The jet engine combustor is now mostly complete, all that’s left for it is to #1 drill/tap for the spark plug and fuel injector(s) and #2 add an intake duct for compressor air. I’ve also mostly completed the 3D model – there aren’t many straight lines or surfaces on it, remembering all the 3D modeling tricks to make this was a lot of fun. I even went a bit overkill with the model – I may not actually build a bell mouth intake, screen, and/or jet tube.
The biggest looming challenge is deciding on a hole pattern for the flame tube. It’s critical that the flame tube holes are in the right places to correctly ‘hold’ the flame through various engine speeds, particularly while starting. If there are too many holes the air will mix too readily and the flame will be blown out, not enough holes and the engine will starve for air and not achieve self-sustaining operation. This is the biggest area for experimentation on the system and it’s why I made the flame tube easily removable from the combustor, modifications may need to be made.
- Finish 3D module including stand w/ various support systems
- Oil system (Oil tank, oil pump, electric motor)
- Fuel system (This will be propane at first for simplicity and safety, but provisions may be made for future use on Diesel/Kero/JetA)
- Starting system (Air jet strategically aimed at compressor wheel)
- Ignition system (old ignition coil excited by a power transistor pulsed by the control system)
- Electrical design, construction, and programming for instrumentation & control system (tachometer, temperature sensors, etc)
Today as I was backing the bus into a parking place, the clutch pedal suddenly became unusually light. It did not stall as I slowed down, so the clutch wasn’t stuck engaged – however once pulled out of gear it would not go back in while running, meaning the clutch was at least partially engaged.
I’ve always thought of the engine/transmission that are in the bus as temporary – I didn’t do much to these other than disassemble, clean, and reassemble. As such, there have been one or two roadside repairs needed, but I’ve always been able to MacGyver it well enough to avoid a tow. That wasn’t the case this time and I had to have it towed a few miles back home.
It’s not a problem with anything I can see on the outside (pedal/cable/fork), so instead something has occurred somewhere inside the transmission. I didn’t hear any pops or bangs, so likely it’s something along the lines of a bent clutch fork. I’ll pull the engine/trans over winter to both find out the problem and also rebuild for more speed, less noise, etc.
Before anyone gets excited, this is in reference to BUILDING a gas turbine (jet) engine rather than flying one, but it should be almost as much fun…
I’ve had a gas turbine (jet) engine on my ‘some day’ projects list for a long time. While cleaning the shop the other day I realized that I now have basically everything needed to complete this: a spare turbocharger, old oil pump, numerous microcontroller demo boards, various switches & sensors, scrap metal, and an assortment of plumbing fittings. All that’s needed to make it happen is to design and build it – a fun ‘free’ project.
I started on the combustor tonight. Fabrication should be generally easy compared to the CNC machine build, however without a lathe or mill there are some parts that I will have to fabricate creatively. I have jumped the gun a bit in not designing digitally first. In general the design will consist of wild guesses based on other similar projects online; so I haven’t lost out on anything by not having a digital model first, but I will create one as I go to make future changes easier to understand.
Christina and I went for a short cross-country flight today. This was the first flight that I wasn’t either solo or with a flight instructor. It was a bit bumpy, but extremely clear and Christina got a lot of pictures.
I haven’t updated in quite some time; summer was very busy with work, travel, and the occasional practice flight. I documented a number of these things with the intention to later post, however I failed logging into my phone one too many times and it deleted all photos.
Bus: Only minor work done on the bus, mainly more wet-sanding & polishing.
CNC: I created a homemade drag knife for cutting out vinyl/cardboard/paper. This is still a work in progress as are accuracy refinements and fine tuning.
Aviation: I passed the Private Pilot check ride! This generally means I can now fly any single engine land airplane (that does not require a Complex, Hi Performance, or tail-wheel endorsement) to/from any airport (besides the obvious: military/etc); and I can now carry passengers that aren’t flight instructors. I should be getting the official plastic certificate (There’s no such thing as a “Pilot’s License”) card in the next few weeks like the one below.
In practice, switching to something other than a Cessna 172 would require a little bit of transition training and there are time limitations to renting the trainer plane. So not sure what’s next with this hobby, but there’s a lot to learn and it’s still very interesting…
A few years ago we glassed in the screen porch. Installing “real” windows would have completely changed the porch and been fairly pricy. So instead I made my own custom wood frames to match the size of each of the screened sections and had regular sheet glass cut to fit in each of the frames. I then installed the frames with hinges at the top to allow the windows to either be propped open or latched closed. This keeps the porch generally the same, but with the windows closed allows just enough heat to be retained to over-winter some plants. Since this is completely custom though, I couldn’t find any good options for hardware. For the last few years I’ve “temporarily” had the windows either held down with screws or propped open with paint stirrers.
This weekend I finally got around to designing, fabricating, and installing the custom permanent hardware. The hardware consists of a regular butt hinge that I pressed the pin out of. I then welded a sheet metal section to one side that I had bent to 90° and drilled holes in. The modified side is mounted to the house and the smaller side is mounted to the frame. In the closed position the hinge holes line up and a securing pin, made from 1/8″ wire, is inserted. In the open position a prop rod, again made from 1/8″ wire, connects the two hinge holes and holds the windows partly open for somewhat of a “bahama shutter” look.
The rear VW emblem on the golf serves a number of purposes:
#1 – It’s an emblem.
#2 – It’s the latch and handle for opening the rear hatch. Pushing in at the top of the emblem causes the hatch to unlatch and the bottom of the emblem swings out to use as a handle for lifting.
#3 – (what this is all about) It’s a back-up camera. When in reverse, a small camera is pushed through a trap door behind the emblem causing the emblem to swivel up. The golf’s controller knows not to unlatch the hatch if it see the emblem swivel while in reverse (because it’s the camera that has swiveled the emblem, not a person).
Having a backup camera on a car that I can practically lean back and touch the rear windshield from the driver’s seat doesn’t make a lot of sense, most of the time. I have gotten used to it though – it’s great for towing and I have lines on the garage floor that allow for precision parking every time, maximizing usable garage space. A few weeks ago the camera stopped working; I investigated further and found that one of the arms of the extension mechanism had broken off. At that time I grafted a sheet metal strap onto the plastic mechanism and melted parts of it back together. This lasted a about a week, so this weekend I re-produced the entire plastic part completely with steel.
During the many cycles of assembly and dis-assembly of the camera mechanism I encountered a problem where any time it was put into reverse the hatch would open! This is kind of a funny outcome since it’s still fulfilling the purpose of more visibility when in reverse, just in a different way. This would be inconvenient, to say the least, so I tracked the problem down to some frayed wire connections. The shorted connections caused the hatch switch signal not to be ignored when the camera was deployed; re-terminating the wires fixed the problem completely.
Lots of yard work lately, the tilling and composting last spring definitely seems to have paid off and grass is finally growing even in the shadiest areas. The bus was enlisted into the effort as plant transport, and we also picked up a big landscape boulder. A big spider joined in with guarding the garden hose, see brick for scale.
This week I was in Atlanta for a conference at Stone Mountain. We hiked to the top after dinner one night, I got some OK pictures from the top….