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Building Tips and technical articles. => 1/2 A building. => Topic started by: John Crocker on August 25, 2007, 07:18:36 PM
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Okay, got somethign weird going on. I think its one of 2 things. Flew the Green Giant with my boy on Fri morning (Low 80's) with no issues. .061 started right up, got in 4 flights (moderate aerobatics), everything was great, never had an issue. Flew in the circle in front of my house yesterday evening (2 flights no areobatics (90 degs)), no issues.
Went flying with a buddy today round lunch (96 degs outside) and the engine just would not peak. If I tried a loop it seemed to lose power. Flew for an hour or so with various planes but eventually could not even get it to start. Engine venturi was so hot it about blistered my thumb. This seems to happen about every time we've flown together lately. Note we have no problems with his Cox Golden bee that we have noticed
So is my buddy just bad luck for me flying or am I getting engine overheating?
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Check the prop---very closely. I had one that twisted a blade to nearly 90d. pitch. Still balanced, no vibration to speak of, but ran as you describe, very sluggish, wouldn't peak, overheated, etc. Changed props and all was well. The twisted blade wasn't even noticeable until I began looking closely trying to figure out what was wrong.
--Ray
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Didn't check the pitch, but did not notice any funny vibration. I forgot to mention I could get it trimmed out perfect before take off. No change in the feel of the pull on the ground. Get it in the air fine to start out, but would wane after 5 or 6 laps, or sometimes die just after takeoff.
My buddy with the Golden Bee keeps telling me I go a POS engine and I'm like, man I never have any problems cept when your around. Aggravating cause I build nicer planes (He goes for nothing but sheet wings (no prob there) but refuses to prep sand, fill in, or even knock the "hairs" off the balsa. They fly, and look okay in the air, but man are they ugly up close. Usually heavy too. Require a real running start to get in the air.
Plus, I can fly circles around him. He's happy with just up and down and maybe a loop or too. He always asks me to fly his planes to see what they can do. Upside down, fig 8's, wingovers, doesn't even care when I crash his planes (which is kinda cool). He's just not comfortable trying it.
So what can I do? Note: I'm running 35% Norvel fuel. 6X2 APC prop. Pressure coming off the muffler to a clunk tank. Have the EXACT same problems with my .061 Wasp and .049 Big Mig Norvel.
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get a golden bee? LL~
Seriously, intermittent problems can be the toughest to solve. Last resort tear the engine and fuel system down and carefully reassemble, not even looking for the problem, just making sure every little thing is right.
In regard to Ray's comment on the prop. Sometimes a prop can get limber or have a limber blade that flattens under load. It'll look fine but won't run fine.
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get a golden bee?
Believe me, the thoughts crossed my mind. Funny thing is he came into it when we were kids cause his older brother had it. That one is for some reason the most consistant small engine I've ever seen.
Will try the tear down though.
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I think it needs more run time. It might be a tighter crank bearing, and that will take a while to ware in. It should not get that hot. Some norvel's had a very close fit between the crank and bearing. It should take care of itself in time. Use a smaller prop to lighten the load and keep the heat down.
The ventri will get hot and you will get a bad run.
Lighten the load on the motor go to a 5 to 5.5 in prop about 4 inches of pitch.
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John, i have a new big mig 049 that gets sluggish half way through the tank, i believe mine just needs more run time. If your having the same problems with 3 engines, i would back down the nitro a little in 95 degree heat. I've been running Omega 25 nitro lately and does fine in the heat.
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I think adding a small amount of castor oil to the fuel could easily brighten your day!!!
Robert
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I think adding a small amount of castor oil to the fuel could easily brighten your day!!!
Robert
Along those lines, I was reading a Cox instruction manual that said using less than 10% castor oil in your fuel would negate their warranty. The total percentage was not mentioned, but most seem to run ~20%.
George
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I don't know if this could be your problem, but a few years ago when I flew a lot of 1/2A CL and RC planes/helis, I had a lot of problems with the Norvel glow plugs. What I would see is that the glow plug element would progressively get a "frosty" look. The "solution" was to lean the motor out a bit. Of course this would lead to sagging later on in the flight. A new plug (expensive!) would usually fix the problem, although usually only for a relatively short time.
Typically I use Sig Champion fuel, 1/2 castor, 1/2 synthetic, with nitro ranging from 15% to 25%. Never really found a fix. I have a lot of friends using the Norvel in 1/2A who didn't seem to suffer this problem like I did. I did typically run pretty high rpm (compared to typical stunt rpms anyway!), >20k using small props (5-4 for 061, cutdown 5-3 with the 049.
Finally went to a Galbreath head and Nelson Plugs to cut down on costs, but at the same time my 1/2A flying dropped off a bit, so I never really figured out what was going on.
But anyway, check the plug element. It should appear shiny, not frosty.
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35% Nitro in a Norvel or AP Wasp is WAY too much, especially in hot weather. I would drop down to 10%! An alternative would be to add several head gaskets to lower the compression. Or some of each.
