MadModder
Gallery, Projects and General => Project Logs => Topic started by: vtsteam on July 18, 2014, 10:11:47 PM
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I decided to take a detour before going farther on flash boilers and make a little boiler I've always been curious about. It was featured as a project in a 1963 Popular Mechanics magazine, and more recently there was a U-Tube video of one:
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I had most of the materials to make it on hand. Nothing is particularly difficult about the construction, except the original safety valve. This was shown in rather vague detail. And the builder in the Youtube video substituted what looks like a commercial valve.
I have one I can use as well, but I was curious about building the version on the plans. It looked to me like it wouldn't work mechanically, so I figured I'd try to build it to see, and then substitute the purchased safety when ready to actually steam.
So I built the thing today and I was right. It can't possibly work as designed. I kind of wonder how many original readers attempted it and found it was whacked!
Sorry I don't have any photos until tomorrow, but to describe it, it's a weight and lever relief valve, that uses the head and smooth shank portion of a #8 wood screw as the lifting plug. This fits into a hole in the boiler pipe with "only 1 or 2 thousandths" clearance. This in turn is soldered to a pivoting lever arm, which gets a 1 ounce weight on the end.
Well, of course, there is no way the plug can lift without jamming, since it's solidly fixed to the lever, rather than pivoted.
This failed device got me curious about safety valves, and though I have a ton of reading material about making them in Model Engineer, and many books, I also like to work out simple calculators for myself.
I had a question about what the pop off pressure of this particular valve would be (if it had been workable), so I decided to write a simple spreadsheet calculator (attached below).
A #8 wood screw has a .164" diameter shank, so I used that in the spreadsheet, along with other plan dimensions.
(to be continued)
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Here's a the relief valve. Notice it says to solder the lever to the valve. Actually the arrow makes it almost look like the valve is soldered shut! Also note no dimensions for the lever other then overall length. And the width is indicated at 1/8", which also can't be correct. The weight is also specified as 1/2" brass rod -- well maybe that's depth but not the rod diameter!
Whoever the draftsman was for this project must have come in to work bleary-eyed the morning after, Maybe the copy editor had joined him!
(http://www.vtsteam.com/Boiler/PMReliefValve.jpg)
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Here's the first trial fit. Nothing has been screwed down yet. The relief valve is immovable as specified (silver soldered to the lever arm and set in a hole with .001" clearance.) I didn't actually use a wood screw, instead I turned a valve from brass stock.
(http://www.vtsteam.com/Boiler/PMReliefValve2.jpg)
Later in the day I unsoldered the parts, and re-grooved the valve. It now lifts the lever freely, though there is no yoke to capture it if it lifts too high, and the part could be lost.
Using the spreadsheet I wrote earlier, I was able to calculate the the pop off pressure of the design as drawn was probably under 10 PSI.
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I don't particularly like the hole in the pipe body being the valve seat, and the sub 10 psi relief is lower than I'd like. That is with the 1 ounce weight out at the furthest notch. The only solution is more weight, or a smaller hole. More weight starts to get cumbersome -- it might contact the boiler side.
I decided I'd prefer .125" to the .164" present bore . so I started to make a replacement screw-in valve seat of brass. I can then drill out the present valve hole, tap and mount the seat. The seat was threaded for 1/8" pipe taper.
(http://www.vtsteam.com/Boiler/PMReliefValve3.jpg)
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I've just watched the video again, and though the dial face is very blurry, I was able to make out in a still frame that the gauge is a 0 to 30 PSI model, and that he's running 10 PSI in the video, though he has a different relief valve.
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Here's a commercial ball and spring relief valve -- larger than needed for this particular boiler, but typical in design. In this case the spring is located in a housing above the ball. I like that particular feature.
(http://www.vtsteam.com/Boiler/ReliefValve1.jpg)
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Here's a classic style small boiler steam relief valve. It's the valve actually used on Polly by Tubal Cain -- David Stilldrillin recently featured one of these engines here on MM:
(http://www.vtsteam.com/Boiler/ReliefValvePolly.jpg)
This one requires a bronze ball and hand wound bronze wire spring. The ball is drilled and tapped to accept a guide rod. A cupped square hole washer is also required. The valve spring is located in the boiler, rather than externally.
These details make it seem difficult to me to build. I have no idea where I'd find bronze balls or wire, or how I would drill and tap the ball, and I don't like the idea of the spring being in the boiler as much as outside. Nevertheless I'm sure these give satisfaction -- just not what I'm favoring right now.
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If the ball is guided by a rod, then wouldn't just a regular cone/ taper turned on the lathe work instead? It does seem weird to use a ball.
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Hi Simon, a ball tends to be self centering, is easy to make a seat for (via light impact), and is considered to have less likelihood of jamming. You can buy balls ready made, high precision, and polished. Stainless is common, bronze isn't -- at least here.
So I was thinking this morning of how to use a stainless ball, in an external relief valve, that is a lever-weight type, instead of spring loaded, and one that doesn't require drilling a guide rod.
I kinda like the look of the lever type, and it's easy to change the relief cutoff pressure. Plus it's unusual.
Here's my present mockup cleaned up and with a weight installed using the Popular Mechanics lever valve design (sans solder) -- and it now works freely, and could probably be used as is.
(http://www.vtsteam.com/Boiler/PMBoiler.jpg)
But I'm still interested in making a valve of my own design, so I've been experimenting today with fabrication.
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So today I was thinking about how to solder a stainless steel ball to a guide piece, without getting silver solder on the working valve portion of the ball. We're talking about a 5/32" diameter ball (4mm).
I didn't have much faith that I could manage a strong butt joint to thin wire, or keep the solder masked properly.
