Current through Register Vol. 48, No. 9, September 27, 2024
(a) Number in
combination.
(1) No more than three saddle
mounts may be used in any combination.
(2) No more than one tow bar may be used in
any combination.
(3) When motor
vehicles are towed by means of triple saddle mounts, the towed vehicles shall
have brakes acting on all wheels which are in contact with the
roadway.
(b) Carrying
vehicles on towing vehicle.
(1) When
adequately and securely attached by means equivalent in security to that
provided in paragraph (j)(2), a motor vehicle or motor vehicles may be full
mounted on the structure of a towing vehicle engaged in any driveaway towaway
operation.
(2) No motor vehicle or
motor vehicles may be full mounted on a towing vehicle unless the relationship
of such full mounted vehicles to the rear axle or axles results in proper
distribution of the total gross weight of the vehicles and does not unduly
interfere with the steering, braking, or maneuvering of the towing vehicle, or
otherwise contribute to the unsafe operation of the vehicles comprising the
combination.
(c)
Carrying vehicles on towed vehicles.
(1) When
adequately and securely attached by means equivalent in security to that
provided in paragraph (j)(2), a motor vehicle or motor vehicles may be full
mounted on the structure of towed vehicles engaged in any driveaway towaway
operation.
(2) No motor vehicle
shall be full mounted on a motor vehicle towed by means of a tow bar unless the
towed vehicle is equipped with brakes and is provided with means for effective
application of brakes acting on all wheels and is towed on its own
wheels.
(3) No motor vehicle or
motor vehicles shall be full mounted on a motor vehicle towed by means of a
saddle mount unless the center line of the kingpin or equivalent means of
attachment of such towed vehicle shall be so located on the towing vehicle that
the relationship to the rear axle or axles results in proper distribution of
the total gross weight of the vehicles and does not unduly interfere with the
steering, braking, or maneuvering of the towing vehicle or otherwise contribute
to the unsafe operation of vehicles comprising the combination; and unless a
perpendicular to the ground from the center of gravity of the full mounted
vehicles lies forward of the center line of the rear axle of the saddle mounted
vehicle.
(4) If a motor vehicle
towed by means of a double saddle mount has any vehicle full mounted on it,
such saddle mounted vehicle shall at all times while so loaded have effective
brakes acting on those wheels which are in contact with the roadway.
(d) Bumper tow bars on heavy
vehicles prohibited. Tow bars of the type which depend upon the bumpers as a
means of transmitting forces between the vehicles shall not be used to tow a
motor vehicle weighing more than 5,000 pounds.
(e) Front wheels of saddle mounted vehicles
restrained. A motor vehicle towed by means of a saddle mount shall have the
motion of the front wheels restrained if under any condition of turning of such
wheels they will project beyond the widest part of either the towed or towing
vehicle.
(f) Vehicles to be towed
in forward position. Unless the steering mechanism is adequately locked in a
straight forward position, all motor vehicles towed by means of a saddle mount
shall be towed with the front end mounted on the towing vehicle.
(g) Means required for towing.
(1) No motor vehicle or motor vehicles shall
be towed in driveaway towaway operations by means other than tow bar or saddle
mount connections which shall meet the requirements.
(2) For the purpose of the regulations of
38-382:
(i) Coupling devices such as those
used for towing house trailers and employing ball and socket connections shall
be considered as tow bars.
(ii)
Motor vehicles or parts of motor vehicles adequately, securely, and rigidly
attached by devices meeting the requirements of paragraph (n) shall be
considered as one vehicle in any position in any combination.
