Spare a thought for plain bearings - with so many re-hanging jobs during the last 100 years, and as a consequence, replacement with ball or roller race bearings, some basic engineering history is quietly slipping away from our belfries.
Plain bearings for swinging bells have been made from non-ferrous metals - mostly brass or bronze, ever since the idea of hanging bells for swinging began during the early medieval period (or even before). Over the years improvements have been made to the way they were mounted, provision for lubrication etc, and even some bell founding and hanging firms took out patents for their various designs. The truth is probably that a steady evolution took place towards the common 19th century style of bearing block, set in to a wooden frame or mounted on top of a metal one, which are most likely to be the examples that remain in a few of our towers to this day.
It was only on considering the position at Finchampstead, where I rang before moving to Worcestershire that I realised that we had the only ring of six (and at Twyford the only ring of eight) in east Berkshire still on plain bearings - and generally speaking they 'go' very well - after 90 odd years. (But the re-hanging which took place in 2004 changed those at Finchampstead).
It is not unreasonable to expect bearings on bell installations to last in the region of a hundred years or so. Certainly this was achieved with plain bearings - although some designs fell short of this, generally speaking such bearings were the subject of good established technology, readily understood by all involved, and of course replaceable when it eventually became necessary. So why change?
Ball races were first used for bell bearings towards the end of the 19th century - but only on an experimental basis. In fact it is now just over 100 years ago (it was in 1899) that James Shaw produced the first practical bearings of this sort, which were roller bearings in a machined block. James Carr also obtained a patent about this time, and eventually Warners tried the then young firm of Hoffmann as suppliers by 1913. It was not until 1914 however that the first complete ring of bells was fitted with a set of what we would call modern ball bearings. This was at Hensingham in Cumberland, fitted by Taylors. From the start the idea was that this was to be a 'bought in' part, not made by the bell-founder, although in fact several bellfounder and bellhanging firms had designed and applied for patents of their own version of this concept as they had done previously with various improvements to plain bearing design.
There are two principal reasons why roller bearings are preferred over plain ones -
The reason for examining the introduction of rolling bearings is to illustrate that for most of the 20th century - in fact through all of it - there was a steady replacement of plain bearings for rolling bearings as major re-hangings have taken place. The hundred-year life cycle of bearings suggests that there are now not very many left - and whilst a greater incidence of longevity of these bearings occur no doubt in rural areas, or in churches where there are no bands and little ringing activity over many years will have preserved them, nevertheless, the net result is that we are near the end of an era.
I would like to suggest that all replaced plain bearings should be preserved somehow - maybe in a museum, in the church, ringing chamber, library, church hall or wherever. Maybe just locked up in the belfry somewhere. One day, someone will want to see them, for genuine engineering or historical reasons. There is another possibility of course - have some of them melted down and cast into something - a bell, trophy, heraldic device, etc - with a suitable plaque to remind folk of it's origin.
The other reason that some plain bearings should be available for inspection is that the concept is still used for certain applications – for example Internal Combustion engines 'main' and 'big end' bearings, although usually with a soft metal facing; many small rotating machinery parts, and the 'non load' end of many electric motors have plain bearings (even if there is a ball race at the pulley end). Many plain bearings are of sintered metal or plastics; and many slide mechanisms in complex equipment use modern materials technology to provide precision plain bearing surfaces. So, like our pulleys, rope, castings and fabrication and assembly found in the belfry - there are many features of good engineering design practice that could be used for educational purposes, both informal within the Exercise and perhaps when a student chooses bells or ringing as a topic for study in a project of some sort. There have been many examples of successful projects within the belfry - from GCSE to post Graduate level - by non-ringers as well as ringers, and it is to be hoped that this can be responsibly encouraged. But these people will be more satisfied if there are a few 'spare parts', or examples of earlier technology to inspect, or their findings will not be as meaningful as they could be.
The sort of topics that could be investigated by looking at plain bearings forms the basis of the science of Tribology - which could include the following topics: friction between different materials; design size (load/area/strength etc); use of tapers or other shapes for location; provision for lubrication (and the nature of lubrication of journal bearings); examination of wear (including comparing each side); fitting and alignment requirements; comparison to other uses of half-cup bearings; similar materials or related applications; possible improvements or summary of existing technology and sources.
Plenty there to grasp and meditate on.
DWS - 7/2014
Document last modified 3-July-2014