- ：
* - - - - ----------------------------=~~~~--~
**************~*~~~~ ---------- …____
orts
QN
CAPTAIN chAPPELL's
~~
REP
~~~~ ~~~~======~~--~-------------~--~____... -） ）...） -
ARCHIMEDEAN SCREW.
ON THE
_____. -_- ------------—~~~~T~~~~
* * * : * -s."
---. & rºse.
.*.*.*** *** - -
- ... * **.*.*.** * ** *
*Y.; rºt. “. . . .
**-*.*.*** *
ES
|
N LIBRAR
* : ; ; ; , ;
iiiGA
ſ · * * *，






R E M A R K S
ON
\
“THE REPORTS RELATIVE TO SMITH's PATENT SCREw
PROPELLER, AS USED ON BOARD THE ARCHIMEDES STEAM
WESSEL, IN VARIOUS TRIALS WITH HER MAJESTY'S STEAM
PACKET WIDGEON, AND SUBSEQUENTLY IN A CIRCUMNAVI-
GATION OF GREAT BRITAIN; TO WHICH ARE SUBJOINED,
OPINIONS ON THE SAME SUBJECTS, CONVEYED IN LETTERS
FROM MANY DISTINGUISHED PERSONS. BY CAPT. EDWARD
CHAPPELL, R. N. THIRTEEN YEARS SUPERINTENDANT OF HER
MAJESTY'S STEAM PACKETS AT MILFORD AND LIVERPOOL:”
BY
ALEXAN DE R s. BY R N E;
BEING
A SUPPLEMENT
TO
“OBSERVATIONS ON THE BEST MEANS OF PROPELLING SHIPS,”
B Y T H E S A M E A U T H O R. .
N E W - Y O R K :
\
PUBLISHED BY CHARLES S. FRANCIS, 252 BROADWAY. AND
J. H. FRANCIS, 128 WASHINGTON STREET, BOSTON.
windt's PRINTERY, 152 chAMBERs st.
^* *xe
1841.
Transportation
%55
..T.S)3
su-tºº. • .
Transportation
library
R E M A R K S
ON
*
CAPTAIN CHAPPELL's REPORT's
Steam navigation is a subject of the first importance, and
is viewed with interest by all classes of society; the public
mind is directed to its development, and an unusual degree
of interest is felt for the success of all improvements
connected therewith : it is therefore the duty of those who
undertake to afford information on this subject to avoid
every species of misstatement, and observe the strictest
regard to truth.
At no period has public attention been more excited than
at the present in reference to the Archimedean Screw,
which is supposed by many to be one of the most important
improvements of the day; and as the public were but im-
perfectly acquainted with the details of this invention, the
Reports of Capt. E. Chappell were presented, with a view
to point out its real merits; but instead of doing so, the
Archimedean screw is most extravagantly extolled, and the
best face put upon the whole plan, whilst its most glaring
defects are either concealed or explained away. N ow, what
can be more unfair in a Report, given as a guide to public
opinion, and professedly with a view to explain the merits
6
and demerits of an invention, than to suppress the most
important elements of the inquiry, and give such a one-sided
account of its advantages as would lead to a favorable
opinion, whilst its disadvantages are kept entirely out of
view f Merely to assert this of Captain Chappell's Reports
would be unbecoming in one who has no claims to scientific
distinction: the following remarks are therefore presented,
to show that these charges are fully substantiated, and that
the Reports alluded to are only calculated to mislead the
public. "-----' --------- ----- --- ------ w
For this purpose, it will be necessary to point out that
Capt. Chappell has not, in his account of the “Archimedes”
and “Widgeon,” given the requisite elements for estimating
the exact amount of power applied to each vessel, nor the
resistances opposed to each.
He ought, in the first instance, to have made an exact
calculation of the area of the immersed midship section of
the Widgeon; her exact displacement, with the superficial
measurement of the whole of her immersed body; a com-
parison between the lines of the two vessels, stating the
angle of entrance ; and all other elements requisite in order
to estimate, with every accuracy possible, the resistances of
the two vessels.
