These notes describe the mechanism and operation of all of the user controls and most of the internal links and levers in the Madas 20ATG. The notes are based on my own observations during the re-building and testing of several A- and B-series machines. All Madas automatic models share the same basic mechanism, which evolved only slowly from the Portable of 1931 to the BTZG of the 1960s. (The B-series machines have a power-assisted set-up mechanism to reduce the force required on the multiplication and division keys. After the initial setup cycle, the operation is the same as in the A-series).
The notes following have been cross-referenced to the partial set of 23 technical training drawings that were preserved by the late Mr Ray Mackay of Melbourne. The drawings relate mainly to the basic control mechanisms, the carriage shift and register clearing mechanisms, and the multiplier mechanism. Many of the multiplier controls are also used during division, but there are no drawings specifically for the division programming mechanism. There are no drawings available for the keyboard, and only a general arrangement for the triplex carriage.
Most of the drawings are dated around 1935-37, except for sheet 2869 from 1951 which includes the carriage tabulator mechanism for the AS-series machines. Regardless of the model, the automatic machines all operate on the same principles, and the majority of the parts will be similar or identical to the drawings. Please use the enquiry form for further information about the drawings, and be sure to include the model and serial number of your machine.
A cross-reference to (eg) "division trip lever 1490/2D6" indicates that part number 1490 can be found on sheet 2, column D, row 6. Parts will appear in many places, often in different figures on the same sheet. There are no part names given in either the drawings or the spare parts manual, so "unofficial" names have been made up to suit myself.
The notes following are intended to be read in conjunction with the Madas technical drawings, the descriptions and illustrations on the previous pages, and (preferably) with a machine in front of you.
The Repeat key prevents the automatic clearing of the keyboard, which would otherwise occur at the end of every machine cycle. The key sits at the top of a vertical sliding link (early version 1592/11A6, later version 2904/36B4) on the inside of the left-hand side plate. The Repeat key supports the rearward end of the keyboard clearing link 2040 (not shown), which attaches to arm 1555/28B7 at the front of the keyboard.
If the key is up, the clearing link will engage with a cam on the mainshaft, and will be pushed forward to release the keyboard at 340°. Pressing the Repeat key down lowers the rear end of the link so that it no longer engages with the cam. The key can be locked down by pressing it slightly rearward, so that a projection on the key shaft latches under the keyboard baseplate. The Repeat key can also be raised and lowered by internal mechanisms, as required by the various automatic operations.
An interlock lever 3938 (not shown) on the outside of the brake arm 1820/2C5 prevents depression of the +/- keys while the brake is raised (ie, while other operations are in progress). The brake arm is attached to a cross shaft 1438/2B4 which is located above the cross-bar in the base casting. Shaft 1438 operates the motor switch via a push link 1800/2B4 underneath. The motor runs while ever the brake arm is raised, and stops when the arm falls into the notch in the brake disc 2327/2D5 at 360°.
Ramps on the bottoms of the key shafts 1303/2A5 and 1304/2B5 slide the long horizontal +/- link 1332/2D6 rearward for plus, forward for minus. The keys are held down by notches in their stems engaging with latching levers 1326 and 1327/2D2. The sliding link 1332 operates a lever 2301/2D7 loosely pivoted on the differential slider shaft 1248/2E7 at RHS rear, then via spring-loaded intermediate arms 1245 and 2300 to the operating arm 1240/2E6 on the outside. Shaft 1248 moves the differential gears via two short arms 97/10D1 and a sliding plate 1948/10D1.
There is no "master" positioning control for the differential sliders. At least eight separate mechanisms operate via shaft 1248 to position the gears to plus, minus, or neutral at various stages of the machine's cycles. Once in position, however, the sliders are locked from 40° to 340° by a lever (not shown) from outermost mainshaft cam, which engages with notches at the top of the outer operating arm 1240/2E6 (on later versions).
A flat section on the bottom of plus key stem presses down on a horizontal link 2432/2A1/2A6 at the bottom front RHS. The minus key operates the same link via an intermediate lever 2431/2B1. Link 2432 presses down on pin 6.317/2A6 on a forward horizontal arm on the brake assembly (2A6), raising the brake arm and starting the motor. The mainshaft rotates, adding the keyboard contents to the accumulator register RI and incrementing the counter register RII.
As the cycle completes, a cam on the left-hand end of the mainshaft pushes forward on the horizontal keyboard clearing link, rotating the clearing shaft 1499/28E6 across the front of the keyboard and releasing the digit keys at 320°. On the RHS of the keyboard, an arm attached to clearing shaft 1499 pulls forward on the horizontal link 2432/2A6 at bottom front, disconnecting the plus or minus keystems from the brake arm. The brake arm drops slightly to rest on the disk behind the main drive gear, but not far enough to open the switch. The keystem latches are released by a cam on the mainshaft at 340°. The head of the brake arm falls into the notch at 360°, switching off the motor and bringing the machine to a stop. The rotational energy is absorbed by the brake arm buffer springs.
If the plus or minus key is held down, link 2432/2A6 will still release the brake arm at the end of the first cycle, and the machine will stop. A short vertical arm on the brake assembly presses rearward on a pin on the plus key latch 1326, raising both latches and ensuring that the keys are able to rise when released by the operator.
If the Repeat key is held or latched down, the keyboard will not be cleared at the end of the cycle, the sliding link 2432 will not be released, and the machine will continue to add as long as +/- keys are held down.
