By dumbbell is meant, not a piece of exercise apparatus – though the original dumbbell was just that, simulating the action of bell ringing – but a weighted wheel in a frame which can be rung full circle in the English style, in which for each pull of the rope a bell turns ‘full circle’ from approximately upside down to approximately upside down, rotating in one direction at one stroke and the other at the next.
17th century dumbbell
modern mini-dumbbell, John Norris design
Unlike its 17th century predecessor a modern dumbbell can be linked by a sensor to ringing software on a home computer or dedicated ringing ‘simulator’
It then forms an excellent learning aid, providing opportunities for extra practice at times to suit oneself, facilitating the development of listening skills, ringing by rhythm and the learning of new methods. While not intended to be an end in itself, ringing a dumbbell is also challenging and fun, even though it lacks the 'apres-ski' of ringing in the tower.
There need be nothing ‘high tech’ about the theoretical design of a dumbbell but there can be considerable head scratching and experimentation involved when it comes to practical decisions on materials, size and weight. A dumbbell with a full size wheel, typically 4ft. in diameter, may pose significant space and stress issues for the average home.
The ‘mini’ dumbbell described in the downloadable DIY Instructions (5Mb) is designed for home use and can be installed in any convenient location with sufficient headroom beneath, typically in a loft with the rope falling through a ceiling boss to a ringing position on the landing beneath.
The design uses an MDF wheel, 22" in diameter, 2" thick and weighing approx. 10 lb, with cutouts in the upper quadrants and 6 lb of steel weights attached to the lower half. The wheel is mounted on a headstock in a wooden frame approx. 29" long and 17" wide, the overall height being 27". A ½" spindle through the headstock runs in self-aligning ball bearings and a papier maché bell is fitted to the headstock, the whole ensemble loosely representing a bell in a traditional frame. (The bell is little more than whimsy but takes advantage of the space provided by the frame width, designed for stability.)
To accommodate a mini-dumbbell to this design, space is required not less than 29" long, 17" wide and 27" high, plus a little extra to allow for access.
Connecting to a computer: Sensor and Interface
SENSOR
To enable the dumbbell to be ‘rung’, a sensor is required and a means of interfacing it to a computer. Details of a suitable optical sensor are given on David Bagley’s website "www.ringing.demon.co.uk". A light source in the sensor projects a beam towards the wheel and a reflector strip on the wheel reflects the beam as the mock bell passes bottom dead centre. A photo transistor in the sensor detects the reflected light and the brief output ‘pulse’ is passed via a suitable interface to the computer. The computer can be, for example, a standard WindowsPC running Abel, Beltoweror Ringing Master or a RISC OS computer (e.g. an Acorn RiscPC or A7000) running Stringing.
INTERFACE
For a WindowsPC:
The ‘gold standard’ is David Bagley’s single bell interface (SBI), described on his website. The SBI comprises both the sensor described above and, in a separate unit, the interface itself, which lengthens the signal to ensure it is not missed and delays it to the normal striking point.
However, an elegant, tried and tested, economical alternative is Alan Griffin's ‘Photohead with Interface’ (PWI). Specially designed to suit mini-dumbbells this comprises both sensor and interface in one small unit mounted on the dumbbell frame. With this system the interface lengthens the pulse, as with the Bagley SBI, but the signal delay is applied in software. Abel, Beltowerand Ringing Master all include the necessary instructions to apply this delay and the end result is indistinguishable from using a Bagley SBI. For DIY enthusiasts constructional details of the Griffin PWI, soon to be available on the Abel website www.abelsim.co.uk. are currently downloadable in two pages here:- Page 1 and Page 2.
Cheaper still is to use a simple reed switch and magnet.
Note that all three systems plug into a serial port at the PC. If using a PC not equipped with a COM port a serial to USB converter will be required (available from Maplin Electronics at about £20).
For an Acorn RiscPC or A7000:
A Bagley sensor (just the optical sensor, not the complete SBI) and a Griffin RISC OS interface are needed and also a Watford I/O card. Details of Alan Griffin’s RISC OS interface are given in the Stringing manual (see below). A Watford I/O card can be purchased from CJE Micro’s.
(There may be little to choose, in overall cost, between a PC running Abel, Beltower or Ringing Master and an Acorn RiscPC running Stringing. Personal preference or the ready availability of either a S/H PC or Acorn can tip the balance. Stringing arguably has more convenient method starting arrangements for dumbbell use. Abel, Beltower and Ringing Master offer many extra features not offered by Stringing.)
COSTS
A mini dumbbell built to the design described can be constructed using all new materials and good quality self-aligning ball bearings for about £80. Depending on the availability of suitable materials already to hand it may be possible to cut the cost considerably, though it is unwise to skimp on the bearings – with such a relatively light wheel good bearings are important to ensure free running and pleasant handling.
Ready built items are available as follows:-
Dumbbell and rope alone £130.
PC Option 1:
Dumbbell, rope and Griffin ‘Photohead With Interface’,
ready to plug into a PC serial port £150.
(Not included: PC, ringing software)
PC Option 2:
Dumbbell, rope and reed switch & magnet,
ready to plug into a PC serial port £140.
(Not included: PC, ringing software)
RISC OS Option:
Dumbbell, rope, Bagley sensor, Griffin RISC OS Interface,
Watford I/O card, Stringing and S/H RiscPC £225.
The above prices do not include carriage.
For further information, including delivery costs, enquire for details or telephone 07774 863184.