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Opposed Piston Engine?

Posted by Peter Brow 
Re: Opposed Piston Engine?
July 28, 2018 06:18AM
Quote: "You can't increase the compression ratio by taking two gas engines and sticking them together. The stress will be the same. The piston and cranks will experience the same forces as if they had a static head. "

If it is twice the cylinder volume, compressed to the same volume of a cylinder with fixed head, the pressure is indeed higher, the loading on each crank is increased.

Quote: "then you need a series of gears, with highly-loaded gear bearings and bearing mount structure, to link the 2 crankshafts."

A timing belt of adequate specification would serve well here and omit the need for difficult to manufacture expensive noisy gears . One crank could be ran 180 out of phase.

-Ron
Re: Opposed Piston Engine?
July 29, 2018 12:39AM
Hi Ron,

Yes, with the right belt and pulleys, I think that would work. I was automatically assuming that a new twin-crankshaft opposed-piston engine would have to be built the way they were in the past, at least in the illustrations which I have seen.

Also, come to think of it, 2 engines could be grafted together this way, and it would run. But I don't think it would have the reliability or longevity of a professionally designed opposed-piston diesel. It's a very tricky project.

Also, a steam "Deltic" engine is possible; just don't use the rotary valve that Lear's team used. That was the design feature that made Lear's version a failure. I'm not sure what I would use for valves on a steam Deltic, or a steam version of other opposed-piston engines, except for unaflow exhaust. Maybe poppet inlet valves, feeding to the space between the pistons somehow.

Peter
Re: Opposed Piston Engine?
July 30, 2018 05:12AM
Hi Z,
Respectfully and after some double checking on my thought process, I do believe that in theory that if you put two (2), 2 cycle IC engines Cylinder head to head, remove the actual heads to make it cylinder to cylinder connection; you would in fact increase the compression ratio. We can talk stress and strain later.

To All,
OK...here is the design plan, to use 2 weed-wacker engines, pull the cylinder head, bolts and bolt them together with longer threaded rod. Now create a plate to hold the 2 cylinders on the face affixed where on-put shaft exits the block. Use 2 small gears on the cranks and one (1) larger in the middle to form the output shaft to perform work. On the end of 1 of the small gears, the crankshaft, put a blower. On the end of the other can be a alternator.

An idea for the fuel injector would be in principle the same as the Stanley oil pump. See attached picture. This would be driven off one of the crankshafts on an eccentric.

Regards,
Rick


Re: Opposed Piston Engine?
July 31, 2018 03:25AM
Hi Rick,

Hey, that is the Stanley cylinder oil pump which I mentioned recently here, with the spring loaded additional plunger, of adjustable spring tension/travel, to adjust delivery rate. I am currently finishing the design & blueprinting of my previously-mentioned oil pump design, with 2 cylinders and 2 adjustable-travel plungers, one to meter oil to steam line/engine and the other to scavenge/recycle cylinder oil from the surface of the water tank. Sounds simple, and it is simple in principle and machining/fabrication processes, but lots of parts and details to work out. Only things left to blueprint now are the bolt-hole layout for the pump-cylinder mounting plate/board, and the sealed oil-bath sheet-metal enclosure for the mechanism, both relatively simple compared to the other stuff now worked out. The pumping/adjustment principle is different, similar to the oil pump used for Model 735 (circa 1918) Stanley. The overall design/blueprint process has been one heck of a time-consuming mental workout, but I think that the actual build will be relatively fast and simple. Mostly drill press and bandsaw work, with standard precision bar stock/billet and off the shelf parts providing most of the dimensions. 50 numbered parts to date, and 22, 8.5x11" sheets of 1/8-square graph-paper shop drawings. Maybe 2-3 sheets left to draw. Unit looks like many of the modern-design commercial off the shelf "pump in a box" units.

Water and fuel pumps, now almost entirely blueprinted, are the same way. Just need to convert a few last details into my "follow the step by step fabrication/assembly procedure" shop drawing format. Then I just order parts/materials, fire up the machine tools, and follow the shop drawings. Hopefully this will minimize "shop floor modifications/design work". For duplicate and multiple parts, I plan to make up simple jigs and fixtures to reduce layout work. Clamp workpieces into jigs/fixtures and align saw blades, "stick drill bits in holes" etc, instead of screwing around with scriber, center punch, layout tools, setup work, etc for every single part. If the pump units work well, which I think they will, that also means [relatively] quick/easy fabrication of additional units.

I had set myself a deadline of July 1st to finish all this stuff. Well, that didn't happen. Frustrating. But the pump blueprints/shop-drawings are very close to finished now. Close enough that I don't want to jinx anything with a "revised deadline/finish date".

Peter
Re: Opposed Piston Engine?
August 18, 2018 07:57AM
You can see opposed piston diesels in action when they crank this baby up every so often!
[silversidesmuseum.org]

edit: TODAY AT NOON! It should be on-line live if you can't make it in person, just checked.

have a nice day
Steve



Edited 2 time(s). Last edit at 08/18/2018 08:01AM by smcmanus.
Re: Opposed Piston Engine?
August 18, 2018 09:33AM
Silversides is a fun visit. I used to work on her occasionally, on Navy Reserve drill weekends over in Grand Rapids. Funny thing is, most tourists thought there was nothing a bit unusual about sailors, in uniform, working on a local museum....
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