Thorp Air Command - T18.net

Ok guys,

I think I got elevator trim all together. Thanks again to David Neustel in Newsletter 93 and for John Thorp's dwg 701. John's flying tail is a fascinating bunch of parts to watch; linkage is a classic 4-bar mechanism. For any who care, I can share a little: Length of the tab arms (the one's bent for adjustment) will control overall amount of deflection (range). The dwg says to weld the clevis to get necessary length. The angle that they're bent (assuming jack screw & nut at mid-stroke) will help center or bias the range of motion (neutral stick position - dwg 701). The need is to set it for equal deflection both directions. Within reason, length of the coupler (the flat link) will do the same thing.

I added limit switches to mine and a few indicators, just cause I like to know where it's at. I haven't flown this yet, and I know it can be serious; just so I don't get any surprizes I thought I'd ask those who know:

1.) I haven't found it documented, but I think it ought to be written down someplace: According to per plans design, the nose will pitch up as the nut moves forward on the jack screw, right?
2.) Unless I cut and reweld the tab arms I get about 18 deg. deflection on the tab, rather than 20 degrees as on dwg 701. Is there a bad need for full trim, or should I leave well enough alone?

BTW, anyone travelling through and would like to pick up a passenger (me) to one of the upcoming events, please let me know. At least stop by for lunch or say hello.

Tryin hard to get it done.
Les Krumel, Albuquerque

what are you using for your trim indicators ? I have been flying with out an indicator for the last 14 years care to share?

lance

Les: I would say if you have the stab and the tabs within a degree or two of the plans , I would hold off making any adjustments . IMHO .

RB

Lance, probably most folks go without indicators for trim. That's just something I thought I'd like. It just cost me a few microswitches and a few LED's on the panel... Les.

Les, did you draw a diagram of the circuit ? how many leds did you use and how did it work out for you?I have been thinkeng about this for several years.

thanks Lance

Not sure how Les did his for the stab , but I put in an indicator lite for my RAC rudder trim. You can see the DPDT switch and green led lite just to the right of the stick . When the rudder trim tab is centered the lite is green . Just gives me some indication of tab displacement.

RB

Lance, this isn't totally the way I did mine, but you might try this if you want trim indicators. 22 gage wires are pretty small but good for LED's. LED's come in various brightness depending on current. I think the diodes on the motor circuit are how Frigelli motors with built-in switches are wired. Not enough torque for pitch trim but some guys use them for roll... Les.