(h) Requirements for
tow bars. Tow bars shall comply with the following requirements:
(1) Tow bars, structural adequacy and
mounting. Every tow bar shall be structurally adequate and properly installed
and maintained. To insure that it is structurally adequate, it must, at least,
meet the requirements of the following table:
Longitudinal strength in tension and comparison
[FN2]
|
Gross weight of towed vehicle (pounds)
[FN1]
|
All tow'bars
|
New tow-bars acquired and used by a motor
carrier after Sept. 30, 1948
|
Strength as a beam (in any direction
concentrated load at center) [FN2], [FN3]
|
Pounds
|
Less than 5,000 ....
|
3,000
|
6,500
|
3,000
|
5,000 and over .....
|
|
Less than 10,000 ...
|
6,000
|
[FN1]
|
[FN1]
|
10,000 and over ....
|
|
Less than 15,000 ...
|
9,000
|
[FN1]
|
[FN1]
|
[FN1] The required strength of tow-bars for
towed vehicles of 15,000 pounds and over gross weight and of new towbars
acquired and used after Sept. 30, 1948, for towed vehicles of 5,000(1) pounds
and over gross weight shall be computed by means of the following formulae:
Longitudinal strength = gross weight of towed vehicle x 1.3. Strength as a beam
= gross weight of towed vehicle x 0.6.
|
[FN2] In testing, the whole unit shall be
tested with all clamps, joints, and pins so mounted and fastened as to
approximate conditions of actual operation.
|
[FN3] This test shall be applicable only to
tow-bars which are, in normal operation, subjected to a bending movement such
as tow-bars for house trailer.
|
(2) Tow bars, jointed. The tow bar shall be
so constructed as to freely permit motion in both horizontal and vertical
planes between the towed and towing vehicles. The means used to provide the
motion shall be such as to prohibit the transmission of stresses under normal
operation between the towed and towing vehicles, except along the longitudinal
axis of the tongue or tongues.
(3)
Tow bar fastenings. The means used to transmit the stresses to the chassis or
frames of the towed and towing vehicles may be either temporary structures or
bumpers or other integral parts of the vehicles: Provided, however, that the
means used shall be so constructed, installed, and maintained that when tested
as an assembly, failure in such members shall not occur when the weakest new
tow bar which is permissible under paragraph (h)(1) is subjected to the tests
given therein.
(4) Means of
adjusting length. On tow bars, adjustable as to length, the means used to make
such adjustment shall fit tightly and not result in any slackness or permit the
tow bar to bend. With the tow bar supported rigidly at both ends and with a
load of 50 pounds at the center, the sag, measured at the center, in any
direction shall not exceed 0.25 inch under any condition of adjustment as to
length.
(5) Method of clamping.
Adequate means shall be provided for securely fastening the tow bar to the
towed and towing vehicles.
(6) Tow
bar connection to steering mechanism. The tow bar shall be provided with
suitable means of attachment to and actuation of the steering mechanism, if
any, of the towed vehicle. The attachment shall provide for sufficient
angularity of movement of the front wheels of the towed vehicle so that it may
follow substantially in the path of the towing vehicle without cramping the tow
bar. The tow bar shall be provided with suitable joints to permit such
movement.
(7) Tracking. The tow bar
shall be so designed, constructed, maintained, and mounted as to cause the
towed vehicle to follow substantially in the path of the towing vehicle. Tow
bars of such design on in our condition as to permit the towed vehicle to
deviate more than 3 inches to either side of the path of a towing vehicle
moving in a straight line as measured from the center of the towing vehicle are
prohibited.
(8) Passenger car
trailer type couplings. Trailer couplings used for driveaway towaway operations
of passenger car trailers shall conform to Society of Automotive Engineers
Standard No. J684c, "Trailer Couplings and Hitches Automotive Type," July 1970.
[FN1]
(9) Marking tow bars. Every
tow bar acquired and used in driveaway towaway operations by a motor carrier
shall be plainly marked with the following certification of the manufacturer
thereof (or words of equivalent meaning):
This tow bar complies with the requirements of the
Federal Highway Administration for (maximum gross weight for which tow bar is
manufactured) vehicles.
Allowable Maximum Gross Weight ___
Manufactured
_____________________________________________
(month and year)
by
____________________________________________________________
(name of manufacturer)
Tow bar certification manufactured before the effective
date of this regulation must meet requirements in effect at the time of
manufacture.
