Theatre Design & Technology - Dec 1972 - 31

NOTES ON THE WORKING DRAWINGS
As might be expected there was a considerable temptation to second guess myself on various aspects of this
device and offer an "improved" design. In the present
article comparison of the photographs with the working
drawings will demonstrate that this is not a temptation
which was entirely overcome!
Most of the revisions concern the low speed drive belt
and its associated pulleys. I simply could not bring myself
to advocate the flagrantly sloppy spring-loaded caster belt
tightener used on the original. Nonetheless, one must
acknowledge that the latter actually works whereas the
revisions suggested here are at this writing paper-improvements only.
The most difficult of these revisions to facilitate is the
inclusion of adjustable bearings on the high speed countershaft to provide belt tightening. A feasible solution to this
is proposed in the working drawings. As shown an oversize
oblong hole must be cut in the top and bottom plates of
the main frame-an arduous task in the non-machine shop
even if both ends of the hole are drilled out with a 7/8"
drill first. The slots in the bearing blocks themselves are
easier since they can be sawed out from each end with a
hacksaw. A self aligning flange bearing, such as Browning
FB 110-3/4, would be the most desirable in this application but would still have to be mounted on some type of
adjustable base to allow adjusting belt tension.
Other revisions in the drive are the use of two belts and
corresponding double sheaves. As mentioned in the parts
list, these may be rather costly and doubling up on die
cast si ngle groove sheaves may be preferable to some
builders. Notice that the low speed countershaft may have
to be lengthened if the latter procedure is choosen. One
other minor revision appears, namely a slight increase in
the depth of the curved portion of forming rollers. The
dimensions mean that 1" thin wall tubing fits it rather
more closely than on the prototype. Thus some cut and
try overcutting may be necessary if binding occurs.
Other aspects of the device are not presented in detail
because of the wide variabil ity in installation possibil ities.
The front assembly view shows the motor mount.
Exact specifications seem rather pointless here since as
mentioned in the text the motor used as not particularly
desirable and further had highly atypical mountings.
Sim ilarly details of the su pport frames and top plate
are omitted because of the range of possible combinations
of mounting requirements and available material that are
likely to be encountered. The solution adapted to our
available space and material requirements is roughly
shown in the assembly views and Figures 1 and 5.
FOOTNOTES:
lThough not shown in the working drawings the same procedure was used in the spindle S1iffeners.
2These variations were probably due to slight variation to tubing elasticity.
3The present 12" pulley is an inexpensive appliance type
which does not grip the V belt very well.

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THEATRE DESIGN AND TECHNOLOGY

PARTS LIST BY COMPONENT
1. TOP PLATE (1) req'd.
(1) approximately 1/8" to 1/4" x 24" to 36" x
30" depending on mounting (see notes)
(4) 5/16" x 2" Flat head bolts & nuts (see Text)
2. ADJUSTABLE BEARINGS (2) req'd.
(2) 3/8" x 1-3/4 x 4Y," flat iron bar stock
(2) sleeve bearings 3/8" x 3/4" bore or brazing rod
(see Text)
(4) 3/8"xl"machinebolts
(4) 3/8" xl" flat washers
3. RIGHT SUPPORT FRAME ASSEMBLY (1) req'd.
(1) 2" x 2" x 1/8" x 16" angle iron
(2) 3/8" x 3/4" machine bolts
4. 12" DIAMETER 2 GROVE "V" PULLEY 3/4"
FINISHED BORE (1) req'd.
(1) Browning2AK124
Note: A less sophisticated but also less expensive
substitute would be (2) light duty sheaves such as
Central Die Casting's 1200A
5. FORMING ROLLERS (3) req'd.
(3) 3'/,," (min.) dia. x 1-3/4" (rough cut) round bar
stock
6. LOW
(1)
(2)
(1)

SPEED COUNTERSHAFT (1) req'd.
10" x 3/4" diameter cold rolled round bar stock
thrust collars 3/4" bore
2.50" pitch diameter spur gear 3/4" face 12
pitch;
0
14% pressu re angle.
Split taper bushing type recommended (see
Text)
Browning =NSS 12G30 or equivalent
(2) Split taper bushings for above; Browning type
G-3/4 or equ ivalent

7. MAIN FRAME ASSEMBLY (1) req'd.
(2) 6" x 19-3/4" x 3/8" flat iron bar stock
(3) 5%" x 3/4" diameter threaded iron bar stock
(12) 3/4" hex nuts
(4) 3/8" x 5/8" machine bolts (main frame mtg.)
(1) 3/8" xl" machine bolt
(1) 3/8" sq. nut
8. TENSION COIL SPRING (1) req'd.
(1) 5" min. overall length, 1-1/16" approximate
outside diameter; wire diameter approximately
.090" tension coil spring_
9_ ROLLER RETAINING BOLTS (6) req'd.
(6) '/,," x 2" machine bolts
10. MOVEABLE ARM FRAME ASSEMBLY (1) req'd.
(2) 5" x 14" x 3/8" flat iron bar stock
(2) 5" x 3/4" diameter threaded iron bar stock
(8) 3/4" hex nuts
(1) 4-3/4" x 5/8" diameter threaded iron bar stock
(4) 5/8" hex nuts

DECEMBER. 1972

31
Table of Contents for the Digital Edition of Theatre Design & Technology - Dec 1972
