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HelicopterThunder TigerOther › TT50 idle needle mod - results
09-04-2003 01:14 AM  14 years agoPost 1
rcrebel

rrApprentice

Michigan

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Well, I did the needle mod the other night to the heli, and was able to test fly today. Here are my results:

I have to set the idle extremely rich (3 turns) and the high needle is at 3 1/4 turns out. It runs rich at idle, lean at hover and FF flying throttle setting, and great on high end. Basically, it's lean in the mid-range. I can't remove the leaness with the high needle, and if I go any richer on the idle needle, it will barely idle.

Does this mean I need to file a little more off the idle needle between the tip (.8mm) and the area up to approx. 4 mm from tip?

I have the tip at .8 mm, and it started out at 1.10 mm.

Also, when I first got this engine (2 weeks ago), I had the low needle out 4-5 turns and the high at 4 turns. At these settings, it was getting hot and not wanting to run. Then, the high speed needle fell out in a hover so I had to order a new one. It's a little better now after the initial mod, but I think I need to remove more material.

Help, please!
Scott aka rcrebel

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09-04-2003 02:10 AM  14 years agoPost 2
spaceman spiff

rrKey Veteran

Tucson

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sounds like a little steeper angle tward the tip will do the trick. i was goofing around with needles on my 39 a while back, i started with a similar mod to what you described, it improved the stituation, so i went ahead and ground it down some more, almost to a point. worked great.

annother thing it could be is the needles often leak air past the o rings, which causes leaning problems. You can make a seal for the main neddle using a slice of large silicone tube that wedges against the end of hte needle barel and the handle of hte needle. seals it right up. not sure what to do about the idle needle, maybe find an o ring that is ever so slightly fatter than the one on there now (ace hardware has a selection of o rings that you can choose from) or maybe you can pack some plumbers silicone in the hole once you have it adjusted.

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09-04-2003 09:14 AM  14 years agoPost 3
Mr_Magoo

rrVeteran

Nevada

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It runs rich at idle, lean at hover and FF flying throttle setting, and great on high end.
That's exactly how a convex needle taper is going to run. I tried to explain the reason for using a concave taper on the LS Needle and how that would richen the midrange. I ran into some internet experts that told me I was wrong, so I mostly keep my opinions and experience to myself. But if you want to richen your mid-range, you should move away from the convex needle taper and go towards a concave taper. That way, you can have a clean idle and a richer midrange.

Magoo

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09-04-2003 07:23 PM  14 years agoPost 4
scouse

rrApprentice

UK Liverpool

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Are u sure i dont have an air leak somewhere?
The intial settings with unmodified needle seem a bit too much.
Mine with modified needle which sounds as though its the same spec as yours is 1 1/2 turns on the low and 2 turns on the high, runs great for me. Im also using 15% coolpower which made a big difference (first off i was using 5%)

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09-04-2003 07:37 PM  14 years agoPost 5
G.Man

rrProfessor

Bristol

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hehe good old Magoo, he loves to get a sly dig in where he can

Anyway, I didnt criticise his use of a concave taper at all, what I did was say that WHATEVER taper you use it only need be over the ACTIVE portion of the idle needle which is the tip to about 4-5mm in (the amount that the needle moves in and out of the jet)....

At full throttle the idle needle should be completely out of the seat allowing full mixture control to the main needle...

An alternative, as Magoo has found sucessful is to modify the idle needle COMPLETELY so that it controls the mixture accross the entire throttle movement and all you use the main needle for is to modify the fuel pressure to that needle...

Both of these methods work, but IMHO I prefer to use the high needle solely for full throttle mixture and the modified idle needle to control the mix upto this point...

Both are accepable methods but from what I am reading about your needle it does need more of a concave taper where the needle is at hover throttle

Don't Email me as I wont reply - PM Only (spam countermeasures)

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09-04-2003 08:41 PM  14 years agoPost 6
Mr_Magoo

rrVeteran

Nevada

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Galifrey:

It seems we have a truce. But, I don't understand why you are defining the active area of the LS needle from the LS needle tip. The idle side of the active area starts about 0.75mm over from the mark left on the LS Needle when it bottoms when the carb is fully closed. The 0.75mm is the sum of the idle mixture turns (approx 2) and the amount the carb barrel moves to obtain an idle. The HS end of the active range is defined by the barrel helix groove.

Also, my concave taper is steep enough that the idle needle gives up control and the HS needle takes over during approx. 1/2 throttle plus operating conditions.

In real life, I'm all about the fun of this hobby. I spend countless hours helping people when asked. If someone doesn't want help, I keep my mouth shut other then to compliment their flying progress.

Magoo

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09-04-2003 09:54 PM  14 years agoPost 7
G.Man

rrProfessor

Bristol

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hey dude, just relax

the active area depends on how you run your needle...

you run yours different to mine, I am man enuff to admit there is more than one solution...

Mine works well, and I believe yours does as well...

lets just keep helping people and let them decide which works best for them

keep smiling

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09-05-2003 02:33 AM  14 years agoPost 8
rcrebel

rrApprentice

Michigan

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Great info guys. Thanks for all the feedback.

I'll shave a bit more off the needle and give it a test flight.

rcrebel

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12-29-2003 02:02 AM  13 years agoPost 9
ghost

rrNovice

virginia

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TT50 needle mod

Does anyone sell the modified needle?. Thanks

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HelicopterThunder TigerOther › TT50 idle needle mod - results
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