Note: Descriptions are shown in the official language in which they were submitted.
CA 02485543 2004-04-20
FIELD OF THE INVENTION
A low-cost gauge or jig for checking the wheel alignment of cars and other
vehicles. The
gauge uses the disc brake rotor as the reference plane for alignment.
BACKGROUND OF THE INVENTION
Wheel alignment saves fuel, provides safer steering and braking, and reduces
tire wear. There
is a need for a reasonably accurate and low priced gauge that small shops and
gas/service
stations can quickly use to check wheel alignment as a routine service for
customers, and to
guide wheel alignment after replacing shock absorbers, ball joints, and
steering-rod-ends.
SUMMARY OF THE INVENTION
The present invention is a gauge that uses one or more double-ended magnetic
extension rods
of equal length that pass through the vent or spoke openings in the vehicle's
wheels (front
and/or rear) and magnetically attach to and extend perpendicularly from, the
disc brake rotor
surface. Preferably three extension rods are used. A flat metal plate (steel)
is attached to the
magnetic outer ends of these extension rods to become the planar reference
surface clear of the
vehicle's bodywork, from which wheel alignment is determined. Alignment arms
with lasers are
magnetically attached to each plate. The arms have perpendicular abutment arms
that contact the
leading edge of each wheel. The alignment arms can be attached horizontally to
project their
laser beams across the the front of the vehicle onto a target sheet where the
laser dot indicates
"toe"; or vertically, to project the laser beams across the top of the
vehicle's hood to check for
"camber". When the steering wheel is turned in increments, the lasers dot's
sequential
locations on the target trace an arc (connect the dots on the target) the arc
depicting a wheel's
caster setting.
A detailed explanation of the complex determination of caster measurement is
given at:
http://www.hunter.com/pub/undercar/2573T/steer.htm.
If wheel alignment is required, the gauges are removed, the vehicle is jacked
up on its
suspension arms (not on the vehicle's frame) just enough to allow removal of
the wheels. In this
way the suspension remains weight loaded, just as it is when on the ground.
The gauges are
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then remounted to the exposed brake rotors, the abutment transferred to
contact the rotor's
circumference and corrective adjustment carried out unfit the laser dots on
the targets indicate
correct alignment.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 A perspective view of a disc brake rotor and plate supported thereon
using equal
length, double ended magnetic extension rods, and with laser lamps on the
metal
disc beaming to targets at the front, rear, below, or above the laser;
Figure 2 a side view of a wheel showing the extension rods inserted between
spokes;
Figure 3 a front view showing the wheel, brake rotor, extension rods, metal
plate, lasers, and
targets above and below the laser;
Figure 4 a perspective view of an magnet-ended extension rod and showing an
offset adaptor
for the inboard end for reaching discs whose diameter smaller than the wheel's
vent hole circular pattern;
Figure 5 a top and/or front view of the tool installed on two wheels showing
the laser beams
being non-coincident indicating an (exaggerated) degree of toe-in for a top
view,
and, of positive camber in a front view;
Figure 6 shows the same view with the wheels removed and a clamp used to hold
one
alignment arm to the rotor;
Figure 7 shows a side view where the alignment arm is held to the extension
rods using a
clamping arrangement and an abutment rod contacts the front of the tire;
Figure 8 the same embodiment with the wheel removed and a rear abutment rod
contacting the
rear of the rotor;
Figure 9 shows a top view of the same embodiment;
Figure 10 shows an embodiment where the plate is resting on the ground and the
alignment
arm is magnetically attached to the plate, a support rod and level allow each
side to
be positioned identically, and a locating pin in the alignment arm engages a
hole in
the plate;
Figure 11 shows the same embodiment used vertically to test wheel camber and
showing the
abutment rods contacting the top center of the tire, and showing on one gauge,
how a mirror may be used to project the laser beam towards the mechanic
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adjusting a wheel's alignment;
Figure 12 shows a front view of the same embodiment;
Figure 13 shows an embodiment with two linear bearings added;
Figure 14 shows the same embodiment with a single double motion linear
bearing;
Figure 15 shows an embodiment with a pivoting bearing added;
Figure 16 shows the measurements needed to calculate the sine of the degree of
the wheel's
angle;
Figure 17 shows a simple single rotatable extension rod embodiment with a
magnet on one
and and a laser on the other which attaches to an exposed brake rotor;
Figure 18 shows the same embodiment where the rod passes through an opening in
the wheel
to reach the brake rotor;
Figure 19 shows an end view of the two alignment arms and how the laser lamps
may be
offset on the arms so that the beams are clearly visible on the target arm and
not
obstructed by the laser lamp body or its lens;
Figure 20 shows and end view of how a magnetically attached carpenter's
inclinometer or
angle indicator may be used in conjunction with part of the present invention
to
determine wheel camber angle.
