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Engine basics => Engine set up tips => Topic started by: FLOYD CARTER on November 02, 2010, 07:24:10 PM
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The engine is inverted, sitting on the maple rails. The 6 oz. wedge tank also sits on the rails. The engine goes rich inverted, meaning I have to move the tank more toward the engine bearers. But, can't do that without grinding off some of the maple!
The tank is a commercial 6 oz wedge plumbed uni-flo. I heard someplace that the uni-flo tube position (up or down) works the same as moving the entire tank. Is that true?
If so, I guess I can pop the back off the tank and re-position the uni-flo tube--if a small amount will do any good.
Floyd
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.....I heard someplace that the uni-flo tube position (up or down) works the same as moving the entire tank. Is that true?
If so, I guess I can pop the back off the tank and re-position the uni-flo tube--if a small amount will do any good.
Floyd
Yes, true.
Rather than guess how much and possibly guess wrong and have to do it all over again, you can raise the tube more than you think will be necessary and then adjust the tank down with shims however much is necessary by trial and error (assuming you have room to move the tank down).
I had this same situation but reversed (upright engine went lean inverted) and used this method to fix it. After 3 or 4 shim adjustments, I got exactly the run I wanted.
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Or, if you have room, you can shim the engine away from the bearers. Move the engine instead of the tank. Keith Varley suggested this to me.
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Moving the engine is a non-starter! Cowling would be messed up, and it is a RE engine, so the muffler inside the fuselage would require a lot of cutting and hacking!
Thanks for the uni-flo advice. That is the easiest.
Floyd
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How would one move the uniflow pipe up or down 'more than necessary' in a commercially made wedge tank?
If it has any wedge shape on the ouboard wall then you have to move it along that wedge and away from feed pipe in the process and I can see problems brewing by doing that.
Perhaps if you had a rectangular shaped tin tank with a clunk in it, then at least then outboard wall will be vertical and the uniflow pipe can follow that wall without leaving the fuel head late in the run.
Thoughts?
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Floyd When you move the uniflow tube don't run it all the way to the back of the tank.Stopping it half way back. It is less critical there and it will still work like a uniflow until the end of the flight. It is very common for commercial uniflow tanks to be made incorrect. Brodak uniflow tubes are sometimes on top of the pickup and sometimes under it. y1
Ed
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Floyd When you move the uniflow tube don't run it all the way to the back of the tank.Stopping it half way back. It is less critical there and it will still work like a uniflow until the end of the flight. It is very common for commercial uniflow tanks to be made incorrect. Brodak uniflow tubes are sometimes on top of the pickup and sometimes under it.
Ed
Yes, good points. Paul Walker also recommended terminating the uniflow tube half way back after systematically testing 5 different termination points along the outboard wall of the tank. The idea that it must stop 3/8" - 1/2" ahead of the pickup to work correctly is a misconception.
My experience with Brodak tanks is the same as Ed's. Floyd, if you would like to let us know how your tank was plumbed when you pop the back off, it might be instructive.
How would one move the uniflow pipe up or down 'more than necessary' in a commercially made wedge tank?
If it has any wedge shape on the ouboard wall then you have to move it along that wedge and away from feed pipe in the process and I can see problems brewing by doing that.
Perhaps if you had a rectangular shaped tin tank with a clunk in it, then at least then outboard wall will be vertical and the uniflow pipe can follow that wall without leaving the fuel head late in the run.
Thoughts?
Assuming that the pickup is located in the standard position, alongside and inboard of the pickup, it is 1/8"+ away from the wedge apex to start with. if you unsolder it from the pickup and start moving it straight up, by the time you hit the wedge you are already about halfway to the top of the tank, which will be more than enough. If you resolder the uniflow to the wedge less than halfway up, you will actually be moving the uniflow a little outboard of it's starting position, producing the opposite effect from the one you are concerned about. Moving the uniflow "away from the feed tube" has no effect and is not relevant to this problem.
Fuel system problems are ones which often seem to benefit more from actual experimentation than from theory, even without misconceptions. I have used the method I described successfully as have many others.
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I still haven't fixed the tank. I made the tank, so I know how it's made. It is rectangular cross-section made of brass (the K&S tin stock was only 4", and my tank is 6" long). The uni-flow tube is about 3/8" ahead of the pickup tube, so I can move the uni-flo tube up or down a lot.
Floyd
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Hi Floyd,
I flew the grey Madman for years with the tank fixed by the compartment it is in, and always suffered leaning out during outsides. I popped the back off, lowered the uniflow 1/8th and that solved that problem.
I'm fixin' to get going on my Floyd Carter "Wildman", I'm hoping it will perform as well as your DH "Big Madman", which is going to be spectacular.
dg
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Dale. Good to hear about yet another WILDMAN. I know of at least 6 (including 2 that I now have). Even one in England is nearing completion.
You will certainly enjoy yours. If no other reason than it isn't just another Jamison or Homongous!
Floyd