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KAP Rig to Pole Adapter

Posted by Tom Benedict on 01/06/2014

In my previous post I described some bits I’d made so that I could swap a rig from one suspension to another. I did this as the first step in getting into pendulum design. I needed a way to move my rig from a Picavet to a pendulum to whatever design I wind up testing so I can compare the performance of each. But even as I was making them I knew I wanted a mating part that would let me flip my KAP rig upside-down and mount it on a pole. Yesterday I got the chance to make the new pole head:

Pole Head

With a KAP rig most of the forces are axial: pulling up or down. With a pole rig the forces are mostly axial, but if for any reason the pole leans to one side the forces become radial: pushing out sideways, wanting to bend things. I knew the joints on the KAP adapters I made were plenty strong, but I wanted something a little beefier for the pole.

The core of it is one of the KAP adapter bits I’d made previously. The outer shell is the new part. It started life as a length of 1″ diameter 6061 aluminum. I bored out the bottom to match the depth and inside diameter of the original pole head. Once that was done I flipped it around. I turned the remaining outside diameter down to 0.6″ and put a 45 degree taper to transition between the narrow and wider parts. There’s a good bit of metal between the bottom and the taper at the top, so it’s plenty strong. Once the outside was done I drilled the inside 0.375″ to match the KAP adapter bits and drilled a #8 clearance hole between the upper and lower halves of the thing. The only step left was to cross-drill the lower half with a 0.128″ hole for the rivets. The original pole head had nice flats for the rivet heads, so I spotted each hole with an 0.250″ end mill to make a flat.

The 0.375″ hole on top is a close fit for the KAP adapter, but not so close that I had to force the part into place. I put some blue Loctite on the screw I used to secure it to the pole head, so it shouldn’t go anywhere. Once the head was pop riveted to the pole, the work was basically done. But I abuse my pole, and I knew the head would take damage if I didn’t do something to protect it. So I chucked up a piece of PVC pipe, faced off both ends, and used it as a cap. With the lock screw backed out just right, the cap is a snug fit and won’t fall off in transit.

I really wasn’t planning on pursuing this during World Wide KAP Week. Not with so many great places to fly. But weather is weather. Sometimes it cooperates, sometimes it doesn’t. The winds in town were gusting so I ducked into the shop to make this while I waited for conditions to improve. This morning the sun rose to a clear sky and almost zero wind. Here’s hoping there’s something to fly in this afternoon!

– Tom

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