Cloyd VanHook:
Anyone have any info on installing a PTT on the standard Beech yoke or in
the alternative where to get a yoke that will accommodate a PTT?
(Search strings: push to talk; push-to-talk; talk switch; yoke switch)
Editor:
Summary: The Beech yokes used on our planes consist of a welded-up aluminum tube core structure. This weldment is placed in a mold, and the ergonomic plastic is cast around the weldment, to provide the ideal shape. This is fact; I have much of the drawing data, and the part numbers assigned to each stage of the process. This is also why cracks in the plastic do not render our yokes unairworthy; the plastic is simply cosmetic/ergonomic.
The yokes come with translucent plastic plugs that cap the top holes. These have usually been painted over the years, and have often been crystallized by sunlight. I have seen metal hole snap-in plugs used, but I don’t think Beech ever used them. Having said that, I have found a lot of other anomalies apparently original from the factory; so who knows. At Sun-N-Fun I found what appeared to be a solid cast aluminum yoke that was shaped like ours (but with a different shaft attachment). It carried a PN for one of the old Beech Twin Bonanzas (50-series).
The Beech factory method for installing PTT switches was to pop off the top cap. The plastic or aluminum plug that caps the aluminum center tube, inside the upper cavity, got a small hole drilled in it. Another small hole was drilled vertically into the bottom of the yoke hub, aligned with the tubing. A small pair of wires was fished through for the PTT. A vacuum cleaner hose and/or an air hose can help with fishing the string/wires. The PTT itself was mounted in the left hand-grip, in a small hole, aligned with the trigger finger. In most cases, the PTT hole was drilled deeply enough to seat the switch, but with a shoulder to stop it from falling completely into the yoke cavity. The switch is usually just a friction fit in the hole; and the wires help keep it from working its way out. A smaller hole goes all the way through into the cavity, to connect the wires. At the bottom of the yoke, a connection is made to a spiral cable (‘coil cord’), which is usually clamped to the bottom hub of the yoke (and under the instrument panel at the other end).
This was the standard method used by the factory, and should be accepted in the field. In many cases involving autopilot disconnect and electric trim switches, a significantly larger hole was drilled in the pilot’s yoke (top and bottom), for the much larger wire bundle needed for the added controls. The wires used in coil cords are a very small gauge (24 gauge or even smaller); particularly when there has to be a high wire count for control of multiple items (autopilot, disconnect, electric trim, microphone). In these cases, it is better to strip back the coil cord so that the group of small wires can be fed up through the yoke to the switches.
I have seen some Skipper yokes that have a different configuration, with an exit hole drilled fore-and-aft next to the hub. I have also run across some yokes that apparently became blocked in the inner tubes, most likely during the molding process, and proved impossible to get wires to pass completely through; even though their structure was clearly the same.