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Hit & Miss Gas Engine Discussion Meet collectors of hit and miss engines, ask questions about collecting, restoring and showing antique flywheel engines.

Hit & Miss Gas Engine Discussion

Hercules running Slooow


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  #1  
Old 10-01-2009, 08:55:06 PM
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Smile Hercules running Slooow

I recently did a search here on slow running hercules engines and have a 3 1/2 hp that will run a little under 100 rpm's. This engine will run like this for hours, and seems to run crappy at the rated speed,suggested,I guess my question is how much strain does it really place on this engine and how do you know?Just kind of want some input I know it can not be good for it like idling a engine all day, just kind of curious, http://www.youtube.com/watch?v=wAH1LYesdEk
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Old 10-01-2009, 09:31:21 PM
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Default Re: Hercules running Slooow

The only truely bad effect that slow running can have on one of these old engines is the twisting force that the crankshaft is subject to when the engine almost stops before it fires. I have seen fractured cranks on engines that were run really slow. It doesn't happen very often, but it does happen.

One thing you might want to adjust on your engine is the clearance between the detent finger and the catch block. This should be around 1/32" when the pushrod is on the highest point of the cam lobe. If 1/32" is too tight, just make it as tight as you possibly can and still have it function properly. Sometimes worn engines can't tolerate the tight clearance. Making this adjustment will drastically reduce the noise of the cam banging the pushrod when the engine is "missing".
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Old 10-01-2009, 09:50:49 PM
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Default Re: Hercules running Slooow

If your running slow, you want your timing retarded to put less stress on the crankshaft. I think throttle goevened engines that run slow put less stress then hit & miss engines do.
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Old 10-01-2009, 11:16:09 PM
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Default Re: Hercules running Slooow

Vernon is right. It will reduce the stress on the crank a lot to retard the timing to about 15° AFTER top dead center. It is my theory that the extra stress on the crankshaft isn't from the acceleration after firing, but a LACK of gyroscopic stabilization from the flywheels. When they are going fast, the flywheels act like giant gyroscopes that reduce how much the crankshaft bends from cylinder pressure. When running my larger hit/miss governed engines slowly, the distance between the back edge of the flywheels increases visibly when ignition occurs. This does not happen when they are running faster. A piece of metal as inflexible as the crankshaft bending that much will make the crank crack some day. How long it will last, I don't know.
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Old 10-02-2009, 12:00:09 AM
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Default Re: Hercules running Slooow

Is that the one on the video that runs under 100 rpms? In the video it is running 140 rpms. I have a 1 1/2 hp economy which runs 180 to 190 all day long. Dick.
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Old 10-02-2009, 06:10:02 AM
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Default Re: Hercules running Slooow

Yes it's the one in the video, I put a handheld tach on it recently and it will hit about 90 RPM's It has always ran slow since I have owned it.
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Old 10-02-2009, 09:16:00 AM
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Default Re: Hercules running Slooow

Interesting theory you have there Dirtbike. I'll have to give that some further thought. One thing not mentioned is what kind of crankshaft is in your engine. Is it cast, billet, or forged? Is it a large diameter? Some engines have smaller cranks then other engines of same horsepower. Say what you want about Fairbanks Morse, but they are a well made engine. The crankshafts in them are always larger then others of the same HP. With all that said, anything you can do to put less stress on a crankshaft is a good thing.
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Old 10-02-2009, 12:32:47 PM
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Default Re: Hercules running Slooow

J Kocak; The reason I posted I have a hand held tach also which is not very accurate on a HIT AND MISS engine. To check your engine in the video,I counted the cam hits on the pushrod for 30 seconds(35) and multiplied by 4 to get an accurate rpms count 140. Cam is 1/2 the flywheel rpms.Try it sometime. It's a good running engine.Dick
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