First serious steam engine build.

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zimirken
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Re: First serious steam engine build.

Post by zimirken »

I thought about the expansion of the aluminum exhaust. The headers are steel, and the pipe is copper. I thought about making the mounting bolt holes into slots. That would also allow more flexibility in gasket thickness. In the end I didn't, but I can always make new headers or modify the current ones.

I'm currently just using a shot of regular machine oil into the intake before every air test. However, I've been thinking about lubricating on steam. I'll probably start with making a simple displacement lubricator, and then upgrade to a mechanical one from there. Initial steam tests will probably be saturated steam but I would eventually like to pass a steam line through a boiler flue to dry it out, no more than 350f or so max temperature. I have to think about steam cylinder oil. I could purchase some online, or maybe go to the nearby scale locomotive track.
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Bill Shields
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Re: First serious steam engine build.

Post by Bill Shields »

you are on the correct track...almost

mounting bolt holes as slots only ensures that the problem becomes one of the gaskets.

what you is some expansion loop technology between the exhaust ports....

once you get past around 250 F, you need special oil or it is going to coke up on you....machine oil is just fine for air....
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zimirken
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Re: First serious steam engine build.

Post by zimirken »

Avocado oil has a smoke point >500f, I could mix that with some tallow for initial use. It seems like many sources of steam oil have dried up in the last few years. Thermal expansion may be a problem, however it's likely the upper solder joint would be the one to fail, and when it does, it probably won't leak enough exhaust steam for me to really care much. I could always make some caps with o rings for sealing and only solder the bottom manifold.

In any case. Taking a small break from the engine itself, since it's at the point where I need to start thinking about mounting it and transmission. I've got some #40 roller chain left over from a previous project. I made a 3d printed sprocket with pinch based mounting bracket but it doesn't seem to get enough of a grip on the shaft to transmit the full torque. I'll have to think about either machining it out of aluminum or getting some steel shaft collars and welding a purchased sprocket onto them. I might try some locktite first though. That's how the flywheel is currently attached, and it seems to work well. The rear wheels I have on the frame are made in two halves, with a 5 bolt pattern holding them together. I printed a spacer collar and a sprocket that bolts up to the wheels using the existing holes and it seems like it will work well.

I also have to start thinking about accessories, like a steam whistle, and brakes. I had some random pushbutton valve laying around that I got a long time ago intending to use it for a steam whistle. I made a bracket for it that holds a lever and allows it to be mounted to something. I added some curvey touches to it to make it look at least a bit more stylish.
20220509_154147.jpg
Also, my burner, which is a modified propane weed burner, currently just uses a needle valve to control it. This valve is quite small, and I really wanted a long stem on it so I don't have to pipe the propane up to a controls plate and back down. So I made a little hat for the knob that allowed me to extend it with some 5/16 threaded rod. I need to solder a bolt to the valve body so I can rigidly mount it to the frame. In testing I could really use a pilot light too, but I'll think about that a little bit later. This is probably the first time I've really used a lathe on this project. In the model shop at work we have a large 10"-ish lathe with no digital readouts and terrible runout on both the 3 jaw and the tailstock, and a very nice new small lathe that's always busy with work stuff. So I try to avoid doing lathe work, which is easier when the CNC has the precision to bore holes and stuff.
20220510_085529.jpg
I also scavenged a bunch of aluminum from a bin of old junk at work that's getting thrown out. Which more than recoups the metal I used in the project so far. It's big chunks too, like inch thick plate. There's a lot of holes in most of it, but there are enough intact sections to make it worth keeping.
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Bill Shields
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Re: First serious steam engine build.

Post by Bill Shields »

Plastic sprocket on the output may not be the best of ideas...consider a heavily loaded engine being suddenly unloaded...and the possible consequences.

Metal sprocket with a keyway and set screws is a better way to go.

You can get small quantities of steam oil from many locations...including clubs.

