Another steam engine shaped object

[DJoksch]

I was given another steam engine shaped object as a birthday gift. Unlike last years project, I think I saw this one on E-Bay. It appears to be an incomplete abandoned attempt at a dual in-line engine. I did a rough rework this morning on the valve cylinder using a black felt pen and my calibrated eyes. It works ‘sort of’. I think I can convert it to an in-line compound engine. l’m sketching out how I think it should look.

 

[DJoksch]

I found a link explaining how to determine the primary and secondary cylinder bore.

https://thermodynamicsheatengines.com/HeatEnginesVol%202%20Chapter%202%20RS.pdf

Lots of wasted space as it sits and it looks clunky. The stroke is currently 1.2” and will be extended to 2.25” to use the entire cylinder length To start. Cylinders should be round. Feel free to criticize.

 

[Jasonb]

With the two connections on the end it looks more like the end cylinder was intended as a pump rather than a tandem engine

 

[DJoksch]

The larger brass fitting is a check valve. The other is just a port to a hole. Could make a simple reed valve. You may be right. It does looks like a pump may have been intended. The rod into the second cylinder has a seal like the working cylinder, but lacks piston rings while the working cylinder piston does. It could be made into a double acting pump since both ends are sealed.

 

[DJoksch]

I just took the second cylinder off the frame and saw that it was ported to be a steam cylinder and later plugged. So it looks like it may have started as a compound engine and then made it into an unfinished air pump and finally abandoned. I‘m thinking about an in-line compound expansion engine.

 

[Steamchick]

I agree that it looks more like a pump configuration. But conversion to a compound should be manageable. The link to the document is excellent! I have read this text before - but from a different book - but it said exactly the same words, so has been re-printed in many books I guess.
Thanks for an interesting post. I hope to read more as the project progresses!
K2

 

[DJoksch]

I made a 2.25” throw crankshaft. Now the entire cylinder is used. Given a 2.25” stroke and a 1.2” ID secondary cylinder I can determine the high pressure cylinder diameter. I have a nice 5” flywheel, but I think I need a little more mass.

 

[DJoksch]

Slowly progressing on the tandem resurrection project. I’m using the last resurrection project as a guide. My plane is to get it to run, then see what happens from there. The rule is to use only materials from the shop floor.

 

[DJoksch]

The valve eccentric was poorly made out of thin aluminum. I will remake it in bronze then cut the steam ports and make the slide valves. The flywheel is not very nice and is only temporary.

 

[Steamchick]

I would not worry about the flywheel at this stage, as "original" 19th C engines had pretty crudely cast flywheels, so yours is more authentic. (If you cast a 2 ton flywheel in the shop, you accept it "warts 'n all" as it costs too much to scrap and make another!). You can utilise "natural" imperfections that make the flywheel imbalanced, to partly balance the engine. I always do, and have very smooth running engines as a result. (As long as the valve is correctly set = balanced!).
Cheers!
K2

 

[DJoksch]

This is turning out to be a smooth easy running beast.

 

[Steamchick]

Testimony to the quality of your workmanship.
Well done Doug!
(But I look forward to it running on air, then steam, then converted to a compound?)
Cheers!
K2

 

[DJoksch]

I replaced the thin aluminum eccentric and used bronze clock bushings in the linkage. I waited to mark off the steam ports so I could compensate for any incremental error.

 

[Steamchick]

Hi Doug. I'll be interested to know how you set the valve port sizes and slide valve dimensions. As you'll be aware, lap on valves is quite a critical bit of the design of the engine. I am making a steam pump and the valve timing is adjustable, to compensate for (MY) inaccuracies of machining. But you don't appear to have any adjustment if a port or valve slide is a few thou "off"? I don't want to suggest your machining is as bad as mine, but I have only built engines with some adjustment in the valve train, to tune to balance (centre) the valve when I get to the running stage. That way I do get very smooth and slow running engines, without an odd "kick" or stall at the end of one stroke...
Also, what material are you using in the glands? I always used graphited string, and have put 1 or 2 turns of PTFE tape on the shaft first, but my latest uses silicon O-rings... which I am sure will seal, but hope they will slide smoothly, and not bind. I may be tempted to apply a layer of PTFE tape to reduce friction for when I tighten the glands "just enough" to stop steam leaks.
It looks really good anyway! - Looking forward to seeing it run and make some power!
K2

 

[DJoksch]

My first steam build was a Clarkson 1” bore vertical engine with missing pages that happened to be the slide valve and steam port dimensions. I found some sites that walked through slide valve design. I also read an article discussing lap allowance for steam expansion. Here is one of the sites I used as a reference in my reading list.

Slide Valve Design

The “steam shaped object”, was my second engine and slide valve calculation. In this case an original aluminum lever with a slot allowed for minor throw adjustment. I made a final piece out of brass with no adjustment. For the tandem engine l set the length, but I used aluminum so I can make it adjustable if I need. The slide valves have 0.6” of travel with a slide valve length of 0.825” running .125 x .3“ steam ports. The exhaust port will be .25 x .3”. I’m reworking the math this morning before I cut. I found an old spool of graphite yarn when cleaning my parents shop. I’ve been using this for packing material. For this engine I used the packing nuts that came with it, but I did have to modify them to actually work.

 

[Steamchick]

Thanks Doug.

 

[DJoksch]

I am always amazed at the complexity of steam engine and boiler design. They look so simplistic after they are built. The criticism of my work has lead to very satisfying results. On another topic. Since I’m not using rivets on the Yarrow project, I am deciding on silver solder. The 65% silver from Rio Grand Jewelry looks like a candidat. Has a 1250 deg. Melting point.

 

[Larry G.]

I would not worry about the flywheel at this stage, as "original" 19th C engines had pretty crudely cast flywheels, so yours is more authentic. (If you cast a 2 ton flywheel in the shop, you accept it "warts 'n all" as it costs too much to scrap and make another!). You can utilise "natural" imperfections that make the flywheel imbalanced, to partly balance the engine. I always do, and have very smooth running engines as a result. (As long as the valve is correctly set = balanced!).
Cheers!
K2

Thank you for your detailed and informative comments on this and many related posts.
Can you provide some insight into the theory and practice of steam engine balance?
Particularly for simple, single cylinder, single or double acting models.

Thanks,
Larry in NJ

 

[Steamchick]

Hi Larry,
I use a text book on locomotive design from (I think?) The 1930s... I'll dig it out for the title, author, etc.
On my little models, parts weighed in grams, calculations become a bit meaningless, but I use a bit of trial and error with plasticine and lead shot (from when I used to fish). Or I have some (scrap) weights from car wheel balancing, so have some 10gm steps. Sometimes one of those strapped on a flywheel gives me a useful balance value, to incorporate into the model.
Catch you later, K2

 

[Steamchick]

Hi Larry, there is a comprehensive thread on the subject of Balancing Engines by Jorgensen Steam, in the HMEM Break Room, from 2011, elsewhere on this site, so look that one up and see if it covers your query?
I'll try and help properly tomorrow.
K2