I avoid styrofoam insulation because: It is too rigid and therefore transmits shocks to the object. Once crushed, it provides no further protecrion.
-John ================= > 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. > > _______________________________________________ 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.
