John Wolff's Web Museum

The Marchant Calculating Machine Company


 

Contents

Marchant Silent Speed 10-ACT
Marchant "Silent Speed", 1930s

Overview

Monroe Nameplate c. 1925 (4kb)

In 1911 Rodney H Marchant obtained a US Patent (No. 994414) for improvements to the carriage shift and winding mechanisms of the Odhner-style pin-wheel calculators. Machines incorporating these improvements were built by the Marchant Calculating Machine Company in Oakland, California, and proved very popular.

It appears that Rodney Marchant may have neglected to licence the pin-wheel mechanism to which his improvements were applied, which led to trouble over patent infringements in 1918. The situation was saved by a young Swedish engineer named Carl Friden, who sold Marchant an original design for a modified pin-wheel mechanism. Instead of individual pins on the rotor, Friden's design uses a sliding gear segment which extends and retracts at the appropriate times to advance the register by the required number of positions. Friden had only recently arrived in America, and is said to have developed some of his designs while stranded in Sydney, Australia during the 1914-18 war.

Friden continued to develop the modified-pinwheel machines at Marchant during the 1920s. By the end of the decade the product range included manual machines with lever or full-keyboard setting mechanisms, motor-driven machines, and machines with semi-automatic multiplication and division.

Carl Friden left Marchant in the early 1930s to establish his own calculator company. Harold T Avery became Chief Engineer around 1931, and led the development of the remarkable "Silent Speed" mechanism that first appeared in 1932. The Silent Speed was based on a continuous-drive mechanism using proportional and differential gears, and was the fastest and quietest machine of its time. The machine formed the basis of Marchant production for the next 30 years. Harold Avery held more than 60 patents for the Silent Speed mechanism, and was still actively involved with its development in the mid-1950s.

In 1958 Marchant merged with the Smith-Corona typewriter company to form Smith-Corona Marchant, which later became the SCM Corporation. SCM expanded the calculator product range by reselling imported machines, including the German Diehl ten-key printing calculators and the Hamann TenKeyMaster. From around 1970 SCM re-sold a variety of mechanical and electronic calculators under the Marchant name, including the Clary Addmaster and the Compucorp range. The calculator business finally closed in 1973.



Modified pin-wheel machines

Marchant DRB8 (8kb) Marchant Model DRB8, S/N 1320.
Technology: Modified pinwheel, manual
Digits: 9 keyboard, 9 counter, 18 accumulator
Dimensions: 10-1/2"W x 12-1/2"D x 7-1/2"H, extended width 15"
Weight: 28 pounds (12.9kg)
Manufactured: Oakland, California, 1920s-30s.

This Marchant Model DRB8 is a full-keyboard rotary calculator from the late 1920s. The machine uses the Friden "modified pinwheel" mechanism, with the pinwheels located at the upper left of the machine and the accumulator register directly below in the small sliding carriage. The carriage can be moved continuously by releasing the latch at its left-hand end, or one step at a time by rocking the lever at the front of the machine.

The counter register is fixed in position at the upper right. The single clearing handle is rotated clockwise to clear the counter, and anti-clockwise for the accumulator. The machine has full tens-carry in the counter register, and to 13 places in the accumulator. The casing is painted in a dark green wrinkle finish, with a large cast-aluminium base and three brass nameplates. The baseplate carries an extensive patent label, with the last issue date in 1928.

Operation of the machine is initially confusing because the keyboard columns are spaced wider than the pinwheel discs and do not align with the registers. The accumulator must be positioned relative to the setting register above, rather than to the keyboard columns. A moving indicator is provided adjacent to the counter register to show the active position.

The strange alignment is due to the calculator's origins as a lever-set pinwheel machine, without the keyboard. The setting levers were mounted between the pinwheels at the upper left in the normal fashion, where they aligned directly with the accumulator below. The keyboard setting mechanism was added later as a convenience.

Keyboard-less Marchant Model XL (illustration ex Martin) (28kb)
 

Marchant DRB10 (8kb) Marchant Model DRB10, S/N 1152-6
Technology: Modified pinwheel, electric
Digits: 10 keyboard, 9 counter, 20 + 16 accumulator
Dimensions: Body 10"W x 16"D x 8"H, overall 16-1/2"W x 18"D
Weight: 50 pounds (22.6 kg)
Manufactured: Oakland, California, 1920s-30s.

