Aero ‘lectrics

Every now and again, I go off on a wild hair and do something completely different than what you are used to. I’ve made the most complex project I’ve ever attempted in a KITPLANES article—a full-house VOR/ILS/Marker test generator. I’ve done some really simple things like a headphone tester out of a single AA battery. Last April, we did some foolishness about the bread-cat emergency generator. This month you get the plywood workbench.

I’ve been wanting to design my own ultimate electronics work bench for nearly 60 years. I’ve always cobbled something together out of an old door and some scrap 2x4s with a light dangling from a string attached to the ceiling. That worked last time for nearly 40 years…sorta. I decided with reader Dave (“Dr. Dave,” flies an Aeronca Sedan on floats out of Anchorage) Mulholland’s prodding, I was going to make the electronics bench of a lifetime.

Here you go: nothing but half-inch plywood, a door, and a little bit of laminate flooring to the project, and it is the electronics workbench. For another Weir two-fer I’ll share the equipment and parts shelf designs for your shop.

I must admit to being just a little bit ashamed. I’ve been in this business for 60 years now, all the way from a 12 year old sweeping out the TV shop and then a professional engineer designing avionics for the last 50 years. In all this time, I’ve never had a really good workbench to work on. Mostly they’ve been 2×4 frames with wood doors for tops. This one is an absolute blessing to work on that I should have had a long time ago.

Construction details of the electronic test bench.

Building Materials

• Three sheets of half-inch plywood (CDX or shop grade), about $20 per sheet
• Five 8-foot-long 1×2-inch furring strips (hemlock fir), about $1.50 per strip
• Five 8-foot-long 2×2-inch furring strips, about $2 per strip
• One package of laminate flooring (enough to cover at least 17 square feet), about $25
• One gallon of boiled linseed oil, about $15
• One very long power strip, about $20
• One solid-core door, 6 feet 8 inches x 30 inches, about $50 (Hollow-core door about $25)
• Miscellaneous glue and nails

Start out by having the lumber shop do one major cut lengthwise on each sheet of the plywood. Sure, if you’ve got a table saw and competent help, you can make the cuts yourself. At a buck a slice, it is worth it to me to have the young kids in the saw shop schlep the plywood around.

How to slice the plywood for minimum scrap.

In the airplane world, we are used to building our aircraft from the “top down.” That is, the tail feathers or wings generally get done first, then the fuselage, and only then do we do the landing gear. We build benches exactly the opposite way: first the foundation, then the walls, and then the working top surface.

Beginning the assembly of the bench. The bench bottom is just about ready for the first of the shelf sides to be attached. Note in the background all the rest of the bench parts cut and ready to assemble.

I wanted more storage than the law should allow. Each of my pieces has more storage than I’ve ever had, and I think I’ll just about have enough for all my stuff. Each bench, then, needed to have room underneath to store all the stuff that I need to keep for all my projects. You can never have enough storage.

The bench shelving all done and braced for the attachment of the door. Note that the lab flooring bears a strong resemblance to the laminate used on the benchtop surface. It’s exactly the same stuff.

The soldering iron gets its own little mini-bench with sides on it to keep solder rolls, desoldering tools, and the ubiquitous toothbrush board cleaner from rolling all over the bench.

I’ve always in the past had a bench-top that wasn’t exactly great to work on. In general it was a hollow-core door with a door skin as my working surface. I wanted something better. I decided to use the belt and suspenders approach. The underlayment for the top was a solid-core door with cheap lauan skin (you can use a hollow core door for half the price, but it doesn’t feel as solid), then lock-together laminate flooring on top of that. I tested the laminate before I used it. I couldn’t scratch it with a sharp center punch. I couldn’t burn it with hot solder splashes or a hot soldering iron for a few seconds. Yes, after two minutes of the hottest soldering iron I had and continuous contact with the laminate, it discolored. It didn’t burn. It didn’t scorch. It simply discolored and then only after a couple of minutes of torture. Good benchtop material.

Now, if at some future time I really abuse the bench, I simply remove the flooring (it is held on by four screws in the corners) and replace it. No hassle, no mess. I highly recommend this laminate for anything you want to have as a benchtop, whether it be electronics or engine work. Tough stuff.

The engineering bench ready for the laminate top and top shelf. Note that the bottom is one single long sheet of plywood, and the top is a standard solid-core door 30 inches wide.

