Horizontal Stab side play

[skywagon8a]

I made nice .115 bushing shim spacers,. Measure with a caliper and have them machined out of chrome moly. Keep your same holes. A little more work but its nice when completed. 1600 hours later I'm ready to make some thicker ones.

It might be advisable to make the spacers out of a sacrificial materiel rather than wearing down the wrong parts. Bronze?

 

[Fortysix12]

Good Point.

 

[Steve Pierce]

The issue is the paint and fabric left on the ends of the stabs when covered and painted. I have had to change the liner tubes on an airplane I rebuilt because the paint and fabric wears away in short order and then you get the play. Have seen it on new Cub Crafters stuff quite a bit. I take a flat file and clean the ends of the stabs where they but up to the carry through tubes, install the tail brace wires and have someone help hold the stabs tightly together when drilling the liner tubes. Have not had the slop issue down the road when I did this. Have also not had any issues with the safety wire. I have three different sizes and one usually fits well and takes out the slop. Worn elevator bushings aren't usually to tough but worn jackscrew ears and yoke are a pita and expensive and that is the end result if left to unfixed.

 

[12Geezer2]

ag-pilot----Thank you for the post----geezer Dan

 

[behindpropellers]

It is in one of the PA18 inspection videos I put on YouTube but basically find the right size safety wire that fits the gap, twist it where it is in the gap, put a courtesy curl on the twisted end and tuck it underneath where it is not seen and someone won't get snagged on it. I just happened to have a PA12 in here that I did it to. Here is a frontal picture.
View attachment 54417

Steve,

I have a ton of respect for you. I would be very concerned with the safety wire filling the gap. My primary concern is the vibration which leads to radial erosion of the liner tube, thus creating a point of failure. To be honest, I don't think a bit of play is bad in this location based on how the jackscrew moves coupled with the non-precision alignment of the parts associated with it.

Tim

 

[mam90]

Been using safety wire since 1978. Haven’t seen a problem.

 

[Steve Pierce]

Steve,

I have a ton of respect for you. I would be very concerned with the safety wire filling the gap. My primary concern is the vibration which leads to radial erosion of the liner tube, thus creating a point of failure. To be honest, I don't think a bit of play is bad in this location based on how the jackscrew moves coupled with the non-precision alignment of the parts associated with it.

Tim

I haven't seen any issue but put a lot of thought into what you have pointed out. I don't think the safety wire really gets tight around the liner tube. The tube is 4130 Type N which is then hard chromed and centerless ground. Do you think the safety wire is harder that the tube? Also do you think the wire would wear vs the back and forth of the horizontal stab and the carry-through tube. I have done this on a lot of airplanes over a lot of years and if it is an issue I need to correct them.

 

[dirthog4]

Safety wire works so do shims. But if you take it apart to put shims in might as well put new tube in. Or it's just a jury rig.

 

[Fortysix12]

So got out the parts manual both old and new(1988). Both Figures, 42 show a part number attached here. It seems when I was assembling my airplane the tube was machined from heavier gauge material as specified and the bronze bushing omitted. What do the experts say on this, notice the specifications of the bronze bushing View attachment A3310071.pdf View attachment NL 14177-000.pdfView attachment NL 86062-80 .pdfView attachment Fig 42 Parts Cat.pdf

 

[BC12D-4-85]

Here's lots of choices in safety wire - hard to soft> https://www.mcmaster.com/safety-wire/

Gary