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Technical Tidbits

Modifications for the AAF Type A7 Mag Switch

A7 Switch

Back in the mid-1990s, Tom Baker brought a Taylorcraft to the EAA Fly-In that was so good it won the Grand Champion Classic award. It goes without saying that the airplane was neatly done, but one little modification in particular really caught my eye. The AN AAF Type A7 magneto switch (see photo) had been changed in a very clever way - Tom had hidden a modern keyed switch right inside the handle of the original switch!

Here are a few shots of Tom’s modification. I’ll apologize in advance for the poor quality of the photos. They were poorly shot by me on slide film a long time ago!


Baker switch with knob
First, the standard looking AAF Type A7 with the nice large knob that has a handle. While the exterior portion of these switches is nearly bulletproof, the interior components are subject to wear and will eventually be unserviceable.


Baker swith no key
With the knob removed, the modern key magneto switch is seen. The guts of the original switch are removed, leaving only the faceplate and the knob. With a new switch without a starter position (one that reads: OFF-L-R-BOTH), the faceplate can be left as is, because the markings will match. Otherwise, the starter position lettering must be added.


Baker switch with key
The hidden secret to the original switch knob, the key. The modern switch’s key is trimmed so that it can be carefully brazed to the interior of the knob, after the original shaft has been removed. The stamped steel knob lends itself well to the brazing process if the key happens to be brass or plated brass. Measuring the height of the interior of the knob will give an approximate height of the top-of-the-trimmed-key-to-faceplate distance. A final trimming with a fine grinder will allow you to put the knob in just the right location above the faceplate, and holding the knob and key with a temporary jig will ensure the key remains centered and vertical in the interior of the knob during brazing.

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