Crank Handle

Bob Kuykendall

A few people who have seen the pushbutton-release flap crank handle in my HP-11 have asked for drawings for it. I pretty much made the thing up as I went along, so there were no drawings.

However, since I'm making a new flap crank for my HP-18, I finally sat down and did a set of drawings for the thing. Actually, this is a slightly simplified version, having fewer custom-made parts and requiring less in the way of precision tooling.

The way it works is a bit of a reverse from what you might expect. The button is actually fixed, and when you push it with your thumb the handle your hand is on slides. That sliding motion retracts the pin that locks the crank to the degree plate (not depicted).

The real credit for the basic device goes to the designers of the PIK-20B, where I first saw one of these. I don't actually know what's inside the PIK-20B handle, but it uses the same fixed button/sliding handle, so it can't be that different on the inside. I know that at least one of you out there has an HP-11 that has been retrofitted with the entire crank mechanism from a PIK-20B.

Here are links to the drawings for the crank handle in Adobe Acrobat format:

Crank Handle Design
Push-Button Assembly Detailed

One thing to note, the handle depicted in the drawings has a 3" swing radius, whereas the typical HP has a 3.5" swing. I can get by with that shorter swing because I've got a double-geared mechanism. But you can just as easily use this handle with the 3.5" throw.

The usual disclaimers apply; these are aircraft parts, and though they are parts of a secondary control system are still rather critical in nature. Use these drawings and the parts represented thereupon at your own risk.