Newbie questions on a plan that I don't understand

[Larry]

I'm an aging woodworker who's looking for a new hobby that will let me sit and take the weight off my knees. Model machining looks attractive, but I've not yet invested in a lathe.

I found an interesting plan for a "Model Marine Engine Requires no Casting" at:

http://www.john-tom.com/MyPlans/Steam Engines/MarineEngine.pdf

Unfortunately, the drawings are not complete. The block shows exhaust ports drilled directly into the cylinder, but there is no end view to show where those ports are located vertically. That would seem an easy solution in a single-acting engine, where the exhaust would be at the end of the stroke, but this engine is double acting. So the only location that could work would be half way up the bore.

That would seem to halve the effective stroke -- won't that throw out half of the engine's power?

The piston valve controls the steam inlets, but nothing seems to control the exhaust. Angling the inlet ports towards the center of the valve would seem to allow more room that might allow the valve to control the exhaust also. How could I modify the valve piston to handle the exhaust?

I looked for a plan for another double acting engine with a piston valve that might show how that's done, but I didn't find one. Would any of you know of a plan? Could you recommend an introductory book that explains it?

Have any of you built this engine? If so, what did you think of it?

I'd appreciate any comments that you can offer.

Very respectfully,
Larry

 

[gbritnell]

Hi Larry,
Welcome to the forum. First off that would be quite an ambitious project to start out with. Not having a lathe yet and not knowing what machining experience you have it could be very frustrating to try an engine like this. Along with a lathe it would require at least a drill press and assorted tools, taps, dies, reamers and such.
As for the engine itself it is what they call a uniflow design. The steam enters from the piston valve and pushed the piston down. When it gets almost to the bottom of it's stroke the ports in the side of the cylinder allow the pressure/steam to escape. On a full sized engine of this type there is also additional relief valves so when the piston returns and starts to compress the volume above the piston it is vented off. Baker traction engines and others used a similar system.
The steam is admitted from the 2 ports in the piston valve sleeve with the cylindrical piston valve. The dimensions for the port location in the main cylinder would be taken from the sleeve. (1.00 spacing centered on the cylinder).
gbritell

 

[kvom]

A similar engine with an excellent set of plans and build threads by member Bogstandard might be easier, esp. as the crankshaft is built up rather than 1-piece. Search the site for "paddleducks" engine. There have been several built by members here.

 

[Metal Butcher]

Hi Larry. I have not built this exact model, but I have built uni-flow designs in the past. They are problematic at best in that they require higher pressures to run than slide valve (D-valve) designs. On the up stroke air or steam is trapped above the piston and must be compressed to complete the stroke. On this model the trapped air must be compressed on the up stroke and down stroke.

As far as modifying the plans? I modified the 'Husky', and made the VALVE double acting and the engine runs well. It proved how bad a design like this really is! I would find plans for a standard two cylinder, double acting, slide valve design marine style engine.

I would recommend building Elmer's #44 is a great running engine and well worth building. Below is a link to the one I built.

http://www.homemodelenginemachinist.com/index.php?topic=6552.30

-MB

 

[Tin Falcon]

Larry:
First of all welcome to the forum . A George said this is not particular a first build engine.
I will say there are at least several kits and projects out there that are advertises as a beginner project that are arguably not well suited as a first project.
The Kozo Hiraoka Pensylvania A-3 switcher is a "First project for the beginner " book While the project is nicely sized and the detail is step by step and superbly written , it is a long term project. Yes take one step at a time one bite at a time but there is a lot of chewing to be done.
IMHO a simple short term project where you can see success in days or a few weeks is important to most of us to start with..
The Stuart 10H / 10v kits are touted as beginner engines as is the Pm research 2A. These are great kits but only come with blue prints. Just a set of prints is great or an experienced hand but a new guy or gal needs step by step instructions on set ups and order of operations. You can get instruction books from Stuart and PM sells how to build videos if want these routes.
Start with something simple that has instructions with it. And if you do a bar stock build if you mess up a part little is lost just cut another piece and start over.
reading this thread may help you.
http://www.homemodelenginemachinist.com/index.php?topic=9413.0
Tin

 

[student123]

A similar engine with an excellent set of plans and build threads by member Bogstandard might be easier, esp. as the crankshaft is built up rather than 1-piece. Search the site for "paddleducks" engine. There have been several built by members here.

