I have used the MK bell crank system with a carbon fiber rod. Is ther another product that could be used on pattern planes that would have pull pull cables connected to a bell crank servo type arm of equal length top and bottom on the inside of the fuse with control arms on each side of the fuse connected to each elevator horn? Does such a product exist. It would be a combination of bell crank and pull.

Check out the Nelson site. Many answers to set up questions. They now have the Rocket City hardware.
EXCAP232

Earl-Have you ever had a problem with the MK system? I am using this setup on a 83" Bipe elevator with short DB shafts and Hitec 5735 servos (200 oz torque)--I had some suspitions as to wheather it was heavy enough.

earl,

what plane / application have you used the MK belcrank? is it possible to retrofit into an existing or prebuilt (arf) such as the piedmont focus? are you dissatisfied with the set-up or just looking at other options?

thanks

Hubb

You can make the MK a bellcrank (I do this on my models) just make a double arm from PCB and bolt it onto the MK single arm above and below the output shaft. You will have to drill the lower hole in the little "***" on the single arm and use the standard holes for the other bolt. It works real good.

Chad,

what is the advantage to that? please explain

thanks

Hubb

Running a solid pushrod back unsupported (getting supports in can be a real pain) can be an issue with vibration and eventual failure at the end of the pushrod. If that happens your only link to the elevators is gone!!! BOOM no more plane.

At least with pull-pull back to the bell crank both cables would need to fail, if you only break one at worst you could land inverted (or at least give it a shot) and have a chance at saving something of the airplane. Plus cable will stand up to the vibration a lot better than a massive 30" long pushrod will over time.

I have used the MK bellcrank in 5 airplanes 4 being with Centrals 3/16" carbon rod from servo to bellcrank, never had one fail, but my comfort level is much much much higher now that I have pull-pull. More confidence in your setup breeds more confidence in your flying.

I think I have some pics of mine before it went in the plane I will post later.

This should give you the idea....

Thanks can773, I like your idea. Where did you get the long arm material, and exactly what is it? I have used the MK system before but did not like the unsupported rod. I needed a wider system to fit a 27% ex300l, so I made my own to custom fit the wider fuse. My is pull to a larger (3") arm inside. The horns on the outside are 1 1/2". The main shaft is 1/8th hardened steel and the arms are aluim. It just took a alot of work to make, and was wondering anyone is manufacturing something simular that would fit wider bnodies and with larger control horns.

I made the arm myself, it is 8 layers of 5.7 oz CF cloth laminated together, stiff as a board. I made 2 of them and bolted the other one to the servo arm so I get perfect geometry on the pull-pull.

Sorry but I have not heard of anyone who is doing a system larger than the MK one commercially.