further to my request for replacement Webster bits, David McC (thanks David) asked if I could use JB Weld for the repairs on the mag pot metal. Though I'm aware of JB Weld, I've never used it and would be interested to hear what others experiences of using it are.
I would be using it to fill oversize threaded holes in the body of the mag in the hope of redrilling and tapping . The metal has cracked around the holes to add insult to injury :-( .
Apparently Fowler owners get a special discount on the stuff ;-).
Its a very good product that I have used successfully for cylinder bore scores. BUT I have never yet found an epoxy that will stick to MaZak alloy (English for pot-metal :-) It should be OK in a thread but the cracks seem to spread far and wide under any sort of pressure, and since its probably due to crystal growth cannot be cured. I assume you have mailed Bill L and Ted B for advice? Failing which I think you have an interesting piece of milling for your evening classes regards Roland
What is it exactly that makes these American alloys so self destructive? My father has a Dixie mag on which the alloy parts have all but reduced themselves to dust and I have a Webster mag which is suffering in a similar manner to Arthur's. The stud holes have been drilled OS and helicoiled (badly!) but one still gets the impression that it is just about hanging on and I never dare tighten the nuts up any more than a light nip. Doc Schuster, in his book "The Webster System" suggests clarting the threads with epoxy to stop loose studs working any looser.
Perhaps one just gets that impression as the Americans seem to have taken to the stuff very early on and were thus victims of a rather imperfect state of the art.
Its nowt to do with country. Mazak is a dodgy alloy that hovers on the borders of its eutectic. A slight deviation form the ideal mix and its buggered. ttfn Roland
See Roly's reply also, but it is a pretty crap alloy which is affected by moisture and oxidisation, at which point the matrix crumbles away to the white dust we know and love.
Protected by painting it lasts well, but so much of the equipment that uses it as a material was low-cost anyway, and protection wasn't though about.
Peter
-- Peter & Rita Forbes snipped-for-privacy@easynet.co.uk Engine pages for preservation info:
I've got a carb and manifold from a 1904 Minerva which I have had for thirty years. It was in perfect condition until I left it on the back of the bench for a few weeks. It must have been in contact with some other metal it did not care for and the corner of the float chamber has rotted quite away. Only took (say) six weeks! This was thirty years ago and it has not changed at all since the rotting incident.
Very strange ...
My dad used to refer to zinc-based alloys as "the metallic equivalent of chocolate fudge" which I still think is rather good.
Another of my hobbies is 3 rail Hornby Dublo as made by Meccano from 1938 till about 1964. They used a lot of Mazak which they made themselves. After the second WW, the production was improved, but quite a percentage of pre-war stuff (Trains Dinky toys, etc.) can and does fall apart, shatter, distort and/or turn to powder!
There seems to be some truth in the rumour that although Meccano had cracked the mix successfully, at the end of the day (or week) when the foreman was busy elsewhere, the tidying up would be finished faster if things like the metal banding from pallets and other odds and sods were thrown into the melting pot instead of removing to the disposal section!
These additions would be enough to throw the Mazak well off it's limits but this would not take effect for some time after the product left the Factory
It is very unusual for post war Meccano products have fatigue problems, (they may have moved the bins nearer the foundry!) but I have seen one "Dinky Disaster" which was an aeroplane that had accidentally been dropped from a couple of feet onto a hard floor. It shattered almost into dust. Poor guy was devastated!
Simon Taylor (Don't drop your Dinkies on the floor Mrs. Worthington)
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