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Engine basics => Engine set up tips => Topic started by: taildragger-j3 on November 04, 2007, 09:08:41 AM
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I've put an old/new Fox profile tank on my new Ringmaster. It was the same tank that was on my old "Yellow Jacket" that I re-kitted at the Ringmaster Roundup last spring. It appears to be in good shape, no leaks or dents, etc. When I cranked up my Greenhead .29 it ran just fine. As long as I'm flying level, (upright or inverted) or pulling +G's everything is ok, but when I tried to go outside (-G's) the engine dies.
I raised the tank up about 1/4" above the venturi and flew my RM again this week-end It still ran GREAT in level flight upright or inverted. Still does good when I pull + Gs but conked out when went outside. In fact I had a rather abrupt arrival after trying to come out of inverted flight with a reverse wing over. I've patched up the plane, but I'm bumfuzzled about why it's doing this. I think I'm going to try a "clunk" tank and see if it makes any difference.
Here's a picture of the tank on my old Ringmaster
Could there be something about the engine, fuel line, or anything else that might be making it die when it pulls -Gs?
HEEELLLPPP!
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Try changing the fuel and vent tubing. Tie the fuel feed line down so it can't flop around. Make the fuel feed line as short as possible to prevent flopping around.
Try tieing the ends of the fuel line to the metal tubing and needle body to prevent any possibility of getting an air leak at that point.
Try changing thr glow plug.
Bigiron
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Had what may be a brainstorm. Here's a picture of how the tank was originally mounted before I raised it about 1/4 inch. If you look at the picture, you'll see that the feed line comes out of the bottom of the ridge that runs along the tank, but the fuel line has to S-turn to get to the inlet on the top of this old Torp. Could the centrifugal force from the outside loop be keeping the fuel from traveling what would then be "up" the feed line into the fuel tubing???
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I'd suggest popping the backplate of your tank and having a look inside. Set it on top of the stove and use an oven mitt and pair of needle noses to get the back off when the solder melts. Put the backplate back on using the same technique. Do this when your wife is not at home.
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It appears that the front of the tank is crunched. Might be a good idea to pressure check it?
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I am thinking something has been missed here. You say it quits on out side maneuvers and you raised the tank and it did not help. I have a plane with an Enya 35 on it that the tank is a 1/4 inch below the center line of the engine to keep it from going lean and dieing on outsides. I also have the needle valve positioned so the nipple is on the lower side of the plane. I must also say it was going rich with the tank mounted above the center of the engine. Several people didn't beleive me until they seen the plane/engine setup. I would suggest changing your needle valve assembly and lowering your tank. Have fun, DOC Holliday
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Mine did that this weekend it was a pinhole in the fuel line that opened up during an outside manuever.
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I have pressure checked the tank. No leaks. The fuel like is certainly a possibility. I'll change it out.
Doc, I've never heard of LOWERING the tank, but I guess I can give it a try. On this old Torp, I like having the needle away from the exhaust, but it is a challenge to adjust down there. I'm sure K&B had some reason for putting the exhaust on the left side of the engine, but I don't know what it was. I'll try swapping the NVA over and see if that helps, too.
Any other suggestions gratefully accepted.
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Raising and lowering the tank is done to use the G-loads from the turns that affect the fuel feed. An outside loop exerts load from Gs toward the top of the airplane, making fuel harder to draw. Makes sense to me that a higher tank would go leaner in outsides.
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Could be the plug. A bad plug will foul with an overly rich mixture. Depending upon the ports and what not, some engines break lean or rich inside or outside. If you're going slightly rich outside a bad plug will foul.
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I'm sure K&B had some reason for putting the exhaust on the left side of the engine, but I don't know what it was.
Many older engines had the exhaust on the 'wrong' side of the engine. Of course back then it wasn't uncommon for people to fly the other direction (clockwise). When a profile is oriented for clockwise flight, with the engine mounted on the outboard side of the fuselage, the wrong exhaust suddenly points the right direction.
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I'd pull the tank off including all the tubing and pressurize the entire system underwater. A sink and fuel bulb or syringe should do it. I've had tanks that appeared to be sound when tested in the field. Seemed to stay pressurized. When checked at home though in a sink lo and behold bubbles. Soldering up the small seam crack solved a problem I was having.
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Raising and lowering the tank is done to use the G-loads from the turns that affect the fuel feed. An outside loop exerts load from Gs toward the top of the airplane, making fuel harder to draw.
