One of the big problems I ran into in building this with aluminum is handling the potentiometer D shaft. I'm really new at machining and I was having a hell of a time finding information on how to reasonably create a D profile hole in an aluminum shaft. With the 3d printed part you just print it as a D. Boring out a D profile in an aluminum shaft is not a trivial task. I hacked my way around it by using a set screw, but it's not ideal.
This, combined with the possible issues of using the potentiometer shaft as a load bearing component, had me thinking of other ways to handle this. I'd seen some information about hall effect sensors and have been researching those trying to find an affordable solution. Many of those chips, particularly those meant as absolute rotary encoders, aren't inexpensive and the breakout board or development boards with them installed are either a DIY project or around $20 each. That'd be a pretty big cost jump.
But today I came across this: http://www.mycockpit.org/forums/showthread.php?t=22267
This guy is replacing a potentiometer with a simple hall effect encoder chip (cost around $1.25 each) and two magnets mounted to the shaft. It's a simple 3 pin connection like a potentiometer and a simple solution, no more complicated board really required. It covers 180 degrees of rotation, far more than the around 90 degrees required by a delta throttle pivot arm.
So my new design will likely be a solid 3/8" shaft with a 3/8" x 1/4" bronze sleeve bearing in each upright for the shaft to ride on. The pivot arm will bolt down securing the right side. a 3/8" ID x 1/2" OD x 3/4" LG sleeve bearing will be placed on the shaft for the spring to ride on. Even though this exceeds the maximum shaft OD for the springs there's plenty of clearance for our required range of motion. the 3/8" shaft will extend on the sensor side by 1/4". I'll machine my own shaft collar to secure this side including pockets for 2 1/4"x1/4" neodymium magnets.
With all the extra bearings, sensor and magnets this will be a bit more than a potentiometer's cost, but not by a lot and will give a secure and smooth operation with a high degree of accuracy and little to wear out.
Thoughts?