Lotus Elan

Mitchell Cotts Gearboxes

PostPost by: worzel » Wed Mar 30, 2011 9:47 am

Hi

A slight "rehash" of my previous posting on this subject. Having managed to get hold of a new MCT box at the right price I'm now hoping to pick other's brains on actually using it!

1st problem is the nosepiece0 Ford very kindly (!) have altered the diameter of the sleeve on the nosepiece which means that I cannot use the std release bearing/carrier and presumably fork. A couple of options possible I imagine-

Machine down the sleeve sufficiently (there is enough metal to do so) or-

Use a different fork/bearing/carrier.

Unfortunately I don't have immediate access to the std clutch fork so I don't know if the fork designed for the MT75 box is exactly the same in relation to pivot point/throw etc.

Any info on this from somebody "in the know"- possibly somebody who's used the std MT75 with the integral bellhousing might be able to clue me in- Spyder are quite difficult to get hold of and I get the impression from an earlier conversation that they only convert with MCT boxes using a co-axial release system (which I don't want to use).

Second question- the MCT box uses only two dowels to mate the gearbox/bellhousing accurately together- has anybody who's done a MCT conversion ever had a plate machined to fit into the recess on the front of the MCT box and to match the aperture in the bellhousing so as to enable a more centralised location system to be used?
All help mucho appreciated.

John
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PostPost by: GrUmPyBoDgEr » Wed Mar 30, 2011 10:02 am

Hi John,

postings about alternative gearboxes always attracts my attention because there's always tons to learn on here.
I can't help you with the questions you've posed apart from asking you why more than 2 dowels?
Standard engineering practice is 2 dowels, they are relatively tightly toleranced in order to provide the needed location.
Any more than 2 would demand very tight positional tolerances so that the parts would fit together without "fighting" against one another.
In one word - overkill.
I too have misgivings about concentric slave cylinders; one load of hassle removing the engine if it packs up.
The MT75 box normally has a cable operated clutch which I think is why others opt for the concentric clutch in our Elans.

In any case good luck, sounds like a good job.
John
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Editor: On Sunday morning, February 8th 2015, Derek "John" Pelly AKA GrumpyBodger passed away genuinely peacefully at Weston Hospicecare, Weston Super Mare. He will be missed.
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PostPost by: gerrym » Wed Mar 30, 2011 11:59 am

John, just a small clarification.

The MT75s from Scorpio donor vehicles had hydraulic concentric clutch operation as standard, plus starter motor on the Right Hand Side. The more common gearboxs from the Sierras had cable operation with starter motor roughly where the exhaust want to run in an Elan installation.

Cheers
Gerry
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PostPost by: GrUmPyBoDgEr » Wed Mar 30, 2011 1:21 pm

gerrym wrote:John, just a small clarification.

The MT75s from Scorpio donor vehicles had hydraulic concentric clutch operation as standard, plus starter motor on the Right Hand Side. The more common gearboxs from the Sierras had cable operation with starter motor roughly where the exhaust want to run in an Elan installation.

Cheers
Gerry


Quite right Gerry; just ANOTHER senior moment from me :lol:
John
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Editor: On Sunday morning, February 8th 2015, Derek "John" Pelly AKA GrumpyBodger passed away genuinely peacefully at Weston Hospicecare, Weston Super Mare. He will be missed.
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PostPost by: Mark B » Wed Mar 30, 2011 1:34 pm

Hi John,

As Gerry rightly said the sierra boxes used a clutch arm and scorpios a hydraulic slave. The mitchell cotts box was designed to replace the scorpio box as far as I know so I'm not that surprised you can't fit a clutch arm to it tbh... When they are used in westfields, they always use the scorpio hydraulic slave cylinder, as do spyder.

I agree with John P, had no probs with 2 dowels, standard practice & works fine, if it ain't broke, don't try & fix it!

Cheers,
Mark.
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PostPost by: bcmc33 » Wed Mar 30, 2011 2:30 pm

Three dowels is not a problem as long as two are 'diamonds' directed in opposite directions - à la machining locations.
However, I can't see why you would want three when two is the norm.
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PostPost by: worzel » Wed Mar 30, 2011 4:04 pm

Hi

Thanks for the input so far.

Dowels- I'm using (or rather intend to use) a Rocket to BDA alloy bellhousing. This would locate on a Type 9 gearbox via the bolted on nosepiece, the large boss of which provides accurate alignment for the bellhousing. However- the bellhousing I have uses two different sized bolts to fasten it to the box which means the holes top and bottom are of different sizes. So- to use this bellhousing would require both the two top holes to be opened out to accept the larger bolts that fit the MCT box and two would require even further enlargement to accept the two dowels fitted to the MCT box.

My reasoning was that if I in effect replicated the central boss that is present on the Type 9 box this would accurately locate the bellhousing to the MCT one thereby eliminating the need for the existing two dowels.

Concerning the clutch actuation- the MCT nosepiece metal sleeve is slightly too large to fit the std release bearing/carrier/fork to it. But- it does have ample thickness to permit it to be turned down sufficiently to permit the std bearing/carrier etc to be retained which makes for simplicity. I was just interested to hear how others might have addressed this particular problem.

Regards

John
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