# 2 cylinder inside-out steam engine



## cfellows (Nov 2, 2011)

I ran across this video on youtube and was impressed with the way it runs and sounds. Also liked all the movement so thought I'd take a whack at making something similar.

[ame=http://www.youtube.com/watch?v=P4UrQFhxf7A]http://www.youtube.com/watch?v=P4UrQFhxf7A[/ame]

This is a drawing of what I have so far. Not complete, but gives you a good idea of what I'm aiming for.







So far I've got the flywheel turned and the 2 cylinders made. The latter are made from aluminum tubing, 1 1/16" OD x 15/16" ID. The flywheel is from Martin Models and is 5.5" diameter.






Chuck


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## Path (Nov 4, 2011)

Chuck ...

This going to be a fun project to follow. 
In fact, I would like to make one. Anything I can do to help?

Pat


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## cfellows (Nov 4, 2011)

Thanks, Pat, think I got everything under control for the moment.

The original engine shown in the video uses rotary valves in the crankshaft. In my engine, the valving will be operated by the cylinder. As it moves from one end to the other, it will push the piston and the hollow piston support shaft left and right to alternately connect one end and the other with the air supply coming up through the end supports. Although not shown, I will have to install stops on each end to limit the axial travel of the piston support shaft.

Here is a picture showing my current plan for the air supply and valve operation. I have some concerns about my ability to get the piston support shafts to move freely left and right and still seal well in the end supports. Have to see how that goes. My engine will be reversible, and, although it should be self starting, I'm guessing it will always start in the same direction it was last going. 






Chuck


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## lathe nut (Nov 5, 2011)

Chuck that is neat, depend on you to find something like that, explain it so easy then draw it, that is so good of you to share your knowledge and great skills, here I go again another copy and paste for a future project, thought that I could get you and Brains projects done in a few hundred years now looks like its going to take several thousand, will follow this one, thanks, Lathe Nut


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## Captain Jerry (Nov 5, 2011)

That is a really interesting design and your innovation of moving the valve rod by piston contact adds to the interest. It also adds to the number of problems to overcome, but that's the whole purpose of this activity (I hate to use the word "hobby"). This project will keep you thinking and will keep the rest of us entertained. I had been trying to figure out the purpose of the o-rings in your first drawing. Did not see this coming.

I know how much you like the exhaust puff of poppet valves and this design should lead to a really sharp PUFF!

Jerry


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## cfellows (Nov 5, 2011)

lathe nut  said:
			
		

> Chuck that is neat, depend on you to find something like that, explain it so easy then draw it, that is so good of you to share your knowledge and great skills, here I go again another copy and paste for a future project, thought that I could get you and Brains projects done in a few hundred years now looks like its going to take several thousand, will follow this one, thanks, Lathe Nut



Thanks, Lathe Nut. I'm always looking for ways to simplify things, so projects can get done quicker!  



			
				Captain Jerry  said:
			
		

> That is a really interesting design and your innovation of moving the valve rod by piston contact adds to the interest. It also adds to the number of problems to overcome, but that's the whole purpose of this activity (I hate to use the word "hobby"). This project will keep you thinking and will keep the rest of us entertained. I had been trying to figure out the purpose of the o-rings in your first drawing. Did not see this coming.
> 
> I know how much you like the exhaust puff of poppet valves and this design should lead to a really sharp PUFF!
> 
> Jerry



Thanks, Jerry. The purpose of the large o-rings is just to cushion the cylinder contacting the piston and sound of metal on metal.

Chuck


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## BillTodd (Nov 7, 2011)

> The purpose of the large o-rings is just to cushion the cylinder contacting the piston and sound of metal on metal.


Chuck,

Have you considered closing off the exhaust hole inside the cylinder (i.e. moving the exhaust hole further away from the piston so it's partially covered by the cylinder gland) to provide an air cushion instead_of/as_well_as the o-ring?

