Thorp Air Command - T18.net

Are the Lyle Trusty drawings for the aileron trim tab referenced in newsletter #129 stilll avialable? I tried the email listed for Mr. Trusty from the membership list in newsletter #122 but his email has changed. Any help would be appreciated. Thanks, Jon Linke, s/n 1321.

Jon,
Are you looking for the drawings detailing the trim tab itself or the trim motor installation? If it's the later, we have the Lyle Trusty aileron trim in N51863 per his drawings. I still have access to the drawings if you like but it will take a few weeks to get them (the owner of the plan set is out of town right now). I will say that although it's a really neat design, you'll save yourself a lot of work by just installing the RAC servo in the aileron and driving a tab with it. Bob Highley did a really great writeup on Aileron trim with the RAC servo. I'll see if I can dig that up.

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Lee Walton
Houston, TX
N51863,N118LW
KEFD

Aileron Trim
As installed on T-18CW
N711SH



Trim tab is about the size of a dollar bill. The general layout is the same as the anti-servo tab on the stab. As you can see, my aileron has folded trailing edges that keep the high speed forces light. The tab is folded out of one piece of .020 2024 T-3. There is a small sub-spar that the hinge is riveted to and the pin can be pulled from the end.



This shot shows the underside. The clevis is from a model airplane. The stock one from Richard Allen is a bit fat for my taste. The panel gives access to the servo, which is mounted on the panel. The wires lead out of the aileron spar to a plug on the rear of the wing. That

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Lee Walton
Houston, TX
N51863,N118LW
KEFD

Be prepared for a little sticker shock when you buy that new servo. They have gone up more than $50.00 (now $183.00) since I bought mine...T2-7A. 02/20/08. I went with the internal mount to protect the expensive servo from the elements. The servo is not waterproof. The T4-5 servo is $314.00 !! Aye' Carumba ![:0]

RB

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Rich, that's a mighty fine looking trim installation with the RC Allen Trim Motor internal. Jon was able to obtain the Lyle Trusty aileron trim drawings from Mike Archer. These drawings show an alternate method of driving the trim tab via a motor mounted on the outer rib inside the wing tip. I have had that set up on my plane for over 10 years now and it works extremely well. The cost of the little motor was perhaps 70 dollars 10 years ago. So, if you are of a mind to save some money on installing roll trim, following the Trusty Blue Prints is a pathway to economic frugality. However, the motor called out is going to be hard to find. It is a 12 volt motor with a clock work gear driving the output shaft at about 10 rpm. You do not want anything faster or you will not be able to fine tune the roll trim with the Trusty design. A creative person such as the typical T-18er will be able to find a suitable substitute for the motor. The plans show limit switches on the travel but I did not bother with them. I just look out at the trim tab as I push on the rocker switch. It hardly deflects at all as I adjust for fuel burn off or a passenger of more "significant" mass than the last one.

I'd like to put in a plug for adjustable roll trim...a darn handy addition to your plane and one you'll make use of each time you fly.

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Tom Hunter
805-202-4261

Thanks Tom. I know I'll use it everytime I go up. I feel naked without electric trim. [8)] I believe the Trusty system used the MAC (S9)/RAC T4-5 servo, which has a universal joint on the end. The T4-5 servo is the one that's $315.00 + tax + shipping ! Oh Baby ! If you can find any of those them there motors for $50.00, buy a gross !

RB

Rich,

Nope, the Trusty plans call out a neat little motor that was actually used on Drones in WWII and after. The reason I know that is that I contacted the company indicated on the plans and talked with them when I was making the trim system for my first set of wings...got to be almost 20 years ago...and they told me that their tooling was not so good any more and the guy who made them was near retirement. I convinced them to make me one by ordering 4 of them! I managed to destroy 2 fairly quckly...a clock work gear drive is not all that strong...( didn't really have to be for the intended mission of a drone) and still have one spare. However, as I said earlier, a resourceful person like most T-18ers will be able to come up with a substitute.

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Tom Hunter
805-202-4261

I think you guys are comparing apples and oranges. The RAC Servo motor we use for the aileron trim is ~160 (the entire trim "system" from RAC is ~310). When you get down to it the two systems cost the same (actually by the time you gather the ingredients for the Trusty system it may be more).

Price is really not the differentiator here, it's simplicity. Both in maintenance and installation. The Trusty setup is really cool but it's significantly more work (and more weight as well). I gave this quite a bit if thought ~ a year ago and ended up with the RAC servo. BTW if my dad were still around he'd argue with me on this one. He really liked the LT setup.

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Lee Walton
Houston, TX
N51863,N118LW
KEFD

Any consideration of a Firgelli 12v analog linear actuator in place of a RAC$$$$$ or clock work motor? Firgelli (and others) offer a variety of strokes, speed, strength, built in limit switches, and position sensors. The 4" stroke, 150lb, with position sensors might work well for electric flaps.

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[b]Terry[/b]

I flew this morning and was quickly irritated having to hold a slight bit of aileron control. I am curious about the size of the trim tab. I have heard a George Washington recommended. As yet I don't have electric trim, but I find that barely massaging the aileron trailing edge contributes quite a bit of roll. How much deflection of Mr. Washington is used in trimming roll for those passengers of "more significant mass?"

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[b]Terry[/b]

Terry,
About the most the little trim tab moves is 1/8th inch deflection in the most severe cases. Note: we are talking about a tab within the aileron, not hanging off the trailing edge.

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Tom Hunter
805-202-4261

You are on the right track, look at the micro miniature linears from Frigelli. They are around $80 and come in various CM travel

*** admin posted for Bill Williams ***

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Forum Administrator

Thanks Tom. I have seen the pictures of the "built-in" aileron trim tab and examined yours as well as some others. I had just never asked about the degree of deflection to accomplish the roll correction. I assumed it was very little. I will design a system to use a micro Firgelli linear actuator, either mounted in the aileron or connected via push/pull cable in the tip.

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[b]Terry[/b]

I have looked at the Frigelli micros and the shortest stroke is 10CM (3.92"). The deflection on my built in trim is about 2" travel,1" up 1" down. I have 16.5 gallons of fuel each side and on purpose run one tank empty to check the imbalance and had to hold about 2# stick pressure. The RAC mounted in the aileron seems to meet all requirements on travel, weight and speed and as you can see by the pictures is easily constructed to fit the aileron. The price is a little higher, but simplicity might weight out over engineering. You will need to use micro switches to limit the travel to about 1.5" travel. I do believe the linear will fit in the aileron and work well. Please keep the site posted on your progress

Actually for the aileron trim tab I was thinking of the Firgelli Micros L12S or L16S series. Strokes from 10mm to 140mm, 5mm/s (~1/4"/s) travel, 45N force (~10 lbs), 12v 2 wire F & R, built in limit switches, weight <60g, overall length 53mm+stroke.
http://store.firgelli.com/index.html

Is there any implications to the weight of the RAC servo mounted in the aileron as far as control surface balance? One engineer commented to me that he was concerned about flutter in the unlikely event the control horn or operating mechanism became detached.

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[b]Terry[/b]