Address the body and equipment before selecting a chassis

Many people start the specification-writing process with the truck chassis, when it is actually most logical to address the body and equipment first. Think about it. An effective, productive work truck is designed to perform a specific job or series of jobs. Therefore, it makes sense to start the process by defining the job or jobs the truck will perform. From there, you can address the equipment and associated truck body needed to perform those tasks. Finalizing the body and equipment will define the vehicle's required payload, necessary clear cab to axle chassis length and the loaded body's center of gravity. This information enables you to select an appropriately sized chassis and perform an accurate weight distribution and payload analysis to determine the appropriate chassis. Finish by choosing the powertrain that meets your performance criteria.

Avoid just doing what you have always done

You're replacing an existing vehicle, so you figure all you have to do is duplicate the old unit. Not so fast. For starters, the current vehicle may not have been optimized for the job it is doing. In such a case, the end users probably figured out how to make it work as well as they could, but that does not mean you shouldn't improve the new unit. Even if the vehicle was properly spec'd at the time it was initially acquired, MTO requirements change (SPIF) and new/ improved products are constantly being introduced. It is possible that there is a new body, chassis or piece of equipment that would offer significant improvements over what was previously available.

Perform weight distributions and calculations

After the preliminary selection of a suitable chassis has been made, perform a detailed weight distribution analysis to determine individual axle loadings. When necessary, optional axles, suspension components and frames may be required to ensure that the chassis is not overloaded and all equipment-mounting requirements have been met. Once the correct foundation components have been selected, it is time to move on to the powertrain (engine, transmission, axle ratio, etc.) and other components such as the electrical system, fuel tanks and cab content. All of these components have an impact on the completed vehicle's overall performance and productivity, so it is important to make selections based on valid requirements.

In far too many cases, vocational truck designers make powertrain selections based on guesses instead of a careful analysis of horsepower and engine torque demands. Start by defining your performance criteria (road speed, starting gradeability, reserve gradeability, etc.) and then calculate your actual requirements. This will allow you to select the proper engine, transmission and axle ratio to ensure that the truck performs as required. The payoff in this process is a truck that has better fuel economy and lower maintenance costs.

Writing a Spec that meets your requirements

Designing an integrated work truck requires that you understand your requirements before starting the design process. DEL Equipment is equipped with knowledgeable sales and engineering staff that is available should you require any assistance.  If you take the time to consider the above, you will be rewarded with a more productive, cost-effective vehicle.

Written by : Steve Schira, Key Account Manager