Oversize/heavy - suitable timber crate design

[Mona]

Hi,

Apologies in advance if information on this exists already. I've tried searching to no avail - maybe my search terms are off.

Anyway, we have a large painted steel sculpture (around 2m H x 3.2 m W x 1.8m D) in our collection which is slated for display in two months.
The crate in which it was originally shipped is structurally inadequate and needs replacement. We make/replace our crates in house, mostly from structural ply, framed with dressed pine support but this object is around 1200 kg and its width means timber tends to flex.

We have examined the possibility of using a steel frame to support the base and to which to attach runners/skids but welding such a large frame within our tight schedule will be next to impossible (fabricating loads of mounts for the same show).

Therefore we need to look at heavier duty timber than we normally use to reduce flex and offer structural support.

The distance the crate needs to travel is about a 10 -15 minute drive from storage to museum - beyond that, it will likely be housed within that for storage long term but we are not looking at a crate travelling long distances or needing to be ipsm compliant.

Does anyone have experiential based suggestions on travel and/or storage crates for such large and heavy works?

Many thanks.

[JasonO]

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[Chris Barber]

Hi Mona,
With enough skids under the pallet, the common construction of 3/4" plywood battened with 3/4" pine can often suffice for moderately heavy objects, and 2x4 lumber battens can work for very heavy objects if they are not too large. This becomes problematic for larger dimensions though, as the open structure of even a heavy pallet can sag under its own weight once it reaches a certain size, providing little structural support for the object.
If rigid support is needed, one alternative option you might consider is a heavy-duty lumber battens combined with a torsion box design for the load-bearing pallet. There are many approaches to a torsion box, but one example would be to replace the pine battens with 2x4s or 2x6s, flip them onto their narrow edges to make a kind of skirt around the perimeter of the pallet, add more 2x material to span the interior of this skirt in both directions at regular intervals (forming a grid), and skin the underside of the pallet as well as the top. This creates a fully enclosed box with a lumber grid inside. Joining each section of lumber securely to the plywood sandwich provides a rigidity otherwise unavailable in these materials. The tighter the grid inside the box, the thinner the top & bottom skins can be without sacrificing rigidity. For something this heavy I would try 3/4" plywood for the skins, and also consider a second layer of ply on top of the torsion box if the object rests on any narrow feet that can puncture the plywood. The caveat to an approach like this is the additional weight of the lumber. Full disclosure: I have not yet had the necessity of resorting to this approach in a crating context, but it is a relatively quick and inexpensive method to test compared to steel fabrication.

Chris