1 Front Wall

What you spec will depend on the severity of your application. Lift trucks banging against the front of the trailer can end up making the trailer look a little pregnant. If you are loading in a lot of different places you likely won’t have much control over the practices of the forklift drivers so it would be best to spec a little bit extra up front. Spec more and deeper posts for more strength. You can also spec’ 1/2″ vs 1/4″ plywood for more resistance. Adding a steel bulkhead will protect the area between the posts.

2 Roof

The standard roof today is .040 inch aluminum material. The roof should be drum-tight and bonded securely to the roof bolts. Chemlite, a translucent roof, is popular for light-duty but can tear at high speed if there’s a small hole in it. For LTL operations, the translucent roof is becoming more popular for its visibility when there’s not sufficient lighting. That could be a big factor if your staff had to be able to read labels inside, but not a good spec if you wanted to backhaul watermelons from the southern U.S., due to heat gain. Also, if it’s an application where the load reaches the top of the unit or the forklift is being used, you may want plywood to cover the inside roof bows or at least have anti-snag roof bows.

3 Sidewalls

It’s a compromise between interior width for extra space and a heavier sidewall for strength. Thinner materials will wrinkle and tear more easily allowing the rivets to work free. For extra support, spec vans with extra posts over the upper coupler and landing gear. If you’re hand-loading and using very gentle loading procedures, you don’t need a scuffliner. But if you know you have people that are very rough, or if you know you are loading products that have sharp edges, such as metal baskets then you have to design the trailer to handle the abuse. If you don’t have the proper heavy-duty scuffliner, it will slice right through your walls and destroy the trailer. Corrugated steel is more or less the standard, 16- or 18-gauge. Hardwood and plastic may take some inside width away but they are both very good at impact resistance. For light duty, galvanized steel or aluminum scuff plate is the most popular.

4 Logistic Posts

Many more trailers are being built with logistic posts. Standard is hat shape, if there’s no need to tie down the freight. Plastic inserts on the logistic posts make for a plastic wall section that snaps in between the logistic posts so you don’t have wood that can splinter on the sides and tear bagged loads.

5 Doors

The basic door setup is 4 hinges, with one lock bar per door. For highway use, the doors should be the swing, barn door type. For city operations, roll-up doors are the best option. For rail operations, a 1 1/4″ door is more acceptable. For durability, there are FRP doors with a stiffener. In terms of the hinges, the steel type will bend but likely not break if the door is hit. However, that can also damage the doors. Sometimes it’s better to just have the door break off totally and fall on the ground and then just replace the hinges. Aluminum hinges are better at breaking off when the door is hit.

6 Rear impact guard

Trailers are built with certified rear underguards that meet certain impact standards. For driver safety, traction on the crossbar is important if drivers have to climb in and out of the trailer. Using a galvanized rear door frame and bumper will also get rid of any possible rust problems at the rear end and it’s good for longevity because the zinc sacrifices itself to protect all the fasteners nearby.

7 Landing gear

Properly spec’ing landing gear requires an understanding of the loads the trailer will be expected to hold. If it’s quite a heavily loaded trailer, you have to make sure your landing gear support is strong enough, which could mean extra crossmembers. Generally, you need a 50,000-pound static weight, over 5-6 crossmembers evenly spaced 12′ from the front of the trailer. If you’re under a really heavy-duty operation you can spec heavier landing gear. A coupler up front is important.

8 Wiring/Lighting

The standard is an incandescent bulb with sealed harnesses. You can also spec’ the new LED systems which are more expensive but come with a five-year warranty. These are optional on most trailers and represent a growing trend for trailer buyers.. Make sure the grounding is done well on the lights because the ground is often overlooked. Also be sure the wires are held securely to avoid problems in winter with hanging ice. For the long-term, it’s important that enough grease is put in the connections to keep out corrosion. Some fleets specify a little bit extra grease to ensure the corrosion isn’t going to get in and damage the plugs. It’s also important to run the wires where people driving nails in the floor won’t hit them, and where they won’t be damaged by items flung up off the road.

9 Floor

The standard is 1 3/8″ laminated hardwood. If you want to keep the unit for a long time go with the oak floor which is more resistant to water. You might want to put extra screws in the floorboards to make sure the floors stay secure and the crossmembers don’t roll. In temperature-controlled units or reefers, full aluminum, inverted T-floors, basically an aluminum floor, can work well. Options include different types of roller systems for operations like airfreight and courier where there is a need to quickly roll stuff off and on, containers and skidded loads.

10 Crossmembers

Twelve inch centres are standard, with 4″ I-beams. To get extra height you may have 3″ I-beam over the bogey at the front over the coupler and a thinner crossmember for tire clearance. If you don’t need the extra height you can spec 4″ throughout.

11 Suspension

Air ride is in vogue, and for general freight carriers that may be the best option. Air ride will give you a smooth ride whether the load is heavy or light, but you have more complexity in valving and cost with air ride. There are also cases where air ride is not necessary.