Twin Rotary Valve Engine

[PaulR]

Started another project while cogitating on the crank+eccentric uniflow idea, this one is a bit more straightforward: a twin single acting rotary valve engine with Scotch yokes driving the crank.

Made the cylinders from old towel rail tube and 5/8" brass square with mild steel pistons and temporary rods. Made the two valve blocks, the simple cranks and the flywheel. Need to find a piece of steel (or brass) the right size to make the long inboard cylinder support and a piece of sheet for the base.

[PaulR]

Made the yokes today. The vertical slide was bouncing around all over the place for some reason, maybe the slot drill is a bit worn or I just have the speed right? Anyway, the slots needed considerable attention with a file to bring them anything like straight. They're wider than planned so I'll just make the pins a bit fatter 

[PaulR]

Made the crank pins and washers and the inboard cylinder support - drilling the 1/2" holes for the cylinders was quite thrilling on the rickety old drill press but it came out alright even if my garage was full of burnt cutting oil fumes! Here are the bits placed together - the two copper air tubes will go through those holes in the middle down to the brass valve blocks. Man it's an ugly duckling and the blocks to guide the rods from the yoke have to be made yet.

[Sanjay F]

I think 'interesting' rather than ugly! Coming along nicely following along 

[PaulR]

I've been having a bit of a nightmare with this stage of the build. Soft soldering comparatively thick chunks of brass and steel to opposite ends of a very thin tube is tricky, every time one end was soldered the other parted company... and there are still some tubes to solder in place! In the end I desoldered everything so I could go the silver solder route instead. After lots of careful filing, emery cloth and cleaning I got rid of all the soft solder and the silver stuff went like a dream in comparison. I should be able to silver solder the other end without any issues and can then soft solder the tubes.

[Sanjay F]

Looking good, steady progress 

[PaulR]

Looking good, steady progress 

Cheers! Got the other end soldered up and all seems ok. Turns out my 'brass' towel rail is plated copper! No matter, it does the job.

[PaulR]

Not much time to devote to the workshop lately but managed to get the base plate to size, cut-outs filed and the assembly fixed to it.

[PaulR]

Only to find that I made a booboo and need to make the cut-outs for the cranks deeper - more filing in my next workshop visit!

[Jeff123]

Hi Paul
Just read through the entire, very interesting, as ever in your case.

Your drawing shows the crank pins set at 180 degrees. Is that just for convenience,  making the drawing easier or are you intending to set them at 90 degrees.

Just curious,  like I  say interesting stuff
Geoff

[PaulR]

Hi Paul
Just read through the entire, very interesting, as ever in your case.

Your drawing shows the crank pins set at 180 degrees. Is that just for convenience,  making the drawing easier or are you intending to set them at 90 degrees.

Just curious,  like I  say interesting stuff
Geoff

Thanks Geoff, it was just so I could check clearances when things are at their maximum extent. I think they'll need to be set at 90 ish

Made the part to guide the yoke rods and loosely  assembled everything to check alignments and it looks ok. Just the pipework to do and then I can try to get it going.

[PaulR]

Design error #too_many ... it isn't possible to fit the pipe with the right angle bend. Oops. As a workaround I've plugged the original inlet/outlet holes and will take the pipe up further into a brass 'connector' then back down into the back end of the cylinder. Here the gist with the bits of pipe just placed and in/out flow (blue/red) indicated. What a monstrosity.

[Sanjay F]

As long as it works ..............

[PaulR]

As long as it works ..............

Touch and go this one I think  Never used so much Loctite on a build, it's probably going to need some JB Weld in places too, just to cover up some corrections I had to make.

[PaulR]

@Jeff123 - when I assembled the engine it seemed that having the cranks at 180 was the way to go.

TBH I've had little time in the workshop or even to think about the thing in detail since starting this one. Hopefully that'll change in a month or so when other hobbies are out of the way for a while.

Anyway, I connected up the various bits and had to spend ages turning it over by hand one cylinder at a time as it was binding too badly to run on air. Once I'd got it freed up it starting running pretty smoothly without any real problems. It has a couple of minor issues: leaks around some of the pipes but those can be fixed easily and an annoying cosmetic issue that can't be fixed: both of the pipes from the inlet manifold to the valve blocks are skewed. Somehow I managed to get the hole at each end slightly where it shouldn't be, the left side more-so than the right:Lol: Ah well, I can live with it.

<a href="https://www.youtube.com/watch?v=LMCtkIlYIP8" target="_blank">http://www.youtube.com/watch?v=LMCtkIlYIP8</a>