Snow engine thoughts

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

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  1. Jan 5, 2020 #21

    dnalot

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    I decided the Snow engine is a failed design and not worth wasting my time on. Getting over it and moving on. Still looks nice on the shelf but will probably move it as the working engines are offended by sharing the shelf with a looser.

    Mark T
     
  2. Jan 6, 2020 #22

    Gordon

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    I agree that the carburetor is likely the problem. I am wondering about putting two carburetors on it. One carburetor on #1/#2 and another on #3/#4. I think that the long intake manifold is a problem. Fuel is atomized at the carburetor but reforms to a liquid before it reaches the cylinders. The two carburetors would not have to matched exactly in order to run since the cylinders fire in sequence.
     
  3. Jan 6, 2020 #23

    Gordon

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    I seem to be drawn to failed designs. I worked for way too long on my Atkinson Differential before I decided that it was a very marginal design and it was time to stop beating a dead horse. Unfortunately working full size engines do not always scale down successfully. It is true that for most of our model engines we just want them to run successfully but not actually power anything so we accept just looking and sounding nice.
     
  4. Jan 6, 2020 #24

    Rustkolector

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    Gordon,

    I posted a while ago here about my problems with the Snow and in particular an issue I took with the intake manifold design. It quickly gets very cold upon engine start. Many engines would run a short time and then stop. Mine started doing this later on, but not initially. The cold impedes good fuel distribution and likely causes fuel and moisture condensation as well. I found a significant improvement by building a flat log type intake manifold. It proved even better when I jacketed this manifold and forced return coolant through it.

    Last year at this time my Snow was running very well. It ran without stopping at 400 RPM as long as it was getting fuel, and combustion had improved to the point where the gasoline/oil mix was burning with a visible blue color. The only drawback was increased carbon inside the engine. The jacketed intake manifold absorbed significant engine heat allowing long engine runs with only a small coolant reservoir system. I was very pleased with the engine. However, the pleasure did not last long. I soon discovered significant cylinder and piston rod corrosion. I blame my own careless operation and ignorance of 12L14 cylinder material for this problem. Short runs create significant moisture inside the cylinders. You cannot let it remain on confined 12L14 surfaces after shutdown even a minute, especially if the engine is burning the fuel completely. If the exhaust is slobbering wet all the time this condition is probably not as bad. I believe this combustion created moisture can cleared by spinning the engine over (fuel ON, ignition OFF) immediately after every engine shutdown.

    So far, I attribute the improved running of my Snow engine mostly to two specific improvements. First the coolant heated jacketed log type intake manifold. It keeps the manifold very warm to the touch right up to the bottom of the carb. I used a small 3 mm throat RC carb. The second improvement was a different cam lobe profile. The cam was changed to a 46⁰ profile. This allowed for ~220⁰+ exhaust duration. However, the single cam lobe Snow feature required increasing the intake valve lash significantly to get a more reasonable 190⁰ duration on the intake valve. For what its worth, I once ran across an old engine book from 1906 on Google books that indicated Snow (Worthington) had recently (1906) improved the poor light load operation of their tandem double acting gas engines. Unfortunately, the book did not say just how they did it.

    In my rebuild I am reusing the cleaned up original cylinders (with better maintenance) and replacing the piston rods with stainless steel. The new piston set screws will be 6-32 half dog type. I also have replaced the piston rod connector with a split type and cutting the piston rod connector reliefs .032” deep to allow use of a temporary Delrin clip type insert to protect the oil seal during assembly.
    Jeff
     
  5. Jan 6, 2020 #25

    oldengineguy

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    Hello All: Re Snow Engine After seeing the real thing at Coolspring , I knew I'd have to build this engine if only for show maybe not a runner. I saw one running at NAMES 2019 that had different manifolding and a radiator ,but can't remember the fellows name. I have had moderate success with other engines but compression loss is always a concern. After reading this thread it seems there may be hope for a runner . I like the heated manifold idea and Loctite on the piston rod/ piston. I'm a long way from that point yet but am only a few parts away from a stack of cylinders and crank assembly which is the point where I find out whether a piston rod will slide or whether I have taken on more than I am able to do with my machines and skills. Regards Colin
     
  6. Jan 7, 2020 #26

    mfrick

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    So When I built my Snow engine I used a spit coupler threaded with LH/RH threads this allowed to adjust the stroke of each piston, the nut has two allen head screws to lock once the stroke is set. The piston rods are 1045 chrome hydraulic piston rod material. Cylinder liners are cast iron with alu pistons. I did change the intake manifold making it a straight manifold and this did improve the running of the engine. Engine runs great for 8 to 10 hours then it carbons up due to the fact that I used mixed gas. I need to play with the mixture and see if I can cut down on the amount of oil used.