In the next place, he ought to have stated the size of the
paddle boxes of the Widgeon, with all other dimensions for
calculating the sectional area of the whole body above water
line exposed to head winds, and the same for the Archimedes,
in order to institute a correct comparison between the two.
Further, the diameter of the paddle wheels ought to have
been stated, their precise dip into the water, depth and
breadth of float, for the purpose of determining whether
rºw
!
any undue expenditure of force, by the receding of the
water, attended the Widgeon—a circumstance of the
greatest importance in arriving at a correct estimate of
power and effect in the respective vessels.
Next, the number of revolutions per minute of the Wid-
geon's paddle wheels, during the trials, and also the pres-
sure of steam and amount of vacuum in the engines of both
vessels, should have been given with the greatest precision,
as indispensable in calculating the precise force exerted by
each. ^.
Also, some statement of the comparative efficiency re-
sulting from the difference of construction in the boilers of
the two vessels, and the quantity of fuel consumed by each,
as a corroboration of the statements made as to the differ-
ent powers exerted.
Let us now contrast these necessary particulars with
those Capt. Chappell has given, when, without reference
to the elements just alluded to, it becomes apparent at one
glance how very imperfect, not to say deceptive, his table
and the remarks that accompany it really are.
CAPT. CHAPPELL’S TABLE.

Dlameter of
& Names. Tonnage. Cylinders, Length of Stroke. Mean draught of Water.
Widgeon, 162 | 39 inches. | 3 feet 1 inch. 7 fect 3 inches.
Archimedes, 237 37 inches. | 3 feet. 9 feet 4 inchess
“The Widgeon is the fastest packet upon the Dover station.
She has 10 horses power more, and 75 tons burthen less, than
the Archimedes, and the mean draught of water of the former is
2 feet 1 inch less than that of the latter.”
It should be here observed, that the conclusion drawn
from the mere difference of tonnage in the two vessels is
S
exceedingly erroneous, since it is well known that neither
the sectional resistance nor the displacement, depends upon
the register of the vessel. Also, the assertion that the
Widgeon has 10 horses power more than the Archimedes
must be viewed as gratuitous, in the absence of those im-
portant particulars before alluded to ; and the difference
of the draught of water in favor of the Widgeon, so point-
edly noted, is only calculated to mislead, since the area of |
the midship section is not stated in connection therewith—
an important omission, when it is remembered that the
Archimedes is rather taper at her bottom, or, as it is tech-
nically called, has a considerable rise of floor, and a keel
of considerable depth.
The important conclusion drawn by Captain Chappell,
“ that the Archimedean screw, even in calms and smooth
water, is decidedly superior to that of paddle wheels,” being
based chiefly on the trial instituted between her Majesty's
steam-packet Widgeon and the Archimedes, in the Dover
roads, the account given of these experiments next claims
our attention.
EXPERIMENTS.
“I. Our first trial was upon a run of 19 miles, upon a W. S.W.
course from Dover roads, with a light breeze aft and smooth
water, but without sails. The engine of Archimedes worked 27
strokes per minute, and the speed of the vessel was 84 knots per
hour. The Widgeon performed the whole distance in 6 minutes
less than Archimedes.”
During this trial it will be seen that the water was .
smooth, with a light breeze aft. The speed of 84 knots is
equal to 9.84 English miles per hour. The stated speed
of the engines being 27 strokes per minute, and the screw
making 5% turns for each stroke of the engine, it follows
9
that the screw made 143.9 revolutions per minute, which,
multiplied by its length, 8 feet, gives a progressive move-
ment equal to 1151 feet per minute, which multiplied by 60
minutes will be 69,076 feet per hour; this divided by 5280
feet (or one mile) shows that the actual speed of the screw
was 13.06 miles per hour through the water; the speed of
the vessel being however only 9.84 miles per hour, it follows
that the “loss,” or “slip,” was 3.22 miles, or precisely one
quarter, which is the same as in a well constructed paddle
wheel.
