engine sag

My last question got answered so fast I'd like to try another. I have an os 35s on a ringmaster. Before this it was mounted on a galaxy, right side of fuselage, tank on left side (4 oz clunk on tongue muffler pressure, sig 5% all castor oil, apc 10-6) On galaxy got great 4 cycle, two cycle break. On Ringmaster engine is on left side, tank on right side. Same tank, same fuel, same prop. Now I have a really sensitive needle. Will crackle on the ground and on takeoff goes to 2 cycle. One click richer and it never goes to two cycle at all. It acts like it is two lean in that on pull up the engine sags. Any ideas?
Thanks
Jim

LAST EDITED ON Jun-14-06 AT 02:32 PM (CST)
 
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LAST EDITED ON Jun-14-06 AT 11:09 AM (CST)
 
I'm assuming that the engine is now mounted on the inboard side of the fuse, with the tank on the outboard side?

If so, then centrifugal force is likely the culprit. With the tank being "downhill" from the engine, in flight. Before, the engine was downhill during flight, which made the entire system more friendly.

Best method is still to mount the engine and tank on the same side, for most of us.

I'm wondering why everything is spinning around?

LAST EDITED ON Jun-14-06 AT 11:40 AM (CST)
 
John is exactly right. Generally this type of set up won't work.
It'll do exactly what you described, run O.K. on the ground but once in the air centrifugal force creates a "head"/resistance to fuel draw and the engine will run much leaner. With a good needle valve you probably could find a compromise needle setting (very rich on the ground) but it's likely going to be very sensitive.
Engine and tank on the same side is generally the most reliable set up. Second to that would be with the engine outboard and the tank inboard.

thanks for the input. I knew it didn't work, just not why. I was hoping for a fix other than remounting everything on the other side. As you say, it all else fails go with what you know works.
jim jorgensen

>thanks for the input. I knew it didn't work, just not why.
>I was hoping for a fix other than remounting everything on
>the other side. As you say, it all else fails go with what
>you know works.
>jim jorgensen

I don't know why you would even want to mount the engine on the inside, but the people who responded have nailed it. Centrifrugal force causing the engine to have to "pull" the fuel "up". It is like mounting the engine on a test stand and then lowering the tank about nine inches (3 gs of force will triple the effective distance).

One thing I would caution is the fuel. You mention SIG all castor. With the 35S you should make sure this is 25% all castor and not the usual 20%. The rods on this engine are soft and it won't take much lean running to ruin the rod. I would recommend somewhere between 25% and 28% total oil for this engine.

LAST EDITED ON Jun-19-06 AT 02:16 AM (CST)
 
>I don't know why you would even want to mount the engine on
>the inside, but the people who responded have nailed it.

Wasn't this in vogue at one time (early 90s, perhaps..)? I've seen pictures of profile stunters (modern ones) with engines mounted inboard. Supposedly keeps the fuel droplets off the glow plug, but that does sound a little silly.

Inboard tank/outboard motor has been used, particularly in Slow Combat. Mainly to get around the tank being too long to fit between wing and backplate.

I suppose, other than mounting the engine inboard, using an inordinately tall tank (especially if it were plumbed uniflo) might also cause the problem.

Why did you change from the Galazy set up when it was working? You should have went back to that when it didn't work on the Ringmaster the way you did it. As I have witnessed, inboard tanks and out board engines work, but, have to set a little leaner on the ground. ---DOC Holliday