Despite this blog being mostly centralized around aviation, I have always considered myself an engineer and tinkerer first, and an aviator second. Below are some of my old projects from my younger days before I embarked the pathway to the airlines. Although not super informative, I figured I needed to devote at least a small page of my blog to some of the Frankenstein-like creations from my youth.
I have always wanted to make an airplane… or at least something that flies. I think most kids do to at least some degree. The difference with me is I was lucky enough to have a garage stocked with a welder and an assortment of basic hand tools. If you combine that with a family who really doesn’t mind their son bringing home broken lawnmowers and bicycles from the junkyard, you get the recipe for innovation.
A MIG welder really is a magical tool. It essentially allows one to glue bits of steel together in a way that is safe enough for a 12 year old ,without requiring a large skill set. This for me meant that my legos and erector sets were replaced early on with bits of junk steel.
Eventually, I began to weld everything together. Without much knowledge of engineering or structures, I eventually learned what bent and what didn’t.
So I got better and eventually decided to start on a larger project. I knew that it was probably too difficult to make an actual airplane out of scrap lawnmowers, so I settled on the next best thing, a hovercraft.
I still remember how much work this project demanded from my 12 year old self. It was truly a big undertaking which required some new skills. Hand fiberglass lay-up, vacuum bagging, propeller balancing, and wood laminating were some interesting new skills that took some time to get used to.
Eventually, I managed to get the thing finished:
The hovercraft was an awesome toy… I mean how many 12 year old kids get to say they have a hovercraft at home? But soon however, I became more interested in mechanical engineering and combustion engines rather than making small lawnmower powered contraptions.
My next big endeavor was the design and construction of small jet engines. This fascination would last for the next three years.
My first designs were small pulse-jet engines. They were simple to build and easy to modify.
I began welding bits of stainless steel exhaust pipe together with stainless milkshake cups bought from the kitchen section in target. Some people view all of that shiny stainless as kitchen appliances, I saw jet engine parts. Pulse-jets really have only moving piece: Spring steel pedal valves. Because these valves cannot be cut with tin snips, I learned a process called electro-chemical etching. This process involves attaching electrodes to a piece of painted spring steel and a cathode. Both are immersed in a saline bath. Before dipping, the spring steel is etched with an exacto-knife over a template shaped like the reed valve. When power is applied, metal is dissolved from the exposed area on the spring steel and is transferred to the cathode. Pretty nifty.
Although pulse-jets make a bunch of noise and blow blueish fireballs, the reality is they are utterly useless. Eventually, I turned my sights to the more practical turbine engine.
But of course, I couldn’t leave you without a video of the actual engine! Enjoy 26 seconds of the most annoying sound in the world:
This was by far the most complex build I had undertaken to date and would require all of the skills I had learned so far.
I thought about what I would use the engine for. Sure it would be an awesome noise maker, but burning a bunch of kerosene for nothing seemed wasteful. I finally decided to incorporate the engine into a small go kart.
Because there was simply no way I could build my own compressor and turbine, I decided to use a turbocharger for the engine’s core. This meant the engine would use a radial compressor and turbine, resulting is a design similar to an aircraft’s APU. Radial turbine engines are great at generating a bunch of high pressure exhaust gas in a small package, but due to their airflow geometry, are terrible thrust producers. Thus, if I ever had a dream to move a go-kart with a home-built jet, my only option was to use a power turbine to extract shaft horsepower, effectively making a turboshaft.
I would need to build an engine which could produce a lot of exhaust gas. Regular sized automotive turbochargers like T-25s an even larger T-04s simply wouldn’t cut it. I needed something Diesel sized.
Luckily, I stumbled upon a huge Cummings Diesel turbocharger on Ebay for 50 bucks! I bet the unit was over two-grand new. Either way, it was the perfect gas-generator I was looking for.
The build went smoothly, but did requiring extensive welding, shaping, and testing. Parts were hard to come by. I originally used an old oil pump from an old truck, and the oil sump the compliment it. I ran the pump off of a 12v electric scooter motor. Eventually I managed to use a soda carbonation pump to feed liquid kerosene to the thirsty motor.
Soon came time to test run the engine. With everything in place, I attempted my first run of a true jet engine. Because I didn’t have a coupling for an electric starter, my only hope of turing the engine over was a meager leaf blower. I had seen this method work with other homebuilt engines and thought it would surely work for me. With the leaf blower cranked, the moment of truth had finally come… but to my dismay, the engine wouldn’t start.
I couldn’t believe it! I thought for sure I had built the engine correctly. From the burner can to the combustion and fuel injectors, the engine seemed to function perfectly. Yet when the engine began to rotate and fuel was introduced all that seemed to happen was a hot flame out of the tail pipe and no engine acceleration after the leaf blower was pulled away. Today, I know this familiar scenario as a hung start, which is normally caused by a weak starter. Back then I was flustered. Eventually I caught on and realized that my massive turbocharger simply required more juice to turn over than one leaf blower could supply. The solution? Use a leaf blower, a small house vacuum in reverse, and a air compressor.
That wonderful whistling of a turbine engine that is so familiar.
Things were going great, I has successfully created a working gas-turbine engine out of spare parts and scrap metal. Prospects were high… until I hit my first roadblock.
I had reached point where my ability to build and create new things, exceeded the capabilities of the basic tools I had available. I remember this moment vividly and feel that it is an important point in the life of every tinkerer.
When I tried to manufacture the power turbines required to extract shaft horsepower from the exhaust gas of my engine, I began to realize that without the capability to machine parts, manufacturing turbines and bearing holders to the proper tolerances simply wouldn’t be possible. This meant my hopes of completing my project simply wouldn’t become a reality. Still today, this project remains dormant with the hopes of perhaps someday finding a suitable power turbine to get it all finished. (By the way, if anyone has an old 1st or 2nd stage turbine from an Allison 250 laying around, please let me know! 😉)
Time went by and I played toyed with some ideas here and there, but overall didn’t really work on anything big. The thought of reaching the limit of my tooling capabilities always lingered.
Then I got a lathe!
Finally, I have to ability to turn big cylinders of metal into smaller cylinders of metal. This meant I could make anything from candle stick holders, to bearing sleeves, all the way to engine cylinders. Instead of turning back to jets, I decided to work on reciprocating engines. In the midst of rising gas prices, I thought it would be an excellent time to try to work on improving the efficiency of the ever-present piston engine.
A New Reciprocating Engine:
My last big childhood project involved the research and development of a small two-stroke engine which could run without using pre-mixed oil.
I made the engine cylinders out of 1100 aluminum with a mandrel steel insert. It is important to use mandrel steel pipe for cylinder inserts because it doesn’t was extruded rather than formed from a flat piece of metal and welded.
I pressed the two together by machining them to a interference fit and then heating the aluminum chunk in the oven and putting the insert in the freezer. Ended up working out great!
Making a custom piston was a challenge. Of course 1100 aluminum isn’t an ideal material, but the engine was being built as a proof of concept and didn’t need to run very long.
After making a bunch of aluminum shavings, I eventually managed to whittle out the engine.
Since, I haven’t really made anything as complicated or as interesting. I always wonder if I will ever go back to my projects again. I have a bunch of ideas for new things, but never seem to have to time to turn anything out. Hopefully one day I will find the time!