The Locomotive - Lighthouse Survival Blog

1893.] THE LOCOMOTIVE. 133
tlie projecting part heing flared or beaded. It was therefore held in the phite by friction
only. The tube-end where it passed through the plate was increased in diameter by 0.1
of an inch by the expanding process. The thickness of the plate into which the tube
was e.xpanded was § of an inch in sample No. 1075, and J^ of an inch in samples Nos.
1070 and 1077. The test was made by observing the stress necessary to draw the tubes
out of the plates, except with No. 1077, where the tube was drawn only partly out. The
greatest observed stress sustained without the tube yielding in the plate was 0,000 lbs.
for specimen No. 1075; 4,500 lbs. for specimen No. 1076; and 7,000 lbs. for specimen
No. 1077. The observed stress which occasioned yielding was 6,500 lbs. for specimen
No. 1075; 5,000 lbs. for specimen No. 1070; and 7,500 lbs. for specimen No. 1077. The
force was applied parallel to the axis of the tube, and the plate surfaces were held in
j)lanes at a right angle to the axis."
These tests indicated a holding power sufficient for ordinary working conditions,
Fig. 6. — A Flared Tube.
"but since so much depends on the proper use of the Dudgeon expander, some mechanical
engineers were not ready to believe that the general run of tubes thus rolled in were
as effective as our specimens indicated. This criticism is certainly justifiable, and hence
all boiler-makers who take pride in their work and have regard for their reputation
should see to it that the tube-rolling at their shops is well done. The riveting-over of
the ends of the tubes is quite generally practiced, and when well done this makes a very
strong joint; but those who are familiar with this kind of work know that in many
cases the ends of the tubes are frayed out and split, and that until the " thumb tool " is
brought to "bear, the job has a very unpromising look. Such work yields readily to the
action of the heated gases, and after a time the riveting or beading fractures and crum-
bles off, and very little strength remains. This fraying and cracking is some-
times attributed to a want of proper annealing of the ends of the tubes, but it is
•quite as often the result of unskilled workmanship. We have seen it so often that we
are never sure such a job is well done. Another method of fastening tubes into the tube-
sheet, and one that works well, so far as we have investigated, (the test being boilers in
use,) is to adjust the tubes so that they shall project slightly beyond the tube sheet.
They are rolled in Avith the Dudgeon expander, and then with one of the tools shown ia