kahloq
Posts: 1698
Joined: 1/1/2006
From: Fort Collins,
CO, USA
Status: offline
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I suppose setting counter-rotating engines/props would be way to troublesome for a glow powered setup. I think, if you program in some differential throttle, you can solve the problem your experiencing. Currently, all your motors are turning normal direction which means all of them are pulling the plane left on the ground. Its sometimes hard enough to keep a plane straight with 1 or 2 motors doing this, but 4? I can see the rudder not being enough. So, either adjust the right thrust on your engines, or program in differential throttle so that the left side engines are pulling more RPM's then the right based on rudder input if you hold right rudder.
This will cause the left motors to want to pull the plane right because there is more thrust on the left side fo the plane. You can also program in the right motors to lower their RPM's somewhat if you input right rudder......just be carefull here though cuz if you do program this(the slowdown on the engines on rudder input), you need to make sure the idle of the engines is set to be able to run on the throttle trim settings otherwise inputting the rudder too far might cause those motors to shutdown.
Set this on a toggle switch so you can turn it off and on. It wont need a whole lot. I have a smaller electric B-25 that uses differential thrust and I have it set at +-35%. So, when inputting left rudder, the right motor will spin faster(up to 35% more) and the left side motor will slow down(up to 35% slower). I have it at 35% because there are no functional rudders on this plane. On this B-17, it has a working rudder/tail wheel so you probably wont need 35% mix to keep the plane straight on the runway during take off. You might try like 15-20% to see how it goes.
This process assumes you have set up the left side motors on different channel then the right side motors. One other way to do this is to have the inner most motors on same channels with no differential throttle and have the outer motors on separate channels and do have differential throttle(this may require a higher mix percentage, but would only effect those outer motors and the inners will stay at a constant RPM relative to each other all along the throttle curve).
I also have differntial throttle on a P-38, but once in the air, I dont use it and switch it off. Of course, i dont need it on the gorund much because both this and the afforementioned B-25 have counter-rotating props which mostly cancel out the pull to the left.
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RE: B-17 Flying Fortress ARF Question - 
