Posted by Rick Denney on November 20, 2001 at 11:23:00:
In Reply to: Re: Re: Re: UPS Shipping/Insurance Follow-up posted by Erik on November 19, 2001 at 17:25:18:
There was a thread a week or two ago where someone suggested a foam insert. We talked about the structural aspect of this then.
You are basically correct. Force long the length of the tuba, meeting the rim of the bell, bends the bell rim easily. The applied force is resisted almost entirely in bending, where the brass is weakest. This is also the thinnest part of the brass. The bigger and flatter the bell, the worse the problem.
Applying longitudinal loads at the bell throat loads the brass much more in compression and much less in bending, where it is much stronger.
The factor that you might not have thought about is that the insert preloads the brass. So, to make a dent in the brass, you have to overcome not only the strength of the brass, but the preload as well. The brass can withstand much greater loads from the inside, where the resistance to force is entirely tensile (it's called hoop strength), instead of the much lower bending strength that resists dents.
The best case or box mounts the tuba body but allows the bell to flow in free air. That way, you'll only damage the bell if the force is sufficient to make the tuba move far enough so the bell runs out of free air. The soccer ball is highly effective in preventing that, because it fights back harder the more it is compressed.
But the ball should be the right size so that it fits into the throat deeply, but not so deeply that it can just slide in deeper when forced. When it's in that position, it should lift the bell away from the end of the case as far as possible within the constraints of the case. Charlie Krause recommends inflating the ball after inserting it into the bell throat, and I think that's a good idea.
Floating the tuba in foam is a good idea, but beyond the reach of most folks. Here's how I would do it.
Wrap the body of the tuba, up to but not including the bell flare, in two or three inches of bubble wrap. Cut a piece of plywood for the bell end of the box, and put foam between it and the inside of the box. The tuba side of the plywood need not be padded, because the ball will keep the tuba from ever touching it. Fill plastic bags (five-gallon garbage bags sounds about right) with polystyrene peanuts, and tape them to the outside of the bubble wrap enough to fill the box. Then put the ball into the bell and inflate so that the bell is reliably held away from the plywood. Float the protected tuba in loose peanuts to fill in all the nooks and crannies, but not so tight that they put any real force on the tuba. The tuba will be able to move around a bit in the box, but the attached bags of peanuts will cushion and damp this movement. The bubble wrap is stronger, to deal with larger forces. The ball protects the bell by keeping it in free air (filled loosely with peanuts).
I would think that the tuba could withstand anything that doesn't burst the box when packaged that way, and the cost of the packaging it still reasonably cheap and available.
Rick "thinking this will solve the problem with peanuts settling and not being where they are needed" Denney