Hit n Miss Engine Tune Up

Discussion in 'A Work In Progress' started by cfellows, Feb 2, 2008.

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  1. Feb 2, 2008 #1

    cfellows

    cfellows

    cfellows

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    This, strictly speaking isn't a new project. I started this Hit n Miss engine in the mid 90's and finally got it running in the early 2000's. It started out as a copy of Phil Duclose's Odds n Ends engine, but I departed pretty radically from his design on the cylinder assembly, building it up out of a cast iron sleeve, a piece of thin walled steel tubing, adding a head and valves of my own design. The engine has never run very satisfactorily, starting hard, running too fast, and not wanting to run at a nice, slow pace.

    Over the past few years I've done things which have helped. I added more weight to the flywheels by pressing a quarter inch thick steel ring cut from pipe over the existing flywheel rims. I've also modified the carburetor, reducing the internal diameter from 1/4" down to 3/16". Finally, I removed several turns from the intake valve spring so it will just barely hold the valve closed between intake strokes.

    This weekend, I'm going to shorten the connecting rod, lowering the compression ratio. And, I'm going to make a new piston which fits just a little looser than the existing piston. If anyone has any other suggestions, I would appreciate any input. I will take a video on Sunday after I've completed the remaining work.

    [​IMG]
     
  2. Feb 4, 2008 #2

    cfellows

    cfellows

    cfellows

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    I finished up the mods late this afternoon. I made a new aluminum piston, about .002" undersize and, instead of a cast iron ring, I used on o-ring. I picked it up at the hardward store, so it's probably not the best material for the job. However, the engine now runs great, hits hard and runs pretty slow. I reduced the compression ration a tad, although I don't really know how much.

    The engine stops several times in the video because it's almost out of fuel. It's running on Coleman fuel with a squirt or two of WD400 added for lubrication.

    [ame=http://www.youtube.com/watch?v=5rLSkLv_SsM]http://www.youtube.com/watch?v=5rLSkLv_SsM[/ame]

    Chuck
     
  3. Feb 4, 2008 #3

    deere_x475guy

    deere_x475guy

    deere_x475guy

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    Chuck I like the way it looks and sounds. What are you using for ignition and how did you come up with a size for the o-rings.

    I am curious about the ignition because I am thinking about going with electronic on my Edwards I am building.

    Also I am a little concerned about the intake valve operation and might decide to operate it off a cam. Of course I guess it won't be and Edwards then if I do that.
     
  4. Feb 4, 2008 #4

    Powder keg

    Powder keg

    Powder keg

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    Nice engine Chuck!!! I'd like to build a hit and miss someday. In the summer there are a couple local engine meets and I really enjoy watching them run.

    Thanks for sharing, Wes
     
  5. Feb 4, 2008 #5

    chuck foster

    chuck foster

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    nice engine chuck 8)
    i have one of tom stuarts 25 h.p. fairbanks morse models and the guy that built it said it ran way to fast.............well i turned it over and it had way too much compresion.
    i pulled the cylinder head off and with the piston at top dead center it was about 0.080" way from the head :eek:
    i shortend the con rod about 0.800" and now the engine runs slow and it will run all day with out water in the cooler. it still hits hard and starts easy.

    hows the three cylinder engine coming along? ;)

    chuck foster
     
  6. Feb 4, 2008 #6

    cfellows

    cfellows

    cfellows

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    The ignition uses points that run off the crankshaft and a motorcycle coil I picked up used. It's powered with a 9 volt rechargeable RC battery pack I bought on eBay. When I first built the engine, I tried running it on 6 volts. I absolutely could not get it to run, although the spark plug would arc when I took it out of the engine. I guess it just wasn't quite enough to arc under compression. As soon as I switched to the higher voltage battery, it started right up.

    The bore on the engine is 1.080". Wasn't designed that way, just kind of wound up there. So, bought a 1 1/16" diameter o-ring that was 1/16" thick. I turned the grove in the piston 1/16" deep and about .075" wide. The piston slides freely in the cylinder, but the o-ring action gives it great compression.

    Chuck
     
  7. Feb 4, 2008 #7

    cfellows

    cfellows

    cfellows

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    They are fun little engines, but this one was sure a learning experience for me. I started building it in the mid 90's and first got it completed to the point of running about 9 years ago. Since then, I've built 3 different crankshafts, 4 different pistons, modified the flywheels, and reworked the carb several times. I've come real close to throwing it through a wall a couple of times. Luckily, reason prevailed when I considered that the missus would almost certainly notice and, well, you know how that could go!

    When you get everything just right, they will run and run and run. But there are are half a dozen or more things that will keep them from running. The governor tends to stick once in awhile, causing it to die. Once I fix that, it should be completely done, once and for all!

    Chuck
     
  8. Feb 4, 2008 #8

    cfellows

    cfellows

    cfellows

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    Haven't started on the 3 cylinder air engine yet. I also haven't gotten much done on my 2 cylinder IC engine. I'm still noodling over what to do for the carburetor, and I've been sicker than a dog for the past week. This weekend was the first time I've been in the shop for over a week.

    Chuck
     
  9. Feb 4, 2008 #9

    raym 11

    raym 11

    raym 11

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    I have a similar engine 1.062 bore. sounds like we have been down the same path to make run. It seems o help by taking the exhaust out to a larger size. A little bit helps and its easy to remove the tail pipe for a test run.

    raym
     

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