Just as a side note on bending. In our manufacturing business we've made hundreds of thousands of bends on tubing. We've owned and used Swiss made mandrel benders and regular hydraulic benders. The mandrel benders if adjusted properly maintain the roundness of the tubing as it's being bent. Without the internal mandrel adjusted to contact the inside walls of the tubing just behind the beginning point of the bend, the tubing wall will collapse inward on the inside radius which will cause the finished part to be slightly oval, rather than almost perfectly round, which weakens the tubing bend. A typical hydraulic bender like your local muffler shop uses does collapse the inside radius wall. The bottom line is all benders stretch the outside radius tubing wall. In other words a .035 wall tubing would be less than .035 after the bend was complete on the outside of the bend. On larger tubing like a lot of the tubing we bend daily, the steel becomes heated from the stretching and compressing forces applied by the bending dies. When bending larger tubing there is not enough heat to affect the metallurgic makeup quality as welding it will. The only reason I know the wall stretches and thins out is because many years back one of my suppliers delivered us a load of inferior steel tubing that during the bending process the steel stretched as far as it could then ripped open. I was shocked to see how thin the wall had become. Since then ever so often when we receive tubing I make a bend on it then cut through the center of the 90 degree bend to check the remaining wall thickness. As some would say "Who'd a Thunk That" I am no expert on this subject but I'll bet I have personally made a minimum of 100,000 bends on tubing in my short 45 years working in and owning manufacturing businesses. I can't count how many bends have been made for me!
Larry H > On Sep 10, 2014, at 9:21 PM, Mark Langford via KRnet <krnet at > list.krnet.org> wrote: > > Tony King wrote: > >> My builders guide shows the rudder pedals as bent tube rather than welded. >> Has anyone built them this way? What are the pros and cons? > > Bent would be stronger than welded, as there would be "no heat affected zone" > to weaken the parent material, as you get from welding. A CNC bender would > make quick work of this job, but given the scale, it may be difficult to > recoup programming costs without buying a bunch of them. Somebody in that > business...like nvAero, might just be up to the task. > > I used .049" for mine, and have thoroughly abused them on landings by pushing > hard on both pedals out of pure apprehension! But they have almost three > thousand landings on them, so .049" is sufficient if welded properly. See > http://www.n56ml.com/pedals/index.html for more on that... > > Mark Langford > ML at N56ML.com >
