Xave7

Hi, i had a quick question about some engine troubles I've been having. I'm the president of the Aerospace Design Team over here at Northern Illinois University. We got a new .61 OS FX engine last year to stick in our plane, but have been having trouble with it's throttling. On our test stand, it works perfect; starts clean and runs at a very stable rpm. However, whenever we stick in in our plane, we can't seem to get past half throttle without the engine cutting off. If we keep the glow plug starter on it, it works fine even in the plane, but as soon as we take it off it'll idle fine, but if we attempt to throttle up it dies again. I was just wondering if you have ever encountered something like this before. We've tried replacing the spark plugs, bought new fuel (since ours was nearly 3 years old), and even cleaned out the carb. Currently using a 12x8 propeller.

flyinwalenda

My Feedback: (5)

A 12x6 prop is usually a good one to use after the engine is broke-in.
Did you follow the break-in procedures on the test stand?
You say you are flying the plane or attempting to fly the plane and the engine cuts  out at throttle up on the runway?
Did you adjust the high speed needle valve for maximum rpm's before the rpms start to fall-off? At that point you need to open the needle valve some more to create a rich condition as it's still breaking-in. When you have the high speed needle set as above the open the throttle to full and CAREFULLY with a good handhold, lift the plane up and point the nose/engine up. The rpm's should not decrease . If they do cut the throttle, put the plane back on it's wheels and open the high speed needle some more and try again. What you want to achieve is the rpm's to remain constant or better yet increase a bit with the nose up versus level.
After that is set you need to check the low speed and with the engine at idle you quickly open the throttle and the engine may stumble a little but not to the point of blowing smoke out of the exhaust or killing the engine due to fuel starvation. iIf the engine stumbles a little then leave it until the engine is fully broke-in then you can learn how to fine-tune the low speed needle.

Gray Beard

My Feedback: (-1)

There could be a few problems but it sounds like it is too lean. You need to balance the low and high end. The fuel tank can also be located/installed incorrectly. Doing a search here on RCU on how to tune an engine should pull up a lot of pages on the subject. I know John Buckner has posted about the how to several times over the years. There is also a glow engine forum here on RCU with step by step instructions. It's another sub forum in Giant scale and shows up in the gas engine forum. There is even OS factory support.
If all else fails then taking the plane out to a local club you can find someone to teach you how to tune with hands on.

jaka

Hi!
Use a 12x6 prop and set it a little richer!

Propworn

My Feedback: (3)

You are building for the Regular Class good for you. Use a McCoy MC14 performance plug (glo plug not spark plug).

First you need to get the centerline of the fuel tank as close to the centerline of the spray bar in the carb. Next try and do all your tuning with just over a half tank. Gravity will affect fuel feed. The tank should be as close to the engine as possible. If the tank is at a different level on the test stand than in the plane this may be part of your problem. If you have the engine inside a cowl on the plane and not on the stand this too might contribute to your problems.

Don't worry to much about breaking an engine in for this application. Run the sh*t out of it peak rpm after the first tank you should not be concerned with longevity. Listen to the rpms we get in the videos spinning fine pitch larger diameter props giving greater tractive effort to get the thing moving.

You have moved the needles around on the carb and need to start fresh. Back both the low and high speed needles out. Place a 6 inch piece of fuel tubing on the inlet nipple. Use a 1/16 wire or drill and put in the carb opening and gently close the carb until the barrel just holds the wire or drill. The carb is now held open at 1/16. Blow through the tube while slowly turning in the low speed needle until the passing air stops then back out until you can just detect air passing through. Now turn in the high speed gently until it stops then open 2 complete turns. This is your initial setting. Remove the wire/drill. Start the engine and open the throttle until wide open then adjust the high speed needle until max rpm is reached. To set the low end let the engine idle then open the throttle full at the same rate as the servo would move it. If the engine quits you have to determine if it is to lean or to rich. Repeat with glo driver attached if it still quits its to lean if it bogs then picks up or runs through transition the low speed is to rich try turning it in a 1/4 turn. Open it a 1/4 turn if it just outright quits. You will have to repeat this until the engine will transition through to wide open without the glo driver attached. Once this happens keep adjusting the low speed no more than a screw driver blade width at a time until best transition is reached. Some here will tell you the high speed should be richened until an rpm drop is detected but they might not understand the requirements of the competition. You don't need long time durability nor fuel feed stability through aerobatics you need max rpm for tractive effort for less than a dozen short flights. Wring it out for max output. You might want to try a 14 X 4 APC or better yet a 13 X 4 if you can find or make one. Remember there are no rules as to using an altered prop. Pay attention to the tip profile as most of your output happens at the tip. APC props for that size have the best performance numbers. Balancing the prop will give a few more rpm as well.

