Posted by Jim Andrada on September 19, 2003 at 17:07:11:
In Reply to: Re: Re: oversize flight cases posted by In need of disabuse on September 19, 2003 at 14:11:53:
Well, I'm not Rick, but I've also pontificated several times as to how a free floating bell is the right answer.
I think most people don't have a good feeling for how much impact stress can be transmitted through foam material if the corners of the case should be impacted hard enough to deform the case. I've seen results of drop tests that caused some significant damage to a fairly sturdy assembly (stronget than a tuba bell).
In this case the fix was to allow air space between the FOAM liner and the corners of the case so the energy from the impact was dissipated by the deformation of the case itself. SOrt of like a modern auto hood etc. Think "crumple zones"
I think in most cases the scenario of interest is the one in which the case is dropped onto a serface such as the floor, as opposed to a point impact to the case (being pronged by the forks of a forklift for example when the driver has the forks too high while starting to pick the load.)
More or less "point" impacts occur when the case is dropped corner down as opposed to a "flat" drop.
I think my ideal design would have a foam liner relieved at all corners and ALSO with free space around the bell, and the body of the horn restrained enough that the motion of the bell under anticipated impact forces would not hit the case.
Another important point is the term "anticipated forces" as any design has a limit which if exceeded will cause damage.
Typically you want to protect against a free fall of maybe as much as a meter, but you don't want to spend the money to protect against a free fall of 120 feet or so.
It IS possible to make a package that will keep an egg unbroken in a fall from the Empire State Building, but most people wouldn't pay for the 12 foot square 1800 pound $100,000 case that would be required (all numbers are ESTIMATES only!)
Similarly you could have a case that would protect your horn in the even it were run over by a dump truck, it just wouldn't be economically feasible to do so.