Bell Frames

[Roderic Bickerton]

Old King post frames have a reputation for being difficult to stabilise.
They are a development of the earlier headless or short headed frame.
They consist of an upright on a heavy foundation with the bell on top of the
upright.
the upright is braced with two angled props.
the structure is a pair of right angle triangles back to back with the
upright common to both.
The swinging bell produces horizontal force.
Each prop in turn takes the load as the bell produces force toward the prop.
If the joints are loose the king post moves across until the looseness is
overcome and the prop can take the load.
The only way to stabilise this set up is to make sure both props are really
tight up against the king post.
This can be done by fitting steel tie bolts to pull down the props so that
they are pressing hard against the king post, and able to resist movement
without the king post having to move and take up the slack.
The concept is not changed if the king post frame has full heads and corner
posts.
The only additional benefit, (apart from being able to walk round easily) is
proper stabilisation of the width of the pits, Not very critical with 3 or 4
bells swinging the same way, but essential when the frame has bells swinging
at right angles to each other.

Looking at a full headed king post frame another way it is a box structure
and would not be able to withstand much horizontal force without some angled
bracing (referred to as angled props above).

The principle remains.
The angle braces must work if the frame is to be stable.
They only work if they are touching something.
This means they must be tight and under some load.

Look at this weeks Ringing World.
A lovely clear picture of Brasted frame (P1030).
What has been done to pull in the cross bracing (the king post props)?

Vertical top to bottom tie rods can only be of limited benefit, because they
only pull together the joints of the vertical king and corner posts, which
were never intended to take the horizontal force generated by the bells. If
excessively tight they can overload joints and damage the timber.

Frames also generally need pulling down onto there foundation beams and
steel underpinning where fitted, if that lot is not to roll around like a
pile of logs, but that is another issue.

Its near November 5 so let us see if there are any fiery replies!

Rod Bickerton
Watford