The Add +/- lever 2377/2C5 selects normal or complement mode for the counter register (Register II) on add and subtract cycles. Pins on the inside of the + and - keys pass through the holes in the RH side plate and interact with a pair of ramped slots in a sliding gate 2929/2E3 on the inner side.
With the lever in the + position, the Add key moves freely downwards through the wide slot in the gate, and Registers I and II advance normally. Pressing the minus key slides the gate forwards via a ramped slot. A rearward extension on the gate presses down on the RII sliding lever assembly 1809/2C4 via an intermediate arm 2390/2C4.
Lever assembly 1809 has two forward arms which can engage with either the top or bottom of the slotted cam 1805/2C4 on the mainshaft. The lower arm is normally held up and engaged with the cam by the spring 6.945/2C4. Pressing the assembly downwards engages the upper arm, which reverses the phase of the sliding motion and thus reverses the direction of the counter register.
Setting the +/- lever to - changes the home position of the gate and engages a different pair of slots, so that the key interaction is reversed.
The gate is held in position by the pins on the keystems, which do not rise fully clear of the divisions between the slots. In order to move the gate forward or back the ramps must push the keystems slightly upwards, against the large buffer spring 6.888/2B5 on the outer RHS.
If the brake arm is already raised, a link from the brake arm interlock lever (not shown) presses forward on a vertical lever 1907/21E5 (on a separate bracket on the baseplate) so that it stands under square pins on the inside of the two shift key levers (1354 and 1356/21D4) and blocks their movement.
Otherwise, as the keys are pressed, their long rearward extensions rotate a rocking lever 1344/21Fig6 on the end of the shift request shaft 1439/21E3 (see also 9C4) at bottom rear of the RHS. The shaft rotates a small distance clockwise (CW) for left shift, CCW for right. A link 1932/21G3 from the rocking lever trips one or other of the shift clutches 1484'/21E3 and 1484"/21F2, which drive the carriage shifter disc 1174/1B1 on the rear plate. An interlock plate swings between the two key slots in the keyboard baseplate to ensure that only one shift key can be pressed at a time.
The underside of the shift key presses down on two circular pins. The larger pin is attached to a lever (not shown) which raises the front of pinned lever 1466/16E5 at the bottom front of the RHS. Lever 1466 is attached to cross-shaft 1709/11D4 that passes through the multiplier unit (also acting as the pivot for the front all-zero shaft), and pulls the Repeat key down via a horizontal arm 2162/11A7 on the LHS. The Repeat key ensures that the keyboard setting is retained as the machine cycles during the carriage shift. The smaller pin under the shift keys is on a forward extension of brake arm 1335/21D5, and serves to raise the arm and start the motor. The shift keys are held down by a small latching lever 2549/29 near the front, which engages with another set of square pins on the key levers.
At the right-hand rear of the machine, shaft 1248/2E7 which positions the differential gears has a rearward arm 2341/5Fig6 with a pin extending through a hole in the back plate. The pin engages with an open triangular slot near the bottom of vertical lever 2345/5C5 on the back plate, to the right of the carriage shifter disk. A cam 1175/5Fig6 rotates with the shifter disk and pushes lever 2345 to the right, drawing the pin into the centre of the slot and returning the gears to a central or neutral position. An interlock lever 470/21B2, pivoted on the carry camshaft bearing block on the LHS, inhibits the RII rocking lever 1478/21C2 whenever RI is in neutral. With the differentials in neutral and the counter drive disabled, the carriage is free to move without interfering with either register.
As the shifter disc rotates through half a turn, cam 2562/1C1 rotates a full turn, first lowering the locking arm 1324/1C1 and then raising it again after the half-way point. The locking arm is always held just clear of the pins.
Towards the end of the cycle, the shift key latch 2549/29 is released by a clip-on link 2551/29 from a cam on the mainshaft at 305°, dropping the head of the brake arm onto the disk. A pin and lever 2543/32C5 behind the cams on the rear plate push the vertical interlock lever 2345/5C5 leftward from 340°, ensuring a positive release for the differential positioning arm 2341. The shift clutch is reset from a mainshaft cam via lever 2373/21F3 at 350°. The carriage movement is completed when cam 2562/1C1 and locking arm 1324/1C1 push the pins on the shifter disc into their home position (horizontal) as the brake arm drops into the slot at 360°.
The outermost teeth on each end of the carriage shifting rack are spring-loaded, so no damage is done if the shift mechanism is cycled with the carriage at ends of its travel.
The clearing arm 1247/5A6 at the right-hand rear of the machine is driven out and back by the rear camshaft on every machine cycle, but normally does not engage with the clearing racks in the carriage. The clearing keys on the LHS slide the arm fore-and-aft via a long lever system to engage with either or both of the racks.
The brake/switch shaft 1438 has a vertical arm 1552/21B5 on the LHS. A pin on the top of this arm passes through shaped slots in the clearing keys. The pin prevents the keys from moving if the brake arm is raised, otherwise, pressing the key pushes the arm forward and starts the motor.
The L-shaped clearing key levers are pivoted on the Division Setup key shaft near the guide block 1748/21C2 at the top centre of the LHS. The upper horizontal section presses down on a pin on the Repeat key to supress the automatic keyboard clearing. The vertical section presses back and down on a small stepped arm 1644/23C4 pivoted under the base plate, which rotates backwards to a position determined by the height of the step under each lever. Arm 1644 connects via a slip-in push link 1966/23D3 to a long cross lever 1363/23E3 under the differentials, and moves the clearing arm 1247 forward by 2mm or 6mm to engage with the racks for Register I or II. A connecting linkage 2535/28D3 between the two key levers raises lever II half a step vertically on its (slotted) pivot if lever I is pressed simultaneously, so that the clearing arm moves 4mm and engages both racks at once.
