A Simple Uniflow Engine

[gary.a.ayres]

Thank you Stuart!

[gary.a.ayres]

The cylinder and its support columns were bolted to the base:



The assembly feels completely rigid, which was a pleasant surprise given that the support columns are quite long. It needs to be rigid, though, given the weight of the piston and the probably high speed of the engine, so the cylinder side braces will further stabilize the structure. For this, clearance holes will have to be made in the frame sides. The approach will be similar to that used in marking and drilling the base for the support columns. Transfer screws were placed in the two blind holes in one side of the cylinder:



One of the frame support bars was reversed and fixed to one of the frame sides the wrong way round so that the frame side could be slid right up to the cylinder unimpeded. The appropriate area of the frame side was blued up:



With the base acting as quite a nice surface plate, the frame side was moved up towards the transfer screws. With the frame sides bolted to the frame support bar (which is made of aluminium angle), the sides are not perpendicular to the base, so I shimmed the support bar to correct this. You can see the top of the square that I used to visually check this in the foreground here:



For the record, when the frame is assembled, the frame sides are pulled into the vertical by the frame cross-braces.

With the longitudinal alignment of this setup confirmed by the position of the frame support bar relative to the base, I supported the cylinder (hidden by the frame side in this photo) with my left hand, and 'trepidaciously' gave the appropriate spot on the frame side a sharp tap with a rubber mallet.



This worked well - the transfer screws marked two small points on the frame side. These were opened up with an automatic centre punch, then a traditional centre punch to create marks which I'll be able to locate in the mill using a wiggler.

The support bars and bearings were then removed from the frame sides...





... and the two sides were bolted together using the existing clearance holes...



... which will enable me to drill the clearance holes for the fixing screws for the cylinder side braces through both frame sides at the same time.

[MJM460]

More good progress Gary.  The flywheel came out well too.

MJM460

[gary.a.ayres]

Thank you, MJM.

 

[gary.a.ayres]

Another reassembly, though it won't be the last.

The main reason was to test the support bars and columns for the cylinder. They appear to be ok, and the cylinder seems to be very rigid:

The crankshaft felt a little tight again though it eased off considerably after  some oil and a few turns.

The new steel flywheel was also put on as a trial fit though it's not visible in either of the two photos.

It's still the old crankshaft that can (almost!) be seen in the pictures. Probably due to my having reduced the width of the frame, there is no longer any visual sign of it running out. I reinstalled it because the replacement shaft isn't finished yet. Subject to further assessment, I may still be able to use the old one, thereby potentially freeing the incomplete new one for another project. We shall see...

Getting there! I'm starting to see the light at the end of the tunnel as opposed to the tunnel at the end of the light.

She's a bit of a beast...   

Main jobs remaining:

Shorten screws through cylinder side braces.
Shape frame sides and make decorative holes in them.
Cylinder drain cock.
Cylinder head gasket.
Exhaust pipes and manifold
Wooden base.[/list]

[gary.a.ayres]

PS sorry about that bit of rogue code at the end of the previous post.

Tried deleting it but it won't go away...

[Don1966]

Love the fabrication work Gary.......


 
Don

[gary.a.ayres]

Thanks Don.

 

[gary.a.ayres]

The fixing screws for the cylinder cross-braces were cut to length and refitted, and the outline shape of the frame sides was roughly marked out, along with the positions for new holes for the frame cross-braces on the finished engine:





The flywheel is hidden at the other side of the frame in these photos. The brass disc that you can see was one of two flywheels which I originally made, but were too small. I'm thinking of cutting a groove round the perimeter of it to convert it to a pulley for a thin round section drive belt. That would give the engine two drive pulleys, the other one being the aluminium pulley beside it which is crowned for a flat belt. The different sizes of the pulleys could allow for two different speed ranges, depending on the sizes of the driven pulleys on whatever  it is that this engine will end up driving. I have some ideas about that but will keep them to myself for now...

Also, further to discussions further back in the thread about oil feed rate to the main bearings, I remembered I have these:



I bought them from PM Research quite some time back for another project which I have not yet begun, so I'll probably use them on this engine and buy more later for the other project. They are very small but still too wide for the small space available above the bearings, but I think I have a way round that...

[gary.a.ayres]

I thought I'd give the engine a second test run before moving on to the final stages, given that since the first test I have properly installed the cylinder, reconfigured the frame and made a new flywheel.

The original crankshaft shows no sign of wobble (not sure what happened to that!) and the flywheel and pulleys appear to be running pretty true. A bit of lateral play can be seen in the crankshaft but that should be easy to fix. I played around with the timing a bit by winding the valve pin in and out, running the engine and measuring the protrusion of the pin. The clip below shows it performing quite well, I think, on my small compressor:

<a href="https://www.youtube.com/watch?v=wU32XjxHvHs" target="_blank">http://www.youtube.com/watch?v=wU32XjxHvHs</a>

Now, on to the final stages. Still quite a bit of time to go in this build, but it's definitely going in the right direction now.

[crueby]

Running quite well at the slower speeds. The engine is quite a bit larger than I had thought, or that was a shop-elf-shoe in that one spot. At the higher speeds it shakes, but that is expected without balance weights on the crank.

Nice!
 

[MJM460]

Well done, Gary.  It runs quite nicely with the modifications and tuning you have done.  It will make the finishing details so much easier, now you know it runs well.

MJM460

[gary.a.ayres]

Thanks guys.

@ Chris - it's a shop elf shoe - size 10, UK size (continental 44). Some elves have big feet!

It is indeed quite a large engine. Generally, I'm aiming to build as big as my machines will allow, and this is pretty much at that limit. I can only dream of a huge workshop with industrial scale machines... I'll post its dimensions and weight in this thread once it is finished. Yes, I should have expected it to shake, given the lack of counterweight on the crank. Another factor may be that currently (and temporarily) the engine is just sitting on the ends of the stainless steel screws that attach the frame sides to the base, and it was running on the smooth wooden floor of my shop. This may have made the shaking more visible as it skated back and forward with the stroke (though of course the shaking is still an issue). When it's done it will be fixed to a heavy slab of oak on rubber feet which I think will probably at least keep it in one place. If that doesn't keep it within reasonable limits, I may make another crankshaft with a counterweighted crank and swap them over... or I may just put it down to experience and put a counterweighted crank on my next engine if it needs one.

@ MJM - yes, it's motivating to see it run at this stage. Having the way ahead clear should make the remainder of the build a pleasure.

 

[gary.a.ayres]

Only modest progress over the last couple of days.

Due to the trial and error that was required to get the conrod, piston and pin assembly to the optimum length for the engine to run, I had left the conrod unfinished so that if necessary it could be adjusted by screwing it in and out of the crosshead. Now that the engine is pretty much tuned, the length of the conrod has been determined. This, however, left a gap:



I had a tiny piece of bronze bar which had previously been drilled to size. With a small amount of facing and turning, it would fit. I press-fitted it on to a piece of steel bar which acted as a mandrel, and turned and faced it to the required dimensions:



I had previously made quite a deep undercut behind the threaded section of the bronze rod. This caused quite a bit of slop in the spacer ring once it had been passed over the threads, so I applied some Loctite 603 and made sure the spacer was centred until the adhesive set. I also used some red Loctite 542 threadlocker on the thread before reassembly:



The slop in the spacer wasn't a major issue, but it wasn't ideal either. No big deal, but a learning point for next time: don't go mad with undercuts!

The finished connecting rod:

[crueby]

Nice solution!