Figure 21 diagrammatically shows how a common laser distance measuring unit
with
calculator may be incorporated in one alignment arm to quickly measure the
distance between the two alignment arms and compute the wheel angle for this
distance and the distance of misalignment of the laser dot on the target with
the
opposing laser lens at the target's center;
Figure 22 shows how the laser may be rotatably mounted on the alignment arm
with index
marks to indicate wheel TOE angle;
Figure 22 shows how an end portion of the alignment arm may be made rotatable
also with
index marks to indicate wheel CAMBER angle.
DETAILED DESCRIPTION OF THE INV ENTION
Vehicle wheels are factory aligned (actually misaligned) in the forward plane
to have a
specific degree of "toe" (misaligned to aim forwardly towards or away from
each other) and in
the vertical plane to have a specific degree of "camber" (misaligned to aim
vertically towards or
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away from each other).
Checking alignment of wheels using the present gauge is done from the
perspective of the
wheel's disc brake rotor B, which is necessarily precisely planar with the
wheel. In the preferred
embodiment shown in Figs 10-15, several equal length extension rods 1 having
magnets la at
each end are used. The inboard ends of these rods 1 pass through wheel
openings D' and attach
to rotors B. Plate 2 rests on ground G and attaches to the outboard ends of
these rods 1. Plate 2
is therefore planar and parallel to rotor B and to wheel A and serves as the
reference surface
onto which alignment indicators are mounted to conduct the wheel alignment
check.
Two alignment arms 2a have three mounting magnets 54 at their inboard end that
hold arms
2a planar to plates 2. The outboard ends of alignment arms 2a have lasers 3,
levels 12, and
perpendicular tire abutment arms 20. The lasers 3 and abutment arms 20 are
spaced identically
on each arm 2a. In manufacture, the lasers 3 are adjusted and locked so as to
aim
perpendicularly dead center into each other's lens when the two arms 2a are in
precise mirror
alignment with each other.
In use, abutment arms 20 each touch the outer circumference and leading edge
of their
respective wheel A. Abutment arms 21 are used to contact the rear
circumference of their
respective rotor B after the wheels are removed.
Each arm 2a may have a support 2b which can be set to a same arbitrary height,
and/or, to the
same height above ground G as hole 53 (or other shaped apertures such as
horizontal and
vertical slots) in plate 2. Optional locating pin 22 on arm 2a can then engage
hole 53 which
makes arms 2a level with ground G as indicated by level 12. The pin 22 and
hole 53 can be
used to best advantage when the workspace has smooth and level ground G.
The laser's beam 4a cross the vehicle towards opposite targets 51 which have
as their center
the the other laser's emitting lens 3a. The measured amount of deviation 11 of
the laser dot 10
(i,e., a red dot) from the center of the target (laser lens 3a) indicates that
wheel's state of
alignment. If the arms are horizontal to check for "toe", the effective
deviation 11 will typically
be in front of or behind the target center and will show "toe-out" or toe-in"
respectively. If the
arms 2a are vertical the effective deviation l la will typically be below or
above the center of the
target and will indicate "positive camber" or "negative camber" respectively.
