Repairing a high quality model marine engine

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bogstandard:
Now to get this steam control valved fixed. I have decided to try the fix I mentioned in the last post, and if it won't work, only a few minutes will be lost.

The first job was to clean up the end where I had to hacksaw the lever off.

This is the first part of the fix, skim 0.015" (0.4mm) off the end of the internal spigot. This is also where the o-ring fits into, so that will allow the ring to sit further out and push against the spool face to form a seal.

The same amount was taken off the flange face. By doing this, the spigot will still sit in the same position, but the ring will be deeper in the bore, so allowing the makeshift fix of a shim under the spool to be redundant.

Now you can see what has happened. The o-ring is holding the spool away from the flange which the spool was previously rubbing against.

When assembled completely, this gap here will be closed, forcing the ring against the spool and forming a steam tight joint.

So to final assembly of the valve. A dollop of good quality steam oil was put into the bottom of the chamber.
Because this valve is using very fine tolerances to work, I won't fit gaskets, so each joint face was painted with Hylomar jointing compound, and the valve was assembled. The spool now runs between the bottom face of the chamber and the o-ring, as it should do, instead of between the shim and the spigot face.
I checked the turning pressure and it was spot on, a nice constant drag as it was rotated. So it looks like the fix has definitely worked.

Seeing as I hacked the operating lever off the valve, I had better make another.
A bit of scrap stock was selected for the job.

A few minutes on the mill had the makings of a handle. If you can just see the scribings on the blued up bar, I have drawn up what I want it to look like, to put it into the same operating area as the old one.
Because the engine will be radio controlled, there will be holes drilled into the arm that match the standard centre and hole pitches of a servo control arm (the black bit). This will make setting up a lot easier.

After a bit of manual cutting out on the mill, the handle is finished. The handle can be mounted in any position so that it suits the operator how he wants the way for the valve to work.
Now if the valve starts to leak steam after the o-ring is worn out, take off the handle, remove four small screws and the ring can be changed. Because of the way Hylomar works, it should be able to be reassembled without changing the gasket cement, because it never sets. So five minutes at the most to change the ring

I now have to make some missing parts, so I will make those as per the plans, but because it will be radio controlled, I have to design a friction slip joint for the reverse operating lever. That will be a bit of trial and error, but it shouldn't take too long, I have ideas in my head already.

Bogs

John Stevenson:
John,
have you seen these quick clamps ?

http://www.arceurotrade.co.uk/Catalogue/New-Products/Vices-and-Clamps

two up from the bottom. No real defined use but different uses for different people.

JS.

bogstandard:
John,

I had seen those bits, but couldn't really make up my mind if I really needed any.
I suppose because they are so cheap, they are not worth making a copy of, so next time I order, I might get a couple, just in case I ever have a use for them. You never know, they just might turn out to be a tool you can't live without.

John

Darren:
They look very handy to have, I like the way this chap is using them to reference his center tool :thumbup:

http://www.homemodelenginemachinist.com/index.php?topic=4294.30

I think a set will be going on the order list :thumbup:

Brass_Machine:
I love to see a craftsman at work. I believe your customer picked the right man for the job!

I do love to see posts like this. While it may seem to you that you are just doing simple tasks in a common rebuild/repair... the viewing collective are picking up many hints and tricks. Thanks John!

Eric

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