jbeech
rrAdvertiser
Location: Sanford, FL (Orlando area)
| gilliraldi said . . . "I am sure I have one of the needle valves wrong - I am just using the factory settings."
Oh my God, this kind of things scares me! How do you know somebody didn't have the engine in their hands before you got it and twisted the needle valve? In case you didn't realize it, idiots love to adjust the needle valve of any engine in their hands . . . it's the first thing they touch after first opening and closing the carb a few times. Hence, the factory settings are worthless. Don't believe me? Observe the next clueless individual you have the opportunity to see as he handles a brand new engine at the local hobby shop, you're in for an eye opening experience.
Anyway, for what follows, please do not take offense because I am going to assume you don't know squat about engines since I cannot assume whomever reads this "does" know anything. Hence, don't go getting your panties in a wad just because you think I'm talking down to you. If what follows is all old hat, then go find another thread to read.
Here's what I advise.
1. Leave the cam-screw alone, or if you think it's been screwed around with (idiots can't usually mess that one up bacause no hobby dealer worth his salt will let an idiot handle a new engine and a screw driver at the same time), then set it in the middle of the range.
2. High Speed Mixture Screw - the main needle valve - CW leans it and CCW richens it. This works just like the faucet in a sink. Turn CW and less fuel comes through the needle to the venturi, OK?
Start with 2-turns out from closed. Closed is when it just bottoms out. With the carb barrel wide open, put a piece of fuel tubing on the carb nipple and blow air through it as you close the needle valve and you'll see what I mean. DO NOT tighten the needle closed as you're just going to deform the needle's tip and put a ridge in it.
Now, suppose you have a tin-ear and have no clue what too rich or too lean is.
One thing you can do is buy my aboutENGINES DVD. Some may view this as a shameless plug (and I suppose technically it is), but the fact is you really need to hear some things, and the difference between too rich and too lean is one of those things. I can explain it until I'm blue in the face but until you hear the difference for yourself you're gonna be clueless. Unfortunately, unlike with a fixed-wing model which you can hold on the ground and adjust the main needle while you listen for it being "right", and perform a pinch test, you can't do this with a helicopter. So what's a noob to do? Here's the link to the DVD (and one of the engines we break in is the OS 50SX-H). Anyway, I explain about fuel, the engine, and the right prop to use, etc.
http://www.genesishobby.com/Product...ductCode=RCB003
Anyway, the DVD and what I explain below is the best I can think of to help you until you can get an experienced modeler to assist.
First, make sure the max pitch on the model is about 10.5°, that you've set hover pitch to around 5.5°, and that low end pitch (if you're learning to hover is about -1°), for everybody else, low end pitch is about -4.5°.
Second, wide open throttle occurs at max pitch. At idle, the carb barrel opening is about the thickness of a medium sewing needle (or maybe a tad more). Hover throttle is about 50% open. Once upon a time this would have been 60% but with the strength of the Hyper, it is usually 45-50% throttle opening. Half throttle is close enough for our purposes.
Next, lift the model into a hover. With the needle 2-turns open, there should be plenty of smoke (lots of it really) and the model should have lifted, but not leapt into the air - presuming it's a new engine and a new model at the same time (a really bad idea). Then land, open the needle 1/16th of a turn (CCW) and lift into a hover again. What we're looking for is when the needle is so far open that the engine is so rich the heli can barely stagger into the air. Once you identify that condition, close the needle 1/8th of a turn and start to fly with it that way.
Why do this? So that we don't cook the engine, score the sleeve, and generally create a 200 dollar piece of junk by running the engine in too lean from the get go, understand? Anyway, run it this way for a gallon or even two. Trust me, the engine will go through fuel like crazy but it'll be running cool and breaking in nice. plenty of time to worry about fuel economy later. Anyway, if you're learning to hover, you can do everything you need to do at 1" of altitude. Oh, here's another shameless plug. Try to find a copy of my Hover video. Unfortunately, it's out of production since I want to update it to DVD and I haven't been able to since Hurricane Charlie wiped out the building for my television production studio (visit my gallery for pictures of that little fiasco). Meanwhile, here's the link to the Hover video so you know what you're searching for.
http://www.modelsport.com/rcb/rcb002.htm
Look, you're faaaaar better off to break the engine in on a test stand before putting it into your new heli. Why? Because then you're just messing around with one new thing at a time, not a hew engine AND a new helicopter all at the same time.
My personal engine, well broken in, has the main needle opened to about 1-1/2 turns. But I don't run my engine as lean as I can because the little extra bit of power isn't worth the risk to me of slagging a perfectly good engine in the eventuality a pressure line comes off or some such. I like a little margin for error.
As for glow plugs, either an Enya #3 or #4, or an OS A8 work well for me. I prefer Wildcat 30% fuel, but their 15% works just fine, especially when you're just learning! Heck, with the power of the Hyper, go cheap and use 5% nitro fuel - and don't buy into the BS that it has to be helicopter fuel. For what you're doing, any conventional model airplane fuel (using all-synthetic oil) will be just fine. Believe me, with that Hyper engine, running 30% nitro is just taking money and putting a match to it for all the good it'll do you while you're learning to hover . . . and because it's a ringed engine, it won't hurt it to switch fuels (shouldn't do this with an ABC engine unless you kow what you're doing and have a reason to switch.
As an aside, with an ABC engine if the compression ain't what it used to be, you can operate it at a different temperature by running a different nitro content and thereby extend the life of that engine. This is an old pylon racer's trick for when you take an engine which is a little too worn to be competitive, and not worth rebuilding because a newer design has come along and obsoleted, and you're really just going to re-purpose the engine for sport-use. A sign an engine is worn is when the idle goes away (and I mean a properly adjusted engine, not your engine gilliraldi), anyway, I digress.
Don't believe me about low nitro fuel? Eyeball the video on the Audacity website of Mitch Shreeve flying the heck out of a Tiger 50 using an OS Max 46FX-H on 15% nitro and woodies plus an el cheapo 2-pc muffler we offer. Then tell me you need to burn 30% nitro whilst learing to hover!
Last thing. Don't touch the low-end needle until the engine is fully broken in and adjusted. Why not? Beacause a change to the high speed needle will also affect the low end mixture slightly as well. Start adjusting both befre the high end mixture is set and you'll end up chasing your tail. Hmmm, that remoinds me of the noob who was adjusting the main needle valve of his engine whilst all he could do was hover. Along comes an experienced flier (but not soo experiencd with the foibles of a noob) and jerked it into forward flight and almost immediately the engine went lean and flamed out, so he does an emergency auto and they spend half an hour trying to figure out what's worng with the engine. Experienced helicopter modelers know the noob had the engine too lean from worrying about a perfect mixture and using the main needle whilst at part throttle, i.e. hovering. Duh!
Anyway, that's my 2¢
John Beech - GM (and janitor)
Audacity Models |
