Two Cylinder Double Acting Steam Engine Build

[vederstein]

On my first attempt at the crankshaft, I used bits and pieces I had laying around. The truth is, I entirely forgot I purchased material to make the crank. The first one sucked anyway.

I'm amazed by the folks that turn a crankshaft from a single piece of barstock. It looks very difficult and I've always been to intimidated to try it. This engine is no different. I make my cranks from built up pieces.

The round pieces are just pieces of 1/2" roundstock where I turned down a shoulder.

The trickier part is getting the crank webs correct. So I drilled/reamed a single piece of barstock that was destined to become the two webs.



Then I marked the approximate center and saw cut the two parts in half.

From there I could index the hole locations and clean up the ends:

All this is fairly normal, the next step will probably send the "proper modellers" cowering under their bed in fear because what I do is so, so wrong. I weld it!

I pressed the ends together then plug weld the ends.

Then I put the two ends into the lathe to face off the extra weld.

So I have two crank halves. To join them, I clamped the two parts together with the crank throw installed. Then weld it up!

I assembled the engine and worked it in with the lathe. Believe it or not, the crank was about as straight as I ever get. After some fiddling with piston/crosshead alignment, I can turn the engine with my hand on the crankshaft. This was a big milestone.

I has planned on making two castings on this New Years Eve (flywheel & 2nd steam chest), but it's raining and to cast material today would be beyond dangerous stupid. So that's it for 2018...

...Ved.

 

[vederstein]

I have two videos here showing the flywheel casting and machining for this engine. The first, which is the heavily edited version is for most people. You can see the creation from making the sand mold to the final clean up in about 3-1/2 minutes.

The second version is for the masochist. It shows all steps in real time with limited editing. It's over twenty minutes long. At least you can listen to the background and guess my music preferences.

Enjoy (or don't)...

 

[vederstein]

Spent some time today working on getting one of the cylinders running. I wanted to check the design prior to making any more components.

First I realized that my design is a pain in the *** to time. So I removed the eccentric ring and drilled out the opposite end. This allowed me to make timing adjustments without removing the eccentric. I seem to remember that steam engines like their timing with the eccentric 180 degrees out of phase with the crank. On this engine, 90 degrees was what really worked. I spent far too much time re-learning this.



Second, my engine had a lot of drag. After some investigation, my oring seals have swelled. I guess EDPM doesn't like something. I replaced the seals, but I'll probably need to get seals of a different materials.

Third, it was a bit troublesome getting the valve rod length correct. It took several tries, but I got there. Below is a video of the engine running on one cylinder. The first part I had the valve rod too short and you can see the engine reversing. The second part of the video has the engine running. Pressure was about 25 psi. I hope this will improve once the second cylinder is active and the engine is broken in.

...Ved.

 

[vederstein]

With one casting to pour and a snowy day outside, making that particular part was out of the question. So I worked on the engine base. This design was totally based on material I had laying on the floor. After I made it, I documented (created drawings) of what I created.

I found a length of 3/8" thick by 3" long aluminum. Looked good to me. So I cut a four inch long piece and after some squaring and guessing the pilot hole location, I drilled & bored the pilot. I usually don't have much luck with my boring head. This time things went well though.



Then I drilled the hole pattern for mounting the plate to the engine block.



I positioned the plate on the engine and used a transfer punch to locate the holes. Next was to drill/tap the corresponding threads in the block.



There were some "ears" left over on the material, so I scribed the location and then milled off the ears. I also drilled/tapped mounting holes of the plate to the base plate.



The base was made from the same material. Other than a cut out to engage the vertical plate, it was pretty easy.

...Ved.

 

[vederstein]

Another weekend another snowstorm. How the hell can I finish this engine when I can't cast the last component!!!!

<GRRRRRRRR>

 

[vederstein]

Last Friday evening it was very cold, but the weather was dry, so I froze my butt off and cast the last component - the steam chest for the second cylinder.

