Brian builds Atkinson Engine

Brian

I am going to go out on a limb here and say that Increasing the bore of your engine is not going to solve the problem of why it is not running.

You should already know this. In order to build a fire you need 3 things.
1. Fuel - something to burn
2. Oxygen - you can't have a fire without it
3. Ignition - some means of starting the fire

If your building a campfire its pretty simple, throw a match into a pile of dry leaves and sticks and away it goes. You have all 3 elements.

If your trying to build a fire inside a cylinder head on top of a piston things get a bit more complicated but you still need all 3 elements. As well the fuel and oxygen need to be mixed together and be pressurized to a ratio of about 5 to 1 in order to be ignited by the spark.

In order to check for a compression ratio hold your finger over the exhaust to plug it off and turn the motor over with a drill. If it doesn't blow your finger off the exhaust then you may not have a high enough compression ratio. Possibly leaky valves and/or piston.

Once we have enough compression lets move on to fuel. I believe that you said before that it would run for short burst then quit. It was probably out of fuel. Even though there was fuel in the tank it was not sucking it up. Let's give it a hand. Find a way to attach a gas line to the exhaust and run it to the fuel tank to pressurize it so that we can force the fuel out. This is something that we did with RC planes so that we would have reliable engines no matter what the orientation of the motor was.

Now if your compression checked out that means there was air coming out the exhaust which meant air was going into the carb onto the top of the piston. Unless the air in Barrie doesn't have any oxygen you have met rule #2 above. You should also be able to see or feel that fuel is coming out of the exhaust. This means you have met rule #1.

Now we deal with Rule #3, igniting the fire. As I recall we want to have a spark a few degrees before TDC (top dead center) on the compression stroke. Take the head off if necessary and verify that the plug is firing at the proper time with a good healthy spark.

When you get #1, 2 and 3 in the proper ratio at the proper time that motor will start to purr like a kitten.

I believe you said that you wanted a longer spark plug as it didn't reach far enough into the head. Would it be possible to counter bore slightly on the plug seat in the head to allow the plug to sit deeper? Might not work, just a thought.

I know that this sounds elementary Brian but the engine isn't running so something isn't right. Check, check and recheck. Don't take anything for granted because if you do it will come back to bite you. I learned all this one day many years ago in the school of hard knocks. It makes an interesting story. I guess I should type it up and post it some day.

Remember, keep your stick on the ice, I'm pulling for you.

Cheers

Don

I would have to agree that the bore size isn't going to change anything, unless the compression in the current set up is so low that it is insufficient to cause an explosion, hardly likely unless there are leaking valves. I would also check the means of providing ignition, in terms of the electrical components.

This is a visual of the new game plan. #1-Bore cylinder out to 1" dia. and make a new piston, this time with one or two Viton o-rings. #2--Rotate the cylinder head 180 degrees, thus putting the sparkplug on top so that raw fuel can not pool around the end of the plug and drown it. Make a new manifold that bolts to the cylinder head, but this time it only directs exhaust down and out to the echaust stack which is moved to a new location. The intake port will be blocked off. #3--Drill a new intake port right through the side of the cylinder head to access the intake valve and mount the carb level with the centerline of the cylinder, and use a conventional carburetor. This also elevates the position of the carb a bit and still lets me use what was the vapour fuel tank as a conventional fuel tank. #4-- Probably this will ultimately mean that the cams for the exhaust and intake valves change places, but they can do that easily enough.

Today I made a new 1" piston from grey cast iron. This one has a Viton o-ring. Its been turned, lapped, abd tested for fit in the cylinder with the o-ring on it.

