The carriage shifting mechanism of the early Marchant calculators is very recognisable, it gives these machines a distinct profile. This mechanism is subject of a 1916 Marchant patent and is quite exposed on the front of the machine - putting it at increased risk of damage.
One of the levers was indeed broken on the target machine, the broken-off piece fortunately still held inside the mechanism.
To try fixing this, the lever was taken out. Fortunately the rod that holds it all in place was freely movable, so slid over to the left and the parts taken out (hold the spring as you slide the rod, to prevent it shooting off into the distance).
The right shifting lever was indeed broken, and actually had an old repair that had failed!
The original steel lever arm (rocker arm) had originally broken where it's weakened by the hole for the connecting rod.
To repair it, some time long ago a brass plate had been soldered to the side and two drilled/pins were added. The solder connection of the brass to the rocker arm had however failed and the part again broke.
After very thorough cleaning of the part, the old repair was re-soldered. The pins could now also be embedded in solder and extra care was taken (flux, much flux) that the solder reached the entire contacting surface of the brass plate with the lever. Hopefully the solder will hold, to be able to keep the original levers on this machine; they are stamped with the last digits of the serial number - parts of machine 70049.
The whole carriage shifter design seems a bit 'out of character' with the rest of the calculator. Even though it works well and is easy to use, it looks (overly?) complicated in its parts design. Even the lever is assembled from three separate parts; three stampings (needing multiple tools!) and a turned rod. Below shown as loose parts; the two different (!) rocker arms and the keypad - these need assembling and 'riveting' together.
That's not even mentioning the complex locking-pin, the swaying gear assembly and complicated casting details of the base. Quite a few parts to be assembled, with a few very tricky springs to insert as well. Here in in the factory; assembly of the full-size Marchant A, not the Pony:
It does however work very well, is surprisingly easy to use and is an (the) original Marchant-specific part of the calculator.
Comparing to the donor-machine, there are again multiple small differences also in this mechanism. These machines are probably very close together in time; the donor machine (shown on right) will date to late 1919 (November?) and the target machine (shown on left) probably is an early 1920 machine.
No comments:
Post a Comment