Model DRB10 is similar to the DRB8 above, but adds two new features - a second "grand total" register in the carriage, and an electric motor drive.

The grand total register is mounted directly above the main accumulator, and can be engaged and cleared separately. It covers only the leftmost 16 digits, with a round-off mechanism to eliminate the fractional cents accumulated in the first four places. The mechanism is described in Friden's US Patent 1928125, filed in 1929 and issued in September 1933.

The electric motor and the main gearbox are mounted externally on an extended baseplate at the rear of the machine. The Westinghouse 220V DC motor has an open-frame construction with the commutator and connections fully exposed. (DC distribution was used in many parts of Australia during the 1920s, before the establishment of a wider AC grid. DC supplies for specific machinery (such as lift motors or theatre arc lamps) were still available in central Sydney into the 1970s). The motor drive is engaged by the Add and Subtract bars on the keyboard, and by the powered clearing controls for the three registers in the extended section at the right-hand rear. Carriage positioning is still done by hand.

The complete key-set calculator and its motor drive mechanism are described in Friden's US Patent 1643710, filed in February 1924. The patent also describes an additional row of keys (not present on this DRB10) which will repeat an add or subtract operation for a set number of times, for use in multiplication and division. This mechanism formed the basis of the fully-automatic "on-the-fly" multiplier of the "Silent Speed" range.

The underside of this DRB10 has the same patent label as the DRB8, with three more numbers added on a separate sticker. The last is 1866023, issued in July 1932. However the 1933 patent for the grand total register is not listed, suggesting that this machine was built between these two dates.

Marchant DRB10 rear view (30kb)
 

Marchant H9 (8kb) Marchant Model H9, S/N 11900.
Technology: Modified pinwheel, manual
Digits: 9 keyboard, 9 counter, 18 accumulator
Dimensions: 10-1/2"W x 12-1/2"D x 7-1/2"H, extended width 15"
Weight: 28 pounds (12.8kg)
Manufactured: Oakland, California, 1930s.

The Marchant Model H9 is essentially the same as the DRB8 above, but with a simplified baseplate, plain black colour scheme, and no decoration.



Proportional-gear machines

Marchant Silent Speed logo (5kb) The Marchant "Silent Speed" and its descendants use a complex and unusual continuous-drive mechanism based on proportional and differential gearing. Every column of the machine incorporates a ten-speed gearbox with three drive shafts and five selectors. The accumulator tens-carry mechanism is contained entirely within the carriage, using an additive (ie, differential) gearing mechanism with two planetary gearsets per digit. The high-speed division algorithm does not wait for underflow, but uses a predictive trip mechanism based on a two-decade analog magnitude comparator. The machine contains well over four thousand parts, with over one thousand parts in the main register alone. In spite of the complexity, the machines were unsurpassed for speed and reliability.

The Marchant proportional-gear machines were continuously refined and developed over a period of more than thirty years, and were generally regarded as the pinnacle of rotary calculator technology. A detailed description of the mechanism is provided in the Technical Section of this site.



Marchant Silent Speed 10-D (8kb) Marchant Silent Speed Model 10D, S/N 157664
Technology: Proportional gears.
Digits: 10 keyboard, 10 counter, 20 accumulator
Dimensions: 11-1/2"W x 14-1/2"D x 9"H, carriage width 15"
Weight: 36 pounds (16.2 kg)
Manufactured: Oakland, California, 1932-

Model 10 D is one of the first "Silent Speed" machines, introduced in 1932. The machine has an internal motor drive, with powered clearing and carriage shift controls. Separate Add and Multiply keys are provided for single or multiple cycles. Division is set up manually, and then proceeds automatically to completion.


Marchant Silent Speed 10-ACT (8kb) Marchant Silent Speed Model 10ACT, S/N 253767
Technology: Proportional gears, fully automatic.
Digits: 10 keyboard, 10 counter, 20 accumulator
Dimensions: 11-1/2"W x 14-1/2"D x 9"H, carriage width 15"
Weight: 37 pounds (16.9 kg)
Manufactured: Oakland, California, 1930s-40s

Model 10ACT includes an automatic "on-the-fly" multiplier based on Friden's cycle-counting mechanism from 1924. The multiplier keyboard is a single vertical column of keys on the far right of the machine. When a multiplier key is pressed the machine will automatically perform the required number of additions and move the carriage into the next place. The next digit can be entered while the machine is still running, giving a very fast and smooth operation.


