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MG Midget and Sprite Technical - Interesting concentric clutch conv. 4 A series GB

An interesting concentric clutch conversion for A series gearboxes from down under.

http://www.ebay.co.uk/itm/concentric-clutch-kit-Austin-Healey-Sprite-MG-midget-Morris-Minor-A40-Farina-/172450394566?hash=item2826d831c6:g:naAAAOSw2xRYVa0Z

Rob


Rob aka MG Moneypit

Okay to use on a finger clutch cover but not the Minor std clutch.
J L HEAP

Interesting !

£380 ?
Laughable!

My Concentric clutch conversion (for a T9) cost £35
Guy W

It's a simple idea that could be replicated by an enterprising enthusiast. A SAAB 9000 concentric slave + release bearing is about £90. I used one on my type 9 conversion.

BTW, I know someone who has a Burton setup on Type 9 and 1098 engine and he has retained the pad on a standard clutch with no problems.

Rob
Rob aka MG Moneypit

Or just keep it simple with no clutch cover mods with one of these.
Alan


Alan Anstead

Or for 948 / 1098 modify the carbon casting to one of these. Direct replacement.
Alan


Alan Anstead

If Rob is talking about me, it wasn't quite straightforward. The nose of the Burton setup fouled the centre hole in the pressure pad, so I had to get the hole enlarged to clear the release bearing guide tube. This was done by Steve Kiel on his lathe. Steve also shaved 1/8th" off the circumference of the driven plate which is from a Hillman Avenger and is 7.1/2" against the 1098's 7.1/4" pressure plate. This was done in case the slight overhang caused a reduction in clamping force as the clutch wears.
The original 1098 3/4" tandem master cylinder was retained.
The Burton concentric slave cylinder and release bearing fitted without any spacers and the initial gap between bearing and pad was spot on at about 8mm.
The setup has been working problem free for about three years and 15,000 miles.
Bernie Higginson

I cannot work out why they have used a piece of ribbed alloy plate to make their replacement front cover for that A series kit? Why not just flat - it is thick enough not to distort. I cannot see the advantage in that - unless it was just a scrap piece they had lying around.
Guy W

Its not ribbed its the way the milling cutter has moved across the aluminium probably on a finishing cut - the beauty of a CNC machine
Martyn Wilks

The concentric release bearing is consistent with modern clutch release systems. It avoids the pad sliding laterally as it is levered into place.

Pricey but the right idea. A better upgrade would be using the concentric release system and a ball bearing release bearing. It would not die on the vine if pushed into place instead of hitting the cover assembly contact pad at an angle.

Glenn Mallory

Glenn,

I would say that concentric clutch release systems have been around for more than 50 years now as the roller release bearings, even if lever operated, were kept concentric with the clutch on a guide tube fitted to the gearbox.
David Billington

It will be more difficult to produce this conversion for the Minor/Sprite/Midget box than the T9. What would interest me would be details on the hydraulic ratios in so far as would hydraulic master cylinder bore diameter is recommended etc.
Daniel Stapleton

Daniel,
When I built my concentric slave system for my T9 I used an off-the-shelf Ford Fiesta slave. I was concerned that the movement created when operated by my standard 1275 master cylinder might either be insufficient, or too much for the 1275 clutch.

I tried unsuccessfully to find figures on the relative volumes and to calculate the distance the slave thrust bearing would move. So I rigged up a bench test with an extended hydraulic pipe from my car to the Ford concentric slave on the bench. To my surprise the actual movement was about 11mm - pretty well perfect first time round so I put the system together. Its been fine for the last 65K+ miles
Guy W

Also, I can add that in my type 9 conversion I used exactly the same slave cylinder (SAAB 9000) as in this kit. It operates a standard 1275 clutch minus the pad. I found that with the standard (disc type) dual master cylinder there was a tad too much throw so I drilled the master cylinder push rod attachment point to the clutch pedal to increase the leverage (reduce the throw). I had to crank the push rod to keep the travel parallel to the cylinder centre line. It should be a lot easier on a later car.

In the end I had reduced the total throw by about 1/2 and it was really good. The bonus is it feels like a modern car clutch, quite light.

Details if needed.

Rob
Rob aka MG Moneypit

This thread was discussed between 20/12/2016 and 28/12/2016

MG Midget and Sprite Technical index

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