Bill


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## Florian (Nov 7, 2011)

Hey Chuck

You may also find that one interesting: 
[ame]http://www.youtube.com/watch?v=ZexzL-WrqqU[/ame]

Cheers Florian


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## cfellows (Nov 15, 2011)

BillTodd  said:
			
		

> Chuck,
> 
> Have you considered closing off the exhaust hole inside the cylinder (i.e. moving the exhaust hole further away from the piston so it's partially covered by the cylinder gland) to provide an air cushion instead_of/as_well_as the o-ring?
> 
> Bill



That is a possibility worthy of consideration. 

Thx...
Chuck





			
				Florian  said:
			
		

> Hey Chuck
> 
> You may also find that one interesting:
> http://www.youtube.com/watch?v=ZexzL-WrqqU
> ...



That's a pretty engine. Uses a more complex valving operation, tho.

Chuck


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## cfellows (Nov 15, 2011)

I got some more work done on my engine yesterday and today. I've been working on the design as well as some house projects, so haven't spent much time in the shop lately. Hopefully I can start getting really serious about this engine.

Here is the engine base. It's a piece of aluminum about 8" long, 2.25" wide, and used to be about 3/8" thick. However, it had a bit of a bow in it, so I flattened both sides with a flycutter in my end mill. It's now about .335" thick, but it is nice and flat. I will probably cut down the length some.






Here are the cylinder assembly support blocks. I gang drilled the holes to make sure they were in as perfect alignment as I could get them. They are 2" wide, 1.375" tall, and 3/4" thick.






Here is a partial assembly of what I have so far. The cylinder support rods are 3/8" diameter. Probably could have gotten by with smaller rods, but didn't want to push it. I'm quite happy with the alignment and the fit of the cylinder support rods... nice, close sliding fit. We'll see if that's still the situation after I screw the end blocks to the base plate... :-\






Next, I will fasten the cylinder support blocks to the base plate. Once I get all the air passages and mounting holes drilled in the end blocks, I may mill them down some so they don't look so "blocky".

Chuck


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## smfr (Nov 15, 2011)

That video in your first post shows a really interesting collection of engines as it zooms in at the start!

This looks like a challenging, but very neat project. I'll be following along!


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## cfellows (Nov 15, 2011)

I did a bit of head scratching today, trying to figure out how lash up the base plate and two cylinder support blocks so I could drill and tap the holes to hold them together. In the end, I mixed up a little bit of 5 minute epoxy and spread a very thin layer on the bottom of each cylinder support block. I placed the two cylinder support rods in the end blocks then carefully positioned the assembly on the base plate getting everything squared up, aligned and the right positioning. Then I just let the epoxy harden. After about an hour, the epoxy was nice and firm and the cylinder support rods still slid freely back and forth in the support blocks. So far, so good. I had already laid out and drilled the holes in the base plate, so now, I flipped the assembly over and drilled the pilot holes into the support blocks. After enlarging the holes in the base plate, I tapped all 4 holes 6-32 7/8" deep. I put in the cap screws, snugged them down then tested the fit of the cylinder support rods again. Everything still slides freely.






I'm a little concerned that if I take the screws out, break the epoxy bond and scrape off the epoxy, it might throw off the alignment enough to make the rods bind, but, as long as I don't have to, I won't take it apart.

Chuck


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## cfellows (Nov 16, 2011)

Today I completed work on the cylinder support rods. The first task was to cut the grooves in the end of each rod. The grooves allow passage of the air regardless of how the rod rotates. I used a 1/8" cutoff tool and cut the grooves .050" deep. I realized later that they really only needed to be about .030" deep but, what's done is done.






Next, I drilled the center holes, 1/8" diameter and 2.875" deep from each end. I was a little nervous about drilling that small a hole that deep, but it was uneventful. I backed the bit out about every 1/16" to clear the chips. I used a standard length bit to drill as far as I could, but had to use a longer bit to drill the last 1/2" or so. Yup, that's a 12" long x 1/8" drill bit I'm using there. I bought it at Home Depot and I did have to sharpen it before I could use it! Guess I'll have to break down and buy a set of extra long aircraft bits one of these days. 






Here's a picture of both rods with all 4 center holes drilled.






