Thorp Air Command - T18.net

As I said Todd, it is ok to support it more. I highly recommend you do that. It is flopping because it is not supported. Since it is not supported, the natural bow in the tube will spin around in the tail. It may catch on something. The only way it can flop like that is because it is binding at either end because it is not supported where it should be.
Go for it.
Cubes

Sounds like you've got it all sorted Rich. At the moment mines attached with clip on nut things that are kind of like a paperclip on the top and sides, don't have a clue what they are called but they work well. Only problem is that the rear panel mounts behind the bulkhead and there is a lip on the inside of that same bulkhead so the panel can't be mounted to the front. I might have to look at cutting it in half and riveting an overlapping panel to the center with some floating nuts. Should solve the problem of removal and installation a new support behind the baggage area.



Cheers again Cubes for your insight. I went and checked the trim again today and when you turn the trim wheel you can hear the rod flicking around and even impacting part of the fuselage so it's not ideal atm. I can't believe it's been like this for 40 years without a problem or anyone changing/fixing it. It was one of the first things on a very long list of repairs/changes at the new maintenance shop.

Cheers all

As a reminder for those still building, reverse the flange on the bulkhead at the aft of the bagage compartment. Sure makes it easier to attach the panel.

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Bob Highley
N711SH
SN 835
KLAL

The paper clip things you are referring to may be tinnerman nuts, http://m.aircraftspruce.com/catalog/hap ... ckkey=5485 and they last a long time if the proper screw is used. As a matter of fact, they don’t perform to bad even if the wrong screw is used. I have been thinking about camlocks or zeus fasteners myself so I don’t have to chase the screws I will drop.

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Thorp T18
O-320-B3B (160 HP)
68x74 Sterba Propeller

"The joke in aviation is, 'If you want to make a million, you'd better start with £10m.' " -Bruce Dickinson

I'm late in this thread but my electric trim motor is mounted in the bulkhead just aft of the rear baggage bulkhead. Quite long shaft. When I pull my baggage bulkhead for new vinyl I'll check to see if there are supports on the shaft. I don't recall seeing them when I was doi maintenance. Maybe il find a picture from when I was in there. Mine operates without issues minus being really slow.

Here's a photo of my rear baggage bulkhead, the floor of the baggage compartment is level with the top of the tunnel. The rear bulkhead is mounted to an extra flange that is attached to the back side of the frame. Also note on the left side the support for the trim tube, it is a nylon "adel" clamp, there are similar ones on the right supporting the wiring and static system tubing.

Wish I had a better photo but this will have to do.

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Bruce Finney
N18JF T-18C #262
Yelm, WA USA

I've read a few of the trim threads. I have manual trim with the cable that runs from the top of the tunnel approximately directly under the engine controls, with a crank mounted horizontally on the tunnel. Something is worn in the system, as it works smoothly on the ground, but at cruise loads on it, the crank will turn, but nothing happens. I'm suspecting the cable is shot.

To replace the cable, I believe I'm going to have to cut an access panel to get at the jack screw. If I've got to go that far would I be better off installing electric trim? There's a thread with pix of an elect trim install but it appears to have occurred during construction, not on a flying airframe.

Opinions and experience, please.

Thanx in advance

Rap

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Base: KALX
N8786
SN 929

I believe you may have something unique to your bird if you have a cable controlled pitch trim system since the drawings show a shaft driven system. Without more info as to the type of system installed, I can only guess that maybe you have an endless loop style cable similar to what Piper used on some of their earlier aircraft and was notorious for slipping under a load (I had to reduce speed in my PA-20 to 80 mph to trim it). Otherwise I think you are probably looking at a stripped gear or broken pin on a sprocket that grabs just enough to work without a load.

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Thorp T18
O-320-B3B (160 HP)
68x74 Sterba Propeller

"The joke in aviation is, 'If you want to make a million, you'd better start with £10m.' " -Bruce Dickinson

Jeff:
No, the system is a since cladded cable much like a tach cable only much longer, and very much like the drawings except the input point is a horizontal crank handle. If I reduce speed to about 100mph as you indicate, I can get the trim to move.

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Base: KALX
N8786
SN 929

Do this and enjoy: viewtopic.php?f=4&t=6201

Graingers no longer has the 2L009 motor, replaced by 52JE52 and the cheapest place to buy is Zoro Industrial their part number is G6617810
Just ordered one for Duke's S18 trim system

I understand now. I wonder if the cable could be coming apart and/or not getting full engagement. I would try to break the system down into sections to see where the problem is then decide how best to proceed.

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Thorp T18
O-320-B3B (160 HP)
68x74 Sterba Propeller

"The joke in aviation is, 'If you want to make a million, you'd better start with £10m.' " -Bruce Dickinson

I saw that, and it looks doable. It appears I must de-rivet the aft skin or cut an access panel to get at the tail section.

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Base: KALX
N8786
SN 929

If it were me, I would look to see if the issue was somewhere in the area of the trim system inside the cockpit, around the trim wheel itself. If your problem was there, I would just fix it and keep the manual trim. But, if its not there, and you gotta drill out the rivets on the skin to get to the jack screw area to assess your current issue, I would 100% go ahead and install the electric elevator trim. Its one of the best mods I've ever made to my plane. I made this change because my manual trim wheel was slipping too! Maybe my favorite mod, was the addition of aileron trim. Talk about HUGE improvement over the original design of dragging that flap. These 2 mods also got all that junk (johnson bar and roll trim knob) out of the cockpit which, i felt, gave me more room.

It’s very doable without having to deconstruct the aft end of the airplane. The most difficult part will be getting yourself into the back of the fuselage. The old trim stuff gets removed, a uninitiated makes the center hole larger. The 4 holes for the mounting of the motor. 2 limit switches...and I can GRT you the parts list for the actuator tube I used to carry the motion from the motor to the trim actuator. Readily available at any hobby shop that carries RC car stuff. The motor Bob highley recommends has good torque and works well. I converted the trim on 66WT and 218TH has the same trim system.
Good luck, you will be happy with the results. Oh, I put a toggle switch on WT right next to the throttle for ease of trimming. There should be a photo of that in the archives under 66WT coming back.