Uploaded March 2020 | Updated September 2026, 2 hours ago

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The Add-em toy adding machine has an unusual and ingenious mechanism. It does not have a normal carry mechanism where one number wheel causes the next wheel to be incremented. Instead, the buttons directly drive all the wheels that need to turn.

Here is the main video where I demonstrate the Add-em:
youtube.com/watch?v=lIvyMR1tCSk

For more information on this and other calculators in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:44 Mechanism overview
1:20 Button latch
2:48 Carry from 10s to 100s
3:59 Carry from 1s to 10s/100s
6:04 Outro