Larry,

Here's a link to where the paddleducks plans by Bogstandard can be got:
http://www.machinistblog.com/bogstandards-paddleduck-engine-plans/


Mike

 

[lordedmond]

Larry

welcome

If thats all the plan that is very incomplete we lots of info missing as the others have said look at the design by "Bogs "

I am sure you will enjoy the build knowing that

1 it is a proven design
2 errors on the drawings have been corrected ( not that there was any )

3 masses of help from the forum members


BTW I build 5 g loco's and spend £ 120 on the plans and some are full of errors which conspire to cause the tyro much time and frustration , not to mention the cost if its a casting


Stuart

 

[bearcar1]

Hello Larry, and welcome to the finest place on the face of the Earth that will satisfy your curiosity in the world of model engineering. (gees, don't that sound like a carnival come-on? oh well. My last name is Barker after all) Anyway, getting down to the answer to your question, I believe that George has explained that one reasonably well in that the admission and exhaust of steam is being controlled by a spool valve and these engines are what is known as 'Uni-flow' type engines. Now having said that, I'd also like to suggest, like others have, perhaps a 'simpler' model would be a better place to begin and then work up to something like this or "The Paddleducks" engine. These two are very nice models but may be just a bit too advanced for someone that is just starting out in metal working. I'd like to suggest perhaps "The Pug" as a good starting point. http://www.homemodelenginemachinist.com/index.php?action=tpmod;dl=item197 This one I believe will provide just enough of a challenge to the first time builder and at the same time provide a great looking engine that is not the usual 'oscillator' type that is frequently suggested as a starting point. This engine was designed and built by one of the members here and he posted a build thread documenting his progress. You can do a search for it to see how he progressed. These plans are shown in metric dimensions but can be very easily converted to imperial sizes without fear of ruining anything by doing so. Just as in woodworking, sometimes one has to be a bit flexible and creative to make things fit. ;D Also, this engine is built from readily available bar stock and the pieces are of a size that if an unrecoverable error is made, it won't break the bank in terms of money or time invested. Others may suggest different 'starter' engines but to me this one is the "just about right" place to begin. Best of luck and please don't be a stranger.

BC1
Jim

 

[Larry]

Wow.

Thank you all for your comments and suggestions.

I'm taking a class on basic repair of mechanical clocks because I'd like to scratch build a weight driven one. From there I got interested in a lathe . . . . .

I read Hasluck's "Model Engineer's Handbook" last week but could not find his "Lathe work." Thank you for that link.

No. I'd not envisioned that engine as a first project, but it did catch my eye. Because the drawings lack detail, I started a SketchUp model of it to mentally build it, which is when I ran into my question on the exhaust. My concern had been on the loss of effective stroke -- I'd not even thought of the opposing compression.

If I can talk my wife into a lathe (I'm looking at the Taig), I'd planned to make a simple wobbler as my first project to learn hand turning with gravers, so I need to order the steel to make a set of gravers -- I need something to encourage me to practice my language skills. A twin was what I'd considered as a challenging second project that would lead to something like Woodson's double acting single (Popular Science of April 1947) as a 3rd project -- but that will need casting, and I don't know a foundry. (I printed it off but cannot find the link to post.)

Anyway. My sincere THANKS! to you all for your encouragement and your attempts to keep me from walking into the wall.

Very respectfully,
Larry

 

[joe d]

Larry

Welcome. I'll certainly recommend the Taig, I've had lots of fun with mine. The '47 Woodson was my first
project, (see my avatar) I had castings done for it, but one could certainly build up the bits from bar stock.
have a look here to see how it went.

Cheers, Joe

 

[Larry]

Joe,

Thank you for posting that: an engine that got my interest on the lathe that I'm considering buying. The pictures do show that I'd not want to up scale it at all.

Did you consider investment casting it rather than sand casting?

Very respectfully,
Larry

 

[joe d]

Larry

I went with sand casting as that was pretty much all I knew about casting at that time.
(and still do not know much more ;D). I did not ask for anything else when I was at the
foundry, and they didn't offer.

As a point of interest, the plans you linked to in your first post are in fact also
a C W Woodson design, published in Popular Science in January of '53, which seem to have had
a little "trimming" before arriving on the John-Tom site to remove the author and magazine
references...

Whatever you finally select, jump on in, the water's fine!

Joe

 

[Larry]

Joe,

THat's interesting that Woodson drew both plans that caught my eye. That could be because of my near complete lack of exposure, or it could be that his designs simply strike a note in me.

Thanks,
Larry

 

[Larry]

Kvom, thank you for citing to the Paddleduck engine, and, Student123, thank you for the link.

I cannot believe that Bogstandard invested the time and energy to create that document. I found it entertaining and a great introduction into the steps necessary to build a marine engine. And he documented answers to several problems that I was trying to resolve in the Woodson marine engine.

Very respectfully,
Larry

 

[joe d]

Larry

I knew I had this, but couldn't find it the other day when I replied to you...

Some guy who modeled the '53 Woodson in solidworks here

Thought you might find it interesting.

Cheers, Joe

 

[Larry]

Joe,

Thank you for that link! It's interesting to see the engine in 3D.

Larry