(10) Safety
devices in case of tow bar failure or disconnection.
(i) The towed vehicle shall be connected to
the towing vehicle by a safety device to prevent the towed vehicle from
breaking loose in the event the tow bar fails or becomes disconnected. When
safety chains or cables are used as the safety device for that vehicle, at
least two safety chains or cables meeting the requirements of paragraph
(h)(10)(ii) shall be used. The tensile strength of the safety device and the
means of attachment to the vehicles shall be at least equivalent to the
corresponding longitudinal strength for tow bars required in the table of
paragraph (h)(1). If safety chains or cables are used as the safety device, the
required strength shall be the combined strength of the combination of chains
and cables.
(ii) If chains or
cables are used as the safety device, they shall be crossed and attached to the
vehicles near the points of bumper attachments to the chassis of the vehicles.
The length of chain used shall be no more than necessary to permit free turning
of the vehicles. The chains shall be attached to the tow bar at the point of
crossing or as close to that point as is practicable.
(iii) A safety device other than safety
chains or cables must provide strength, security of attachment, and directional
stability equal to, or greater than, that provided by safety chains or cables
installed in accordance with paragraph (h)(10)(ii). A safety device other than
safety chains or cables must be designed, constructed, and installed so that,
if the tow bar fails or becomes disconnected, the tow bar will not drop to the
ground.
(j) Requirements for
upper half of saddle mounts. The upper half of any saddle mount shall comply
with the following requirements:
(1) Upper
half connection to towed vehicle. The upper half shall be securely attached to
the frame or axle of the towed vehicle by means of U bolts or other means
providing at least equivalent security.
(2) U bolts or other attachments. U bolts
used to attach the upper half to the towed vehicle shall be made of steel rod,
free of defects, so shaped as to avoid at any point a radius of less than 1
inch: Provided, however, That a lesser radius may be utilized if the U bolt is
so fabricated as not to cause more than 5 percent reduction in cross sectional
area at points of curvature, in which latter event the minimum radius shall be
one sixteenth inch. U bolts shall have a diameter not less than required by the
following table:
DIAMETER OF U-BOLTS IN INCHES
|
Weights in pounds of heaviest towed
vehicle
|
Double or triple saddle mount
|
Front mount
|
Middle or front mount
|
Rear mount
|
Single sadd le-mount
[FN1]
|
Up to 5,000 ........
|
0.625
|
0.5625
|
0.0500
|
0.500
|
5,000 and over .....
|
0.6875
|
0.625
|
0.5625
|
0.5625
|
[FN1] The total weight of all the vehicles
being towed shall govern. If other devices are used to accomplish the same
purposes as U bolts they shall have at least equivalent strength of U bolts
made of mild steel. Cast iron shall not be used for clamps or any other holding
devices.
|
(3) U bolts and points of support, location.
The distance between the most widely separated U bolts shall not be less than 9
inches. The distance between the widely separated points where the upper half
supports the towed vehicle shall not be less than 9 inches, except that saddle
mounts employing ball and socket joints shall employ a device which clamps the
axle of the towed vehicle throughout a length of not less than 5
inches.
(4) Cradle type upper
halves, specifications. Upper halves of the cradle type using vertical members
to restrain the towed vehicle from relative movement in the direction of motion
of the vehicles shall be substantially constructed and adequate for the
purpose. Such cradle mounts shall be equipped with at least one bolt or
equivalent means to provide against relative vertical movement between the
upper half and the towed vehicle. Bolts, if used, shall be at least one half
inch in diameter. Devices using equivalent means shall have at least equivalent
strength. The means used to provide against relative vertical motion between
the upper half and the towed vehicle shall be such as not to permit a relative
motion of over one half inch. The distance between the most widely separated
points of support between the upper half and the towed vehicle shall be at
least 9 inches.
(5) Lateral
movement of towed vehicle.
