Vol. LxIx,'No. 14.}

would be hypothetically required, it would need to be only 8
ft. long instead of 10 ft., as it would be if placed between the
wheels.

This plan of engine has also the characteristic that it gives
very long tubes. By increasing the diameter of these some-
what, there will be no objection to their use, and a large
amount of heating surface will be obtained, which means cor-
responding steam-generating capacity. The driving-wheels, it
will be seen, are placed as near together as their flanges will
permit—which gives short coupling-rods and less liability of
breaking, which is a constant source of terroizto some of us
when we are riding on locomotives. The rods, too, it will be
seen, instead of being below the cab, as in orginary engines,
where they are the most dangerous, are in front, where they
will be less liable to injure the occupants of the cab in case
they or the crank-pins are broken. The feature in the engine
to which there may be some demurral is the single-axle leading
truck.’ There is still considerable doubt in the minds of many
locomotive superintendents and master mechanics with refer-
ence to the safety of such trucks at high rates of speed. The
process of reasoning which leads to this doubt seems to be that a
two-axle or four-wheeled leading truck has been proved by long
experience to be safe, and the inference is then drawn that if
there is only one axle, there will be only half the safety. It
would lead us too far now to examine the premises and the de-
duction which leads to this conclusion. Mr. Rhodes, however,
after years of experience with mogul engines on his road in
fast-express service, has ordered the engine which is illustrated
in this number. He is a cautious man and generally sound in
his conclusions, and has apparently acted with the approval of
his superiors. Then, too, there is the fact that there are hun-
dreds or thousands of mogul and consolidation locomotives
employed in freight service, in which they often run at high
rates of speed, and we have never heard itieven hinted that
they were not as safe in that service as 10-wheeled or decapod
engines. It has been argued, and very plausibly too, that if
a single-axle truck is properly constructed, it is safer than
one with four wheels, and if the reported derailments of 10-
wheelcd express engines is confirmed, it adds plausibility to
that conclusion. Anyway, the railroad public will be inter-
ested in learning the results of Mr. Rhodes’s experience with
his new engines.

Again our subject has extended beyond our limits and may
be taken up again in the ‘future.

A

A
?

THE MOST ADVANTAGEOUS DIMENSIONS FOR
LOCOMOTIVE EXHAUST-PIPES AND SMOKE-
STACKS.*

BY lNs1=Ec'ro1t Tnosxn.

(Continued from page 543.)

II. THE HANOVER EXPERIMENTS (1892-94).

THESE experiments were suggested by the fact that a newly
constructed high-speed locomotive was an exceedingly poor
steamer, and that the usual remedies madeonly a very slight im-
provement. In order to ascertain the reason for this phenome-
non, Herr von Borries, the Superintendent of Motive Power of

‘ the State Railways, decided to make a special in vestigation with

different shapes of smoke-stacks, and had made for that pur-
pose the apparatus illustrated by fig. 12. The author of this
paper was intrusted with the execution of these investigations.
They were commenced in the summer of 1892 at the main
workshops of the railroad company, and continued on until
the autumn of 1894.

The apparatus used is shown in fig.’12. It consists essen-
tially of a lower steam chamber and an upper air chamber.

* Paper read before-the German Society -of Mechanical Engineers.

AND   RAILROAD JOURNAL.

' precisely the same results were obtained.

559

The steam pipe with a diameter of 6.3 in. passed air-tight
through the plate separating the two chambers and carried the
nozzle at its upper end, this piece having an opening ranging
from 3.9 in. to 5.5 in. The stacks subjected to the investiga-
tion had a diameter of 17.7’ in., and were placed over the cir-
cular opening cut in the top sheet of the air chamber. On the
four sides there were four air valves of the same size. It was
the original intention to investigate the effect of various posi-
tions of the nozzle relatively to the lower end of the stack, and
to do this by raising or lowering the nozzle through the means
afforded by the apparatus illustrated in fig. 12. But it devel-
oped that when the nozzle was in its lowest position, the air
chamber itself acted as a sort of stack, and it became possible,
with the stack removed, to obtain a vacuum equivalentto
-} in. water pressure.

In order, therefore, to render exact work possible, and for
which purpose it became necessary to place a cap over the
mouth of the pipe leading from the boiler, the location had to
be obtained by more convenient means. The distance of the
nozzle in question could then be changed without actually
altering the position of the nozzle itself by changing the posi-
tion of the stack by putting welded rings in between its foot
and the air chamber. These rings were welded out of «gin.
plates and were of the form shown in fig. 13. There were 10
o_f these rings, starting with one 1.5?’ in. in height and increas-
ing in height by 1.57 in. By setting several rings on top of
one another the distance of the nozzle from the lower end of
the stack could be increased up to 30 in. or more. ‘

During the tests the joints between the rings were kept
well smeared with a paste, so that they were kept air-tight.
The four air valves were so adjusted for the admission of the
outer air that their combined free area amounted to 14.65 in. X
5.51 in. :: 80.72 sq. in. This latter had previously been de-
termined on a standard passenger locomotive in the following
manner 2 After loosening the slide valve and then fastening in
another in such a way that the steam portswere closed, a mer-
cury manometer was connected with the empty steam chest
of the locomotive and then enough steam was admitted through
the throttle valve, the depth of the fire being the same as that
ordinarily carried on fast runs, to produce a vacuum of 3.94
in. of water in the smoke-box as indicated by the water col-
umn attached thereto. The corresponding readings of the
mercury manometer that measured the steam pressure were
noted, and this was repeated several times until a whole series
of results was obtained, and then an average was taken. Then
a blast nozzle of the same size as that used upon the locomo-
tive was placed upon the apparatus, and steam admitted until
the mercury manometer indicated the average pressure that
had been obtained by the previous experiments, when the air
valves were so adjusted, the same amount of opening being
left in each, that the vacuum indicated by the water column
amounted to 3.94 in. This was then made the basis of the ex-
periments which were thus warranted to correspond closely to
actual practice. As a matter of fact also, as we have already
remarked, the different shapes of stacks that were investigated
with the valves in these positions were frequently transferred
afterward to locomotives under steam and made fast, where
In consequence of
the uniformity of results, the slight difference which existed
between the steam measurements in the steam-chest.and the
apparatus due to the greater freedom of steam flow in the lat-
ter seems to be a matter of no moment.

The position of the four air valves being thus ascertained,
the experiments were then-carried on, admitting cold air in to
the chamber, while. in the actual work of a locomotive, it is

well known that the temperature of the hot gases coming ~

from the fire-box range from 575° to 840° F. Afterward sim-
ilar experiments upon a running locomotive showed that the
difference between the same shaped current of steam as ap-
plied in the apparatus or upon the standing locomotive and
the steam acting intermittently upon a fast-running locomo-
tive is of no importance whatever as far as the action of the
stack is concerned, and though this is not the case with slow-
moving locomotives, it is in no way troublesome to make a

_ transfer or application of the results obtained with the experi-

mental apparatus.‘ It has already been stated here that iso-
lated experiments with the apparatus in no way serve to es-
tablish the formula for the laws of actual service, but that
these can only be fixed by experiments with running locomo-
tives. ‘

The next thing to establish was, how smoke-stacks of differ-
ent forms would act with respect to the creation of the draft.
Here it is a matter of slight importance whether the values of

- the vacuum obtained are in exact correspondence with the
‘values observed on running locomotives or not.

In all the experiments with the apparatus the aforesaid posi-
tions of the air valves were left unchanged, hence the sucking