Take a baby food jar with you and go begging... :lol:

Cannot say that I have ever heard of anyone using avocado oil in a steamer... wouldn't it make the engine smell like a guacamole food truck?
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zimirken
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Re: First serious steam engine build.

Post by zimirken »

Keyways are nice, but I have yet to come up with an easy way to cut internal ones. Also I've found that pinch collars hold on to shafts plenty good. After all, that's how half of the crankshaft is built. The eccentric uses set screws, set screw pits in the rods, and locktite to stay together. The other side is a pinch bolt style assembly. I'll be using the pinch bolt side for driving the wheels.

I'm having trouble finding information on sizing the displacement lubricator. I suppose I could whip one up out of pipe, maybe add some gasketed bolts for draining and filling. I could use a needle valve for the connection to the steam line. I can't find any info on how to size or how to adjust the output though.
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Harold_V
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Re: First serious steam engine build.

Post by Harold_V »

zimirken wrote: Thu May 12, 2022 11:06 am Keyways are nice, but I have yet to come up with an easy way to cut internal ones.
If you have a vertical mill, it's not all that difficult to hand grind a slotting tool. It cuts on the end, not on the top, as you're used to with a parting tool. By holding it in the quill, you can easily stroke a keyway in components. If the keyway terminates (doesn't go through the entire bore) you can drill a hole in which it ends, or simply use a sharp chisel to remove the resulting chips at the end of the keyway.

H
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rmac
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Re: First serious steam engine build.

Post by rmac »

Joe Pieczynski has a couple of videos showing how to grind and use homemade broaches in the mill. I suspect that Joe's showing essentially the same thing that Harold is talking about.

-- Russell Mac
zimirken
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Re: First serious steam engine build.

Post by zimirken »

Well, the steam test was less than successful. I could barely get it to turn over due to hydrolocking, and when I finally did the eccentric strap broke. Oh, and it sprayed hot water all over me the whole time. It didn't even run long enough to take a video. I made a new eccentric strap out of aluminum, but I need to add cylinder drain cocks.

I don't have much material in the cylinder to tap into, so they will have to come in through the top and bottom caps. The caps aren't thick enough for much more than an m6 hole in the side. I couldn't really find any tiny ball valves for a reasonable price. Normally these drains would use a taper plug valve. I suppose I could order a taper plug reamer and give making my own valves a try. Otherwise I was going to get some 1/8npt ball valves and make 6mm-1/8npt adapters.
https://www.amazon.com/Tapered-Chamfer- ... 79-3508807

I'll also probably be wanting to insulate my steam lines and the cylinder a little bit. I've got a big roll of aluminum foil backed fiberglass for doing stuff like that.

On the plus side, my engine still runs great on air with the new eccentric strap. I also made a steam whistle, and it sounds really good.
https://imgur.com/3pbbolB I adjusted it since this video so it's less hissy. I just need to weld some small rods on the outside to keep the two parts in line with each other.

I made a crude displacement lubricator by drilling and tapping some holes in pipe plugs, and using bolts with gaskets. I may weld a washer on the bolt heads to make it easier to empty and refill.
20220517_163224_rotated.jpg
During the steam test, I had some boiler issues though. My current test boiler has one large 2" flue going through the middle of it. I'm using a modified weed burner to heat it. On the first steam test it was slow to come up to pressure, and the flue gas was quite hot. Obviously it was being overfired. Since then I managed to find some 3/4in stainless steel strips. I folded some up into a zig zag, weaved two zig zags together, and pulled them through the flue tube. This caused a new issue - back pressure. The burner wasn't working very well until I grabbed my forge blower (my wife's old blow dryer) and held it in just the right spot to force air through the boiler. Once I figured this out it came up to pressure in like half the time it previously took.

So, I need to add a steam blower, I need to find or make an electric stack blower, and I need to route the engine's exhaust into a blast pipe. For the steam blower, do I need to make some sort of venturi or something? Or do I just stick the 1/4 copper tubing into the stack pointing up and run it to a needle valve? Same question with the engine exhaust blast pipe.
Last edited by rmac on Wed May 18, 2022 4:11 pm, edited 1 time in total.
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Bill Shields
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Re: First serious steam engine build.

