What engine would YOU build

Discussion in 'General Auto Conversion Discussion' started by Winginitt, May 15, 2019.

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  1. Jul 19, 2019 #141

    PTAirco

    PTAirco

    PTAirco

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    I once got totally consumed with the idea of an aircraft barrel (axial) engine. It has a lot going for it, starting with its cylindrical shape - you cannot get aa piston engine with less frontal area for the power. My idea would be this: 4 cylinders, opposed pistons, port valves, compression ignition. Picture the cylinders like the chambers of a revolver. Pistons go in from either end. Each connects to a wobble plate mounted on a straight shaft. This converts the reciprocating motion into rotary motion. It also eliminates about 93% of piston side loads. Front end drives the prop. Rear drives a vane-type blower (it's essential to make it run, it does not add power. It performs the scavenging.) Behind that the accessories. Injection could be as simple or sophisticated as you like, mechanical pumps and injectors or common rail injection. Most components can be made on a simple lathe. Cases can use sheet metal and the whole thing furnace brazed; no castings. Liquid cooled, since the shape does not lend itself to air-cooling.
    The advantages of the two stroke, opposed piston engine can be seen everywhere, including some modern iterations. The old problem of burnt out exhaust pistons of the Jumo can be solved with carbon pistons. In its simplest form, it needs no electrics. You could even go so far as fit a spring starter and don't even need a starter motor. For more power and efficiency, a turbo could be added - it's' almost a no brainer for a diesel, but it's optional.

    I once managed to get hold of an interesting diesel engine analysis/simulation program from a Russian university that was amazingly sophisticated, but very user friendly. I sat up many,may nights tweaking things like port angles and injection profiles and whatnot. It was addictive. It also proved to me that this wasn't some hare brained idea with a fatal flaw. I literally read every patent there is on this type of engine (most had at last one fatal flaw), and dug up whatever else there was on the subject (not much). Flight magazine archives had a series of articles on these engines in the 1940s and was as quite hopeful they would materialize. I think their chief merits are only really apparent in the opposed piston type. If you want to get deeper into these, read about Charles Redrup, a British engineer who was the guru of barrel engines. I almost fell off my chair when I read his biography and saw a drawing of his proposed 2000hp aircraft engine - it shared so many details with my own scribblings, it proves that given a certain problem, many people working on it independently will arrive at the same solution.

    Another advantage of this design is how scale-able it is. It should work from 100hp to some insane size.

    Anyway, here's just crude picture of something that illustrates barrel engines. Barrel.PNG
     
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  2. Jul 19, 2019 #142

    imacfii

    imacfii

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    Nope, 4 cylinders wont work. I had conversations with Pat Wilks about this. The barrel enginw is essentially a radial rolled up into a ball, but with the dynacam, you have six piston heads, so as pistonhead #1 is at TDC, so is Piston #7 which inrtroduces a dangerous rocking couple , so much so that the center section started to crack. The solution is to make it 5cy or 7cyl, to eliminate that problem. Port design was another issue.My understand in that Ford Australia bought the design, had major issues with the swash plate staying in balance and shelved the idea. (maybe it was too good). I think the design traces its lineage back to a French (Salmson) engine in the 1910's, which was a 3 cyl single sides engine. Most auto aircondition compressors use this design, and it can be a variable compression engine.
    https://en.wikipedia.org/wiki/Axial_engine
    See also Duke engines. http://www.dukeengines.com/
     
  3. Jul 20, 2019 #143

    rv6ejguy

    rv6ejguy

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    There was a barrel engine designed and built back in the '70s called the K-cycle. Port induction, variable stroke, opposed pistons. I knew the designer who lived down the street in Winnipeg. Worked well, low noise, very good BSFC. Ran out of money after a merger and provincial funding went dry and that was the end of it. I read someone had bought the rights to it 20 years ago but have heard nothing since.

    http://umanitoba.ca/libraries/units/archives/tribune/photographs/display_photo.php?id=2557
     
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  4. Jul 20, 2019 #144

    Hephaestus

    Hephaestus

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  5. Jul 21, 2019 #145

    PTAirco

    PTAirco

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    Nope. My idea is a two stroke, opposed piston barrel engine. It most certainly will work and is in perfect balance as far as firing order goes. Same as a two stroke radial could have even cylinders.
     
  6. Jul 21, 2019 #146

    PTAirco

    PTAirco

    PTAirco

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    You must be thinking of a different engine. The Dynacam had 6 cylinders and a two lobed cam. Everything moved perfectly symmetrically.
     
  7. Jul 21, 2019 #147

    litespeed

    litespeed

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    You can get a factory efi version of both the Hirth F23 and Siminoni engines.

    Cost is more but smooth and lower fuel.

    I would happily go the Hirth at 50hp and very low weight.
     
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  8. Jul 21, 2019 #148

    PTAirco

    PTAirco

    PTAirco

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    Oh, sorry. I get what you mean.
     
  9. Jul 25, 2019 #149

    Terrh

    Terrh

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    I've pondered a few options that I think are interesting and might prove to be useful aircraft engines.
    There's a Europe and Japan only Honda 1.6L diesel that's all aluminum.
    Certain year US market chevy cobalt diesels have this engine as well and are cheap but not abundant.

    The large displacement Superbike engines have always been appealing - and have a built in reduction box, though I'm not sure what you'd have to do to make it handle thrust loading, maybe eliminate it entirely and go with a regular style PSRU.

    For big power - the big cube LS/LT engines are unbeatable. And they will run all day at 4000+ RPM without a second thought, there are hundreds of thousands of short geared delivery vans around the country proving that point every second.

    For medium power - There's now a V6 5th gen smallblock that's based on the 5th gen engines, everything you love about the LS but 3/4 of the size, weight and displacement.

    I've always loved rotaries - and for certain mission profiles they are hard to top.

    No need for two plugs per cylinder in any car based engine that's modern and EFI - Most iridum plugs will outlast your car.
     
  10. Jul 25, 2019 #150

    Terrh

    Terrh

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    I have - and I agree with you on the most part - but there are a few reasons here that I think you haven't considered:

    Those old engines were attached to transmissions that didn't have overdrive, and that had short gears.

    If you drive a modern car that's designed similarly (large engine, short rear end gear) and drive it in 4th (or whatever the highest non-overdrive gear is) they behave the same way. I drive a 2007 Corvette which has an absolutely amazingly flexible engine (LS7) for being all "old tech" on the surface - it's just OHV, one camshaft for the whole engine, but it will pull in 4th gear from a stop if you don't mind being a bit abusive to the clutch, and without shifting it will continue all the way to ~170MPH at 7200 RPM.

    I've got another car that, while far slower, will equally pull from idle all the way to redline in 4th gear despite only having a 650CC turbo engine. It does this by having short gearing and a (really small) turbocharger.

    Interestingly, despite being entirely different engines, with entirely different design goals, and one having more than 10X the displacement and nearly 10X the power output, V8 vs i3, OHV vs OHC, N/A vs Turbo, the torque curve on both engines is a very similar shape past 1500 RPM.
     

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