The vertical ends of the key levers also push rearwards on a long horizontal link 1372A/36Fig2 along the bottom of the side plate. This link has a triangular slot which engages a pin on the left-hand differential locating arm 1249, forcing the gears into neutral during the clearing cycle. The rear end of sliding link 1372A disengages the drum gear clutch (Register IV) via an intermediate lever (not shown). The front end has an interlock lever 1438/31F4 which prevents the link moving backwards if the brake arm is raised. Link 1372A has a return spring at the front, but also has a hook which engages with a mainshaft cam to ensure a positive release of the differentials at the end of the cycle.
The clearing key levers are held down during the cycle by a latching bail 1364/23B4 which engages with projections on the vertical arms. The latch is released by a mainshaft cam at 315°, but the key levers are held down by the pin-and-slot on the LH brake/switch arm until the brake arm drops at 360°.
The fore-and-aft positioning of the clearing arm 1247 is blocked if the right-shift lever is down (and vice versa), via a sliding link in the right-hand rear corner. The shift and clear operations are also interlocked via brake/switch system.
The long lever 2033/26C3 carrying the "0" key is pivoted near centre of the LHS. A shaped slot near the front of the key engages with the pin on the left-hand brake/switch arm and prevents the key from moving if the brake arm is raised, otherwise, pressing the key moves the switch arm forward and starts the motor. A triangular slot at rear of the key lever forces the LH differential positioning arm 1249 into neutral. There is no latch on the key lever - once the key is released by the operator, the brake arm rests on its disk for the remainder of the cycle, and the key is held down only by the pin and slot.
A vertical arm on the key lever extends downwards through the base and engages with a lever 2186/26C3 on a large fixed post on the underside. Lever 2186 rotates L-shaped lever 2264/26C3, bringing the notch at its far end into engagement with the tail of lever 2011/26E2 on the inside rear plate. Lever 2011 is pulled to the right on every machine cycle by the clearing cam 2562 and the horizontal link 1491/26E2. This motion is transferred from the back to the front of the machine through a series of four links and levers (2264, 2042, 2041, 2049), and finally pushes the Register V clearing rack 1844/26B5 to the right. The levers are reset by a large spring. The cycle stops when the operator releases the key and the brake arm drops at 360°.
The Division Setup key on the left-hand side clears Registers I and II, moves carriage to the far right, and transfers the keyboard setting to RI without advancing RII. The automatic carriage control and clearing mechanisms are common to both multiplication and division, but there are no drawings specifically for the division programming mechanism.
The automatic register clearing is accomplished by a third (keyless) clearing lever 1402 (11B1, 27, 36Fig2) located alongside those for RI and RII. The step under the tail of this lever moves the clearing arm 4mm to engage both register clearing racks. The auto-clear function can be disabled by pulling the step out of the way with the knurled pin protruding from the lower LHS of the machine (27).
As the Setup key is pressed, a triangular pin pushes down and forward on a rearward extension on the Repeat key, ensuring that it is not locked. A small pin near the front of the Setup key then presses Repeat down (without locking) so as to retain the keyboard setting. A large pin on the lower extension of the Setup key moves under the hook at the front of the Register II rocking lever 1478/21C2, blocking RII operation for the duration of the process.
The auto-clear lever 1402 is pulled down by a vertical sliding link 1698A/11B3 on the inside face of the side plate, just forward of the sliding link for the Repeat key. Link 1698A is pressed down by an inverted-L lever, operated via a pin and link from a downwards arm on the Setup key shaft. (The arm is on the outside of the side plate, the link and lever are on the inside).
The bottom of Setup key outside arm presses downwards on a horizontal lever, which pushes the pin on the LH differential positioning arm rearward into the add position. A spring-loaded scissor lever at the end of this lever allows the positioning shaft to be forced back to neutral during the shift and clear cycles. A pin at the bottom of the Setup key outside arm operates a long curly-headed lever on central zero-key pivot, which pushes forward on the pin on the LHS brake/switch arm and starts the motor. The Div Setup key is held down by a latching lever on the inside of the LH side plate. The auto-clear key is held down by a tag on the vertical sliding link 1698A, and by same latching bail 1364/11B3 that holds the manual clearing keys. The machine commences a clear cycle as previously described.
The long horizontal link 1372A/36Fig2 at bottom inside LHS (described in RI/II Clear) has a smaller sliding link 2546 attached to its rear end. This smaller link is normally sprung forward, and does not move when the manual clearing keys are operated. The tail of the auto-clear lever 1402 pushes both links rearwards, so that in addition to disengaging the Register IV clutch, a ramp on the rear end of link 2546 raises the left-hand end of the horizontal clearing-cam link 1491/5C7 around the corner on the rear plate. This raises a notch near the end of link 1491 into engagement with a pin on an L-lever 1488/5D7 in the bottom corner of the back plate. As the machine performs the clearing cycle, the link 1491 pulls the vertical arm of the L-lever inwards, where it is held by a latching lever 1444/5E5 on the back plate.
The horizontal arm on the L-lever 1488 raises the rear end of a heavy horizontal lever 1774/25C3 at the bottom rear of the LHS. The front of this lever presses down on the horizontal arm of another L-lever 1770/25A4 near the bottom front of the LH side plate. The vertical arm on lever 1770 pushes rearward on a pin on the inside vertical sliding link 1698A/25A4, disconnecting it from the auto-clear lever 1402/25B3. The auto-clear lever releases when the clearing-key latch bail 1364/25C3 is tripped by the mainshaft cam at 315°, completing the auto-clear cycle.
