The new arrival shown in the previous post has a carriage and even a bell - mounted on the cast-iron base-plate. The larger view from the rear with the covers off shows the bell, the input-check register on top and some of the safety-interlocks to the side of the register.
The front view without the main covers shows the pinwheel drum and the carriage with the result-register and the revolution-counter - all with 10s-carry. The bell rings the alarm when there is an overflow (or an underflow) in the result-register - very nifty. (A very clear demonstration of the workings of a Thales machine can be seen at this link.)
The 'paddles' on the front of the carriage are for stepping left or right - squeeze both for carriage-release. The crank at the right is of course for driving the mechanism, either adding (cw) or subtracting (ccw). The wing-nuts at the carriage-ends are for clearing the result- and revolution-counters.
The drum with pinwheels is from brass and steel, fortunately no zamac anywhere. In the picture above the pinwheel itself is shown with the first four number-wheels showing 4, 3, 2 and 1 set, i.e. four of the pins 'up' on the first wheel, etc.
Even though all it does is adding or subtracting the number on the drum (EW - entry, on top) to the result register (RW - results, lower right), with the extra revolution counter (UW - turns, lower left) on a sliding carriage it enables a whole host of calculations. Repeated addition is fairly simple multiplication - the tens-carry in the 'UW' helps reduce the the number of turns (e.g. 89 x 89 reduced to 3 turns from otherwise 17 turns). Together with the bell to alert on underflow, repeated subtraction allows for quick long-division.
With a simple extra 'trick' it is e.g. possible to do exponents. As example; when wanting to know the precise amount of cubic cm in a cubic inch, that would be 2.54 cm to the power of 3. First multiplying 254 by 254, gives the square in the 'RW'. By then working from left to right on the 'UW', add turns to make the 'UW' copy the digits in the 'RW'. (Working left to right preserves the next digit to work on, no need to keep notes.) This then results in the 3rd power to be in the 'RW' - giving 2.54 cubed as 16.387064. (Repeating this same copy-to-'UW' procedure of course keeps raising the power.)
Another not immediately obvious technique is to split the 'EW' and 'RW' in two areas, e.g. to be able to do a proportions calculation in one setting.
Overall a fascinating little machine that is surprisingly heavy - packed dense with gears and levers - with much to discover. Not certain if the '0' to '9' issue on that single digit can be fixed, but with some light cleaning/oiling and occasional exercise it should remain 'stable'.
An ~80 year old and very ingenious digital machine :-)
