| Topic: |
Science > Physics |
| User: |
"sunsite" |
| Date: |
22 Feb 2006 05:18:54 PM |
| Object: |
Life inside the case of a fragile guitar..... |
If this is the wrong group, then please forgive me and, even better, send me
to a more suitable one.
I wonder how cases for fragile musical (wooden) instruments are made and
what are the thoughts and physics behind (if any).
Some are hard with some soft material inside. Some are totally soft with no
hard material and a thick layer of soft protection.
I just wondered:
1. Does is make sense at all to make a instrument case which is hard on the
outside ? Does is just not transfer the force of an eventual blow more
directly to the inside ? Or does the hard material in fact absorb some of
the blow ?
2. Let's say a fragile instrument (in it's case) falls from 1 meter (3 feet
approx) to the ground (God forbid it !! :-)). Will the hard case protect
the inside well eventhough there is a terrible sound ? If it is a soft case
with a lot of buffer, will the fragile instrument have an similar blow,
since the damage maybe depends of things in speed being stopped ?
Any general practical commentaries about the best protection of fragile
objects ?
Generally I would expect the thicker the buffer, the safer the object.
Thanks a lot..
Peter.
Travelling musician.
.
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| User: "CWatters" |
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| Title: Re: Life inside the case of a fragile guitar..... |
23 Feb 2006 07:55:17 AM |
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"sunsite" <ingenspamtilmigtakpstrom@tiscali.dk> wrote in message
news:43fcf15c$0$15790$14726298@news.sunsite.dk...
If this is the wrong group, then please forgive me and, even better, send
me
to a more suitable one.
I wonder how cases for fragile musical (wooden) instruments are made and
what are the thoughts and physics behind (if any).
Some are hard with some soft material inside. Some are totally soft with
no
hard material and a thick layer of soft protection.
The trick when designing packaging is to know what its going to be subjected
to and the properties of the object being packed.
A soft case is cheap and will protect the contents from scratches but not
direct loads - when other objects are stacked on top it the packaging
deforms and transfers the load to the contents. That might be acceptable if
the contents is a flat pack kitchen but unacceptable if it's an egg.
A hard case is more expensive but in theory it prevents a direct load being
transferred to the contents. I say in theory because not all hard instrument
cases are good enough to do that. If you are shipping goods using a freight
carrier you would be wise to special packaging rated for the purpose.
Packaging must also be designed to handle dynamic loads (shock and
vibration). Typically you might use a rigid shell to protect against static
loads and soft padding inside to absorb shock and vibration.
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| User: "CWatters" |
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| Title: Re: Life inside the case of a fragile guitar..... |
23 Feb 2006 08:01:17 AM |
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I forgot to add that...
Packaging design is a compromise. You might be able to design a box that
protects the contents from the shock of a 1m fall onto concrete but how big
and expensive would it have to be?
If you know how many g the item can withstand without damage then it's
possible to calculate the order of magnitude for the thickness of the
padding required. You know the impact velocity (from the height dropped) and
you could assume that the stopping distance is say half the thickness of the
padding. The rest is simple maths.
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| User: "Dr Physics" |
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| Title: Re: Life inside the case of a fragile guitar..... |
22 Feb 2006 11:10:13 PM |
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"sunsite" <ingenspamtilmigtakpstrom@tiscali.dk> wrote in message
news:43fcf15c$0$15790$14726298@news.sunsite.dk...
If this is the wrong group, then please forgive me and, even better, send
me to a more suitable one.
I wonder how cases for fragile musical (wooden) instruments are made and
what are the thoughts and physics behind (if any).
Some are hard with some soft material inside. Some are totally soft with
no hard material and a thick layer of soft protection.
I just wondered:
1. Does is make sense at all to make a instrument case which is hard on
the outside ? Does is just not transfer the force of an eventual blow more
directly to the inside ? Or does the hard material in fact absorb some of
the blow ?
2. Let's say a fragile instrument (in it's case) falls from 1 meter (3
feet approx) to the ground (God forbid it !! :-)). Will the hard case
protect the inside well eventhough there is a terrible sound ? If it is a
soft case with a lot of buffer, will the fragile instrument have an
similar blow, since the damage maybe depends of things in speed being
stopped ?
Any general practical commentaries about the best protection of fragile
objects ?
Generally I would expect the thicker the buffer, the safer the object.
Thanks a lot..
Peter.
Travelling musician.
Should be layered, hard on the outside to absorbe/deflect shock when
dropped, and inside the case enough padding to keep the instrument in one
location when dropped.
Soft cases (the bag kind usally do not survive the drop test)
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| User: "Tony" |
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| Title: Re: Life inside the case of a fragile guitar..... |
23 Feb 2006 08:07:37 AM |
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It may not be right on point, but this is a useful thing to remember.
If something falls 10 inches and stops in 1 inch, it will undergo an
average of 10 g's while stopping. If it stops in .1 inches, it's 100
g's: jus the ratio of the two distances.
