Typewriter Talk / How do electric typewriters work?

**Posted by jeffbiss** 27-2-2025 17:54:25

Hello all,

I have an Ollivetti 36 that's fan runs when power is turned on, but it doesn't type. I see that it is missing a belt, I removed it from its case, but don't see any wires running anywhere but from the On/Off switch to the fan motor. I don't know how electric typewriters work, so to start me on the road to fix this electric typewriter can someone point me to good information that explains how electric typewriters work?

I've searched the internet, but get useless high level descriptions when I need lower level information to help me determine where to start removing parts first. I am reticent to start that process because I'm not sure how to safely remove the plastic keys in order to remove a cover plate.

Thanks, Jeff

**Posted by Eagle** 28-2-2025 06:48:14

Hello Jeff,

first I have to say that I'm not an expert on the Olivetti 36 or any other Olivetti.

What I found on the internet is that the wiring from the On/Off switch goes underneath the machine to the motor as one can see at the end of this video:
Olivetti Lettera 36 Features Review

The wiring is also visible on one of the photos here:
Typewriter Database - 1972 Olivetti Lettera 36 #594248

Electric typewriters are using a rotating drive shaft (power roll) which is driven by the electric motor via a belt. The details could be different for other manufacturers and typewriter models. The rotating drive shaft could either have teeth on it or the surface is coated with rubber like the machine's platen. In the case of the Olivetti 36 it could be a drive shaft with teeth I would assume.
A technical drawing of the Olivetti Praxis 48 that shows that principle:

The toothed drive shaft (1) rotates in direction of the arrow. When the key lever (9) is triggered by the operator the ratchet (2) is tipping over into the teeth of the drive shaft. Over a system of levers the typebar (8) get the necessary momentum to strike the platen.
That's a very short explanation of the mechanics behind a electric typewriter.

Here a Phoenix Typewriter video of a Olympia SGE 35 typewriter with a toothed power roll:
https://www.youtube.com/watch?v=XfJ6nBux8f8

And as an example of a rubber coated power roll here a video that shows it's removal as part of a repair of an IBM Model C typewriter.
https://www.youtube.com/watch?v=Kl-o9bIjw10

This video shows a repair adjustment of individual sticky keys of an IBM Model D. A video that shows also the working of the power roll.
Often a lot of experience and some special tools are needed for servicing a typewriter.
https://www.youtube.com/watch?v=MBK25GOEyck

Have fun exploring and repairing your Olivetti typewriter!
-Rainer

And be careful with electricity - it can bite.

**Posted by Eagle** 28-2-2025 06:55:06

Eagle wrote:
A technical drawing of the Olivetti Praxis 48 that shows that principle:

And I have to correct an error that I've made.
The technical drawing shows a Olympia SGE 50.

**Posted by Pete E.** 28-2-2025 11:10:28

My Olivetti Lettera 36 required toothed belts. But some of these machines, use smooth belts. The type of pulleys on your machine will determine what style you need.

For my machine...I got 2 sets of toothed v-belts from this on-line outfit : https://vbeltoutlet.com/ The motor side belt was : 145 teeth long, 5 mm wide, and a 2.0 mm tooth pitch. The power-roller side belt was : 153 teeth long, 5 mm wide, and a 2.0 mm tooth pitch. p { line-height: 120%; margin-bottom: 0.1in; background: transparent }a:link { color: #000080; so-language: zxx; text-decoration: underline }

**Posted by jeffbiss** 28-2-2025 18:42:59

Eagle and Pete E.,

Thank you very much for that information. I'm surprised that there is a book about typewriters that explains it all as there are with other technologies. I started with this question simply because I thought having a "how it works" post would be a good thing. I didn't think of going to patents for that information, but it makes sense. I was hoping that Trusty Old School would have more detail as to what's under those covers, I took only the exterior and first inner covers off, so I could see what I would get into when I take that lower inner cover off to deal with the sticking type arms. Oh well, I will try to document that for an Olivettii Lettera 36 post

And Pete E. that link to belts and what you found was needed is a great help, I will be able to order a few, but am missing the one from the motor to the big black pulley, I don't know what to call either, but you do.

**Posted by Pete E.** 01-3-2025 08:17:50

Jeff,

The big black pulley, as you say, is the power roller pulley. Without a belt, there, your type-slugs will not activate to strike ribbon & paper.

Below is a photo off the Internet showing a machine with flat-belts (and not toothed belts). This machine in the photo is a later production of the Lettera 36 with its squarish-shaped key-tops, etc.

My machine is an earlier one when the key-tops were round-shaped. See 2nd. photo, below.
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**Posted by Pete E.** 01-3-2025 08:28:12

Jeff,

Hope you do not mind a bit of un-solicited advice.

I have 75 typewriters in my collection which I cleaned, serviced, and repaired all of them but one which needed repairs above my pay-grade. And 12-13 of them are electrics.

I added an Olivetti Lettera 36 and a Praxis 48 as the last couple of electrics in my collection. I found they are very complex mechanisms crammed in very small and tight spaces.

I gained experience working on more simple and easier to work on electrics like the Smith-Corona 5TE and Electra 110, 120, 210, models

Some of the Electras can be had for cheap on Shop Goodwill and they might help you to gain experience before you tackle the Lettera 36. I would suggest putting the Lettera 36 on the shelf for a while and build your skills on one of the Smith Corona Electra machines, first.
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**Posted by jeffbiss** 01-3-2025 09:50:06

Pete E,,

Advice is welcome. I fully understand what you're saying and will look into getting more experience. But I had no idea as to how these things work and am amazed at how simple the concept is. I was expecting a more complicated system that actuated the type bar, not just a continually spinning roller that would propell it.

However, I will be ordering belts so I will have them. That site is a bit difficult to use as it should provide a better search feature, such as entering the details that you provided above. I have to look through their offerings again to find those that you list. I haven't found any 5mm width belts, just 6mm, so I may have to slit them down to 5mm.

**Posted by Pete E.** 01-3-2025 13:21:16

Jeff, you are right about the web site.

It was much user-friendly 1-1.5 years ago when I was working on my "36" and needed belts.

Funny how often web site get changed...usually not for the better.
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**Posted by Pete E.** 01-3-2025 18:16:31

Jeff,

Another vendor here in the States to try is McMaster-Carr Co.

On this web page along the left side, they even have a sizing & measuring guide to help you possibly find belts that will work.
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https://www.mcmaster.com/products/drive-belts/
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