smith cub trimm

Hi All. Have been working on getting the overhead trim system on the smith cub installed. Got it up and running, works smooth ect But..... noticed that when the trim is cranked about three quarters of the way up ( up being the leading edge of the stab) the cable starts to slip, If I put just a bit more spring tension on the system it seems to work fine. My concern is the airloads binding the system. Any thoughts or just get a slightly heavier spring? Thanks
Bill

Where is it slipping at, the front drive area or the rear?

Pokey

More than likely the lower bushing for the jackscrew is not lined up perfectly with the top bushing and the jackscrew is binding. I had the same problem. You may have to cut the lower bushing off and reweld it in place. If it is not perfect on the ground it will be worse in the air. Just my 2 cents and I could very well be wrong.

Good luck

Bill

You might want to also make sure you have all pieces in place and tensioned. I have seen the Smith Cubs bind at the jackscrew and not able to move at all with all the stabilizers level and the flying wires tight! What an unpleasant surprise after everything is covered...

Brent

I'm not sure if Bill's lower screw bushing is out of alignment, but it sounds like it moves okay initially.

It is completely acceptable to get good alignment by inserting a piece of heavy wall tubing that sleeves perfectly inside the bushing and levering on the tubing slightly for a trial and error fit.

I would also check that the threads in the yoke are good. I've seen some burrs on the Smith yoke I have here.

DAVE

smith trimm

Thanks for the response. Bill Rusk I did have that problem you describe however I corrected that by re welding early in the build process and now have great alignment. The jack screw turns without inpediment. The front double grove pulley is the one that is sliping and only in one portion of the range of travel. If I increase tension in the system by using a slightly stiffer spring at the rear I can make the problem go away and it feels smooth through out the range of travel. My concern is that all this is happening in a non air load enviroment. Will the sliping be a issue, even thorough it feels smooth now with a airload on it? The 100 dollar question. When I put some resistence on the stab and then trim it slips again. Thanks for the reponse.

Mine was doing the same thing. I adjusted the flying wires a little ( trial and error) and it was much better. I now have 80 hrs and have never had an inflight problem.
Ron

Having built a couple of smith cubs there are two fixes to the problem. Call steve tubbs at performance air. He can give you both fixes. All the trim systems that they have installed seem to work just fine. At first they had the same problem with all of them. This is one reason that they cut the rear mounting point of the horizontal stab. It's moved up and resquared. Also the jack screw tower isn't perfectly sqaure. You can move it or open up the holes to where the front horizontal tube mounts to the jack screw. It's worth the call to find out exactley how to fix it. 208-455-7400. Be paitent on the return call he's quite busy but you will get an anwser.