Today I machined said component and installed on the engine. No need to document, since I already documented the first one. Then it was about six hours of fiddling getting the engine to run at lowish pressures.

If you remember from my previous video, the engine was running on one cylinder at about 25 psi. In the video below, I managed to get it to run at 8psi on both cylinders and will sometimes tick over at 5psi. Good enough for me!!!

As I was setting the timing on the second cylinder, I realized its eccentric was exactly the same position (clocking) on the crank as the first eccentric. The 90 degree cylinder offset takes care of the timing. I'll update my design/drawings to reflect this.

Other things I changed. I changed the piston seals from EDPM to Teflon orings. The EDPM was near wear resistant enough. It was difficult to get the valve train free, and much of my tweaking had to do with this aspect. I started painting the thing. After the fact, I'm not too thrilled with the purple, but I guess I'm stuck with it now.

This engine is destined to power a spin art machine of my own design for the 2019 Maker Faire season.. Though the spin art machine is only about 40% complete, I was able to test the engine on the spindle. It works just fine.

Now for the video:



Bye,

...Ved.

 

[davidyat]

Since this is of your own design, can I buy a set of plans from you?
Grasshopper

 

[vederstein]

Since this is of your own design, can I buy a set of plans from you?
Grasshopper

Once I'm completely done with the engine, I'll post the plans on this website, no charge. This is hobby and I'm flattered if someone else uses my designs.. As I've made the engine, I've caught some print and design errors. Therefore I don't want to pass those errors on to the next person. I intend on posting PDF drawings and the solid models (step format) of the engine and the casting patterns.

This engine can be built entirely of barstock if you choose (and it would probably look better), but if you want the castings instead, we can discuss and come to common terms. I won't gouge on price, but it will expect to be re-imbursed for my material and labor. I'll probably take orders for one casting run only. Also, I do the castings in my driveway and honestly they're not great quality. I tend to have lots of casting flash.

Wait a couple of weeks and I should be completely finished with the engine and I'll post the drawings.

...Ved.

 

[johnmcc69]

Really nice build Ved! Nice of you to share your plans & castings here.

John

 

[davidyat]

Looking forward to getting my hands on this build design and plans. I like to do things from bar stock.
Thanks,
Grasshopper

 

[vederstein]

I've gone ahead and posted the design in the Plans forum

https://www.homemodelenginemachinis...double-acting-steam-engine.30980/#post-319664

 

[vederstein]

I just couldn't get over the paint coverage of the purple modeling spray paint I used on the engine. I found an alternative paint that I used on my last engine project. The color is blue, but this paint is much thicker and works quite well when it comes to filling in the nooks and crannies of the casting finish. You can still tell it's a casting, but the sand cast bumps are much smoothed out. This paint also adheres to the aluminum barstock components, so they can be painted as well if desired.



I disassembled the engine for painting this time. It's a risky prospect. It took so long to get the engine running to my satisfaction that I was hesitant to do it over again. But so be it...

After reassembling and getting it running ok again, I touched up a few places. I intentionally left the block raw aluminum.

I did realize that I need to re-make the right hand steam chest. It simply leaks too much through the valve rod gland. I used a 0.189 reamer, I guess I should have used a 0.1875 or even a 0.0187 and lapped the valve rod to the housing. The left side housing is much better than the right. I just can't let the leakage go.

The leakage isn't a big deal on compressed air, but when I run this engine on live steam, it will create one hell of a mess.

To be continued...

...Ved.

 

[johnmcc69]

Nice work Ved!
It looks good in blue.

John

 

[vederstein]

Sometimes I just don't get it. I remade the right hand steam chest and reamed the valve rod gland 0.1875. When I assembled the engine, the new steam chest leaks worse than the old one. I reamed through both ends of the part in one pass. After assembling, I can see the gap between the valve rod and the gland. Perhaps this reaming set I have is just complete junk.

Well, I'm out of castings so I'm out of work for awhile. Perhaps next week I can get the leak resolved. Next time I'll go to my -.001 press fit reamer and lap the two parts together?

