Gallery, Projects and General > Project Logs
Small "Mill Engine Plant" (Display)
DeereGuy:
Peter very nice job once again on the write up. You do a great job of explaining everything very clearly. I have bookmarked this page for future reference. You should be writing articles for a magazine....
klank:
Thanks Bob - I am not sure how to respond to your very kind remarks without sounding callow.
I spent the last 35 years writing reports as an insurance company surveyor - from that experience I have found that there are times when you have to make the thing "interestingly readable" rather than just a load of mind numbingly boring stark facts.
In recent years, I once got ticked off by the underwriters for describing a building as "repellent in its ugliness" - better, I thought, than saying it was a "pile of badly assembled building materials in a random design"!
Prior to this was the time before the "Disclosure of Information" legislation came along. You could then couch the truth in all honesty - like "The policyholder appears to be as crooked as a dog's hind leg. Divest ourselves of this risk urgently". Technically that used to come under the heading of "Moral Hazard"!
Nowadays, this is not allowed.
I would love to write for Mad Magazine.
Peter
Stilldrillin:
Peter,
Some people have developed a good way with words. :thumbup:
Others have spent a working lifetime muttering at machinery........ ::)
David D
klank:
Ha Ha .
If in doubt, club it to shape, then debur and remove all sharp edges.
klank:
On the home stretch.
The piping and associated fittings were made from the copper brake - line and brass hex. Economic circumstances dictated that I had to go with what raw materials I have - even though it might be better to follow Bogs advice on smaller size pipe diameter. Anyway - I thought it might be interesting to see how the boiler steamed and the engine ran by using this larger pipe, with a modest steam dryer (not a superheater) to help improve some possible lost efficiency.
The dryer is simply a question of running the steam outlet from the globe valve back into the boiler cabinet via one of the portholes and directing it three times (in a sort of loop) up and down the length of the hottest part of the interior (between the water tubes) and over the burner and then down and out of the bottom of the cabinet by the burner, and back up to the engine/lubricator on the steam chest.
After some further thought, I felt that using the copper brake line (all I really had in stock) would be a good choice, if, for no other reason, that it is of much thicker gauge than the pipe Bogs suggested - it shouldn't come to much harm when sitting over the burner when lit.
It took an awful lot of continual re-annealing to get the pipe properly bent to where I wanted it - quite thick material!
Here is the dryer sitting amongst the entrails of the boiler and above the burner, inside the cabinet.
The water inlet pipe to the clack valve was coupled up underneath the board - within the "well" formed by raising the base on its outside walls.
The blowdown pipe was bent to shape and fiddled into place, emerging from the front of the board. I found it easier to make up the pipe runs first by using copper wire as a sort of template, and cutting/bending the copper pipe to match.
The engine exhaust was a simple right angle bent length of copper tubing to the front wall of the board.
The drain cocks were coupled to a short length of 1/4" copper pipe (off cuts left over from the water tubes), and brake pipe soldered into those and ducted out through the front wall.
The outlets were angled downward slightly and cut off. A piece of aluminium right angle strip acting as a sort of shield. (The top edge is horizontal, somehow the re-sizing of the photo makes it look "skewed"!) This is only a temporary measure - the exhausts etc. being fired down towards a bucket positioned below the bench for the time being whilst the plant is tried out. I appreciate this is a bit crude, but when materials come to hand, a proper sump/container will be fabricated.
The steam pipes have been lagged with string and wound in PTFE (plumber's) tape.
(I did remove the hanging whisker of tape, stuck to the lower water gauge fitting, near the fire-hole door - I understand that flame and PTFE tape leads to a very nasty acidic vapour! )
And here is an overall view of the complete outfit.
The original Stuart engine was made according to the recipe with a brass piston, in which I had grooved a single piston ring - using wound PTFE tape. This seemed to worke well when I ran it originally on compressed air.
I dis-assembled the cylinder from the trunk guide to properly pack the piston rod gland with graphited yarn and felt that the piston/rod screwed connection was not all it could be (made when I was still very much learning how to use my first lathe) so i decided to make a new piston/rod before re-assembly. I happened to have blagged a length of gun-metal rod of just the right diameter from another source, and decided to make one from this, cut with three oil grooves instead of a PTFE or graphited string piston ring plus a new stainless steel rod.
That done, I re-assembled the engine, re-packed the valve rod gland, re-timed it and ran it in very slowly on the lathe for a while, with plenty of oil.
I was then running out of excuses not to fire her up and see what happened.
The cat's entrails looked good, and the moon was in the seventh house, so I half filled the boiler and water tank, charged the burner tank with lighter gas, filled the lubricator with steam oil, opened the steam cocks, shut the valves and lit up the burner to a very low blue flame with the ceramic starting to glow nicely. Rotating the flywheel a few times showed no sticking in the engine.
The water bobbed up and down in the gauge glass, and then several drips started appearing from a few unions, but nothing daunted I carried on. When the pressure gauge needle started to move off the bottom pin, I opened the globe valve to allow wet steam into the dryer. No signs of leakage around the lubricator union, and so with the safety valve starting to fizz at 25p.s.i. I cracked the engine/lubricator valve open. Immediately I did this, the flywheel jerked round with a violent hissing and spluttering from the drain cock outlets. I rotated the flywheel a few turns and shut the cocks, and she sprang into life. Opening the engine valve further caused the engine to rapidly pick up speed, but the steam pressure seemed to remain constant. Then things got a bit more exciting as leaks rapidly appeared in the valve chest cover plate, the cylinder front cover and the union between the pressure gauge and the syphon, plus several pipe fittings. None of the glands appeared to leak luckily. Watching all these leaks, running the hand pump to maintain boiler water level and reduce the burner flame whilst disregarding my wet trousers became a most interesting period.
Fortunately, by that stage, the burner had consumed most of the gas in the tank and the flame died down without me having to shut it off.
I lifted the safety valve stem to release most of the pressure and then blew the remaining boiler contents down into the bucket.
That was overall a great experience.
I am sure those of you who read this and operate steam, must have had a similar memorable time on your first (semi) successful run. It sure beats the hell out of running on compressed air, and you get the advantage of a luvverly smell (hot oil and steam).
If it is of further interest to anyone, I will try and get a short movie using my little camera of the plant running after I have fixed a few leaks.
Thanks to all who have encouraged and offered advice - I am sure I have made some mistakes here, the overall result is not all that blingy, and certain circumstances have not allowed me to do all I wanted. However, I have enjoyed the build and got the pleasure I really wanted from seeing the little engine run as a first build, under steam from a home made boiler.
For those who maybe think about steam running rather than just compressed air - do give it a go - its messy, but well worth it.
Peter
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