Author Topic: Snow engine  (Read 1993 times)

Offline GordonL

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Snow engine
« on: May 22, 2017, 06:38:50 PM »
I am building a Snow tandem engine and I have everything pretty much completed. As always I am having compression problems. The pistons, rings and valves seem to be fine but I am leaking badly around the lip seal at the end of all four cylinders. I can purchase new seals but I have a feeling that I am just going to have the same problem. At some point you have to install the seal in the wrong direction over a recess in the connecting rod which may be turning the lip in the wrong direction.

I was wondering about using string packing similar to what I have done in the past on steam engines.

Do any others who have built this engine have any advise on what to do?

Gordon

Offline fumopuc

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Re: Snow engine
« Reply #1 on: May 22, 2017, 07:17:38 PM »
Hi Gordon, sorry that I cannot help.  I am shortly before the same step with my Snow build. Hopefully the lipseals will be in place during the next weeks and I have to do the compression test than also.
If you put the seals in position on the piston rods, may be it would help, if you use some Office Tape around the rods, similar like this one
https://www.amazon.com/Scotch-Magic-Inches-Boxed-810K6/dp/B00006IF67/ref=lp_1069326_1_6?s=office-products&ie=UTF8&qid=1495476613&sr=1-6
to protect the lipps of the seals during the gliding over the recess.
Kind Regards
Achim

Offline Rustkolector

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Re: Snow engine
« Reply #2 on: May 22, 2017, 10:14:00 PM »
Gordon,
It has been a while since I built mine, but I did not have a problem with the seals during installation of the head components.  I did have an initial concern of tearing the seal lips so I rounded the square cut ends of the recesses a bit so the lips would not be snagged. With a little oil they went on without any issue. I know I had them on and off a couple times. You could use anything to radius the ends of the recesses in the piston rods. I think I used an abrasive paper covered small file to smooth the square edges. If you made the recesses to the depth on the drawings and round the ends of the cuts, you should have no problem.
Jeff

Offline GordonL

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Re: Snow engine
« Reply #3 on: May 24, 2017, 02:07:39 PM »
I found a temporary solution. I packed up my backpack and will wander around in the wilderness for several days. The problem will still be there when I get back but for now it is gone.
« Last Edit: May 24, 2017, 02:22:17 PM by GordonL »

Offline Tennessee Whiskey

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Re: Snow engine
« Reply #4 on: May 24, 2017, 07:50:29 PM »
Might still be there, just may "look different " when you return  :thinking: :old:

Cletus

Offline crueby

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Re: Snow engine
« Reply #5 on: May 24, 2017, 07:59:50 PM »
Gone WalkAbout. Usually works!

Offline fumopuc

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Re: Snow engine
« Reply #6 on: June 04, 2017, 04:18:33 PM »
Today I have put the first lip seal in position at cylinder #1 at my Snow engine.
Doing this, I have recognized that my proposal top use an office tape as a protecion for the lip was not very well thougt out.
I have forgotten that the bronze bush is just in front of the lip seal.
I apologize for  the confusion.
« Last Edit: June 04, 2017, 04:37:59 PM by fumopuc »
Kind Regards
Achim

Offline fumopuc

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Re: Snow engine
« Reply #7 on: June 05, 2017, 10:10:06 AM »
Hi Gordon, I will try to give some useful input again.
Yesterday I put the lip seal of cyliunder #4 (close to crankshaft) in position.
After five time disassembly and reassembly I could move the piston rod with a reasonable force again by hand.
This took me nearly 4 hours.
Today I have done the same job with cylinder #1 again, other end of the engine.
I have used a little different process today because I wanted to the see the lip seal in position and if it is still in a good condition after pushing over the piston rod.
Yesterday I have pushed the complete unit, cylinder head and cylinder head cover pre-assembled over the rod, so I could not see the lip seal, I was just wondering about the strange force which was needed to push it over.
Watching the process directly now, I could see the failure immediately.
See picture one, this is the again dissembled cylinder #1 from yesterday evening.
Picture two shows my attempt from this morning at cylinder #1, where I discovered the problem first, with the damaged lip seal.
Cylinder #1 is closed in the meantime again, to protect the lip seal during the assembly, I have used a piece of drill rod, same size of the piston rod, pushed from the outside slightly into the lip seal to open it a bit. I will post a picture soon.
May be this experience will help you to find the problem after your return from the wilderness.
But anyway, wilderness is always a good place to relax.
Kind Regards
Achim

Offline fumopuc

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Re: Snow engine
« Reply #8 on: June 05, 2017, 11:37:03 AM »
Here are two pictures of my current lip seal assembly process.

Kind Regards
Achim

Online sco

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Re: Snow engine
« Reply #9 on: June 05, 2017, 12:44:42 PM »
Achim,

Just a couple of alternative ideas;

Can you put the lip seal on last - this way you can use the tape to protect the sealing lip and drive it home with a tube.
Have you deburred the cross hole - this will reduce the risk of cutting the lip.

Simon.
Ars longa, vita brevis.

Offline fumopuc

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Re: Snow engine
« Reply #10 on: June 05, 2017, 02:05:28 PM »
Hi Simon, thanks for your thoughts.
After a closer look to all, I think I do understand the circumstances now much better.
I am using an Elring FPM lip seal with dimensions below in the chart.
This lip seal is close to the dimensions in the drawing, but mainly matching my 8 mm silver steel piston bar.
If I measure it carefully with a calliper, so it has an 7,14 mm hole, without any tension, for the 8 mm shaft.
Under my "very special ALDI USB Microscope" , you can see the very very small chamfer.
So now you can imagine what will happen if you try to push a 8 mm bar in this 7,14 mm hole.
If the bar will not match the entire chamfer, what is unlikely, immediately the whole seal will be squeezed undefined until you push it with pure force through.
The result is the earlier shown deformation of the lip area.
Next to do, I will disassemble the inner cylinder head #2 and #3 to get the seal in.
Kind Regards
Achim

Offline GordonL

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Re: Snow engine
« Reply #11 on: June 08, 2017, 05:12:12 PM »
At the suggestion of someone else on another forum I am going to try some O Ring supported U cup seals which look promising. I just got them and I have not tried them yet. They are McMaster Carr #9505K14. Presently I have gotten somewhat sidetracked and have kind of lost my drive for this project but I will get back to it.