Then I thought of a possible way to do it with strip brass, so had to try an experiment:
Spotting with 1/8" drill -- new valve seat also shown:
(http://www.vtsteam.com/Boiler/ReliefValve2.jpg)
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The ball in place. The real question was whether I could solder something this small without getting solder in the wrong place.
(http://www.vtsteam.com/Boiler/ReliefValve3.jpg)
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The setup for soldering. Flux paste and a tiny sliver of silver solder. I decided to heat from the bottom, as I was sure my torch would blow these bits right off the brass strip:
(http://www.vtsteam.com/Boiler/ReliefValve4.jpg)
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It worked! :ddb:
I did have to steer the silver with a tiny bit of wire because the flux boiled and moved it away from the ball. But it did work.
Here's a close-up outside in stronger light:
(http://www.vtsteam.com/Boiler/ReliefValve5JPG.jpg)
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(http://www.vtsteam.com/Boiler/ReliefValve6JPG.jpg)
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And how the valve would go together:
(http://www.vtsteam.com/Boiler/ReliefValve7JPG.jpg)
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I'm waiting for gauges to arrive, since I want to hydrostatic test the boiler, check the pop off of any relief valve used, And will also have a gauge attached when working. I'm hoping to be able to run 20 lbs pressure with this boiler.
From a little Internet research, 2" electrically welded steel pipe -- sch 40 -- has a working rating of 1500 psi.
It is pierced and tapped however in this design which would reduce that, and the sch 40 CI pipe caps have a working rating of only 150 psi.
So what I'd like to do is hydrostatic test the finished boiler to 150 psi and hold for a half hour. That should give me a reasonable degree of confidence for 20 PSI in use.
One aspect of this boiler that I do like quite a bit is the ability to remove the caps and inspect and clean it periodically. And the ability to replace the copper water tubes easily.
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Steve
To limit where silver solder flows to make critical or neat joints use Tippex type writer correction fluid. The solder will not wet where the chalky deposit is left
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I'll remember that, Andrew. I guess that must be the same thing as WhiteOut here.
Today was Fun With Sheet Metal Day! I managed only one small cut on the back of the thumb.....I did everything with snips and a couple of pieces of angle iron clamped in the vise by way of a bending brake. The boiler base came together surprisingly well, for me. I have hardly ever worked in the stuff, and this was pretty heavy gauge metal I had lying out back. A good day! :beer:
(http://www.vtsteam.com/Boiler/PMSheetMetal.jpg)
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(http://www.vtsteam.com/Boiler/PMBase.jpg)
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Well done the only thing with that ball is it won't be able to self adjust I'd rather have the ball being pushed into place.
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Not sure what you mean Tom.
I haven't built it yet. the ball and strip was just a soldering experiment.
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re. self adjusting:
A ball will tend to center (within limits) in a hole if the ball isn't constrained.
In a ball and hole valve, lack of constraint means play in whatever type of linkage there is connected to the ball. If there is no play, the ball is constrained.
However, the play is not only the means by which a ball will center, but also creates the need for self-centering in the first place. If a ball is perfectly aligned with a seat and the linkage has no play, the valve will be centered when closed
Play (or clearance) is necessary in a vertical ball and stem type steam safety valve, because the valve stem must be free to slide in the tube, despite corrosion, heating effects, lapses in lubrication, etc. Clearance can't be overly restricted. Therefore the ball needs to have a range of movement to self align. And in an internal valve of this sort, steam must also be able to pass alongside the valve stem. An external vertical tube ball type is somewhat better, but the ball must have a restricted clearance range in the tube, which amounts to the same thing.
In a lever type external ball valve any play will be located in the pivot. The circumferential play can be taken up by guides near the ball. Some clearance is necessary there, just as in the vertical tube and rod types. The radial distance is well constrained in this type of valve, but not absolutely so. The pivot will have a tiny amount of play. And to the extent that there is play, there is also the ability of the ball to self-align provided that any misalignment is less than the degree of play available for self-alignment.
Where there isn't enough play to overcome misalignment the ball will enter the hole off center. This will allow the valve to leak, but won't interfere with the safety of the valve. Generally ball valves are "set" by tapping in place to slightly form the seat, in which case the seat forms to the ball and corrects a minor misalignment, and sets a very slight taper in the seat. The same thing is done with a stem and ball valve.
If grossly misaligned, tapping in place won't work. Example: in a stem and ball type valve, If the stem is attached off center to the ball, it won't work. The solution is in carefully centering the stem when attaching to the ball, Likewise for a lever system it consists in properly aligning the lever when building.
Both systems have the same requirements for initial alignment, and both can use the advantage of self centering to a small degree.
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It's coming along well Steve :thumbup:
Tim
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I meant more along the lines of the comercial one where the ball gets inserted against the seat with a spring used for tension mind you a rod could be used to push the ball instead of the spring so you could use the weighted arm instead of the spring that way would prevent misalignment better.
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Hi Tom, I don't think I'm going to have a problem with misalignment, but probably best to make it first and talk about it afterward.
Today I didn't have much time to work on the boiler, but I did make a smokestack. I used a piece of fence post brazed to a bit of 1/8" plate that I had turned into a washer to fit. That's for a mounting flange.
(http://www.vtsteam.com/Boiler/PMStack.jpg)
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By afternoon I had some paint on it and mounted the chimney. Now thinking about the firebox and door.
(http://www.vtsteam.com/Boiler/PMPainted.jpg)
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VERY flashy :thumbup:
The heat losses on a design like that must be a high proportion of the input power. No real possibility of lagging, and a long response time due to the relatively thick wall of the boiler.