Post by Bill Shields »

suggest something like a crab pot burner with a dozen small burners instead of one big one up the middle.

you need distributed heat....
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James Powell
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Re: First serious steam engine build.

Post by James Powell »

Zimirken,

Had you started your approach like this, rather than asking boiler questions 1st, I would have been a lot less hostile- I've just seen enough stupid, and enough 1 question wonders, to not have a lot of patience for it.

You are charting your own course- which can result in good, or bad. There's a lot of advice available here, and by showing you are _doing_ something, you get far better results than by just dropping a question first off that can lead to unexpectedly poor results (hmm...yes, tom thumb's fireman...)

I have some experience with coal fired semi flash boilers, though not forced circulation, and a fair amount of experience with full sized watertube boilers. I also have a little bit of experience with small propane fired boilers (4" OD firetube boilers or so...).

Given that you have had some success, what I would suggest is to isolate one side of the equation from the other- build a vertical firetube boiler, propane fired, to start with, and muck around with the engine design feeding it steam from the boiler. I know, it's "boring", but...experience suggests that having more than one radical new idea at a time is a sure way to have your head explode from the difficulty of figuring out what is causing the problem.

Sensible Solution to Thing's Boiler question:
ImageDSC_0005 by Peach James, on Flickr

was to move to a firetube boiler from the semi-flash coal fired boiler, at least until we got reliable "performance" out of Thing. "Performance" in this case means hour long trips around a 1200' track :)
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Bill Shields
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Re: First serious steam engine build.

Post by Bill Shields »

You may want to consider that what you are attempting to do should not be to reinvent the wheel. There is little about boiler design (successful and otherwise) that has not already been tried and we'll documented at the industrial level.

A Google search for a reference book on boiler design "boilers: types characteristics and functions" by Carl D Shields (an industry standard textbook since the 1960's) would be well invested reading.

It is reasonably safe to assume that if McGraw Hill books spent the time and $ to publish it ..there is something there worth printing...and reading

Enough of these books were sold to Hartford Steam Boiler inspectors to pay for the house in which I grew up -> with enough left over for college tuition for my sister and me.
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zimirken
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Re: First serious steam engine build.

Post by zimirken »

Well, it runs, and quite well. I added a steam blower, just the regular 1/4in copper tubing pointed up the stack with a little bit of crimp on the end. I also routed the engine exhaust up the stack. I still need an electric blower to start it, but once it makes steam I can switch over to the steam blower. Also, the engine exhaust creates quite a draft too. I didn't have a chance to do any testing over 20 psi, so I'm still nervous that it won't have enough power to move me, especially with a 60psi boiler rating. I suppose I can always gear it down, but I am hoping for something a little bit faster than a traction engine crawl. I will be looking towards adding a second cylinder in the future, as I do want it to be self starting.



Alas, I couldn't do a running test this weekend because the sprocket I ordered was for 40 chain, but apparently the chain I have is 420 chain. It's the same pitch, but it's thinner, so I have to turn the sprocket down a bit on the lathe this week.

As far as the cylinder drains go, I ordered some small 1/8in npt ball valves and made some passages in the top and bottom cylinder covers. They work great, although I may make some sort of restrictor nozzle for them as they flow too much at full open. I also mixed some beef tallow with some straight 30 weight lawnmower oil, and it seems to emulsify with water how it's supposed to. That will work for now.

I also want to figure out something besides threaded rods and nuts to hold everything together. They work well structurally, but controlling the distance between the top end and bottom end using nuts is not ideal. I'm thinking about getting some tubing that closely fits the rods, cutting it to the exact lengths it needs to be, and sandwiching it in the middle. Also, I need to add a reverser lock, as it's currently relying on the pinch friction from the bolts and lock nuts in the linkages to stay in place.
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