Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
AUq'OMOTIVE V~HICLE TIRE-SPANNING BEAM OUTSIDE CALIPERS
This invention relates to beam outside
calipers for spanning the diameter of an automotive
vehicle tire which are yraduated to indicate the
circumference of the tire~
The performance of a racing automobile is
influenced by the relative outer circumferential size
of its tires. Automobile racing may be ~onducted on a
closed race course having parallel straightaways the
corresponding ends o-E which are joined by course end
curves.
In closed course racing it is usually
desirable to obtain as high speed as possible on the
straightaways and slow the speed as may be necessary to
navigate the track end curves~ If all of the tires of
a racing automobile are of the same size, the
automobile tends to maintain a straight course along
the straightawaysJ but it is difficult to change such
straight course to a curved course corresponding to the
curvature of a track end.
On the other hand, if the tires of a racing
automobile on the inside of a curve are smaller than
the tires of the automobile on the outer side o the
curve, the automobile will tend to hold the curved
course. If the differential between the size of the
tires on the inner side of the curve and on the outer
side of the curve is properly selected with relation to
the sharpness of the curve, the automobile will hold
the curved course with little or no steering efort.
An automobile having such tires of differential size in
a straiyhtaway will, however, tend to swerve toward the
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inside of the track instead of tending to maintain a
straight course so that it will be necessary for the
driver to exert a steering effort to hold the
automobile in a straight courser Such steering effort
will be greater for greater automobile speeds and for a
lar~er tire si~e differentialO
Because of the foregoing course-holding
capability of a racing automobile along a straightaway
and in a curve, it is customary practice for the tires
used on the wheels of a racing automobile on the inner
side of the course to be somewhat smaller than the
tires of the automobile on the outer side of the
course. The amount of differential in size will depend
upon the particular race course, the length of its
straightaways and the sharpness of curvature of its
ends, and also will depend upon the individual
preference of the particular racing driver.
Also it is important to be able to select
pracise tire si~es for automobiles used for drag racing
and for road racing or for other types of automotive
vehicles such as tractor-trailers.
Another factor in selecting the size of tires
for an automotive vehicle is the fact that the maximum
circumferential extent of a tire is lnfluenced by the
degree of tire inflation, and the degree o-f tire
inflation is dependent both upon the initial air
pressure in the tire and the amount o-f heat generated
by travel of the vehicle which heats the air in the
tire and consequently increases its pressure.
For the reasons discussed abovel it is
important to be able to measure the circumference of
tiras accurately as a guide to selecting tires.
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P~62~
secause of the time constraints of automobile racing,
it is also desirable to be a~le to measure the size o~
tires quickly, particulaxly if it is necessary to
change tires during a race. It is not acceptable
simply to select a tire indicated to be of a particular
size designation, because the wear on a tire will
change its circumference. Also dif~erent tires may
expand at different rates for the same increase in
temperature resulting from being heated by travel. The
size of tires is measured immediately after test racing
as well as when cold. Consequently~ it has been
customary hereto~ore to measure the actual
circumference of each tire and then to relate the
measured circumferences of tires on the wheels to be on
the inside of the race course to the measured
circumfexence of the tires to be on the outer side of
the race course.
In order to measure the circumference of a
racing automobile tire it has been the practice to
apply a tape measure around the circumference of each
tire~ If the tire was mounted on a wheel supportin~ an
automotive vehicle, it was therefore necessary to jack
up ~uch wheel until the tire was clear of the ground in
order to make such a measurement,
A difficulty with actually measuring the
circumference of a tire mounted on a wheel, whether or
not that wheel is supporting an automotive vehicle, is
that the tire usuallv is crowned to a greater or lesser
extent and the measurement made will vary depending
upon whether the tape measure encircles the tire
precisely in registration with the tire crown
throughout the circumference of the tire, or whether a
portion or all of the tape measure is located at one
side or the other of the crown. To locate the tape
measure precisely Oll the crown is more difficult if the
tire is mounted on a wheel that is attached to a
vehicle, even if such wheel is jacked up~ On most race
cars there is not enough room between the body and the
tire to see the tape.
Another disad~antage to the customary
procedure for measuring the circumference of a tire
mounted on a jacked-up wheel is that it is more
difficult to place the tape measure properly all around
the tire, it is generally more awkward to wrap the tape
measure around the wheel, it is harder to locate the
tape measure precisely on the crown of the tire and the
tendency of the wheel to rotate about its axis and -to
swivel on its axle or spindle generally complicate the
measuring manipulation. The tires become very hot when
raced (approximately 180 F.). They collect debris
when the automobile comes into the pi ts o This debris
must be cleaned off before the tire can be measured
with a tape measure.
It is a principal object of the present
invention to be able to ascertain the circumference of
; an automotive vehicle tire mounted on a wheel that is
supporting the vehicle, instead of measuring the
circumference of such a wheel when it is jacked up off
; the ground.