Finally, I drilled the radial port holes in both ends and one on either side of the piston in the middle.






Before the engine is completed, I'll have to plug the ends of the center holes, probably with something resembling a rivet. I'm planning to just use Loctite.

Chuck


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## cfellows (Dec 4, 2011)

After lots of noodling, Thanksgiving, and seemingly endless honey-do items, I got back out in the shop today and made some chips. In fairness to SWMBO, I was kind of stuck on a couple of design issues so probably wouldn't have made much progress anyway!  :-\

I decided to change the cylinder material from the thin walled aluminum to thicker walled brass. I was originally going to put screws through the side of the cylinder into the heads, but decided the convention method of screwing through the head into the end of the cylinder made more sense. So, I turned the brass cylinders from 1.125" brass rod. The heads are also turned from 1.125" brass rod. I will probably do some further shaping to the cylinder and perhaps the head at a later time. 

I also made an aluminum crosshead guide that will fasten flat to the base. The crosshead will be comprised of either blocks or round rollers attached to the cylinder that fit into the slots in the guide.

Here are some pictures of the parts and partially assembled.
















Chuck


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## cfellows (Dec 15, 2011)

Work has been slow on this engine, mostly because I've been working on design issues. I'm trying to come up with an engine that will look good with nice proportions and not look like a bunch of parts just bolted together. Consequently, it has been kind of tough.

I did build and fit the pistons, added the cross head bearings and the connecting rod bosses to the cylinders, and made a steel base to hold both the cylinder assembly and the flywheel assembly. I plan to weld milled angle iron around the steel bed-plate to form the base. The other hurdle before me is to design the flywheel support and bearing assemblies.











I'm also playing around with different flywheel designs. 

Chuck


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## Harold Lee (Dec 15, 2011)

Looking real good Chuck!! Interesting that your base had a bow to it. I was looking through Rudy Kohoupt's plans on the Pioneer engine and he said that all extruded aluminum will have stress warpage and should be milled on both sides to relieve the stress. otherwise it will warp during machining. Was this something that you discovered on your own from experience?

Moving forward I will buy aluminum plate one thickness larger and mill it down like you did.

Watching your build with interest.

Harold


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## cfellows (Dec 16, 2011)

Thanks for the comments, Harold. I really only noticed the bow on this piece because I knew it would have to be completely flat. The way this engine operates requires all the moving parts to be square and in pretty perfect alignment.

Chuck


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## cfellows (Dec 16, 2011)

Got some more done today. I Finished making and mounting the flywheel support assembly. Here's a few pictures of everything assembled.
















I feel like I'm in the home stretch now. Gotta finish the crank arms, connecting rod, and the external plumbing. 

Chuck


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## gbritnell (Dec 16, 2011)

Nice looking engine Chuck. Great job on the flywheel.
gbritnell


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## Harold Lee (Dec 17, 2011)

I agree with gbritnell on your flywheel. The design of it perfectly matches the engine. I liked the martin model casting one you originally proposed but with the larger mass which was not required on this double acting two cylinder design, this one seems more "Victorian".


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## metalmad (Dec 17, 2011)

looking great Chuck :bow:
Pete


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## cfellows (Dec 17, 2011)

Thanks, guys, for the comments. I originally made that flywheel for another project 4 or 5 years ago that never got completed. I carved it out of a solid piece of brass six inches in diameter and 1" thick. As I recall, the blank cost me $40 at Speedy Metals. Now the same piece is priced at $98!

I'm not generally a big fan of flywheels with 8 spokes, but this one looks pretty good. I agree with you Harld, that the larger mass makes it look more victorian and has better proportions.

Chuck


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## sawyer massey (Dec 17, 2011)

cool that is on fantastic design


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## cfellows (Jan 7, 2012)

After a brief hiatus to work on my mill / drill and add DRO's on the x and y axes, I got back to work on my engine today. I finished up the two connecting rods. Here in the first picture you can see the fixture I made to hold each connecting rod for machining. 







I first milled the edge of one side, then took out the screws, flipped the rod over and did the opposite side. After finishing the edges on both rods, I changed end mills to a 3/16" and milled the groove down the center of each side. Finally, I rounded the outside edge of the small end.

