Widget Of The Week
Guy’s Brittannic Calculating Machine, 1952?
In a rare break with tradition the featured item in this episode of
dustygizmos is totally mechanical in operation, i.e. no batteries are required
(or indeed any sort of electrical supply) to make it work. What makes the Guy’s
Britannic Calculating Machine vaguely relevant on a website largely devoted to
electrical and electronic gadgetry is that devices this were still being made
almost twenty years after the first electronic calculators appeared in 1952 and
ten years after the introduction of transistorised calculators in 1963. By the
early seventies the cost, size and performance of electronic calculators
finally consigned these old hand-cranked marvels to almost overnight
The Britannic, in common with many other mechanical calculators of
the time is based around an ingenious contrivance called an Odhner Pinwheel,
which in turn was based on mechanisms dating back to the seventeenth century.
More on the exotically named Wilgott Theophil Odhner, the chap responsible for
this revolutionary (pun intended) contraption, in just a moment.
This Britannic is capable of performing the four most
basic mathematical operations, namely addition, subtraction, multiplication and
division and can handle calculations of up 18 digits in length. Whilst it looks
fiendishly complicated operation is actually quite straightforward. It has
three numeric ‘Registers’ for entering or displaying numbers. The first one –
at the top is the bank of 12 levers. This is the Setting Register, the
equivalent of a keyboard on a modern calculator, where you input numbers, from
0 to 9. Below that, on a sliding carriage are the other two Registers. The one
on the left, comprising a bank of 10 digits is the Revolutions Register which
displays the number of rotations of the large crank handle on the right of the
instrument’s main body. Next to that is the Results Register, a bank of 18
digits, where, as the name implies, the results of calculations are shown. The
silver topped lever is for zeroing the Settings Register and the two small
cranks at either end of the sliding carriage are for zeroing the Rotations and
The actual Pinwheel is essentially a barrel, made up of
discs each one having 9 retractable teeth that pop in or out, according to the
number selected by the Setting Register lever. The teeth engage with gears that
drive the numeral wheels on the Results Register each time the handle is
Anyway, enough of that here’s a simple example of how it works,
and pay attention because you will be tested on it later… Let’s say you want to
add 631 to 294. Step one, move the three rightmost levers on the Setting
Register to 6, 3 and 1. Turn the large crank one rotation clockwise and 631
appears on the Results Register below. Clear the Setting Register by moving the
silver-topped lever upwards and enter the digits 294. Turn the crank one
revolution and the total 925 appears on the Results Register. If you had turned
the crank counter-clockwise the machine would have subtracted one number from
the other. Multiplication and division
simply involve rotating the crank one way or another multiple times, which is
where the Rotation Register comes in.
Needless to say there’s more to it, and much more that it can do, in the
right hands. Apparently skilled operators were able to match or even exceed the
speed of the earliest electronic calculators.
The Britannic featured here was made by a company called Guys
Calculating Machines of Wood Green in London, possibly in the early 1950s, for
reasons that will be explained later on. It’s hard to say exactly when as the
design changed little over the years but it was popular and apparently produced
in quite large numbers. This appears to be an unsual variant with a 12-digit
Settings Register; most of the others I have seen have 10-digit registers.
came from ebay and I stumbled across the auction listing a day or two before it
was due to end. There had been no bids – it happens a lot and the real bidding
often starts in the last few seconds -- nevertheless I added it to my watch
list, mainly out of curiosity to see how much it would sell for. I caught up
with it again five minutes before the auction closed and was surprised that
there still hadn’t been any bids. I decided to kick things off with a cheeky bid of
£5.00, and no real hope of it actually winning. Ten minutes later it was mine,
for 99 pence! I can’t understand why it had been missed, okay, it didn’t look
very pretty in the pictures and it was minus its wooden cover, but that
wouldn’t normally have put off serious collectors and restorers. As it turned
out it was really dirty and caked with dried grease and gunk but as you can see
the machine and its wooden base scrubbed up really well. There is a problem
with the mechanism, which keeps locking up. It’s probably nothing serious and
it feels like it just needs a complete stripdown, degrease and rebuild.
However, it also looks like the kind of job I would instantly regret, as tiny
springs and gears fly out all over the place. One day maybe but for the moment
it will be earning its keep as a rather splendid looking display piece.
What Happened To It?
Back now to pinwheel pioneer Wilgott Theophil Odhner. He was a
Swedish engineer and businessman, working in St Petersburg in the 1870s. The
idea came to him whilst repairing an early adding machine called a Thomas
Arithmometer. He believed it could be improved, and he was right, though it
took him 19 years to achieve his goal. Odhner’s pinwheel quickly became the
industry standard for mechanical calculators and was ruthlessly cloned and
copied by countless other companies around the world. One of them was Guy’s Calculating Machines, founded by Frank Guy
who started out importing calculating machines from Germany. Following a
request and some financial backing from the British Petroleum and Anglo-Persian
Oil Company (later just BP) Frank Guy produced a copy, and later a refinement
of the Odhner machine, called the Britannic, which is what you see here.
Initially they were made just for BP but by the 1920s they were being marketed
commercially, with Guy’s claiming it to be the only British Calculating
machine. Guy’s was sold to the Muldivo Calculating Machine Company in 1939.
This Britannic has a brass Muldivo badge with a Queen Victoria Street address
pinned to the wooden baseboard. The fact that Guy’s is stamped on the
calculator’s metalwork points to it being made close to 1952 which was when the
company moved to new premises in Salisbury Square, near London’s Fleet Street.
Muldivo continued making calculating machines and later switched to precision
engineering until it was wound up in 1969.
It turned out to be 99 pence well spent. Britannic machines are
not uncommon and the one’s I’ve seen on ebay recently have been priced at
between £100 and £250 in some cases in much worse condition than this one.
Antique and vintage mechanical calculating machines can fetch some very high
prices, three figures and beyond. It is clearly a specialist field and 99 pee
Britannics like this don’t turn up very often, but as this one proves, it can
and does happen.
First Seen: 1930
Original Price: £?
Value Today: £100.00 (0520)
Features: Odhner pinwheel mechanism, 12-digit
setting register, 18-digit accumulating register, 10-digit revolution register,
single-action rotor clearing lever, addition, subtraction, multiplication and
Power req: N/A
Dimensions: 260 x 120 x 100mm
Made (assembled) in: England
Hen's Teeth (10 rarest): 7