First serious steam engine build.

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Bill Shields
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Re: First serious steam engine build.

Post by Bill Shields »

All this really neat technology to get right back to the mid 1800's :mrgreen:

What would Mathias Baldwin have created if he had a 3D printer available instead of boring cylinders with a piece of an old file jammed into a wooden boring bar?

It is really cool to see your creativity and tech applied to old concepts.

Your observation about valve gear travel applies to most. -> not just Hackworth
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NP317
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Re: First serious steam engine build.

Post by NP317 »

Creative work.
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zimirken
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Re: First serious steam engine build.

Post by zimirken »

I finally got my linear bearings in and it does run a little smoother now that the piston rod has real support. Also, testing on higher pressure air has allowed me to test "notching up", and it seems to work quite well. I think I'll keep the current printed bottom end parts until they break, so I'm focusing on making it steam worthy. I'll order all the viton o rings and x rings I could possibly try this week. The o rings that are currently on it are buna from a harbor freight pack.

I may have to adjust the design of the piston valve a little if I end up using o rings. Since the o ring seal doesn't begin exactly at the start of the o ring slot, the valve width is functionally smaller than it's supposed to be. This wouldn't be a problem with an x ring though, so I'll try that first. Otherwise, I may have to move the o ring slots outward. Once I get it running well on steam I'll be sure to post the cad model on grabcad for anyone else to take a look at.
9.jpg
I'm working on the exhaust routing now. I machined these header flanges out of steel so that I can solder a half inch copper pipe into them. My CNC eats aluminum for breakfast, but likes to leave a lot of burrs on steel. I didn't have any brass of the right size laying around, so I used steel since I needed something solderable.

I'm also working on gaskets. Ideally I'd have some local person who has a laser cutter cut them out, but I think I might make some 3d printed stencils to cut them out by hand instead. Or maybe I'll get an ink pad and do it the keith appleton way. I read that soda can box cardboard makes good steam engine gaskets?
Last edited by rmac on Wed May 04, 2022 10:23 am, edited 1 time in total.
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NP317
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Re: First serious steam engine build.

Post by NP317 »

Regular brown paper shopping bags also make good gaskets, especially if oiled during assembly.
Those on my Allen Ten Wheeler have worked perfectly for 15 years of steaming, and come apart easily because of the oil impregnation.
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Glenn Brooks
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Re: First serious steam engine build.

Post by Glenn Brooks »

Wait. what? You built this in 7 days?? Iam into my locomotive rebuild 7 years and haven’t even started yet. Please move in next to me. Sounds like you need something to do each week, in between your builds.

Phenomenal work BTW! :!:

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Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

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zimirken
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Re: First serious steam engine build.

Post by zimirken »

It's actually been about four weeks. I had a couple slow weeks at work, so I was able to load and start the CNC, and then go about my tasks while it was running. The machined parts have taken around 20 hours of machining time across about 40 setups. I only had to redo a couple of parts. Plus, besides the cylinder and valve chest, the majority of the parts aren't much more complicated than a piece of aluminum plate with some holes in it. The design is very much optimized for ease of manufacture, especially with a CNC. In fact, I didn't actually make anything on a lathe. Even the piston valve was made on the CNC with some clever use of a slitting saw and a chamfer tool. The cylinder and valve bores were done by spiraling a large carbide insert end mill, and the precision and finish ended up good enough to use as-is with o rings. I also get to skip a lot of finishing operations due to the precision of the CNC. I use stubby high precision drill bits that don't need spot drilling and make perfectly sized holes that don't usually need reaming. It can also make round pockets with 0.01mm precision using regular end mills moving in a spiral motion. I also have a fourth axis that can hold small pieces, that allows me to make parts like the piston rod clevis without having to re fixture to drill holes on a different side of the part.

