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Thread: What is a semidiesel?

  1. #1
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    Default What is a semidiesel?

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  2. #2
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    Default Re: What is a semidiesel?

    An engine the runs on Diesel fuel but instead of the heat from compression alone it uses an independent ignition source.
    Works good...


  3. #3
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    Default Re: What is a semidiesel?

    Usually taken to mean a hot bulb engine; you start it with a blowlamp and then swing the flywheel. I used to know a Baltic ketch that had one but alas it was the death of her some years later. They don’t start in a hurry.
    IMAGINES VEL NON FUERINT

  4. #4
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    Default Re: What is a semidiesel?

    usually they have a more mellow sound than the boat above.
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  5. #5
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    Default Re: What is a semidiesel?

    When I was a kid many years ago, we had an International crawler tractor. It was referred to as a semi diesel. Unlike the Caterpillars that started with the help of a pony engine, now an electric starter, this International started on gasoline and after the engine ran long enough to to warm up, you moved the throttle to switch it over to diesel.
    it had some kind of compression release which allowed it to be started electrically on gas, then when you threw the throttle, it must have closed the compression release. It ran, sounded, smelled and performed like a true diesel.

  6. #6
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    Default Re: What is a semidiesel?

    Quote Originally Posted by horsepen View Post
    When I was a kid many years ago, we had an International crawler tractor. It was referred to as a semi diesel. Unlike the Caterpillars that started with the help of a pony engine, now an electric starter, this International started on gasoline and after the engine ran long enough to to warm up, you moved the throttle to switch it over to diesel.
    it had some kind of compression release which allowed it to be started electrically on gas, then when you threw the throttle, it must have closed the compression release. It ran, sounded, smelled and performed like a true diesel.
    Those were pretty sweet engines, one side of the engine had a carburetor and ignition system the other side had a high pressure injection pump. The compression release was an extra cam lobe and a wee valve in the head that when opened it would allow the engine to have just enough compression to run as a gas engine. When the engine warmed up a bit, you threw the lever and closed the compression valve it also shut off the gasoline supply and switched open the high pressure pump. It was a direct injected "regular" diesel then. (In a pinch you could hook the starter up to 24 volts and start it as diesel)
    Complicated things with the best and the worst of both worlds they were remarkably reliable and overbuilt. The "day tank" for gasoline held about a half gallon, and was always empty.

  7. #7
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    Default Re: What is a semidiesel?

    The Kelvin K series engines, much loved by Scottish fishermen, were like that - start on petrol, warm up, change the compression and run as diesel.
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  8. #8
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    Default Re: What is a semidiesel?

    There was a relatively brief fad for petrol (gas)/paraffin(kero) tractors in the UK - start on petrol and, once the carburettor had reached operating temperature, switch over to the much cheaper paraffin.

    Heir to many many ills - and operator errors.
    I'd much rather lay in my bunk all freakin day lookin at Youtube videos .

  9. #9
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    Default Re: What is a semidiesel?

    Quote Originally Posted by P.I. Stazzer-Newt View Post
    There was a relatively brief fad for petrol (gas)/paraffin(kero) tractors in the UK - start on petrol and, once the carburettor had reached operating temperature, switch over to the much cheaper paraffin.

    Heir to many many ills - and operator errors.
    That is how the Kelvins of the 1920s worked. My boat was first fitted with a 6/7. 6HP on paraffin, 7hp on petrol.
    A company in the '50s were marinising car engines by fitting an inlet manifold around the exhaust manifold to vaporize the kerosene. They welded up some of the cogs in the gear box to give forward and reverse at about the same reduction ratio.
    It really is quite difficult to build an ugly wooden boat.

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  10. #10
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    Default Re: What is a semidiesel?

    The Kelvin E and F series were petrol paraffin but the Ks were petrol start diesels. Not in fact semi diesels as they were not hot bulb engines - you dropped a decompressor to bring the engine from its quite low petrol compression ratio to the diesel compression ratio.

    I fancy that the odd Kelvin E, F and K may yet live on the inland waterways of Britain.
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  11. #11
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    Default Re: What is a semidiesel?

    FWIW, my 1939 John Deere B and many other tractors from that period had 2 fuel tanks: a little one for gasoline, and the main one for "Distillate"; which was a cruder fuel akin to a light kerosene.

    Distillate (motor fuel) - Wikipedia

    You wouldn't be able to start the tractor on the distillate; you switched to gasoline before shutting down so the carb bowl would contain only that for the next start. Then, after you started and warmed it up on gasoline, you switched over to the much cheaper distillate for the field-work.

    Not dieseling though -- the spark system was required.

    tractor and caboose.jpg

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