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Odhner 139 Mechanical Calculator

It all started at the flea market at Quinquonces in Bordeaux, France.

On April 20, 1998, I saw this cool old calculator for 100€

Original condition.JPG

It was rusty, dusty, and stuck.

An Original Odhner Model 139 serial number 139-751016.

I brought it home and didn't get around to working on it until May 2019.

First, I did some digging on the web.

These sites recommended using solvents and lots of 'elbow grease' to clean the gummy old oil on the parts. I was afraid of losing them (not to mention the smell and I'm a little lazy) so I decided to use an ultrasonic cleaner (an H&B Industries Industrial Grade 160 Watts 2.5 Liters Digital Heated Ultrasonic Cleaner). The cleaning ritual would be:

  1. Disassemble while take tons of pictures and putting parts in labeled plastic bags

  2. 12-18 minutes in the ultrasonic cleaner with heat in a 50/50 mix of water and Simple Green cleaner

  3. dip in water to remove detergent

  4. dip in methanol to remove water

  5. let air dry

  6. lubricate with Nyoil or Hoppe's Number 9 oil

  7. reassemble.

Here are some pictures of what it looked like before cleaning. There's tons of gunk in there - no wonder it was stuck!

rotor original.jpg
left side original.jpg
carriage original.jpg

It wasn't easy. There are a zillion little and non-replaceable parts in the calculator. I managed to get it back together while only losing one tiny little spring. I managed to get a replacement from Tom Goodkind in the UMB Machine shop who also provided excellent advice along the way.

Once cleaned, it wasn't in original condition, but it was a lot better:

cleaned inside.jpg

But it didn't work! It was still jammed! Step by step, with lots of patient help from John Wolff, I was able to debug the mechanics of the thing. It was very interesting to see logic implemented in metal rather than silicon. It took a bit to get my brain into that mode but it was very satisfying when it finally worked!

final outside.jpg

July 14, 2019 - it is finally fully working! It adds, subtracts, multiplies, and divides with a very satisfying mechanical feel. Theoretically, it can take square roots, but I need to figure out the instructions....

Here are some videos:

      123 x 456 = 56088                                                      1/7 = 0.1428571

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