Printed Brain - Slide calculator

Before digital electronic calculator there was many genius mechanical calculators, one of the simpler is the sliding calculator, also known as Addiator (specific brand) and Magic Brain.

I recommend getting some countersunk 5mm M3 screws so put this together, but if you don't want, glue or tape should work as well.

Customize it on Onshape: https://cad.onshape.com/documents/2c1e1e41af824f44070417e2/w/825cc559e6e41afb90ddb9fd/e/7e3f1d24644b28f1d5aff32d

Printing

Designed to work with 0.2mm layer height, but the ones i printed the pats at 0.1mm seems to work a little bit smoother, could be other factors as well. Change filament colors to make text easy to read. Use the color change at leyer function in the slicer and change filament manually or use MMU.

Fronts

Print both fronts with the front side down, do color change after 0.2 mm to make text easy to read.

Slider

Print 9 of these. You can do color changes in a bit different ways to get the look you want. I tried doing dual color with black - red - white - black. That way one side of the sliders have white, and the other red numbers. The contrast between red and black is a bit harder to read but you can do interesting things like  grouping numbers with different colors.

Assembly

Bend the sliders a little bit, that way they won't slide around freely in their tracks, making it less likely you loose your calculation from just a little bump.

Put the sliders in the track of one of the fronts.

Put the other front on top.

Screw (countersunk M3 5 mm) or glue the fronts together, make sure no glue gets the sliders stuck in their tracks.

Usage

You can use a ball point pen, or a pointy tool as a stylus.

The round holes will show the current value.

Clear the calculator by pulling each digit from the bottom until the round windows shows 0.

Addition

1. Flip the calculator to the + side.
2. Stick the stylus in the hole in the slider teeth right next to the number you want to add.
3. Try to pull downward, if you can get all the way to the bottom you have added your number.
4. If you get stuck on the way down (and the digit in the round hole is 9) you need to pull upp and move your stylus over and down the hook.
5. If you can't pull down the hook, you need to move to the main track for that digit and pull from 1 and go over it's hook.

Subtraction

The calculator can only do subtraction on positive numbers.

1. Flip the calculator to the - side.
2. Enter your initial value you want to subtract from, there is no simple way, just pull them down until you have the numbers you want in the round holes.
3. Try to slide the picked number up.
4. If you get stuck, go down and under the hook.
5. If the hook is stuck, go to the main track for the hook and go from 1 down under the hook.

Multiplication

You may want pen and paper for this. Lets do 123 x 456.

We will do this as 3 x 456 + 20 x 456 + 100 x 456.

Lets start from the right digit and add numbers 6, 5, 4; 3 times each. Essentially you do each step as single digit multiplications.

You just shift left as there is 0's in your numbers. 3x6 = 0 steps, 3x50 = 1 step, 20x6 = 1 step, 100x400 = 4 steps.

If you need to do something like 7x1, instead of pulling 1 7 times you can do 1x7 and pull 7 once. You can also do head multiplication on small numbers like 3x3 = 1x9 as long as the result is 9 or less.

Division

Sorry, haven't gotten in to that so i can't help you (yet). I'm sure you can find it on other places on the internet.