It always pays to read the fine print. Sports team scrutinize the rules for opportunities to make new plays. Race teams look for ways to generate more downforce than their competitors, and patent attorneys look for loopholes in contracts.
It’s no different in trucking. Trucks have a weight limit of 80,000 pounds, but the regulations don’t distinguish between tractor, trailer and freight. Put more goodies in the cab – CB radio, coffee-maker and so on – and that’s less freight you can haul. Conversely, slim down the tractor and trailer and you can increase your payload. That reduces the transport cost per pound which means more profit, fewer truck journeys, or both. Just as in sports, you have to know the rules of lightweighting truck trailers and use them to your advantage.
Lightweighting truck trailers
The typical dry van trailer weighs around 15,000 pounds. Historically they’ve been built more for cheapness and durability than with weight in mind. That’s why you’ll see wooden floors and steel and cast iron components. However, there’s growing recognition that switching to lightweight materials can pay. There are three ways of lightweighting truck trailers:
- Substitute lighter, stronger materials.
- Integrate component design.
- Right-size assemblies and subsystems.
While cast iron weighs 450 lb/ft3 and steel 490 lb/ft3, aluminum comes in at just 169 lb/ft3. In absolute terms aluminum isn’t as strong, but its relative strength is higher. That lets aluminum substitute for steel in places like:
- Floor cross members
- Roof bows
- Sidewall posts
- Light-mounting boxes
- License-plate brackets
- Mud-flap hangers
An additional benefit of aluminum is that it’s naturally corrosion-resistant.
Alternatively, when strength is the priority, consider the new high strength steels being used by the automotive industry. Some are more than twice as strong, meaning you can use half as much.
A principle of “Design for Manufacturing” is to ask whether joined components need to come apart for maintenance or move relative to one another. If the answer is, “No,” the logical conclusion is to make them as one single piece. From a lightweighting perspective, this reduces the number of fasteners needed, and may allow other design changes that take out more weight.
An often overlooked approach is to use extruded material. Most grades of aluminum extrude readily and tooling is not expensive. With a little creativity it’s sometimes possible to combine several components into a single piece that’s manufactured as an extrusion.
Some tractor and trailer components are larger than needed for the type of service the vehicle will see. A prime example is fuel tanks. If a truck won’t travel more than say 300 miles in a day, why provide enough capacity for double? Not only will the tanks be bigger and heavier than needed, but the truck will be carrying more fuel.
Right-sizing is very much driven by the application. As metal fabricators we’re always happy to offer our thoughts on what might be possible. (And don’t overlook our expertise in alternative fuel fabrications!)
Fuel saving considerations
In passenger vehicles lightweighting is all about saving fuel. That’s not the case in trucks, with one important exception. Load the trailer with a low density product like breakfast cereal and the volume is filled before the weight limit is reached. In situations like those a lighter trailer means the truck doesn’t work as hard, and that reduces fuel consumption.
Have us take a look
If taking weight out of the things you make appeals talk to us. While we’re not experts in truck trailers we do know a lot about metals and metal fabrication. We can’t break any rules of physics, or even metallurgy, but we’ve studied the fine print and know what can be done. If you’re interested in substituting lighter materials or combining components ask us for ideas.