servo question

[slowflyerhehehe]

I am working on a 70 inch wing type trainer that has trike gear and useing HS 325 servos and the problem is when i aline the rudder and the trike gear i cant seam to get the rudder center and if i remove the pushrod from the trike gear the rudder is just fine do you think that i need a better servo with more torque to fix this problem

[jetmex]

Sounds like the problem is in your nose gear linkage and not the servo. Do you have a way to adjust the rod to the nose gear? If not, an EZ connector or threaded clevis will probably fix you right up.

[slowflyerhehehe]

Yes it does have a adjustment and i have tryed to adjust it but seams like the pushrod does not move freely like i said i can unhook the wheel from the pushrod and the rudder works fine and centers just like it should then hook up the wheel and less travel then it happends all over again,I could fix the problem by just removeing the trike gear and adding a tail wheel but were we fly the run way is to ruf for a tail dragger and the grass is way to high. thanks

[Patch]

sounds to me like you eithier have some binding, or some slop. If this isn't the case, I'd go for the straight rudder over the straight main wheel. Besides, the main wheel is likely to get bent anyway

[ctdahle]

The main thing with a trainer is to have enough nose wheel throw to keep it running in a straight line, not necessarily enough to run esses through a set of traffic cones...(although I do think that steering your trainer on the ground through a set of cones is good practice for your left hand.) With computer radios, (to which I have become resigned, even for beginners) the hint is to land on low rates to get the model down and stopped, then switch to high rates to taxi back to the pits.

One thing that helps with binding nose gear is to take a look at your plans. Plot, on the plan, the location of the outermost hole on the rudder and nose gear arms and connect the two locations with a line using your straight-edge. Do this on both the plan and side views of the fuselage, then, in your airplane, locate your servos so that the pushrods are congruent with the lines you've drawn and the servo horns are on the lines as well. From the top, you can usually get away with a slight angle where the rudder and nose gear pushrods intersect, but make sure that it is the nose gear that is off, NOT the rudder. Best practice is to assure that the holes in the rudder control horn are congruent with a line perpendicular to the rudder datum and intersecting the hinge axis, and that the rudder pushrod runs perpendicular to THAT line.

Your nose gear and throttle pushrods may have to deviate slightly from a perfectly straight line may have to deviate slightly to get around the fuel tank and the batteries, but not much. If you MUST curve these pushrods, the curve should be a continuous, gentle sweep, breaking in only one direction. NEVER put an "S" curve in ANY pushrod because doing so is all but a guarantee that you will have a binding problem.

That's the scientific approach. Here is the quick and dirty one:

With high wing trainers, you can correct many pushrod binding problems by moving the servo tray far aft and to the floor of the cabin. This gives you more room to make the curves around the gear in the nose.