The Tower Handbook
An odd struck bell doesn't strike when it ought to. But when ought it to strike? Many people would accept that a bell is odd struck if it strikes earlier or later at either or both hand and back stroke, when judged by an experienced ringer. That still leaves us wondering what an experienced ringer judges it by. The reality is that there are two effects people call odd struck.
Both these effects are off putting, but a bell that is odd struck in the absolute sense must be rung with a deliberate uneven rhythm, whereas you can successfully ring one that is the same on both strokes, merely by adjusting your perception of the delay between pull-off and strike.
Bells are not the only things that can be odd struck, so can ringers. Heavy handling can greatly distort the bell's in-built rhythm. Compare the effort some people put into ringing rounds with the effort needed to do a dodge and you will realise that short backstrokes, snatched handstrokes, etc can force a bell to ring a quick stroke. If you add compensating slowness at the other stroke to keep in place you have an odd struck ringer.
A perfectly hung bell, with its axis, its centre of gravity, the pivot of the head-stock and the pivot of the clapper all in line, and the bell and clapper perfectly symmetrical, will strike evenly. If any of these are out of line, the bell may be odd struck. Traditional hanging leaves plenty of scope for such misalignments. Modern fittings are less troublesome, but small misalignments are still possible. Some modern headstocks include clapper adjusters (twiddle pins) that can be used to move the clapper slightly, and so adjust the timing between the two strokes. See section 14.7c.
It is actually easier to agree when a bell is badly odd struck! There are two ways to look at it. What we might call a 'bell hanger's view' says that a bell swinging freely with no rope to disturb it should strike perfectly evenly. In contrast to this, in a 'ringer's view' a perfectly struck bell would need no extra effort at hand or back in normal ringing to strike perfect open leads . The two may amount to the same thing or they may not, depending on the length and weight of rope  and the speed at which the bells are normally rung.
If you ring as you have been trained, smoothly and evenly with balanced effort on each stroke, an odd struck bell will strike wide at one stroke and close at the other. If you do it with perfect regularity every blow will be wrong! To make the bell strike at the right times, you must ring it unevenly, ringing quicker on the stroke where the bell is slow and slower on the other where it is quick. Ringing deliberately unevenly is harder than ringing normally, especially in changes since it is another rhythmic variation you have to add onto the changes between slow and fast for hunting up and down, etc.
Ropesight is misleading when ringing odd struck bells. Even when you have mastered the odd struck nature, you will also need great will power to overcome the temptation to deflect from your intended rhythm when the ropes you are following make you appear to be in the 'wrong' place.
There is yet another twist when ringing an odd struck bell, if you lose concentration for a blow and hear your bell strike wide. Feeling rather guilty, you smartly correct it by ringing quicker on the next stroke, which of course is the worst thing to do because the bell rings close at that stroke anyway. You need to develop the knack of correcting striking faults after two blows rather than after one. This is perhaps the most irritating feature of ringing badly odd struck bells, and one of the hardest to master.
You may notice this when ringing at different speeds or when 'driving the bell harder' in unsteady striking. There could be an interaction between you and the bell. Sometimes bells are described as more or less 'forgiving'. If you ring them carefully they strike well, but if you relax they go astray, or rather you and they go astray together. A bell is odd struck because something about the way it and its clapper are hung is asymmetrical. With an old style hanging on timber headstocks, it is possible that several things are asymmetrical and they may partially cancel out. Whether they do so may be affected by the speed and the way you ring the bell, hence the perceived change in behaviour.
Yes. There are two possible reasons. The leather pad lifts the clapper slightly from the bell (if it is a bulky one or if the clapper ball normally rests in a pit in the sound bow). This may slightly affect the time when the clapper leaves that side of the bell and flies across to hit the other side. It would make the bell quicker at handstroke . The more probable explanation is that when the bells are half muffled the whole band rings with a slightly different rhythm. They may ring more slowly, and there may be less difference between handstroke and backstroke because this is easier and the half muffling provides the punctuation effect normally provided by the open lead. So if your odd struck bell tends to strike wide at backstroke, the effect will appear less since everyone else is ringing wider at backstroke.
The clapper strikes the wrong side of the bell each time. When a bell rings full-circle, the clapper strikes the bell on opposite sides at handstroke and backstroke. If the bell is up right, the clapper swings faster than the bell, across its mouth and catches up the other side to strike the 'leading edge' (the way the bell is going). If the bell is up wrong, the clapper swings more slowly than the bell which catches it up as it falls back to strike the 'trailing edge'.
The position of the clapper when the bell is stood affects the balance. If the bell is up right, it rests against the leading edge so it helps hold the bell against the stay. If it is up wrong, it rests against the trailing edge, and so its weight tends to pull the bell back over the balance.
There is the direct way and the indirect way.
The fact that people can ring a bell without noticing that it is up wrong suggests that it does not matter, but there are some differences. It may slightly alter the striking, making the bell a little more (or less) odd struck. It may also make the degree of apparent odd struckness more variable with how the bell is handled, in other words it may become less predictable. The fact that the clapper rests more lightly against the bell means that when the bell is vibrating strongly just after being struck, the clapper may bounce on and off against it. This can in some cases increase the risk of cracking . When you come to lower a bell that is up wrong, it will stop striking part way down, just after it makes the transition from double to single clappering, and may be difficult to get striking again. This may not matter when lowering singly, but sounds messy when lowering in peal.
The bell and the clapper are both pendulums. They naturally swing at different speeds, depending on their shape and length. This is what makes the bell strike. The bell moves the pivot of the clapper (because it is some way out from the bell's swing axis), as well as the clapper ball being pushed when it hits the bell.
A team  working at Cambridge in 1965 showed that the complex behaviour could be boiled down to two ratios of physical properties of the bell, the clapper and the separation of their pivots. Different combinations of these three variables give bells that will clapper right, wrong, both or neither. Most bells ever made fall fairly neatly into the 'both' category. Once up they stay clappering the same way, but which way that is depends on what happens while they are being raised.
With many bells you can, but not all. Raise a bell sharply from rest, pulling and checking it fairly hard so the bell strikes the clapper earlier and sets it swinging in the right direction. If you raise it slowly, the clapper will dither for a while, and may first strike the wrong side of the bell. Once it hits the bell fairly hard, it is likely to continue clappering the same way, as it is batted back and forth by the bell, a bit like a ping pong ball. Getting this good start is harder with a heavy bell because even quite strenuous effort cannot make the bell swing far enough to hit the clapper before the friction and movement of its pivot start it swinging.
With some bells you may be able to, but in many cases, the only way is to bring the bell most of the way down again, pull extra hard to get the clapper to flip over and then try to make it go up right. The heavier the bell, the lower you will have to bring it before you can pull it hard enough to flip the clapper over. With a very light bell you may be able to make the clapper flip over by pulling very hard (at hand or back) while it is up.
Some bells always go up wrong, whatever you do. If that happens, the only way to flip the clapper over is to do it by hand after the bell has been stood. Remember that going near bells when they are up is dangerous so take all the precautions listed in section 3.1w. (Read them again unless you are sure you know all the safety precautions.) Be sure you are properly supported before trying to move the clapper. Clappers can be much heavier than you think. Make sure you do not disturb the bell by moving the clapper. Lower the clapper gently onto the other side of the bell.
Big bells swing slightly more slowly than small ones. We make all the bells ring at the same speed by ringing the lighter bells higher so they spend longer near or over the balance. This compensates for their quicker swing. The clapper strikes about three quarters of the way through the swing, so a lighter bell gets to that point a little more quickly than a heavy bell.
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