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ROCKEESTOS WIRE & CABLE 00. Division of Cerro de Pasco Corcoraticn
IHTEHaAL MaSRAHEJM
CC: 3.?. Coyle (2) G.3. Buettacr File {)
To: J.F.S. Abbott
-
From; D.A. Charlotte
Subject: small Diameter Type SA tLre
Hew Haven, Conn. January 11, i960
W.E. Tierney recently requested that ve consider a small diameter silicone
rubber asbestos braided wire 'with which ve might possibly get Underwriters0 approval. Reduction in diameter would be accomplished by the use of a finer asbestos braiding yazn to be applied over the standard wall of silicone rubber required for fype SA.
Cur present 9-Cut asbestos yam gives a .0^0" wall (.030" adder). The 18-Cut
asbestos yam that ve use on small sizes of Table ML Mining Cable gives a
.QZT5" vail (.055" adder). We have used some 20-Cut yam, .0225" vail (.04?-'
adder), cut have run into considerable breakage in production due to low
tmsile strength. In order to meat the 60$ minimun asbestos content on very
fine yams, finer carrier threads must be used end this accounts for the lov
tensile strength. We have had fair success when running 2 ends of the 33-cut
yam.
................
Other sizes of yam are available, namely 0, 24, 20-cut, with tensile strengths
of 2, 1 3/4, 1 l/2 lbs. respectively. Cur l8-eut yam has a 2 lb. tensile, and the 30-cut yam a 1 l/4 lb. tensile. It is possible that we could braid success fully with one of the intermediate sizes but this would have to be investigated by R. & D. In any such investigation, braid adders should be carefully checked sad this applies also to the 30-cut yam as ve have very little factual data to substantiate the adder of .045" nov shown on specification cards.
A table of comparative diameters is shown below to indicate approximate overall
diameters vith 9-cut (regular Type SA), 18-cut and 30-cut yam on a solid conductor. Diameter of Type R is shown in last column.
RBB 00713
SC-ELEC-03290
Ccntisued
*2- January 11, I960
Size AWE
9-Cut yarn
Outside Diameter
28-Cut yarn
30-Cut yarn
Type ;
lk .2U3
.218
12 .260
235
10
.281
256
8
350 *
.315-
.208 225 .21)6 305
* .0^5" braid thickness (.090" adder): 8 core diameter is .260".
.171 .188 242
311
The above tabulation indicates that ve can approach Type R diameters cm sizes #10 and 8 AVD. However, an sizes #14 and 12 ARC ve are faced with 3/6k" insulation on Type SA whereas Type S has 2/6V' insulation* If ve decide to contact the Underwriters relative to decrease in asbestos braid thickness,
ve should consider inquiring into the possibility of S/6k" silicone rubber cn sizes #14 and #12 AW.
zm D.A. Charlotte"
RBB 00714