...Ved.

 

[davidyat]

Ved,
Looking at what your problem is, what's the reason the valve rod exits the top of the steam chest? When you saw my 1890 Model Machine shop, I finished the Coke Bottle steam engine from PM Research and it has the same type steam chest and no exit at the top for a valve rod. It is much smaller than your design and works fine with only one entrance hole for the valve rod. It uses a round rubber doughnut that is squished a bit to keep it air tight at the only inlet for a valve rod. There is a hole at the top for air not a valve rod. If you'd like to see the blue prints of the coke bottle, let me know.
Grasshopper

 

[vederstein]

The reason for the exit is to show more moving parts. It's there entirely for looks and has no real purpose.

Actually I went as far as to consider making the valve covers out of a clear plastic, but reconsidered knowing that I'm eventually going to run this thing on live steam.

Now for a bit of engineering knowledge: In mechanical engineering circles, a sliding plain bearing requires the length of the bearing to be at least 2 times the diameter. Otherwise, there's the chance that the rod may bind in the hole. Being that the rod is 3/16 diameter, the bearing surface needs to be at least 3/8" long. One one side of the part we have that, so all is good. Two short bearings spaced far enough apart will also meet this requirement.

On your version of this engine, you don't need to drill all the way through if you choose not to.

Thanks for the inquiry.

...Ved.

 

[Andy Munns]

On most actual small steam engines (<5" bore?) the lower valve rod guide and gland does all the guiding, but over many years wear leads to slop. Larger engines often have a tail rod guide - these are mostly blind and therefore capped to stop leaks. You could thread the OD and fit a cap. Also could fit a cap nut on bottom guide and build a gland. Sometimes engines have a packed tail rod gland but I have never seen this in practice. Steel valve rod in aluminum not ideal with steam so you could sleeve with bronze bushes, perhaps also incorporating grooves to create a tiny labyrinth seal.

 

[vederstein]

I keep finding new and inventive ways to screw up.

I created two steam chest castings and of course started with the better of the two. As I was making a finish pass, the endmill slipped in the collet and I created a sloped surface. CRAP!!!!

So I machined the other one.

After re-assembling the engine I saw that I have a porosity issue. I'll plug it with some JB weld after the RTV sealing I use to seal the steam chest "sandwich" cures.



Anyways, my excessive leak around the valve rod is gone. This time I reamed the gland .1870 and then used a piece of 3/16 brass roundstock to lap the gland to size.

In the end, the engine will run (no load condition) on 5 psi. It will run the Spin Art Machine at 10 psi, but a bit too slowly. 15-20 psi seems to be the sweet spot when running the Spin Art Machine.

Although my casting certainly isn't the prettiest. I'll look less bad when I paint it. I'm considering this win (especially after trying about five times getting this component not to leak profusely).

...Ved.

 

[davidyat]

Grasshopper here,
I'm working on Ved's 2 cylinder engine. Working slowly and following Ved's blog so as not to make the same mistakes. Pictures of my progress so far. When I get to the steam chest, I will probably machine it close to size out of CRS steel I have laying around. Then I will bore a hole length wise while it's still solid and insert a 3/8 " solid brass insert and braze or silver solder it with plenty sticking out either end. Then bore the brass a bit smaller than the valve rod diameter. Then hog out the valve chamber taking the brass rod out of the inside. Lap it when finished to the valve rod. The future engine block is in the
background. Will be a lot of aluminum on the floor for future melts and pours

 

[vederstein]

David,

following Ved's blog so as not to make the same mistakes

That's a lot of mistakes to account for....

You seem to be flying through this thing. Being my version has taken about 5-6 months now, you're making great progress. I see the giant chunk of AL round for the block. This will be a good use for the dividing head you recently procured.

On a side note I see that you're a "Well known member" with 109 posts. I have 583 and "Must do dumb things..." (Years ago I figured out how to manually change the member description to say whatever I wanted it.) But as for defaults, this makes me wonder what the various criteria for various levels?

...Ved.