Here are some progress photographs that I uploaded to-day of the work as it is progressing on my Stuart Score/504 based plant that I plan to use to power a small computer. The most recent pictures are progress up to this afternoon; as you'll see, the next remaining job is the pipework.
I tried my hand at silver soldering this afternoon, and, with some assistance from my father (who pointed out that the reason that the first attempt was not as successful as hoped was because I needed to turn up the blowtorch), managed to get some good soldered joints. Hopefully, I'll have the pipework finished in a few weeks, and will be ready to test the engine under steam!
G'day James. Going well One thing I noticed in your photos was the feed water suction line going through the furnace. This will most likely give trouble because the water will vapourise and cause a vapour lock in the pump. I can see you are enjoying it. Regards, Ian
Thank you for your replies: I am glad that you find it interesting :-)
Ian - as to the pipe going through the furnace, that is a deliberate means to try to pre-heat the feedwater so as to reduce pressure losses when water is fed into the boiler. It is somewhat experimental: by my calculations, it should work a little like a pop-pop boat: the pump end will act as a seal, so the water vapour/steam, which will be at higher pressure than the surrounding liquid water, will force its way out back into the tank, creating a vacuum in the pipe, which will then cause more, colder, water to be sucked in, that way maintaining an exchange of water between the hot firebox pipe and the cooler tank that should help to keep the water in the tank warm.
When the pump is operated, the water will not have time to turn to vapour or steam (the pipe is below the level of the ceramic burner, so should not act as a flash boiler since the head will be indirectly, rather than directly applied), and the warmer water from the tank, warmed further by being passed through the firebox, will be fed to the engine.
If it doesn't work that way, I can always re-route the pipe :-)
Dick - my next project will be using a Stuart S50 (run from the same boiler) to power a shoe polisher: a somewhat less ambitious task, but one no less useful ;-)
I spent about two hours to-day out in the rain silver soldering the brass nipples to the pipes. I forgot to add detergent to my flux, which was then diluted with rainwater, so it was not always easy, and I had to re-solder several; however, I got there in the end.
I had evidently mis-measured some of the pipes, such that, when I came to fit them together with the unions, they did not fully meet or line up properly. They were close enough to screw in, but looked as if they'd leak if I were to use them. To remedy that, I used two spare O-rings that I had to fit inside the nut and over the pipe: they were both a tight fit, suggesting that the steam seals should hold.
Here are some photographs of my progress. I am just about to capacity test my boiler to see whether it needs an inspection certificate to run in public - since it produces 60psi (3 bar), any capacity over a litre would require a certificate, so I am going to see whether a litre of water is enough to fill it to overflowing or not :-)
Any comments on the pipework would be much appreciated.
Update: The boiler devoured a litre of water and was still barely half full - the capacity of the 504 I therefore estimate at 2 litres. Does anybody know of any good places to get a test certificate in the Thames valley?
I am also having trouble with the drain cock that I fitted to the gauge glass to act as a blowdown valve leaking. There's no trouble with the thread, which is sealed with an aluminium washer, but little drops of water leak through the bottom of the valve itself, as if they manage to get around the metal tube inside. I tried wrapping PTFE tape once around the metal tube, which seemed to work at first, but it still leaks: just more slowly. Any suggestions on how to resolve that one?
No 1 - lose the tread tape from off the tapered plug of the valve - it will only make things worse.
No 2 carefully clean out any bits of tape that have found their way into other parts of the cock
No 3 the retraining nut on the back of the plug also acts as an adjuster - you need to tighten it just enough so that it doesn't leak but is still able to move.
If all else fails, you may need to lap the plug into the cock body - use brasso for this - a smear on the plug and rotate, rotate, rotate in the body til your arms are ready to drop off - freshen up the brasso from time to time, and CLEAN IT VERY CAREFULLY when you finish.
Hi James The Thames Valley is a big place, where abouts are you and then we might be able to help. Of the top of my head are Malden DSME- primarily railway orientated, Staines MES-dont know much about them, Guidlford MES- an all round society with a variety of intrests, Surrey Society at Leatherhead,various around West London, Reading SME and the list goes on. You would have to be a member for your boiler to be tested that however will bring other benefits such as access to workshops, tools and the experience of the membership. Otherwise do a google searcch for Farncare and pay the money, which is probably more than the membershiop fee for a society.
Thank you all for your replies :-) Tel - I've just tried your "Plan A" suggestion, of removing the tape and tightening the nut, and it seems to be working so far: the cock is now stiffer to turn, but it's still turnable, and it doesn't seem to be leaking, although I'll leave it a while to be sure.
As for clubs, I was somewhat unsure about joining one because I'll probably have little time to be able to attend meetings and such - does that matter? I will have a look for "Farncare".
Edit: After leaving it for a few minutes, a small amount of water is oozing out of the sides of the valve. Time to track down some Brasso, I think...
Last Edit: Mar 16, 2008 11:11:05 GMT by jamespetts
I tried the Brasso lapping. I spent a great deal of time turning the thing around and around with Brasso inside, then cleaned the Brasso off. After doing that several times, it seems a little better now, but it still leaks, alternately out of the side furthest from the handle, or out of the bottom. Also, lapping it seems to have caused the handle to be pushed further in so that the hole no longer fully aligns with the shaft such that the flow of water is reduced when it is open.
However, after using the Brasso, it is an awful lot shinier!
;D You're getting there mate. Yet, it's only natural that the plug will seat further in to the body as you lap it in. If it's only a small leak, such as in the pic, I wouldn't be too concerned at this stage - it may well take up when you get it fired up and some pressure on board.
Also, don't worry too much about the bit of misalignment of the holes caused by the plug seating deeper, it's not too critical and the hole can be opened out a bit later, with a tiny round file, if needed. Wouldn't fool with it at this stage tho'.