Looks the business though :bow: :bow:
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There's a copper coil under the boiler, and the inside of the firebox will be insulated. Not shooting for high efficiency, though, just playing. :beer:
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well done Steve....might have to dig the book out and have a play too....if time permits :Doh:
Pete
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Pete, thanks, that would be cool! I've got a gauge now, looking to hydrostatic test the boiler after I make a pump, still plenty to do.
Tim, sorry, missed your earlier post - thanks so much! :beer:
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Not much time today for fun stuff, but I did make a start on a hand pump. Rummaging around in my scrap barrel, I found this cutoff of what I think is brass. Could be bronze, I'm not sure. I have a small half nail keg of stuff like this -- mixed brass, bronze, and sintered bronze material that I got in an auction (real, not online) at a closed Hayward-Tyler machine shop.
Anyway, I thought this might work as a base:
(http://www.vtsteam.com/Boiler/PumpBody1.jpg)
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Milling a foot:
(http://www.vtsteam.com/Boiler/PumpBody2.jpg)
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And ended up with a blank for the base by supper time. Haven't quite decided how I'm going to do this pump yet, guess I'll figure it out tomorrow! :scratch: :coffee:
(http://www.vtsteam.com/Boiler/PumpBody3.jpg)
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Bah, chores all day, and then company for supper. Well, the last was good, but nothing much done on the pump except puzzling out how to do the valves with materials on hand.
I do have some stainless steel ball bearings 3/16" dia. and some 1/4" brass pipe for the pump body. But it's not exactly clear how I'll fit it as two check valves and pipe connections in the pump base.
I've looked in ME's and a few books for hand pump plans for ideas, but it's a subject that hasn't got as much attention as I would have thought. The few designs I've found in print often lack valve details, or are over-complicated or use odd thread sizes and large machined chunks of brass stock.
I want something simple, any threading ought to be managed with stock taps and dies and shouldn't require sculpting $50 of swarf out of a solid block. Ideally brass plumbing fittings might be used or adapted to the job.
I'm thinking that 3/16" balls would probably need a 1/8" bore at the seat. I have some brass compression to NPT straight adapters that have a slightly larger bore at the pipe taper end -- maybe I can sleeve it with some 1/8" ID brass tubing, soldered in as a seat.
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You guys just keep impressing me with all you do. Great job.
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Thanks Ginger Nut :beer:.
So this is the little design problem I'm thinking about. If you use a sliding ball as a check valve you need clearance around it to allow water to flow past when the valve is open. But if the valve is horizontally oriented, the weight of the ball tends to make it rest on the bottom of the large bore, off center.
To close, the ball moves to the valve seat end of the bore. The valve seat is a small hole, typically concentric with the bore. The ball closes the valve by basically plugging that hole.
But if the ball is off center, that means it must lift when it gets to the seat, since the ball was resting off center with the bore. Will that happen for sure? Seems like how surely it lifts depends on the amount of oversize of the bore, the size and weight of the ball, and how the seat is shaped.
If the seat is concave with a hole in the center, that would help the ball seat. But usually what is recommended for best seating is a convex seat with a hole in the center. I can imagine that if proportions of all these things weren't right, the ball might not lift and seat.
So the question is, how much oversize can the bore be to get good flow through the check valve for a 3/16" ball, when open, yet have the ball lift to the seat properly. And what shape and position should the seat be?
There are other design possibilities than the above:
1.) The sides of the bore could be grooved -- this would allow clearance around the ball for water flow, yet maintain a relatively tight guide clearance for the ball.
Question -- how to groove easily in this size valve (3/16" ball), and how to make a stop for the end opposite to the seat so that the flow can continue around the stop. Ball travel should only be about 1/32" to 1/16" by most accounts.
Possibilities -- maybe groove with a home made single toothed broach -- shaped like a chisel. Maybe use a pin as a stop in a cross drilled hole.
2.) The ball could be supported by a cage in a much larger overall bore to give clearance, but the ID of the cage could be close to the ball size to serve as a guide. Making and attaching a cage this small could be tricky/finicky.
Possibilities -- maybe a cage consisting of two hairpin shaped wires at right angles to each other. Maybe inserted in small holes in the seat and soldered there.
3.) Maybe the seat could have a double taper -- an internal convex cone with hole (volcano shape) and a larger concave cone lead in that lifts/guides the ball to center on the seat. This would require making a special cutter for this shape.
Writing this all out like this, it looks like #3 above would be the simplest. A home made cutter could even form the bore and the special seat in one operation if designed right
Still not sure what the optimum clearance would be for the bore vs ball size, though. I imagine even with such a cutter, it's possible to design a bore too large or too small to work well.
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I'm thinking maybe 1/32" oversize dia for the bore, so 7/32" for the 3/16" ball. Hope that's not too tight for good flow in this size valve. But I guess I could enlarge it if it didn't work well.
Well I guess for hydrostatic pressure testing of a small boiler, the flow rate isn't important anyway.
It would be nice to know what works well, though if I need a hand feed pump at some point...
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And now working through this aloud (or in print) I realize that such a small oversize might not require a special seat, since the ball only has to lift 1/64" to center.
I guess the only thing to do now is just try things and see what happens.
I'll try a straight seat first.
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Don't blow your self up Steve :zap:
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Nice job on the boiler Steve, it looks swell.
Andrew, like your tip on the tippex, have made a mental note.
Cheers David
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Don't blow your self up Steve :zap:
Okay.
This is just a hand pump for doing a static hydraulic test.
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Thanks David! :beer:
The pump check valve experiment has gone rather well today. Pictures later this evening....
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Couldn't you make it like carb float valve a spring loaded rod tapered to make the seal grooved or flat sides to pass the water?
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I guess you could Tom, but I made a free ball check valve today.
