Re: Alignments of the Newport Tower

On 1 Feb 2007 03:39:04 -0800, ghughesarch@xxxxxxx wrote:

On 31 Jan, 22:04, Eric Stevens <eric.stev...@xxxxxxxxx> wrote:

Bear in mind that the structure running on the track weighs several
tons and the track almost certainly was made of wood. It would have to
be much wider than an equivalent metal rail. The wheels would almost
certainly be made of wood also.

We have no evidence as to the material of the track or wheels. The ones
shown on the sectional drawing of Chesterton Windmill are not very wide.

http://www.warwickshire.gov.uk/Web/graphics/Graphics.nsf/graphics/che...
orhttp://tinyurl.com/2c73l3if you prefer shows the rails to consist
of two rectangular members lying flat on their longest side. The
lowest member is probably wood but the upper member may just have been
iron. The wheels are a mystery but they could be wood or wood shod
with an iron tread.

The construction of the Chesteron mill makes it a much higher class of
structure than the Newport Tower and if the rest of the NT mill
mechanism was of the same standard as the tower I would expect it to
be made of wood.


Eric Stevens- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -

I should mention that, in its current form, the track at Chesterton is
the result of alterations in c.1860, when some modifications were made
to the machinery.

It was -and still is - quite usual (despite the weight of the cap - at
Chesterton, IIRC it's about 5 tons) for there * not * to be wheels or
rollers, but for the cap to slide round on greased timber (and
latterly iron or iron-shod) blocks with a flat-face to flat-face
contact, or for the point of contact with the timber curb on top of
the tower to be the sheers - the two main longitudinal timbers forming
the base of the cap frame.

Hmmm - 5 tons sitting on a track of say 22' dia = 11' radius.
Coefficient of friction = say 0.2, therefore frictional resistance at
the track = 1 ton. Therefore torque required to rotate cap = 11
tons.ft. Even with a lever with a working radius of 30' (19' beyond
the track) it would take a force of at least 820 lbs to turn the cap.
No wonder they invented the fan tail!

There's no need for the timber curb to be exceptionally wide in
relation to an iron one - the smaller the contact area between the
fixed curb and the moving cap, the less resistance there is to be
overcome when turning the cap into the wind.

Oops - no. Within limits, the area of the bearing doesn't have any
effect on the frictional resistance.

At the more "typical"
English tower mills, the overall wall thickness at the top of the
tower is in the range 12" - 18", the timber curb might be around 12"
wide.

Gareth



Eric Stevens
.

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