Nogyro

My Feedback: (10)

This is the first time I've tried ganging rudder servos on a pull/pull system with the Hitec 5955TG servos. I've done it with them in the tail using push/pull without any problems. I'll be using a 4" offset arm going to the rudder. What size arm do I need on the first servo? I have a 3" straight arm, but would I be loosing too much leverage with that long of arm. Would a 2 1/2" or 2" overall length arm work better? I've got the programmer, so I should be able to get them dead on so they don't bind. Would it be worth it to broaden the dead band one number just to be on the save side?

Thanks,

Josey Wales

My Feedback: (61)

subscribed!

altavillan

My Feedback: (1)

Any arm that ligns up with the auxilary holes in the first servo horn. You can save yourself some work and grief buy using the Karbonite horn that comes with the 5955 on one servo, and the aluminum horn of choice on the first servo. On the Karbonite horn make small slots for the linkage to have some freeplay to eliminate binding. Under a large load the second servo will catch up to the first servo and do near equal work.

JoeAirPort

My Feedback: (41)

I assume you're using the 4" offset arm on one servo and deciding which one to put on the other? You would want to use one that would line up with the tapped holes on the 4" offset arm. Measure them and just choose one that lines up exactly with those. For example if they are 2" apart on the 4" use a 2". If they are 2.5" apart use a 2.5". They should be exactly the same so your geometry matches and eliminates binding. It doesn't matter which ones you use, just so the second arm's holes line up with those holes to the thousanth. DOD had some non-binding geomtry how-to videos for ganged servos. That's exactly what you need to see to understand this. You can match the geometry using the pushrod lengths and get it totally dialed without any power on the servos. Once you have that done then you just program the centers and endpoints to get rid of buzzing. To do this right takes a little learning but well worth it.

Nogyro

My Feedback: (10)

Thanks for the advice guys. [sm=thumbs_up.gif] I knew whichever holes I used to on the two arms, they had to be the same. Just didn't know if I would loose some torque by using a 3" vs. a 2 1/2" arm when connecting it to the 4" offset arm. The 4" is a SWB, my 3" is an AirWild, then I have an assortment of the Karbonite arms that come with the 5955 servos. I don't have the 4" arm yet, but it appears to have several holes to choose from, just like their single sided arms. I'll get over to DOD and check out the vids. This doesn't sound too bad. It will just take some time to get everything dialed in just right.......

JoeAirPort

My Feedback: (41)

You don't lose any torque as long as the holes in the shorter arm are the same distance as the holes in the 4" offset arm. It makes it an exact 1:1 ratio for mechanical advantage and needs to be so you don't bind one servo against the other throughout the entire travel. I don't think the dead band needs to be increased if it's done right.

I assume you're using the titanium turnbuckles for the pushrods. These can be precision-fine tuned so the binding is zero throughout the entire travel. One thing I'd do is once I got to the servo programming, I'd keep one servo loose so I could sight the two sets of holes to line them up before even connecting them. That keeps you from damaging something if the servo's are too far off by accident.

Nogyro

My Feedback: (10)

Yep, the spacing has to be the same on both arms. Gottcha.

I will be using the titanium turnbuckles to connect the two servo arms together. Good tip on keeping one servo loose and making sure they line up before connecting them. They probably don't give you much warning before the smoke comes. [&o] Unlike an aileron that can flex a bit, these things will be locked in there tight.

Thanks