Algodoo

pretty good concept but it's hard to read values.

Nice scene, but short explanation. What keys operate it? Do both mechanisms work together or do they both do the same thing? How does each mechanism work? What is the principle of operation? I know we can probably figure this out in time, but why not make it a little easier for us.

Great work once again.

@Kilinich: Agreed.

@s_noonan: To answer your questions:
- 1. Zoom out. Off to the right, you will see a blue-gray ball with a tracer on it.
Move it with the arrow keys.
- 2. They work independently.
- 3. Both have the same mechanism at their heart: two identical discs, each with an attracting circle and a repelling circle on opposite sides.
Left to their own devices, these would both line up in the same direction, with the attracting circles both pointing at the ball mentioned above.
As it is, however, two springs try to push them apart.
When the ball is closer, the attraction is stronger and they point in nearly the same direction.
When the ball is farther off, the attraction is weaker, so the springs can push the discs farther apart, or at least closer to the same direction.
The angle bisector between the two discs will always point at the ball.
The mechanism on the left efficiently uses pistons to achieve its effect- the arrow always points at the ball and as the ball gets closer, it pulls back into the mechanism.
The mechanism on the right uses C-gears. It uses two planetary gearsets (Hmm... cycloid gears could do this more efficiently...) to find the difference between the positions of the discs in the radar mechanism, leaving out the direction (there's an arrow for that), which then gets plugged into a dial.
The semi-planetary (after a closer look) C-gear arrangements behave much like the piston mechanism.
One arrangement is located on the the radar mechanism itself. This keeps the arrow on the bisector.
The other is responsible for the dial. It finds the difference between the two discs on the radar mechanism and thus controls the dial.

Again, interesting mechanisms. Both are very accurate. The C-gears provide a disc for readout, so this can be easily geared up or down to increase accuracy in the dial itself, at the possible expense of having any clue what that readout means (i.e. Is this 5 representing 5, 50, 500, or 5,000 meters?).
The gears can, however, be knocked out of phase, meaning that you get nonsensical distance readings, or perhaps direction as well.

The pistons, however, cannot be knocked out of phase like this very easily. However, the mechanism can lock up and give you no clue of distance or direction if the target passes too close. It will right itself when the ball passes in front of the wandering arrow at a greater distance, so it resumes function. This could be prevented if there were more pistons in the mechanism, meaning the only way to break it would be to badly stretch the hinges and pull a piston either through the piston wall or out the end of a piston.

So, all in all, the mechanism on the right is more precise, but easier to break.
Both, however, are well-deserving of the title "Good job."