I recently bought a big Carette 677/13
Here as seen in the catalog of 1911
It was sold with the remark of a leaking water gauge…
This is how it arrived…
The machine was still in a very good patina, but still someone did try to repair it in the past, using some crude methods.
The whistle and outgoing steam tap where soldered to the boiler.
And a crack in the nickel boiler / burner house ring, was repaired by soldering a thin brass plater on the inside of the ring.
After some consideration, I decided to leave it as it is as part of it's history
Big issue was the water gauge.
Even before I took it off, you could see that the original screws where replaced.
Screws on water gauges are always a big issue.
Since I had my first antique steam engine, I had to deal with that.
For a beginning collector this can be a real nightmare, as a repair like that require some skill.
Problem with most of these, is that they are made of soft brass, that is nickeled.
They tend to break, this due that they can't stand pressure and heat changes, so not idle for holding a water gauge.
What makes it even worse is, that when the closing washer around the glas it self doesn't seal off, people tend to put even more pressure to these screws.
And that is fatal of course.
I will come back to the washers later, but first the screws.
Sometimes a big issue can be, what kind of tread they used for the original screws.
This can be metric, but also withworth or some other od tread size.
So If you want to replace a screw, keeping the original size, sometimes asks for real tradesmen knowledge.
That's, why often, you see such bad repairs, where someone just wacked a non fitting entirely differed size screw in.
Let me tell you, that this never ever will work, and that it will end up in disaster.
Even danger, as these screws can become lethal projectiles under steam pressure.
I'm all in, for if it comes to replacements, to find or make an original fitting screw.
But If the tread in the boiler, is damaged you have 2 choices.
Most difficult, and time consuming, are special made screw inserts.
These must be custom made on a lathe.
And to fit them in, the old hole must be drilled out, and the inserts soldered in.
It is a specialist job, but it allows you to keep the original screws if they are still good.
The easiest way is to retap in a slightly different bigger size.
Let say the original was M2, you retap to M2,5.
I also advice, to keep the extra bigger size, to a minimum.
By this I mean, If the original is a M2, not to go for a M4 replacement.
A 0,5mm increase is more than enough
Downside is, you need new screw.
Also the original screws of that time, had a sharp edge, giving them a cylindrical look, like this one, of a other engine…
Modern screws however have rounded edges giving them more the shape of a balloon, as where replaced on this engine…
And I really don't like that, to me it gives the appearance of a cheap repair.
So what I usually do, is cut off that edge on my lathe, turning them looking like the original screws.
Coming back to my restoration It seems that they taped a M3 hole to fit in the new screws, a bid big if you ask me.
Anyway after reshaping the heads of the screws.
I reassembled it.
Coming to the issue of the washers…
The black washer on the left was used.
Now, out of experience those aren't any good, because they seal off bad.
This makes people, put more pressure to the spanner screws, with a breaking result.
The washer on the right is what I use, they fit very tight to the glass, and being flat, fits tight to the boiler.
And with little pressure the spanner screw close everything off.
An other thing I also use, in combination, is Loctite SI 5990.
It's liquid sealer, that when dry, tuns into a very heat resistant rubber.
And I have a strong feeling that Loctite SI 5990 is almost the same recipe the manufacturers used.
I also apply Loctite SI 5990 on the screws, as the screw tread hole is an opening into the boiler.
This being done I immediately noticed that the M3 holes tread was gone on my engine.
Even cold water poured out on them.
So disassembling it again, I went for the only sensible thing to do.
Drop the screws into a spear box, and make incerts and use new M2.5 stainless screws.
The screws heads where adapted to look like old ones, and stainless steel is much harder to break.
The incerts where closed incerts, by this mean, once soldered in, there is no direct opening anymore to the boiler.
So this way you avoid the chance of water leakage over the screws.
Anyway with everything cleaned this was the result…
Only thing left do was to put it under steam pressure…
https://youtu.be/gwYOrEzYhTECheers,
Danny