Another Atkinson Differential build

[dsage]

Ken:
If you come up with anything different than Gordon posted above - in so far as how he'd like to be contacted for purchases post it here. Otherwise..... I guess we're good.

 

[dsage]

That email should work.
He seems hesitant to post here (IMHO) to promote his work.
I have been emailing him.

Gordon:
Not to hijack this thread. Dave Perreault apparently researched the original patents for the differential and figured it out and built one. He used to (maybe still does) offer castings for it. Have a look here.

 

[Gordon]

That email should work.
He seems hesitant to post here (IMHO) to promote his work.
I have been emailing him.

Gordon:
Not to hijack this thread. Dave Perreault apparently researched the original patents for the differential and figured it out and built one. He used to (maybe still does) offer castings for it. Have a look here.

I have seen the video and agree that whatever he did he has a working model.

In looking through my stuff on my computer I found that I had a copy of a purchase contract from him which I apparently got back in 2017. At that time he was offering the castings for $450 which was a show special with $100 discount. Not to downplay his efforts or expertise but that is more than I am in a position to pay. I am retired so I have more time than money. I would be interested in a set of his drawings but quite honestly mostly to see what he has made different than anything I have been trying to do.

I have thought about trying to play around on cad with his mechanical valve idea which he uses on his Mini. Not sure that I want to spend that much time on more Atkinson Differential design which I have already spent too much time on. At this point I have moved on to other more productive endeavors.

The patent drawings and application are reprinted in the Gingery book but like all patent information that is to obtain a patent without giving away too much design information.

Gordon

 

[dsage]

All valid points. I agree.
I consider the sliding valve addition as not true to the original design. (certainly not looks wise) which is what I was going for. So I won't be going there. Also it's too much work to add it now.
Having said that I don't like to have an engine that doesn't run sitting on the shelf so I might eventually end up with some sort of modification to "fix it" and hopefully not be too far from the original appearance

Enough said here in Ken's thread. We should continue in your or my thread.

On that note I think Ken will have success with the Dave P. design. It looks solid.

 

[Ken Brunskill]

Dave & Gordon, near as I know there are not any castings available for the Perreault Mini-A design, it would be easy task for those of you with CAM milling capabilities, and a fun conventional machining task for rest of us (Hey, isn't why we enjoy this pursuit.) By the way I made some of the part twice, not being pleased with the 1st parts. I paid $35 for the set of plans last year and as I've said before think they are well done.

 

[dsage]

Your right, There aren't any castings for the Mini.
BUT Dave was at one time (maybe still) supplying castings with drawings ($500+) for the original large patent designed engine. I'm not sure if he would supply ONLY drawings for the original.
And yes the mini would be easy enough to make from the drawings. But I'd rather keep closer to the original design.

Continue on Sir. We want to see it run

 

[Richard Hed]

I was just watching a vid on Diesel engines and I thot maybe someone might like to see this:



It's not about minis but it is interesting.

 

[Ken Brunskill]

Mentioned a few posts back that I was going with (2) rings in (1) groove for the Pump piston only, well . . . . . I am finding out how fragile .025" thick rings are, see photo. Good thing I made extra's. The remainder are safely installed in the cylinder now! After that experience, feel that those thin rings would likely have been an issue crossing the .187" dia port holes that come in at an angle (making them obround in the bore).

 

[Gordon]

I just received the plans for this from Dave Perreault. I have not had a chance to look too closely yet but the instructions say that you have to run it for 4 or 5 hours with an electric motor to get the rings seated properly.I am not too sure that I want to get into another engine which takes a lot of fussy tweaking.

 

[Ken Brunskill]

I am just at that stage now, so very soon (next week, as I am an ardent fly fisherman, and there is particular hatch going on in a N. Calif. Lake, so . . . . . ), I will be doing that and then start the process of getting it to run, I have a good feeling as using Solidworks 3D modeling I can observe the interactions of the valve, etc.