    Mike
     
  7. Jan 7, 2020 #27

    Gordon

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    Obviously I am missing something. I cannot get my engine to run on it's own for more than a few seconds. I think the compression is the problem but I certainly cannot isolate the problem. I have a fitting which permits me to put compressed air into the cylinder through the spark plug hole and I can pressurize it to 30-40 psi and there are no or at least very minimal leaks. I can put a pressure gauge in the spark plug hole and turn the engine over by hand and the gauge jumps up to about 10 psi but immediately drops to 0. If I turn it over with my drill it jumps up to about 40 psi but drops right back to 0. On the other hand turning it over by hand I do not feel any appreciable bounce back. If I put my finger over the spark plug hole and turn it over by hand I can feel some pressure on the compression stroke and it seems to hold vacuum for a couple of seconds on the intake stroke. I had the engine running a couple of years ago until I decided to "improve" it recently.

    I have 12L14 cylinder liner, aluminum pistons and drill rod connecting rod but I have not noticed any rusting or corrosion. I use Coleman fuel with a shot of Marvel Mystery oil which is the same as I use in all of my engines.
     
  8. Jan 8, 2020 #28

    mfrick

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    Hi Jeff
    Could you post a drawing of your new cam profile.

    Mike
     
  9. Jan 8, 2020 #29

    Rustkolector

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    Gordon,

    If you don’t have a pressure gauge that holds the highest reading, it is normal to see the compression pressure or vacuum bleed off rather quickly through the ring gaps. No flywheel bounce back is puzzling unless your engine hasn’t been run much. If you crank your engine with a portable drill driver and you can hear the compression strokes in the sound of the drill motor I would say the problem is not compression.

    Have you documented your valve timing? I have gathered some relative valve timing information on one currently running 400 hp Snow engine and it is pretty strange. I have told two other builders about the 46⁰ cam profile and this single change produced a running engine in both cases (see link below). I don’t have a drawing of this cam lobe, but see item #46 in the original drawings and reproduce it with a 46⁰ angle instead of the original 58⁰ angle. It produces longer duration. Install the cams and then adjust the exhaust valve lash at about .002-.003”” and then, using a dial indicator on the valve spring retainer, set the exhaust valve opening (EO) to about 40-45⁰ BBDC and exhaust close (EC) at TDC. Then adjust (by opening) intake valve lash to get IO at about 5⁰ ATDC and IC at about 10-15⁰ ABDC. It should run better provided everything else is good. This is not an orthodox valve adjustment means, but with only one cam lobe you have to improvise. The wide valve lash hasn’t presented and issues or wear on my engine.

    Jeff

    http://www.modelenginemaker.com/index.php/topic,4060.630.html (go to reply 632)
     
    Last edited: Jan 8, 2020
  10. Jan 8, 2020 #30

    Gordon

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    Thanks. I have not been watching valve timing too closely. I will try your settings to see what happens. Last night just before I quit I noticed that at least on #4 I was getting a puff back through the intake which is obviously exhausting the intake manifold just prior to the intake stroke so at least part of the intake stroke is used to refill the manifold. This tells me that I am opening the intake valve BTDC while it is still in the exhaust cycle. I had run across your 46° cam on another post and I have made 46° cams. Generally valve timing is not as critical as it is on this engine but as you say you are using the same cam for both intake and exhaust so things become a compromise.

    A continuing problem is the set screws come loose as the engine runs. I like the idea of at least making the rod coupling with RH and LH threads. I have already made the set screws in the cams 6-32 instead of 2-56. Trying to tighten a 2-56 with a .050 hex just does not provide enough torque to hold. I have also put a coupling in the valve shaft which makes the adjustment of the relationship between ignition and valve timing easier.

    Hopefully I will get time soon to get back and try some things. My wife seems to think that replacing the GFI receptacle in her bathroom just because it trips even with no load is more important than working in the shop. Sometimes wives have no concept of priorities.

    Gordon
     
  11. Jan 8, 2020 #31

    awake

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    Newbie here - can someone help me to understand what it means to talk about a 58° angle or 46° angle (or whatever angle) cam? I'm particularly confused because my first thought is that this angle is the included angle of the flanks of the cam (if that's even the right word - the flats or slightly rounded part that leads up to the lobe). But if that is the case, wouldn't a smaller angle result in less duration rather than more? I think I am not understanding correctly ... help! :)
     
  12. Jan 8, 2020 #32

    Gordon

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    per my as I go along sketches
     

    Attached Files:

  13. Jan 8, 2020 #33

    Rustkolector

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    Gordon,

    Set screws are a problem indeed. I ran across a this set screw tightening recommendation: To tighten new, standard, alloy, cup point set screws, install an allen wrench with the short end in the socket, long end in your hand, and tighten until the wrench bends or twists about 30° (1 hour on a clock face). Then the set screw is as tight as it should be. The key word is “new”. Don’t put used set screws in a final assembly, and use black alloy and not SS. Always dress up the wrench end if any rounding apperars. I am using half dog point set screws on my pistons. In theory they should help. I had considerable trouble with the connector set screws loosening, but none of the others.


    Mike’s idea on the piston rod connector is a very good one. Piston position is difficult to equalize, but can be done close enough. I was more concerned with damage to shaft seals during assembly. I chose the split type I saw on another Snow engine builders engine. I was able to make a temporary and simple split clip Delrin bushing that snaps in the shaft connector relief. This allows the shaft connector relief to smoothly glide past the seal with no forcing.

