New: Pull-Pull System - Need Help!!!
Hi Guys,
I am an old time builder from way back. However after 45 yrs. + of building and flying experience I have just never have gotten around to putting together a Pull-Pull Cable System. I am working on installing one now on the Elevator in a P-51-Mustang. So all has been going well, except I am at the point where all is connected up and the cables are setup & the tension is fairly firm. I have the servo centered and have tried to test the control system. However, when I check the tension of the control service when the servo is centered and at rest, there is a lot of sloppy play in the Elevator. I try to flex it a bit up & down. I feel it is very sloppy, way too sloppy nothing like my old tried & true controlrod set-ups. I truly believe if this was flown with the current setup, there is 95% chance there would be some serous flutter. All I can imagine is it fluttering and getting worse by the second, until the tail actually explodes into pieces and crashes due to the Fluttering issue.
I have tried to adjust the tension of the cables to a very tight & firm cable setup, to a set up with tension with some slight amount of slack in it. I have tried several types of tension setups and all producing the same result, sloppiness in the Elevator which I really believe would be a “Big Time Flutter Issue”. I even checked all of the other aircraft that I own (13 of them) that are currently setup to fly with straight rods. All have no issues of being sloppy, none at all using the old tried and true straight rod approach….
The last thing I will add is the cable run description:
Looking inside the plane, with the wing saddles facing upward.
From the Servo: There’s approx. 4 inches of a straight cable run in where the cable then enters into a plastic guide tube. There is a slight 10 deg. downward bend in the plastic tube guide as it passes thru a former. Then there is a straight run of about 16 inches at approx. a 5 deg. downward direction. Then it passes thru the former and is pretty much a straight run for about another 4 inches and it connects to the U-shaped wire to which is setup into the two Elevator halves. All of the connections appear to be tight and no slippage.
What I did find is that when you are in Neutral position and the Elevator Halves are Centered, if you reach into the back of the fuse where the hatch is open on the bottom of the fuse below the tail section and grab the cable, you can push down or Pull up on the cable approx. 1 inch in either direction, the cable seems to have some play and stretch a bit. All of the crimps and the clevises are tight, it almost seems like as if the cable itself is stretching a bit in either direction like a rubber band. The System I am using is from Dubro. The Dubro Pull-Pull System 4-40 - (Tower Stock# LXD859 • Manufacturer Stock# 518).
Please let me know your thought’s or comments on this set up.
Thanks a Bunch
Ed
Last edited by Electriceddie; 01-12-2019 at 01:38 PM.