clapper bushes

[Chris Povey]

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The three main types in modern clappers are timber (genarally lignu vitae, =
I believe), nylon-type materials, and brass or bronzes. Timber ones aren't =
used now, so it's between the others. personally, I think the nylon-type on=
es are crap. They wear out far more quickly than metal bushes, and when fai=
rly new have a tendency to swell up in warm weather and bind on the pin, ca=
using the clapper to stick.

The most often used type of metal bush is that of oilite, which is an oil-i=
mpregnated phosphor bronze. Taylor's certainly use this (I've has some clap=
pers rebushed by them fairly recently), as do a number of other firms altho=
ugh I couldn't say specifically which ones without checking.

I'd advise that you recommend oilite.

David

Not quite so fast, David!

Yes, nylon has been used for clapper bushes and it can swell, causing clapp=
ers to stick. However, most bellhangers now use Tufnol, which doesn't swell=
and doesn't cause sticking. This seems to wear acceptably well in the grea=
t order of things. The big advantage of tufnol is that it is self lubricati=
ng and therefore is well-suited to being used in installations that get lit=
tle or no maintenance.

Lignum vitae is the traditional material for clapper bushes. It is the dens=
est of all timbers (it sinks in water) and has natural oils that allow a fa=
ir amount of self lubrication. It is now much rarer than it once was, but I=
understand that it is possible to get lignum vitae clapper bushes if you k=
now where to go. Another advantage of lignum vitae is that it absorbs shock=
s fairly well (as does tufnol).

Bronze, usually in phosphor bronze form because of its self-lubricating pro=
perties, is used for bearings commercially. It is used (but not exclusively=
so) for Oilite bushes. I think oilite is fairly new on the scene - but pos=
sibly as long as tufnol. I cannot think bronze in any form has the same sho=
ck absorption properties as lignum vitae or tufnol. Apparently, machining/r=
eaming oilite to size has to be done very carefully with a very sharp tool,=
otherwise the pores can be burred over and then no lubrication results.

I came across a very interesting bushing material a few years ago: white me=
tal. The shock absorbing properties and wearability of this material is exc=
ellent. It used to be used on big ends of petrol engines and therefore it h=
ad to withstand the shock loads from the pistons having big explosions abov=
e them every other revolution. I think the shell bearings now used in engin=
es still employ white metal. Someone had cast white metal into the eye of a=
1928 Taylor clapper. It had been reamed out to the size of the clapper pin=
. The other clappers (lignum vitae bushes) were being send off to be rebush=
ed. It was a shame to send the white metal one, because there was virtually=
no wear in it. However, it was. In retrospect, it would have been useful t=
o monitor its performance.

The biggest reason for clapper bushes wearing is lack of lubrication. Old-s=
tyle clapper pins had Stauffer lubricators for greasing the bushes. It is p=
robably quite rare to find a new clapper pin with a facility to grease. It =
is clearly very difficult to get grease properly into the bush if the pin h=
asn't a grease channel - and a lot of greaseway pins have been exchanged fo=
r solid stainless steel ones. I quote below an extract from a bellhanger's =
sales blurb:

We have found most so called 'self-lubricating' clapper bushes to have an u=
nacceptably short lifespan and many to have a tendency to seize up in warm =
weather. "Oilite" is a type of lubricant impregnated phospher bronze that w=
e have found to have at least a comparable lifespan to other 'self-lubricat=
ing' materials even when grease is never applied to the clapper joint. If g=
rease is applied to the clapper joint via a Stauffer lubricator a couple of=
times a year, we don't know how long an "Oilite" clapper bush will last be=
cause we haven't yet found any which have worn out when kept properly greas=
ed.

Note that they recommend lubricating oilite bushes with grease.=20

When I argued a point with Alan Hughes about lubricated bushes and greasewa=
y steel clapper pins always being better than self-lubricating bushes (tufn=
ol) acting on solid stainless steel pins, he said, "yes, I agree; but the v=
ast majority of my products are going to places where they will never get a=
ny maintenance. On that basis, this is the best arrangement". Difficult to =
argue against that one.

Another reason for wear is over reaming. If the bush has excess clearance, =
the shock loads will increase this very quickly.

What would I use? Lignum vitae if I could; but oilite does sound interestin=
g. Do not write-off tufnol, though. I've had fairly decent wear out of this=
material (but it was greased); and none of them swelled to cause binding.=
=20

Don't forget to lubricate regularly...=20

Chris Povey
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