Here is a list of all the postings johan bekaert has made in our forums. Click on a thread name to jump to the thread.
|Thread: Super Scale Avro Anson|
Good evening all, I just finished an Avro Anson, from a Duncan Hutson plan. It may not be to perfect scale, but to me it looks allright. It's powerplant is 2 OS FS48surpass. The dry operating weight came out a bit more than hoped for: 6,200kg (about 13 lbs), and that includes a horrible 350 grams of lead in the nose in order to get the cg right.
The maiden flight is approaching fast, and I have a bit of a confidence lapse. I would love to get some practical info from people who have built and flown it: weight? controls deflection? Correct cg position? (on the Hutson plan it looks exagerated forward in my opinion...) Any further hints and tips? Thank you much!
|Thread: ASP FS 180AR|
Yeah but it smells so nice
I think it's solved!!! I crosschecked everything everybody suggested here, but all seemed as it should be. I started thinking about the fuel and the smoke the engine produced. Nearly choked me. Jon suggested not to use castor fuel, so I went to the modelshop and bought a can of Rapicon fuel.And believe it or not, ...the engine runs wel now.
I have been mixing my own fuel for years now, all my engines run on it, even an OS Wankel. But ok, it's been winter, and the can of fuel I used was mixed last summer. Maybe it was a bit off, maybe the oil a bit sunken to the bottom? Anyway, the ASP runs all the way to full throttle now, still needs some tweaking but it looks promising. Still no handstarting though. Graham mentionned that the tube from the crankshaft to the carb may cause the fuel blow back when the airinlet is blocked with a finger. Maybe that's why the ASP, unlike my OS'es and Saito's, doesn't have this rubber clapet to block the inlet when the engine is inside a cowl.
as soon as I have a bit of spare time again, some more testruns, and hopefully in a few weeks airborne in my brandnew scratchbuilt Marchetti SF260!!!
Thanks to all, Jo
back home and I've ran it again. I have thoroughly cleaned the carburetor and all fuel pipes. Starting is basically the same: finger over the carb makes it suck fuel but blows it back somewhat after the compression, however spinning it with an electric starter makes it draw fuel, even without blocking the carb. I let it run, quite rich, for 15 minutes. Produces a lot of smoke; it doesn't like my castor oil? (I'm oldfashionned. I use homebrew half castor half synthetic, 5% nitro) Going to full throttle: found out it's only possible with exhaust pressure in the tank (which I didn't do before). But it does it; albeit not full power. It doesn't stop abruptly (like it did before) nor sputters with smoke; it simply loses rpm. Throttling back keeps it alive. Ah wel: it's an improvement. Give it some more breaking in; might end up fine, fingers crossed.
Just wished I could start it by hand: crancking such a big engine one or two times with my electric starter makes my poor field battery need some defibrilating on the charger...
Keep you informed, Jo
Thanks for the prompt reply gentlemen!
It's fitted with an OS F plug, and a master airscrew 16x8, fuel has 5%. Thus all according to specs. Plumbing (feed and vent line) is ok, the valve move ok and their clearance is ok, compression (when primed) is ok. I have had quite a few OS and Saito 4strokes, but this one baffles me: With the needle at 1 1/2 turns out, finger on the carb, turning it over draws fuel, but after 1 flick the fuel simply returns to the tank. As a matter of fact, the finger on the carb feels it suck, but when the engine passes compression, you actually feel it blow! Hence the air bubbles in the tank... It's on a test bench, so I can see through the tank and fuel line. Do these large engines perhaps have anticipated opening of the inlet valve? I'll take the advice and run a couple of tanks through it, and have a look at the idle needle. Maybe give the carby a complete cleaning?
I have bought an ASP180 fourstroke from Hobby King (I know, I know...) It spent some time in my drawer but I recently put it on a testbench. Hand starting was impossible. You could see that it didn't draw fuel. Very strange: when turning the prop over, once past compression you actually saw airbubbles escape in the fuel tank!! Nevertheless, tried to start with an electric starter. Even then, whilst applying the starter I had to put my finger on the carb for a second or so (not the safest thing to do with a 30cc!!) before it drew fuel and started. It then ran ok, although I didn't have a clue anymore about the position of the needle. So after 30 seconds I went to full throttle but the engine died. After that I started it 4-5 times; each time the same tricky starting procedure and dying before reaching full throttle, no matter what needle setting. HELP! This is far from my first fourstroke, but now I'm out of ideas. Anybody, please?
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