“2. In returning the above 19 miles to Dover roads, against
a moderate head wind, without sails, the engine of Archimedes
worked 26, and her speed was from 7% to 8 knots. The Widgeon
performed the distance in 10 minutes less than Archimedes.”
The result of this trial is particularly worthy of notice,
as it clearly indicates want of power in the screw of the
Archimedes, and establishes the fact that the slightest head
wind produces great effect on this vessel. The wind is
stated to be “moderate;” very moderate it must be inferred,
since the Widgeon in this trial beat the Archimedes by ten
minutes, whilst in the former trial, when it was perfectly
calm, she beat Archimedes by only six minutes' Although
the Widgeon thus during this trial not only worked up to
the same speed as in the former one, but actually increased
her speed, Archimedes' engines only made 26 revolutions,
which is less than during the former trial. The “slip,”
therefore, during this trial will be as follows:—26 revolu-
tions multiplied by 54 will be 138.58 revolutions of the
screw per minute, which multiplied by 8 feet, length of
screw, will be 1108.6 ft. per minute progressive movement;
this multiplied by 60 minutes, will be 66,515 feet per hour;
10
which divided by 5280, gives 12.6 miles per hour. The
speed of the vessel being stated at from 7; to 8 knots, the
mean will be equal to 7.66 knots, or 8.87 miles, showing a
“slip” of 3.73 miles, or nearly one third, at a time when
the ordinary steamer with its paddle wheels was not in the
least affected by the cause stated in the Report as having
produced this considerable falling off in the speed of the
Archimedes. This is the more remarkable, since the
Widgeon’s greater sectional resistance above water was
counteracted by the stated moderate head wind, and of
course by some effect, however slight, on her paddle wheels;
whilst the efficiency of the screw, working entirely under
water, could not be affected by waves or any undulating
motion of the surface of the sea. \
The unfair comparison made in reference to this second
experiment between the Widgeon and the Archimedes, in
which the “low mast and snug rig” of the former are stated
as advantages over the latter, cannot be overlooked. How
came Capt. Chappell to forget to notice that the Widgeon
had paddle boxes greatly increasing her beam, and project-
ing some six or eight feet above deck f thus nearly doubling
her sectional area exposed to the wind.
The result of the third experiment corroborates the
opinion before given, that Archimedes is sensibly affected
by the slightest head wind, and that she requires a perfect
calm in order not to be subject to a great amount of “slip,”
for in this trial the sea is stated to be “smooth as glass,”
and accordingly we find that the Widgeon beat Archimedes
by only three minutes instead of ten minutes as in the last
experiment. It should be here borne in mind, that these
experiments were of a practical nature, and should have
11
formed the proper guide for Capt. Chappell in determining
the exact amount of “slip.”
That a statement so important as the one lyeſore referred
to, as to the “decided superiority” of the Archimedean
screw over the paddle wheel, and that “in a dead calm the
speed of the vessel is less than one-sixth short of the rate
at which the screw revolves,” should have been ventured in
contradiction to the facts so clearly demonstrated by these
experiments, is truly a matter for surprise. Why such
inaccuracies are permitted in a Report of such paramount
importance, the author is at a loss to conceive ; and is
compelled by a sense of justice to observe, that if these
unfair representations arise from oversight, such careless-
ness is, to say the least of it, not very creditable in a Report
given as a guide to the public.
There are other improvements in steam navigation, of
far greater value than the Archimedean screw, which were
—though not with an equal degree of “management”—
presented to the world at the time Mr. Smith departed
from his original adaptation of the Archimedean screw to
introduce modifications suggested by the improvements al-
luded to : it is therefore the height of injustice towards those
who originated these really useful and important improve-
ments to conceal such a radical defect of the Archimedean
screw as, amongst many others, its real amount of “slip.”
But these are not the only instances of unfairness to be
censured, for the whole Report abounds with similar cases ;
and had it been the production of a stockjobbing company,
anxious to allure the public, its contents could not have
been more plausible, whether its inaccuracies arise from
mistake or not.