As the rear of horizontal lever 1774/25C2 is raised during the clearing cycle, its forward end presses downwards on a forked link 1776/25B4 to the underside of the machine. Underneath, this link rotates the auto-shift control shaft 1891/9B3 and lifts the long rearward arm 1623/9D3 to a position parallel with the base of the machine. The tail end of arm 1623 engages with a trip mechanism which operates the shift request shaft 1439/9C4.
The operating pin 6.568/9E2 at the end of the rearward arm 1623 is on a sliding link which is normally held forward, so that the pin is under the small trip lever 1604/9D3. As arm 1623 rises it pushes the trip lever 1604 forward, rotating the shift request shaft into the right-shift position via levers 1750/9D2 and 1762/9D2. The machine commences to perform continuous right-shift cycles.
As the carriage moves into the far right position, a tag on the carriage position sensing rack releases the latch 1444 on the rear plate. The shift control levers then return to their rest positions, and the shift clutch disengages normally at the end of the cycle.
The machine now commences an add cycle to transfer the keyboard digits to Register I. Actually, it has been doing add cycles all along, but the differentials are forced into neutral during the clears and shifts, and RII is disabled whenever RI is in neutral - as well as by the interlock pin on the bottom of the Setup key.
As the carriage moved fully into the rightmost position, a small ramp at the left-hand end of its front support rail operated via two levers 2906 (similar to 3768 on Dwg 2869) and 2916A (not shown) to pull rearward on the Repeat key, releasing it from under the pin on the Setup key and allowing it to rise. With the Repeat key released, the mainshaft cam clears the keyboard towards the end of the addition cycle. A pin on the inside of the keyboard clearing link releases the latch which holds the setup key, and the process ends when the brake arm drops at 360°.
At this stage the carriage is in the far right position, the keyboard entry has been transferred to the accumulator, and the keyboard and counter registers are clear. The machine is now ready to commence the division procedure.
The division process involves the Div and Div Stop keys, and two levers named Div +/- and Emergency Stop. It is controlled by a six-layer auxilliary cam driven by intermittent gearing from the right-hand end of the mainshaft.
The Div key 1430/2D3 pivots on the inside of the RH side plate, between the + and - keys. A vertical arm on the key lever passes through the side plate and prevents the key moving if the brake arm is already raised. Otherwise, the key arm pushes forward on the vertical arm on the brake assembly, raising the brake and starting the motor. A forked link on the inside of the key presses down on the rearward arm of the Repeat cross-shaft 1709 and pulls the Repeat key down on the LHS.
A forward extension on the Div key passes through the side plate at 2A5 and operates a small curved lever 1810 (not shown). Lever 1810 pushes the horizontal +/- link 1332/2D6 forward into the minus position. The Div key extension also blocks the manual shift keys, which are already blocked because brake arm is raised. The Emerg Stop key 1305/2C3 springs forward, latching the Div key down. A pin on the Emerg Stop key rises, releasing the forward arm on the 4-way trip lever 1276 (RHS outer rear, on the major pivot post above and behind the mainshaft. As the Div key reaches bottom, it presses a pin on a horizontal lever 1290 (not shown) above the mainshaft, raising the latch on its rear end clear of the upper arm on the 4-way lever. The machine starts to perform continuous subtract cycles.
When the accumulator goes negative a carry propagates across the machine. A long horizontal lever just forward of the carry sense lever detent bar transfers the final carry (from digit 11) across to the RHS. The cross lever pushes rearward on a vertical trip lever 1490/2D5, releasing the rearward arm on the 4-way lever at 300°. The 4-way lever is pulled clockwise by a stiff spring from the top of the division cam bracket. As the lever rotates, a ramp on its lower arm engages with the second layer on the division cam assembly, and attempts to rotate the cam CCW into engagement with the intermittent drive gear on the mainshaft.
The intermittent gearing picks up the division cam via the 4th layer at 325°. The innermost cam pushes rearward on a heavy horizontal link to the differential positioning arm 1240/2E6, forcing the arm rearward against the spring-loaded levers and into the add position. A forked lever halfway along the link connects through the side plate to RII slider assembly, reversing the direction of the counter register. This movement is completed by 15°, so that the machine cycle will perform an addition, reversing the overdraft. The second layer on the division cam pushes back on the 4-way lever and resets the trip lever at 25°. The division cam completes one-third of a turn by 40° mainshaft rotation, and then stops.
At 325° on the add cycle, a pin on the drive gear engages with a single tooth on division cam layer 5, picking up the intermittent gearing again. Cam 1 releases the reversing link, and cam 3 operates via a small intermediate lever to trip the shift request shaft 1439/9C4 clockwise at 355°. The machine commences a left shift cycle. The division cam completes its second third of a turn by 40°, then stops.
Another tooth on cam 5 picks up the gearing at 325° on the shift cycle. The carriage shift completes at 360°, allowing the differentials to return to the minus position. The machine continues with subtract cycles in the new carriage position. The division cam completes its final "do-nothing" third of a turn, and returns to its starting position at 40° on the next machine cycle.
When the carriage moves into extreme left position, a ramp at the right-hand end of its front support rail presses down on a shoulder on the Div Stop key (not shown). The machine completes the shift and continues with subtractions in last place until the carry trip occurs. At this stage it is necessary for the machine to reverse the overdraft and then stop.
