Friday, 13 May 2011

It's Hard To Get Your Bench To Eat Ice Cream...

My life has been spent trying to reduce the weight of something. When I built cars, I spent a lot of time removing metal to increase the weight to horsepower ratio. Over my entire 30-year career as a photographer, I spent a great deal of time and a huge amount of money searching and buying lighter weight equipment for location work. I have also spent my entire adult life trying to reduce the weight of my butt, but maybe that isn't a good analogy here.

Becoming a hand tool freak has changed a lot of things for me including this thing I have about weight-reduction. Now I am trying to calculate the best way to add weight to something, rather than remove it – specifically, a workbench.

I have been mulling over designs for a workbench for years now. My problem with coming up with one I feel would fit the bill is that I know all the things that I don’t like about a bench, but damned few of what I like. I have worked at a few benches in my time, but only one or two that were "real" benches. The rest were just a bunch of 2 x 4’s cobbled together in a squeeze. While shoddy, wobbly and rather unattractive, those stand-in benches did teach me one thing about a good bench - it doesn't have to have 'weight', it has to have 'serious weight'.

How to add massive weight to a small workbench has been the rub. I have come up with a number of ideas, everything from simply using massive timbers to storing tools beneath. Processing each idea, though, has resulting in points from the “don’t like list” coming into play.

It boils down to this; I want a solid workbench that isn’t a dust collector. I don’t want to chase the damned thing around the workshop and I don’t want one that is a pain in the butt to keep clean, both on top, and underneath.

A possible answer to my quest for an ideal bench, at least in the weight department, may come from an idea that I am currently mulling over. This current brainwave can be summed up with one word – sand.

To say that the working facilities I have been struggling with for the past two years are “limited” would be an understatement. I have been working off of a portable work bench that has a piece of ¾ ply clamped to it to extend the top and two 50 pound bags of sand strapped to a make-shift cross member to add to its weight. It was those two bags of sand that gave me this brainwave.

Whenever I read some woodworker bemoaning the
fact that his or her bench is only 8' or only has
one vice, I laugh, and laugh, and laugh.

Here’s the thing; before I strapped those two bags of sand to it, just trying to drive a screw would start the chase. After the bags were added, the bench became reasonably stationary, even while doing light planning. It all boils down to weight.

Question: So what if you add those sand bags to a normal looking workbench?

Answer: It would look seriously silly.

Question: how can you hide a 50-pound bag of sand in an open workbench?

Answer: in the legs.

This is a render in perspective without any
embellishments. It does show the widths
aren't that out of proportion with the height.
Here's what I have been mulling over…

Concept:
  • As a base calculation, I will use one of the cheaper woods, say Poplar.
  • While a standard bench top is 24-inches deep, I would prefer one a little deeper to help make up for its shorter length, which will be 5-feet. Hence, the depth of the top for me is 28-inches.
Dress this up with a bit of trim and it
might not look too bad.
  • By positioning the rear legs flush with the rear edge of the top and allowing for a 4-inch set-back on the leading edge, I would be left with 24-inches between the outside edges of the legs.
  • It would be possible to build the legs out of 12-inch stock, but I think 10-inch stock would be better.
  • Considering that 10-inch stock isn’t actually 10-inches wide and allowing for joining, you end up with an inside dimension of 8 inches.
Volume Calculations:
  • 8-inches by 8-inches equals 64 square inches.
  • The average height of a bench leg is 28 inches.
  • 64 square inches times 28 inches in height equals 1,792 cubic inches.
  • There are 1,728 cubic inches in a cubic foot.
  • This means that one leg would have an internal volume of just over 1 cubic foot.
Weight Calculations:
  • On average, 1 cubic foot of sand weighs 90-pounds.
  • As one hollow bench leg has a volume of just over 1 cubic foot, filling with sand would then result in that one leg weighing in at about 92-pounds.
  • Four hollow bench legs filled with sand would then weigh about 368-pounds.
Comparison:
  • Maple has an average weight of roughly 3.5-pounds per board foot.
  • To equal the same weight, it would take 26 board feet, or roughly one piece of maple 12-inches by 12-inches by 28-inches.
Cost:
   Poplar:
  • Here in Canada, a running foot of 12-inch poplar from Home Depot runs about $3.50 a foot
  • Each leg takes about 11¼-feet of stock, so at $3.50 a running foot, one leg would run you $40.
  • The wood for a set of four legs would run about $160. 
  • A 50-pound bag of sand costs $12.
  • Four legs require four bags of sand so the cost of the sand would be $48.
  • The total cost for a set of seriously weighted legs? About $210.
    Maple:
  • You couldn't find 12-inch by 12-inch maple, so you would have to do a glue-up.
  • However you got it, a board foot of maple costs $9.50.
  • Each leg takes 26 board feet, so each leg would run you about $247
  • The total cost of a seriously weighted set of legs in maple would run you about $988.
Conclusions:
  • Chris Schwarz estimates his latest Roubo bench weighs about 300-pounds.
  • At 368-pounds, this idea has legs that weigh in at more than that and the weight of the top hasn't even been factored in as yet.
Go figure.

Peace,

Mitchell