(i) Towed vehicles
having a straight axle or an axle having a drop of less than 3 inches, unless
the saddle mount is constructed in accordance with paragraph (m)(2), shall be
securely fastened by means of chains or cables to the upper half so as to
insure against relative lateral motion between the towed vehicle and the upper
half. The chains or cables shall be at least 3/16 inch diameter and secured by
bolts of at least equal diameter.
(ii) Towed vehicles with an axle with a drop
of 3 inches or more, or connected by a saddle mount constructed in accordance
with paragraph (m)(2), need not be restrained by chains or cables provided that
the upper half is so designed as to provide against such relative
motion.
(iii) Chains or cables
shall not be required if the upper half is so designed as positively to provide
against lateral movement of the axle.
(k) Requirements for lower half of saddle
mounts. The lower half of any saddle mount shall comply with the following
requirements:
(1) Ubolts or other attachments.
U bolts used to attach the lower half to the towing vehicle shall be made of
steel rod, free of defects, so shaped as to avoid at any point a radius of less
than 1 inch: Provided, however, That a lesser radius may be utilized if the U
bolt is so fabricated as not to cause more than 5 percent reduction in cross
sectional area at points of curvature, in which latter event the minimum radius
shall be one sixteenth inch. U bolts shall have a total cross sectional area
not less than as required by the following table:
Total Cross-Sectional Area of U-Bolts in Square
Inches
|
Weights in pounds of heaviest towed
vehicle
|
Double or triple saddle mount
|
Front mount
|
Middle or front mount
|
Rear mount
|
Single sadd le'mount
[FN1]
|
UP TO 5,000 ............
|
1.2
|
1.0
|
0.8
|
0.8
|
5,000 and over .........
|
1.4
|
1.2
|
1.0
|
1.0
|
[FN1] The total weight of all the vehicles
being towed shall govern. If other devices are used to accomplish the same
purposes as U bolts they shall have at least equivalent strength of U bolts
made of mild steel. Cast iron shall not be used for clamps or any other holding
devices.
|
(2) Shifting. Adequate provision shall be
made by design and installation to provide against relative movement between
the lower half and the towing vehicle especially during periods of rapid
acceleration and deceleration. To insure against shifting, designs of the
tripod type shall be equipped with adequate and securely fastened hold back
chains or similar devices.
(3)
Swaying.
(i) Adequate provision shall be made
by design and installation to provide against swaying or lateral movement of
the towed vehicle relative to the towing vehicle. To insure against swaying,
lower halves designed with cross members attached to but separable from
vertical members shall have such cross members fastened to the vertical members
by at least two bolts on each side. Such bolts shall be of at least equivalent
cross sectional area as those required for U bolts for the corresponding saddle
mount as given in the table in paragraph (k)(1). The minimum distance between
the most widely separated points of support of the cross member by the vertical
member shall be three inches as measured in a direction parallel to the
longitudinal axis of the towing vehicle.
(ii) The lower half shall have a bearing
surface on the frame of the towing vehicle of such dimensions that the pressure
exerted by the lower half upon the frame of the towing vehicle shall not exceed
200 pounds per square inch under any conditions of static loading. Hardwood
blocks or blocks of other suitable material, such as hard rubber, aluminum or
brakelining, if used between the lower half and the frame of the towing vehicle
shall be at least 1/2 inch thick, 3 inches wide, and a combined length of 6
inches.
(iii) Under no condition
shall the highest point of support of the towed vehicle by the upper half be
more than 24 inches, measured vertically, above the top of the frame of the
towing vehicle, measured at the point where the lower half rests on the towing
vehicle.
(4) Wood
blocks.
(i) Hardwood blocks of good quality
may be used to build up the height of the front end of the towed vehicle,
provided that the total height of such wood blocks shall not exceed 8 inches
and not over two separate pieces are placed upon each other to obtain such
height; however, hardwood blocks, not over 4 in number, to a total height not
to exceed 14 inches, may be used if the total cross sectional area of the U
bolts used to attach the lower half of the towing vehicle is at least 50
percent greater than that required by the table contained in paragraph (k)(1),
or, if other devices are used in lieu of U bolts, they shall provide for as
great a resistance to bending as is provided by the larger U bolts above
prescribed.
