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C16 Johnson bar servo linkage

1909 Views 7 Replies 3 Participants Last post by  Don Howard
I seem to be mechanically challenged of late.

I need some photos of how C-16 owners attached their servos to the Johnson Bar.
I know that Hitec HS-81MG will fit, and probably the 85MG, too.

I have attached a picture by Pete Thornton of his servo install, but if the arm is connected, I cannot see the connector rod or mechanism.

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I usually solder a small ring lug on the end of a pushrod and secure it to the Johnson Bar via the screw used for finding the detents (you don't want the detents with R/C anyway). I also remove the spring from the pivot so allow less friction in the bar movement - less torque required for the servo to move it.

I drilled one Johnson Bar once for a standard clevis. Dulled three HSS drill bits doing it. You really need a carbide bit to punch through that stainless.
I have in my previous installations (C-16, C-21) made angle brackets to hold the servo and JB Welded them to the side of the cab. In the future, I think I'll adopt Pete's approach and secure the servo to the cab floor instead (space permitting). It's a lot easier to adjust pushrods, etc. with the cab off and out of the way. :)

BTW, here's a link to an archived topic showing how I did it in my C-21. I did pretty much the same thing in my C-16.
Glad to help Don. :) Actually, the C-21 was the one Johnson Bar I drilled. On the C-16, I used a ring lug. I also used a ring lug at first on the C-21. Servo problems later caused me to try something else, and I drilled the J-bar.

See this archived thread for photos of the first installation using the ring lug.

BTW, the ring lug would have worked. I was burning out the reversing servo, so I drilled higher up on the J-bar to give the servo more leverage. Turned out I was using too small/low torque of a servo, and the pushrod was too thick initially, causing lateral stress on the servo horn, causing the servo to constantly buzz. Ultimately, it would overheat and give up the ghost. Using a higher torque servo and a smaller, more flexible pushrod solved the problem.
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