Calculating the Load on a Slip-On Tank Fire Engine
This calculator was developed to estimate the total load on a slip-on fire truck
prior to fabrication. It requires the input of accurate information that you, the
designer, must obtain. Your reward for doing your "homework" will be the reduction
of costly design errors and the likelihood of a well balanced truck. You will need
to enter good numbers into the calculator. This discussion will help you determine
The vehicle manufacturer or dealer can provide you with the pick-up truck's Gross
Vehicle Weight Rating (GVWR) and each Gross Axle Weight Rating (GAWR). This information
is often found on a data plate on a door or door jam. Military vehicles will have
this data on a dash plate.
Bare Chassis Weights and Wheelbase
This section asks for three items that are necessary for the calculations. Determine
the bare truck weight by filling the truck full of fuel and taking the vehicle to
a set of scales. Without occupants, weigh the vehicle to get a total weight and the
weight on the rear axle. Also enter the wheelbase. You may refer to REC’s Weights
of Common Componentsfor calculating your load. Estimates include weights of water
tanks, pumps, winches, and various other items.
Behind the Front Axle
In this section, you will enter weights of major objects that you place in the vehicle.
Estimate the horizontal distance between the object’s CG and the center line of the
front axle. Refer to REC’s Center of Gravity Diagram for assistance.
Important: This Detailed Calculator - Pickup Truck Slip On Units is a simplified
version of our Detailed Calculator - Truck Chassis > 14,000 GVWR. This calculator
only considers adding items that will be located behind the front axle. If your slip-on
unit will have components added in front of the front axle, please use the Detailed
Calculator - Truck Chassis > 14,000 GVWR.
After verifying that your entries are correct, click the "Calculate" button. The
estimated weight of the completed truck and the weight on each axle will appear.
The results will also display the estimated percentage of the weight on each axle
and the percentage of the payload on each axle. A dialog box will give a general
statement of what the results mean. It might recommend that you make some changes.
Use "Reset" to start over.
Considerable effort has been made to make this calculator accurate and easy to use.
The more accurate information you enter, the more accurate your estimate will be.
It is your responsibility to determine the accuracy of the results. Your final check
for accuracy should be to weigh the completed vehicle with a full load of occupants,
water, fuel, and equipment to verify that it does not exceed the manufacturer’s GVWR
Tips & FAQs
Please refer to Tips & FAQs for more information about the calculator.
User's Pledge: I have read the instructions and understand that the calculator’s
accuracy depends on my understanding of vehicle design principles and accurate input
of the data requested. The interpretation of the results and decisions about their
accuracy are my responsibility. By clicking the calculator link below, I accept this