In article ,
says...

The Hounsfield Tensometer works on a lever system that compresses a
leather bag containing mercury. As tension is increased, the mercury
is pushed up a glass tube, the length of the column indicating tension
on an adjacent scale. I would like to get rid of the mercury. Any
ideas on a method of conversion to alternate reading method please.

Leather bag? Mercury?? When was this thing manufactured?
Next you're gonna tell me it uses Plutonium Tri-Arsenide as
a muffler bearing lubricant.

Anywhere, I would suggest replacing the leather bag with
a stainless steel bellows, and replace the mercury manometer
with something like a pressure transducer. Does this item
measure force, or displacement, or a combination of both?

Jim

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please reply to:
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On 26 Jul 2003 13:20:13 -0700, (Glenn Cramond) wrote:
The Hounsfield Tensometer works on a lever system that compresses a
leather bag containing mercury. As tension is increased, the mercury
is pushed up a glass tube, the length of the column indicating tension
on an adjacent scale. I would like to get rid of the mercury. Any
ideas on a method of conversion to alternate reading method please.

If you replace the leather bag with a rubber bladder, and replace the
glass column with one much taller (30 inches of mercury is equal to
32 feet of water), you could then substitute colored water for the mercury.
That's physically unwieldy, but it is cheap and simple (at least it is simple
if you don't need so much accuracy that temperature compensation
becomes an issue).

Alternatively, you could replace the bag with a strain gauge load cell,
and the column with an electrical readout. That's a bit spendy, but it
would be neat and compact.

A more mechanical approach would be to use a spring and dial indicator
in place of the bladder and column.

Gary

"Gary Coffman" wrote in message
...
On 26 Jul 2003 13:20:13 -0700, (Glenn Cramond)
wrote:
The Hounsfield Tensometer works on a lever system that compresses a
leather bag containing mercury
^^^^^^^^^^^
If this is, indeeed, a pressure measuring system using column of mercury,
you might explore substituting the pressure gauge from a blood pressure
cuff. But, I suspect that is is kind of a "hybrid" (*******) system, in
which the volumetric displacement of liquid from the bag plays a part, so
the calibration in mm Hg will not be the same if you use a gauge. It might
be worth a try, though.

However, if this instrument is as antique as it sounds, it seems a shame to
mess it up.

On 26 Jul 2003 13:20:13 -0700, (Glenn Cramond)
wrote:

The Hounsfield Tensometer works on a lever system that compresses a
leather bag containing mercury. As tension is increased, the mercury
is pushed up a glass tube, the length of the column indicating tension
on an adjacent scale. I would like to get rid of the mercury. Any
ideas on a method of conversion to alternate reading method please.


Try this link: http://www.randhtesting.com/data1.htm

They mention a conversion in the opening paragraph that converts it to
a digital readout.



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--What the heck is this thing measuring anyway?

--
"Steamboat Ed" Haas : California: "The crap magnet
Hacking the Trailing Edge! : in America's crankcase".
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---Decks a-wash in a sea of words---

Jack Erbes wrote in message . ..
On Sun, 27 Jul 2003 16:19:50 GMT, steamer wrote:

--What the heck is this thing measuring anyway?

Thanks for the links they were useful.
The Hounsfield was issued to Australian High Schools and Technical
Colleges in great numbers in the days when governments were prepared
to spend money on education. Most schools still have one but keep it
well hidden (mercury). The most common use of the machine is to plot
stress strain curves of various samples of materials.
The test piece is placed under tension with a manual or motor driven
screw (both available), attached to one end of the test piece (uses
chineese finger trap type clamp). The amount of tension applied
causes the end anchoring the test piece to operate a lever that
compresses a leather bag and forces the mercury from the bag along a
horizontal capilliary tube. The tube runs axially beside a rotating
drum (rotated by the screw). By manually marking the length of the
column of mercury, one can plot a stress strain curve, examine
elasticity, determine UTS, yeild point etc.
Other attachments come with the machine to allow similar compression
and shear tests.