12
The startling assertion made by Capt. Chappell (Reports,
page 85) that the aggregate steam power of Archimedes'
engines does not eacceed 66 horses, must not be overlooked.
By referring to the accounts of the experiments in the
Dover roads, it will be seen that the speed of Archimedes'
engine in a perſect calm was 27 strokes per minute. Taking
this speed for the basis of our calculations, it follows, that
if the stated power of 66 horses be correct, the effective
pressure on the pistons of the Archimedes amounts to only
64 lbs. per square inch; for one horse power being equal
to 33,000 lbs. raised one foot high per minute, 66 horses
will then be 2,178,000 lbs. raised one foot. Now the dia-
meter of the Archimedes' cylinder being 37 inches, its
superficial measurement will be 1075.2 square inches; and
the stroke being 3 feet, the two pistons will travel through
a space of 324 feet per minute; which number, if divided
in the above 2,178,000, gives 6722; and which, if divided
by the superficial measurement of the piston, shows that 6+
lbs. effective pressure to the square inch only will be suffi-
cient to exert 66 horses power This proves incontestibly
that the stated power of the Archimedes is vastly under-
rated, particularly since the steam pressure in her boilers,
a subject carefully avoided by Capt. Chappell, was carried
several pounds above that used in ordinary steam vessels
with Bolton & Watt’s engines, which form the data for
estimating the power of marine engines. Eight pounds
pressure to the square inch being usually estimated as the
effective pressure in ordinary marine engines carrying LEss
pressure in the boilers than the Archimedes, it must be
conceded that 9 lbs. pressure to the square inch would be
only a fair estimate of the effective pressure of her engines,
\
13
in which case their power will be ninety-sia, and not sixty-
six as most erroneously stated.
Passing over Capt. Chappell’s general observations, let
us proceed at once to consider his detailed remarks under
their various heads.
“I: Form of Screw.
“The screw, as originally introduced into the Archimedes,
consisted of one entire turn, 8 feet in length and 7 ft. in diameter.
As it was found that the screw in this form was larger than the
steam-engine could drive at the requisite velocity, the diameter
was gradually reduced to 5 feet 9 inches. Subsequently, for the
sake of compactness, it was divided into two half turns, which
reduced it to half the length; but as the two half threads were 4
feet each in length, the superfices of the screw remained the same-
The propeller, therefore, used in the late circumnavigation of
Great Britain, consisted of two half threads, 4 feet each in length,
and 5 feet 9 inches in diameter. *.
“The forms of screw tried by Mr. Smith before he adopted the
one now in use on board the Archimedes, varied from three turns
to a single turn ; and also to the division of the single turn into
two, four, six, and eight parts or segments; but Mr. Smith de-
clares it to be his opinion, that one entire turn, the length and
diameter of which shall be equal, is the most effective form of
propeller. The two half turns, however, or even four quarter
turns, as they maintain the same superfices, while they occupy
less fore and aft space in the dead wood, afford a more compact
form of propeller, and one more applicable to vessels in which the
run is short.”
It is here stated that the screw of SEVEN feet diameter
was larger than the steam-engine could drive at the “re-
quisite” velocity . A very different reason, however, may,
be given to account for the want of power in the engines to
turn the screw at the said “requisite” velocity, viz. the
immense resistance produced by the friction or adhesion of
the water against the thread of the screw.”
* See Observations on the best Means of Propelling Ships, p. 9 to 14.