    Jeff


    http://www.safetysocket.com/sites/www.safetysocket.com/files/parts/bd/Products/setscrewtorque.htm
     
  14. Jan 8, 2020 #34

    mfrick

    mfrick

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    Hello Jeff
    Thanks for the SnowCam drawing. I will try this out on my engine and let you know how it works out.

    Mike
     
  15. Jan 8, 2020 #35

    awake

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    Gordon, that sketch is very helpful. I realize now that I was "defining" the angle correctly ... I just wasn't processing the results correctly in my head.

    I should have realized - the one time I have attempted to cut a cam thus far, the same sort of confusion caused me to cut it wrong. I was thinking it was simple - a 62.5° degree cam was called for, so I would need to make cuts while rotating the dividing head by (360-62.5) = 297.5°. Ah, no. I did finally get it right, but I am still not quite sure how to turn it into a formula ...
     
  16. Jan 8, 2020 #36

    Gordon

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    I have the engine somewhat running, at least I did until the rod coupling came loose again. There is one thing which does not seem right or at least I do not understand it on the valve timing. I have flats milled on the valve connector rod at 90°. That is if #1=0°, #2=90°, #3=180°, #4=270°. It would seem like once one cylinder is set the others should be also set but there seems to be quite a bit of variation from one cylinder to the next. If #1 is set for intake close at 10-15 ABDC #2 closes at 10 BTDC. I have tried to compensate by adjusting for more or less valve lash gap but that is not giving me 190° open on each cylinder. Should not the valves be at a fixed 90° position? Any idea what is causing the variation?
    Gordon
     
  17. Jan 9, 2020 #37

    Rustkolector

    Rustkolector

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    Gordon,
    Sorry, no idea of the cause of the variation. However, the camshaft flats at 90⁰ sounds like a good idea and probably would work on a shorter larger diameter camshaft, but I found precise cam lobe adjustments on this long small diameter camshaft to be very sensitive. You will still have to fine adjust each one. If you could clock the flats to the easy-to-set EO location, it might prove helpful. Use a degree wheel on the crankshaft, set the #1 cylinder at 40-45⁰ BBDC on the power stroke and back the cam lobe up against the exhaust lever roller and snug one set screw. Fine adjust till you get EC at, or just after TDC. Go to the remaining cylinders adjusting for the EO at the same setting. This is a very slow speed engine so any valve overlap is likely not beneficial. After setting the exhaust valves, go back and adjust the intake valves using the valve lash. There may be some slight variation in the possible exhaust settings, but usually all will be close to the desired setting. You probably won't get them all to the same setting, but close should be good enough. Replace all set screws with new and tighten. Take your time.

    Jeff
     
  18. Jan 9, 2020 #38

    Gordon

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    Jeff: Thank you very much. Your input has been very helpful. I am sure that I am now on the right track. I am presently waiting for a couple of things to continue but I am now confident that I will get it running. Valve timing is the answer. The extended running will come later.

    This and other on line groups are very helpful. Frequently we are too close to the problem to see even obvious solution. The internet is not all bad. There are some real advantages.

    Gordon
     
  19. Jan 16, 2020 #39

    Gordon

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    Latest observations on the Snow: I think that the most important aspect of valve timing is to be sure to start the intake stroke after bottom dead center. If the intake is started before bottom dead center a puff of exhaust blows out through the manifold and exhausts the manifold chamber which then must be refilled in order to start filling the manifold with a combustible mix. This is my theory and I am sticking with it until proven wrong but once I made sure that the intake started ATBC I could get the engine to start.

    As suggested I have made a rod coupling with RH & LH threads to adjust the stroke and prevent the loosening of the set screws and uncoupling of the rods. I then put the assembly together with the #1 and#4 heads removed and discovered that as built the #3 piston extends into the combustion chamber by 1/8" and #4 piston is 1/8" short. I then did a CAD layout and confirmed this. In order to get the correct position there is a 5/16" gap between the two piston rods. Each rod should be about 1/8" longer. I am not sure how much this affects the running but I am sure that it it does not help.

    Gordon

    I just back into the CAD drawing and checking parts and I have found that I had cut the piston retaining groove from the wrong end. However it just meant that the piston was too far in the other direction. Both piston rods should be shortened by .07 in order to center in the cylinders. Back to the lathe to remake the piston rods. By my calculations and CAD drawing the groove on each rod should be 3.59 from the end, not 3.66. Now if I just did not screw up again. That is a real possibility with me lately.
     
    Last edited: Jan 16, 2020
  20. Jan 24, 2020 #40

    Gordon

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    Does anyone have a picture or drawing or description of how Doug Kelly utilized a point ignition on his original Snow? He used the electronic ignition later. The electronic ignition is kind of fussy and I was thinking that perhaps the point ignition would be less fussy. I am not sure where and how to place the four lobe cam without it being unsightly.

    Gordon
     

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