Here's how:
I started with about a one inch length of 3/4" round -- another scrap piece from my nail-keg 'o brass. Center drilled,
(http://www.vtsteam.com/Boiler/PMCheckValve1.jpg)
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Then drilled 1/8" through:
(http://www.vtsteam.com/Boiler/PMCheckValve2.jpg)
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Widened out one end to 7/32" for a depth of 0.75":
(http://www.vtsteam.com/Boiler/PMCheckValve3.jpg)
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Then I put a 3/16" ball in the wide end, and checked the depth. I wanted the ball to have 1/32" free movement to a cross pin which was to be made of .092" dia. stock -- a bit of brazing rod. I worked out the center location for the pin and cross drilled it in the mill:
(http://www.vtsteam.com/Boiler/PMCheckValve3a.jpg)
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Then back in the lathe, turned down one end to .375":
(http://www.vtsteam.com/Boiler/PMCheckValve4.jpg)
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And the other end also to .375":
(http://www.vtsteam.com/Boiler/PMCheckValve5.jpg)
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Turning done:
(http://www.vtsteam.com/Boiler/PMCheckValve6.jpg)
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Then back in the mill to add some wrench flats. I got to use one of my mill holders for my mill sharpening sander project to act as an indexing block while milling the valve here:
(http://www.vtsteam.com/Boiler/PMCheckValve7.jpg)
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Valve body done. After this photo I set the valve in the bench vise, dropped the ball in place and, with a drift, gave it a light tap to seat it.
(http://www.vtsteam.com/Boiler/PMCheckValve8.jpg)
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The brazing rod fit well and trapped the ball with just the right amount of play.
(http://www.vtsteam.com/Boiler/PMCheckValve9JPG.jpg)
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I threaded both ends 1/8" NPT pipe thread. Then it was time to seal the pin.
The check valve outside on a fire brick, ready to silver braze the pin in place:
(http://www.vtsteam.com/Boiler/PMCheckValve10JPG.jpg)
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Brazed:
(http://www.vtsteam.com/Boiler/PMCheckValve11.jpg)
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And done. It works great -- at least blowing through it. It seems quite free in the open direction, and instantly seals in the other. Horizontal orientation doesn't bother it. Quite happy with this result!
(http://www.vtsteam.com/Boiler/PMCheckValve12.jpg)
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Looks good well done!
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Thanks Tom! :beer:
Today I started work on the pump base valve. First I drilled through 1/8":
(http://www.vtsteam.com/Boiler/PMPump1.jpg)
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Then I drilled 7/32" for the stainless ball, as done yesterday. And after, opened out to tap size for 1/8" pipe thread:
(http://www.vtsteam.com/Boiler/PMPump2.jpg)
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Then I turned the base upside up, and drilled for the retaining pin and a hole to connect the valve passages with the pump cylinder:
(http://www.vtsteam.com/Boiler/PMPump3.jpg)
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I''m going to use a 1/4" brass pipe nipple as the pump cylinder. I cut the threads off one end and turned a small step in the end:
(http://www.vtsteam.com/Boiler/PMPump4.jpg)
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The pieces of the pump base -- I faced a small recess in the base to fit the step in the pump cylinder.
I had to offset the cylinder slightly to clear the retaining pin:
(http://www.vtsteam.com/Boiler/PMPump5.jpg)
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The pieces together and ready to silver braze:
(http://www.vtsteam.com/Boiler/PMPump6.jpg)
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Brazing complete:
(http://www.vtsteam.com/Boiler/PMPump7.jpg)
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I found an odd bunch of scrapped hex fittings in my nail keg o'brass, so I drilled one out as the pump cap, and tapped it to fit the 1/4" pipe nipple threads:
(http://www.vtsteam.com/Boiler/PMPump8.jpg)
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And finally, where I left off today -- the pump body and cylinder and attached check valve:
(http://www.vtsteam.com/Boiler/PMPump9.jpg)
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I finished up the pump with linkages and handle the last couple days. No photos yet -- maybe tomorrow. After a little fiddling tracking down connection leaks it worked perfectly today easily building up 150 lbs of pressure when tested with a few strokes. I didn't try more, since that was all I needed for testing the PM boiler, though I'm sure it could go to considerably higher. Handle pressure was light even at 150 PSI.
With the new pump working, I attached the pump to the PM boiler filled the system with cold water and applied pressure. Unfortunately the original style safety valve leaked at any measurable pressure. I tried lapping the seat with valve grinding compound, but it just wouldn't hold. That was okay, because I really wanted to make a ball valve along the lines I'd experimented with earlier. I didn't like the PM valve design from the start. I'm sure it would release, the problem is it leaks when closed.
Since I was binning the old valve, I decided I could just drill out the valve seat, tap for a screw in seat, and then put a pipe plug in there so I could test the rest of the boiler. So I emptied the boiler, removed all fitings, and spent a few minutes drilling and tapping. I reconnected everything and was gratified to see the gauge needle move steadily upwards. This time I was able to pump to my target of 150 pounds, but the boiler slowly leaked through the threads of the two pipe caps on the ends.
I wasn't able to hold pressure for long, but there were no other leaks through any of the smaller brass fittings -- only the two pipe caps leaked along the threads. I saw no structural problems, but I wasn't able to give the boiler a steady half hour test at 150 lbs, which is what I want to do. (My intended max working pressure is only 20 lbs, so this represents a large factor of safety.)