Here are the finished rods...






And an idea of what they will look like on the engine...











The whole process was a good exercise in using DRO's for positioning. Makes for much more precise locating than trying to machine up to scribed lines and marks. 

I think I only need to make and install the crank arms to be able to test the engine. And of course I'll need to make a base for it sooner or later.

Chuck


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## cfellows (Jan 10, 2012)

Well, the good news is that I got the engine together enough to try running it...






The bad news, it doesn't run... at all. Doesn't even look like it's trying. I suspect there is too much binding and too many air leaks. 

Chuck


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## flatbelter (Jan 10, 2012)

Sorry Chuck 

Some times even the pretty ones don't run. 

It it does look pretty stunning, I'm sure you'll get it straitened out real soon.

If making motors was easy, it wouldn't feel like much of an accomplishment.

Best of luck, and congrats on the DRO. (I've got one to hookup some time too that I just never seem to get to)

FB


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## cfellows (Jan 10, 2012)

flatbelter  said:
			
		

> Sorry Chuck
> 
> Some times even the pretty ones don't run.
> 
> ...



Thanks, FB. I think I'm going to convert over to a D-Valve arrangement driven by an eccentric off the crankshaft. That will help me control the are leaks and reduce the binding. 

I had my DRO's in a drawer for close to a year. When I finally tore down my mill/drill a couple of weeks ago to replace the x-axis lead screw nut, I decided it was time to install them. I've used the DRO's a few times now and it really makes things a lot more accurate with less time involved. I would highly recommend them to anyone who hasn't installed them yet.

Chuck


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## napoleonb (Jan 10, 2012)

Not that i am a model engine expert but it looks to me that your design could be improved upon.
When the conrod pushes the cylinder forward the forces are also up/downwards, perhaps it leeds to a slight rotation of the cylinder which in terms can leed to higher friction.
Perhaps if you were to offset the conrods or prevent the rotation of the cylinder, as is the case in the movie on the first page, there is less friction to overcome.

Really love the design of your engine by the way, please fix it!


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## cfellows (Jan 13, 2012)

napoleonb  said:
			
		

> Not that i am a model engine expert but it looks to me that your design could be improved upon.
> When the conrod pushes the cylinder forward the forces are also up/downwards, perhaps it leeds to a slight rotation of the cylinder which in terms can leed to higher friction.
> Perhaps if you were to offset the conrods or prevent the rotation of the cylinder, as is the case in the movie on the first page, there is less friction to overcome.
> 
> Really love the design of your engine by the way, please fix it!



Thanks for the comments. Actually, there are crosshead guides on the bottom of each cylinder comprised of a ball bearing race fixed to the cylinder which rides in a square groove attached to the base. This keeps the cylinders from trying to rotate.

Chuck


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## cfellows (Jan 13, 2012)

Got the engine running! Here's a short video...

[ame=http://www.youtube.com/watch?v=GFW1I0_33XM]http://www.youtube.com/watch?v=GFW1I0_33XM[/ame]

Still got some air leaks to fix but I know where they are and how to fix them. Also gotta build the base.

Chuck


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## Captain Jerry (Jan 13, 2012)

Chuck

Don't give up. That thing will run! If I understand the valving, it ought to oscillate without even needing the crank and flywheel. You said it was leaky, but without a load, even a leaky cylinder should show some reaction if there is any pressure at all. If a cylinder doesn't move, it makes me think that there is no pressure in the cylinder, (both ports closed) or equal pressure on both sides of the piston, (both ports open or really bad piston ring).

If it were me, I would take the con rods off and isolate the cylinders so that air was going to only one. I would reduce the pressure so that leaks are minimized and then manually slide the piston to the limit of its travel to check the valve action. If you don't see any reaction from the cylinder, then I would take the cylinder off and test the valve action by moving the rod manually. This should give you a clue to the problem.

It may not be the most effective valve setup. There are lots of opportunity for leaks but it should run some.

I'm just thinking out loud, you have probably thought of these things.

