Pull-pull systems and bellcranks...
 

I'm having trouble trying to layout the fuse servos (thottle, rudder, and elevator). Here are the basic problems:

1. Becasue the engine is mounted inverted the trottle control rod has to enter the fuse just about a 1/4" off the floor.

2. I'd like the cables for the rudder pull-pull system to run close to the floorboard (under the pilots seat)

2a. Is it OK to use the servo arm instead of a bellcrank (the large Airtronics arm is a perfect size match for the rudder control horn)?

3. Ideally, I'd like to have the elevator pull-pull cables attached to a mock-joystick which would be moved by the servo via a short control rod. But where to put the servo?

The real problem is thinking of a way to install the servos so that I can get at them for adjustments. I'd appreciate any photos of the "guts" of your planes that might jog my mind into finding a solution. Thanks.

RE: Pull-pull systems and bellcranks...
 

Hi Don,

Construction on my eindecker has not yet proceeded to the stage of servo installation so I can't (yet) post any pics of my servo setup.
I did however have a look around for possible uses of bellcranks, pulleys ect.
The main problem also with my eindecker is weight, specifically how to cram as much of it as possible into the fuselage nose section.
This makes it very difficult to install, say the elevator servo in such a way, that the pull-pull cables exit the fuse at the required (and scale) location. Hence I've considered the use of either pulleys which would deflect the wires accordingly and allow some margin in terms of servo location or alternatively bellcrank systems (which amounts more or less to the same)
I reckon it should be perfectly in order to use a modified servo arm as a bellcrank, I'll probably end up doing just that.
Well, here are some of the pics I've scavenged:D, hope they give you some ideas

RE: Pull-pull systems and bellcranks...
 

And some more

RE: Pull-pull systems and bellcranks...
 

Should be about done after this/

first is a relatively low quality pic of the insides of a K&W Pfalz EI. The bellcrank with the pull-pull wires for the elevator is visible below

second is taken from the manual
(available online at: http://www.kwmairpl.com.ph/KWManuals.asp)

RE: Pull-pull systems and bellcranks...
 

Oh btw, for the throttle control rod you might consider using a flexible bowden cable/ This would give you better allowance for the throttle servo location and you could lead the cable directly adjacent to the fuselage floor if necessary.

Also, it might help making a 1:1 cardboard mockup of your fuse profile and positioning battery, servos, tank, bellcranks ect. accordingly so you can 'optimize' the location for each component prior to its actual installation.

Hope I could be of some help/
Oh and pls post some more pics as you progress with your construction, I'd be very interested[8D]

cheers,

Trev

RE: Pull-pull systems and bellcranks...
 

I know this is just slightly off-subject,
but here's a very nice example of an aileron pull-pull system