A couple of people have suggested to me that the small brass bleed cups
that are sold by the Player Piano Co are not sufficiently uniform.  I
thought it might be interesting to take a random selection of bleeds,
measure the leakage and look at the uniformity.  The results of the test
are tabulated below.

Flow, cubic inches per minute:
•
      62           XXX
      63           XXX
      64           XXXXX
      65           XXXXXXX
      66           XX
•
Total bleeds measured: 20.  All bleeds were #68 hole size (.0310-inch
diam.) and were measured using 6 inches of water vacuum.  For
comparison, the flow through a #64 (.0360-inch) bleed cup (the next
larger available size) was 97 cubic inches per minute. I don't have
enough experience to know whether this is acceptably uniform or not.

There is a factor other than hole size which can have a substantial
effect on the flow through a bleed.  Quite simply, it is sharpness of
the orifice-hole entrance.  A sharp entrance will have a lower flow than
a beveled or rounded entrance.

For example, one of the bleeds from the above test was selected: it had
a flow rate of 64 cubic inches per minute.  The entrance face was sanded
flat so as to give a sharp entrance; the flow dropped to 61 cubic inches
per minute.  Using a small drill bit in my fingers the orifice entrance
was given a very slight bevel: the flow increased to 73 cubic inches per
minute.

I hope one or two restorers might find the above of interest.

Phil Dayson