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Geoffrey.walsh
06-18-1998, 05:22 AM
I am posting below my original message, the replies, then the
subsequent message I put out, and the replies to it.

What an erudite lot of people indeed !

I have taken out one facetious remark, left another in and done a bit of
other editing. I hope none of the comments have become attributable to
the wrong person by some flaw in my word-processing. If so please accept
my apologies.

Replies are still trickling in - if they add materially to the
discussion I intend to post these also in due course
************************************************** ********
One of the conspicuous landmarks of Edinburgh is the ornate tower
inPrinces Street erected to the memory of Sir Walter Scott , the
novelist-The 'Scott Monument'.

It is at present under repair and is swathed with scaffolding.

Some of its numerous stone carvings have decayed and are being replaced.
The masons use hammers the head of which are apparently made of stone.
They are in he form of a truncated cone (i.e. a wide cylinder with
gently sloping sides).

The handle is short and the hammer must be so heavy that many untrained
people would surely have difficulty in using or even of lifting it.

Why is this the traditional mason's tool ?

One would suppose that because of such high inertia it would be very
difficult to control. The hammer is only moved a short distance and only
low velocities are reached.

The same impulse could be obtained by the use of a smaller hammer swung
through a bigger distance. There must be some biomechanical trade off
between the large mass that has to be controlled and the accuracy of the
cut of the stone.

Would the precision of the cut in the stone vary with the speed of the
initial impact of the chisel which the hammer strikes ? The present
system has stood the test of time.
--------------------------------------------------
>From "Al Vangura Jr."

Have you thought about the number of strikes that the user must make
using the traditional hammer (heavy and slow) vs. a smaller hammer
(lighter and faster)? I think that the cuts need to be exact and the
number of blows to the stone quite low - like a diamond cutter. Once the
cut is made, there is no going back. I would be interested to hear what
responses you get Also, my father-in-law is a stone mason and I will
ask him what he thinks and contact you again. Good luck.

Al
University of Pittsburgh
Human Engineering Research Labs
------------------------------------------------
Dhendry@aol.com

The same impulse could be obtained by the use of a smaller hammer swung
through a bigger distance.

Can you apply the same reasoning to golf?
I used say that F=ma, and the only thing that the golfer controlled was
a. But then you could use a big massy club, swung more slowly and
achieve the same effect. This is clearly not true. Do you play golf?
Is the mason mall that you describe peculiar to Scotland? (Maybe the
masons in Glasgow use a more delicate instrument.)
-------------------------------------------------------
iallison@info.curtin.edu.au (Garry Allison)

I think it is about the motor control capacities in combination with the
development of linear momentum - otherwise I can see the stone mason
swinging a golf club although I did work for a stone mason once and he
did prefer to swing a golf club :-)

I think it is an optimisation of momentum (angular to linear / tangental
force of impact) and motor control/ performance.

I recently gave a lecture on the push - throw continuum where sequential
segmental kinetics (peak velocities) are either occur simultaneously
(i.e synchronised = a push) or in a sequence (proximal to distal = i.e a
throw). When accuracy and control are required the individual usually
combines some degreeof synchronised rotations of multiple joints
(shoulder / elbow) to at least have a rectilinear pathway at release (or
in this case impact) rather than a curvilinear pathway. The selection of
the strategy (push or throw) is also associated with factors such as the
level arm length, the size and mass of the projectile and the skill of
the individual.

I would hazard a suggestion that in a craftsman the heavy mass may be
optimal. Defining optimal may also be a factor - in cases where a
mistake is catastrophic you may find the optimal pattern may reflect
minimal error rather than maximal momentum.

Dr Garry T Allison Lecturer in Functional Rehabilitation,
School of Physiotherapy,
email:iallison@info.curtin.edu.au
Curtin University of Technology, Tel. +61 8 9266 3648
Selby Street, Shenton Park, Fax. +61 8 9266 3636
Western Australia 6008
http://www.curtin.edu.au/curtin/dept/physio/pt/staff/allison/
--------------------------------------------------------------------
rwhiteley@magnet.com.au

Organization: Mitchell & Whiteley Physiotherapy

Why is this the traditional mason's tool ?

Sorry that my explanation isn't such a definitive biomechanical one, but
one gleaned from a hobby of mine: carving. If your question is why use a
heavy hammer instead of a light one, I think you've answered it in the
next sentence.

One would suppose that because of such high inertia it would be very
difficult to control. The hammer is only moved a short distance and only
low velocities are reached.
Since the heavy hammer means large momentums are created with small
movements and small velocities (due to the large m), the hammer's easier
to control. If you use a lighter hammer and therefore higher velocities
to get the same momentum, it's more difficult to hit exactly where you
want, and then the chisel starts making the decision about the carving
rather than you. The same impulse could be obtained by the use of a
smaller hammer swung through a bigger distance. There must be some
biomechanical trade off between the large mass that has to be controlled
and the accuracy of the cut of the stone.
Again, I don't know that the trade-off is biomechanical in terms of an
enhanced muscular efficiency making the work easier, it's more that the
lower velocity movements are easier to control the accuracy of.

