The Schubert Model DRV is a pin-wheel calculator. It take its name from the fact that it has a circular disc or wheel which has nine retractable pins extending radially around part of its circumference. The pins can be extended or retracted by a setting mechanism, which is generally operated by rotary levers. The pin-wheels and setting rings are assembled into a "rotor" or cylinder, which rotates forward or backward as the handle is turned. The extended pins act as gear teeth to advance a register by the corresponding number of places. The wheel in the illustration shows five pins extended on the left-hand side. (The two pins on the right are part of the tens-carry mechanism). It was marketed as a ADM Teacher for the UK market.

Emil Schubert (1883-1952) built the Thales pinwheel calculator (above) at Rastatt in Germany from 1911, and the Tasma add-list machine from 1924. Schubert lost control of the company in the early 1930s, but re-established a new business under his own name in 1938. Production of Schubert calculators resumed after the war, and continued until the late 1960s.

The Schubert Model DRV was first introduced in 1953. This colourful version in metallic green hammertone is from the 1960s. The machine was designed to facilitate one-handed operation, with all of the controls located (or duplicated) on the right-hand side.

The rotor has ten setting rings on 7mm centres, with a check dial above and a quick-clearing lever to the right.

The carriage has separate clearing levers for each register. The right-hand lever normally clears both, but the coupling can be disconnected by pressing the small tab between the registers. The carriage shift levers at the front are replicated in the double-sided lever below the winding handle.

The counter register has full tens transfer, with automatic reversing and manual override. The carry mechanism is unusual, in that it uses a simple odometer-style register with a powered "helper" mechanism to assist each dial over its detent.

The machine has a back-transfer mechanism operated by the handle at the right-hand rear. The rotor clearing lever is pushed rearwards and held, then back-transfer lever is pulled forward and latches. The result is transferred as the accumulator is cleared.

Manufacturer: Schubert
Date: 1953

This exhibit has a reference ID of CH6057. Please quote this reference ID in any communication with the Centre for Computing History.

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