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...I had a lot of problems with the Norvel glow plugs. What I would see is that the glow plug element would progressively get a "frosty" look. The "solution" was to lean the motor out a bit. Of course this would lead to sagging later on in the flight. A new plug (expensive!) would usually fix the problem, although usually only for a relatively short time.
Alan,
I remember that NORVEL had problems with their plugs. As I remember it part of the cause was that the engines ran cool enough that they would not burn off contaminates. They listed rubber eroding from fuelers, additives in fuel such as anti-foaming agents, detergents, etc. as the cause. I believe this was the plug before the "Freedom Plug". They listed fuels that they tried that worked well with their engines (as well as NORVEL fuels).
Perhaps this may have been part of your problem.
George
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Took clunk tank apart and replaced tubing etc, stopper, etc. Changed fuel to 20/20 Powermaster. Switched to a 5" balanced prop. Still not getting good runs and the engine is still getting hot enough to blister you. Engine is mounted sideways with the piston on the outboard side. When working with it off the lines, I tried pointing the plane up like would happen in a loop, would stall the engine out.
Another funny thing is happening. I cannot get it to break into a rich 4 stroke run. I can take the needle all the way out and its still breaking on a high pitched 2 stroke. I've got the RC throttle wired open, could I be getting too much air in it?
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John, are you working on a norvel with throttle or your ap wasp? I still haven't mounted my ap yet, just never runs through a tank on test bench very steady. I have removed the throttle, adjusted the spray bar, and replaced the plug with a norvel freedom plug, picked up about 1,000 rpm's . Just not a steady run. Will mount on a little home made plane that i know flies well this weekend and see what happens. I just don't seem to have any probs on the norvels, especially after changing them all to the freedom head and plug.
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doesnt matter, both seem to do the same type of things. Could this be the fuel line? I'm using the "small" and it is really tight.
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I really do stand by the additional castor oil theory.
Castor as it gets hotter, polymerizes and becomes a better lubricant far above temps that even synthetic oils can handle.
Check here:
http://modelenginenews.org/faq/index.html#qa5
That article is an eye opener.
Here is another:
http://www.georgiacombat.com/CASTOR_OIL.htm
Robert
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Took clunk tank apart and replaced tubing etc, stopper, etc. Changed fuel to 20/20 Powermaster. Switched to a 5" balanced prop. Still not getting good runs and the engine is still getting hot enough to blister you. Engine is mounted sideways with the piston on the outboard side. When working with it off the lines, I tried pointing the plane up like would happen in a loop, would stall the engine out.
Another funny thing is happening. I cannot get it to break into a rich 4 stroke run. I can take the needle all the way out and its still breaking on a high pitched 2 stroke. I've got the RC throttle wired open, could I be getting too much air in it?
I got to wonder if you don't have more than one issue.
What do you mean breaking. breaking usually means switching. If it won't go rich witth the needle out, there is a restriction somewhere, plugged vent, or filter. Look for junk in the needle valve and spray bar.
It should not get that hot, it is too lean, something is too tight or not enough oil. Castor is good.
When it quits when the nose is up, is it fuel stravation or the motor over heating? I point the nose up, then peak out the motor, several clicks rich of the peak.
What tank are you using?
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John, a few weeks ago i was playing around with some different tanks and had all the same symptoms . I was amazed at the difference moving the tank an inch or two closer to the engine would make sometimes. I tried this theory again last night , tank 4 inches away and engine would quit when turned up, moved same tank 2 inches closer and engine would perform and pull fuel correctly. I have read posts that say that shouldn't matter , but I for one, beg to differ!
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doesnt matter, both seem to do the same type of things. Could this be the fuel line? I'm using the "small" and it is really tight.
Just noticed that you mention having the problem on both the AP and the NORVEL. Assuming you are not switching parts, the problem is probably not the engine.
Switch tanks. You may have a small hole or crack in the pickup tube that is sucking part air and part fuel so that you have a lean mix BEFORE it gets to the needle. This hole is probably uncovered partway through the run.
If this is the case, you can just replace the tubing.
George
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Everything I am readnig here points me to a "too lean" condition where the engine is sagging.
If the needle is out and it will not richen up, that has to be the problem..................
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Woohoo, I figured it out (at least on the .061) y1
Holy crap what a bunch of troubleshooting. Tried the head shims, nope. Tried bigger line and smaller line, nope. Finally stripped the whole d@mn thing down.
Found a sprig of grass in the intake nozzle. Blew it out with a syringe.
Removed the wire securing the fuel hose, little pinhole under it. trimmed and used mini zip tie in its place. Got much better but still was not perfect
Suddenly noticed, hmm venturi feels a little loose, weird. I had to replace the screws holding it in a couple days after getting it, they vibrated loose. New screws had just a hairs worth of play in them. Put a little CA on the screw, let it cure and voila! Full peak performance, just got back in from flying in the culdesac.
I HATE issues caused by multiple problems. Makes trouble shooting a biatch.