Gross weight of towed vehicle (pounds)1 | Longitudinal strength in tension and compression2 | ||
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)2 3 | |
Pounds | |||
Less than 5,000 | 3,000 | 6,500 | 3,000 |
5,000 and over | |||
Less than 10,000 | 6,000 | (1) | (1) |
10,000 and over | |||
Less than 15,000 | 9,000 | (1) | (1) |
1 The required strength of tow-bars for towed vehicles of 15,000 pounds and over gross weight and of new tow-bars acquired and used after Sept. 30, 1948, for towed vehicles of 5,000 pounds and over gross weight shall be computed by means of the following formulae: Longitudinal strength = gross weight of towed vehicle * 1.3. Strength as a beam = gross weight of towed vehicle * 0.6.
2 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.
3 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 trailers.
This tow-bar complies with the requirements of the Federal Motor Carrier Safety 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.
Diameter of U-Bolts in Inches
Weight in pounds of heaviest towed vehicle | Double or triple saddle-mount | |||
Front mount | Middle or front mount | Rear mount | Single saddle-mount1 | |
Up to 5,000 | 0.625 | 0.5625 | 0.500 | 0.500 |
5,000 and over | 0.6875 | 0.625 | 0.5625 | 0.5625 |
1 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.
Total Cross-Sectional Area of U-Bolts in Square Inches
Weight in pounds of heaviest towed vehicle | Double or triple saddle-mount | |||
Front mount | Middle or front mount | Rear mount | Single saddle-mount1 | |
Up to 5,000 | 1.2 | 1.0 | 0.8 | 0.8 |
5,000 and over | 1.4 | 1.2 | 1.0 | 1.0 |
1 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.
Minimum Test Load in Pounds
Weight in pounds of heaviest towed vehicle | Double or triple saddle-mount | |||
Front mount | Middle or front mount | Rear mount | Single saddle-mount1 | |
Up to 5,000 | 15,000 | 10,000 | 5,000 | 5,000 |
5,000 and over | 30,000 | 20,000 | 10,000 | 10,000 |
1 The total weight of all the vehicles being towed shall govern.
Diameter of Solid Kingpin in Inches
Weight in pounds of heaviest towed vehicle | Double or triple saddle-mount | |||||||
Front mount | Middle or front mount | Rear mount | Single saddle-mount1 | |||||
Mild steel | H.T.S.2 | Mild steel | H.T.S.2 | Mild steel | H.T.S.2 | Mild steel | H.T.S. | |
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.
This saddle-mount complies with the requirements of the Federal Motor Carrier Safety Administration for vehicles up to 5,000 pounds (or over 5,000 pounds):
Manufactured________________________
(Month and year)
by________________________
(Name of manufacturer)
[1] See footnote 1 to § 393.24(c) .
49 C.F.R. §393.71