Uploaded December 2020 | Updated September 2026, 2 hours ago
The Addac was invented in 1925 or 1926 by Andrew Ekman in Grand Rapids, Michigan. It is a simple adding machine with 8 co-axial wheels, and a clearing lever. The carry mechanism works in both directions, so subtraction is done by moving the wheels in the opposite direction to addition.
For more information on this and other calculators in my collection, please visit my website:
jaapsch.net/mechcalc
0:00 Introduction
0:16 Addition
0:58 Subtraction
1:45 Clearing
1:55 Columns
2:22 Serial number, patent
2:40 Legs
3:10 History
4:13 Outro
The Addac was invented in 1925 or 1926 by Andrew Ekman in Grand Rapids, Michigan. It is a simple adding machine with 8 co-axial wheels, and a clearing lever. The carry mechanism works in both directions, so subtraction is done by moving the wheels in the opposite direction to addition.
For more information on this and other calculators in my collection, please visit my website:
jaapsch.net/mechcalc
0:00 Introduction
0:16 Addition
0:58 Subtraction
1:45 Clearing
1:55 Columns
2:22 Serial number, patent
2:40 Legs
3:10 History
4:13 Outro
