Trim adjustment

[mike bc12d]

The trim on my BC12D seems to want to slip and get out of adjustment. The pulleys look like the original ones and I was wondering if replacing them would help . What would be the part numbers if so an what is involved to change the rear one out, the front looks like I will have to pull the headliner loose to get to it,maybe time for that new headliner.

[Dick Smith]

Re: Trim adjustment

Go to this link and familiarize yourself with the info that Rob Lees pulled together: http://vb.taylorcraft.org/showthread...=trim+slipping Dick

[mike bc12d]

Re: Trim adjustment

Thanks I found several links about the adjustment after I posted, thank you again for your reply, looks like I can go and play a little in the hangar tomorrow and see if incan get it set correct, I asked a buddy to see if his kid still had any violin rosin to put on the wire that was also suggested .
Thanks again
Mije

[Hank Jarrett]

Re: Trim adjustment

There are several threads here on trim system problems, but a quick few tips.

1) NEVER turn the trim crank with the elevator far from neutral. It causes the system to slip just like yours is. The cables and pulleys just can't handle the angles involved.

2) Make sure you have the crank threads in the center of the travel with the tab neutral. Turning the crank after the system hits the stops is a guaranteed way to make the cable slip.

3) Check the spring tensioner and make sure it doesn't hit the guides and is centered between them in the tail when the trim is centered.

4) NEVER, NEVER, NEVER force the crank! If it is stiff, STOP TURNING IT till you know why it is stiff!

If you get all of this done and it still is slipping, you can rub Violin Rosin on the cable and work a little into the pulley groove. Got to a music store near a high school and see if they will save you a piece that is worn out from the music guys. They will usually just give it to you. IT is VERY sticky on the cable and in the pulley groove.

Hank

Never would have thought playing in an orchestra 45 years ago would come in handy with antique airplanes!

[mike bc12d]

Re: Trim adjustment

I got everything fixed up good now, I bought the Rosin at the music shop the lady just looked at me funny when I told her it was to fix an old airplane. An interesting thing I found on my plane was the stop on the cable. I don't know if all crafts are like mine but the stop was on the pilot side cable and would only stop at the forward (nose down) position, you could by mistake crank it the other way (nose up) and it would go so far with tab movement that it would hang in a position with about 40 degrees of movement and you had to us a lot of forward pressure on the yoke to keep the plane level. That is when I saw that if the stop was on the cable on the co-pilot side that it would go to the back and hit a guide tube there and stop with the approx. 25 degrees of movement, so you might want to look and see if any other planes have this problem.
Mike

[Carrieve]

Re: Trim adjustment

Many years ago I had the "normal" trim problem, meaning slipping, etc. I rebuilt everything and after 25 years of flying the old girl I rarely have to turn the trim more than a half a turn in either direction. I only trim when in cruise to compensate for fuel load and baggage. So far I have never had a problem. Hank is right, if you feel opposition, STOP.

[M Towsley]

Re: Trim adjustment

I use 2+ turns while setting up for landing, that is where you will find if you have a trim problem. Half of a turn isn't much of use.

[cvavon]

Re: Trim adjustment

My next mod on 26658 will be electric trim.I will use the servo off of a Cessna sky catcher the company that made the servo also has all the other things to make it work led indicator and rocker switch and wire loom to hook it up the total weight is 1lb 2oz for all the parts, my estimate on the weight of the stock trim system is between 3or 4 lbs a savings of 2to3 lbs but no more slipping cables or stuck trim tabs and a weight loss that is good.I have talked to me go to guy at the Nashville FAA and he thinks he can field approve it for me will send paper work off this week and see what happens.

[lawheelock]

Re: Trim adjustment

I hope your FAA guy will like your proposed electric trim and give you approval.
You may or may not be aware of an add on electric trim system that a gentleman by the name of Norm Smith, PhD, and Mooney owner got STC'd for older Mooneys several years ago and could be used on either rudder or ailerons. It probably would not have been practical on the unique elevator trim system that Mooney uses, which pivots the entire empenage.
I installed one of the systems on the left aileron on my '65 Mooney M20 C. It consisted of a small tab hinged to the rear of the aileron and operated with a small pushrod of piano wire (or stainless, 1/16" welding rod) from an in the wing mounted small dc motor and miniature gearbox(looked like out of a toy race car) that also had a potentiometer to feed back position.
In the cockpit is mounted a 2 1/4 inch zero centered meter with a rocker switch under it for left-right trim. It is a very light, small, and ingenious system and the fact it was approved on a much faster aircraft than a T-Craft should give confidence that such a system could be approved.
Norm Smith has passed away and I don't know if anyone has purchased the STCs from his estate, but it really worked well.
In your case, the trim tab on the Taylorcraft is much larger than the little tab put on my Mooney aileron and will need a larger motor, but the concept is sound.

Larry Wheelock, '46BC12D under repair, '46 Lyc 180 powered Stinson 108 and '65 Mooney M20c, A&P, IA

[cvavon]

Re: Trim adjustment

Larry first Thank you for the kind words. The servo is a rack and pinyon type and is enclosed so it is water proof the trim tab on the cessna sky catcher is some what larger then the tcrafts. It is less then 1 in thick and a little over 2 in square it will fit inside the elevator on a bracket that will bolt to the bell crank bracket in the elevator and the push rod will hook to the existing lever on the trim tab.the servo has 1.2in of travel threw its cycle witch will give me the 25 deg down and 30 deg up travel. also the servo has a reastat built in that sends a signal to a led indicator in the plane. Its operated with a self canceling rocker switch that will mount in the panel close to the throttle.This whole system only weighs 1lbs9oz that includes the wire to hook it up.The only thing i have not got a weigh for is the 1amp circuit bracker.

[Marv]

Re: Trim adjustment

Charles it looks like a good deal. If you lose at the most 2 lbs you will have the same useful load. LOL

[cvavon]

Re: Trim adjustment

i HAVE LOST 18 LBS SENSE OCT 30 2013 WHEN THEY PUT IN MY NEW KNEES THE TRIM WILL KOCK OFF ABOUT 3 FOR A TOTAL OF 21 LBS IF i KEEP GOING WE WILL BE ABLE TO HALL TWO OF US AND THE CAMPING GEAR AND A bARBEQUE GRILL WITH 24 GL OF FUEL?

[Marv]

Re: Trim adjustment

Looks like i better get started losing a lot of weight.LOL