Accounting machines, the IBM 1403, and why printers standardized on 132 columns

Re:Accounting machines, the IBM 1403, and why printers stand... by chiph on Tuesday January 22, 2019 @09:15PM (#18975073)

How did the 1403 start & stop the paper advance? Once the paper gets moving, there's a lot of inertia there. Was there an air bladder in the hydraulic line to absorb fluid-hammer from the rapid pressure changes?

One of the printers I worked on in the USAF had electromagnetic clutches - one would engage to hold the paper in place while the other would open to disengage the drive belt. To move the paper, the "hold" clutch would disengage and the "drive" clutch would engage for just long enough to move it the required distance. And then the clutch action would reverse (hold clutch engage, drive clutch release) to stop the paper's motion.

After a while, the clutch material would wear out and you would get the infinite form-feed.

Edit: For the curious, this was taken at the school at Sheppard AFB in 1983: https://imgur.com/a/J74K6wM

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Re:Accounting machines, the IBM 1403, and why printers stand... by kens on Tuesday January 22, 2019 @10:24PM (#18975388)

The 1403 has electrically-controlled valves to send fluid from the constantly-running pumps to the hydraulic motor to do a space (line feed) or skip (form feed). There's a back pressure bypass valve that relieves the pressure when the printer advance stops.

The 1403 Field Engineering manual goes into great detail on the hydraulic system, starting at page 56. The momentum when stopping is described on page 62. Link: http://ibm-1401.info/0KenShirriff/IBM_Field_Engineering_Manu...

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