Snow engine thoughts

Discussion in 'General Engine Discussion' started by Gordon, Dec 24, 2019.

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  1. Dec 24, 2019 #1

    Gordon

    Gordon

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    A couple of years ago I built a Snow engine and had it running fairly well. Recently I have been going back to past builds and trying to get them to run better. The Snow had rather poor compression after setting so I ended up making some new rings and trying some other things. When I put compressed air (20-30 PSI) into the cylinders everything seems to seal and have minimal leaks. When I turn it over by hand it does not seem to generate much compression. I finally came to the conclusion the the garter spring seals were expanding when enough pressure was applied but not sealing at lower pressure. I am thinking about trying string packing similar to what I would use in a steam engine.
     
  2. Dec 24, 2019 #2

    Harry.

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    What about PTFE? Would that be better for compression in low pressure applications ?
     
  3. Dec 24, 2019 #3

    dnalot

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    I built the Snow Engine but never got it to run more than a couple of minutes. Tried a number of different intake manifolds, new rings, new shaft seals. I found two main problems , the intake manifold would get very cold and the shaft seals would quickly start leaking. Finally declared it a failure. But it looks great on the shelf.

    If you get yours to run well I will be very excited.

    Mark T

    Here is a photo for those not familiar with this engine

    Snow Engine.jpg
     
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  4. Dec 24, 2019 #4

    Gordon

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    I have tried playing around with some various seals and I have found that the garter spring seals hold well at 30-40 PSI and leak much worse at 10 PSI. My theory is that by the time the seals start to work the piston is already heading the other direction so you never really build up a compression stroke.
     
  5. Dec 24, 2019 #5

    mfrick

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    Hello to All Merry Christmas and have a Happy New Year.

    So several years ago I built the Snow Engine, I doubled it in size so the bore is 2 inch, the piston rod is 5/8 chromed 1045 material cylinders are cast iron with steel housing the fly wheel came off an Ideal hit and miss engine.
    I had tons of trouble with the seals and I changed to Chevron Packing made of Teflon put three rings in each head and compressed with the plate covering the water chamber, since doing this I have had great compression and the engine runs fairly well. I purchased the seals from McMaster Carr.
     

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  6. Dec 24, 2019 #6

    mfrick

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    So I didn't get all my photo's loaded of the Snow Engine so I will try again.

    Mike
     

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  7. Dec 24, 2019 #7

    Gordon

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    Thanks. That looks like it could actually work. The stem packing string does not work.
     
  8. Dec 25, 2019 #8

    Rustkolector

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    Gordon,
    I am presently rebuilding my Snow engine also. Previously I had made a number of changes to my engine and had it running quite well and slowly. Combustion had improved to the point where the exhaust was dry. It was burning the oil in the fuel to the point where it was creating blue smoke. To control the smoke level I was trying different oils and began cutting back the oil in the fuel. Unfortunately, I went too far and seized it up scoring the rings and cylinders. So I have refinished the cylinders .003" larger with new pistons and a few other changes. It is just about finished but I still have a few issues to resolve. That said, I have never had any problems with the original Buna N seals leaking and my engine had a fair number of hours on it. The first thought I had is that you might have your seals installed backwards. When installed as designed, with the lips facing the combustion chamber, the lips should grip the shaft tighter as cylinder pressure increases.

    I have never built a good compression tester, but my engine always had good flywheel bounce back when hand spinning it. One thing I sadly discovered when I completely disassembled my engine was that it had a lot of cylinder and piston rod corrosion. 12L14 is a great cylinder material on a 4 stroke engine, but only if properly maintained, especially immediately after stopping the engine. My drill rod piston shafts were both badly pitted over a large area, BUT the original seals were not leaking when I seized it.
    Jeff
     
  9. Dec 25, 2019 #9

    Gordon

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    I do have the seals installed correctly. When I put compressed air in the cylinder I do not have any leaks except at the rod seal. The lower the pressure the more air leakage. Mike suggested V ring seals from McMaster and that looks like a possibility but it will require a new head to accommodate the larger 11/16 OD seal. I am not getting any appreciable bounce back when I turn it over by hand. I have an adapter which I can put in the spark plug hole with a pressure gauge. The gauge bounces up to about 10 PSI and immediately drops back to 0. The rings are sealing because when I put pressure in the cylinder it does not bleed through to the other cylinder on the opposing side. Obviously I am missing something.
     
