Thorp Air Command - T18.net

Guys,

I installed the Trusty spring and AP tail wheel this past winter and last night I had my first chance to test it out. I also have the Tom Hunter fairing on the assembly as well.

1) The ground handling seems fine but I get the impression that the tailwheel releases before the rudder hits it's stop.
2) Once the tail wheel releases it has a lot less resistance or stiffness than the previous Matco set up or even the Scott, I had on the Stinson. It feels like it's on ice. There is virtually no friction once it releases.
3) I think I have to check the geometry to confirm when it releases.
4) In the air at 2200 rpm, 24 ", 8.2 gph and 2000" asl my cruise used to be 157-158 mph. This has increased to 160-161 mph.
5) The runway this this time of year has some major frost heaves and the new spring definitely handles these bumps better than the old flat spring. It's not as stiff and the tail doesn't seem to get bounced as much.

All in all I am happy with it. If any of you guys have also noticed the release issue, I would be interested in the cure. My thoughts are that I would re-drill new holes in the rudder horn closer to the pivot, to decrease the angular movement at the wheel.

Best regards,

Jim Mantyla

Jim,
I think most of us decided that the wheel assembly, as it comes from the manufacturer, releases too early. If you search the archives of this forum, you should find a lot of info on correcting that. It involves a little minor machining, extending the arced groove that the locking key moves in. A milling machine is nice, but some have evidently made the modification with a Dremel tool. If you disassemble the wheel, you'll see what's needed. It doesn't take much, but you have to lengthiness the arc of that groove on both sides. I have the flat spring, but the locking mechanism is the same on these Aviation Products tailwheels.

_________________
John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

Hi John,

Thanks for the quick reply. I was out to the plane tonight and made a few measurements and found the following:
1) The rudder moves 30 degrees side to side and the tail wheel horn rotates 45 degrees each way.
2) The distance between the linkage holes on the rudder are 8" apart and on the tail wheel they are 6" apart.
3) I laid the geometry out on the CAD proogram and found that moving the rudder holes 5" apart will give me about 29 degrees at the wheel.

I will search the archives and see which approach to take. I do have access to a mill since I run a mold building shop here.

Thanks again,

Jim