# Jaap's Mechanical Calculators Page

The curved front of the casing has 7 vertical slots inside of which are a set of co-axial paddlewheels, These wheels are used for entering numbers, and simultaneously act as number wheels of the 7-digit register. To the right of each slot are digit markings 0 to 9, and on the left is an opening through which part of the wheel is visible, displaying a digit of the register. To enter or add a number to the register, simply enter each digit by putting your finger on the associated paddle next to the digit you want to enter, and pull your finger downwards until it hits the ledge at the front of the machine. The register carries automatically using a spring-loaded mechanism.

The digit markings also have the complementary digits in a smaller font, and these allow you to do subtraction. To subtract a number, simply enter it using these complementary digits, including all leading zeroes, and then add an extra 1.

To clear the register, pull forward the crank that is on the left side of the machine as far as it will go, and then let it return to its rest position.

It has serial number 47934, and the first two digits are the year of manufacture, 1947.

## Video

Below is a video I made that demonstrates the Högfors adding machine.

## Instructions

The instructions are on a piece of paper stuck to the bottom of the machine. On mine it is quite damaged, but from online pictures of others I have recovered the full text and I reproduce this below.

### Directions for Use

Before starting check that each window in the horizontal row marked "TOTAL" indicates zero (0). If not, push down the handle to its lowest position. The handle will return automatically to its normal position.

As a general rule, each figure is "set" by putting your finger in the recess between two teeth located opposite to the figure in question on the right side of each toothed wheel. Then pull the finger downwards until it abuts against the forwardly extending portion of the cover, thus causing the wheel to rotate the corresponding distance or angle.

If two or more quantities are to be added, set each figure of the first quantity successively as mentioned above, only using the large figures at the cover, and then proceed in the same manner with the figures on the units wheel, the tens figures on the tens wheel and so forth. When all quantities have been accordingly set one after the other the final result is shown in the windows in the "TOTAL" row.

#### SUBTRACTION

When subtracting first set the larger quantity or subtrahend. Then add the figures of the subtractor, now using the small figures on the cover and finally add 1.

Example 1. Subtract 147 from 793. Set 793 in the usual manner. Then, using the small figures, add 0000147 and 645 will appear in the windows. Add 1 and the correct result will be 646.

Example 2. Subtract 48030 from 74362. First set 74362, using the large figures. Then, using the small figures, add 0048030 and 26331 will apear in the windows. Add 1 and the correct result 26332 is shown.

#### MULTIPLICATION

When multiplying two quantities write them down, one beneath the other. Instead of writing down the partial products those are set with the wheels and are added successively. This is easiest shown by means of an example.

Example 3. 563×234=? Beginning from the right side proceed as follows: 4×8=32 which result is set on the first and second wheel from the right. Then, 4×6=24 which is set on the second and third wheel, and 4×5=20 which is set on the third and fourth wheel (really only the fourth since the zero is not set on the third wheel). Now we take the second component of the multiplier: 3×8=24 which is set on the second and third wheel, then 3×6=18, which is set on the third and fourth wheel, and 3×5=15 which is set on the fourth and fifth wheel. Now proceed in the same way with the third component of the multiplier, 2×8=16 which result is set on the third and fourth wheel, 2×6=12, which is set on the fourth and fifth wheel and finally 2×5=10, which is set on the fifth and sixth wheel. The final result of 132912 is then shown in the windows.

## History

Högfors is a location about 140 km northwest of Stockholm, near Norberg. Högfors means high fall, or waterfall, and the river Norberg drops some distance there which made it the perfect place for a water wheel. In the middle ages there was already ironworking being done there, and it is known that in the 16th century they were using a trip hammer powered by the river.

Högfors Bruk (Högfors Mill) was in continuous use as an ironworks for centuries, at first under co-ownership of the Swedish crown, and eventually in the 19th century as a limited company. At its peak about 250 people worked there.

The last new blast furnaces were built in about 1915, but the whole mill was closed down in 1953. I presume that it was no longer profitable due to its relatively small scale and remote location. The ruins of the ironworks still exist and are open to the public. Many of the buildings were made of wood, and all but a few of those are gone, but the blast furnaces and stone walls of the surrounding building are still standing.