<)
aº
14
Capt. Chappell’s statement, that Mr. Smith, before he
adopted the screw now on board the Archimedes, tried not
only a screw divided into two parts but also divided into
eight parts or “segments,” calls for particular notice. It
would be interesting to know where and when Mr. Smith
tried these eight segments; for it is known to several per-
sons that Mr. Smith was on board the iron steam-boat
Robert F. Stockton, fitted with Capt. Ericsson's propellers,
during the successful trials therewith, in the presence of a
great number of scientific gentlemen, several months before
the Archimedes was ready. Probably Mr. Smith alludes to
the information obtained through the courtesy of Captain
Ericsson, in permitting him to inspect his propellers. If
so, it must be confessed that Mr. Smith did not make such
correct observations as he was enabled to do by the open
and frank manner in which he was permitted to examine
the practical operation of the propeller, which was remark-
able for its perfect action and very trifling amount of slip
and loss of power. y
The proposed “four quarter turns,” or rather the four
spiral wings, present an entirely new feature, and surely
cannot be termed an Archimedean screw : a spiral or
“smokejack wheel” would be the appropriate denomination
of such a contrivance, and one which Mr. Smith certainly
cannot claim under HIS patent.
“2. Angle.
“Mr. Smith states his experiments as having extended to all
angles of the screw from 30 to 50 degrees; but in the propeller
used on board the Archimedes, the flange or thread of the screw
stands at an angle of 45 deg. with its axis or shaft. Constructed
upon this angle, the screw, when put into action, drives off water
in radii diverging equally from every part of its periphery; and
15
upon first starting in a dead calm, I have observed a column of
water thrown astern of the ship, in the shape of an inverted cone,
from which it may be inferred, that the whole force of the screw
is directly propellant in the line of its axis, while that of paddle
wheels is partly wasted in lifting up the bows of the vessel and in
raising water behind.”
Capt. Chappell here states, that the angle of the thread
of the screw used in the Archimedes is 45°, and in another
place that the number of revolution: given to it amounted
ordinarily to 138% per minute. Let as see if this statement
of the angle can be correct. The diameter of the screw is
stated to be 5 feet 9 inches; hence the circumference will
be precisely 18 feet. Now since the angle is 45°, it follows
that the progressive movement of the screw must be 18 feet
for each revolution, and therefore that the progressive
movement during one minute (with 138% turns) will be
2495 feet, or upwards of 28 miles per hour, while the speed
of the ship at no time exceeded 10 miles. This statement,
therefore, must be untrue, or the asserted “slip” of only
one-sixth is vastly underrated.
“3. Area.
“The area of the screw now in use on board the Archimedes
bears a proportion to the immersed portion of the ship's midship
section as something less than 1 to 4. In other words, at the
usual draught of 10 fect, the area of the ship's midship section
immersed is stated to be 143 feet; and the area of the screw,
minus the shaft, is 33 feet. It should be observed that the surface
of the screw must depend on and be confined to the area of its
diameter, and not by its spiral length of flange or worm. In
applying the screw to larger vessels, it will not be necessary to
increase its dimension to such an extent as might at first appear
requisite, since a small addition to the diameter gives great addi-
tion to the area.”
In head No. 1, where the object appears to be to extol
16
the small dimensions of the screw of the Archimedes, Capt.
Chappell states its diameter to be 5 feet 9 inches; but in
this place, where his object evidently is to prove a very large
area as compared with the area of the midship section, he
states that the screw presents a surface of 33 square feet,
besides the sectional area of the shaft | Now, a simple
calculation will prove, that in order to present that amount
of surface, the screw represented in head No. 1 to be 5 feet
9 inches must be 6 feet § inches in diameter. On this point
it is impossible to be mistaken ; Capt. Chappell having
stated distinctly on page 9, that the two half turns of the
screw used in the experiments were equal to “one entire
turn.”
w
“8. Noise.
Besides the remarks under this head, Capt. Chappell—
page 5 of the Reports—observes :
“There are two points of great practical importance respecting
the screw propeller, which ought not to pass unnoticed:—1. The
noise made by the spur wheels, used in giving the necessary
velocity to the propeller shaft.—2. The liability of those wheels
to rapid wear and to accidental derangement.—The noise alone,
I conceive, would prevent its being applied to any of her Majes-
ty’s home packets, in particular. Mr. Smith, however, proposes
[PRoposes!] to obviate this objection by substituting spiral gearing
in lieu of the present cogs; and a model of this method has already
been exhibited to the Lords Commissioners of the Admiralty.