Another object is to be able to ascertain the
circumference of such a tire quickly~ easily and accurately~
It is also an object to be able to ascertain
the circumference of a tire on a wheel supporting an
automotive vehicle by use of an instrument which is
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easy and quick to manipulate and read, and which can ba
used to ascertain the circumference of tires within a
considerable size range.
More speciEicallyl it is an object to
ascerta.in the circumference of a tire on a wheel
supporting an automotive vehicle by yauging the
diameter of the tire rather than by directly taping its
circumference.
The foregoing objects can be accomplished by
providing automotive ~ehicla tire-spanning outside
calipers comprising opposed tire-contacting members for
engagement with diametrically opposite portions of a
tire, joining means connecting said tire-contacting
members and guidiny said tire-contacting members for
relative movement toward and away from each other~ and
scale means and index means movable relative to each
other in synchronism with movement of said tire-
contacting members relative to each other, said scale
means including a scale line elongated transversely of
but inclined relati~e to the direction of relative
movement of said scale means and said index means, and
said index means includiny a line extending transversely
of the direction of relative movement of said scale
means and said index means and disposed for crossing
said inclined scale line to indicate a predetermined
spacing of said tire-contacting membexs~
The details of the invention will be
described in connection with the accompanyiny drawings
of my preferred embodiment in which,
Figure 1 is a top perspective of an
automobile wheel showing the tire-spanning beam outside
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calipers of the present invention in top perspective
applied to a tire on a wheel,
Figure 2 i5 a top plan of an automobile tire
with the calipers shown in a side view applied to the tire,
Figure 3 is a detail section through a
portion o~ the calipers taken along line 3--3 of Figure
2, and Figure 4 is a ~urther enlarged fragmentary
section of a portion of Figure 3,
Figure 5 is an enlarged side view of a
portion o~ the calipers shown in Figure 2 bearing an
indicating scale of one type, and Figure 6 is a similar
view o~ calipers having a scale of a different type and
wi-th further parts broken away.
In applying the beam outside calipers of the
present invention to the tire T of an automobil~ or
another automotive vehicle for ascertaining its
circumference, it is important that the tire be mounted
on a wheel W, but it is immaterial whether that ~7heel
is in turn mounted on an automobile~ The tire should
be mounted on a wheel, however, because it is desired
to ascertain the circum~erence of the tire when it is
inflated to the desired degree, and such in~lation can
only be accomplished when the tire is mounted on a
wheel.
Although~ as stated, it is not necessary for
the wheel W to ba molmted on an automobile in ~rder to
ascertain its circumference by applying to it the beam
outside calipers of the present invention, such
calipers can be applied to the tire almost as readily
when the wheel is mounted on the automobile and is
supporting the automobile as when the wheel is
unmounte.d.
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The beam outside calipers indicated generally
at 1 are composed of a beam 2 of rectangular cross
section and of a length substantially greater than the
diameter of any tire the circumference of which is to
be ascertained by use of the calipers. An arm 3 is
secured by screws 4 to one end portion of the beam 2
extending perpendicularly from one side of it and of a
length at least as great as one half the width of
the widest tire to which the calipers are to be
applied. Another arm 5 projecting perpendicularly from
the same side of the beam 2 is carried by a slide 6
slidably mounted on the beam 2 for shifting the arm 5
toward and away from the arm 3. Arm 3 and arm 5
projecting from the slide 6 are parallel and both arms
are perpendicular to the length of beam 2. The beam
should be of a sufficient width in a direction parallel
to arms 3 and 5 so that these, arms cannot be cocked
relative to each other when the caliper arms are slid
tightly against diametrically opposite portions of the
tire in a direction axially of the tire.
Normally, in applying the calipers to a tire
the arms 3 and 5 will not be forced against the
circumference of the tire. On the contrary, it is
preferable that the arms 3 and 5 initially be spaced
apart a distance somewhat greater than the diameter of
the tire. The calipers are then moved loosely axially
of the wheel to span the tire, and the beam 2 is moved
lengthwise to draw the arm 3 against one peripheral
portion of the tire. Slide 6 is then shifted along the
beam until arm 5 contacts the portion of the tire
clrcumference diametrically opposite that portion
engaged by arm 30 The beam 2 can then be swung
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slightly about arm 3 as a center to move arm 5
circumferentially of the tire until it is in a position
spaced as far as possible from arm 3 while still
contacting the circumference of the tire during such
swinging movement.
When the position of slide 6 along beam 2 has
been established by such manipulation of the calipers,
the slide is secured in such adjusted posi-tion by
setting screw ball clamp 7O A~ shown in Figure 41 such
screw ball clamp includes the screw 8 threaded into a
tapped hole in the slide 6. Such screw has in it a
blind bore receiving presser ball 9 and helical
compression spring 10 backing such ball. The screw can
be rotated relative to slide 6 in its tapped bore by
turning knob 11 carried by the outer end of the screw.
As the knob is rotated to screw screw 8 inward, ball 9
will be pressed resiliently more firmly against the
edge of beam 2 to press such beam in turn edgewise
against the opposite side of the passage through sllde
6.
