Marine Twin Cylinder Build (Steamech)

[Kim]

Hi Everyone,

After completing my first engine, the GEARS 2011 aluminum casting kit (I posted some pics of the finished engine here http://www.modelenginemaker.com/index.php/topic,1550.0.html) I wanted a bit more of a challenge.  Something that had more parts and maybe two cylinders.  I've been building model ships for a while, and a marine engine seemed in keeping with that, so I looked around for available plans (I don't think I'm quite ready to do something completely from scratch yet. We'll leave that challenge for a future build. )

In my search I came across the SteaMECH site. He had a nice looking  2 cylinder marine engine with reverse!  That seemed cool.  So I ordered a set of his plans for $8.00.  They arrived in PDF format in less than 24 hours.  The plans are very nice and fairly complete, consisting of 17 sheets of nicely done, clearly labeled drawings.  I've found a few mistakes.  And though I don't have a ton of experience here, I feel that they are very good value.  I'm pleased at least.

Here's a picture of the engine and the plans from the Steamech web site: http://www.steamech.com/marine-engine-model.htm


My first task on this build was to spend several weeks converting the drawings from metric to English measurements.  I did mostly a straight conversion, but a few things I changed to dimensions that would be more readily available for me (e.g. rather than using 3mm thick stock, I changed it to 1/8", etc.)  Several of the diametrical dimensions were already in English units, like the cylinder bore (1/2") and the crank shaft (3/16"), so that simplified things for me.  Going through this exercise helped me get thoroughly familiar with the plans.

Also, the plans came with no BOM, so developed one for myself.

With that done, I ordered some bar stock I was missing, a couple of reamers I would need, and some fasteners (I also converted those to US stranded sizes).

The engine felt very small to me.  It's only 2" wide, by 4" long, and about the same height.  I realize its not small by many people's standards, but for me, it feels like a challenge.  During the conversion process, I even considered doubling the dimensions of everything. But in the end I decided against it.  Keeping it small will make it use less metal, fit on my smaller equipment better (Taig lathe & mill) and take up less space when done   But I was worried that some of the parts would be so small and thin that they'd be beyond my abilities.  So, I started there first, making one of the smaller parts of the engine - the reverse links.  Of course, I happened to have the stock on hand to make those too, which helped me choose to start there.

Next post - the Links.

I'd also like to take a moment at the beginning of my build to say that I love to learn.  And I like the challenge of working on things just beyond my abilities.  I also like to get pointers and constructive criticism from others.  I find I learn more that way and enjoy the process more too!  So please, feel free to comment - tell me where I could have done something smarter, or better.  I'm not necessarily committing to doing it that way, but I am committing to learn, and I'll certainly have another tool in my tool belt for the next time!

Thank you in advance for any advice, pointers, tips, criticisms or comments of any kind.  I welcome them all!

Kim

[Jo]

I'd also like to take a moment at the beginning of my build to say that I love to learn.  And I like the challenge of working on things just beyond my abilities.  I also like to get pointers and constructive criticism from others.  I find I learn more that way and enjoy the process more too! 

  I also like the challenge of something that is just beyond my abilities. But my expectations of what I think I can do and what comes to pass is never the same. 

She is a nice little engine, looking forward to seeing your progress.

Jo

[Robert Hornby]

Hi Kim, your engine looks extremely similar to the one I started recently though mine is marginally larger at 15mm bore and 1/4" crank shaft. Good luck with it and I will be following your progress closely.
Robert

[Bogstandard]

Kim,

I was one of the lucky ones who managed to get hold of one of the laser cut sets before he started to rip people off, it is still sitting on a shelf waiting to be built.



At the size shown on the plan, the engine would be perfect for a steam model up to about 48" long, if it was a fairly streamlined one, like a Windermere launch, and coupled to one of Sandy's boilers.

http://www.modelenginemaker.com/index.php/topic,1317.msg17602.html#msg17602

http://www.modelenginemaker.com/index.php/topic,1318.msg17605.html#msg17605

There is a critical dimension missing from the drawing, and despite a fellow member going round to see the gent personally, we never managed to get it, so it is a matter of suck it and see if it works with a guesstimation. That is the centre height to the main bearings.

John

[zeeprogrammer]

Looks like a fun project Kim and I'll be watching.
Don't worry much about small parts.
There's lots of info around here to help with making small parts.
I had less trouble with holding them but more trouble with order of operations.
My favorite boo-boo is crushing drilled holes in the part when I clamp them in the vise.

[b.lindsey]

Hi  Kim.  At 2" x 4" that is a small thing, but should be perfect for your Taig equipment. I'll be following along with interest also !!!

Bill

[Kim]

Thanks for the comments Jo, Robert, John, Carl, and Bill,

John, I saw that he was selling laser cut sets at some point, but I wasn't really interested even if he'd had them in stock since I want to make all the parts myself.  And I hope I'm not touting someone who's been ripping people off!  I've been pleased so far with the plans and the transaction.  Making plans is hard, and missing a measurement is understandable.  But not responding to honest questions is not.  That's kinda low in my book

I did notice a few missing dimensions, and I believe that I can figure out what to do in those cases.  Guess we'll find out, eh?  And then when I make a muck of it all, I can come crying to you good people to help me resolve my mess 

As for steam... I'm currently planning to use compressed air only.  Real steam scares me a bit and I don't have the urge to tackle that...  yet...  Who knows what I'll do in the future!