Now with plumbing normally you'd just tighten leaking pipe caps to get rid of the leaks. But here's the rub with this project -- it just isn't possible on the Popular Mechanics boiler design. :bang: :bang: :bang:
The reason is there is a coiled water tube under the boiler, and their fittings are tapped into the underside of the caps. Therefore, tightening the caps rotates the coils in relation to the fittings on the top of the boiler which are tapped into the pipe. Well, unless you could do a full turn to tighten. I couldn't. The most I could manage even with an extension on the pipe wrench was 3/4 turn. :hammer:
Then while trying to tighten the second cap, the pipe slipped in the pipe vice, and the jaws ruined one of the tapped holes in the top of the boiler. :hammer: :hammer: :hammer:
So I realized, the boiler had to be scrapped. Even if I had managed a full turn on both caps, the boiler would have ended up shorter, and would no longer fit the base I made for it. A lot of work went into fitting the boiler exactly to the top of that base. :(
I guess the only good part today is I know how I can now improve the design.Obviously the water tube coil fittings should go into the pipe body of the boiler, as they do on the top. Not the into pipe caps. The caps can then be tightened at any time and also easily removed for inspecting or cleaning the boiler, without disturbing any of the smaller fittings.
As it was before, if the boiler was taken apart for inspection, chances are the caps would have had to be screwed on tighter -- and the same positional problem would have arisen. I think one of the really nice features of this boiler is the ability to open it up -- and in fact disassemble it completely.
Problems? The boiler may have to be longer to fit the same length of copper tube underneath (although, I may be able to coil it differently and get the same heating surface on the same length boiler-- I have to think about that) . However a couple inches longer boiler wouldn't be a big problem, other than having to make a new base for it. Stresses and material strength would be about the same as long as the diameter and construction is maintained.
The basic good news today was that none of the tapped fittings leaked and all stood up to 150 lbs for as long as I could hold it. I pumped up several tmes. That's where my main concern was in the PM design. I'd still like to do a half hour test with the finished boiler, but I have more confidence now that these fittings tapped into the steel pipe will be fine for the working pressure I have in mind.
Anyway, that's today's results. A couple steps back, but I think I see the way forward. Just a lot of work to have to repeat.
Basically I have a new pump. But not a boiler.
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Today was the opposite of yesterday! :ddb:
I woke up at 4 A.M. with a sudden realization that I could save the boiler if I just drilled out the bashed 1/8" pipe thread hole to fit 1/4" pipe. Duh!!! I guess I was just tired and disappointed yesterday not to have thought of it.
So I went to town, bought two more pipe caps, and screwed them on. I re-drilled and tapped the bad hole and installed a pipe plug temporarily. With the new caps screwed tight with pipe compound the boiler still fit the sheet metal base. Yessss!
I looked at the old copper coil and realized I had stretched it out to fit the first boiler, all I had to do was compress the coils a little, and put two new flare fittings into the bottom of the boiler pipe to fit. The coil length would remain unchanged. Wooohoo!
So, I connected up the hand pump and pressurized the new rig to 150 pounds, and it slowly dropped -- over maybe 5 minutes. I tightened up the copper coil nuts and the next reading stayed over 100 pounds for 5 minutes. The pipe caps leaked a drop every half minute or so, but it was lunch time so I left it at that. Byt the time I got back the leak had stopped and the gauge needle was stationary at 50 lbs.
I pumped it up again and saw that now only one pipe cap was leaking an occasional drop, So I let it drop over another 20 minutes figuring the leaks would probably self seal at this rate, and indeed they did. I was finally able to do my 150 lb test with the needle stationary and no leaks for a timed half hour. Yahooey! :med:
Finally I dug out my commercial safety valve -- it had a 1/4" base which fit the new tapped hole. Basically I now had a boiler AND a pump, unlike the day before.
The valve was set for 100 psi, unfortunately and I need one for 20 psi. so it wasn't usable today. It is an internal spring and ball type, and though adjustable, would really need a new spring to bring it down to the low range. Nevertheless I had fun pumping up the boiler with cold water and setting different pressures with it and watching it blow.
Sorry no pics today either -- tomorrow for sure. :beer:
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Nice thing you didn't need to go back further. but I agree. Design could have been different.
About the design. I once used one fire extinguisher cylinder for a pressure tank of a compressor. I tought I was smart, drilled hole on the shell and hard soldered a fitting for a water cock. It corroded in ten years. Maybe having fittings on the cap will give there some extra material? I was thinkking of suggesting using T-unions on both ends and shortening the middle part, but looks would be very different. T-unions are pretty stong and they would allow easy internal inspection without upsetting coil fitting.
... Nevertheless I had fun pumping up the boiler with cold water and setting different pressures with it and watching it blow.
So, it was like watching paint to dry :lol:
Pekka
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Thanks Pekka!
By the way, the copper coils now go into the pipe body, not the end caps, now. I think it's an improvement to the design.
re. corrosion:
Galvanic corrosion can happen over time between dissimilar metals, and how fast depends on the water quality and metals involved. Welded or brazed tanks and fittings can allow this to happen out of sight. I read a recent account online of a model locomotive boiler that had passed club pressure tests for years, yet the owner found he could poke a screwdriver through the boiler wall in the last inspection, due to internal corrosion out of sight.
I would say that this little boiler has 4 very good qualities in that regard that I've come to appreciate as I've worked with and thought about what I originally considered to be a "crude" design:
1.) The boiler is WAY over built. The walls are .154" steel, and the end caps considerably thicker cast iron. There's a lot of material that would have to be eroded away to be able to stick a screwdriver through it from the outside.
2.) The end caps can be removed for direct inspection of the entire interior No need to also poke around with a screwdriver outside. Any wasting away or corrosion products at fittings would be immediately evident on inspection.
3.) There are NO welded or brazed boiler joints for hidden corrosion to occur in.
