Light Engine
(Aka; Nuclear meltdown.)
A long time ago, back in Metalwork class, I recall making a small boat out of tin. We had to cut out a template, fold it together, & solder the seams with an old manual iron.
The interesting part was, the boat had an engine, which consisted of just a coil of copper tube, with both ends sticking out the back of the boat. A tea-candle was placed under the coil, & heated the water inside until it boiled, sending a spurt of water out the end of the tube, & propelling the boat. The tube would suck water back in, & the process would repeat rapidly once the coil was up to temperature.
I thought I'd use the same principal for my build, substituting the naked flame for the heat of an over-driven LED. That sounds easy....
Engine #1
I started with the copper tubing, coiling it around a socket extension, & brazing a thin brass plate to the coil.
I also added a copper strap to the rear of the brass sheet, to provide support, & help with heat transfer. A couple of spare XM-L2 LED's were scrounged up, & re-flowed to a pair of 16mm copper boards, which I had previously hand-modded to make them DTP.
Before adding the LED's, the engine was tested in water with a small jet-lighter, & worked as expected. The LED boards were then soldered onto the 'engine', test leads attached, powered up, & tested again in water.
...Please forgive that mess....
Unfortunately, the copper engine seemed to be doing too good of a job of wicking the heat away, & I could not get localized boiling in the copper coil.
No problem - I'll knock up something else with more power...
Engine #2
This time, I thought I'd do a variation on the design, making a small boiling chamber out of brass ammunition shells.
Two shells were cut & brazed together, primer holes brazed over, & copper tubing brazed into holes drilled at either end.
I was hoping the brass would hold the heat, & with the addition of a little more power, courtesy of a pair of triple 219c's, we should be in business...
Engine #2 was rigged up on a 'test-raft', with a couple of ~half charged LG MH1's in Direct Drive. That should do the trick!
The engine gave a brief sign of life, prior to both triples letting out a whisp of smoke, de-soldering themselves, & plunging into the water....
I then tried using the mounting plate design from Engine #1, to give a little more surface area for the Noctigon's to hang on, but they complained again, & a wire de-soldered itself.
Time for another re-think....
Engine #3
After a long day with the first two engine failures, I figured I should sleep on it, & approach things fresh.
Water boils at 100DegC. Solder melts around 180DegC. Sounds like plenty of room to move, but the metal is working against me, drawing the heat away, & so is the water in the tube.
Getting enough heat through the brass to boil the water effectively, & maintaining that heat, was a finer balancing act than I had anticipated.
I needed to know what was going on, & I needed a finer control over the power/heat source.
The copper we all love was working against me, wicking away heat from the boiler. I had to make a new motor, entirely out of brass.
I started similar to Engine #2, but using a single, larger shell, & brazing in two thin brass pipes. The larger diameter shell allowed me to file a flat on it's side, to give the LED boards more surface area where they mount.
I went back to using the pair of 16mm boards with the XM-L2's, & used a Fet +1 driver with a good range of power levels to choose from at the top end.
The Engine assembly was mounted dry on the new "Dyno-Thermometer" rig for initial testing, where I could monitor the power level & heat.
When I was happy with the dry testing, & had the heat under control, I made a much sportier 'test raft', & tested again with water in the boiler. I settled on around 5 amps, which brought the water to the boil quick enough, but kept well short of the de-soldering red zone.
Ok - all aboard, & strap your selves in.....
www.youtube.com/embed/SOVVWLJlaIY
So, it's no powerhouse, but it will propel the vessel, & the LEDs are 'water cooled' to a certain extent!
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