The position of slide 6 along beam 2 will
coxrespond to the length of the diameter of the tire T
extending between the portions of the tire
circumference en~aged by arms 3 and 5. Such diameter
; will be located at the crown of the tire because of the
perpendicular relationship of arms 3 and 5 to the beam
2 and their parallel relationship to each other. The
maximum diameter of the tire bears a fixed relationship
to the maximum circumference of the tire, the len~th of
such circumference being times as great as the diameter
of the tire, i.e. 3~14159265 times as great as such
diameter. It is preferred to ascertain the dimensions
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of the tire in terms of its circumEerence rather than
its diameter, because racing automobile drivers are
accustomed to calculate the relationship of sizes of
tires at different locations on the automobile in terms
of circumEerence rather than in terms of diameter.
In order to enable the user of the calipers
to ascertain the maximum circumference of the tire to
which the calipers have been applied in the manner
described above, a scale 12 i~ provided for indicating
the tire circumference corresponding to the position of
slide 6 along beam 2. As shown in Figures 5 and 6, the
scale 12 is of buttress configuration, including
parallel intercepts 13 extending perpendicular to the
length of the beam 2 and parallel to arms 3 and 5,
which are spaced apart distances corresponding to
one-inch increments in the circumfexence of the tire.
Consequently such intercepts are actually spaced apart
7/22 of an inch, or .318 of an inch (0.81 cm). Each
of these intercepts bears a number 14~ indicating such
circumference of the tire in whole inches. In Figure 5
the slide 6 is positioned on beam 2 to indicate that
the circumference of the tire is greater than 69 inches
and less than 70 inches, while in Figure 6 the slide is
positioned on the beam to indicate that the tire
circumference is greater than 78 inches but less than
79 inches.
Most racing drivers are not satisfied to be
able to ascertain the circumference of a tire within a
tolerance of one inch. While the edge or line index 15
of the slide 6 could be used to indicate approximately
what portion of an inch exceeding the numeral adjacent
to such edge is included in the circumference of the
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tire, i-t is preferred that a much more precise
indication of circumference be readily ascertainable.
For this purpose the parallel intercepts 13 are all
made of the same length and one end of each intercept
is connected to the opposite end of the adjacent
intercept by an inclined intercept 16, so that the
scale on the beam 2 is of buttress configuration.
Because intercepts 13 are of e~ual lengths, intercepts
16 also will be of equal lengths and will be parallel.
The index edge 15 of slide 6 will intersect
the inclined intercept 16 joining the parallel
intercepts 13 at opposite sides of the index edge at a
location proportionate to the spacing between such edge
and the adjacent intercept 13 parallel to it that is
not co~ered by the slide. Such proportion can be
ascertained by graduations 17 arranged along the ~ndex
edge 15. In Figure 5 such ~raduations are designated
by decimals of an inch 18, wh~reas in Figure 6 such
graduations are designated by fractions o~ an inch 18'.
The appropriate decimal or fraction of an inch
indicated by the graduation mark closest to the
intersection of the index edge 15 with the inclined
intercept 16 which it crosses will indicate the
proportion of an inch in addition to the full inch of
the adjacent intercept 13 thak is included in the
circumference of the tire for the position of slide 6
along bea~ 2. Thus, in Flgure 5 the circumference of
the tire is indicated as being 69.7 inches, and in
Figure 6 the circumference of the tire is indicated as
being 78-1/4 inches.
While the scales of Figures 5 and 6 are
indicated as being calibrated in inches, the scale on
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the beam 2 could be designed to provide an indication
of the circumerence of a tir~ in metric units of
measurement.
By the use of the beam outside calipers
described above, the circumference of a wheel~mounted
automotive vehicle tire, whether or not the wheel is on
and supporting the vehicle, can be ascertained very
quickly and conveniently. If the wheel W on which the
tire T is mounted is supporting an automotive vehicle,
it will be convenient for the user of the caliper to
apply it to the tire with the beam 2 in substantially
horizontal position as shown in Figure 1 . With the
clamp 7 released, the calipers are applied with the
arms 3 and 5 fitting opposite sides of the tire
circumference loosely. The slide 6 can then be moved
along the beam 2 until the arms 3 and 5 contact
diametrically opposite portions of the tire. With the
slide held in ~uch position along the beam, knob 11 is
turned to set the clamp 7 to fix slide 6 in position on
beam 2. The calipers can then be removed from the
tireO
By observing the position of slide index edge
15 r~lative to the adjacent intercept 13, the whole
number of inches of the tire circumference will be
known. The user can then read the additional portion
of an inchl if anyl in the tire circumference by noting
the graduation 18 or 18' along index edge 15 that
coincides with the intersection of such edge with the
inclined intercept 16 which it crosses.
If desired, the side of slide 6 covering the
side of beam 2 bearing the tire circumerence scale
indicia can be made transparent by providing Eor such
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side of the slide a txansparent panel 19. Such panel
is preferably made of transparent plaskic.
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