Four pushrod system.

[Paul Smith]

I got a message about the four pushrod setup I developed and posted back around 2008.  It worked very well on the prototype which I used for WWII combat, profile stunt and fun scale.  The model is still in service and has always performed as intended.

I used an X-crank with two ball links on each side, driving each surface with its own dedicated Dubro 2/56 pushrod (actually more pull than push).
The benefits of this setup are:

No need to connect the flaps to each other.
Independent adjustability of all control surfaces.
Elimination of the highly stressed "master" pushrod to the flap horn.
Elimination of the need for a very strong flap horn secured to the trailing edge.
Elimination of all pushrod guides.
Elimination of compression forces, the primary cause of pushrod failure.
The possiblity of swept or dihedral control surfaces.
With the exception of the X-crank itself, all the parts are Dubro off the shelf.

I didn't keep a copy of the picture of the four-output X-crank, but I have one of an X-crank with just the elevators done this way.

The X-crank was used with to pull rods on this 1/2A scale F-86.

[Air Ministry .]

AND , if one ' falls off ' youve still got some control , on the ' other side ' too .  ( The Orange Crate  etc artiles ! ) .

[Paul Smith]

AND , if one ' falls off ' youve still got some control , on the ' other side ' too .  ( The Orange Crate  etc artiles ! ) .

That is a very true observation.

However, by dividing the forces between four pull rods, the change of failure is minimal compared to putting ALL force through a single push/pull rod.