My Improved Snow Engine

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Rustkolector

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This is the proverbial Snow tandem double acting gas engine designed by Doug Kelley that I built in 2008. It is my favorite model engine. I never took any video of it at the time. Over the years this little engine and I have had our ups and downs and finally last year we had a bit of an accident, I admit, it was my fault. So over the last year I rebuilt this Snow and was determined to incorporate what I think are some needed changes to address the issues I was having with my Snow engine. In particular, my Snow would not continue to run without running at a very high rate of speed making everything moving on the engine a complete blur. Other Snow owners might be familiar with these issues.

So far, it seems to be running well and it will now continue running through a tank full of fuel. The engine is running at 350 RPM in the video.

Jeff

 

oldengineguy

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Jeff: Good running engine! I just completed a Snow (July 14) and have tried to start it only once, it popped and the cylinders got warm but it would not sustain itself. Work and other things have not allowed time to get back at it. One of the things I see different about your engine is the inlet manifold. Is it water heated? Did you run the water outlets into one then along side the inlet then back to the tank/ rad.? Did you redesign cam profiles? No secrets , PLEASE tell all. Thanks Colin P. S. Once I figure out how to post pictures, I'll have a go at that .
 

Rustkolector

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Colin,
With a new untried engine you have to know for sure that you have good sealing piston rings and valves. An absolute must on the Snow. Your pistons should not contact the cylinder walls. The pistons should float between the two piston rod bushings on each cylinder head. If all is good, you should feel noticeable compression on all 4 cylinders. Like most Snow builders, you are likely to have piston rod set screw retention problems with the coupling and maybe the pistons. I pinned the pistons and used a positive clamping split coupling on the piston rods. I allowed no clearance between the two mating piston rod ends at the coupling.

One of the two most significant changes I made was to change the intake manifold to a flat plane log type manifold for simplification and to heat it with jacket water. I circulate all coolant through the manifold and back to the coolant reservior. There is considerable heat lost to fuel vaporization as you probably have experienced. Use a tiny carburetor. Even if the engine runs with the original intake manifold, it will run with a wet sloppy exhaust and it will only run at relatively high speed.

The second significant change is the cam lobe profile. The original Snow engines have odd valve timing and were known for poor running at light and no load conditions. Two valves, one cam, what else would you expect? They just don't breathe well. The new cam alone has gotten two other Snow engines running that previously would not run. I detailed the cam lobe change in a past post on this same subject. I suggest you read the whole thread to see what problems others have run into. Snow engine thoughts

Jeff
 

oldengineguy

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Thanks Jeff: Yes, I think my pistons are too tight. I will definitely change the manifolds . Cam lobes are50 degree ( I wanted to try a compromise) Back to the shop! Colin
 

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