Because the plate 2 is planar with rotor B and wheel A, the alignment arm 2a
is also planar
therewith and will in fact show both toe and camber when in either the
horizontal or vertical
position. However the gauge's accuracy is increased when the two checks are
made in separate
CA 02485543 2004-04-20
horizontal and vertical positions.
As shown in Fig 16, measuring deviation 11 (value D) and arm spacing 100
(value S)
provides the two values for a ratio (11:100 or D/S) the resultant of which is
the SINE (a
number) of the wheel's angle. Published trigonometric tables or a calculator
is used to convert
the SINE number to the wheel's actual angle.
When it is shown that alignment is required, the vehicle H is jacked up via
its suspension
arms (so that the wheel's angles are not altered) and the wheels are removed
to gain access to
their adjustment means (bolts and nuts). With the wheels off, the two gauges
are reassembled to
the exposed rotors and adjustments made to bring the laser dots 10 into
conformity with the
vehicle's alignment specifications.
With the wheels off, extension rods 1 may have inboard clamp means lc to
firmly grasp the
rotor B during adjustment, and, rear abutment rod 21 is used to locate against
the rear of the
rotor B. Several precision-spaced placement holes for abutment arms 20, 21 may
be furnished
along the arm 2a as shown in Fig 10. A cutout in plate 2 (Fig 11) will allow
arm 2a and
abutment rod 21 to reach smaller diameter rotors B.
Fig 12 on the left side shows how a mirror 101 may be used in conjunction with
a transparent
end 103 on alignment arm 2a to direct a reflected laser beam 102 towards a
mechanic adjusting
a wheel's alignment for remote viewing of the alignment progress. The mirror
101 and/or arm
2a may be marked to show the zero point when the arms 2a are parallel. Other
markings on the
mirror 101 and on targets 51 may be used as a ruler to measure deviation 11 a.
A two-way
mirror with the laser 3 behind it could also be used to effect the same remote
viewing (not
shown).
Alternatively the lasers 3 may be located above and below the center line of
each respective
arm 2a so that the beam 4a is visible on the target arm 2a and not obscured by
its laser 3, as
shown in Fig 19. Abutment arms 20, 21 may have a broad flat shape as shown in
Fig 7 to more
accurately locate tangentially to the leading/trailing edge of wheel's/rotor's
periphery. Also an
angle plate or post may be placed on the ground in front of the wheel so as to
contact the
wheel's leading edge and the abutment arm then brought into contact with it
(not shown).
Further the abutment arm 20 may be removably attached so that it can be
quickly repositioned
to become abutment arm 21 to contact the rear of the brake rotor. In addition,
the alignment
arms 2a may be of equal length (distance from outboard laser lens to the
inboard end) and long
enough so that in the vertical mode, the lower ends of arms 2a each contact
the ground G (not
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shown) serving the same positioning/locating purpose as abutment arm 20 and
eliminating the
locator pin 22 and abutment arm 20.
Figure 20 shows how a common hardware store magnet inclinometer may be
attached to the
plate 2 so as to measure wheel camber without the use of arm 2a.
Figure 21 diagrammatically shows how a common distance measuring unit laser
101 having
emitting lens 3a and with associated calculator 105, may be incorporated into
one alignment arm
to measure the distance between the two alignment arms 2a so as to quickly
compute the wheel
angle based on the ratio of distance 100 (Fig 16) and deviation 11. This laser
distance
measuring may be integrated into existing laser 3. The calculator 105 may also
be connected to
laser 101 such that the laser-measured distance 100 will be automatically
inputted, ready for
input of the deviation 11 into the calculator 105. The angle is then displayed
by the calculator
105. In greater detail, the calculated result of the ratio deviation 11
divided by distance 100,
results in a number which is the ARC SINE (ASIN) of the angle between the two
wheels.
Stated otherwise, the calculated ratio result is a number that is the SINE
value of the wheels
angle, such that, from a common table of trigonometric values, the SINE value
number can be
looked up in SINE Tables and across from that number, the angle can be read.
