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CORRESPONDENCE.

STAYBOLTS

Editor American Engineer and Railroad Journal:

The whole secret, I believe, of the staybolt question is the
larger water space. We have proved beyond any doubt that,
by increasing the width of the water space, and consequently
the length of staybolts, we have increased their period of use-
fulness about thirteen times without the slightest change in
the material.

We are still drilling tell—tale holes in the ends of staybolts,
and even on old boilers we drill them and afterward test
them. In this way a great many partially broken staybolts
are discovered.

We are not now putting in corrugated or cupped side sheets
in our fireboxes, because we found that the cupped sheets had
a life of but 18 to 20 months’ service, and, while these sheets
have lasted fully as long as straight sheets, we met with
difliculty in patching them and found that this could not be
done successfully, while with a straight sheet a portion may
be cut out and replaced with a patch which is, of course,
greatly in favor of the straight sheet. I

In riveting up our mud rings we used to put_ the head of
the rivet on the inside of the firebox. We now put the head on
the outside of fireboxes, countersinking the sheet inside and
driving the rivets up flush. There are several points in favor
of this. The first is, that by getting rid of the head there
is no obstruction whatever to putting up side grates. We
used to have to chop out the side grates for the head. Another
advantage is that the corrosive matter does not now stick
on top of the heads and cause the sheets to rust out; also,

» by this method We have quicker work, as the rivet is ham-

mered down flush. The riveting is done on the most im-
portant sheet in the firebox inside, where it is likely to give
us less trouble from corrosion than if it were on the outside.
Chicago, Ill., ROBERT QUAYLE,
Nov. 27, 1899. Superintendent Motive Power
Chicago & Northwestern Ry.

STAYBOLT PROGRESS.

Editor American Engineer and Railroad Journal:

The article in the American Engineer and Railroad Journal
of December, under the above caption, was peculiarly inter-
esting to the writer on account of some tolerably thorough in-
vestigations concerning staybolt practice made in the winter
of 1892-93, the results of which were published in the proceed-
ings of the Southern and Southwestern Railway Club for April,
1893. At that time these results, judging from subsequent cor-
respondence and references, attracted considerable attention,
but in seven years’ ‘time the report referred to has become an-
cient history and forgotten, the subject matter investigated all
over again by others produces the same results and recommen-
dations to be again forgotten. That the same thing has been
going on for generations is plain from the fact that staybolts
of the form recommended in the article referred to last month,
and in the report of April, 1893, have been found in «ancient
locomotive boilers that were being cut up years ago. Some
thoughtful men had investigated and reached the same results
years before, the results to be lost and buried. Our text-books
and treatises, our technical teachers, etc., are largely responsible
for this. I " '

The writer, being familiar with the rules and formulae.
tests, government and L1oyd’s rules, etc., was rather taken
aback at one time when some staybolts were found broken
in three pieces. The boilers in which these were observed were
fitted with circulation sheets, and the stays referred to were
found broken off at the outside sheet and again at the circu-
lating sheet, through which they had been tapped. Here was
an object lesson——the steam pressure and its strains had had
nothing to do with the second fracture, as all strain on the
stay was relieved when the first fracture occurred.

‘ The nextthing that came to the writer’s attention in follow-
ing up staybolt breakages was that bolts broken at the same
places" in boilers of the same. classes and designs, when exam-
ined in place, or by markingtheir position before removal,
showed that they had been broken off in the same way. For

instance, the staybolts at the reverse bends in the sides of
radial stay fireboxes near the middle always showed that verti-
cal bending had broken them, because the line of final fracture,
or “let go,” was always horizontal. Similarly, in certain long
fireboxes the end stays showed a vertical line of fracture, prov-
ing that horizontal bending had been their ruin. Different writ-
ers, who have touched on the subject of expansion of l‘ocomo-
tive fireboxes, have considered the vertical movement of the
box or lifting of the crown sheet, but I have yet to see the
first mention of the longitudinal expansion as a factor in the
staybolt breakages. In a deep, short firebox of the old style,
between frames, the differences of longitudinal and lateral ex-
pansion are so small that no trouble to speak of comes from
them, while the differences in vertical expansion are consider-
able. With modern shallow fireboxes, ten and eleven feet long,
the opposite is the case, and it is the longitudinal expansion
which does the most damage in many designs of boilers.

The writer well remembers the pride with which a prominent
master mechanic some years ago pointed to a large boiler in the
shop wherein all the portions of the firebox where broken stays
were ‘troublesome were strengthened by doubling the number
of stays—p1acing them 21/, inches centers—with the firm convic-
tion that “now, by joining, we won’t be worried any more with
broken staybolts.” The boilermaker and designer places stays,
bolts, braces, etc., to make the boiler as rigid as possible, and
ignores the destructive effect of the expansion and contraction;
or, if he does anythingto meet it, it is as above illustrated,
to try and master it instead of providing for it intelligently.
To attempt to overcome or master the expansion of a boiler
due to heating is absurd, and, when indulged in, is really due
to lack of appreciation of the irresistible power to be con-
tended with. .

Experiments made in England with cylindrical, corrugated
fireboxes, showed that, to shorten a “Fox” corrugated firebox
30 inches diameter, one thirty-second of an inch required a pres-
sure of over 300 tons. What“ would be the power exerted by
a flat firebox sheet 10 feet long, well held to its place, and
prevented from buckling by numerous staybolts, when due to,
say, 1/16 inch of scale, it must expand, say, 1/32 inch in length
more than the outer shell? The power is there and is inevi-
tably absorbed by crushing the sheet or breaking the stays;
then, when the cooling off process comes, the sheet having been
previously shortened, is stretched again. Leaky seams and
cracked and pocketed side sheets are the inevitable result.

Inquiry made in 1892 from 22 prominent and progressive rail-
roads brought out the fact that on some roads staybolts had
to be tested every week, the renewals being a heavy source
of expense and delay to the engines; while on other roads broken
staybolts were rare, it being found sufficient to test them once
a year. Why the difference? The trouble from broken stays
was found to be directly proportionate to the amount of scale
forming matter in the water. Where the firebox sheets became
rapidly incrusted, so that the inner sheet would be many de-
grees hotter than the outer shell, there the broken stay and
cracked sheet and leaky flue were household words; Where

the water was soft and good, so that little or no deposit ever‘

formed on the sheets, both sheets could heat up and cool down
together, broken stays and cracked sheets were rarities, and
staybolts only had to be tested once a year. It is the repeated
bending that breaks the staybolts, assisted of course, by the
strain.

A wire rope, if the ends could be secured steam -tight in the
sheets, would make an ideal staybolt.

But flexibility in the staybolts is only half the battle. The
firebox sheets must expand and contract in all directions more
rapidly than the shell sheets; this expansion and contraction
should be considered in the design of the boiler at every brace
and stay rod, at every seam and corner of the firebox, giving
easy curves and bends at all the corners with room for the
boiler to breathe vertically, horizontally and laterally. The re-
cently illustrated boiler with. a single large corrugated, cylin-
drical firebox, seems to offer a remedy for all these ills, if it

does not introduce other evils of perhaps a worse nature. A’

few years’ hard service for such boilers in districts where the
water bears scale and boilers have to be worked to their ut-
most will bring the answer. '
R0an0ke. Va-. R. P. C. SANDERSON,
December 16,  Master Mechanic’
Norfolk Western Ry