As it is the intention of Mr. Smith to make trial of this alteration
'shortly, I abstain from giving any opinion upon its merits at
present.”
That a contrivance so fanciful as “spiral gearing” will
obviate the highly objectionable noise and tremulous motion
of the cog wheels, is gratuitous, and much to be doubted ;
besides which, nothing can be more incorrect than to com-
pare the noiseless motion of such paddle wheels as those
*
17 .**
of the steam frigate Medea to the very loud rumbling noise
of the cog wheels of the Archimedes, and which as a matter
of course will increase with the wear of the cogs,
“10. Slip or Loss of Power.
“This is so difficult a matter to determine with accuracy, that
it is with considerable hesitation I offer any remark upon it.
Most of the engineers whom I have consulted calculate the slip
of the best constructed paddle wheels at one-fourth ; that is, the
speed of the ship is one-fourth less than the speed at which the
wheels are traveling, The screw in the Archimedes being of an
cight feet pitch, would, if worked in a solid instead of a fluid,
advance eight feet at every revolution; but it appears by repeated
trial of the log, as well as by observation of measured distances
on the shore, that in a dead calm the speed of the vessel is less
than one-sixth short of the rate at which the screw révolves. In
this most essential particular, therefore, the screw has an advan-
tage over the paddle wheel as one-sixth to one-fourth ; and in
any future experiment I am confident that this superiority of the
screw may be materially increased, by improvements in the
method by which it is fitted and worked.”
In this important article, Capt. Chappell has not only
underrated the amount of “slip,” but he altogether passes
over the “loss of power,” so ingeniously linked together with
the slip. Now, what can be more uncandid than that of not
at all adverting to the great waste of power which must
necessarily be occasioned by the friction or adhesion of the
water against the two sides or surfaces of the thread, when
it is considered that its speed towards the outer edge
amounts to upwards of 30 miles per hour f
The great loss of power thus attending the use of the
Archimedean screw Capt. Chappell was bound to point out,
in a Report professedly drawn up for the information of the
public.”
* Sec Observations on Propelling Ships, p. 9 to 14.
18
“16. Application to Ships of War.
“In vessels of war, the screw propeller admits of the whole
machinery being kept below the water line—of the ship being
ordinarily used with sails only, but of being converted into a
steamer in a few minutes; or, as the action of the screw is equal,
whatever may be the heel or inclination of the ship, the screw
will allow of using both sails and steam when required. The
propelling apparatus is placed wholly out of reach of injury from
shot, the falling of masts, or collision with other vessels ; the
whole broadside battery is left unobstructed : and should every
mast be shot away, the propeller might still enable a ship to
maintain an efficient fighting position, to follow an enemy if re-
quired, or to convey the vessel safely into port, however crippled
in condition.”
Although the Archimedean screw revolves entirely under
water, still the steam machinery necessary to work it is as
much exposed as in ordinary steam vessels, and in addition
to which the complicated wheel work for giving the requisite
high velocity to the screw, is not only placed above water
line but is partly above deck. Is it not matter for surprise
that Capt. Chappell, in recommending the Archimedean
screw so strenuously, should have omitted to notice these
great defects, which confessedly are of such magnitude as
to render the whole plan almost useless for war purposes?
Sufficient has been said in the foregoing remarks to
point out the real value of Captain Chappell's Reports;
but should Mr. Smith favor Captain Chappell with the
elements before alluded to, the subject will be again
resumed, and numerous other inaccuracies and erroneous
conclusions pointed out.
Since it is impossible to attribute to a gentleman of Capt.
Chappell's high character any intentional misstatement, the
author has not the remotest intention of imputing improper
motives to that gentleman ; at the same-time, he cannot
19
refrain from expressing his unfeigned regret that Captain
Chappell should have hazarded such decidedly favorable
opinions on a subject of vast importance, on which he
evidently is not correctly informed.