Hi All, I just measured the shelving in my original Ampico roll cabinet
that had an American Piano Co. label in it before I had it refinished
in about 1967.  The span of the shelving is 16.5 inches, the depth is 8
inches and the thickness is 0.2 inches.  The shelves are mounted toward
the back of the cabinet so that the rolls extend beyond the shelving to
make it easy to extract them.  The wood is solid, not laminated.

All shelving is not of the same span, depth and thickness.  The
strength of shelving, it's ability not to bend down, is dependent on
many things, but without question one thing is its stiffness to
bending.  Plywood has much less resistance to bending than solid wood
and hard wood has better resistance than soft wood.

The resistance to bending is also inversely proportional to both span
and depth and directly proportional to the thickness to the third power
for the same material.  Using the Ampico shelving as a standard, if the
depth d, span s and thickness t are different than those of the Ampico
shelving they will be just as strong if they conform to the equation:

C=[(0.2in)x(0.2in)x(0.2in)]/[(16.5in)x(8in)]=[(t)x(t)x(t)]/[(l)x(d)]

where C = 0.00006060606 inch which is the thickness in inches
multiplied by itself three times divided by (the span in inches times
the depth in inches), as the equation above indicates.

So, for a given span and depth, the thickness can be calculated.
Anyone having a problem finding the correct thickness for a given span
and depth can contact me for assistance.

Allen Ford

P.S.: The bending strength of plywood can be greatly improved by having
it permanently cambered along a cord perpendicular to the span, but
this would not be something that I would suggest attempting as it would
require experimentation and insight.