There are lots of assumptions, like no air resistance or terminal
velocity limitations, or twisting on impact, but it's a rough
estimation of the kinds of shocks things endure. That's way wooden
floor impacts are less likely to break a dish than a ceramic floor
does, unless I drop the dish. Then it breaks, even if on a rug. On the
other hand, if my wife drops it. . .
There's a similar inconsistancy in speeding tickets, for that matter,
as to who gets warnings and who gets points, but that's a discussion
for another news group.
.
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| User: "sunsite" |
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| Title: Re: Life inside the case of a fragile guitar..... |
27 Apr 2006 12:36:53 PM |
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Dear friends;
Thank you for the replies. It was excactly what I was looking for: The
physists explanation, - not the everyday assumptions of some music
department salesman, or some nerd-like musician like myself.
The egg-story is interesting, though the succés-criteria of the egg is quite
simple to tell: Even it breaks or it doesn't..
Another story is maybe the state of a $ 15.000 guitar when dropped once,
twice or 10 times from 1 or 2 meters by airline staff. It may not brake, but
could get unvisible, but hearable damages. Wood is alive. The instruments
improves over the years when played regularly. In the same way could it lose
quality when dropped.
I presently have a "Liteflite" hard case made by Hiscox in England. The
guitar is fixed inside the case. The plasticlike material on the outside is
probably 5 milimeters thick and the layer inside about 1cm. I think there
must also be a 1-2 cm layer of flamingo between the plastic outside and the
teddy layer inside.
I wonder what would happen to the guitar if it was dropped from 1-2 meters
protected by this case. Some professional guitarists refuse to hand over the
instruments to the airlines, but insist on carrying it with them in the
cabin. This is much harder nowadays after 9.11.2001, and more so with the
new wealth of discount airlines who must be stricter about everything in
order to cut prices.
Others, who travel very much with the guitar have enormous flight cases
which seem to combine stiffness with very thick inside blow absorber. I
think they must be very heavy though.
The great Spanish guitarist Andrés Segovia always bought 2 seats, one for
himself and another for the guitar. But I think he could afford it.
Peter
"Tony" <ajw27703@yahoo.com> skrev i en meddelelse
news:1140703657.812749.185720@i40g2000cwc.googlegroups.com...
It may not be right on point, but this is a useful thing to remember.
If something falls 10 inches and stops in 1 inch, it will undergo an
average of 10 g's while stopping. If it stops in .1 inches, it's 100
g's: jus the ratio of the two distances.
There are lots of assumptions, like no air resistance or terminal
velocity limitations, or twisting on impact, but it's a rough
estimation of the kinds of shocks things endure. That's way wooden
floor impacts are less likely to break a dish than a ceramic floor
does, unless I drop the dish. Then it breaks, even if on a rug. On the
other hand, if my wife drops it. . .
There's a similar inconsistancy in speeding tickets, for that matter,
as to who gets warnings and who gets points, but that's a discussion
for another news group.
.
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| User: "Andy Resnick" |
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| Title: Re: Life inside the case of a fragile guitar..... |
23 Feb 2006 07:58:01 AM |
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sunsite wrote:
If this is the wrong group, then please forgive me and, even better, send me
to a more suitable one.
I wonder how cases for fragile musical (wooden) instruments are made and
what are the thoughts and physics behind (if any).
Some are hard with some soft material inside. Some are totally soft with no
hard material and a thick layer of soft protection.
I just wondered:
1. Does is make sense at all to make a instrument case which is hard on the
outside ? Does is just not transfer the force of an eventual blow more
directly to the inside ? Or does the hard material in fact absorb some of
the blow ?
2. Let's say a fragile instrument (in it's case) falls from 1 meter (3 feet
approx) to the ground (God forbid it !! :-)). Will the hard case protect
the inside well eventhough there is a terrible sound ? If it is a soft case
with a lot of buffer, will the fragile instrument have an similar blow,
since the damage maybe depends of things in speed being stopped ?
Any general practical commentaries about the best protection of fragile
objects ?
Generally I would expect the thicker the buffer, the safer the object.
Peter,
The goal of any crash-protection device is to dissipate energy, usually
by increasing the surface area of contact and increasing the duration of
impact- these priciples can be seen in most protective devices, from
athletic padding to automotive (and roadway) safety devices. A lot of
physics and engineering departments have "egg-drop" contests; the goal
is to drop an egg as far as possible, without it breaking upon impact.
As for your specific questions, I suspect hard cases are superior to
soft cases in terms of (1) being able to withstand extremely high,
extremely localized, imapact forces (like say, a sledgehammer) and (2)
better able to be packed away in storage (while containing the object).
The downside is that hardcases are more expensive.
One common misconception is that the impact force is somehow decreased.
This is not true! What changes is the time- and space-profile of how
the force is felt by the object. In a previous life, part of my job was
the packaging of equipment to survive getting into space, we had a
gigantic shaker table that could simulate lift-off forces (shaking only,
not static accelerations). We learned all about this stuff.
--
Andrew Resnick, Ph.D.
Department of Physiology and Biophysics
Case Western Reserve University
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