Atkinson frustrations

Discussion in 'General Engine Discussion' started by Gordon, Jul 9, 2018.

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  1. Nov 25, 2018 #141

    Gordon

    Gordon

    Gordon

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    I have tried propane in the past but never got good results. I even built a demand regulator but still could not get it to work. It may be time to give it another try. Nothing else seems to work.
     
  2. Nov 25, 2018 #142

    Gordon

    Gordon

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    Ray
    You may have something. I have not really tried pressure after moving back to the right but it seems like that may be true. It would also explain why I am only able to get it to fire with the timing retarded so that it fires after the piston is beyond TDC. I will have to play around with that.
    Gordon
     
    Last edited: Nov 25, 2018
  3. Nov 25, 2018 #143

    Ramoye

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    Hi Dave,

    I have thought some about using propane, but not quite ready to give up on using gasoline.

    Wow Dave, that Parcell and Weed engine you built is beautiful! Great job on it! My engine is starting to look like it has been through WW2. :)

    Thanks for the ideas.

    Ray
     
  4. Nov 25, 2018 #144

    Ramoye

    Ramoye

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    Hi Gordon,

    Another thing that might cause some leakage on the far left, is when it was lapped the edges got a little more material taken off, but I do not recall measurements being that different, plus, it seems the rings are springy enough to compensate for it. I still suspect a side load on the piston at that far left location. I may make another eccentric shaft for the left oscillating arm to move the pivot point down some to test my theory. My engine is really starting to have a lot of adjustments. :)

    Let me know what you find?

    Thanks Gordon.

    Ray
     
  5. Dec 10, 2018 #145

    Ramoye

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    Hi Gordon,

    How are things progressing?

    I changed things up some on my end. I went with a 1 1/2 link arm on the left, and a 1 7/16 link arm on the right. I am still using the eccentric crank pin to adjust the right piston location relative to the left piston (have a gap of around 1/16 inch when the pistons come together).

    I took some time to build a stand for the motor. I also changed to a 12V ignition system, as well as adding a 4 1/2 fan and duct to cool the cylinder. I got two great runs today of 9 minutes each. Not sure why it quit, but it could be due to thermal issues and/or carb. I have no throttle, so the engine was running really hard and fast uncontrolled (increasing the heat output). I am still waiting to receive the new chainsaw carb. The chainsaw carb. has an idle and fast needle for adjustment, as well as a butterfly valve for throttle control. I hope the new carb. will give me better fuel management.

    Ray
     
  6. Dec 11, 2018 #146

    Gordon

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    I have not made much progress. I have been doing some other things, mostly to get a break from this source of frustration. I have made a new intake manifold which provides more support for the valve. I think that the intake valve is hanging up and not closing properly. I have only had a few very short runs where the engine ran on its own. Not sure if a stronger spring would make a difference. I will be getting back to the engine again in a couple of days. I have been working on VFD drives on my lathe, mill and drill press. Another set of frustrations but at least different.
     
  7. Dec 11, 2018 #147

    Ramoye

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    Hi Gordon,

    I know what you mean about the frustration. Been a challenge.

    I had a four and five minute run today, then no luck. Backfiring keeping it from running longer, it seems, not sure why. I think it may be carb. issue. Still waiting for the new carb. At least when it runs it runs hard, too hard, which may be causing a heating problem too.

    You may want to make an eccentric crank link so you can adjust the gap between the cylinders. That seemed to be the key for getting my engine to run. I have a 1/16 gap between cylinders, 1 1/2 left link arm, 1 7/16 right link arm. Left piston sticks out of left end of cylinder about 1/32 (when all the way to the left) and right piston is inside the right end of the cylinder about 1/16 (when all the way to the right). Port locations, pistons, and piston rods are per Gingery's book.

    Ray
     
  8. Dec 12, 2018 #148

    Gordon

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    Ray: I am sure that the problem is poor vaporization of the fuel. I am not sure if it is a result of compression or carburation. I think it is some of both. The fact that you get it running by squirting oil in the cylinder points to a compression problem. The engine seems to be firing way too hard. When it is firing it is burning off fuel in excess of what it can use. Therefore it runs for short periods of time until there is just more fuel in the cylinder than it can burn off in one cycle and once it is flooded it stops running. I have played around with both a vapor carburetor and propane but I have not had much luck with either of them. I have also done some experimenting with different carbs with smaller jets and other throat size. I will be getting back on the engine in a few days.
     
  9. Dec 12, 2018 #149

    Ramoye

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    Gordon,

    I agree with you on poor vaporization of the fuel. Today I adjusted the gap between the pistons wider. It resulted in a 7 minute run at a slower rpm (and richer carb. setting). This rpm seems about right, it was running way too fast before. It still quit after the 7 minute run, which may be attributed to fuel build up (causing flooding). Seems to be a correlation between piston gap and rpm. I may have some piston/cylinder leakage, but it seems to have enough compression to run.

    I will be glad to get the chainsaw carb. in. Curious to see how it will work.

    I ran out of time to experiment with it more today. Will try playing with the piston gap some more tomorrow.

    Thanks Gordon.

    Ray
     
  10. Dec 16, 2018 #150

    Gordon

    Gordon

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    Got around to doing a little more experimenting on the engine yesterday. Still not much progress but I did discover that if I held the intake valve open while turning over with the electric motor the engine fires or backfires every stroke. There seems to be a fine line between a strong enough valve spring and too weak. Too strong and it will not fire and too weak and it spits back through the carburetor. It looks like there may be an ideal match between intake and exhaust valve spring match. I have tried several different carburetors and they all work some times. They seem to be close and then they will not run at all. Then suddenly they seem to work again for a short time.
     
  11. Dec 17, 2018 #151

    Ramoye

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    Gordon,

    Might can try to put shim washers under the spring to incrementally increase the spring force? I also have noticed too weak of a spring causes carb. spitting. Maybe temperature is affecting the spring force (I would hope it is not that sensitive).

    Still waiting on the carb. to come from China. It was only six dollars, but beginning to wish I had spent a little more to get one sooner. I have about done all I can do for now until I get the new carb.

    Thanks Gordon.
    Ray
     
  12. May 28, 2019 #152

    Gordon

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