HP 13255 Technical Information page 39

13255
Cartridge Tape Module
13255-91032/37
Rev AUG-01-16
by two extension springs which also provide the correct capstan force.
The right hand ball and socket set prevents translation while the left
set has an elongated socket to prevent rotation about two axes without
causing binding due to tolerance accumulations.
As well as retaining the motor/tachometer assembly in its gimbal, the
two extension springs load the motor capstan against its mating belt
capstan within the cartridge. This spring loading takes up an accumu-
lation ot dimensional tolerances within both the cartridge and the
drive while holding the force between the capstans within specifIed
limits. The motor capstan is a polyurethane elastomer covered aluminum
part 0.338 inches in diameter. The elastomer used has the best combi-
nation at high coefficient
Of
friction, resistance to compression set
and resistance to wear of a selection ot potential materials which were
tested. The capstan is set-screwed to the motor shaft and its height
can be set without
~pecial
tools or fixtures. A variable reluctance
tachometer is mounted to the motor/tachometer assembly. This conSists
of a 48-tooth disc staked to the motor capstan, a piCkup coil and per-
manent magnetic flux gate assembly screwed to the motor mount. The
disc-to-pickup distance is set at 0.012 inches
+1-0.002
inches. Motor
capstans with disc attached can be field replaced without need for fur-
ther adjustment.
3.4 FUNCTIONAL OESCRIPTION - TAPE CARTRIDGE. Refer to the tape cartridge
diagram (figure 13), hole status format (figure 14), and valid record-
ing area (figure 15) located in the appendix.
The tape cartridge shown in figUre 13 provides 120,000 bytes of storage
in 256-byte record, single-track 0.\30
+1-0.005
inches, 800 BPI (1600
rRPI)
+1-60
BPI standard format. At 10 ips, this gives a typical burst
rate of 1000 bytes per second and 748 bytes per second average through-
put.. The cartridge consists of a metal base plate and plastiC cover.
The tape contains 140 feet (minimum) of O.150-inch 8138 computer tape
suitable for recording purposes. The tao labeled RECORD is used to en-
able recording on the cartridge. A cartridge door is used to protect
the tap@ during transport and storage. When the cartridge is inserted
into the CTU Transport Assembly, the door Is opened automatically. The
mirror is used witn the hole sense scheme. An infrared emitter located
in the CTU Transport Assembly base shines through the base plate onto
the mirror. Lignt is then reflected through the front of the cartridge
to a photo-sensor in the CTU Transport Head Bridge Assembly. The l1ght
is intercepted by the tape normally ind1cating no hole. If a hole is
present the light will be detected by the photo-sensor. The motor cap-
stan drives the belt capstan which then moves the cartridge tape via
the belt. The belt consists of an elastomeric belt whiCh drives the
tape by transmitting the belt capstan force to both tape reels. The
tapp. cleaner consists of a scraper which is displaced approximately
1.125 inches in front of the head.