4.) All parts of the boiler are removable and replaceable, the fitting seats and threads can be inspected easily. All fittings can be removed in ten minutes time with 4 wrenches. Every part could even be replaced once a year if desired for a very small total cost. A new boiler body itself is just another $8 pipe nipple with a few tapped holes in it.
I think the key to lifetime longevity re. preventing corrosion with this one would be to make sure it is dry when not being used -- which is fairly easy with such a small boiler with a big fill plug removed and a little warming from a propane torch before putting away.
I think it's a very different case from larger traditionally constructed live steam boilers, or home made compressed air tanks, for that matter.
I'm very impressed with the concept of this small boiler, though not with the execution in the original design. The safety valve was unworkable as shown, and the fittings seated in the pipe ends discouraged inspection and sealing if there was a leak. There was no pressure gauge indicated and there was no accompanying article on building and using a hydrostatic test pump, which I think is essential for initial and periodic testing. Remedy these things, and I think the design has a lot of advantages.
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Steve, presumably the boiler (and hence the screwed end cap joints) go above 100 C as it contains water / steam under pressure. What are you using as your sealing compound on the threads? Many proprietary ones top out at 100 C. I suppose Teflon tape is an option that will take the temperature, but I have an abiding loathing for it and use one of the Locitite thread sealers these days for oils, air and gas - but they fall off at about 100
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Well I'm not happy with that one aspect either,Andrew -- I'd prefer a non-PTFE compound, but they are all the fashion these days -- at least in the hardware stores I have locally. So yes I used some Teflon tape and also some teflon containing paste.
Why I don't like or want PTFE:
True it can withstand more than 100C by quite a lot, but if you exceed its breakdown temperature (over 250C -- say the boiler running dry) it is hazardous stuff. I'm scrupulous to remove any of it showing beyond any fitting in the firebox.
Fitting threads themselves are shielded from direct flame and are technically water cooled to a little above the boiling water temperature (@20 psi in this case). But still, I don't like using it at all.
If anyone here knows of better alternatives, I'd appreciate hearing them. I'd be happy to remove the present stuff.
I have read in older references that sal amonniac was used to induce a quick rust seal for pinhole leaks in steel pipe joints -- but I do wonder how easy the end cap fittings would be able to be removed afterwards.
Also in older references for model boilers, I've read of using just old thickened paint -- but ditto on removal for that. Of course I don't really know how hard it would be to actually break the joints free with either, after a year,
And also Andrew -- even if a paint or other sealant broke down with heat -- the residue might still seal the joint.
I don't know -- this is definitely an area that could use improvement, and all suggestions welcome.
ps. of course there are many proprietary "boiler seal" and treatment products on the market for hydronic heating and steam heating, and also automotive radiator stop-leak products. These could be added after assembly. But being proprietary, I kind of wonder what I'd be getting with something like that. Could be fine or could be downright evil stuff.
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Here are a couple photos. Pump parts:
(http://www.vtsteam.com/Boiler/PMPump10.jpg)
The plunger was 3/8" cold rolled rod that just coincidentally fit the 1/4" brass pipe nipple used for the pump body. No machining necessary.
I turned a groove at the end and added an O-ring.
I also changed the cap, originally from brass scrap, to a simple pipe cap, drilled to .375" and some cotton string added for packing.
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And here's the pump assembled and painted:
(http://www.vtsteam.com/Boiler/PMPump11.jpg)
ps. re. the plunger -- I'm going to make another of stainless steel -- just found an SS bolt to turn down for the replacement at the hardware store.
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At work on our low pressure steam we use Key-Tite or never-seez on all threaded joints, my employer,s procedure calls for Teflon tape and Never-seez but I omit the Teflon tape. When we install unions we soap up the threads too so it comes apart easy.
One advantage of Key-Tite is that it never sets.
Ket-Tite is a registered Trade mark name.
Anthony.
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When I re-plumbed my launderettes years back I did it in stages. Water distribution originally was in 2" screw galvanised. Getting a good seal onto fittings as I gradually replaced it all with copper over a few nights (keeping shop open during the day) was a nightmare. You could wrap as much teflon tape as you like round the male before screwing, and it would still leak - quite repeatable! I reverted to 'Boss White and Hemp' which instantly cured all problems. It wasn't until a bit later I found the reason. The hemp, put in dry, expands if a leak wets it and seals the joint. Sometimes the old ways are the best.
Not sure if 'Bosswhite' got across the great pond to the US but is a whiting and linseed oil composition. Now banned here for potable water.
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Thanks Anthony, I looked it up and it only seems available from the manufacturer with a $66 minimum quantity. :(
I also found this non Teflon stuff which seems pretty good in the specs:
http://www.gsasupplyco.com/gasntnonsofs.html.
Andrew -- is "whiting" white lead in linseed oil? I actually have some of that as an old unopened tub of traditional gesso.
ps. some forms of hemp are also banned here.....
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Whiting is calcium carbonate, CaCo3 Chalk, the "hemp" is sometimes known as skrim in the UK I know what it is in French "fillasse" , I found oakum as a translation on the web. Wind the threads of hemp round the screw thread (previous in a clockwise direction as on would with teflon. It is very different to Lead oxyde. The jointing compound (or it's modern equivqlent)should be available in plumbing suppliers
Regards, Matthew
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I pretty much hate teflon tape on any sytem that has small orifices, screens or such. I have cleand up fules systems, pumps etc. because someone had a bright idea. Bits of it always ends somewhere where it does most harm. Here probably into safety valve.
Teflon tape works on reasonably good brass fittings, when it is taped over male thread same way than you thread the union over it. DO NOT turn back at all when tightening. If turned back, it needs to be completely removed and replaced. Most good fittings works without it. Cast iron unions/iron pipe (central heating) seems to work best with traditional hemp/white paste. But pressure is not much in central heating system water circulation.
