600/OS55 Cutting Inverted

[waveydavey]

My clunk isn't too long guys, it may be a bit short actually allowing it to double over in the tank. The 600 tank with the sloped back makes for the clunk being a bit short and it's easy to get ti to suck to the back corner if your not careful. It's definitely a fuel delivery/pressure issue.

[coolice]

Hey.

Surely if the problem was pressure related it would still be present upright as much as inverted? Reason being the tank is no less pressured right way up or otherwise, also if a header is used if there is still fuel within it then fuel flow from main to header tank is still free flowing.

From memory I'm pretty sure your running a header tank Dave and while it is in the same position as your previous engine, which was a TT53 from memory again, this OS55 might be less tolerant to it's location.
It might pay to change it's height in relation to the carb fuel nipple, ideally try to get it in the same line as said nipple so that either way up fuel does not have to travel up or down hill any different.

To be safe you could also change all piping, it's not uncommon to have even new pipe with a pin hole in it.

The more I think about it the more I think it's linked to either tank location in relation to the carb rather than an air leak, as any air leaks would still be present right side up. Or the clunk is touching the rear/side of the tank while inverted and under high revs with fuel demand high it's being restricted somehow. The latter I'm more inclined to go with due to the circumstances which give problems.

Are you using Hayes fuel line for your clunk Dave? This is a right pain to get just right as for the first few tanks it does swell in the fuel and get longer.

Another stab in the dark, it's not too short is it in that it's leaving the fuel at certain angles? But then a header will fix this.

If you are running a header did it stay full?

I must admit I didn't know you were getting problems at the weekend or I'd have poked my head in for a closer look.
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[Mslater]

Hey.

Surely if the problem was pressure related it would still be present upright as much as inverted? Reason being the tank is no less pressured right way up or otherwise, also if a header is used if there is still fuel within it then fuel flow from main to header tank is still free flowing.

If the exhaust return becomes blocked then the tank becomes a vacuum and will not provide fuel to the Header, thus starve the engine.

[coolice]

If the exhaust return becomes blocked then the tank becomes a vacuum and will not provide fuel to the Header, thus starve the engine.

Hey.

Oh yes exactly, but my line of thought is that this would still occur with the model flying along upright to, unless your tank is full of sludge which covers the tank vent when inverted ;-)

Another thing to try is the pipe, Daves fitted a brand new pipe and if a baffle is loose inside or there is muck in there blocking the vent when inverted this would have the same result as what he's seeing. Try a different pipe is a quick check for this.
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[waveydavey]

But it's only as I get towards the bottom of the tank, I thought I'd ran out again. The header was full and there was about 5mm or so in the main tank. You've seen how much time I spend inverted Ian so I don't think it's there all the time. I've just had a good shake of the main tank and I managed to get the clunk stuck on the front wall. Is it possible that the pressure is too much in the tank when down low and the fuel tube is collapsing, it's very thin wall (Hayes). Although the 53 didn't cut it would sometimes miss a beat if I changed direction quickly.

[Eckchaz]

my line of thought is that this would still occur with the model flying along upright to, unless your tank is full of sludge which covers the tank vent when inverted.

I thought that too and posted it about the clunk being too short but I got ingnored and shot down with the other.. but its got me thinking again.. if it is down to the line kinking.. then it should only ever happen when the heli rolls left from upright.. as thats the only oppertunity to allow the clunk line to have more of an angle on it, compared to all the other orientations.

[Mslater]

But it's only as I get towards the bottom of the tank,

Dave, I had something like this but it was present in normal flight as well. Uneven Revs etc. but I wasn't running a govenor so if you are it may be hiding the same problem.

I would have mentioned this before but didn't realise it only happened at the bottom of the tank.

The problem was a bad O ring on the align fuel filter. Caused a venturi effect and sucked in air on the last 1/3 tank.

[waveydavey]

Well it went in again, a bit of damage this time so a bit ****ed off to say the least. I've renewed everything, tank, clunk etc. Could this just be down to tuning, Andy K our engine doctor has suggested that the mid is a too lean at about 1.5 turns out. It always seems to happen after a prolonged period of little pitch and throttle. This time I was coming out of a stall turn and as I started to pull out it quit, into the wind positive pitch, blades stall drops into the quarry we have at the edge of our field. Half full tank, header full.

Anyone else had this happen with this engine or similar, my clunk, pressure line etc have all been replaced

[Geek]

I have.
Check the exhaust nipple.
put a small drill in it to check the hole is open.

I too thick it could be going lean.

good luck

[coolice]

Well it went in again, a bit of damage this time so a bit ****ed off to say the least. I've renewed everything, tank, clunk etc. Could this just be down to tuning, Andy K our engine doctor has suggested that the mid is a too lean at about 1.5 turns out. It always seems to happen after a prolonged period of little pitch and throttle. This time I was coming out of a stall turn and as I started to pull out it quit, into the wind positive pitch, blades stall drops into the quarry we have at the edge of our field. Half full tank, header full.

Anyone else had this happen with this engine or similar, my clunk, pressure line etc have all been replaced

Hey.

The 50 Hypers exhibited a lean mid range when tuned on the top and bottom needles to give power and idle, the trick with them is to run the idle needle richer. IanH's model I've setup this way and its smooth in flight, you do get a little spluttery with a prolonged idle sometimes but it adds the necessary extra fuel at the mid point to smooth the engine at a critical point.

The high end needle doesn't have as much bearing on the mid range as the idle setting screw does and so run richer on the bottom to fix the middle.
.

[coolice]

Hey Dave.

Another quick idea, your running a TT RedLine HiFlow pipe on this model from memory yes? You dont have another pipe you could try out?

It might be a stab in the dark but the OS55 is a much more powerful unit than the old Hyper/TT53 and hence will produce more gas flow as a result and also the tuned rpm range of the pipe might not suit the 55.
It could explain why you're getting a problem while unloading the engine, the return pulse within the exhaust is causing problems and/or the pipe tuning is allowing the engine to drop off the power band.

Definetly worth looking at, switch off the govenor and setup the engine on curves before reapplying the govenor.
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[WOODSTER]

To rich it will cut out inverted and to lean it will cut out ,i was messing with my os55 for a good few hours at the field to stop it cutting out inverted.

[squeaky pete]

it more than likely tuning now if u checked the rest, coz im running the exact same combo in my ely q and last weekend it was one fire my heli isnt here, but i will check all my needle setting and PM them to u when i go get it later

[3D FLIP]

Hi Dave,

Is your fail-safe set to engine idle or cut there is a possibility that you have some radio problems and not fuel pick up.

[waveydavey]

Hi Dave,

Is your fail-safe set to engine idle or cut there is a possibility that you have some radio problems and not fuel pick up.

I'll check, someone suggested it yesterday and I must admit I ignored it, but worth having a look.

Ian I have got another pipe but it's just the standard align 50 one, Pete runs the same combo, the reason I went for it really. I do think it sounds like tuning now just wish I done it before writing it off yesterday.

Thing is I've lost so much confidence in it how do I test it, lots of height and hope for the chance to get it down in one piece I suppose