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Thread: 4-Stroke Snowmobile Engines

  1. #1
    Registered User mstull's Avatar
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    4-Stroke Snowmobile Engines

    I researched 4-stroke snowmobile engines. 4-strokes are fairly new for snowmobiles, with gradually increasing acceptance. But there aren't many choices yet, and they are too heavy and powerful for my U/L. Unfortunately, all the 4-stroke snowmobile engines are water cooled, and are very high performance (expensive and complex).

    Some of the snowmobile manufacturers have made or still make 4-stroke sleds, with the smallest engines in the 500 cc to 660 cc range, twins or triples. But these are fire breathing, fuel injected, dual overhead cam screamers, in the 48 to 80 Hp range, similar to sport motorcycle engines.

    Arctic Cat had a 53 Hp, 3 cylinder engine, several years ago on a model called 4-stroke Touring. Polaris made the Frontier with a 48 Hp twin. Yamaha makes a 499cc, 80 Hp twin, called the Phazer.

    They also have 1,000+ cc models with over 100 Hp.

    Due to increasing EPA regulation, 4-stroke sleds are expected to become more common. So there should be more choices soon. One struggling, upstart company is supposed to come out with a 300 cc, 22 Hp, low tech single very soon.
    Attached Thumbnails Attached Thumbnails 4-Stroke Snowmobile Engines-arcticcat.jpg   4-Stroke Snowmobile Engines-polaris.jpg   4-Stroke Snowmobile Engines-yamahaphazer.jpg  

    Mark E. Stull
    mstull@wtxs.net

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    Registered User pwood66889's Avatar
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    Re: 4-Stroke Snowmobile Engines

    Thanks for the update, Mark.
    One reason for 2-cyc's being popular with sno-mobilers is that the have no oil to get thick in the crank case at cold temperatures. Like SE Alabama tonight!
    Keep us posted.
    Percy

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    Registered User BBerson's Avatar
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    Re: 4-Stroke Snowmobile Engines

    What is really needed is a long stroke and slow turning engine designed to turn a prop.
    Unfortunately, most other vehicles such as snowmobiles and motorcycles need a gear reduction in all cases so they are designed for a gear reduction.

    I can't think of any slow turning and light engines other than aviation.
    We need a 30- 40hp engine that is purpose designed.

    Like this:http://www.ultralightnews.com/sunfun99/amtec.html
    Last edited by BBerson; February 27th, 2010 at 12:18 PM. Reason: paste website

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    Re: 4-Stroke Snowmobile Engines

    I completely agree BB, we want long stroke, low revving and designed just for planes not mowers etc.

    The Buddy twin looks good, with a few mods it could be great.

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    Re: 4-Stroke Snowmobile Engines

    Mark, Have you tried looking around for a scooter engine? They come in all sorts of sizes from 50-600cc. They have large bearings on the output shaft to hang a CVT on. And, you can find them in all sorts of configurations like 2 and 4 stroke and air or water cooled. A 200-250cc engine might suite your needs if the snowmobile engines are too powerful. They are, pretty much, just littler snowmobile engines and ,if you could find a Euro connection, very common. Jialing makes a bunch of good quality ones in China so it may be possible to find a very inexpensive one too.

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    Registered User mstull's Avatar
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    Re: 4-Stroke Snowmobile Engines

    Thanks John,

    I spent some time researching scooter engines. All the ones I could find, the engine cases included a long extension for the drive connection to the rear wheel. I'm willing to design my next plane around a suitable engine. I joined the 4-stroke engines Yahoo group. They're mostly trying to convert industrial engines that are too heavy and too low powered.

    I like the long stroke idea for direct drive. If I'm going to have to have a reduction drive, a shorter stroke, higher revving engine might have a better power to weight ratio.
    Mark E. Stull
    mstull@wtxs.net

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    Registered User pwood66889's Avatar
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    Re: 4-Stroke Snowmobile Engines

    Always nice to see your thinking, Mark, and am looking forward to your 4-stroke design.
    Yeah, the industrials are overweight and underpowered. Like Wood's Rule of Metal Motors: "If it is made of metal, it is too heavy... :-)" But I do believe they have possibilities in LSA if not ultralights.
    Percy in SE Bama

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    Registered User Dan Thomas's Avatar
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    Re: 4-Stroke Snowmobile Engines

    Quote Originally Posted by BBerson View Post
    What is really needed is a long stroke and slow turning engine designed to turn a prop.
    Unfortunately, most other vehicles such as snowmobiles and motorcycles need a gear reduction in all cases so they are designed for a gear reduction.

    I can't think of any slow turning and light engines other than aviation.
    We need a 30- 40hp engine that is purpose designed.

    Like this:Amtec Buddy Twin aircraft engine, Amtec Buddy Twin 4 stroke 2 cylinder aircraft engine.

