Metal Worker Plumber & Steam Fitter - Clpdigital.org

Metal Worker
Plumber & Steam Fitter
FLORAL PARK, N. Y., JULY 9, 1920
A
The Magazine for
The Combination Shop
Copyright 1920 by the Architectural
and Building Press, Inc.
Method of Development Including Allowance
to Be Made When Heavy Metal Is Used.
VOLUME 94, No. 2
Patterns for Spiral Chute Around Cylinder
Here is an opportunity too good to be lost to point out the valuable
service that our readers are given.
In our columns has been found the solution for problems which
otherwise would be passed up as too expensive for many men and
occupation for men in centers where it is greatly needed would cease
because the work would go to shops which employ experts and can
handle any character of work required of them.
As the result of its assumption of the burden of the expense of
affording instruction on intricate and unusual problems, METAL
WORKER PLUMBER AND STEAM FITTER has been the means of providing
all over the country qualified men to serve the whole sheet
metaf industry and extend its field. The request for aid on such a
problem and the method of supplying is given in the article below.
CORRESPONDENT writes: "I would like to
ask assistance with a pattern problem which has
given me much trouble . The problem is a
round spiral chute or succession of elbows, to be
made of No. 10 sheet steel, the chute to be 30 in.
diameter, to fit snugly around a 16-inch pipe, as
shown in Fig. 1. The chute must be smooth inside,
so the seam line will be placed on top and follow the
chute down spirally and form a continuous seam line
from top to bottom."
The sections of the chute should be made tapering
so as to slip into each other without stretching. The
sketch shown in Fig. 1 has been drawn from the
correspondent's description. He does not show or
mention the height of each revolution, which must
be known before any elevation can be drawn, so it
has been assumed to be 48 in. for each revolution.
Before proceeding with the pattern, a plan and
elevation must be drawn as shown in Fig. 2. First
draw any horizontal line as A-B and using T as a
center, describe a semi-circle representing the outside
diameter of the 16 in. vertical cylinder. As the inside
diameter of the chute is to be 30 in. and as No. 10
steel is to be used which is 9-64 in. thick, to avoid a
decimal, take J /s in. as its practical thickness, thus
making the outside diameter of the chute 30J4 in-
Therefore lav off 30^4 in. in the half plan, as shown,
emi-circle C-P-D.
As the correspondent required 12 sections in each
revolution of the chute, then divide the outer semicircle
C-P-D into two halves and five full divisions
as shown by c-d-c-f-gAi, through which joints draw
radial lines — to the apex T, extending them slightly
over the outside of the outer semi-circle as shown.
The quickest way to obtain these five whole and
two half divisions is to first space the semi-circle
into 6 parts, then bisect one of these parts and place
a half part from C to c and D to h, then from C
place 5 whole divisions as shown. Now from
C and D erect vertical lines intersecting the extended
miter lines T-e and TAi, at O and o. Take either
distance c-o or h-o and set it off on each miter line
as from d to o, e to o, f to o and g to o and draw
the outlines from o to o, etc. In a similar manner
parallel to the outlines o-o, etc., draw lines tangent
to the 16 in. semi-circle as shown, two of the corners
being marked a and b. Then C-P-D-J-S-H represents
the one-half plan of the chute.
Obtain the center line of the chute in plan, representing
the top seam as follows: Bisect H-C and
obtain I, from which joint erect a vertical line to
intersect the first miter line at 2. Using T as center
with T-.. as radius draw the semi-circle 1-8 intersecting
the various miter lines at 3, 4, 5, 6 and 7 and
from 7 drop a perpendicular line to meet th^> center
line A-B at 8.