(ii) Hardwood blocks
must be at least 4 inches in width and the surfaces between blocks or block and
lower half or block and upper half shall be planed and so installed and
maintained as to minimize any tendency of the towed vehicle to sway or
rock.
(5) Cross member,
general requirements. The cross member, which is that part of the lower half
used to distribute the weight of the towed vehicle equally to each member of
the frame of the towing vehicle, if used, shall be structurally adequate and
properly installed and maintained adequately to perform this
function.
(6) Cross member, use of
wood. No materials, other than suitable metals, shall be used as the cross
member, and wood may not be used structurally in any manner that will result in
its being subject to tensile stresses. Wood may be used in cross members if
supported throughout its length by suitable metal cross members.
(7) Lower half strength. The lower half shall
be capable of supporting the loads given in the following table. For the
purpose of test, the saddle mount shall be mounted as normally operated and the
load applied through the upper half:
MINIMUM TEST LOAD IN POUNDS
|
Weights in pounds of Double or triple saddle
mount heaviest towed vehicle
|
Front mount
|
Middle or front mount
|
Rear mount
|
Single sadd le-mount
[FN1]
|
UP TO 5,000 .........
|
15,000
|
10,000
|
5,000
|
5,000
|
5,000 and over ......
|
30,000
|
20,000
|
10,000
|
10,000
|
[FN1] The total weight of all the vehicles
being towed shall govern.
|
(l) Requirements for kingpins of saddle
mounts. The kingpin of any saddle mount shall comply with the following
requirements:
(1) Kingpin size.
(i) Kingpins shall be constructed of steel
suitable for the purpose, free of defects, and having a diameter not less than
required by the following table:
WIDETABLE
|
NOTE--Some parts of this form are wider than
one screen. To view material that exceeds the width of this screen, use the
right arrow
key. To return to the original screen, use the
left arrow key.
|
DIAMETER OF SOLID KINGPIN IN INCHES
|
Double or triple saddle mount
|
Weights in pounds of heaviest towed
vehicle
|
Front mount
|
Middle or front mount
|
Rear mount
|
Single saddle-mount 1
|
Mild steel
|
H.T.S.2 Mild
|
steel
|
H.T.S.2 Mild
|
H.T.S.2 Mild
|
steel
|
H.T.S.2
steel
|
UP TO 5,000 ...
|
1.125
|
1.000
|
1.000
|
0.875
|
0.875
|
0.750
|
0.875
|
0.750
|
5,000 and over ....
|
1.500
|
1.125
|
1.250
|
1.000
|
1.000
|
0.875
|
1.000
|
0.875
|
1 The total weight of all the vehicles being
towed shall govern.
|
2 High tensile steel is steel having a minimum
ultimate strength of 65,000 pounds per square inch.
|
(ii) If a ball and socket joint is used in
place of a kingpin, the diameter of the neck of the ball shall be at least
equal to the diameter of the corresponding solid kingpin given in the above
table. If hollow kingpins are used, the metallic cross sectional area shall be
at least equal to the cross sectional area of the corresponding solid
kingpin.
(2) Kingpin
fit. If a kingpin bushing is not used, the king pin shall fit snugly into the
upper and lower halves but shall not bind. Those portions of the upper or lower
halves in moving contact with the kingpin shall be smoothly machined with no
rough or sharp edges. The bearing surface thus provided shall not be less in
depth than the radius of the kingpin.
(3) Kingpin bushing on saddle mounts. The
kingpin of all new saddle mounts acquired and used shall be snugly enclosed in
a bushing at least along such length of the kingpin as may be in moving contact
with either the upper or lower halves. The bearing surface thus provided shall
not be less in depth than the radius of the kingpin.
