master cylinders

[Dean]

Hello

i am restoring a 62 mini, originally it had nut top master cylinder which were in a bad condition. so they have had to be replaced.
i still want that look , and i remember someone on here, ( or one of the older mk1 forums) had machined/modified to top of a new master cylinder to take the nut top off the early master cylinders.

if anyone has some insight of ways this can be done it would me much appreciated.

thanks Dean

[Tim]

That modification (done by Bill Bell I think) is probably most suitable for the early ('59 and '60) master cylinder which has a removable threaded end to the master cylinder. The later version has a hexagonal top to the master cylinder, but its not a separate piece, they appear to have been done when the cylinder was originally cast. It would be difficult to modify a later tapered top cylinder to look exactly like the hexagonal top one unless you could put more metal on somehow, maybe with weld, or a cleverly made sleeve shrunk on.



Tim

[andy1071]

Tim,
-Just as a bit of (useless? ) information, the cylinder barrel was cold-forged. -A cylindrical slug of steel was placed on a die and a punch pushed/extruded it into the die. -It was with an almighty bang! And out came a nicely, almost finished, cylinder -which was actually then too hot to pick up....

The open end of the cylinder had the circlip groove machined, and a screw-thread machined on the outside. The mounting flange was then screwed into place. After which the little cut-off port and the by-pass port were machined.
-The little cut-off port (about 0.5mm dia, in new money) was pierced outwards from the cylinder bore, so there wouldn't be a sharp edge to damage the seal.

-In my time the end of the cylinders were conical, (on the left in the picture). I would guess that the hexagon form was there for when the flange was screwed on, and later found to be unnecessary (but I wouldn't swear to it!). -Or maybe it was 'tradition' from the earlier version with a removable plug...

After all this, the reservoir was soldered in place. -And I've always thought it was soldered too low -because the ports always appear about half-way up...!

[Tim]

Thats really interesting Andy. I had no idea they were forged, I guessed they were cast because sometimes the conical bit doesn't seem to be perfectly round and has the appearance of a parting line on it. I also wondered how the flange was fitted to the cylinder, they appeared to be pressed on then the cylinder sort of peined over.

Any idea what they were originally plated with? The plating place I went to said they didn't know what it was and couldn't replicate it.

Tim

[andy1071]

I believe the early coating was a zinc phosphate and oil process.

But I think this was not particularly nice for the environment (the council were very strict about waste from the factory). Not sure whether it was very nice for the workers either!
(-the 'problem' with a lot of plating/coating is that the process is nasty for the workers along with the waste, rather than the finished product; cadmium plating being one example)

Later cylinders were passivated zinc plated, either clear (silver) or yellow. -The yellow is more corrosion resistant. The more colour -the more resistance, olive drab being the most.
Probably a cheaper process too.

It just so happens that my father was the foreman in the plating division.
-Which I must point out, had absolutely nothing to do with the fact that I was the only apprentice who had the toolbox that we all made, passivated zinc yellow plated.....
(still have it, and it's corrosion-free )

-The peined over end stopped the flange from unscrewing.
I can't remember whether the die was split, which would explain the parting-line. -It would have to be to release, as the cylinder is parallel rather than tapered (easier than a bit ejector pin!)