 

[stragenmitsuko]

There are thougts against using an E motor to run in the rings .
The pressure of the combustion should seat and wear in the rings .
Offcourse if there's no combustion possible due to ring leakage ....

I've also been told by a professional engine rebuilder that changing rings
without honing the clinder is pointless . The "rough" spiral surface left by the honing
works as an abrasive and wears in the rings . Altough it sounds logical , don't know if this is true .
I've changed rings on countless occasions without honing and never had bad results .

Let's hope you have a runner .

@Gordon , is that the full size or the mini plans you've got .

 

[Gordon]

There are thougts against using an E motor to run in the rings .
The pressure of the combustion should seat and wear in the rings .
Offcourse if there's no combustion possible due to ring leakage ....

I've also been told by a professional engine rebuilder that changing rings
without honing the clinder is pointless . The "rough" spiral surface left by the honing
works as an abrasive and wears in the rings . Altough it sounds logical , don't know if this is true .
I've changed rings on countless occasions without honing and never had bad results .

Let's hope you have a runner .

@Gordon , is that the full size or the mini plans you've got .

It is the small one like in this thread. I am a little bit disjointed because the lines are light grey and hard to see with my old eyes. The dimensions are dark but the main part line are very light. I suspect that he made the drawing with the lines some color and then printed in greyscale. That is what my cad drawings look like so I either print in color or all lines to black.

 

[dsage]

I just received the plans for this from Dave Perreault. I have not had a chance to look too closely yet but the instructions say that you have to run it for 4 or 5 hours with an electric motor to get the rings seated properly.I am not too sure that I want to get into another engine which takes a lot of fussy tweaking.

Oh no. Shades of Gingery. I hope it isn't so. Also disappointing on the poor quality of the drawings. I hate that.
I guess Ken did the right thing redrawing them.

 

[Gordon]

Oh no. Shades of Gingery. I hope it isn't so. Also disappointing on the poor quality of the drawings. I hate that.
I guess Ken did the right thing redrawing them.

I assume that the drawings are accurate. Ken redrew them and found only one minor error. The problem is the quality of the printing. Due to the lines being greyscale they are hard to read. If I do make one of these I will also probably redraw them in cad but I frequently do that with my projects.

 

[dsage]

Yes. Redraw is standard with me. But the running in with an electric motor worries me (as was the case for the Gingery - page 111). Gingery said Twelve days of running in before it got to running on on it's own. Crazy.

 

[Ken Brunskill]

Well, I fabricated all the parts as Dave P. had designed them, assembled everything less the rings and all operated smoothly, then observed a fair amount of stiffness with the spanking new rings installed, so the thought expressed by strangemitsku might turn out to be true. (BTW, Fishing was OK lastnight, catching not so much). Will be doing some E motor run in starting Monday, with the suggestions and comments here, think I'll try to power it on its own after each hr. of E motor breaking in. Will keep posting as progressing.

 

[Ken Brunskill]

Regarding the light feature lines, my bet it is because Mr. Perreault did not desire them to be xerox copied, I tried that and those light lines do not copy or scan worth a darn. Wise on his part, IMHO.

 

[Ken Brunskill]

Slightly different topic, maybe worth a individual post? Anyone come up with a method and/or device for measuring compression of one of our model engines? I.E. measuring via the 1/4-32 thread hole? I am sure I can come up with something, but why reinvent this 'wheel'?

 

[dsage]

I made an adapter from 1/4-32 to whatever is on the end of the hose of a standard compression gauge. I added an o-ring above the threads so you don't have to crank down on it and possibly damage the head of the engine (since there generally aren't many threads).
Works fine.

 

[Ken Brunskill]

I made an adapter from 1/4-32 to whatever is on the end of the hose of a standard compression gauge. I added an o-ring above the threads so you don't have to crank down on it and possibly damage the head of the engine (since there generally aren't many threads).
Works fine.

A picture would be a great addition to your 'elegant' solution. Elegant IMHO, is simple, efficient & effective.