SeditiousCanary

So, what do you folks think about Pull-Pull systems? Are there some things you would/would never use it on? Clear advantages? Obvious problems?

I get Ackerman, so no issues there, but I'm curious what real world experience has tought you all about his. I'm also wondering what one uses for the line on Pull-Pull? I can't say that I want to use thin steel wire. Would Spectra, Kevlar or a high tech fishing line like Spider Wire work well? Keep in mind this woud not be a gas plane.

Thanks.

barto

I use fishing line, works great, never had any problems with it
Dont know what you mean with Ackermann, is it a brand of something??

SeditiousCanary

Ackerman is akin to a turntable. The outter edge turns at the same RPM, but actually travels faster then the center of the platter. Here is a great artical about the subject I jacked from another thread: [link=http://members.cox.net/bdfelice/Ackerman/ackerman.htm]Ackerman[/link]

barto

Aaah so thats what you mean.
Thx

CafeenMan

The two great advantages to pull-pull are light weight and the control always being under tension. With a pushrod, the control gets pulled (tension) in one direction, but pushed (compression) in the other direction. Because of the compression direction, the pushrod has to be bigger and stiffer to resist collapsing. Because pull-pull always pulls, it can be smaller and much lighter while still being very positive.

I used .020 music wire on Rustik - mainly because the one thing about pull-pull that scares me is a cable breaking where it has a tight radius bend through the fitting.

barto

Another advantage: if you use plastic pushrods they expand in warmer weather so your trim is totally offset.
Ofcourse that isn't all too bad cause you just trim it out again but still.

Kenny R

I have been using the smallest diameter music wire from the local hobbyshop (cant remember the exact size) but it is very small. I have had no problems with this method. The wires do not stretch over time.

I have used the spiderwire on elctrics, it seems to always be working loose, I think it is stretching with time.

The latest plane that I built I used kevlar. The reason I changed to Kevlar is I had a few tighter than normal turns to make and the wire was binding somewhat. The kevalar seemed to be working great till the 5th flight. It broke on the elevator where it went through the hole in the fitting that screws into the cleavis. I thought this stuff was basically unbreakable, but it sure did wear fast. I mangaed to save the plane.(lucky me)

They make a fishing leader that is very small, it is a braided steel cable with a nylon coating it is a 40lb test that I'm using. I replaced my kevlar with this and it seems to be working great. It is very flexible and strong, and still is very light.