Lightweight Bench Work Thoughts

Erie's Harlem 149th Street Terminal in HO scale

I'm contemplating redoing my Erie 149th Street pocket terminal so that it is more manageable to move around. I had a few minutes this morning while waiting for software to update to get started on testing a couple of material options.

This morning I am looking at framing members. Each member is 12 inches long and 3-1/2" wide. I will weigh 1x4 Pine, 3/4" 11-Ply Baltic Birch Plywood, and a composite construction of 1/4" Luan Plywood w/1x4 Pine Spacers. Another option is to cut weight-reducing holes with a large hole bit in the solid materials (think aircraft wing ribs), but that won't be tested here.

Results:
The 1x4 Pine, a traditional bench work framing member is a soft, relatively lightweight wood that is easily found at big box retailers. Individual members are not always perfectly straight, and because they are soft, they can present some minor challenges associated with crushing and clean edges, etc. The weight of 12 inches is 7.9 oz.

The 3/4" 11-ply Baltic Birch Plywood is somewhat more difficult to find, and requires preparation work to cut into the 3-1/2" strips for bench work use. The advantage is that it is an efficient use of material (I have not done calculations of cost), it is stable, strong and works more like a hardwood in terms of drilling, etc. It is heavier, though, as the 12 inch piece I am using weighs in at 8.6 oz.

The composite member of 1/4" Luan Plywood and 1x4 Pine spacers is a technique I saw described in John Chivers' article on a British web site of the Barry and Penarth Model Railway Club. This intrigues me because I do have a bunch of 1/4" Luan at my disposal at the moment. This seems a very efficient use of material, although preparation time is greatly increased. Stability should be good due to the composite construction and the materials are easy to work with. For a 12 inch section, this assembly weighs in at 6.8 oz.

Roughly, each member section is about 1 oz per foot difference from the next. I currently have approximately 42' of framing members in 1x4 Pine (this is for the support of the top only, and does not include the base.) Current weight, then, works out to 42 ft x 7.9 oz/ft = 331.8 oz (9406.37 grams) or 20.74 lbs (9.4 kg). The same framing plan in 3/4" plywood would be 22.6 lbs and the composite construction section would be 17.85 lbs.

So the pine is not too bad start with, but there is some savings with the composite section, maybe as much as 3 lbs. This assumes that the framing is the same and there are no other additional members needed for stiffness.

The main weight of the existing bench work is in the top, which is 3/4" 15-ply Baltic Birch Plywood. This really nice cabinet grade plywood is about 40 oz/sf (about 2.5 lbs/sf). The top of 149th Street is approximately 25.5 sf, so it weighs 1020 oz or 63.75 lbs. Total weight of the top with framing therefore is approximately 84.49 lbs. That's heavy already, and doesn't include anything else like track, wiring, structures, scenery, etc. I would imagine that could add at least another 10 lbs. This means we are talking about 100 pounds. Not impossible to move on one's own, but given the size and shape of the layout, it is not easy to maneuver.

Alternatives for the top would be 1" foam insulation (maybe .13lbs/sf), 1/2" Gatorfoam at about .625 lbs/sf) which would mean a weight of approximately 4 pounds for foam insulation and 17 lbs for Gatorfoam board. The lightest combo would be composite framing members and 1" foam insulation for total weight of approximately 22 lbs or about 62 lbs lighter than the existing layout construction.

Hmmmmm. That sounds worth the effort at this point as I stare at the layout with the thought of moving it by myself...

The story continues over at the PoNY blog.