As the reversing link is pushed rearward by cam 1, a pin on its inner side raises the rear end of a lever pivoted on the Div Stop key. Because the pivot is now lower, the front of this lever presses down on a pin on the Emerg Stop key 1305/2C3, forcing Emerg Stop rearwards and releasing it from the Div key. The Div key rises slightly, but is held by the tail on its outside vertical arm, which is now behind a projection on the raised brake lever. The brake lever is being held up by an extension on its interlock lever, which is held up by the sixth (outermost) division cam during the add cycle.
The machine completes the add cycle, picks up the division cam again at 325°, and commences the shift cycle. The carriage is already at end of its travel, so the shift cycle will have no effect on the carriage or the registers. Division cam 6 releases the interlock lever at 40°, allowing the brake arm to drop onto its disk. The shift cycle continues.
The division cam commences its third stage (return to home position) at 325°, but the brake lever drops at 360°, stopping the machine and releasing the Div key. The top latch lever drops to lock the upper arm on the 4-way lever. The final do-nothing stage of the division cam rotation will not be completed until 40° into whatever cycle the machine does next.
If the operator presses the Div Stop key, the machine will terminate the division in an orderly fashion (as above) at the completion of the current digit. The lever can be latched down by a notch in the front of the key stem, which engages with the cutout in the keyboard baseplate. The latch is released by a small lever which pushes the Div Stop key rearward when the Div key rises.
The Emergency Stop key releases the Div key, which will stop the machine immediately (at the end of the current cycle) if pressed during subtractions. If pressed during the add cycle, division cam 6 will hold up the brake lever and the Div key, ensuring that the add and shift are completed before stopping.
The Div +/- key (not shown) operates via two intermediate levers to move the pivot point of the small forked link near the centre of the division reversing link. This sets the initial direction of the counter register to normal or complement, while ensuring that the direction reverses automatically during the add cycle. The key is locked by the brake arm interlock lever while the machine is running. A spring-loaded plate behind the lever presses on the underside of the keyboard base plate to provide a secure detent.
The Multiplier Bar across front of machine is supported by two side arms and a heavy cross shaft. The arms on the right and left sides operate mechanisms for Stage 1 and Stage 2 respectively, depending on status of the multiplier register RV. An interlock lever at the inside top front of the RH side plate blocks the Multiplier Bar if Div or the manual shift keys are down.
If the multiplier register is empty, the Mult Bar initiates a Stage 1 cycle. This transfers the keyboard setting into RV and positions the carriage to the far left. The operation is controlled by a heavy Stage 1 lever 1459/18D3 on a long bushed pivot at centre of the multiplier RH side plate.
If Register V stands at zero (18Fig12), the fingers 1469/18C6 on the front zero-detect shaft 1709/18C7 will fall into the notches in the front faces of the stepped collars 1455/18C6, and the shaft will rotate rearwards. A short arm on the RH side of the zero shaft allows a vertical arm 1462/18D6 attached to the Stage 1 lever to spring forward (18Fig13). A notch near the top of arm 1462 catches under a tag on the right-hand Multiplier Bar arm 1453/18D6, so that pressing the bar pushes down on the Stage 1 lever. A triangular slot in the Stage 1 lever engages a screw-in pin 7.036/10C3 at the forward end of the RHS +/- sliding link 1332/10D2, setting the differential positioning arm to neutral. Alternatively, if the sliding link is already held in the + or - position by some other operation, the pin will block the Multiplier Bar movement.
A sloping slot near the front of the Stage 1 lever engages a pin and roller on the transfer shaft positioning bail 1647/18C7. As the lever moves down, the bail pushes the transfer shafts rearward through the stepped collars to engage with the gears on the front of the addition unit. This state is shown in 18Fig9. The bottom of the Stage 1 lever presses down on a forward arm 1759/10C3 on the brake/switch shaft, raising the brake arm and starting the motor.
The transfer shaft bail has large vertical arm 1624/10A3 at the front LHS, which also moves rearward unless blocked by interlocks from the RI/II and RV clearing keys. A clip-on link from this arm operates a small L-lever 2566/36Fig2 which releases the Repeat key if it was latched. The upper pin on the transfer bail arm 1624 connects via a chain of 4 links and levers (4095, 4098, 3804, 3915 on sheet 2869) towards rear of machine, eventually pushing rearward on a short arm 3788/2869 on the left-hand end of the shift request shaft and engaging the left-shift clutch.
As the Multiplier Bar moves down, the brake/switch arm 1552/31E3 on the LHS moves forward. A pin and spring pull forward on the vertical arm of a large L-lever 2454/31F4 that pivots on the brake shaft at the bottom front of the side plate. When fully forward, a square pin at the top of this arm allows a spring-loaded lever 4089/2869 on the upper central interlock pivot to rise, latching the transfer shaft bail arm rearward and the vertical arm forward. A projection on the vertical arm holds the switch arm forward via its lower pin.
When the Multiplier Bar reaches the bottom, the Stage 1 lever is held down by a triangular pin D521/32A3 near its front engaging with a latching lever 2440/32A3 on the outside of the RH side plate. The Multiplier Bar is free to rise when released by the operator. The machine commences a left shift cycle. The carriage registers are disabled during the shift cycle, but the addition unit and stepped drums still rotate. The keyboard setting is transferred through the meshed gears into the multiplier as the mechanism rotates during the shift cycle.
With the Repeat key released, the keyboard will be cleared towards the end of the first shift cycle so that further cycles will not affect the multiplier register. At 320°, the latch 2440 holding the Stage 1 lever on the RHS is released by the mainshaft cam and link 2551/32C3 (previously described under the shift keys). The Stage 1 lever rises, releasing the transfer shaft bail pin on the RHS. However, the bail is still held rearward by the latch 4089/2869on the LH vertical arm. This also holds the left shift request arm rearward, so the machine continues to make left shift cycles.
