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We have almost completed the installation of the trim system that eliminates the trim tab servoing as the elevator is moved. We basically followed Pat's installation with a few minor tweaks.
Starting up front we had to decide what to do about a trim control. We wanted it to be less sensitive than the factory system and I wanted a crank like what is found in a Stinson or a Pacer. We came up with this:
Untitled by Jon Whee, on Flickr
It uses a 6 tooth front sprocket off a pocket bike (factory wheel uses a 9 tooth sprocket). The sprocket is welded into a tube which is inserted into a larger tube with a nylon bushing. Pretty basic. I'm really missing my Luscombe so we found a Luscombe trim handle and will be fitting it onto the assembly and that will complete the control. It takes 3 revolutions to go from full up trim to full down trim.
Routing the control cable took a little thinking because the stringers are really close to the high spot in the rear cabin area. There was not room for a regular fairlead here so we welded on a couple tabs and will use a HDPE skid plate for the cables to rid on in that location. Two more fairleads were added behind the cabin area.
Untitled by Jon Whee, on Flickr
Untitled by Jon Whee, on Flickr
Next we built the trim horn and mount.
Untitled by Jon Whee, on Flickr
We used the factory trim horn with nylon bushings installed. We drilled a 1/4" hole through the center for a mounting bolt. The horn bracket is made of 0.063 4130 as is the cable retaining bracket. Obviously we didn't want any flex in the system. We mounted the push/pull cables (A920 cables 60" long) closer to the center line because they laid in there nicer than when mounted to the side. We also didn't want them rubbing on the elevator cables or the fabric.
A couple tabs were welded in further back in the tail to help hold the push/pull cables in place.
Untitled by Jon Whee, on Flickr
This video shows the original install which caused the elevator rib to twist. I didn't want to move the horn on the trim tab so a 3" long cable retainer was welded to the elevator rib. The cable retainer is made out of 0.032 4130 bend into a "U." This long retainer kept the cable inline with the horn but the moment it created about the rib caused the rib to twist significantly.
To fix the twisting we cut off the horn on the tab and moved in inboard as far as possible. This allowed us to shorted the cable retainer to 7/8" and reduced the moment about the rib enough that there is zero twisting. I'm very happy with the outcome.
Untitled by Jon Whee, on Flickr
Huge thanks to Pat for sharing his ideas. I'm really excited to see how the plane feels with this system.
Starting up front we had to decide what to do about a trim control. We wanted it to be less sensitive than the factory system and I wanted a crank like what is found in a Stinson or a Pacer. We came up with this:
Untitled by Jon Whee, on FlickrIt uses a 6 tooth front sprocket off a pocket bike (factory wheel uses a 9 tooth sprocket). The sprocket is welded into a tube which is inserted into a larger tube with a nylon bushing. Pretty basic. I'm really missing my Luscombe so we found a Luscombe trim handle and will be fitting it onto the assembly and that will complete the control. It takes 3 revolutions to go from full up trim to full down trim.
Routing the control cable took a little thinking because the stringers are really close to the high spot in the rear cabin area. There was not room for a regular fairlead here so we welded on a couple tabs and will use a HDPE skid plate for the cables to rid on in that location. Two more fairleads were added behind the cabin area.
Untitled by Jon Whee, on FlickrUntitled by Jon Whee, on FlickrNext we built the trim horn and mount.
Untitled by Jon Whee, on FlickrWe used the factory trim horn with nylon bushings installed. We drilled a 1/4" hole through the center for a mounting bolt. The horn bracket is made of 0.063 4130 as is the cable retaining bracket. Obviously we didn't want any flex in the system. We mounted the push/pull cables (A920 cables 60" long) closer to the center line because they laid in there nicer than when mounted to the side. We also didn't want them rubbing on the elevator cables or the fabric.
A couple tabs were welded in further back in the tail to help hold the push/pull cables in place.
Untitled by Jon Whee, on FlickrThis video shows the original install which caused the elevator rib to twist. I didn't want to move the horn on the trim tab so a 3" long cable retainer was welded to the elevator rib. The cable retainer is made out of 0.032 4130 bend into a "U." This long retainer kept the cable inline with the horn but the moment it created about the rib caused the rib to twist significantly.
To fix the twisting we cut off the horn on the tab and moved in inboard as far as possible. This allowed us to shorted the cable retainer to 7/8" and reduced the moment about the rib enough that there is zero twisting. I'm very happy with the outcome.
Untitled by Jon Whee, on FlickrHuge thanks to Pat for sharing his ideas. I'm really excited to see how the plane feels with this system.
) . I also like the stinson style trim crank. Nice job all away around!
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