Most school budgets don't allow for upgrading or replacement so we
need to find a DIY method of converting these machines. In a school
of 650 kids I have a total budget of $7,500 PA (all tools materials
consumables etc.)

Really appreciate your efforts to help.
Glenn

We're using a $25 data acquisition board (hooked to $50, 1 psi pressure
transducers) to input flow bench data directly into an Excel spreadsheet.
If you could replace the mercury with some (any) other less hazardous
fluid and attach the pressure transducer where the "column" is supposed to
be... you could make a "virtual" column onscreen using Excel's graphing
capability. You can record, calibrate, graph and e-mail the data like any
other Excel worksheet.
Any old piece-of-junk pc will work... Windows95 or better.
The daq is he http://www.dataq.com/194.htm
The sensors are he
http://www.digikey.com/scripts/us/dk...?keywordsearch click
"technical/catalog info".
I honestly can't picture exactly what you have there, but if you just
need to record the pressure exerted by the leather bag, convert it to
engineering units, and display or record it.... you should be able to do it
for about $75 plus the old PC.
Just a thought,
David


"Glenn Cramond" wrote in message
om...
Jack Erbes wrote in message
. ..
On Sun, 27 Jul 2003 16:19:50 GMT, steamer wrote:

--What the heck is this thing measuring anyway?

Thanks for the links they were useful.
The Hounsfield was issued to Australian High Schools and Technical
Colleges in great numbers in the days when governments were prepared
to spend money on education. Most schools still have one but keep it
well hidden (mercury). The most common use of the machine is to plot
stress strain curves of various samples of materials.
The test piece is placed under tension with a manual or motor driven
screw (both available), attached to one end of the test piece (uses
chineese finger trap type clamp). The amount of tension applied
causes the end anchoring the test piece to operate a lever that
compresses a leather bag and forces the mercury from the bag along a
horizontal capilliary tube. The tube runs axially beside a rotating
drum (rotated by the screw). By manually marking the length of the
column of mercury, one can plot a stress strain curve, examine
elasticity, determine UTS, yeild point etc.
Other attachments come with the machine to allow similar compression
and shear tests.

Most school budgets don't allow for upgrading or replacement so we
need to find a DIY method of converting these machines. In a school
of 650 kids I have a total budget of $7,500 PA (all tools materials
consumables etc.)

Really appreciate your efforts to help.
Glenn

(Glenn Cramond) wrote in message . com...
Jack Erbes wrote in message . ..
On Sun, 27 Jul 2003 16:19:50 GMT, steamer wrote:

--What the heck is this thing measuring anyway?

Thanks for the links they were useful.
The Hounsfield was issued to Australian High Schools and Technical
Colleges in great numbers in the days when governments were prepared
to spend money on education. Most schools still have one but keep it
well hidden (mercury). The most common use of the machine is to plot
stress strain curves of various samples of materials.
The test piece is placed under tension with a manual or motor driven
screw (both available), attached to one end of the test piece (uses
chineese finger trap type clamp). The amount of tension applied
causes the end anchoring the test piece to operate a lever that
compresses a leather bag and forces the mercury from the bag along a
horizontal capilliary tube. The tube runs axially beside a rotating
drum (rotated by the screw). By manually marking the length of the
column of mercury, one can plot a stress strain curve, examine
elasticity, determine UTS, yeild point etc.
Other attachments come with the machine to allow similar compression
and shear tests.

Most school budgets don't allow for upgrading or replacement so we
need to find a DIY method of converting these machines. In a school
of 650 kids I have a total budget of $7,500 PA (all tools materials
consumables etc.)

Really appreciate your efforts to help.
Glenn


Sounds like somebody's overly clever method to replace a spring scale.
If it operates a lever, you could probably calibrate a suitable dial
indicator which should be within your budget or go to resistance-type
strain gauges which probably wouldn't be. The latter are what's used
in industry so would probably more useful to your student body.

Stan