Jim wrote:
As you can imagine, it turns out that foam can be too stiff or too soft, and that the appropriate foam density and thickness is dependent on both the mass of the thing being supported and the expected loading.
You also need to pay attantion to what parts of the item can bear how much loading, and from which directions -- knobs, connectors, and many handles can't bear much, for example -- and design the packaging to route loads around these features to other parts of the item that can bear them. That's what all the carefully folded cardboard and die-cut foam in engineered pakaging do.
Take home message: packaging is non trivial. A simple: "pack it in two boxes with X inches of crumpled paper or peanuts" isn't going to work.
There is no substitute for a basic understanding of the physics involved and the properties of available packing materials. The mistake I see most often is that the contents of a box are not immobilized by the packing. When the box is in motion and then stopped abruptly, the item has a running start to smash into the inside of the box and whatever stopped it. Sometimes there is enough packing material to fill the space in the box but it just isn't stiff enough (e.g., light open-cell foam), and sometimes there isn't enough packing material so there is air space inside the box. Frequently, both. The buffer material for a 50 to 100 pound item needs to be considerably stiffer than most people think.
That said, it's not rocket science. Large-bubble bubble wrap, wrapped TIGHTLY around the item in at least two directions until there is at least 4" on all sides of the item, is a very good start for anything up to about 100 pounds (6" on all sides is better by the time you get to 100 pounds). You may need to use sheets of styrofoam insulation, heavy cardboard, or plywood to make sure loads will not bear on fragile parts of the item. The bubble wrap must be taped up very tightly so the wrapped item feels like a monolith bursting at the seams, then put into a box rated for the weight of the item.
All internal space in the box must be filled with packing -- the bubble wrap, applied as described, will make a rounded shape, so peanuts or something else must be used to fill the gaps to the square corners of the box (I hate peanuts, so I generally use rolls of bubble wrap, pieces of styrofoam building insulation, etc.).
Finally, the entire contents should modestly overfill the box -- you should have to compress the packing to get the box shut. When you do, USE TAPE FREELY. Do not depend on tape-to-box adhesion -- wrap wide (at least 2"), strong tape all the way around the box (fiberglass filament tape is excellent), lapping the tape over itself the entire length of the longest side to form a tape band all the way around the box. Wrap tape all three ways around the box (all three axes). For smaller boxes, you can wrap once per axis, in the middle of the box. For larger boxes, you need to use two or even three of these loops per axis, spaced out along the box.
You can also build up most of the buffer with styrofoam building insulation, if you prefer. I still like to use an inch or two (all sides) of tightly-wrapped bubble wrap as the innermost layer.
All of this is not exactly free, and takes a bit of time -- I often use a whole roll of bubble wrap, sometimes more, and half a roll or more of tape, for a benchtop instrument or a boatanchor radio. Plus a good, sturdy box. But I have never once had an item damaged in shipping, since long before there was an eBay.
Best regards, Charles _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
