What is this thing and what will it be used for?

You’re looking at a right-angle drill attachment.

This little device performs the same function as a 90° gear box.

…specifically, to accept power (torque) onto the input drive shaft and to turn the direction of drive through 90 degrees (a right angle) to the output drive shaft.

The drill attachment achieves this functionality in the same way a 90° gear box does — through the use of two bevel gears.

Using this apparatus is more cost-effective and practical than building my own 90° gear drive system or gear box. And why do I need a 90° drive system? Because the power from pedaling the trike [where the sprockets are aligned vertically] needs to transfer to the rotor blades of the Flying Machine [where the rotor is aligned horizontally (or at 90° to the trike’s drive system)].

[Although, building a gear box would have been a fun project in itself; after noodling around with some designs and looking at the cost of supplies {gears are expensive!}, I determined that this piece of the Flying Machine project could best be attained with this right-angle drill attachment. Plus, I found one for less than $12. – Ed.]