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Photos of the latest work on our engine test bed. They are:
Upper left hand.
The test bed will have a software-based controller so we are presently writing the code. The components of a bench top test are labeled.
A. Controller. It is a 44-pin demo board with a Microchip PIC18F45K20. It is affixed to perf board that has solder pads underneath with 0.100 inch centers.
B. Simulator. Another board is programmed to produce approximate simulation of signals coming from an interface. Components to interface with the engine will be breadboarded on a similar piece of perfboard with equivalent connectors. This way, the controller can be tested and debugged to a large extent before it is even connected to an actual engine interface.
C. Power supply that provides regulated 5 VDC / 12 VDC. Right now it is more convenient to plug into 120 VAC.
D. RS232 / USB adapter connects to a laptop. The laptop runs on Ubuntu Linux. A program called minicom is used to send commands and recieve data. The data can be stored as a CSV file and analyzed in more detail on the laptop.
Upper right hand.
Digital storage oscilloscope of the output from the engine simulator. The trigger disk tooth position is at 6 degree increments. Two teeth are missing so it produces a gap in the clock signal every 58 pulses. Top dead center is located at about tooth 24 past the gap in a counter clockwise direction of rotation. The top trace is meant to simulate this crankshaft position signal.
The controller is also connected to a sensor of cylindeer pressure. It uses this signal to tell which rotation is compression/power and which is exhaust/intake among other functions. The bottom trace is meant to simulate an indication of compression.
Lower left hand.
The existing gas engine has a carburetor and a variable reluctance magneto system triggered off the fly wheel. Those components will not be used so that engine functions can be controlled electronically. A fuel injector valve is shown of the left. A throttle body will be machined from a block of aluminium. The valve requires a 42 psi. fuel pressure feed. This whole system will replace the carburetor. Also, an ignition system will be used that can be fired by a transistor output. Shown are a 35 kV ignition coil with spark plug wire attached and a capacitor typically used for this type of system. This way, fuel feed rate, air/fuel mixture ratio, and spark advance can all be controlled electronically.
Lower right hand.
Shown on the right is a cast iron V-belt pulley with the trigger disk bolted to it. The horsepower rating of a heavy duty V-belt is reached at about 50 amps on 12 volt alternators while it would require about 200 amps to fully load a 6.5 hp engine. To get better capacity, an 8 rib belt to a 200 amp alternator will be tried. This requires an 8 rib pulley shown on the left. The engine has a 3/4 in. keyed shaft while the bore on the 8 rib pulley is 7/8 in. A 3/4 in. to 7/8 in. bushing is shown. Also, a 1/4 in. by 3/16 in. rectangular key must be used as opposed to a 3/16 in. square key. A rigid coupling on the engine shaft and flange bearing on the other end may be used to extend the shaft. A machine shop cut a 3/16 key way in the 8 rib pulley for us. Currently, a wooden plank is being used as the base for all equipment. It likely that a base made from 1/2 in. aluminum plate will be used for a test bed with extended capacity.
At some point, a 13 hp engine might be tested. Then a pair of 200 amp alternators will be needed. The shaft on this engine will be 1 in. with a 1/4 in. key way. There are adapter bushings with a stepped key for going from 1 in. dia. / 1/4 in. key down to 7/8 in. dia. / 3/16 in. key.
The advantage of using DC alternators is that the load response is roughly constant over a certain range of speeds. This is needed to run an engine at different speeds and loads. An AC generator will overheat if it is run under heavy load at any speed other than the one correspnding to 60 Hz. To load the alternator we use a series of relays switching 20 amps each. Each relay is connected to a coil of 18 ga. nichrome wire immersed in water. One last coil is connected to a PWM for variable current. This system is also under electronic control. The estimated IMEP is used as the input and the relay/PWM system is used as the ouptut of a PID loop that applies a regulated load to the engine.
A video of a preliminary experiment is found on youtube at: youtube
Our website for HHO research: hho-research.org