    That sure looks like an aircraft engine from the 1920s. Exposed valve train, manual spark advance, and all. Dirt plays hob with any open machinery; too bad he doesn't have rocker boxes. It wouldn't add much weight at all, maybe none once the "sponge-filter" valve oiling system was taken off it.

    Here's a 1918 Lawrence aircraft engine:





    Wright J-5 from the 1930s, with manual spark advance visible on the magnetos:


    Dan

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    Registered User BBerson's Avatar
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    Re: 4-Stroke Snowmobile Engines

    I think the Lawrence engine was severely imbalanced with a single throw crank. The popular V-twin configuration is much better using the single throw crankshaft. The V-twin is basically a two cylinder radial engine, I think. (the single throw radial is lowest weight and best for aviation)

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    Registered User mstull's Avatar
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    Re: 4-Stroke Snowmobile Engines

    Thanks Percy. I've learned you can get amazing low speed thrust with low horsepower if you use a lot of reduction to turn a very large prop. For example, I have my present Kawasaki 340 de-rated down to about 23 Hp, yet get spectacular climb performance with a 2.78 reduction and 60" prop.

    I'm wondering how far you can go with more reduction turning larger props and still get significant gains (at U/L speeds)? I would think you'd reach a point where gains would become insignificant. It seems obvious that the gains come from increased prop efficiency. The faster the plane, the less reduction and prop size you'd need to optimize efficiency.

    It would be interesting to see if I could use a very small 4-stroke, like the 22 Hp Bailey PPG engine. But I would need a custom made reduction drive to get the needed reduction. It might be possible to add a secondary reduction onto the stock one. But that would have to be custom made as well.

    I'm amazed nobody makes a 4-stroke U/L engine with about 30 Hp. It would be great if HKS just scaled their engine down to about half its horsepower and 2/3 of its weight, or if Jabaru made a direct drive opposed twin.
    Mark E. Stull
    mstull@wtxs.net

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    Registered User Dan Thomas's Avatar
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    Re: 4-Stroke Snowmobile Engines

    Quote Originally Posted by BBerson View Post
    I think the Lawrence engine was severely imbalanced with a single throw crank. The popular V-twin configuration is much better using the single throw crankshaft. The V-twin is basically a two cylinder radial engine, I think. (the single throw radial is lowest weight and best for aviation)
    Any single-throw crank needs considerable mass balancing of the crankshaft to keep vibration under control. The mass of the pistons must be countered somehow. A V-twin will either shake or have counterbalances. The other problem with a single-throw V-twin is the uneven firing (there are inline four-stroke twins that have the same problem). Listen to a Harley, and hear a single-throw V-twin. Listen to a Virage, and hear a two-throw V-twin; the difference in smoothness is readily apparent. The two-throw still need mass balancing.

    And the problem with mass balancing of a crank is that it adds weight and makes the engine much heavier. The popular opposed engines found in most light aircraft have either no mass balances, or minimal balance weighting on the larger versions. Each rod has its own journal, and opposing pistons move toward each other and away from each other, cancelling each other out. The half-VW is made from a four-banger that needed no balance weighting, but when it was cut in half it needed some mass welded to the crank to control the rocking moments caused by the offset of the opposing pistons. This mass was minimal though, far less than that needed on any single-throw engine.

    in line aero engine animations

    Will show you several animations of inline, V and opposed engines. Note the mass balancing in the inline and V, and the total lack of it in the opposed.

    Dan

  12. #12
    Registered User BBerson's Avatar
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    Re: 4-Stroke Snowmobile Engines

    Dan,
    My Briggs 24hp powered mower is a V-twin. Yes it has large counterweights opposite the single throw. It is the smoothest two cylinder I have ever used. Yes, a four cylinder opposed is smooth as shown in the animation, but we are looking for low cost ideas, that means two cylinders or one cylinder with a counterweight.
    I don't think the Harley can compare with mower engines for vibration.

    The mower engines are bolted solid without rubber mounts. All the industrial engines are V-twin now, I think, including Briggs, Honda, Generac, Kohler, even Kawasaki now has a similar V-twin 4-stroke.

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    Re: 4-Stroke Snowmobile Engines

    A friend of mine has a Burgman 400 engine lying on the shelf. I'll see if he wants to donate it.

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    Registered User Kmccune's Avatar
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    Re: 4-Stroke Snowmobile Engines

    I have traded some emails with a guy flying a Artic Cat 1000cc powered 701 in NW Minnesota. He seems to like it.
    Kevin

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    cmm
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    Re: 4-Stroke Snowmobile Engines

    perhaps the new SAVOIA S40, twin boxer, EFI, 40HP, could be useful. Can be seen at SAVOIA CARS Autoparts - Autoparts and new groups for 2CV6 and 3CV Citroën - Autoparts assembles for Citroën 2CV6

    Carlos

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