Subject: Re: How to stop a falling weight with NO bounce

From: [email-masked] (James T. Bober)
Date: Tue, 23 Jul 1996 08:04:24 -0500

In article <[email-masked]>,
[email-masked] (Steve Gray) wrote:

>...
>    After many unsuccessful experiments, I went down to the beach (only a
> mile from here) and got a bucket of beach sand. The weight drops into the
> bucket of DRY sand with absolutely no bounce or loud noise or strain on
> anything. When I pull the weight up, the sand fills the depression so that
> the next drop will act exactly the same.
>    Beach sand here has fine, round particles, which form a rather shallow
> angle of repose. Sand for concrete, which I also tried, is sharp and
> angular, and does not flow back into its pre-drop configuration.
>...

For some experiments I did years ago, which required reproducably stopping an
accelerating mass without rebound under various conditions, I found that
zirconium oxide was the best substance available for my application. It was
finer and flowed and packed better than any sand I could find.

Jim

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From: [email-masked] (G Merryweather)
Date: Mon, 22 Jul 1996 23:26:52 GMT

How about sorbothane? It is supposed to be very good at absorbing
energy
Geoff

On Sat, 20 Jul 1996 17:04:46 -0700, [email-masked] (Steve Gray)
wrote:

>   I was making a machine to stretch ABS plastic by heating it until a
>weight supported by the plastic dropped. There was a problem: the weight
>would bounce back some, allowing the plastic to retract, which would
>deform it.
>   This is a nice solution,m which I am still using. Maybe some of you
>have a suitable problem! :)

Avant-Garde Engineering
Woodturning, general engineering and fabrication.
General Blacksmithing and wrought ironwork
Ph/ Fax 64-9-2669936

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From: [email-masked] (Jim Janecek)
Date: 23 Jul 1996 20:26:48 GMT

I know- it costs more- but in my work, I use a set of ACE brand adjustable
hydraulic shock absorbers.

The demo at the Design Engineering Show has 2 bowling balls that are
picked up by a suction cup.
One is dropped about 6 feet onto a large spring.  It bounces around for a
few seconds until it settles.

The second ball is dropped onto an ACE shock that has been adjusted to
absorb all the kinetic energy of the ball.

It drops and is linearally decelerated over a length of 3-4 inches to a
dead stop.  It looks great. The deceleration happens in a split second.

they are used in manufacturing to decelerate loads with no recoil

-- 
Jim Janecek

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From: [email-masked] (Greg Lewis)
Date: 24 Jul 1996 12:53:01 -0700

In article <[email-masked]>,
>finer and flowed and packed better than any sand I could find.

I've found that my foot works best. My size 14 Red Wing boots stick
way out in front of my body, and their nice soft toe caps transfer the
impact to my toes inside. I've tested Newton's theories with various
pieces of steel bar, heavy machine tooling and miscellaneous auto
parts and can verify that they all reached the ground without damage.
The energy was all absorbed by my toes, so of course, there was no
rebound.  Part of the technique is learning to realize that an object
is in downward motion, and quickly putting your weight on one foot
while moving the other so it is underneath the object being studied.

;-)
___________________________________________________________________
[email-masked]      	   	     They don't
Photojournalism sequence      	   	     Call this place
Department of Mass Communication   	     An institution
     and Journalism 	      	   	     For nothing
CSU Fresno, Fresno, CA 93740-0010

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From: "John R. Johnson" <[email-masked]>
Date: Thu, 25 Jul 1996 09:29:27 -0500

On 24 Jul 1996, Greg Lewis wrote:
<snip>
> while moving the other so it is underneath the object being studied.

Greg,
  I found that the technique is really quite automatic.  I seem to have
this natural reflex that very effectively catches any dropped object.
It works especially well with large castings and other heavy objects.
It seems like the heavier the object, the more effective my innate
reflexes are at cushioning its descent with my Red Wings!

John

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From: PPIERCE <[email-masked]>
Date: Thu, 25 Jul 1996 07:15:06 -0700

Greg Lewis wrote:
> ........
> way out in front of my body, ............
> ......The energy was all absorbed by my toes, so of course, there was no

When I worked for Caterpillar, guys in the shop usually wore steel toed
boot/shoes.  Even office people could get wingtips with steel toes.
Cat really pushed for metatarsal saftety shoes, but did not require
their use.  Dropping a 10" chuck on your tootsies could really be quite
convincing (lock door after horse is stolen)...  :-)

Paul in AJ AZ

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From: Mike Rehmus <[email-masked]>
Date: 29 Jul 1996 03:44:35 GMT

Hmmmm.

I always thought I should use my hands.

I've saved a lot of hot pieces of metal that way...
soldering irons, just welded metal, etc.

Next time I'll use my feet!  Guess I'd have to 
get rid of the steel toes in the Red Wings,
though.

Best regards,

Mike Rehmus

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From: Clarence Noyer <[email-masked]>
Date: 30 Jul 1996 22:21:19 GMT

The normaltendency to avoid an objec falling towards your foot is to 
pullyour foot away.  This puts your toes on the ground, floor or 
whatever.  If your reflexes are poor, you are set up for a dented shoe, a 
black toenail or even a crushed number of toes.

The conditioned refles is to lift your toe off the floor and ease the 
load down to the floor after it has hit your foot.  Of course, practicle 
limits of this process are dependent on your physical prowess and the 
mass of the falling object and it's velocity.  By using your head (not to 
intercept the object, fool :-)) choose small objects to stop or consider 
a safer working stance.

"CC"

act from knowledge not react from ignorance.

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From: [email-masked] (Greg Lewis)
Date: 27 Jul 1996 14:10:47 -0700

In article <Pine.SOL.3.91.960725092715.2661K-100000@reliant>,

>reflexes are at cushioning its descent with my Red Wings!

This is a genetic problem. We have some researchers here at the
university isolating that gene so the trait can be bred out of my
descendents. They may also soon have a cure available in tablet form.
Sufferers will take one tablet and stuff the remainder in the boots.

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From: [email-masked] (Steve Gray)
Date: Thu, 01 Aug 1996 16:31:14 -0700

> >> while moving the other so it is underneath the object being studied.
   You guys are overlooking one thing about catching a dropping weight with
your toes. My method is good for an indefinite number of repeats with no
degradation in the weight catcher, but feet or toes might turn to hamburger
after say 1000 drops. Also replacing beach sand is cheaper than going to the
hospital. Of course the beach is a mile from here but my feet are only about
6' away.

-- 
Steve Gray
Gray Associates
Santa Monica CA
Algorithms, computer graphics
Mechanical inventions