Another Atkinson Differential build

[Gordon]

Pistons are .750" Diameter. The photo posted on 6/2/20 is 1st photo of the engine partially assembled. Right now awaiting delivery of hex Stainless to make the screws to hold the Intake/Exhaust Valve Manifold (The Brass part in front.)

I am confused. The Gingery design and the Pendergast design both have 1 1/8" dia pistons. Does yours have 3/4" dia pistons? That certainly makes a different design.

 

[stragenmitsuko]

The pendergast design is even bigger . 1.25" od on the pistons .

 

[Gordon]

In looking again at his design I find that he offers a kit with a 10" flywheel and plans for one with a 4" flywheel. If we cannot get the larger one to run I cannot imagine the problems with one half that size.

 

[Tim Wescott]

So, it looks like this is going from the patent drawing -- could that be why these things don't work well?

I don't know about the late 19th century, but in the late 20th century the point of a patent drawing was to get a patent, while making it as hard as possible for someone to duplicate.

 

[dsage]

Probably is the reason. But somewhere I ran across a link where someone took the patent drawings and built one based on them. He had to "wing it" in a few places becasue not everything was specified. The article had a picture of it completed and he "said" it ran after a bit of frustration BUT there was no video proof.
Same thing for the Gingery version. There IS a Youtube video of it running but the book says it might be VERY difficult to get running and that a few pieces might have to be re-made to tweak it into submission. No very re-assuring to be sure.

Not to be too confused - I think Ken is building the one from Dave Perralt that apparently DOES run. It has some very strange valve actuating mechanism on the front so it's very different than the Gingery and maybe the Pendergast -(sorry sp?) for sure.

Perhaps Ken can post a larger picture of the front of the engine. ( i.e. take the picture in a higher resolution say 3mb in file size and paste it into the next post. (rather than the thumbnails presented thus far).

 

[Steamchick]

Hi, just picked up on this thread... from my experience (engine design and testing with Nissan in the UK) rotating rings is really the way that wear creates the "perfect circles" of rings and bores during running-in. The finest of spiral grooves from machining in bores and ring surfaces is "worn flat" by lapping, but not completely polished. The lapping or honing causes much finer grooves in the flatted peaks of the machining. All the valleys are oil reservoirs to prevent pick-up and siezing. But the finest peaks from honing / lapping are polished by rings running past bore surfaces, but the ring rotation helps ensure the high spots find each other and lap away, hence the rings and bore must become perfect circles.. Ring stops used on 2-strokes are a necessary evil to prevent ring ends from fouling cylinder ports after some rotation. Avoid on cylinders without side ports, if not part of the original design. Don't worry about ring gap alignment, it happens on your car's engine frequently, without significant trouble. The oil consumption change when a 3-ring piston in the car engine aligns the gaps is measurable on the dynamometer test kit (blow-by and exhaust gas monitoring and analysis). Manufacturers factor in this natural oil consumption in the service intervals, so I suggest you do the same on your model. When rings align, oil passes through the gaps, this causes gases to be withheld.. so excessive blow-by doesn't become a problem on the full sized engines. Maybe models have exactly the same effect?
Please add more expert comment, I love to learn!
Cheers!

 

[Ken Brunskill]

At the suggestion of Both Dave Sage & Dave Perreault I created a utube video: (My 1st - sorry for the amateurish narration)

Filename
4th Shot Atkinson operation.MOV

 

[Hettinger]

I see your going with two separate rings vs. the paired single ring. I was hoping you were going with paired ring. Did you go with heat treated ring or ( my preference) all machine ring? Congratulations on your progress and excellent work. Bob

 

[Gordon]

At the suggestion of Both Dave Sage & Dave Perreault I created a utube video: (My 1st - sorry for the amateurish narration)

Filename
4th Shot Atkinson operation.MOV

Thanks for that. That engine valve configuration is a completely different setup than the Gingery or even the original patent drawings. With a mechanical valve actuator it stands a chance of working.

 

[dsage]

Yeah
In fact I'll bet it does. I believe the designer has displayed it running at Cabin Fever.

 

[stragenmitsuko]

Now I understand what the function is of that extra central connecting rod .
It actuates the valves .
Wonder if this can be added somehow to the other designs out there
thx for the vid .

 

[Ken Brunskill]

I see your going with two separate rings vs. the paired single ring. I was hoping you were going with paired ring. Did you go with heat treated ring or ( my preference) all machine ring? Congratulations on your progress and excellent work. Bob

Bob, based on the comments of steamchick, have decided to go with (2) rings in one groove for the pump piston where there are no ports, and (1) ring per groove in the power piston.
As for the method of making rings, I made them both ways, the Trimble method, less fixturing and machining time, and the unheatreated way. Then used a Chattilion force gage to measure the force it takes to close the gap, either way it came to 1.3 lbs.

 

[Gordon]

Just found this. Delete if the link is not permitted.

 

[stragenmitsuko]

That is what ken is building if I'm not mistaking .
The piece of copper on the right seems to be a coolant tank .

 

[Gordon]

Since Dave Perreault seems to offer both a larger kit with a 10" flywheel and plans for this smaller engine with a 4' flywheel I wonder if the larger model uses the same valve setup. I have not been able to find much information on his designs or kits. Anyone familiar with his offerings?

Gordon

 

[Ken Brunskill]

Gordon & Strangenmitsuko:

Yes, I am building Dave Perreault's design. I would heartily endorse it, as the price is reasonable, and so far I have only encountered one error which he concurred. Mine should be up & running soon. I do fly fish also and need to get ready for a 4 day trip. By the way the RH cylinder is the coolant tank, I am adding a pump and cone screen, so the engine is doing something, not because I think it is needed, just because . . .

 

[dsage]

Ken:
Do you have a link to a website or email for Dave Perreault so as to purchase the plans for his engine?

 

[Ken Brunskill]

Ken:
Do you have a link to a website or email for Dave Perreault so as to purchase the plans for his engine?

Dave, I had copied him in an email to you a few days ago. For some reason my cpu is not loading my email server, I need to het that resolved, when done I will send you his contact details.

 

[propclock]

Very interesting results on the 2 ring methods = spring factor . Good luck with the fish.

 

[Gordon]

This is the email address he posted on Model Engine Maker in February. Let us know if you get any more information on what he has available and prices.

[email protected]