As the carriage moves into the far left position, a raised section on the face of its front support rail engages with a horizontal sliding link 3813/2869 at the top of the LH side plate and moves it forward about 1mm. The sliding link operates via an intermediate link 4096 to release the latching lever 4089 that is holding the transfer shaft bail arm and the switch arm. This releases the shift request, but to make doubly sure a separate curved link 3923/2869 from the slider 3813 raises the pivot point of the final lever 3915 so that it no longer presses down on the shift request arm. The machine completes the shift cycle and stops.
At this stage the carriage is at the far left position, and the first number has been loaded into the multiplier unit and displayed in Register V. The carriage registers have not been cleared, and still retain their previous contents.
When the multiplier register has been loaded (from Stage 1, a back-transfer, or by manual setting), the Mult Bar initiates a Stage 2 cycle to perform the multiplication. Stage 2 involves the Mult Bar, Mult +/- Lever, Non-Return Lever, and the Register V Lock Button. The process clears the carriage registers, performs the add-and-shift cycles, and (optionally) clears the multiplier register and returns the carriage to the left-hand side on completion. It is controlled by a large Stage 2 lever assembly pivoted at the front LH side of the multiplier unit. It uses the same auto-clear and shift control mechanisms described previously under Division Setup.
The Mult +/- lever 1681/11D5 at the front left allows the result to be added to or subtracted from Register I. This lever operates via cross shaft 1824/11E6 to position the long +/- link 1332 on the RHS. The operator only moves the control lever a short distance either side of centre. As the Stage 2 lever descends, a V-shaped pin engages with the inverted-V projection on the +/- lever to complete the movement and latch the lever in position. The counter register can be set independently to normal or complement mode by the Div +/- key, as previously described.
The zero-detect shaft 1709 will be rotated forward if there is a value present in any of the RV dials (see 18Fig5). This shaft pushes the right-hand vertical arm 1462 rearward, disengaging it from the RH Multiplier Bar arm. An arm 1664/18B3 on the LH end of the zero-detect shaft moves forward, allowing a hook 1658/18A2/11D1 on the inside of the Stage 2 lever 1642/11D1 to catch under a pin on the left-hand Multiplier Bar arm. The Stage 2 lever is blocked by a pin on the inside of the LH brake/switch arm if the machine is running, otherwise it is pulled down as the Mult Bar moves. A forked link 1632/11C2 on the outer side of the lever pushes the Repeat key down via the horizontal arm 2162/11C2. The Stage 2 lever 1642 is held down by its front vertical arm, which engages with an inverted-L latching lever 1696/11D2 near the bottom front corner of the side plate. The Multiplier Bar is free to rise when released by the operator.
At the bottom of its stroke, a short pin at the top of the Stage 2 lever presses down on a horizontal latch 1659/17A6 at the top of the multiplier side plate, releasing a spring-loaded vertical lever 2171/17A6. This lever pushes forward on a horizontal slider 2089/17B1 with sufficient force to push the inner pin on the brake/switch lever arm (not shown) forward, raising the brake arm and starting the motor. A small pawl 2090/17A1 on the slider raises the locking pawl 1703/17A2 which holds the pinshaft sector 1635/16B3 in its home position, and a latch arm 1856/17A2 holds it clear. The pinshaft springs clockwise until the raised pin (the rightmost, with the carriage in the left-hand position) contacts the lowest tooth on the stepped collar on the corresponding multiplier shaft. A tiny pawl 2526/16B3 (often removed) prevents the pinshaft sector from bouncing back.
As the Stage 2 lever moves down, a long pin 7.049/11C2 on its rearward extension pushes down on the vertical slider 1698A which operates the RI/II auto-clear lever on the inside of the LH side plate (described previously under Div Setup). The auto-clear cycle proceeds initially as before - the clearing arm operates, the clearing link on the rear plate is raised, the levers around the left rear corner release the vertical slider and auto-clear levers, and the shift control shaft (underneath) is raised to the first position.
Two things are different about the auto-clear cycle this time. First, the pinshaft sector has been released and has moved clockwise, releasing the vertical arm 1628/11C3/13B4 that hangs from its shaft. This releases link 1715/13B5 and allows the slider on the auto-shift arm to moved rearward. When the arm rises, the operating pin moves to an "armed" position directly behind the pawl 1604, rather than tripping it immediately to start a carriage shift as it did during Div Setup (see 9Fig1a). Second, because there is no carriage shift, the levers involved in raising the shift control arm remain held in position, ultimately by the latch 1444 on the rear plate (9Fig1b).
As the auto-clear cycle proceeds, the pinshaft sector operating pawl 1617/11A2 is pushed forward by innermost mainshaft cam, reaching maximum stroke at 70°. To ensure that the pinshaft is not disturbed during the clearing cycle, a right-angled extension on the auto-clear lever 1402/11B1 presses down on the operating pawl, holding it clear of the pinshaft sector. The operating pawl pushes forward on the tail of lever 1856/16A2 that is holding up the sector locking pawl, allowing the locking pawl to spring back into engagement with the sector. A pin on the back of the operating pawl presses forward on the vertical lever 2171, which resets the spring and latch for the top horizontal slider. (This operation takes considerable force). The slider itself is held forward by a latching pawl 2102/16B1, keeping the brake/switch arm forward and the motor on. The auto-clear lever is disengaged from the vertical slider 1698A at about 140°, and is released by the clearing-key bail at the end of the clear cycle.