This could all be the result of "Too many new things" all at once. I never built an i.c. engine without rings before. Jans plans didn't call for a ring, and I HAVE heard of other i.c. engines without rings. I didn't find out until after building mine that Jan actually DID use a ring on the engine he built.--That bit of wisdom was hiding in the literature. I never built/used a vapour carburetor before. Some people swear by them, but it just seems a bit "weird science" to me. I know that I made the bore smaller than was specified, because I didn't have a larger reamer than 7/8". I never built an engine with the strange arrangement of levers that the Atkinson has instead of a crankshaft. My experience has shown me that any time you position a sparkplug at the lowest point in the combustion chamber, once it floods its impossible to clear it without removing the plug, and doubly impossible if the way the engine is built means that you can't even get at the plug.
So---I'm going back to what I know and has worked for me in the past. (I have built two succesful i.c. engines.) First, we bring the bore up to spec. Then we make a new piston WITH A RING ON IT. Then we rotate the cylinder head 180 degrees and get that damn sparkplug up top where it can't get drowned, and if it does its easy to acces and pull out to check. (The head attaches to the cylinder with a square bolt pattern, so its not a big deal to flip it 180 degrees.) Then we try a real carburetor and forget this vapour tank business for now. I can't do anything about the strange arrangement of levers instead of a crankshaft, but thats why I picked this engine to build.--I know it works because I've studied a dozen different videos of this type of Atkinson engine running.---Oh, the games we play!!!---

Well Brian, I know your persistence will pay off in the end. And, we'll all learn from it. Keep chargin'!

Todd

The suspense is killin' me

Jim

The rebirth continues. New manifold with only the exhaust hole drilled thru, the intake port blanked off to totally seal off the original intake path. New longer "muffler" made from some hex brass I had laying around. Note that there is a 0.040" dia hole thru the bottom of the exhaust stack so I don't get raw fuel puddling in the bottom of the exhaust manifold.

Looks good Brian. Don't give up! I really appreciate your sharing problems along with success, it is educational.


Lee

So, there we have it, The cylinder has a 1" bore and a new piston with a ring to match it. The cylinder head has been rotated 180 degrees to get the sparkplug up top. The old intake port has been sealed and a new one created straight through the side of the cylinder head into the valve cage cavity. A new very short intake pipe and a Traxxas carburetor. A new manifold which only has an exhaust port in it and a new "muffler". All I need now is a new head gasket, switch sides with my exhaust and intake cams, and the kiss of an angel.

Brian,

This is the best cliffhanger I have ever seen on this site.
I can't wait for you to get it to work.

The best of look to you.

Brian

Well it looks like plan #1, 2, 3 and 4 haven't produced a running engine as yet because you always let us know as soon as you get it running. Go back and check steps 1, 2 and 3 in my last post. You get those right and I bet your engine will run just fine.

Good luck

Cheers

Don

Made a new valve guide and installed it last night with Loctite, lapped the seat and left it overnight to dry. Got up this morning, instlled valve and spring and hooked up to leaktester. Leaks are gone!! Airtight as Mrs. Cartright!!

YUBADUBADOOO!!!!!! The engine runs, under its own power. Hot Damn!!! Happy dance in the Rupnow garage!! YAHhOOOOOOO--Video to folow after social commitments and clean up!!!

Congratulations.

It even makes me feel good. I love a happy endings.

Brian

Glad to see that you finally got it running. You changed so many things at the end that we will never know for sure what the problem was that prevented it from running earlier.

Anyway I guess you should get a for your perseverance.

Cheers

Don

Well done Brian. Your perseverance paid off.

Congratulations Brian ,another great working engine ,your skill and efforts paid off again.Thank you again for sharing another VERY interesting build with us.

Regards ,
Ian(seagar)

Congratulations Brian - that was some journey. Do you have some idea of what it was that prevented it from running before?

Jim

AussieJimG--Twas either the leaking intake valve, the lack of a piston ring, or a combination of both factors working together. I don't think it was the bore being a bit undersize. If the leaky valve and piston ring had been okay I'm sure it would have ran with the undersized bore. Its all well and good for people to say "Fix one thing at a time so you'll know exactly what the problem is", but I have enough work and time into this that I didn't really care that much as long as it ran. Its a lot easier to fix multiple things in one go than to disasssemble and reassemble 3 or 4 seperate times to isolate the problem.