Sunday, December 6, 2009

Elevator Horn Material Thickness

I've been working on how to make new elevator and rudder control horns. They are not used on the Waco Ten so there aren't many people to ask. There is one on each elevator and the rudder. They are stamped as 2 metal shells and welded together along the edge to form a rigid streamlined shape. There is no drawing I've found for these and they are more complex than almost anything else on the plane so I believe they were simply purchased as new WWI surplus. We built our Fly Baby with a lot of WWII surplus parts from the A & N store before they discovered Levis and Nike.

The outside shape was easy and I'll cover that in another posting. The bigger problem was the metal thickness. I have one horn on the rudder which is in good shape and one on one elevator. This elevator has rust problems but the horn is usable so I didn't want to damage it to measure the metal thickness.
Also at each end there is a piece of steel welded in the tab end making the tab 3 layers thick all welded along the exposed edge. The three layer tab measured .110" thick which leave a couple possibilities for the 2 shells and the inserted tab. The most likely combination was all three being 20 gauge steel (.o359").

The idea was to make a go-no-go gauge from 2 pieces of welding rod with feeler gauges taped between them. with this the thickness of the tab insert could be measured and the thickness of the shell becomes half of what's left from the .110" total

We don't need an exact measurement just close enough to determine the gauge size of the steel. By adjusting the stack of feeler gauges between the wires in .oo2 increments it was easy to show that the steel is 20 gauge.

I've included a video which explains this better but even at the lowest resolution it's 62 mb. I have a higher resolution version but it's 229 mb. If you have a high speed connection check out the video.

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