Pekka
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Thanks Anthony, I looked it up and it only seems available from the manufacturer with a $66 minimum quantity. :(
I also found this non Teflon stuff which seems pretty good in the specs:
http://www.gsasupplyco.com/gasntnonsofs.html.
Andrew -- is "whiting" white lead in linseed oil? I actually have some of that as an old unopened tub of traditional gesso.
ps. some forms of hemp are also banned here.....
Steve, I think others have answered this before I got to it !
The chap I bought my last house from 32 years ago was the heating and ventilating contractor who installed the plumbing in Terminal 3 Heathrow. He swore by just using oil based gloss paint on screwed joints, which seems to work. Mind you looking at the state of the house plumbing when we bought it I shudder to think what the airport terminal pipes are like :ddb:
He got his come uppence though - BOTH his wives turned up at his funeral, and oh was there a fuss :clap:
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Thanks guys, I should have looked up whiting. Oakum/hemp I'm familiar with.
My father in law once brought me a full gallon of raw linseed oil he didn't want any more -- looks like it's from the 50's judging by the label. I've used boiled linseed oil before because it air dries easily, but not raw, so I've had no particular use for it either.
But maybe now, to make up a once a year removable traditional putty it might be just the thing. I'm wondering however -- whiting -- I haven't seen it anywhere in the local hardware stores as such, but we do have something which might be the same thing -- plumbers putty -- oil based chalky and smelling of linseed oil, and also very similar, window glazing compound -- white chalky, linseed oil-ish smelling, and supposedly non drying.
Last night I ordered some of the Gasoila non-teflon pipe compound, since I found it for $5 plus change on Amazon in a small quantity. The specs say good for potable systems, NFS approved, and good to 400F. But, still, whatever is in it is unknown and it's reaction to high temps above that also unknown, while whiting and oakum are very well known ingredients, and non toxic no matter what the temp.
You know Andrew I came across the paint as joint compound recommendation elsewhere in old writings re. model engineering. I was tempted by that, too.
so many choices.......
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With most of the other problems solved, it's back to the relief valve today. I decided to do an outside barrel ball and spring type, but to use as much ready-made brass plumbing as I could, to keep with the overall theme -- which turned out to be quite easy.
First I turned a bit of brass to the ID of a 1/8" brass pipe nipple:
(http://www.vtsteam.com/Boiler/NewReliefValve1.jpg)
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Checking fit:
(http://www.vtsteam.com/Boiler/NewReliefValve2.jpg)
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Drilled to 1/8" for the steam passage:
(http://www.vtsteam.com/Boiler/NewReliefValve3.jpg)
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I drilled a recess of 3/16" then added a bevel out to the edge of the valve seat plug. These two steps will help guide the 3/16" stainless steel ball to the 1/8" valve seat at the center.
(http://www.vtsteam.com/Boiler/NewReliefValve4.jpg)
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This is a better view of it:
(http://www.vtsteam.com/Boiler/NewReliefValve5.jpg)
And with the ball in place:
(http://www.vtsteam.com/Boiler/NewReliefValve6.jpg)
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Then I silver brazed the valve seat plug into the pipe nipple:
(http://www.vtsteam.com/Boiler/NewReliefValve8.jpg)
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With the ball in place I formed the valve seat to the ball with a light tap on a drift.
(http://www.vtsteam.com/Boiler/NewReliefValve7.jpg)
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With the valve body and seat done, I started on a plunger to take the spring pressure and push the ball into the seat. I decided to use 1/8" brazing rod as the stem. Here I'm turning the plunger end:
(http://www.vtsteam.com/Boiler/NewReliefValve9.jpg)
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And here's what it looks like with the rod in place. The bevel will help center the ball:
(http://www.vtsteam.com/Boiler/NewReliefValve10.jpg)
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Here's how the plunger, spring and ball go together. The plunger has been brazed to the stem already:
(http://www.vtsteam.com/Boiler/NewReliefValve11.jpg)
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Finally, I drilled a 1/8" standard pipe cap to .136" to give good clearance on the 1/8" stem:
(http://www.vtsteam.com/Boiler/NewReliefValve12.jpg)
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Here's the completed relief valve assembled with a 1/8" to 1/4" pipe bushing:
(http://www.vtsteam.com/Boiler/NewReliefValve13.jpg)
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I'm looking forward to doing pressure tests on the valve tomorrow with the new hand pump. If all goes well after adjustments, we may be steaming!
(http://www.vtsteam.com/Boiler/NewReliefValve14.jpg)
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That looks quite impressive your safety valve looks to be quite natural and you could also adjust the spring tension easily with a spacer.
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Thanks Tom, I;m going to re-thread the top end of the barrel from 1/8" pipe taper thread to 3/8" straight thread so I can screw down the cap to adjust pressure somewhat. Probably put a thin locknut there if I do so the adjustment can be locked. Right now the friction of the taper thread works, but there's little adjustment.
The main adjustment on this type of safety valve, though is the spring itself. The current spring is a hardware store type. I have a few others with different rates that I bought today, but all are spring steel. Once I find the right one for the working pressure, I'll either order a stainless version from McMaster Carr, or if I have the right SS wire, try winding one myself.
I was wondering where I would find SS spring wire, and then remembered I have quite a selection of saltwater stainless steel fishing leader stock, which is about as stiff as music wire. I think i would make good springs.
Looking forward to tomorrow!
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It looks real swish in black and gold; the best colour combination.
Have you got an engine to run with it?
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Oui!
several....
Although I really want to make a new one :drool: perfect excuse.