In another embodiment exemplified by Fig 13, the alignment arm 2a of the
preferred
embodiment is split into two pieces 63, 64 joined together by linear bearing
60. This allows the
measuring end 63 (comprising laser 3 and abutment arm 20) to be quickly
adjusted, as shown
by arrows 61, to bring abutment arm 20 to contact the tire, Further, a second
linear bearing 62
may be used to separate the attachment end of alignment arm 64 from its
carrier 55 (which
attaches or is part of plate 2). This bearing 62 allows split alignment arm
63, 64 to move
vertically, as shown by arrows 64. A second support 2b may be added and knobs
2m can be
used to turn a threaded support 2b to adjust arm 63, 64 level and to adjust
its height above
ground for different wheel sizes. A variation of this embodiment shown in Fig
14 also includes
keeping the one piece alignment arm 2a and using a double action linear
bearing 70 attached to
carrier 55 which is magnetically or otherwise fixed to plate 2, This
arrangement allows
alignment arm 2a to be moved friction free in both required directions 70
quickly and
accurately. Thumb screws (not shown) may be added to bearing 70 to lock arm 2a
when it is in
position.
In yet another embodiment shown in Fig 15, a rotating bearing 80 between
Garner 55 and
plate 2 allows Garner 55 and arm to be rotated 81 for leveling or for moving
to/from
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horizontal/vertical position, while linear bearing 70 provides fore and aft
motion 61 of arm 2a to
bring abutment rod 21 to contact wheel A as required to check wheel alignment.
Fig 16 shows the measurements 11, 100 (exaggerated for clarity) needed to
calculate the
degree of toe or of camber of a wheel using the present invention. Lasers 3
project beams that
deviate from dead center by deviation 11 which is made equal on each side by
turning the
steering wheel; right and left alignment arms have a spacing 100. By way of a
"toe alignment"
example, if deviation 11 measures 1 inch and spacing 100 measures 50 inches
then each
wheel's "toe" angle is that angle whose SINE is 0.020 (1-50). From
Trigonometric SINE
Tables this angle is 1.6 degrees (or 1 degree 10 minutes) per wheel, or 3.2
degrees total toe-in.
Table 1 below is a partial reprint taken from the Internet of wheel alignment
specifications for a
Dodge Neon car (http://www.neons.org/neontsb/TSB/02/020694.htm).
Table 1
FRONT WHEEL ALIGNMENT
TOTAL TOE 0.30° IN TO 0.10° OIJT
CAMBER -0 4° TO +0 4
Thus for this particular vehicle using the above example, the wheel "toe"
alignment is
incorrect there being excessive toe-in. Adjusting the vehicles steering arms
(tie rods) until the
deviation 11 measures, say, zero inches, would bring this vehicles alignment
to within factory
specifications. Likewise for camber.
In Fig 2 a wheel has wheel nuts or studs G and center hub C. Disc brake has
rotor B and
caliper E attached with bolts F. Disc brake rotor B runs planar with a wheel A
since they are
both accurately mounted on the same axle (not shown). With the wheels A on the
ground,
access to the rotors is through openings D' such as those between spokes D
common in alloy
wheels or through the round vent openings in plain steel wheels (not shown).
In all Figs
extension rods 1 are equal length and their inboard ends contact the brake
rotors B. The inboard
ends of rods 1 may attach magnetically or by clamp means lc as in Figs 6 and
9.
Fig 1 shows how plate 2 (sheet steel) is held planar to rotor B using at least
three extension
rods 1. Plate 2 then becomes the surface onto which laser or other sighting or
measuring tools
can be mounted. Plate 2 may be of different sizes or have suitable cutouts to
adapt to larger and
smaller vehicle rotor diameters
Extension rods 1 are equal-length and have strong magnets la (rare earth
magnets) at each
end. Where the rotor B is smaller than the circle pattern of the vent holes of
a wheel, an offset
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lg shown in Fig 4 can be used on the inboard end of rod 1 so that the magnet
la on the offset
contacts the rotor B.
