Bob Loesch wrote:

> I'm gearing up to make a 165-scale tracker bar or two, and there
> is one rather important piece of information that I'm missing:
> What size are the holes, and what is the space between holes?

In answer to Bob's question on the 165 tracker spacing.  The same
tracker bar can also be used on the Wurlitzer APP piano and the Caliola.
As I have a Caliola with an original roll frame and had some of these
tracker bars pass through my hands, I can add some additional
information.

The spacing is actually metric and a machinist's trick.  The spacing
works out to be pi (millimeters) - 1/40 mm.  Most dividing heads used
to divide circles on a lathe use a 1:40 gear reduction.  This means
that with a metric lead screw on the lathe, turning the dividing head
one less turn each time produces this spacing.

As for the hole diameter, when I was working on a perforator for this
spacing I found that a #50 drill is the same size as the hole in the
paper.  This was found by passing wire drills though original green
paper Wurlitzer rolls.  According to my drill chart this is a diameter
of 0.0700 inches (1.778 mm).

The holes in most tracker bars are broached square.  This works out to
about 1.75 millimeters.  The holes on my tracker bar appear to be this
measurement.

As I have scanned over 50 Caliola and some Wurlitzer 150 roll fragments
and a few Wurlitzer 165 rolls, I find that the hole spacing is a bit
thin, especially on the chaining for long perforations.  This affects
the diagonal link between tracks more than the more direct horizontal
link.  Often the vertical links in a given track break out completely
(more so at the end of the roll) as the webbing changes in size due to
the take-up spool compensation.

The timing offsets on the drums are another matter.  If the instrument
to be sold had no drums then there is probably no offset.  The
APP/Caliola scale has drums on different channels than the Wurlitzer
165 so the offsets are in different places.  I have seen both round and
square holes used for the drum channels.  I believe that the tracker
bars with the round holes were made by Steve Lanick, who did more
research on this than anyone.  My Caliola has square holes on the drum
offsets.

Wurlitzer used a number of different designs over the years for the
drum beater mechanisms.  Which style drum beater used may also affect
the need for the offset.  As noted, the accuracy of many of the recut
rolls renders this offset to not be of much use.

Tracker bars get swapped all the time.  I am informed that the Wurlitzer
165 in Glen Echo Park currently has a Caliola tracker bar on it.

The tracker bar was made from thin sheet metal.  At an organ rally,
Robbie Rhodes pointed out an example to me that looked like it was made
on a kitchen table.  Probably these were made on a punch press: the
sheet metal would then be folded and soldered together.  After
soldering, the end mating to the wooden frame would be machined flush.

The 0.123-inch spacing is unfortunately some bad information that
persists.  Care must be used when laying out a tracker bar.  If one
measures each hole from a fixed point, then rounding occurs which may
lead to the 0.123 spacing.  I have in my possession a Wurlitzer 165
roll that was perforated to this spacing.  I was able to scan this roll
optically and convert the scale to play on the Caliola using Spencer
Chase's E-valve system.

Julie Porter

 [ pi - 1/40 = 3.1416 - 0.025 = 3.11659 mm = 0.1227004982 inch.
 [ Mike Kitner measured 0.1227 inch.  Either number will work.
 [ I can imagine Farny Wurlitzer telling his master machinist,
 [ "Make it so irrational that no one will figure it out!"
 [ -- Robbie