The machine now commences to perform addition cycles. The sector operating pawl strokes forward on every cycle, lifting the anti-bounce pawl and ratcheting the pinshaft sector one step CCW for each addition. The number of additions required is determined by the length of the corresponding tooth on the stepped collar, or rather, by the distance the pin travelled to contact the end of the tooth.
On the last addition, as the pinshaft sector is pushed into its home position, a short pin 6.55/16B3 on the face of the sector pushes forward on the hanging arm 1628. This arm pulls forward through link 1715/13B5 to sliding link 1712/13D5 on the shift control arm under the machine. The operating pin on the rear end of this arm is standing just behind the right shift pawl on the shift request mechanism. The pin is pulled forward as the sector is pushed home, tripping a shift request. The machine completes the current add cycle, then commences a right shift cycle. The sector operating pawl strokes harmlessly against a "missing" tooth when the pinshaft is in its home position.
As the carriage moves right, the position sensing rack 1337/25E1 operates through the intermediate gears to rotate the multiplier camshaft 1590/11C7 CCW by one position. The second cam raises the pinshaft pin for the next digit to the left, via the forward arm on its follower 1732/11C7. As the shift completes, the ratchet wheel 1588/16A3 on the end of the camshaft raises and then drops the vertical forked lever 1713/16A2. The top of this lever is held forward by the top sliding link, so that it will engage with the trip pin on the sector locking pawl 1703. The locking pawl releases momentarily, allowing the pinshaft to spring forward to the position selected by the second digit. The pinshaft sector releases the hanging lever, and the shift control slider returns the operating pin to its rear position, cancelling the shift request. The machine finishes the shift cycle and then resumes addition cycles in the new position. This process repeats for each digit.
The second zero-detect mechanism at the rear of the multiplier unit serves to terminate the multiplication when all digits to the left of the current position stand at zero. A set of spring-loaded vertical fingers 18Fig1 are located under the notched disks towards the rear of the transfer shafts. A small lever 1661/17E1 on the inside LH side of the multiplier allows the fingers to rise only when the Stage 2 lever is down. The sensing fingers are cascaded in such a way that those to the left of the leftmost non-zero digit will rise, and the rest will be held down and inoperative. As the carriage moves into each new position, a second vertical arm on the follower lever 1732/18C1 tests the corresponding sensing finger by pushing rearward. If the sensing finger is raised, a tag engages with the testing finger and the zero-detect shaft 1741/18B1 is rotated rearwards.
This motion is transferred through arm 1811/18B2 to a small sliding link 1812/2D4 on the bottom inside face of the outer right-hand side plate. This link pushes a second small lever 1814/2D4 into the path of a cam on the mainshaft, which picks it up at 320° and pushes it further (see 10Fig7 and 8). The tail of lever 1814 engages with an arm 2355/9B3 on the shift control shaft under the machine, raising its operating arm into the second (higher) position as the mainshaft rotates from 320° to 360°. Pin 6.337/9D4 on the shift control arm engages a forward extension on lever 1750, rotating the shift request shaft 1439/9C3 into the left shift position at 350°. The operating arm is latched high by a spring-loaded lever 1888/9D4 at its rear end, so the machine will now begin to execute continuous left-shift cycles.
As the carriage moves left on the first cycle, a pin 6.395/25E1 on the inside of its position sensing rack trips a spring-loaded pawl 1446/25E1 at the top of the latching lever 1444 on the rear plate. There is a separate pin for each carriage position. Tripping this latch releases the levers that held the shift control arm in the first position. The arm remains latched in its second position by lever 1888/9D4.
As the shift control shaft rotates to its second (high) position, its innermost arm 2027/9C2 pushes rearwards on a link 2024/9D5 which is supported at its rear end by a guide pin on the switch bracket. This link pushes the Register V clearing link 2264 into the path of the operating lever 2011 in the back centre (underneath), which clears the register during the first left-shift cycle. Pressing and latching the Register V Lock Button on the front of the machine pushes link 2038/9B7 rearward, raising the front of link 2024 clear of the operating pin and disabling the auto-clear function (9Fig8). Clearing RV with the Zero key causes a ramp on the intermediate link 2041/9C6 to lift link 2024 (9Fig7), while a second ramp on the final clearing link 1844/16C6 releases the latch and allows the pushbutton to return.
As the carriage shifts left into its home position, a cam 1679/13C3 near the left-hand end of the multiplier camshaft pushes forward on a link 2261/13B3, releasing the Stage 2 lever latch 1696/13B3 at 170°. As the Stage 2 lever rises, a pawl on its inside face trips the pawl 2102/16B1 holding the top sliding link. The link is pulled rearward by a light spring, releasing the pin on the brake/switch arm. As the sliding link moves back, the vertical link 1713 which trips the sector locking pawl at each right-shift is moved rearward and out of engagement, ensuring that the pinshaft and sector remain locked in the home position. A light link 1887/13D3 attached to link 2261 releases the latch 1888 holding the shift control arm arm at 210°, returning the shaft to its rest position and cancelling the shift request. The motor stops when the brake arm drops at the end of the cycle.
In normal operation as described, the machine uses the "all zeros to the left" detector to terminate the multiplication, and it has to shift into the first of the zero positions (one step too far) in order for the sensor to operate. If the multiplier uses all 10 places there will be no zeros to the left, so a different method must be found to terminate the process.