Good luck,
Jerry


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## Captain Jerry (Jan 13, 2012)

Chuck

While I was typing, you got it running! See, I told you it would. Congratulations. Nice action and nice "outside the box" design.   Thm: :bow:

Jerry


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## cfellows (Jan 14, 2012)

Thanks, Jerry. The problem was massive air leaks in supply side and some binding. I redesigned to the air supply but still have some leaks to fix. I managed to fix the binding so it turns over pretty freely now.

The only way the cylinders would oscillate without the flywheel is if the cylinders had enough mass to move the valve rod with it's momentum at the end of the stroke. The cylinders are brass and pretty thick walled, so they may have enough mass. The whole engine oscillates back and forth pretty good at high rpm's.

Chuck


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## ozzie46 (Jan 14, 2012)

I knew you'd get it Chuck. Good job. Nice looking engine. :bow: :bow:

 Ron


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## bearcar1 (Jan 14, 2012)

Way to go Chuck, BRAVO!! A very unique and interesting engine to say the very least. 


BC1
Jim


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## archer3d (Jan 14, 2012)

WoW that looks great I love the way the motion looks. The noise at the end of the video is a bit dis-concerning.

Wonderful work Chuck Thm:

tom


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## rudydubya (Jan 14, 2012)

Nice, Chuck. And I always learn something by following along with your projects.  :bow:

Regards,
Rudy


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## Captain Jerry (Jan 14, 2012)

??? So now that it is running, is it reversible? How? Seems like it ought to go either way ???

Jerry


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## arnoldb (Jan 15, 2012)

:bow: Nicely done Chuck - it looks great Thm: 
I love the way it sounds like a big steam locomotive pulling a heavy load ;D

Kind regards, Arnold


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## cfellows (Jan 15, 2012)

Captain Jerry  said:
			
		

> ??? So now that it is running, is it reversible? How? Seems like it ought to go either way ???
> 
> Jerry



Yes, it's reversible. If you turn the air off, then turn it back on, the engine will self start in the same direction. If you turn the air off, then manually spin the engine in the opposite direction, it will start up in reverse. In other words, the engine will start up in whatever direction it was last spinning.



			
				arnoldb  said:
			
		

> :bow: Nicely done Chuck - it looks great Thm:
> I love the way it sounds like a big steam locomotive pulling a heavy load ;D
> 
> Kind regards, Arnold



Thanks, Arnold, I think it will sound even better once I get all the air leaks in the supply side fixed.

Chuck


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## Maryak (Jan 15, 2012)

Chuck,

Very, very nice. :bow: :bow:

Best Regards
Bob


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## danstir (Jan 16, 2012)

Great job and a very interesting engine.


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## cfellows (Jan 16, 2012)

Thanks, Bob, danstir...

Sometimes I look at a part I've just made and have a "What the H*LL were you thinking!" moment. :doh:

This is the sliding rod that the piston is fixed to and the cylinder slides on. The two radial holes are the ports which admit the compressed air into the cylinder. The piston is solidly fixed to rod right between the two holes.

I had originally planned to fasten the piston to the rod with a set screw. So, I milled a flat in the rod as a seat for the set screw. Unfortunately, I milled it too wide, connecting the two holes and providing a convenient passage for air to transfer from one side of the piston to the other. 

So, what you see here is what is my final fix to air leaks in the form of a dollop of soft solder which I'll file and sand to the OD of the rod before re-attaching the piston. By the way, I abandoned the idea of set screws in favor of loctite 620 (love that stuff).







I'd like to think I learned a lesson here, but I'll probably wind up doing something else equally as obtuse in the future!!!

Chuck


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## bearcar1 (Jan 16, 2012)

"....equally obtuse...." That's funny Chuck! Rof}

BC1
Jim


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## Teza (Jan 27, 2012)

Hi Chuck
Just now found this build thread, fascinating design and great build reports. Your last post shows you need eyes in the back of your head to see all possible errors, gives a newbie like me heart to see a master can still make simple mistakes 
Love this site and the wealth of knowledge and experience.
Terry


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