Might just try the old Tesla disk turbine first, though I have a feeling it won't do anything with this little (and this wet) steam. But you never know until you try. But it sure won't pose much resistance -- it has a nozzle efficiency of a soda straw. I have 4 piston steam engines of various sizes, another one half built, ......and well my top secret tunaturbine, the antiTesla, which has never been tried on steam, or indeed publicly revealed. I don't know if I dare speak of it even here...
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Well it sounds fishy!
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......and well my top secret tunaturbine, the antiTesla, which has never been tried on steam, or indeed publicly revealed. I don't know if I dare speak of it even here...
Does it looks like a tunnymelt? :lol:
I have heard about flyreels (fly fishing) which brake fails when SW fish takes off. Maybe same thing or form?
Pekka
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Looks the part Steve.
You could eliminate the spring entirely with a weight on the stem
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Here's a quick test of the new Popular Mechanics boiler running a Westinghouse type twin, and showing the release valve blow off. The valve pops twice, a little below 20 lbs because of boiling pressure peaks in the copper coil below, but opens steadily at 20 psi. Unfortunately you can't read the gauge easily since it's out of focus -- the second marking is 20 lbs.
ps because of the frame rate of the video it strobes the engine rotation and it looks very slow. The sound gives you a better idea of the actual speed -- about 750 RPM I think.
FUN!! (Lot's more planned, too). :ddb:
https://www.vimeo.com/102665448
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Very cool! That engine looks great too.
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Boiler seems to work good nice engine too!
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:headbang: :headbang: :headbang: :headbang: :headbang: :headbang: :headbang: :headbang: :headbang: :headbang:
A lovely project, well completed, and I'm sure it will be very useful.
Tim
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Thanks mates! :beer:
Andrew, I thought about a weight but worked out earlier that it would take 4 ounces on a 1/8"" bore for 20 psi, which is rather a big lump, even if lead!
The earlier lever style had a mechanical advantage so the weight could be more reasonable in size.
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How can you make a new boiler without wanting to make a new engine?
(http://www.vtsteam.com/Boiler/TwinCase.jpg)
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These details make it seem difficult to me to build. I have no idea where I'd find bronze balls or wire, or how I would drill and tap the ball, and I don't like the idea of the spring being in the boiler as much as outside. Nevertheless I'm sure these give satisfaction -- just not what I'm favoring right now.
I know this is an old post, but since I missed it the first time around, I thought I should take the opportunity to chime in now.
First, brilliant build. Thanks for sharing.
Nowadays it seems that just about every podunk town has a piercing/tattoo parlor on every corner. Those places will sell piercing jewelry consisting of a couple of steel or titanium balls, threaded to accept a post. Sizes range from 3mm to 8mm diameter ball and with a post length of up to ~24mm. This jewelry is available for somewhere in the €5.00 range.
You can use the threaded balls and posts in valves, governors, or put 'em in your :bugeye:
Just a thought.
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So there's a challenge for you miniature engine builders - make an engine entirely from metalwork intended as 'body ornamentation' (shudder - I hate the stuff )
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I've never had a tattoo, basically because I'm torn between that and accupuncture and can't make up my mind about it. So josh you're saying I ought to visit one of these places and ask to look at their titanium ..... uhhhh .....spheroids?
:lol:
Well seriously, that might work for one of the Tubal Cain type small safety valves, if of the right size.
While I'm sure it's sufficient, I don't like his design as much though, because the spring (and stem) is on the boiler side of the valve, instead of the outside.
In the external spring type, the steam has a clear passage through the valve orifice and seat, the parts count is lower, the ball can rotate to even out wear, and the spring compression (and steam pressure) are somewhat adjustable, and the spring can be replaced and inspected without removing the saftety valve body from the boiler.
I suppose you could use a stem and ball running the stem and spring externally, I'm not sure what the stem would do unless you had a guide bore for the stem before the spring, and that could jam with debris.
Personally, I think a simple floating ball and external spring, is not only the easiest to build, but probably the most reliable for this small size and type of boiler. That's just my opinion. :beer:
ps. I think a proper seat for the ball is important to avoid leaks. The seat should be convex conical -- like a volcano in shape. It's true that to finally finish the seat writers generally call for tapping a ball lightly on the seat to form a very slight impression, but it may not work as well on a simple flat seat in this size valve.
You can make a cutter to from the seat easily on the lathe in drill rod/silver steel and harden and temper ( or not probably if just cutting a seat or two in brass).
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Well, now that you've got me thinking about it, I just thought of one advantage of the internal spring and stem type. It's relatively tamper proof.
To alter it you'd have to remove the valve body and change the spring and retainer on the stem. Many of these small boilers were intended as toys, and a tamper proof safety valve is pretty desirable in that case.
The worst for tampering, is the external weighted type, like the original PM Boiler. Kids could add weight. But of course, it didn't even work as drawn.
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Photos restored after Photobucket broke links.
Video also fixed.....
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SNIP!
Nowadays it seems that just about every podunk town has a piercing/tattoo parlor on every corner. Those places will sell piercing jewelry consisting of a couple of steel or titanium balls, threaded to accept a post. Sizes range from 3mm to 8mm diameter ball and with a post length of up to ~24mm. This jewelry is available for somewhere in the €5.00 range.
You can use the threaded balls and posts in valves, governors, or put 'em in your :bugeye:
Just a thought.
Josh, thank you for that. :mmr: :nrocks: :mmr: :nrocks:
I have a few microscope attachments with broken operating levers. The levers comprise a thin stem with a tapped (about 10 BA) ball (about ⅛" diameter) on the end. OK, I OUGHT to be able to make replacements but parts that small are a bit fiddly and time is short. Maybe you've just alerted me to a workaround.
Hey! Where did that 'spell Check' button come from? I've never noticed it before!!!!