AN IMPROVED FRICTION METER
Year: 1874

page_text: LETTERS PATENT to Robert David Napier, of Glasgow, in the
County of Lanark, North Britain, Engineer, for the Invention of
"AN IMPROVED FRICTION METER."
Scaled the 18th September 1874, and dated the 25th March 1874.
PROVISIONAL SPECIFICATION left by the said Robert David Napier
7
at the Office of the Commissioners of Patents, with his Petition,
on the 25th March 1874.
I, ROBERT DAVID NAPIER, of Glasgow, in the County of Lanark,
North Britain, Engineer, do hereby declare the nature of the said.
Invention for "AN IMPROVED FRICTION METER," to be as follows, that is to
say :-
This Invention has for its object the measuring of friction under
various conditions in a more direct and better manner than heretofore,
and an important application of it will be for testing the action of various
lubricants.
The improved friction meter consists of an axle, wheel, or other object
having a cylindrical or other surface of revolution, and which has a¨

page_text: i
bearing piece, bush, or gland applied to such surface, with a definite
pressure obtained by means of a weight or spring. The bearing piece is
also connected to an indicating spring or weight in such a way that
when the axle or equivalent is made to rotate the strain due to the
friction, and which tends to carry round the bearing piece, is indicated.
The axle or equivalent and the bearing piece are made of the metal or
other material or materials, the friction between which it is wished to
measure, and when testing a lubricant it is applied to the contact
surfaces of the axle or equivalent and bearing piece.
.
In one modification the bearing piece is borne up against the under
side of the axle or equivalent by means of a counterweighted lever, from
which it is suspended by links, and the connection to the indicating
spring or weight is made in a direction tangential or nearly so to the
rubbing surfaces.
With this improved friction meter the co-efficient of friction can be
ascertained directly at any instant instead of being got indirectly, and
only after a considerable time, as hitherto; and the indications will be.
more accurate and will yield valuable information never hitherto obtained
as to variations of friction under different conditions, whilst the apparatus
is simpler and less costly than any heretofore used for the same
purpose,
SPECIFICATION in pursuance of the conditions of the Letters Patent
filed by the said Robert David Napier in the Great Seal Patent:
Office on the 24th September 1874.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ROBERT
DAVID NAPIER, of Glasgow, in the County of Lanark, North Britain,
Engineer, send greeting.
.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her-
Letters Patent, bearing date the Twenty-fifth day of March, in the year-
of our Lord One thousand eight hundred and seventy-four, in the
thirty-seventh year of Her reign, did, for Herself, Her heirs and succes-
sors, give and grant unto me, the said Robert David Napier, Her
special licence that I, the said Robert David Napier, my executors,
administrators, and assigns, or such others as I, the said Robert
David Napier, my executors, administrators, and assigns, should at any

page_text: And in order that my said Invention and the manner of performing
the same may be properly understood, I hereunto append a Sheet of
explanatory Drawings, to be herein-after referred to, and representing
simple modifications of apparatus for carrying out my improyements.
In these Drawings the same reference numerals are used to mark the
same or like parts wherever they are repeated.
Figure 1 is a sectional elevation, and Figure 2 is a horizontal section
showing the essential parts of one modification. The friction wheel 1 is
fixed on a horizontal shaft 2 mounted in suitable bearings in any con-
venient form of frame, and the shaft 2 has also fixed on it a pulley 3 to
be driven by means of a belt 4; or there may be substituted for the
pulley 3 a pinion having in gear with it a spur wheel mounted so as to
be driven by hand. The friction block 5 is of a segmental form, and is
shaped to bear on the surface of the friction wheel 1 between retaining
flanges formed on that wheel, but it is fitted so as to be perfectly free
between the flanges. The back or outer side of the friction block 5 is
formed with a groove to receive the lower part of a chain 6, which has
its bottom end attached to the lower part of the block, whilst its upper
end is connected to the spring balance or indicator 7, the arrangement
being such that the chain 6 remains tangential to the same point of the
circle notwithstanding some movement of the friction block 5 in the
direction in which the friction wheel 1 tends to draw it, and which is
shown by the arrow. The friction block 5 is pressed against the friction
wheel 1 by a weighted bell crank lever 8, 9, a pair of arms 9 formed on
such lever having pivotted between them an antifriction pulley 10, which
bears against the outside of the friction block 5. This arrangement
avoids any appreciable resistance to the movement of the friction block 5
being caused by the means for pressing the block and wheel together.
The dial of the spring balance or indicator 7 may be marked to show the
co-efficients of friction, and so dispense with any calculation of results.
Figure 3 is a sectional elevation of a simpler modification of my
friction meter, in which the friction block 5 is applied to the upper part
of the friction wheel 1, and has attached to it by arms 11 a weight 12
hanging pendulum-like below the friction wheel 1. When the wheel 1.
is made to rotate the strain with which the friction tends to carry round
the block 5 causes the weight 12 to move to one side, and this movement
is communicated by a link 13 to an index 14 arranged to sweep over a

page_text: scale having marked on it numbers representing the co-efficients of
friction corresponding to the different positions of the weight.
One important difference between arrangements made according to
my Invention, and any hitherto used for directly ascertaining the absolute
frictional strain, consists in my using a spring balance or its equivalent
to indicate the tendency of a block which is at rest to move instead of
attempting to measure the resistance to motion which a moving body
experiences from friction. By these means I obtain the following
advantages, namely:-The friction indicator is in a fixed position, and
the strain indicated is completely dissociated from the power otherwise
required to work the machine, and as a consequence the power absorbed
or given out, as the case may be, by any variation in the velocity of the
friction wheel does not effect the reading of the friction indicator, the
indication simply varying comformably with the actual co-efficient of
friction of the absolute velocity.
The practical objections to arrangements hitherto employed to ascertain
the co-efficient of friction directly have been so great as to cause them
to be superseded by arrangements with indirect methods and by a very
imperfect and tedious method involving the measuring of heat evolved
in a given time. Moreover by such arrangements several important
questions respecting friction, such as the relative frictions at various
speeds, can hardly, if at all, be obtained, which by my Invention can be
completely answered and disposed of in a few minutes. For example,
my apparatus has disclosed the hitherto undreamt of fact that in the
cases of some oils friction decreases with the speed, whilst with other
oils there is an opposite change.
When my improved apparatus is used for testing or comparing lubri-
cants the oil or other lubricant is applied to the surface of the friction
wheel 1, against which the friction block 5 is pressed.
Having thus particularly described my said Invention and the manner
in which the same is to be performed, I have to state that I do not
restrict myself to the precise details hercin described or delineated, but
that what I believe to be novel and original, and claim as the Inven-
tion secured to me by the herein-before in part recited Letters Patent is,
the combining of friction wheel, friction block, and indicator to form
a friction meter or friction gauge, the said friction block being arranged
to communicate to the indicator the strain with which the friction

page_text: tends to move it from a state of rest, substantially as herein-before
described.
In witness whereof, I, the said Robert David Napier, have here-
unto set my hand and seal, this Twenty-third day of September,
in the year of our Lord One thousand eight hundred and seventy-
four.
Witness,
EDMUND HUNT,
Patent Agent,
Glasgow.
ROBERT DAVID NAPIER. (L.S.)