One more thing is the Magnum engine turns the same prop a little bit faster than the OS. This was consistant testing two engines of each brand. Dynamic testing in the wind tunel also showed slightly better performance with the Magnum engines at airspeeds through 50 mph

Dennis

[youtube]http://www.youtube.com/watch?v=fLXF9SOoGAY[/youtube]

[youtube]http://www.youtube.com/watch?v=mcJB8A3xbxU[/youtube]


[youtube]http://www.youtube.com/watch?v=TiTDtcITTSo[/youtube]

Flying wing 2005 Open Class

DGrant

My Feedback: (4)

Alot of good info here... I'm thinking if it worked as it should on the test stand... then malfunctioned in the plane.. it might be in the fuel-supply sysytem in the plane.. IE fuel-tank, tubing, tank position, etc... and I think someone mentioned(maybe)... the fuel tank can't be extremely far from the engine.. and has to be near or on the center-line of the engine.. ball-park distance would about 4"-6" max from the engine.. and nearly inline with the carb.. If you're trying to get the engine to draw fuel from any further out.. you might want to think about a pump, or a device to help deliver the fuel.

These engines are usually VERY reliable, and once set don't need to be fiddled with much at all. Another idea is.. if it works fine on the test stand and then dies in the plane... take the whole tank/line and all out of the plane.. and run that on the test stand too. Good luck.

Taurus Flyer

Shane,
I was interested in the Northern Illinois University, to find some photographs or other info about your activities.
Is the "Aerospace Design Team" a new group or is the name a little bit different?

Taurus Flyer

Warbird40

My Feedback: (24)

I had a similar problem with a Rossi 45.. it turned out to be a few specks of dirt in the tank of the used plane I installed it in..flushed it out and its a screamer now.

hugger-4641

My Feedback: (6)

A few questions and my personal recommendations for each:

What kind of glow plug? ( I use an O.S #6 Hot, used to be called A-3, until engine is tuned and running good, then you can switch to colder plug like #8)
What kind of fuel? (tuning will be easier with a 10% to 15% nitro content, I personally prefer OMEGA)
Was the engine broke in? (glow engines require a breakin process to allow the piston/rings and other components to seat properly, mixture settings and rpm will not stabilize until breakin is complete)
What RPM is the engine turning while running at full throttle? (With a 12x8 prop you should get at about 12,000 rpm, mine will peak out to about 12,800, then I richen the mixture to drop to 12,300)
How hot is the engine after running full throttle? (you should be able to touch the muffler within a minute of shutting off the engine, otherwise it is probably running too lean and getting too hot)

jester_s1

So you are losing power as you advance the throttle, leading to the engine cutting out. You've changed glow plugs and fuel, so you know they are good. I'll ask a question that is notoriously hard to answer on the internet, but it's important. What does the engine sound like when it dies? I'll offer the three most common choices: a strong exhaust note that just suddenly quits, a gurgling, weak sort of sound that slowly goes down until it quits, or an erratic sound that sounds strong and weak a time or two before it quits. Option 1 is indicative of a lean condition 99% of the time. That may be a needle setting issue, but I'd suspect bad fuel lines or something wrong with the tank setup first since you are getting good runs on the test stand. Option 2 is an over rich condition which usually won't cause the engine to quit, but if the over rich condition is compensating for an air leak it sometimes will. Option 3 (or really anything erratic) is a dead giveaway for an air leak. The common culprits there are the carb o ring, the backplate, the front bearing, loose head bolts (rare), or even a cracked case. It's possible you have such an issue but the test stand fuel supply is good enough to let the engine run well enough anyway.

One other thing to consider is that if you are over propping the engine (and you are) you're going to get deadsticks if you're even a little bit lean. The absolute toughest situation for a glow engine to handle is accelerating from idle to full throttle quickly. The intake vacuum goes down reducing fuel draw, the RPM's take a little while to catch up and raise the vacuum, and the big rush of air leans out the mix even further. With an overpropped engine that struggles to accelerate, you can get a lean condition even if you are set a little rich on the top end.

Bozarth

My Feedback: (15)

Is there a particular symptom of improper break-in procedures?

Kurt

Propworn

My Feedback: (3)

Everyone goes on at length about break in procedures. Everyone has their own procedure they claim they have been using for years. I am one of them but I am a hold out from many years of dicking with engines. Today’s engine seems to need little or no break in before using. I say this because if you observe the arfs brought to the field most are started tuned for dependability then flown. As they get flown and the running time builds up they start easier, seem to develop more power and run better. To me this is either breaking in while in use or the operators familiarity and confidence in the adjustment of his power plant. Either way most times it is done while enjoying the airplane in flight. I would not put to much emphasis on spending time breaking modern engines in on the test stand or during ground running. Get it adjusted so it will run though a full tank reliably and fly it. Keep your first few flights high and close enough to easily make it back to the field in the event of a dead stick or run problems. Once confidence in the engine, airframe and your abilities develop then go ahead and have at it and enjoy.

Dennis

Taurus Flyer

No Dennis, you wrote:

Everyone goes on at length about break in procedures.

Not me!!!!
http://www.rcuniverse.com/forum/fb.asp?m=11436366

I am OS Max 61 FX user myself but I first want to see some background information of the Aerospace Design Team of Shane,
My information will be related to the know how of the Team!!