Marchant 10DRX (8kb) Marchant Figurematic Model 10DRX, S/N 412562
Technology: Proportional gears, fully automatic.
Digits: 10 keyboard, 10 counter, 20 accumulator
Dimensions: 12"W x 16"D x 9"H, carriage width 16"
Weight: 39 pounds (17.7 kg)
Manufactured: Oakland, California, 1950s

In the late 1940s Marchant engaged the noted industrial designer (and expatriate New Zealander) Joseph Sinel to produce a new external casing for the Silent Speed machines. Sinel transformed the rather "busy" appearance of the original machines into a very clean, simple, and elegant design. The new machines had smooth cast-aluminium sides, with sheet-metal front, rear, and bottom covers. The panels are held together by an ingenious system of interlocking flanges, with no screws or fasteners visible anywhere on the external surfaces.

The new models were known as the "Figuremaster" and "Figurematic", but the mechanisms were essentially the same as the "Silent Speed" above.


Marchant10ADX.jpg (8kb) Marchant Figurematic Model 10ADX, S/N 569259
Technology: Proportional gears, fully automatic.
Digits: 10 keyboard, 10 counter, 20 accumulator
Dimensions: 12"W x 16"D x 9"H, carriage width 16"
Weight: 39 pounds (17.7 kg)
Manufactured: Oakland, California, 1953-

The "Figurematic" Model 10ADX is essentially the same as the 10DRX (above), but with the addition of a push-button carriage tabulator and an automatic division setup key.


Marchant TR10FA (8kb) Marchant TransFlo Model TR10FA, S/N 638399
Technology: Proportional gears, fully automatic.
Digits: 10 keyboard, 10 counter, 20 accumulator
Dimensions: 12"W x 16"D x 9"H, carriage width 16"
Weight: 41 pounds (18.6 kg)
Manufactured: Oakland, California, 1955-

The "TransFlo" Model TR10FA is essentially the same as the 10DRX (above), but with the addition of a back-transfer mechanism between the accumulator and the setting register. The covers changed from green to blue in the mid-1950s.


Marchant SKA (8kb) Marchant Deci-Magic Model SKA, S/N 598831
Technology: Proportional gears, fully automatic.
Digits: 10 keyboard, 11 counter, 20 accumulator
Dimensions: 12"W x 16"D x 9"H, carriage width 16"
Weight: 44 pounds (19.8 kg)
Manufactured: Oakland, California, 1958-

The Model SKA (Single Keyboard Automatic) or "Deci-Magic" from 1958 is the most complex and highly developed of the Marchant range. The "on-the-fly" multiplier has been replaced with a new mechanism having internal storage for a full ten-digit value, which is displayed in a separate register at the front of the machine. The storage mechanism is used in multiplication, and also to provide temporary storage for keyboard or back-transferred values. The new mechanism includes automatic division setup, automatic decimal alignment, and a one-touch "Square X" function.

The Deci-Magic mechanism is described in US Patent 3019971, filed in 1956 and issued in 1962. The patent lists five inventors, including Eugene Reynolds and Harold Avery.


SCM Marchant TR (8kb) SCM Marchant Transflo Model TR, S/N 721280
Technology: Proportional gears, fully automatic, back transfer.
Digits: 10 keyboard, 11 counter, 20 accumulator
Dimensions: 13-1/2"W x 16"D x 9"H, carriage width 16-1/2"
Weight: 44 pounds (19.9 kg)
Manufactured: Orangeburg, South Carolina, after 1962

In 1962 SCM moved the production of the Marchant calculators from Oakland to a plant in Orangeburg, South Carolina. The new models had a wider and more angular casing, with cast alloy panels held together by a system of concealed toggle clamps.

While the new styling lost something of the simplicity and elegance of the 1950s models, the internal mechanism was largely unchanged. This Model TR is generally similar to the TR10FA (above), with a back-transfer mechanism and on-the-fly multiplier.



Resources for further information

 


Original text and images Copyright © John Wolff 2002-11.
Last Updated: 19 April 2011


Back to:    Home    Calculating Machines    Full-keyboard rotary calculators