Original Posted By: "Jim Markle"
Subject: Pietenpol-List: Tailwheel Cable GeometryLast week I was showing Chuck my plan for tailwheel steering. We got into a discussion about geometry and the leverage and throw required for steering. Chuck showed me how he attached tailwheel steering cables very close inboard from his feet near the center of the fulcrum on the rudder bar. His logic is that the 'throw" (or travel) is a shorter distance on the tailwheel steering arms than on the rudder horns. I am getting ready to design the attachments for tailwheel steering on mine and have been thinking more about this. First of all....our plane does not have a rudder bar...but instead has pedals similar to a J3 cub. I could accomplish the same effect of Chucks design by welding a tab onto the pedal closerto the pedal fulcrum. This way the tailwheel steering travel will be shorter than the rudder cable travel.But after thinking this over... I am not so sure that this is the best way to set this up. I am planning to use compression springs at the tailwheel steering arms to dampen shimmy. But I am thinking that the springs will also compensate for the difference in "throw" if I choose to tie the rudder and tailwheel cables together with the same travel. In addition....I am thinking thatthis should allow more steering authority with less input when the tailwheel ison the ground. Does anyone have any experience and comment on this? I am not knocking Chucks design. He is a whiz at all things mechanical. But I am just trying tothink this through before I make more parts. One thing I did notice is that 'olNX770CG's rudder seems to swipe back and forth a lot on 3-point landing as it is steered down the runway. I don't notice nearly that much rudder input required to steer the Taylorcraft.TLB________________________________________________________________________________