Thanks everyone for looking in on my nascent build!
Kim

[Kim]

Just to see if I could make these small parts, I started with the links. These are part of the reversing mechanism.  They are about 1”x1/4”, and 0.047” thick (I chose to stay with the 1.2mm dimension here because I worried that 1/32” would be too thin to have the required strength, and 1/16” would be too thick and cause clearance problems somewhere else – there’s a lot going on around those linkages!)

I was unable to find 1/16” mild steel, so I just went with some 1/8” bar stock I had.  I started by milling it down to the 0.047” thickness.


Then I used a slitting saw to cut the 1” wide piece to the appropriate width.  This way I got 3 pieces out of the single chunk.  Since I needed 4 of these links, I did this all twice anyway, ending up with 6 parts for me to choose the 4 best from.


Following this, I brought them all to the correct width, then length.  I milled all 6 pieces individually to get the width.  But when I went to trim the length, I had these long skinny pieces sticking up out of my little vise.  So I ganged them all together, sandwiched them between some parallels, and used some other parallels to square it all up while I tightened things down.  This image shows the setup I used to mill to length.  This may have been a dangerous operation; I would love to hear people’s thoughts on doing it this way. But it worked OK for me.  The widths were all the same, I’d just assured that, so they all seemed to hold tightly.  And I made light passes to even them up and get them to the correct length.


Next, I drilled the appropriate holes in each end of the links.  They are symmetrical, so I setup a stop on one end of my vise, and used that to get the same spacing, then proceeded to spot center and drill each end of the link.


Here’s what I had at this point; six identical parts with end holes.  All that was left was to round the ends and mill out the center.


So, next step was to round off the ends.  To do this I tried using my dividing head (home made), but it has too much movement unless you lock the spindle down.  So I made a jig with a steel pin that fit the end holes, and used my disk sander to round off the ends.  I didn’t take a picture of this (silly me).

I was having a hard time milling this steel.  It wasn’t the mild steel I thought it was.  I think it was some kind of hot rolled steel.  I got it from the local hardware store, and they don’t really seem to know or care what kind of steel they have.  It’s steel. Its hard. Use it.    I’d chipped a couple of 3/8” HSS mill bits working with this stuff already.  I did find that using a lower spindle speed (~5000 RPM) and taking really thin passes helped, but still… I was worried about milling this hard stuff with a 1/8” bit.  So I opted to drill out a series of holes, then just mill through to connect them.  This seemed to work, and I didn’t damage my 1/8” end mill. 


Here’s a shot right after I milled the holes together.


Here’s the final product:


The drawings show the middle cut out making arcs on the ends to match the holes.  I chose not to do that because of the small radius (and small mill bit that would be required) and because my dividing head wouldn’t really support that. I have since gotten a Rotary Table which would make this possible.  And I may do it yet…


My assessment, based on my first part for this engine, is that, while a challenge, the size isn’t TOO small.  Unfortunately, I’m not very happy with these links.  I don’t like how the ends are rounded.  They aren’t very uniform and have more of a taper on one side.  I believe my setup for drilling the original end holes was off by a few thou on getting the holes centered, which messed up the rounding of the ends.

I’m withholding a final decision.  These parts are likely functional, but may not ever see the final engine.  I’ll decided how I feel as I get toward the end of the project.  I may be ready to use them just to get done when I get there!  Who knows!

But at this point, I’m committed to the build at this size. And I’m excited.

Next step will be the cylindars.  Another part that I see some challenges in…

Thanks for looking, and please feel free to offer comments and suggestions!
Kim

[Jo]

Kim, Good job these little parts can be a pain  .

For information I showed an alternative way to make small spindly links on my governor thread  : http://www.modelenginemaker.com/index.php/topic,838.msg10061.html#msg10061

Jo

[b.lindsey]

Those don't look bad Kim...but yes that hardware store "steel" can be a pain. Just take your time, even if that means waiting for Big Brown to bring you the correct material when needed or finding a local source with a greater variety of materials.

Bill

[vcutajar]

A good start Kim.  I wouldn't throw away those parts as yet.

Keep it up.

Vince

[Robert Hornby]

Kim, Regarding rounding the ends of the links I make two discs about 3 or 4 mm thick of the same diameter of the link with a hole the same dia of the hole in the link. Fix the three together like a sandwich with a bolt, but not tight as the discs need to rotate easily. Then just file the link ends round to a perfect radius, the file will roll over the links. Easy peasy

Robert

[Mike OConnor]

Hello Kim,

You were spot-on with your decision to gang and stack the thin material as you did. However, it may have been easier to orient them horizontally and place them on a parallel, than to do it vertically as you did. I think it would be tough to make sure all of your parts were aligned in that orientation, which could result in a squareness error. A vise stop is a great aid to bring the second side to dimension and to drill holes in multiple parts. Also, an end mill (4 flutes) would give you a better finish than a slot drill (2 flute) on the end of your links (length).

Robert Hornby gave you some good advice to finish the radii on your small parts. Theses are also known as filing buttons and can be easily made from drill rod or silver steel and hardened with a propane torch. If you clip the corners at 45 degrees with a belt sander or even a file at this small size, you can use the filing buttons to finish the radii in short order.

The complex profile of the internal slot was meant for the CNC laser-cut parts. You are doing a great job documenting your build. Thanks for taking the time to post it.

Kind regards,
Mike

[steamer]

Nice build Kim!

Dave

[zeeprogrammer]

Good start Kim. Good post too.

Filing buttons...I used them in my last project and was very surprised at how well things turned out.