Md. Code Regs. 11.13.08.04

Current through Register Vol. 51, No. 22, November 1, 2024

Section 11.13.08.04 - Light Service Devices and Systems

A. These systems are for use with trailers having a gross vehicle weight rating of 10,000 pounds or less. This includes, but is not limited to such types as the utility, boat, camping, travel, and other trailers which are normally towed by the conventional passenger car, or similarly constructed vehicle, or light-duty truck. This regulation is intended basically for the ball-and-socket type of primary connecting system, but does include the fifth wheel and pintle hook-type system when used on vehicles subject to this regulation.

B. Trailer Classification.

(1) Class 1-----Trailers, with a gross weight not exceeding 2,000 pounds.

(2) Class 2-----Trailers, with a gross weight over 2,000 pounds, but not exceeding 3,500 pounds.

(3) Class 3-----Trailers, with a gross weight over 3,500 pounds, but not exceeding 5,000 pounds.

(4) Class 4-----Trailers, with a gross weight over 5,000 pounds, but not exceeding 10,000 pounds.

C. Couplings.

(1) Coupling Classification. There shall be four major strength classifications, or designations of couplings. The designation shall be based on the maximum gross trailer weight (MGTW) the coupling is qualified to tow. The No. 1 couplings shall be used for towing Class 1 trailers; No. 2 couplings for Class 2 or smaller trailers; No. 3 couplings for Class 3 or smaller trailers; and No. 4 couplings for Class 4 or small trailers. This is not intended to limit the number or variety of couplings in a given class, or designation.

(2) Coupling Ultimate Strength. Each coupling and hitch ball, when subjected to static bench tests in a rigid, non-yielding test fixture, shall withstand the test loads specified in Table 1 without incurring failure. For purposes of this regulation, failure occurs at the point at which the coupling or ball will accept no additional test load.

(3) Coupling and Hitch Ball Test Procedure. A new coupling or ball shall be used for each mode of load application. Each type of test load is to be applied individually to one component at a time, utilizing a non-yielding test fixture similar in design to the typical test fixture illustrated in Figure 1. When testing a coupling, a hardened ball shall be used. When testing a ball, a hardened coupling shall be used.

(4) Attachment of Couplings. Each coupling is to be mounted to the trailer attaching member by bolting, welding, or riveting in such manner that the towing loads are safely and adequately transferred to that member.

(5) Provisions for Safety.

(a) Each coupling, regardless of classification, or designation, shall be equipped with a manually operated mechanism so adapted as to prevent disengagement of the unit while in operation. In addition to this positive locking mechanism, the coupling shall be so designed that the trailer can be disconnected from the towing vehicle regardless of the angle of the trailer to the towing vehicle.

(b) Each hitch ball shall be equipped and installed with a lock washer or equivalent device and each replacement hitch ball shall be marketed with a lock washer or equivalent device with instructions as to proper installation provided by the responsible manufacturer.

Md. Code Regs. 11.13.08.04