More Furniture

The bench turned out so well, I built all the rest of my lab furniture the same way: plywood structure reinforced with hem fir furring strips. For the heavy stuff (like the power supply and oscilloscope on the test bench) I’ll put a vertical support on the shelves. On one of the assembly benches, I don’t have the luxury of a vertical support, and I had to resort to a piece of 2×2 angle iron to keep the plywood shelf straight.

Yes indeedy, I’ve got a thousand dollars in materials to make 14 complete lab shelves (two workbenches, two parts shelves, three equipment shelves, a computer desk, and six bookshelves that would cost well over five grand if I were to go out and buy them on the commercial market. Take that extra four grand and go buy some decent test equipment.

The finished electronics bench itself. The test equipment on the top shelf is angled down with a combination of wood blocks under the back of the equipment, rather than having the top shelf angled. Much safer this way.

Speaking of which, note my four pieces of test equipment on the equipment shelf above the lab test bench. Each of these pieces of equipment needs to be read face-on direct (something about parallax readings being inaccurate). The problem is that building the shelf on the slant does not take into account the different angles needed for each piece of test gear—and once a piece of gear starts to slide, it just keeps on sliding. The answer is that I built the shelf itself square, and then for the instruments that needed to face down a bit, I used a combination of the aforementioned 1×2 and 2×2 furring strips, cut for each instrument, to prop the back end of each individual instrument up and therefore slant the face down. No chance of the equipment sliding off of a slanted surface; if it slips off of the furring strip it simply plops down onto a flat surface and that is the end of that.

The “engineering parts” shelving stuck over in the corner next to the workbench. Each of the parts boxes has 60 little drawers for little electronic parts. There are 540 little drawers, each of which can be divided into half for really small parts. There’s room on the bottom for plastic boxes with larger parts that wouldn’t fit in the drawers, and room on top for more plastic boxes with the remains of old projects (including some KITPLANES projects more than 15 years old).

I’m an RF cat; I work in the black magic world of Megahertz and Gigahertz, so the instrument on the far left in the bench photo is a “service monitor,” a $15K piece of 10 Hz to 1 GHz equipment that is a precision signal generator, spectrum analyzer, modulation meter, power meter, frequency counter, and communications receiver all in one package. There’s also a garden variety (Heathkit) power supply for 12/24-volt work, an inexpensive sine/square wave 1Hz to 1MHz audio generator, a 60 MHz oscilloscope, and my antique Heathkit transistorized voltmeter, milliammeter, and ohmmeter that has been my right hand for 40 years.

It rarely gets below 20F, but an electric forced-air heater with a “dummy” woodburning lamp makes the place warm and cheery during the non-fly months of winter. The card rack above with the little kids kissing is my wife’s reminder that we were about this age when we shared our first kiss nearly 60 years ago. Note that the engineering toolbox is on a stand just to the right of the fireplace and is made from solid 2×12-inch Doug fir to support the weight of the toolbox. Note also that on top of the toolbox are the plastic “deli” boxes I mentioned using for small parts in the October 2015 KITPLANES.

Other Workbenches

Just a word or two about the three workbenches in the downstairs shop/garage: one for woodwork, one for metalwork, and one for engine work. Same basic construction as the ones upstairs, but I only used a double plywood layer for the benchtop with no laminate. However, the top plywood layer is not glued into place, just held with a dozen nails. If and when that benchtop gets trashed, I’ll simply pull off the top plywood sheet and replace it with a new sheet, or if I’m strapped for cash I’ll simply turn the plywood over and use the second surface. Note that the top of the workbench is covered with cardboard cut from cheap shipping boxes. If you build the benches exactly 6 feet (72 inches) long these shipping boxes will just fit onto the top.

This is the downstairs general purpose workbench. The top is a double sheet of plywood covered with cardboard moving boxes opened up and taped together. So far this one has seen a lawnmower carburetor overhaul, a garden tractor generator repair, a Cessna carburetor heat box repair, and a weed whacker cutter head installation. The only thing I would redo if I had it to do over again would be to make the bottom a solid piece of plywood.

The production parts shelving, nearly like the engineering parts shelving, but a bit taller, with room for all the heavy stuff (like rolls of wire) on the bottom to give the unsupported shelving stability. Rows of plastic boxes on the top are for bulky stuff like shrink sleeving and completed production assemblies.

Now that I’ve got decent benches to work on and equipment shelves to put parts on, it is back to the multimeter series. Voltage Ahoy! Have fun, see you next month, stay tuned.