Taurus Flyer

flyinwalenda

My Feedback: (5)

Trying to establish how many times it has been ran on the test stand or if they know what break-in means. An engine breaking-in runs worse and will shut down more often than an engine that has been properly broke-in.
All these questions and suggestions and not a peep from the OP !

thailazer

When it is in the plane, look at the fuel line to the carb to see if you have bubbles forming in it when you are throttling up. If so, vibration is causing a loose throttle linkage to move the carb barrel back and forth at a high rate creating an air pump at the needle. This is a long shot but it is the toughest thing that I ever had happen.

Propworn

My Feedback: (3)

I have been the pilot for the University since 2005 everything from micro thru advanced class. One year I had 2 micro teams, one regular and one advanced all at the same time. Most of the teams this is their first contact with any RC aircraft. Read the first post where he calls a glo plug incorrectly a spark plug. This should give you an indication of the level of experience. They are open and eager learners and will adapt very quickly if you give them a chance. I have enjoyed my time with the students and at the competitions immensely and have made many new friends’ from around the world. Each year the same pilots show up with their new teams and it’s nice to see and talk with them. If you ever get a chance to work and fly for one of these teams I highly recommend you give it a shot. I even invite them into my shop to use my CNC equipment to cut out their parts. This is something they also have to learn from scratch but they pick it up very quickly.

[youtube]http://www.youtube.com/watch?v=5Z9pZ_MZG7A[/youtube]

[youtube]http://www.youtube.com/watch?v=zzoSjeWPkCk[/youtube]

CafeenMan

I didn't read all the responses so maybe this has been covered but I'd bet that the problem is the fuel feed. A line is kinked, has a hole or a cut in it or something of that nature.

Pull out the tank and empty all fuel from it.

Hold it up vertically to a good back-light and see if the clunk hangs free. If the clunk is kinked then you can't draw fuel. It may be only slightly kinked and can feed at low throttle but not pass enough fuel at full throttle.

When held vertically the clunk should clear the back of the tank about about 1/4" and be able to swing to all four walls of the tank.

Are any of the brass tubes kinked or cracked at a bend?

Did you check your tank for leaks before installing it? Put it under water with two lines on it. Fold over one line to seal it. Blow in the other line to put pressure in the tank. If you see bubbles in the water something is leaking.

Are the holes in the firewall for the fuel tubes smooth? If they are rough or splintered they may be cutting into your fuel lines.

Propworn

My Feedback: (3)

http://forums.sae.org/access/dispatc...roDesign09.pdf

[youtube]http://www.youtube.com/watch?v=OhgEN2tOHsc[/youtube]

Lot of info here if your interested
http://students.sae.org/competitions/aerodesign/

[youtube]http://www.youtube.com/watch?v=MbLbTRkji9c[/youtube]

[youtube]http://www.youtube.com/watch?v=wsafPhz_ly8[/youtube]

Taurus Flyer

Do you see Propworn, Shane doen't show up to answer my question!
What could be the reason of that?
Let me tell you, I am not surprized just curious, who is that thread starter?

Cees

hugger-4641

My Feedback: (6)

Well, he joined RCU in 2011 and didn't make his first post until this thread, so I'm guessing he doesn't get on here everyday. So what is your point, that he's not responding for some hidden reason?

CafeenMan

Xave - did you try any of the things I suggested?

Propworn

My Feedback: (3)

I should have been more specific in that I am the pilot for the University of Windsor in Windsor Ontario Canada. My experience with these students is that they know almost nothing when they start except what may have been passed on from the previous years if they bother to look at it. They have an infinite belief that they can find all the answers by just asking on the internet. Experience is not really necessary in their mind. How little they know. Book smart does not equal practical smart that comes with learning from all our mistakes. They have probably joined every forum and news group having to do with RC aircraft and asked the same or similar question from all of them. Once they have a solution I doubt you will hear another thing from them. Of the 80 to 100 students I have had under my wing not one of them are interested in anything RC beyond the project. As long as the project is under way they will engage in conversation to do with the project at hand after I doubt you would be able to stir much interest at all. It’s just the way it is.

Dennis

CafeenMan

Propworn - Every year I get requests from students doing these sorts of tasks asking me to design the plane for them. Nothing of that sort this year but my response is always the same - sorry.

jester_s1

I've volunteered for the SAE contest held in Fort Worth a couple of times and can vouch than many of the students have no use for learning how to pilot an RC aircraft. Their designs reflect their lack of knowledge too. Lots of designs show up that are designed to fly well in a straight line yet the contest flight is mostly turning. Few know how to do a proper takeoff, and since lots of the best lifting designs have very unforgiving stall characteristics I see lots of planes crash as the pilot does a gun and jerk takeoff trying to get as much altitude as possible as fast as possible. And lots of the designs simply don't have stability in mind at all, so you see weird reactions to cross wind flight and planes that are hard to recover from stalls (make that impossible for an inexperienced pilot). If guys who are doing these contests would just take one day to come out to a club field and get a few flights on a trainer plane they could go into it with such better perspectives on building practical designs that are pilot friendly and will make successful flights.

Taurus Flyer

My point is, I wasn't asking a student but "the president of the Aerospace Design Team over here at Northern Illinois University.", and for that case I expected an answer within a few days.
No answer, no action. Simple is that.



Cees