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.
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.
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.
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.
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.
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
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)
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.
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.