I count myself very lucky that I have access to a CNC like this. I work at a factory, so it's not a production machine, it's mostly just used to make random tooling for the lines and RnD. It sits idle most of the time, and I'm really the only one here who knows how to use it.
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Bill Shields
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Re: First serious steam engine build.

Post by Bill Shields »

If you have good surfaces then a dab of RTV may well be all you need for sealant.
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Re: First serious steam engine build.

Post by zimirken »

I finally placed my o ring order from https://www.oringsandmore.com/ . I ordered viton o rings of both normal and 90 durometer hardness, viton x rings, and silicone o rings, in all the sizes I need. It was only $25 to meet the free shipping minimum, and I'll have quantities enough for the rest of my life thanks to the minimums for each. I've heard that silicone o rings don't like sliding very much, but Keith Appleton uses them for gland packings, so I figured I'd spend the two dollars to get some of those too. The o ring website says that EPDM rings are actually recommended for steam service, but I've never heard of anyone using them, so I didn't bother getting any.

I'll start with x rings on the piston valve, so that I can get more precise valve timing. I think that there's a couple positions in the stroke where steam may be able to leak around the edge of one o ring, into the cylinder passage, and around the other one, going straight from intake to exhaust. Plus, the piston valve moves much slower than the piston, so x rings should do better there anyways.
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Bill Shields
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Re: First serious steam engine build.

Post by Bill Shields »

You do not want silicon on sliding service on the pistons.

Packing.....maybe .if they work who is to argue?

Your obsession with the shape of the rings allowing for more precise timing is unwarranted.

However if there is a valve position where what you describe can occur.. well then maybe the design is not the best. Relying on the edge of an elastomer seal to prevent such from happening is fraught with impending problems.
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zimirken
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Re: First serious steam engine build.

Post by zimirken »

I'm getting closer to it being ready for steam testing. I got some copper pipe and soldered it into the exhaust headers. It's just regular silver bearing plumbers solder, since it's for the exhaust. Then I milled the passages out of the pipe.
20220506_140815.jpg
After cleaning it up and reinstalling everything. Anyone have any tips on the best way to remove the extra solder?
20220506_141858.jpg
Giving it another try on air it's quieter and sounds more like a steam engine! Also further testing on air shows that on 40-50psi I can move the reverser lever almost to the middle and it will idle along. This shows that my valve timing matches the simulation (dockstrader) very well. It also runs just as well backwards as it does forwards, although I feel like it runs a little bit better backwards when notched up. With the o rings arriving on monday, I'm very close to a steam test.

The o ring timing issue is due to the fact that the o ring seal begins close to the center of the slot on the piston valve. Since my valve is timed based on the edges of the o ring grooves, that means it's functionally shorter than it's supposed to be. I'll try the x rings first, as they seal right up near the edge of the ring groove. If they wear out quickly, I'll make a new valve and place the center of the o ring grooves where the edges of the valve should be.
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Bill Shields
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Re: First serious steam engine build.

Post by Bill Shields »

hmmm..

you are assuming that an O-ring under pressure is the same shape and position as a static O-Ring at STP -> which may or may not be a valid assumption.

and that both are different than the X-Ring -> which again may not be a valid assumption.

symmetrical running is a very good sign...and most every steamer runs slightly better in one direction than the other...the better the build, the better the symmetry.

what are you using for lubricant in the air / steam ? Especially since all appears to be aluminum....

food for thought regarding your copper header mounted to a non-copper cylinder..

differential growth due to material / temperature differences will eventually cause something to fail...be it a bolt or gasket or .....???

it probably won't make much (if any) difference in what you are doing -> but as a design practice -> there is room for future improvement.
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Re: First serious steam engine build.

Post by Harold_V »

zimirken wrote: Fri May 06, 2022 1:59 pm Anyone have any tips on the best way to remove the extra solder?
It's easy enough to remove with a three cornered scraper. Once carved away, blend the scraped surface with some fine abrasive cloth. The use of a file can be helpful as well.

H
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