Work on the Boiler continues with the finishing and installing of the Economiser (pre-heats the incoming water to the boiler using waste heat from just before the flue) and the Superheater (adds energy to the steam on the way to the engine, again using waste heat from the flue gasses.
Milling and Drilling the Econo/Superheater Headers
As noted in the last post, I decided to mill the recesses in the two halves of the headers, as there is a lot of metal to shift, and with the “ripping” milling cutters this was by far quicker. (some pics)….
While we await the 600+ cut and bent boiler tubes from the other members of the “Boiler Collective” beavering away in Sussex, we went back to the engine to try and close off the final list of “to do” jobs….
I think Cleading is the official word for this, even though WordPress objects! Continue reading →
While we wait for the plasma cut boiler plates and housing to arrive I went back to a job that’s needed doing for a while on the engine; the Lubricator.
Approaches to lubrication
There are several approaches to lubricating a steam engine, from a hand-held oil can (tends to be a bit erratic, and you chop the end of the spout off in moving parts) thru oil wicks, to pumped lubrication. I felt that a pumped system was the way to go.
There are 11 bearings that need lubrication in the engine (3 main bearings, 2 big ends, 2 little ends/crossheads, and 4 eccentrics). Actually, there is cylinder lubrication as well, but we are going to deal with that via a separate displacement lubricator which injects oil into the incoming steam (a sort of 19-century “posi-lub”! Continue reading →
So, following some communication with the steam boating forum we are all agreed that the Edwards Air Pump as drawn is missing anything to hold the valve-plate in place, or seal its contact with the pump body. This means that:
The whole valve tends to move up and down with the piston rod, (and I think this needs to be a “good” fit to prevent leaking round the pump-rod, so this is unavoidable).
There is nothing to seal the lower valve plate (the one with the holes) where it sits on the ledge of the pump body…
So, my solution is to:
fit a gasket under the valve plate
make and fit a nylon block to hold the plate down – made 10 thou too long, so that the top cover provides some “squishing pressure”
As other members suggested this may help pump performance by removing “deadspace” (but it is beyond the valves so I am not sure if this is correct), and secondly it needed to be made in a way that ensured the outlet port is not cut-off if the block rotates; so, as can be seen in the pics below, I have made it with an exhaust annulus and internal ports to the valve chamber cut in the bottom…
I think this approach will also prevent the valve opening too far….. a test in the kitchen sink proves that it all works!
Here are some pics of the block and completed pump assembly.
Well it seems I have not posted since November and the arrival of Befur’s trailer. Since then a lot has happened (so Happy Xmas, and Happy New Year)… I have had the fortune to be made redundant, and have (with Louise’s kind support) agreed to turn that into retirement – so from the end of February there will be no more working interruptions, and as I am only “on call” now, progress should be faster. So with the shingles finally subsiding, and hopefully the last of the winter colds and the left shoulder starting to free up, there can be no more excuses – so 2015 looks bright indeed 🙂 Continue reading →
I have puzzled over the drawings of the Impulse Valve for a year or more, and spoken to others who can make no sense of it.
Well finally last week while mulling the design over with a friend, he (I think) correctly fathomed how it is meant to be built and operate…
As drawn there appears to be a plunger in a tube which is operated by a press button. There appears to be no way that this would operate, as it would just admit HP steam to the chamber formed between this plunger and the end of the valve body….
The explanation is that this plunger is in fact a tube! Thus when depressed the steam is admitted to the end of the valve assembly, and then passes down the tube to the valve chest/cylinder. There are hints in the drawing that this is the game, but some of the views are incorrectly drawn which leads to the confusion – and actually I am not even sure it could be reliably constructed as drawn.
I think it would still be hard to make this valve steam tight, but in operation this might not be a practical problem…. Thanks to Neil Davis for figuring this out!
*Simpling or Impulse
In the ME words, Mr. Leak complains that many people incorrectly describe the Impulse Valve as a “Simpling Valve”, and he argues that this is wrong as it does not make the engine run as a simple (which is true) but just introduces a HP steam feed into the LP valve chamber to push the engine off HP TDC if it stops there.
He’s right in the description of what it does, but knowledgeable friends of mine tell me that within the road steam community (Traction Engines) these valves on compounds are always known as “Simpling Valves”… so maybe we can continue to use the term…