Long crates

The problem with length

A long thin load behaves like a beam. Lift it in the middle and the ends droop. Lift it at the ends and the middle sags. Add a bump and it whips. A crate that is only a long box around a long item will not stop any of that, so the construction has to supply the stiffness the load lacks.

That is why a long crate is built differently from a compact one with a larger lid. Its runners run the full length, a strongback adds bending stiffness, and the load is carried by supports placed at intervals along its span instead of lying on the floor.

Strongback, runners and cradles

The strongback is a deep timber, or a pair of timbers, set on edge along the length. Deep section means a high resistance to bending. It is fixed to the runners and to the end frames and ties the crate into a single beam, so lifting at one point does not twist the box.

Cradles are blocks cut to the shape of the load and spaced along the span. A round shaft sits in a cradle with a radius cut to match. Bar lies in a notched block. Straps or a hold-down over each cradle stop the load rising from it. Spacing is set by the load's weight and stiffness, and it goes on the written spec.

Tubing, conduit, angle iron and extruded aluminium arrive in bundles, and a bundle is not a rigid beam: tie each bundle with banding at every cradle, separate dissimilar metals with kraft or foam to avoid galvanic staining, and cap the ends so swarf and moisture stay out.

• Full-length runners under the base
• Strongback along the span
• Cradles shaped to the load
• Hold-downs at each cradle

Loads that call for it

Drive shafts, turbine rotors, long pump shafts, extruded profiles, linear guide rails, heat exchanger bundles, boring bars, steel tube and conduit all need this type of construction. So do rolled goods that stand on end in a tall crate.

Machined shafts and rails need extra care. Bare steel is wrapped in VCI paper or film, supports are padded where the shaft touches, and desiccant rides in a sealed bag. A shaft that has been ground to a bearing fit should never be placed on bare timber.

Handling a long box

Forklifts handle long crates badly. Lifting from one point means the crate teeters, and lifting from the end puts load in the wrong place. We mark lift points along the length, cut fork entries wide enough for tines to span the strongback, and add a centre-of-gravity mark on both sides, because the centre of a long crate is not always the middle.

In a container, a long crate sits along the wall and is blocked at both ends. Give us the container or trailer length so the crate leaves clearance for the doors and for blocking.

Tare, cube and export

Long crates carry a lot of lumber for their weight, because the structure that resists bending is heavy relative to the load. Tare is higher per pound of contents than on a compact crate. Cube is mostly set by length, and freight is often priced by the linear foot, so the crate should be only as long as the load plus clearance.

All the timber in a long crate is solid wood, including the strongback and cradles, so it is heat-treated and carries the IPPC stamp on a minimum of two opposite sides for export. Because the sides are long, we apply the mark twice, near each end, so it can be seen from either end of the box.

Long versus skid-base

A skid-base crate puts a heavy base under a compact, dense load. A long crate is about stiffness over a span. A long, heavy item may need both: a skid for the weight and a strongback for the bending. If the load is under a certain slenderness it is a skid-base job; if its length is many times its width, plan for a strongback.

Planning the route for an extended crate

Long crates pose planning questions that compact crates do not. Check dock door width and turning space, the length of the truck bed and the reach of the loading equipment before the crate is built. A crate that cannot turn into an aisle is a crate left on the street.

Ask the carrier about overlength rules on the route, since an extended load can attract permits, flags or a pilot vehicle depending on the roads used. We cannot give a legal ruling on that, but we can supply exact outside dimensions early so a dispatcher can plan. For air shipment, check the aircraft door opening and the freighter's ULD options before fixing the length.

What to send

Give us the overall length, the cross-section, the gross weight in pounds and the destination. Tell us whether the load is rigid or flexible, and where its mounting points are. A photo with a tape across the item saves a round of questions.