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Peter, thanks for the supportive comments, I've sent the originator of the plans a note to see if he has any pressure or vacuum data on his running model. I'll spend some more time making some careful measurements with various valve placements, the initial trial I reported was a 'WAG' for the...

Here is a confession that you might get a chuckle over, or rememeber doing the same or similar thing. I was desiring to measure the compression and vacuum on the Atkinson Differential I've built as well and then have a device for future builds. (Reference post of Feb. 16th.) I'd created several...

Great idea, thanks! I've come up with a 'Smoke Test' device by modifying an old CPAP machine (produces a really low pressure). I use incense in the water chamber to produce the smoke, and an adaptor to attach a fitting from the CPAP machine to the sparkplug hole.

Like your idea of a 'stethoscope' type device - way simpler than a machining a tool that won't work anyway (still enjoyed the designing time ;)). Haven't totally given up on that idea just yet, stubbornness, I guess. I've come up with a SolidWorks design that might test compression and vacuum...

One of the issues that come to mind is: how much does the area/volume prior to any type of check device (before the gages) come into play? Seems like that would get both pressure and vacuum, as I'm considering checking at the sparkplug hole. Maybe I'm stating the obvious :rolleyes: & it can't be...

Not as much as determining the intake integrity and timing. 1st application is on an Atkinson Differential model, then on to a Parcell & Weed model.

Interested in how others have come up with means of testing the vacuum on their model engines. Wondering if a Schrader valve would be useful & what it's proximity to the cylinder/cylinders ought to be.

This design has been accomplished more from visual observation of photo's and bit's & pieces of the metric plans posted way back . . . my thoughts are shortening the Cylinder Base, would not look right, of course I could make the piston taller (move the wrist pin down) to accomplish that...

Great comments! Thanks :)

Interrupted a cabinet project to noodle out the compression ratio on the inch 1/4 scale benz at top dead center the volume of the combustion chamber with the reduced cavity is .57 cu inch and the volume of the chamber at bottom dead center is 2.945 cu in, that comes out to be north of 5:1, if I...

Jason, Bingo! You are absolutely correct I'd mis-read the volume numbers initially the smaller version is 88% smaller. Original is .33 cu in, smaller is .04 cu in. About the welding, did a small welding experiment today, finding plain silver soldering is perfect see photo. Left side is Safety...

Tony, Great idea, I checked my original idea (Glad I have not welded anything yet! :)!), that cavity was .05 cu in, this redesign reduces that 20% to .04 cu in. Does not seem like a lot but in a model might make a huge difference. Now to the shop to re-remake that combustion chamber.

Jason, No there is no porting in the head, the valve at the top opens the passage to the exhaust, there is a slide valve that opens the fuel inlet. I felt it easier to make the 'D' shaped area a separate piece as that allowed me to clamp the 'housing' and turn the inside & outside (Photo...

As promised here is how I plan to fabricate the three main parts that would most often be castings. Also is a photo of the head components which is ready for welding. On the welding, since I was out of acetylene I stopped in a my local Airgas supplier and ended up with Radnor 95/5 that has a...

Thanks Craig, for strength, my thought is to tack with TIG (I have an Miller Econo TIG) and fill with the 620 deg. Silver solder mentioned by jasonb, the JB Weld I'll use to obtain consistent fillets. It will all be painted Red any way. Later this week end I'll post something where I have...

Spent some time noodling out how to approach this engine as a weldment vs. a casting. I have the head machined and ready for brazing, just need to replenish my acetylene first. (Concept attached.) Today completed designing Rev 1a of the cylinder and components, starting to be convinced it is...

Very nice indeed! Doing you own casting, is something I contemplated, however now have sold off all the gear and am too close to retiring my shop to restart now.

Craig, looked at the Martin Casting site, and the 7" curved spoke flywheel would (IMHO) the best choice for this 1/4 scale, that is what I,m going to go with.

Definitely nice looking job, as mentioned a little JB Weld, sanding & painting it will look great. Is that silver solder or braze. my silver soldering does not leave that much of a fillet.

Craig & Jason, OK did not take a lot of urging to reignite my interest, here is this morning's Solidworks effort, the attached is what I see as the logical approach to making the head from solid material, it would all be steel the colors are merely for component identification. I'll of course...