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File D 00.12/122/No. 2922 AIR CORPS TECHNICAL REPORT
AIR CORPS INFORMATION CIRCULAR
PUBLISHED BY THE CHIEF OF THE AIR CORPS, WASHINGTON, D. C.
Vol. VII August I, 1929
REVISED NOMOGRAPHIC COLUMN CHARTS WITH
ISOBARS OF WEIGHT AND TENSILE STRENGTH
Ralph Brown Or~r.
UBRAR'\
JUN 13 Z013
Non·Depo\tm~
Auburn Unh1ers\ ~
(AIRPLANE BRANCH REPORT)
UNITED ST A TES
GOVERNMENT PRINTING OFFICE
WASHINGTON : 1929
REVISED NOMOGRAPHIC COLUMN CHARTS WITH ISOBARS
OF WEIGHT AND TENSILE STRENGTH
(By H. E. WEIHMILLER 1)
This report contains the revised nomographic
column charts for use in the determination of correct
tube sizes for given column and tension stresses. It
is assumed that the user is familiar with the basic
charts and hence the additions are explained only.
Two sets of lines have been superimposed upon each
of the existing column charts. The first set is a mat
of isobars or lines of equal weight per hundred inch
length of tube. Referring to the light full lines, numbered
from 2 to 22 on Chart A-46, the numerals are
the weights in pounds per hundred inch length of
tubing. The weights of standard size tubes, noted by
circled points on the basic mat, can, therefore, be
determined by interpolation between isobars.
The second set of lines are those of equal tensile
strength and are concentric with the weight isobars
inasmuch as each is a function of the cross-sectional
area of the tube. These are shown on Chart A-46 as
heavy broken lines running from 5,000 to 40,000, the
numerals being the tensile strength in pounds. lt
should be noted that the tensile strength is determined
as the product of the cross-sectional area of the tube
multiplied by the ultimate tensile strength of the
metal used, no allowance being made for the efficiency
of welded joints, rivet or bolt holes. The allowabll'
tensile strength of each standard- size tube is r('adily
determined by interpolation between these lines.
Inasmuch as the allowable column load is a function
of the yield point, and the allowable tension load is a
function of the ultimate tensile strength, the corresponding
official values are noted on each chart and
also in Table 1 below.
TABLE 1.-0fficial Air Corps physical properties of metals
Chart
.A.ir Corps I .A.ir Corps
speciflca- specification
(new) tion (old)
Steel
number
Yield
point
Ultimate
tensile
stress
Remarks
A-46. _ .. ------- •. ---.• ·--------------.. ---
A-47b ...... ------ ____ •• ----- ----- ---- •....
A-48a. _. --- •.•. -------- .•• ---- __ •.....••••
A-48b ..• ----------- ----- . . ---- ....... ---..
A-49a. _. --- -----. --- . --- - -----.. -- --- ---- -
A-49b . •.. --- .•.•••••.•.•.•.•.. --- ......•..
A-53. _ ••. ---- ---- •• ----- ---- •... ---.... ---
57-18(}-l
57-180-2
57-18(}-2
57-18(}-2
57-18(}-2
57-18(}-2
57-187
10225
10231
10231
10231
10231
10231
11055
1025 1
X-4130
X-4130
X-4130
X-4130
X-4130
Lbs. per
sq. in
36,000
60,000
I 105, 000
I 105, 000
I 125, 000
I 12S, 000
30, 000
Lbs. per
sq. in.
55, 000
95, 000 Not heat treated.
125, 000 }
}~g; ~
1
. Heat-treated alloy steel.
150, 000
' 55, 000 Hardened.
1 From Heat-Treatment Specification No. 98-10025. .
'From Handbook of Instructions for Airplane Designers, Section II, Part IV, Table 5, and Heat Treatment Specification Ko. 98-10026.
The value and economy elements of the new charts
are best demonstrated by examples.
Example 1.-It is given to determine the most
economical tube for the following conditions:
57- 180-1 tubing.
Design loads, + 9, 000 or - 10, 000.
Length, 60 inches. Fixity=2.
From Chart A-46, a straight edge between 10,000
compressive load and 60 length shows a l}'sX 0.058
tube is satisfactory for compression. This tube bas a
maximum allowable tension load of 18,000 pounds by
approximate interpolation between the strength lines,
and is, therefore, satisfactory. Again, by interpolation,
the tube weighs 9.4 pounds per hundred inches, or
5.64 pounds for the given length.
1 The basic nomographic charts are those published by the Air Corps
in Airplane Design by .A.. S. Niles and others, while the superimposed
isobars of weight and strength are by tbe author of this report.
Example 2.-Determine the most economical t ube
for the following:
57-180-2 tubing, heat treated to 150,000
ultimate.
Design loads= + 12,000 or - 12,500.
Length, 38 inches. Fixity= 1.
From Chart A-49a, the following tubes are satisfactory:
1%X 0.049, 1)/iX0.058, and l ViX 0.065.
From a perusal of their positions with respect to
the weight isobars, it will be seen that the first tube is
not only the lightest but would give the highest plus
margin of the three noted for this particular condition.
Example 3.-Determine the most economical tube
for the following:
57-180-2 tubing, beat treated to 125,000
ultimate.
Design loads= +58,000 or -35,000.
Lengtb=55 inches. Fixity = 2.
64.298- 29 (1)
•
From Chart A-48a, a line between - 35,000 and 55
inches shows three tubes satisfactory for compression.
However, their position shows the l YsX 0.095 to be
about 0.9 pound per hundred inches heavier than the
2X 0.083, and about 2.5 pounds per hundred inches
heavier than the 2XX0.065 tube. The latter, however,
has a maximum allowable tension load of 56,000
pounds, so the 2X 0.083, which has about 63,000
I
2
pounds, is the most economical. With a weight of
14.2 per hundred inehes, this tube weighs 7.8 pounds.
The value of the two sets of superimposed lines in
saving time of referring back to tables and thus allowing
all the necessary data to be obtained from one
reading, together with acting as a guide for economy
in weight in tube size determination, is obvious.
•
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FIGURE!1
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YIELD POINT /05,000 fa~;_
LO/lD5 z5,ooo-1oaooo LB.5.
LcN(jTH.5 0-100 INCttc.5
TEN5. 5TR = 125.000 5~~-ti.
NOTE: HEAVY BROKEN LINES
5HOW TUBE TENS. STR. FOR
ULT. TENS. STR.-= IZ5,0CXh~6~N.
LIGHT FULL L1NE5 SHOW
WEIGHT PER 100 INCHES.
FIGUR~ 4
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FIGURE 5
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FIGURE 6
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Air Service Information Circulars