Would the precision of the cut in the stone vary with the speed of the
initial impact of the chisel which the hammer strikes ?
Not really, just at higher speeds, it's harder to hit the spot you want.
The present system has stood the test of time.
Apparently so.
Cheers,
Rod Whiteley.
----------------------------------------------------
Tim Pitt

Just a couple of thoughts. The high mass of the hammer would make it
more controllable, in the sense that small wobbles in the arm guiding it
would not affect its path very much. I'm no expert, but I think such
small movements do occur in muscle control.

I also expect that stone masons would generally be pretty tough lads.
There may also be a certain amount of job protection in maitaining a
high level of skill required to do a job.

Lastly, the size and shape of the hammers is also a compromisefor the
job to be done - does this hammer cope with several different types of
stone, or just granite ? Can it cope with large lumps, as well as the
level of detail required for monumental work ?

Anyway, why don't you ask one of the masons !

Tim
-------------------------------------------
From: Andrew_Pinder@hsl.gov.uk

Wood carvers use very similar shaped mallets, which are made of lignum
vitae which is a very dense wood. The short handle length is
presumably to prevent the weight of the mallet forcing the wrist into
ulnar deviation. The shape allows all parts of the head to be used for
striking. Are you sure about the material? Surely a stone hammer would
be liable to splinter or crack when used with a metal chisel.

Andrew.Pinder, MSc, Eur Erg
Ergonomics and Work Psychology Section
Health and Safety Laboratory, Broad Lane, Sheffield, S3 7HQ, UK
Tel +44 114 289 2594; Fax +44 114 289 2526
HSE home page: http://www.open.gov.uk/hse/hsehome.htm
-----------------------------------------------------
Blandine.Bril@ehess.fr (Blandine Bril)

I was very interested by you message and pleased to hear about some one
asking question about hammering. With some colleagues we have been
working for some times on hammering in a particular case of stone
knapping : the experiment took place in India, in Kambhat, were people
still make beads in stone, unsing a technique of "indirect percussion by
rebound".

I think we have some element of answer to your question :

Would the precision of the cut in the stone vary with the speed of the
initial impact of the chisel which the hammer strikes ?

We have shown, using an accelerometre stuck on the head of the hammer,
that expert stone knappers are able to "control" or to tune acceleration
of the hammer, depending on the task (length of the flake to detach, or
the raw material to knap) much better than the less expert do. In
addition, using a harmonic analysis we may hypothesise that the expert
minimize energy, during a sequence of percussion.

We have published preliminary results and we are now writing a paper in
English on that experiment.

landine Bril

Apprentissage, Cognition et Contexte
Ecole des Hautes Etudes en Sciences Sociales
54 Bd Raspail - F-75006 Paris
Tel: 33 01 49 54 20 74
Fax : 33 01 45 44 93 11
---------------------------------------------------
Bryan Kirking

I suspect that at least one reason for the hammer design is that larger
diameter hammers moving slowly are more likely to hit the chisel, rather
than the worker's hand. But that's just my guess.

Bryan Kirking
Research Engineer
Department of Orthopedic Surgery
Baylor College of Medicine
Houston, Texas
--------------------------
kburton@cix.co.uk

Interesting question. My guess would be that small amplitude aids
accuracy of cut (and reduces risk of hitting hand instead of chisel !.
Do you have any idea of prevalence of upper limb symptoms in
thisoccupation?

Dr Kim Burton
Editor, Clinical Biomechanics,
30 Queen Street, Huddersfield HD1 2SP, UK
Voice: +44 1484 535200
---------------------------------
Dhendry@aol.com

In a message dated 6/12/98 10:17:45 AM, you wrote:

I am aware of course of the rivalkry between Edinburgh and Glasgow,
Oxford and Cambridge, Harvard and Yale but have never heard of a
difference in mason's tools !
-->>
That was a point of the question.

I would hope that you would get replies from masons (or mason-savvy
people)
all over the world. These replies might throw light on the matter of
uniformity of masons' cutting methods. I would think, for example, that
the
favored tools would depend on the nature of the locally abundant or
cheap
material.
I still don't know whether you play golf. If you did, I would assume
that you
had practical experience with the control of impulsive forces and forces
that
are impulsive in a gross representation and not impulsive at all on a
finer
analysis.
I guess you don't play golf.

