Meagan Daugherty

A roll-off subframe is an engineered frame design that is used to make non-roll-off bodies or equipment compatible with roll-off trucks. Sometimes called skids, rail frames and long rails, these structures are the base for whatever you want to haul with your roll-off truck. There are different subframe styles available, allowing you to choose the solution that fits your needs – some of those being a hooklift or combo style hookup. These types of subframes differ because they require more information from you, the buyer, in order to get the best fit for your hooklift style system.

When you purchase a roll-off truck with a hooklift system on it, there are certain rules that must be followed. One being that it is required to have a mechanism that will secure the container/subframe to the vehicle, shown below:

393.134 What are the rules for securing roll-on/roll-off or hook lift containers?

(a) Applicability. The rules in this section apply to the transportation of roll-on/roll-off or hook lift containers.

(b) Securement of a roll-on/roll-off and hook lift container. Each roll-on/roll-off and hook lift container carried on a vehicle which is not equipped with an integral securement system must be:

(1) Blocked against forward movement by the lifting device, stops, a combination of both or other suitable restraint mechanism;

(2) Secured to the front of the vehicle by the lifting device or other suitable restraint against lateral and vertical movement;

(3) Secured to the rear of the vehicle with at least one of the following mechanisms:

(i) One tiedown attached to both the vehicle chassis and the container chassis;

(ii) Two tiedowns installed lengthwise, each securing one side of the container to one of the vehicle’s side rails; or

(iii) Two hooks, or an equivalent mechanism, securing both sides of the container to the vehicle chassis at least as effectively as the tiedowns in the two previous items.

(Cornell Law School. 49 CFR § 393.134. law.cornell.edu)

A common mechanism on hooklift systems is commonly referred to in the roll-off industry as stops or hold-downs. These are highlighted and defined in section (b)(3)(iii). Most hooklift systems will already have stop hooks on the rails. When purchasing a subframe, you’ll need to relay those location measurements to the roll-off subframe manufacturer prior to purchase. Let’s look at how to properly measure your stop locations with two common stop styles: Inside and Outside Flat Bar.

More stop types that are seen on hooklift systems are Inside Bar, Inside Pocket, Inside Pins, Inside Angle, and Outside Tubing. Regardless of your stop style, there will be these three measurements needed to properly locate stops for your containers

1. Back of the arm to the center of the rear roller

2. Back of the arm to the center of the stop/hold-down

3. Bottom of the long rail to the stop/hold-down

Ready to order a subframe? Here are five simple tips to keep in mind:

1. Know your hooklift system model information – Sometimes subframe manufacturers have dealt with that model and already know the proper measurements, however, don’t rely on that alone as some may have several different options that will need to be confirmed. It is always best to measure yourself for the best possible outcome.

2. Use an accurate tape measure

3. Measure in inches

4. If there have been any modifications done to your hoist system, please be sure to let the subframe manufacturer know. Certain modifications may affect the stop locations.

5. Review the sales order before you sign off – Be sure to review based on your measurements and let them know if anything is incorrect before the subframe is built and let the sales representative know if any changes need to be made.

Following the three required measurements and the five tips above, you can get your stop locations right the first time. This will also help avoid having to make time to complete unnecessary modifications and adjustments both for you and the subframe manufacturer. Be on the lookout for an upcoming article about how to measure the hook height and pin measurements.