(4) Kingpin to restrain vertical motion. The
kingpin shall be so designed and installed as to restrain the upper half from
moving in a vertical direction relative to the lower half.
(m) Additional requirements for saddle
mounts. Saddle mounts shall comply with the following requirements:
(1) Bearing surface between upper and lower
halves. The upper and lower halves shall be so constructed and connected that
the bearing surface between the two halves shall not be less than 16 square
inches under any conditions of angularity between the towing and towed
vehicles: Provided, however, That saddle mounts using a ball and socket joint
shall have a ball of such dimension that the static bearing load shall not
exceed 800 pounds per square inch, based on the projected cross sectional area
of the ball: And further provided, That saddle mounts having the upper half
supported by ball, taper, or roller bearings shall not have such bearings
loaded beyond the limits prescribed for such bearings by the manufacturer
thereof. The upper half shall rest evenly and smoothly upon the lower half and
the contact surfaces shall be lubricated and maintained so that there shall be
a minimum of frictional resistance between the parts.
(2) Saddle mounts, angularity. All saddle
mounts acquired and used shall provide for angularity between the towing and
towed vehicles due to vertical curvatures of the highway. Such means shall not
depend upon either the looseness or deformation of the parts of either the
saddle mount or the vehicles to provide for such angularity.
(3) Tracking. The saddle mount shall be so
designed, constructed, maintained, and installed that the towed vehicle or
vehicles will follow substantially in the path of the towing vehicle without
swerving. Towed vehicles shall not deviate more than 3 inches to either side of
the path of the towing vehicle when moving in a straight line.
(4) Prevention of frame bending. Where
necessary, provision shall be made to prevent the bending of the frame of the
towing vehicle by insertion of suitable blocks inside the frame channel to
prevent kinking. The saddle mount shall not be so located as to cause
deformation of the frame by reason of cantilever action.
(5) Extension of frame. No saddle mount shall
be located at a point to the rear of the frame of a towing vehicle.
(6) Nuts, secured. All nuts used on bolts, U
bolts, king pins, or in any other part of the saddle mount shall be secured
against accidental disconnection by means of cotter keys, lock washers, double
nuts, safety nuts, or equivalent means. Parts shall be so designed and
installed that nuts shall be fully engaged.
(7) Inspection of all parts. The saddle mount
shall be so designed that it may be disassembled and each separate part
inspected for worn, bent, cracked, broken, or missing parts.
(8) Saddle mounts, marking. Every new saddle
mount acquired and used in driveaway towaway operations by a motor carrier
shall have the upper half and the lower half separately marked with the
following certification of the manufacturer thereof (or words of equivalent
meaning).
This saddle mount complies with the requirements of the
Federal Highway Administration for vehicles up to 5,000 pounds (or over 5,000
pounds):
Manufactured
_____________________________________________
(month and year)
by
____________________________________________________________
(name of manufacturer)
(n) Requirements for devices used to connect
motor vehicles or parts of motor vehicles together to form one vehicle
(1) Front axle attachment. The front axle of
one motor vehicle intended to be coupled with another vehicle as defined in
paragraph (g)(2)(ii) shall be attached with U bolts meeting the requirements of
paragraph (j)(2).
(2) Rear axle
attachment. The rear axle of one vehicle shall be coupled to the frame of the
other vehicle by means of a connecting device which when in place forms a
rectangle. The device shall be composed of two pieces, top and bottom. The
device shall be made of 4 inch by 1/2 inch steel bar bent to shape and shall
have the corners reinforced with a plate at least 3 inches by 1/2 inch by 8
inches long. The device shall be bolted together with 3/4 inch bolts and at
least three shall be used on each side. Wood may be used as spacers to keep the
frames apart and it shall be at least 4 inches square.
[FN1] "Pursuant to direction of the South Carolina
Legislative Council, this footnote 1 refers to note 1 following the table in
(h)(1), ante."