Regarding the earlier response of "gasket material". There is a company called James Walker that manufacture gaskets and related components and materials. From their website, their UK office is in Cheshire but a search on Walkerite does not provide any results. Possibly an enquiry may result in the current equivalent material being identified.

Not my area of interest or expertise; but I note that the drawing asserts its insertion to be Important

… Presumably because of its thermal properties, and/or its mechanical ones.

One would hope that Martin Evans included a textual explanation … somewhere !

MichaelG.

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Edit for clarity: __ If Mr Evans only included it as a convenient ‘packer’ then its important characteristic might be the 1/64” thickness.

Edited By Michael Gilligan on 15/02/2021 08:49:18

I agree the gasket is intended to prevent heat transfer in this small engine,Why not use gasket paper,might have to use nearest metric equivalent for thickness,a local motor accessory shop sells a gasket paper which is very tough,it resists tearing much better than the old type gasket paper,or try to get some of the graphite coated,grey colour gasket material which has been asbestos free for many years,suppliers to the vintage vehicle owners is also good source ,I would suggest a visit to an auto jumble but thats not on at the moment with cov 19 lockdown.

Success or failure in this gauge can rest on the rate at which heat is lost in the cylinders.

Personally , I would make as much of the frames as possible in that area 'disappear', ie a hole.

The 'gasket' material thickness is probably vital to stop 'clashing ' somewhere.

This is the other half of the OP's drawing:-

As the only dimension shown is the thickness of the gasket material, one must assume that this is necessary for motion clearances.

Reasons for including it might be a. the original drawing of the cylinders was incorrect or b. that the cylinder castings, originally meant for a different design, would not clean up to the size required here.

Having read many of Martin Evans's articles I conclude he would appear not to find it easy to acknowledge a mistake and would either ignore it or suggest an 'improvement' had been pointed out to him – and at least two other well known authors would seem to not offer any corrections at all!

I would think that commercial gasket material would be best here being less compressible than my goto oiled braille paper.

Edited By Nick Clarke 3 on 15/02/2021 09:56:05

But not by him!

Cynical, Moi?

While normally I would agree wholeheartedly with you, in this case the loco was designed by Martin Evans and built by Severn Lamb for a French customer in 1965 although the design was not published in ME until 4 years later.