Once the rods l and plate 2 are assembled onto the rotors B of the wheels A to
be checked
for alignment, various types of indicator devices may be attached to plate 2
which is now planar
and parallel with the wheel A.
In a simpler embodiment, laser 3 is rotatably attached by magnetic or other
means such as a
bearing to plate 2 at the center of the plate 2 so as to project a horizontal
beam 4, a vertical beam
4a, or a angled beam 4b (as shown in Figs 1, 2, 3) toward a target such as a
standing horizontal
ruler Sa which may be positioned on stands (not shown), or toward floor
targets Sd parallel
with, and alongside the vehicle, or towards floor target Sb which is
perpendicular to and
underneath the vehicle, or upwards towards an overhead suspended target Sc.
With each wheel's laser cooperatively aimed, the alignment can be determined
by measuring
the relative position of the respective laser dots. For example, if the
vehicle's factory stated track
(wheel spacing) is 60 inches and the lasers are 5 inches beyond the track on
each side but the
laser beams are 59 inches apart on a target close to the wheel, then a toe-in
of 1 inch exists at
target distance. If the target is a greater distance from the laser, then the
converging or diverging
effect of target distance from the laser is calculated according to that
distance and the state of the
wheel's alignment is thereby determined. The same applies for both toe and
camber
measurements.
In another embodiment alignment arms 2a are attached to plates 2 magnetically
or by other
means. In Figs 7, 8, 9 the arms Za are clamped to bars if which in turn are
attached to the rods
1. Clamp screw 2c allows arm 2a to move in cage ld while support 2b is set at,
or close to,
wheel center height and locked with thumb screw 2c thus allowing arm 2a to be
leveled
(according to level 12) and then clamped to bars if with thumb screws 2c.
Fig 17, 18 show the simplest embodiment comprising a single extension rod 1 to
be inserted
through wheel opening D' to contact rotor B with magnet la on the inboard end
and a laser
lamp 3 on the outboard end. Either end can be arranged with bearing means to
enable the laser 3
to rotate 3a in plane and beam its light 4a towards suitable targets such as
Sa, Sb, Sc and Sd in
Figs 1-3. The larger the diameter of magnet la the better, so as to bridge a
scored or grooved
rotor surface. This embodiment can also have an offset end as shown in Fig 4.
In Fig 18 the
rotor is shown without caliper E or wheel nuts for clarity.
Plate 2 may have ball feet (not shown) to allow easy positioning on ground G
and may be
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weighted after installed to prevent unwanted movement.
Of course all magnet attachments described above could be replaced by other
means such as
threaded fasteners, suction cups, clips, clamps, mechanical interlocks, and
the like.
Alignment arms 2a and their respective plates 2 could be a one piece assembly
such that the
assembly is attached to extension rods 1 in a horizontal or a vertical mode to
gauge the above
mentioned wheel/rotor alignment angles.
In another embodiment, the lasers 3 may be mounted on a rotatable degree dial
120 with
angular divisions 121 and a zero index mark 122 on alignment arm 2a. These
degree dial's
show zero angle when lasers 3 project their beam 110 perpendicularly and on to
each other's
lens 3a. When the gauge 120 is attached to the vehicle and a horizontal laser
dot deviation 11 is
present on targets 51, the degree dial 120 is rotated to bring the dot back
horizontally to center
(i.e., lens 3a) and the vehicle wheel's angle read from the dial markings. The
alignment arm
could also have its end section holding the laser 3 rotatable for centering
the dot in the vertical
plane. this end section could also have angular markings and an index mark to
read off the
vertical angle, or camber, of the wheel when the end is rotated to bring the
dot to its vertical
center.
It follows from the aforementioned disclosure that other surfaces that are
planar to the wheel
may be used with the present invention to check alignment, surfaces such as:
areas on the wheel
itself; the wheel's drive flange or hub; the wheel mounting studs or holes,
the drum brake drum,
these providing alignment reference with the wheels still on the vehicle, and,
providing working
clearance from the vehicle's bodywork for unobstructed gauging.