Jack
-------------------------------
Geoffrey.Walsh@ed.ac.uk

Mark Twain is quoted as saying -

Golf is Good Walk Spoilt
-------------------------------
gpp3@rabbit.INS.CWRU.Edu (Wes and Gail Perusek)

To look better into the history of hammers, you might get a copy of
George
Basala's The Evolution of Technology. Basala is at the University of
Delaware. Another tool analysis is done by Dr. Robert Weber in his
Forks, Phonographs and Hot Air Balloons
Both are excellent texts.
Dr. Wes Perusek
------------------------------------------
SAM EVANS

The builder's club hammer is similar in principle, with a heavy head
and a short handle. I think the head usually weighs 2 1/2 pounds,
and the handle is about ten inches long. This is the traditional
tool for hitting cold chisels when cutting bricks, masonry, plaster
etc and in my experience is much easier to use than a lighter hammer.
The reason may be that it is difficult to strike the chisel
accurately with a longer swing, and there is a danger of injuring the
hand. Thinking about it, the lighter hammers used for nails and the
carpenter's mallet are normally swung a shorter distance still,
particularly where great accuracy is required. You suggested that a
lighter hammer swung further might be easier, and this is exactly what
blacksmiths do, using a sledge hammer with a handle perhaps three feet
long. However, when striking a chisel like this, an assistant always
holds the chisel using a handle, because of the danger of hitting the
hand. Perhaps for the stonemasons, who want to hold the chisel in one
hand and hit it accurately with the other, a short swing and a heavy
hammer is the best solution.

Best wishes,

Sam.
Dr. Sam Evans,
Medical Systems Engineering Research Unit,
UWC School of Engineering,
PO Box 688, The Parade,
Cardiff CF2 3TE, UK.
Tel. (01222) 874533 or (01222) 874000 x5926
Fax. (01222) 874533
-----------------------------------------
"Doug McClymont" >
>the experiment took place in India, in Kambhat, were people still make beads in stone, using a technique of "indirect percussion by rebound".
>----------------------------------
>One more thought. I spent a year in India long ago working at one of themedical colleges. I saw at least one craftman working precious or semi-precious stones by hiting them with, as I remember a small hammer against a spike of metal. I took a few seconds of cine film and must have another look at it - it is now transfered to video. It was I think at a small place called Cambrai on the Gujarat coast,
>but I would need to check that.

Yes it is exactly there. In "colonial" terms the town is named Cambay.
It
is exactly as you say. I shall send you the papers we have published. We
are now finishing a big chapter for a book in archeology (in French),
and I
am working on an english version of the experimental part of our study,
that I would like to submit to the J. of Experimental Psychology.

Blandine Bril

Apprentissage, Cognition et Contexte
Ecole des Hautes Etudes en Sciences Sociales
54 Bd Raspail - F-75006 Paris
Tel: 33 01 49 54 20 74
Fax : 33 01 45 44 93 11
------------------

Just a couple thoughts, though I know nothing of
stone masonry or quarrying - I work with birds.

I think it is a matter of precision, and not a need
for force.

Moving a light hammer through a greater excursion will make it more
difficult to hit a chisel with precision every time. A heavy hammer
need not be moved as much between strikes, making the hit on the head of
the chisel more reliable, and thus making small, precise cuts during
stone carving possible
Logically then, if the aim is to make large rough cuts, the heavy,
short-handled hammer is not necessary. What is the normal hammer shape
for
quarrying large blocks?

Kay D. Earls
Dept. Ecol. & Evol. Bio.
Box G-W
Brown University
Providence, RI 02912

Ph: 401-863-2619 (office, voice mail)
401-863-3549 (lab, voice mail)
401-863-3804 (lab, no messages)
Fax: 401-863-7544

Kathleen_Earls@brown.edu
=======================
"Al Vangura Jr."

I still believe that the large mass should be looked at from the angle
of
motor control and the ability to control the mass. I spoke with my
father-in-law (the stone mason) and he believes that like a blacksmith,
the
effort is used to lift the hammer and gravity/inertia is used to move
the
hammer. A smaller amount of energy is needed to guide the hammer with
gravity/inertia than to go through the repetitive motions with a lighter
hammer. Also, the hammer will have much less bounce or return after the
impact. This along with higher quantities of impacts will fatigue the
user. His first reaction is that if they use the tool, it is definitely
the best tool. On the contrary, you could get used to or good at using
any
tool if you practice enough.

Al Vangura Jr
Alvst11@pitt.edu
University of Pittsburgh
Human Engineering Research Labs
----------------------------------
Edsko Hekman
>
> Will there be a difference when it is struck with a light high velocity
>missile (hammer head) or a large slowly moving one ?

Interesting question. If impulse has anything to do with it, as I think
it
does, the mass of a hammer would make a difference. Given a certain
amount
of kinetic energy (m*v^2) the impulse of a heavier object (m*v) will be
higher than that of a lighter object. Similarly, to obtain a certain
impulse, the kinetic energy and therefore the energy the carver has to
'invest' during the swing will be lower for a heavier hammer. Any takers
from here?
-------------------------
************************************************** ********
Email -

Geoffrey.Walsh@ed.ac.uk

http://www.ed.ac.uk/~gwalsh

Phone (0)131.664.3046

64, Liberton Drive,
Edinburgh
EH16 6NW
U.K.

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