 🙂 Thank you.

I now notice, that the current spec of the MacKay have some differences in dimensions, compared to the picture you have in your post. The bolt spacing is the same, but diameter is 11mm vs. 10mm. Overall width is 109 vs. 114mm. Maybe I´ll get the bolt holes filled and some material added to the ends, to strengthen edge of the new bolt holes.

[rgh0]

I made a bottom plate and 1/4 moon shaped top washer as you can see in my photos to reinforce the alloy ears on the mount after  slotting and this has worked fine for me

[tkathulevej]

BTW: Would someone have a set of the original engine stays (only the metal 'legs' attaching to the engine, rubber mounts not needed) surplus. I came to throw mine out by accident 😖

 

I yes, and if you want to sell, please contact me. (Living in Denmark, but i take they'd be fairly easy to ship)

 

Br /tka

Thomas Kjaer-Andersen