A lever 2122/18Fig4 attached to the right-hand side of the zero detect shaft is normally held above a fixed pin 6.524 on the top of the pinshaft 1470 by a notched cam 2123 on the multiplier camshaft. The lever falls into the path of the pin when the cam drops on reaching the rightmost (digit 10) position. As the pinshaft is pushed back into its home position on the last digit, the fixed pin contacts the end of the lever and pushes it rearward, rotating the zero shaft 1741. This movement is completed by 70°, in time for the auto-shift cam to pick up at 120°, so that the carriage return commences as soon as the last addition is completed.
If the carriage return is not desired, the Non-Return lever 2184/13E6 at the front of the machine (to the left of Register V) is placed downwards, raising a projection on the forked lever 2071/13C6 towards a release pin on the downwards vertical arm of the Stage 2 lever latch. As the shift control shaft rotates to commence the left-shift cycles, an arm 2255/13B7 raises the rear end of lever 2071 so that its rear end aligns with a pin on the sector operating pawl, and the projection aligns with the release pin. As the machine commences the first right shift, the pinshaft operating pawl pushes forward on the tail of lever 2071,pushing the projection against the pin on the latching lever and releasing the Stage 2 lever. The machine completes the shift, reversing the "one step too far", and stops. The carriage must always make at least one return shift, even if the multiplication was terminated by the "fake" zero in the tenth position, in order to release the shift control arm first position latch on the rear plate.
If the Multiplier Bar was held down by the operator, there would be trouble terminating the multiplication. As the carriage moves into the rightmost position, a pin on the tenth (leftmost) camshaft finger operates a long curved lever 2154/17E4 on the inside of the multiplier side plate, releasing the hook 1658 that connects the Stage 2 lever to the Multiplier Bar arm. The lever can then rise when the latch is released, regardless of the position of the Multiplier Bar. As a side-effect, this also means that a multiplication can not be started with the carriage in the far right-hand position.
The Back Transfer function transfers the contents of the ten digits of the accumulator register at the current carriage position into the multiplier register RV, and returns the carriage to its leftmost position. It assumes that Register V has been cleared manually, or automatically by the previous multiplication.
The back-transfer key 1969A/13E2 pivots at the top front of the LH side plate, and presses down on a large inverted-L lever 1726/5D2/31G3 that pivots near the top rear (see also 3839 and 3838 on sheet 2869). The key is held down by a square pin which latches under the front of the top horizontal slider 3813/2869 (described under Multiplier Stage 1). The back-transfer lever 1726 is held down by the key lever at the top, and by a tail at the bottom of its vertical section engaging with a pin on the outer side of the clearing-key latch bail 1364/23B4.
As the lever is pushed down, the bottom of its vertical section pushes rearwards on a horizontal sliding link (not shown) which disengages the Register IV clutch lever at the rear of the machine. A pin near the bottom of the vertical section raises a small forked lever 1822/23B1 to block the movement of the counter register rocking arm. A second pin further up the lever raises the front of another differential positioning lever 1734/5C2, pulling the gears into their forward (subtract) position. The highest pin on the vertical arm connects via a light diagonal link 3930/2869 to the front of a machined horizontal slider 3804/2869 located towards the bottom centre. As the slider is pulled rearward, a step on its rear face pushes against an upward extension on the clearing arm positioning lever 3972/2869, moving the clearing arm 1363 into the RI position.
A shaped slot at the front of the back-transfer lever pushes rearward on transfer bail positioning arm, moving the multiplier shafts upwards and rearwards into engagement with the addition unit. The clip-on link 2567/36B4 on the positioning arm releases the Repeat key. The positioning arm pushes rearward on link 4095/2869 and raises the rear of lever 4098, as in Multiplication stage 1. However link 3930 has pulled slider 3804 rearwards, so that the tail of 4098 misses the top pin on the slider and does not initiate an immediate shift request. A ramp on the front face of the back-transfer lever pushes forward on a pin on the release arm 1555/28B7 on the keyboard, ensuring that no keys can be engaged during the transfer. A second shaped slot on the back-transfer lever pushes forward on the pin on the LH brake/switch arm, raising the brake arm and starting the motor.
As the clearing arm pulls the accumulator digits back to zero, the motion is transferred back through the differentials, rotating the addition unit shafts clockwise. The multiplier shafts rotate CCW the same distance, and advance the Register V numerals clockwise. The motion is completed by the time the addition unit shaft locks re-engage at 180°.
As the transfer cycle completes, the leftmost cam on the mainshaft begins to lift the rear of the horizontal slider 3804/2869 at 280°. A pin on the rear of the slider raises lever 3915/2869, which trips a left shift request via lever 3788. The clearing arm lever 3972/2869 is released from the notch in the slider at 320°. Lever 3972 springs forward, holding the slider in the raised position and maintaining the shift request. The machine now starts to perform continuous left-shift cycles.
As the carriage returns to its leftmost position, the ramp on the face of the front support rail presses forward on the upper horizontal sliding link 3813/2869. The curved link 3923 from the slider releases the lever 3915 holding the shift request arm by raising its pivot at 210°. The lower slider 3804 springs forward and drops as lever 3792 re-engages in its notch. The front of the top slider 3813 releases the back-transfer key at 220°, and the clearing-key latch bail releases the tail of the back-transfer lever at 310°. The lever rises and the motor stops when the brake arm drops at the end of the cycle.
The Register IV lever engages or disengages a dog clutch which drives the Register IV drum gear at the rear of the machine. The lever operates a horizontal sliding link at the lower rear of the left-hand side plate, then via a lever across the back of the machine to the clutch on the shaft extending rearwards from the clearing cam. The register is disengaged automatically to preserve its contents during RI/II clearing cycles.