scsmith
Well Known Member
Some of you will have seen the thread that I started several years ago after a surprise groundloop occurred in a strong starboard cross wind when the steering link unexpectedly and suddenly released.
That thread stimulated a lot of good discussion on several related topics, one of which is the asymmetry of a "rocket link" steering link in the release points when steering left and right. The asymmetry is caused by the angle at the rudder horn from the rudder hinge axis to the attach point for the steering link being a different angle than the angle at the steering arm from the tail wheel pivot axis to the attach point for the steering link.
After some discussion with Darwin Barrie at JD Airparts, he arranged to make a modified steering arm. I spent a little while doing some trig and analytic geometry to come up with a length and sweep angle of the steering arm that would produce a symmetrical release action to the left and right, and have both directions cause release of the tail wheel lock just at the extreme deflection of the rudder. Darwin sent me the the new steering arm and a longer steering link to test out. Here are some pictures of the installation.
I have not been able to fly this installation yet because of weather, ongoing condition inspection, and some other activities. But I will report back here as soon as I can fly with it. I can tell you that on the ground, if you pull the rudder all the way to the stop, and put pressure on the tail wheel in the direction it would feel if steering, it does NOT release. Same left and right. If you put the rudder all the way to the stop and put pressure on the tail wheel in the direction to make it swivel intentionally, it does release. Same left and right.
You can also see that I substitute a normal rod end with an AN3 bolt and AN970 washer, plus some of the rod end spacer washers that Vans sells, in place of the integral rod end + stud that is supplied. This insures that the rod end stays captive in the very unlikely event that the bearing fails.
So I am pretty optimistic that this will be a nice improvement to the steering link system for those that like it. The steering link system is quicker steering than chains or cables with springs and a little slack, and arguably not as rugged as cables with springs. So there is still room for personal preference here. But for those of us that like the quick, positive steering feel, this new steering arm should give you symmetrical behavior.
That thread stimulated a lot of good discussion on several related topics, one of which is the asymmetry of a "rocket link" steering link in the release points when steering left and right. The asymmetry is caused by the angle at the rudder horn from the rudder hinge axis to the attach point for the steering link being a different angle than the angle at the steering arm from the tail wheel pivot axis to the attach point for the steering link.
After some discussion with Darwin Barrie at JD Airparts, he arranged to make a modified steering arm. I spent a little while doing some trig and analytic geometry to come up with a length and sweep angle of the steering arm that would produce a symmetrical release action to the left and right, and have both directions cause release of the tail wheel lock just at the extreme deflection of the rudder. Darwin sent me the the new steering arm and a longer steering link to test out. Here are some pictures of the installation.
I have not been able to fly this installation yet because of weather, ongoing condition inspection, and some other activities. But I will report back here as soon as I can fly with it. I can tell you that on the ground, if you pull the rudder all the way to the stop, and put pressure on the tail wheel in the direction it would feel if steering, it does NOT release. Same left and right. If you put the rudder all the way to the stop and put pressure on the tail wheel in the direction to make it swivel intentionally, it does release. Same left and right.
You can also see that I substitute a normal rod end with an AN3 bolt and AN970 washer, plus some of the rod end spacer washers that Vans sells, in place of the integral rod end + stud that is supplied. This insures that the rod end stays captive in the very unlikely event that the bearing fails.
So I am pretty optimistic that this will be a nice improvement to the steering link system for those that like it. The steering link system is quicker steering than chains or cables with springs and a little slack, and arguably not as rugged as cables with springs. So there is still room for personal preference here. But for those of us that like the quick, positive steering feel, this new steering arm should give you symmetrical behavior.
