Adjustable Mirrors for Spy Game

This Instructable shows how to make small and tiny adjustable mirrors for a spy laser game.

In the first picture you can see an example setup on a table. The second picture shows you how the setup looks in light.

For the first picture I waited for a foggy night outside. The green laserpointer is in fact a 1mW version, and I obviously didn't clean the mirrors, that's why there are a lot of scattering.

You need:

• wooden half balls (Ø 15-25mm)
• small mirrors (Ø 20-30mm)
• supermagnets ( 6x1mm round)
• glue
• and a drill at the size of the magnets.

I started out with mosaik mirror tiles, but they are quite thick and the reflecting side is below the glass which is not ideal.

Then I found out that the mirrors the dentist uses are not as expensive. They cost 2.-€ per part and if you by 10 of them the price goes down to 1.50€ pp. The reflecting side is still under the surface, but it seems that the glass is coated, because there is nearly no secondary reflection from the glass.

The next important parts are the magnets. They must be really strong to be able to hold the two balls together and to carry the mirror. And they have to fit into the balls. The bigger is not always better. I found that 15mm for the balls and 20-30mm for the mirror is ideal, although the handling is quite fuzzy.

With bigger balls you'll need bigger magnets and bigger mirrors. It is best if the mirror outsizes the ball by a factor of 2. Because if you turn the upper half, the optical axis still hits the mirror. If it is to small you have to move the whole thing.

Take a drill for wood at the diameter of the magnets.

Now drill two flat holes into the balls: One in the middle of the flat side and one on the outer side in a 45° angle to the flat side.

It takes some practise to do this right, but it is not important to be very precise.

Now fill a bit of glue into the holes, let it dry a bit and then press in a magnet.

Make sure the magnets on the flat sides attract each other.
After inserting the magnets, I let the glue dry with the two halfs connected to each other.

I used a sheet of while paper between the two half balls to keep them from glueing together.

Then add one magnet to the hole on the outside of one of the two balls.

The video shows a high speed recording of the ball attracted to the base. It was done with the high speed mode of my Samsung WB750 which makes 480fps at reduced resolution. You see the magnets are really strong! ;-)

Now use the last hole on the other half ball to fix the mirror on the ball.

If the mirror is bigger than the ball glue it to the edge of the mirror. Otherwise you will get problems turning the upper half.

This is now the easiest step. If you have metal door frames you are well off. If not, glue some flat iron sheets on the doorframe or built special stands for the mirrors.

Adjust the mirror by turning the two half balls. Turn the lower ball to move the mirror around the vertical axis, and turn the upper ball to change the slope of the mirror.

The magnets should be strong enough to keep the mirror where it is, once you move it there.

Now go and play the Laser Spy Game!