My collection of old adding machines

I have a collection of mechanical calculators that I have rescued and returned them all to full working order. My interest in these machines began when I happened to see a YouTube video featuring a Friden machine. After telling someone about my newfound interest I was later gifted an adding machine for my birthday, later someone else gifted me a couple more and next thing I knew I was acquiring more and more of them until I now have over 40 of the things, and counting...

These machines seem to attract little interest or value (apart from really early ones or 'THE CURTA!'), most of them have been given to me or I have bought for under £10 plus postage, I like to think I am rescuing them from being lost forever and some day interest in these machines may increase. I will probably donate them to a museum one day?

See the Schickard Calculator I made
A collection of old film clips of adding machines

A comptometer emulator
Computing/calculating time line
Videos: My Diehl model E15 in action,   My Burroughs Class P in action

You can see more about these machines here: Jaapsch or JohnWolff or Vintage-Calculators or Prof. Christian-M. Hamann or Wim Hasselo or Crisvandevel
Others: Slide adders, Slide rules, Lalannes Abaque

YouTube links: GrumpyTim or ChrisStaecker.
Curious Mark's video about his Friden
Comparing speeds of some electromechanical calculators
My Marchant filmed in slow motion
How a 10 key adding machine works (Remmington Rand)

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Click on a device in the image for more info.

The collection includes: Brunsviga, Citizen, Olivetti, Diehl, Precisa, lagomarsino numeria, Multo Addo, Facit, Bell Punch / Sumlock, Burroughs, National / NCR, Monroe, Muldivo Mentor, Contex, Felt & Tarrant Comptometer, Remington Rand, Bowler, Schickard Calculator and Napiers Bones.

Some handy tips I have learned whilst restoring these machines

> Most problems you will encounter is the old oil has turned to a stiff, sticky mess and glued moving parts together. A electronics heat controlled hot air gun is very good for softening it up so you can get it moving enough to work some new oil in to it. In extreme cases I have found heating it by resting a soldering iron on to it has worked mirracles.

> Solder is very handy for repairing broken parts (I find an electronics soldering iron and solder works fine), with small parts you can actually form the molten solder in to shapes and it is a very handy way to build up worn surfaces. I have even in one case managed to replace a broken gear wheel tooth in this way which worked surprisingly well. It will of course not be as strong as the original metal but it works and also is very easy to remove at a later date if required so doesn't cause any permanent damage to the machine.

> Water slide decal printer paper is very handy for replacing missing text/labeling etc. and also very handy for putting the text on replacement key caps. You simply print your required text/image (if printed on an inkjet you need to then seal it with a spray laquer), cut it out, put in some water to soften the glue and slide it in to place. This is very good for putting the text on replacement key tops.

> Patents are a good place to find information on how the calculators work etc, you can search them at espacenet (thanks Martin Cummins for suggesting this site).

> With the add-lister type machines such as the Olivetti and Citizen there is a bar which a carriage slides along as the numeric keys are pressed, I have found oiling this a very important first step as this sticking can be the cause of a lot of issues.

> With cracked/broken plastic cases I find sinking some fine wire stainless steel mesh in to the plastic across the break with a soldering iron makes a good/strong repair. Fine adjustment can be made by heating the area with a hot air gun.
To replace missing plastic putting some baking powder on it, dripping superglue on to this then building up more layers works well

> If you need to replace a drive belt search eBay for 'Round Polyurethane Conveyor Drive Belt PU Green Rough Surface Transmission Belts'.

> I have a few items I created for 3D printing which may be of use/interest: Thingiverse