??? Sorry. This is a new one on me.
Raising and lowering the tank is done to get a consistent engine run and lap time either inverted or upright. When the tank is on the centerline of the venturi, some engines will run too rich while inverted. That is why we have to raise the tank on most profiles to balance the run.
The accelleration/decelleration (G-load) through the turns may cause unporting when the tank is almost empty, but it's not a reason to raise or lower the tank. If you experience this problem, you should shim the aft end of the tank away from the fuselage. This extra angle helps keep the remaining fuel in place, especially during the cloverleaf. VD~
My .02 - gained via costly experience. n~ n~
Ron
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The accelleration/decelleration (G-load) through the turns may cause unporting when the tank is almost empty, but it's not a reason to raise or lower the tank. If you experience this problem, you should shim the aft end of the tank away from the fuselage. This extra angle helps keep the remaining fuel in place, especially during the cloverleaf. Devil
My .02 - gained via costly experience.
Ron
I was thinking the same thing, so I put a 1/8" shim at the back of the tank and it still died with an almost full tank (less than 5 laps flown). I've got a Sullivan 4 oz slant front "clunk" tank I think I'm going to try. It will just fit between the LE & the engine.
I REALLY appreciate all the input I've received on this. You guys are great.
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I think the clunk tank will cure it. You may also try a standard rectangle type tank on suction. If you can find one, a chicken hopper type tank is also worth a try. (Don't ask me why they are called that) n~. I have never had any luck at all with the style of tank you show mounted and think that may very well be the problem. Good Luck 8)
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I have never had any luck at all with the style of tank you show mounted and think that may very well be the problem.
Pete might be on to something. Back in the old days when these tanks were made by Veco, they had a baffle to keep the fuel from sloshing around during maneuvers. I'm not sure if the newer tanks are baffled and I have not had any luck with these "profile" tanks, either. I use the regular style Uniflow tank and kick the aft end out.
BTW - It may also take a new (or different) glow plug to solve your problem. When my engine burped after the second loop of a clover, I switched to an O.S. #8 plug. This is the plug I run in my RC helis and it helped to cure the problem. Changing the plug is cheaper than building a new plane.
Another .02 - again earned through time and experience. :##
Ron
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The problem with a clunk is that they require a lot of extra space at the front of the tank for all that plumbing (Hayes brand clunk tanks take less space) and you don't have much room to work with on this plane.
That S bend can't be good for steady fuel delivery. If you flip the needle assembly over, you will have much more direct feed. You can adjust the needle valve with a glove and pliers to keep your flesh out of the exhaust blast.
A chicken hopper might work well, as Pete suggests. The main tank is shaped much like the tank you're using now. I have used them with great success. Brodak carries several sizes, so check their paper or online catalog. Hoppers are a bit pricey because of all that extra metalwork, so that's a factor if your wife has you on a budget. mw~ For everyone's educational benefit, Z@@ZZZ the tank gets its name from feeders used on chicken farms, in which a large bin above the feeding trough is filled with chicken feed. As the chickens dine, the level in the trough goes down, and the bin dispenses just enough additional feed to raise the level back to normal. I believe there are cat feeding systems, for when the owner goes on vacation (or is just incredibly lazy) that work the same. However, "cat hopper tank", like "cat house" or "cat fight" might have a slightly different meaning. :## Wasn't that interesting?
Kim
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Ditto the problems with the Veco "Profile tank". When it went into production, the baffle system was changed. It is MEANT to work like a chicken hopper, but it never really did. Maybe if you were just sport flying and running the engine wide open they *Might* have worked. But for stunt use................. :(
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I have been reading this thread, and it doesn't look like anybody has determined if the engine is quitting lean or quitting rich. Sometimes, it's not easy to tell. If it's quitting lean, then there's probably something wrong with the tank. If it's quitting rich, then it might just need height adjustments. Beyond that, I think the tank needs to be replaced, if not recycled, which would be my choice. Smash it flat, too. y1 Steve
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I THINK it's going rich, but that tank is already history. I'm experimenting with other styles and shapes. Hope to have something positive to post soon.
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If it's loading up and quitting rich, then it's possible that a hotter glowplug would fix it. H^^ Steve
Edit: Well, it wouldn't FIX it. I was thinking that it might at least get through an outside without quitting, allowing tank tuning to be fussed with before the airplane is destroyed. How's the new tanks working?