As to the bellcrank ....I expect to have them packaged by next week and I will be sending some to Sam's Stuff and Hobbies and Maxwell's hobbies. We were going to make them from metal but the price ballooned up so we will have them in Nylon. Nylon is better too because it works smoother, with no drag. I have concluded the design for the plane and it is in drafting now.
Now the handle....The standard three line handle will operate it and since the plane will be on (about) 50 foot lines that seems like a good choice. Of course, any way that you can pull a third line will work.
Larry
YIIKES!!!!! I just looked at the price of the handle I guess I will need to get engineering to work on that next.
Feel free to take inspiration from my home-made handle - it is important to note that a pull on the trigger yields a pull on the throttle line results in "HIGH" speed. Most carrier flyers use a pull for high speed. With this arrangement, you want the double-drag of the elevator lines to pull you down to low speed when you release the tension on the throttle line. It makes it much more reliable to come up off low speed quickly should you need to if you are pulling on the throttle line for high speed.
With the Brodak/commercial units, it is not important which way is high or low because the mechanism applies a pull to either the throttle line or both elevator lines. The throttle line moves the opposite direction of the trigger.
I'll include a picture of a Cox 3-line handle that was sold with one of their RTF plastic planes - You can see that this one moves the throttle line the same direction as the trigger (note that the throttle line is 'forward' and the elevator lines are retracted into the housing in the bottom pic - vice-verse in the top). This one would be slightly easier to manufacture, because the throttle trigger and the throttle line attachment are one piece which simply slides back and forth.
I'll also note that my home-made unit was modelled after a Hot-Rock with a coat-hanger wire throttle arm that won profile carrier at one of the Lincoln Nats, and my bellcrank is a Perfect 1/2A bolted to a home-made aluminum bellcrank.
It need not be a hugely expensive venture. (There is also a similar composite of my handle in both positions).