Troubleshooting “Space Age” Electronics

On the last few test drives the blinkers had begun blinking very fast. On many cars, even today, which use a thermal timer relay this would mean a bulb was burned out. The bus, however, uses a resistive/capactive timer circuit that’s relatively immune to such load changes. I opened up the ‘black box’ hazard/blinker control module and even though it only consists of a few relays, a pair of germanium transistors*, and a handful of discrete parts it’s by far the most sophisticated electronic part in the bus; actually it’s the only electronic part if no radio was installed.

*This was roughly the time frame when people discovered that silicon was nearly as good of a semiconductor but far cheaper and easier to work with.

Troubleshooting “Space Age” electronics like this is basically the same as troubleshooting modern electronics:
#1 – Replace any/all electrolytic capacitors.
#2 – If it doesn’t’ work, throw it away unless it’s really valuable and further in-depth analysis can be justified.
This repair was no different, though I had to guess at the values since the capacitor code/markings were non-standard and only decipherable to electrical engineers of 1960’s Germany. With new capacitors its back to blinking at a good rate for both blinkers and the hazard signal.

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The clock also needed attention as it stopped a while back. Once I opened it up I found that everything appeared to be OK. I poked the rewind contacts with a pin while the clock was powered on and there was a small spark followed by a successful rewind; meaning the contacts were just dirty. After cleaning the contacts it successfully went through it’s usual automatic cycling. It’s a ‘normal’ old-fashioned wind-up clock in every way except that there’s a solenoid on a crank to rewind it and when the spring unwinds electrical contacts come together to energize the solenoid and rewind itself. Because it always has battery power available, the spring only lasts a minute or so before it cycles again.

Also, not pictured, I finished fabricating the passenger seat frame and added tabs to the seat mount. The seat pads arrived for both front seats; all seats are now complete and ready for covering in the spare vinyl that I have set aside.

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Atlas/Craftsman Lathe Reversing Switch

Originally the Atlas/Craftsman lathes spun in only one direction; because of this they came with only an On/Off switch integrated into the lathe’s headstock. At some point in my lathe’s past the On/Off switch was removed and a reversing ‘drum switch’ added. The drum switch gives the flexibility to spin either directions for special uses (cutting metric threads, power tapping, etc) however it’s it’s too big to fit in the lathe’s headstock.

The previous owner had the switch mounted on a wooden arm extending up from the lathe’s workbench; re-using this idea would work but since I’ve moved the lathe to the shop countertop the arm would need to be rebuilt and I also don’t like the aesthetics or the need to reach over the spinning work to turn it on/off. Another option would have been to mount the switch under the lathe base, however for the carriage to clear the switch would require raising the lathe – it was already at a good working height and raising would effect stability/rigidity as well as being susceptible to dripping oil. Lastly, it could have been mounted just anywhere on the ‘outside’ of the lathe (on a guard door, past the tailstock, etc) – none of these locations seemed great and overall this just seemed like giving up.

So what I ended up doing over the past few nights was locating the switch in the only volume of space just big enough for it, under the motor. This location has the added benefit of making the wiring short and simple. As-is, this is of course very inconvenient, but I chose it with creating a linkage in mind. The addition of the linkage allows the original On/Off switch hole to be utilized (previously this was just an open hole), puts the control in a convenient place, and makes it look like it was designed this way. The linkage was a challenge and took a few iterations to get right. It consists of a 1/2″ OD steel tube that runs through the headstock, supported by two metal plates I fabricated. At the end of the tube I welded on a nut to accept a bolt that bolts on another arm I fabricated. The arm has a bolt welded through it that engages with a slotted lever welded to the drum switch’s lever. The resulting contraption actually works very smoothly: pushing IN runs the spindle forward, pulling OUT runs it reverse, and returning to center is Off. All that’s left to do is create a matching knob and mark/paint the switch plate.

Reverse Forward Off

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Atlas/Craftsman Metal Lathe

This winter I’ve done some much needed cleaning and painting of the garage; it’s survived the bus restoration and countless other small projects. This has put the jet engine project and bus transmission on hold, but I’m in no particular hurry with either.

Also, recently I picked up an old Atlas (Craftsman) lathe I found on Craigslist with lots of tooling. This style of late was made by Atlas from the late 1930’s through the late 1950’s; based on the numbers engraved in this one’s bearings it seems to have been made around 1956. The manual that came with it was published in 1967; but I later found a receipt for the manual, proving that it was a replacement and explaining why the lathe in the manual looks like the late 1950’s through mid 1970’s version – both machines have all the same features and function the same though. For the most part it was in good shape and only needed some heavy cleaning, repainting, and a new motor capacitor; there are a few mechanical areas for repair/improvement that I will tackle, but nothing that prevents it from operating now. The original motor used a flat capacitor that’s no longer made in it’s motor base, so I had to get a little creative with mounting the replacement on the side of the motor.

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No particular project in mind for this, but no doubt it will come in handy with other projects especially since it has the milling attachment allowing it to serve as a small mill as well.

