Was working on the throttle linkage on the FJ-4-15 and decided rather than trying to get the ratio between the bellcrank and carb worked out it would be easier to just have a link that would compensate for the bellcrank over-travel. Putting the brain in gear I grabbed a ball point pen and removed the spring. Found a piece of aluminum tubing the spring would fit inside of... (7/32) and came up with the following.

Cut the aluminum tubing off with a tubing cutter which put a little crimp on the end. Found a piece of carbon fiber tubing (3/16) that just fit inside the aluminum tubing, couple #2 quick links, two 2-56 nuts and a 2-56 threaded rod completed the parts needed. I ground the tips off the outside of the nuts so they would fit inside the tube and drilled out the center so they could be slipped over the threaded rod. 1st photo is of all the parts before assembly. Last photo shows the spring assembly as it will be installed into the aluminum tube.

Estimated the overall length of the finished control rod and cut the CF tube and threaded rod. Soldered one of the modified 2-56 nuts on the end of the rod and soldered a solder quick link on the piece of rod I had cut off and cut it the same length as the CF tube. I also scored the outside part of the rod that will get glued inside the CF tube with JB weld.

Second photo is the link assembled before anything was glued together alongside the original hard link. Used a spare 2-56 temporarily installed on the threaded rod to put preload on the spring and hold the rod in position. After double checking the length I pulled it apart and used JB-Quick to glue the modified 2-56 nut into the end of the aluminum tube, the crimp from the cutter prevented it from being pushed out the end. I used a tooth pick to smear JB-Quick just on the inside end of the tube and used a scrap piece of the CF tube to push the nut in and seat it against the end. After the JB-Quick had cured I applied a liberal amount of Teflon grease to the plunger and spring, inserted it into the tube and held it in position with the temporary nut. I then degreased the inside of the tube where the CF will be inserted with a Q-Tip dipped in acetone.

Used JB weld to install the soldered quick link into the CF tube then glued the CF tube into the aluminum tube. When the JB weld was set I remover the temporary nut and installed the 2-56 quick link. This link has a solid connection when pushing but when pulling it will start compressing the spring when the throttle is at the end of it's travel and the bellcrank still has room to move. I think something like this can be bought from the RC market but it was fun to make and works as advertised.

Bob,
Pretty clever, but I agree with Bill. I use a transfer crank to adjust the travel ratio between the BC and engine. I like to have full throttle range when flying carrier or scale. I have used similar spring concepts on sport planes, but not for competition.
John

I set my three line systems up so full low throttle shuts(chokes) off the motor. I have a throttle stop on the handle which is adjustable and sets the idle rpm. By releasing the stop I can shut off the motor as required in scale. It takes a bit of tme, but once set works well.