|23 Nov 1999: First RUN! Yahoo!
Unless you can count 1 second bursts as "runs", the engine ran successfully today, sustained, for the first time. While there are still outstanding ignition and carburetion problems, the run was successful. Hopefully, thanks to the gang at RCM, especially Peter Logghe, Don Forman, Ron Colonna, Brian Whatcott, and others, these will be ironed out soon.
Note the minimal setup for the first run... the oil tank is an open bottle of 30wt oil. The fuel tank is an old model airplane tank filled with gas and a fuel line inserted into the tank. Electrically, the coil and TIM module can barely be seen to the left. I used a variable DC power supply to drive the spark.
The saga of getting the engine to this point is long and sad. The first carb I tried was a massive Briggs & Stratten carb from a lawn mower. Bore on this carb was .625. It didn't look too big, but I was assured by Ron Colonna that it was in fact ridiculously massive. Next carb was a Walbro from a weed whacker, also too big. Neither of these was drawing any fuel at all. The engine was cranking off of priming fuel, but was unable to sustain. In the meantime, frustratingly, I was burning out Hall effect IC's and TIM4 modules like candy. A lot of it was not having the coil clamped via a big zener diode, so that while the distributor was being massaged to function properly, the energy from the HV coil, needing somewhere to go, was blowing out through the Hall IC and cookin it in nothing flat. Worst of all, in flipping the prop through 2 days ago, I severly jammed the fingers on my right hand after following through into the mounting stand. The pain was so severe I couldn't even slowly take the prop through compression with my right hand, and my left was so uncoordinated, I couldn't give it the sharp flip it needed.. A friend saved the day with a massive model airplane starter which cranks (albeit barely) the engine.
So depression had set in somewhat. I knew the engine would run, it was just a matter of getting a properly sized carb mounted and an ignition system that wouldn't crump after just a few bursts. My good buddy Paul Stelly saved the day with the loan of a K&B .60-sized model engine carb. Amazingly, this carb might even be too big. Even though my engine is 8.0 C.I., the bore of the carb should be ~ .25 to .35 the diameter of a piston, so I am looking at a carb bore of 1/4 to 3/8" dia. This rule holds true regardless of the number of cylinders! Go figure. So I quickly (but temporarily) mounted this carb on a brass plate, ugly as sin but functional. The fuel tank placement was a bit critical... too low and the fuel simply wouldn't draw, even with my finger over the air intake. Too high and it all basically drained via a siphoning action. The answer will be in the design of a float assembly which can be adapted to an OS carb or similar. The burned out hall IC was replaced again, a very tedious affair. Everything seemed a go.
With aching fingers but high hopes, I set up the engine for another run. Once again it was prime, crank, ignition, and 1 second of running. I began opening the needle valve more and more, and kept trying. I think in the end it was the electric starter which made the difference... there is nothing quite like a vigorous cranking to get the fuel/air mix where it needs to go. Prime, crank, VROOM, die, prime, crank, VROOM... WOW, its sustaining! Quick, work the needle valve! At this point I threw my left ring finger into the prop, and took a wicked shot to the fingernail. My mind shrieked, "Get the needle valve you fool, before it dies again!"
Some careful work with the needle valve produced an ugly but sustained, medium throttle run. After maybe 1 minute, the engine died. Checking the heads for heat, to my utter dismay I found that the entire run had been powered by only 3 of the 9 cylinders... 6 were cool to the touch. Depression set in again. Any engine problem can be narrowed down to 3 items... fuel, spark, compression, or any combination of these. I knew I was now getting fuel, and compression had been checked and was adequate. It had to be weak ignition. I cranked the engine again, this time getting a pretty decent light-off right away, as the mixture was finally close to where it needed to be. This time, though, I began slowly increasing the voltage to the coil, working my way up from 6V. As I dialed in the voltage, I could hear the cylinders begin to catch one by one. At 10 volts or so, the engine was roaring with that extremely cool radial sound, amazingly replicated even with this small engine. There is no mistaking the sound of a radial... it has a note and signiature all of its own, true music. I slowly manipulated the throttle, and was able to produce a sweet idle.
My only problem now was excess oil-flow. The plans call for a needle valve to control oil flow into the engine from the external oil tank. My temporary setup today used only simple tubes without any kind of flow restriction. I was counting upon the greater capacity of the scavenge pump to keep the lower crankcase area free of oil. Sadly, it was unable to keep up with the pressure pump, and I knew it for a fact when the engine began to blow oil out of the front main bearing. But otherwise all went well, with all 9 cylinders firing!
Yes, I actually executed the "happy dance" in my driveway. After two years of work, I couldn't care less what the neighbors thought! The next step is a more permanent carb mounting, oil and fuel plumbing, and an ignition system with a bit more protection in it.
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