  10. Dec 25, 2019 #10

    Gordon

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    I just had a thought about the seals. I wonder if the seal is being compressed in the retaining cage. In order to seal air must get behind the spring loaded lip to push it out against the rod. If it is compressed longitudinally it is sealing the face and air cannot get to the spring area to expand the seal. Counterboring or countersinking should answer that. Probably worth a try.
     
  11. Dec 25, 2019 #11

    Rustkolector

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    Good idea Gordon. My seals (no garter spring) measure .122-.124" thick and adding a head gasket space of about .012" would leave a seal pocket depth exposed to compression and combustion pressures of about .017" between the seal and rear of the bushing (.470 - .340 - .125 + .012"). This would vary depending on your seal thickness and gasket material. I use Teflon gaskets which don't compress much.

    One more little bothersome item I found when I disassembled my engine was that the single piece head gasket area directly exposed to the coolant had bulged into the head water jacket space greatly reducing water jacket volume (estimated 50%), and likely coolant flow. This happens with fiber and Teflon gasket materials. I use antifreeze to prevent water jacket corrosion which might have contributed to this gasket deformation. I have changed to a two piece head gasket leaving the entire water jacket space open.
    Jeff
     
  12. Dec 25, 2019 #12

    Gordon

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    I have not tried O rings. I will try that next. I tried plumbing string packing and that did not work. It would not stay in the recess long enough to assemble it.
     
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  13. Dec 26, 2019 #13

    gld

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    Gordon
    A few years ago I rebuilt my snow using vitron o rings on the Pistons. In the process I install stainless steel sleeves, and stainless steel piston rods. The O-rings will give better compression (no leakage through a gap) less friction which equates to easier starting and cooler running.


    That's a very nice looking engine you have. I should think with the increased bore and flywheel weight, that engine should be able to run very slow. When you get it running, post a video, and tell use how slow it will go.
    Gary

    BTW where are you located?
     
  14. Dec 26, 2019 #14

    mfrick

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    I'm located in Port Angles WA. I haven't had the Snow Engine running since August, need to get it out and crank it up after the holidays I will try to find some time to crank it up and get some video to post. Just installed a new lathe so now I need to put my shop back together, then I will have some spar time.

    Mike
     
  15. Dec 27, 2019 #15

    Gordon

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    As I am doing more experimenting it appears that a lot of my leakage may be around the piston rod at the piston which allows the pressure to bleed from one cylinder to another. For instance when cylinder #1 is under pressure it bleeds into cylinder #2 and when cylinder #2 is under pressure it bleeds into cylinder #1. I found this by pressurizing #1 and if there is no spark plug in #2 I have air coming out of the open spark plug hole. I am presently tearing things apart and putting epoxy around the piston rod in the piston. This is not obvious until the opposing spark plug is removed.
     
  16. Dec 28, 2019 #16

    mfrick

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    A good way to stop the leakage around piston rod is to use some Loctite I used Red on mine and zero leakage if you need to disassemble just heat piston up with a torch.

    Mike
     
  17. Dec 28, 2019 #17

    Rustkolector

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    Gordon,
    How did you determine the air leak past the piston was from the piston rod clearance and not the piston rings?
    Jeff
     
  18. Dec 28, 2019 #18

    Gordon

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    I took the head off from #4 cylinder and put air pressure into #3.
     
  19. Jan 4, 2020 #19

    Gordon

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    This thing continues to baffle me. I seem to have the leaks fixed but now the problem is that it fires #3 & #4 cylinders but not #1 & #2. I have checked valve timing and ignition timing and all four cylinders seem to have the same timing. It fires #3 & #4 and it will continue to kind of run for 10-15 seconds but with #1 & #2 resistance it just bogs down and quits. It only seems to fire when the engine is almost flooded with raw fuel actually coming out of 3&4 but not out of 1&2. I have tried a couple of different carburetors and even a different manifold but nothing seems to make any difference.

    I guess that it is time to quit for the weekend.
     
  20. Jan 5, 2020 #20

    Shopgeezer

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    Sounds like your fuel is not being atomized by the carb. I wonder about pre-heating. We have engines on the farm that benefit greatly from a touch with the tiger torch. The Deutz diesels won’t start without it.
     

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