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Using a Real Aviation Headset with a PC Simulator

In parallel with real-world flight training I’ve begun to use a PC flight simulator more seriously. This reinforces what’s learned in the real plane and also allows me to practice flights ahead of time. The simulator is only vaguely analogous to real flying though, so the more I can do to make it realistic the better. One realism point would be to use the real aviation headset, but the headset does not directly plug into the PC. After a good bit of research cross-referencing part numbers and checking schematics, I came to two critical conclusions:

#1 – Standard 1/4″ mono audio dimensions are the same as general aviation headset plug dimensions. (The speaker plug, not the microphone plug)

#2 – The sound card output levels are compatible with the headset’s required input level. (not so low that they’d be inaudible, and not so high that they’d blow out the speakers on even the lowest setting)

Once those realizations were made it was easy enough to make an adapter cable from a scrap audio cord and a $2 1/4″ mono jack. There are ready-made adapters online, but these go for far more then even the standard 5X markup for anything with ‘aviation’ in the description; so it was worth the effort to spend a few minutes and build myself. The microphone connector is more special-purpose and would require finding the special jack and likely some circuitry to make the levels work for the PC mic input, I don’t do anything in the simulator that requires the microphone though, so that connection just stays unplugged.

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Interior Insulation & More Speakers

Since I’m again waiting on engine components, tonight I insulated the interior panels with jute insulation and added speakers to the rear interior panels. The rear speakers are lower than I’d like, but the bottom of the wall cavity is the only place thick enough (barely) to allow the speakers to sit mostly flush with the interior panel. I’ll be making era-appropriate covers for all 4 of the larger speakers that should provide some protection.

Insulation Insulation Insulation Insulation Insulation

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The last few nights have been spent installing the electrical harness and getting all of the electrical parts working. The lights (high/low headlights,blinkers,hazards), wipers, clock, ignition, and starter are all working.

lights lights lights lights lights

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Engine & Battery Installed

Tonight I finished installing the baffles, reassembling, and reinstalling the engine. I also picked up and installed a battery since I’m getting close to hooking up and testing the electrics. Now that the engine is in I was also able to test and adjust the clutch linkage; this is working great, the only driver control that remains is the throttle cable. Remaining to-do prior to starting:

– Install heat exchangers, muffler, and rear apron
– Install alternator/fan/belt
– Connect and test electrical harness
– Connect fuel lines, fill tank, and leak test
– Connect throttle linkage

Engine Reinstalled

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Headlight Assembly Restoration

The headlight assemblies that were media blasted yesterday were primed and painted today. Once the paint was dry the bezels and lens were cleaned and polished, then everything was re-assembled. More media blasting was completed on the vent window frames and other miscellaneous parts. The pop-out windows were disassembled; all of the rubber was dry-rotted so it took considerable time picking all of the rubber out of the sealing channels before the screws could be loosened to separated the frame halves and release the glass. There was substantial rust and the screws are tiny, so many had to be drilled out. Most of the frames can be salvaged and the drilled screw-holes re-tapped for slightly over-sized screws. (The head of the over-sized screws is the same size, so no difference will be visible once assembled)

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Sandblasting Small Parts, Finished Gauge Repairs

With the colder weather I’m limited to painting only small parts, the garage is heated but painting requires so much ventilation that the temperature drops below the paint minimum temperature. If the catalyzed automotive paints I’m using (epoxy, acrylic urethane) drop below their minimum temperature during the curing process, the molecular cross-linking stops and the paint is permanently in a gooey state. So since I’m limited to painting small parts for a while I needed a way to strip the paint and rust from all the various small parts. Sandblasting is a quick way to do this. However I had no way of recovering the blasting media, making blasting completely impractical, messy, and wasteful for small parts. To solve this problem I found a (deeply discounted) blasting cabinet that will enable blasting the small parts inside without using excessive amounts of blast media. After the performance today I wish I had gotten this a while ago because the results are much better than can be obtained by hand, infinitely faster, and with barely any effort required.

After many parts were blasted I finished the gauge restoration. The broken fuel gauge needle was replaced with a section of a “T” pin and painted to match the other two gauges. The sunburned celluloid indicator light lenses on the back of the speedometer were replaced with new lenses. Finally, everything was re-assembled including repainted light rings for all the gauges.

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Speedometer and Clock Restoration

Taking another break from painting/sanding, I worked on cleaning up the speedometer and clock. The speedometer was in generally OK condition but needed some polishing. In the process of disassembly and polishing the bezel and glass I found that the light ring needed repainting. The light ring is the khaki-colored ring between the glass and gauge face, it reflects light from the back of the gauge housing onto the gauge face. In other words the gauges do not have illuminated numbers like a modern car, instead the effect is more like holding up a flashlight to the gauge face.

The clock had the same cosmetic issues with the bezel, lens, and light ring. Additionally the clock’s hands had faded badly and the mechanism was not working when connected to 12V. The hands were repainted by carefully mixing model airplane paint to match the color of the speedometer hands (which also matches reference pictures online). After disassembling the clock mechanism I found the the fusible wire connecting the rewinding coil was broken. After the wire was re-soldered the clock fired right up. The clock is completely unlike the digital clock in a modern car (or modern anything) in that it is a mechanical action. The clock contains a spring, escapement, and flywheel just like a pocket watch and actually ticks while operating. When the spring gets close to unwinding a set of contacts closes and the aforementioned coil rewinds the spring.

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