in 1974 I needed to make boxes for housing electronic projects.
To do this I made myself a very crude sheetmetal folder out
couple of pieces of angle iron hinged together and held in a vice.
To say the least it was very awkward to use and not very
versatile. I soon decided it was time to make something
I got thinking about how to make a 'proper' folder. One thing that
concerned me was that the clamping structure had to be tied back to the
base of the machine either at the ends or at the back and this was
going to get in the way of some of the things that I wanted to make.
So I made a leap of faith and said ...OK, lets not tie the
clamping structure to the base, how could I make that work?
I could support the clamping member from the ceiling of my workshop?
Well that could work, but then, in effect, my workshop
would be the thing that was attaching the clamping member to the base
of the machine.
there some way to break that connection?
you hold onto an object without attaching something to it?
seemed like a ridiculous question to ask but once I had framed the
question in that way I came up with a possible answer:-
influence things without a physical connection to them ... via a FIELD!
knew about electric
and magnetic fields*.
But would it be feasible? Would it actually work?
As an aside it is interesting to note that modern science is yet to
fully explain how "force at a distance" actually works).
happened next is still a clear memory.
was in my home workshop
and it was after midnight and time to go to bed, but I
couldn't resist the temptation to try out this new idea.
found a horseshoe magnet and a piece of shim brass.
I put the shim
brass between the magnet and its 'keeper' and bent the
brass with my finger!
worked. The brass was only 0.09mm thick but the
principle was established!
photo at left is a re-construction of the original experiment but it is
using the same components).
was excited because I realised, right from the start, that if the idea
be made to work in a practical way then it would represent a new
concept in how to form sheetmetal.
next day I told my work
colleague, Tony Grainger,
about my ideas. He was a bit excited
too and he sketched out a possible design for an electromagnet for me.
He also did some calculations regarding what sort of forces
be achieved from an electromagnet. Tony was the cleverest person that I
knew and I was so lucky to have him as a colleague and have access to
his considerable expertise.
initially it looked like the idea
would probably only work for fairly thin gauges of sheetmetal but it
was promising enough to encourage me to proceed.
Over the next
few days I obtained some pieces of steel, some copper wire, and a
rectifier and built my first electro-magnetic folder! I still
have it in my workshop:
electro-magnet part of this machine is the genuine original.
front pole and bending beam shown here were later
rather crude this machine worked!
envisaged in my original eureka moment, indeed the
clamping bar did not have to be attached to the base of the machine at
the ends, at the back, or
anywhere. Thus the machine was completely open-ended and open-throated.
the open-ended aspect could only be fully realised if the hinges for
the bending beam were also a bit unconventional.
the coming months I worked on a kind of half-hinge that I called a
'cup-hinge', I built a better performing machine (Mark II), I
lodged a Provisional Patent Specification
with the Australian Patent Office and I also appeared on an ABC
television programme called "The Inventors". My invention was
selected as the winner for that week and later went on to be selected
as one of the finalists for that year (1975).
was the Mark II bender as demonstrated in Sydney following the
appearance on the final of The
used a more developed version of the 'cup hinge' as shown here:
During 1975 I metGeoff
Fenton at an Inventors Association meeting in Hobart (3
August 1975). Geoff was quite interested in
the "Magnabend" invention and came back to my place after the
meeting to have a closer look at it. This was to be the start
an enduring friendship with Geoff and later a business
was an Engineering graduate and a very clever inventor
He readily saw the importance of having a hinge design that
allow the machine to realize its full open-ended potential.
My 'cup hinge' worked but had serious problems for beam angles much
beyond 90 degrees.
Geoff became very interested in centerless hinges.
This class of hinge can provide pivoting around a virtual
which can be completely outside the hinge mechanism itself.
day (1 Feb 1976) Geoff turned up with a drawing of an unusual and
innovative looking hinge. I was amazed! I had never seen anything
remotely like it before!
(See drawing at left).
I learned that this is a modified pantograph
involving 4-bar linkages. We never actually made a proper
of this hinge but a few months later Geoff came up with an improved
version which we did make.
A cross section of the improved version is shown below:
'arms' of this hinge are kept parallel to the main pivoting members by
small cranks. These can be seen in the photos below. The
only have to take a minor percentage of the total hinge load.
A simulation of this mechanism is shown in the video below. (Thanks to
Dennis Aspo for this simulation).
hinge mechanism worked quite well, it was never installed on an
actual Magnabend machine. Its drawbacks were that it did not provide
for a full 180 degree rotation of the bending beam and also it seemed
to have a lot of parts in it (although many of the parts were the same
as each other).
The other reason that this hinge didn't get used was because Geoff then
came up with his: Triaxial
The triaxial hinge did
provide for a full 180 degrees of rotation and was simpler inasmuch as
it needed fewer parts, although the parts themselves were more
triaxial hinge progressed thru several stages before reaching a
fairly settled design. We called the different types The Trunnion Hinge, The Spherical Internal Hinge
and The Spherical
The spherical external hinge is
simulated in the video below (Thank you to
Jayson Wallis for this simulation):
One of the biggest problems with the Magnabend hinge was that there was
nowhere to put it!
ends of the machine are out because we want the machine to be
open-ended, so it has to go somewhere else. There is really no room
between the inner face of the bending beam and the outer face of the
front pole of the magnet either.
To make room we can provide a lips
on the bending beam and on the front pole but these lips compromise the
strength of the bending beam and the clamping force of the magnet. (You
can see these lips in the photos of the pantograph hinge above).
Thus the hinge design is constrained between the need to be thin so that only
small lips will be needed and the need to be thick so that it
will be strong enough. And also the need to be centerless so as to
provide a virtual pivot, preferably just above the work-surface of the
These requirements amounted to a very tall order,
but Geoff's very inventive design addressed the requirements well,
although a lot of development work (extending over at least 10 years)
was needed to find the best compromises.
If requested I may write a separate article on the hinges and their
development but for now we will return to the history:
Over the coming years we signed a number of "Manufacture-Under-License"
February 1976: Nova Machinery Pty Ltd, Osborne Park, Perth
December 1982: Thalmann Konstruktionen AG, Frauenfeld,
October 1983: Roper Whitney Co, Rockford, Illinois, USA.
December 1983: Jorg Machinefabriek, Amersfoort, Holland
(More history if requested
by any interested party).
This page updated: 14 March 2018.
Author: Alan Bottomley