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HelicopterAlignT-REX 700N › HeaderTank-standoff
06-04-2009 05:23 AM  8 years agoPost 41
littleman

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Pasadena, Ca

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I use the bottom engine mount hole, using just a screw through the bracket which is upside down my normal standards. I have a thin peice of 2 face convering the upper engine mount screw, and the header tank pushed back so its touching the main tank.
A.J.

Proud member of Teams Castle, MSH USA, Futaba, Scorpion, & Nick Maxwell Products

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06-04-2009 05:39 AM  8 years agoPost 42
rexxigpilot

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Florida

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If you look closely at his picture, the level of the line coming out of the main tank is even with the entrance of the fuel line into the nipple, the same height as the header should be, therefore, even with the main tank fuel line exit, which is even with the nipple.
not the barrel

If it was supposed to be the barrel then the main tank would be even with it too.
Simply not true. First off, we are talking about pressurized systems with almost all RC helis. The fuel system of a typical pumped heli engine operates at more than a couple of psi, as do muffler pressurized systems. The change in the fuel system pressure due to static head is typically insignificant.

The pressure added to a hydraulic system due to height above a reference point is known as static head or delta Hs. It takes 2.54 feet of head to equal 1 psi when we discuss 30% nitro fuel at approx 7.5 lbs/gallon. Using Bernoulli's principle the static head at the carburetor is the difference in height of the fuel between the inlet and outlet. The inlet is the header tank. Since the header tank is typically full, the inlet height is the tank top or bottom if flipped inverted. The outlet is the orifice that lets fuel enter atmosphere in the venturi (barrel) of the carb.

Even with a poorly selected header tank location the change in static head between upright and inverted is only maybe two inches, which is equal to 0.066 psi. In a fuel system with a total head as low as 2 psi, this works out to only a 3% change in total pressure.

Header tank location is not that critical to fuel flow in the typical RC heli. Sorry if I bored anyone. I thought it was important to get the truth out here.

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06-04-2009 07:09 AM  8 years agoPost 43
brcg123

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Wagoner OK USA

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Wow, when Im wrong Im wrong huh? Id say tie it with a shoelace to your skid tube and forget it then...








Trex700N, Trex600N, Raptor70, RaptorTitan, GMPCrickett, Visa

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06-04-2009 03:49 PM  8 years agoPost 44
dos boss

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Broken Arrow, Oklahoma - USA

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I built a new bracket for mine last night and now have both clunk nipples level. I will test it out Friday to see if I still get air bubble in header tank.

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06-04-2009 05:48 PM  8 years agoPost 45
JetFire

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The Golden STATE

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Cool 'dos' let us know. From the info gathered, I made a slight change in my standoff and swapped it for something better and shortened the feed line to the carb. As it stands, its basically the same setup I had originally with the feed line from the header... in line with the carb. I will let you guys know as well if I get any issues otherwise I'm basically done with this project.


Trex700N Pro
DX8-2.4
Spartan/BL9088

-The ONLY way you fail is when you quit.-

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06-04-2009 10:52 PM  8 years agoPost 46
dos boss

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Broken Arrow, Oklahoma - USA

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OK JetFire, Have a ball game tonight but I will test mine tomorrow and if it works good I will add photo as well.

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06-05-2009 01:11 AM  8 years agoPost 47
RC.

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Bay Area Ca.

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axial post
This is what I used on my trex 600n. I think it should be the same on the 700. Just search "axial" on tower to find more.

http://www3.towerhobbies.com/cgi-bi...p?&I=LXWDN2&P=7

RC.
MI Flyers.

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06-05-2009 02:28 AM  8 years agoPost 48
dos boss

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Broken Arrow, Oklahoma - USA

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The 40mm would work for the 700 but then you will need to extend it to get the header tank at the right level. I think it would work great though, thanks

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06-05-2009 03:53 AM  8 years agoPost 49
flustercluck

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Newnan Ga (Just S. of ATL)

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header tanks are for pussies......
+1 for whoever said that

Just fly til your out of gas & auto down... seriously.. makes it more of a challenge.

'Sides, headers on a 700 look goofy.

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06-05-2009 04:09 AM  8 years agoPost 50
dos boss

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Broken Arrow, Oklahoma - USA

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flustercluck

I guess that's OK if you have enough experience but I do have to say the times I have been forced to Auto come out better than the practice ones.
Is that what you do on purpose?

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06-06-2009 02:19 AM  8 years agoPost 51
flustercluck

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Newnan Ga (Just S. of ATL)

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Dos, I was only half-joking. The reality is, the "countdown alarm" on my DX7 is very weak (esp when flying a 90 close-in).

Thus, many has been the time when I've simply run out of gas in-flt. While it can make things exciting, it's almost never planned-for.

I do run a fuel mag, and the 700 tank is see-thru. So you'd think I could manage my fuel. But what I find on the 90ST is that fuel mileage varies greatly, depending on how much I'm on the throttle; therefore it's hard to predict when the motor will stop (the exciting part again).

Personally, there's something about a header on a 700 that doesn't look right to me, in addition to just adding dead weight. Who knows. I may still do it.

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06-06-2009 02:53 AM  8 years agoPost 52
dos boss

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Broken Arrow, Oklahoma - USA

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I agree the header tank uglies it up a bit but my magnet was causing me issues finally got that all sorted and got a good 5 or 6 flights on it today and no more air bubbles but now after all day flying it started acting up the tail started just jerking to the right about 20 degrees and just stop then a few seconds later it may or may not jerk back then the engine would just slow down to about half throttle and pick back up again. I changed out all the fuel lines, changed out the gyro checked all wiring checked glow plug. I am going to pull engine and carb tomorrow morn to see what I can find.

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06-06-2009 03:38 AM  8 years agoPost 53
flustercluck

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Newnan Ga (Just S. of ATL)

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Sounds like either a mixture issue or a non-smooth-running motor. Good luck getting it sorted.

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06-06-2009 04:10 PM  8 years agoPost 54
dos boss

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Broken Arrow, Oklahoma - USA

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Thanks,

I just took carb all apart and blew it all out so if that isn't it I am not sure where to go next. I am going to test later today

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06-07-2009 03:09 AM  8 years agoPost 55
Regie

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Manila, Philippines

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3M double adhesive tape rated at .4kg/inch.

First two weeks of my T700, I used the canopy stand offs of the Stratus. Then found this 3M tape on some hardware store. I can cary the whole heli on the header tank and muffler and the header tank is rock solid on it's position.

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06-07-2009 04:20 AM  8 years agoPost 56
Helifat

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Vista,Ca

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Had it mounted like this for a while but got rid of it after a fuel magnet was installed!

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06-07-2009 02:40 PM  8 years agoPost 57
dos boss

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Broken Arrow, Oklahoma - USA

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Problem seems to be solved at the moment
After removing carb and cleaning it though out, it solved the problem at least for the first flight. I tried the sticky tape on header tank and it lasted about 1 minute and fell off. I rigged another mount at the field but didn't get time to check it, I had to leave on family emergency. Maybe a few days before I get a chance to check it out again but I am confident that this problem is solved, what will be next.
I have worked on this 700 more than any other heli I own.

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06-08-2009 02:28 AM  8 years agoPost 58
flustercluck

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Newnan Ga (Just S. of ATL)

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Sounds like a motor and/or header retrofit issue... not a 700 issue per se

The motor part's a black art; can't really help ya there... on the header, just chuck it & get a fuel mag

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06-08-2009 02:52 AM  8 years agoPost 59
brcg123

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Wagoner OK USA

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get a fuel magnet...

here we go again...








Trex700N, Trex600N, Raptor70, RaptorTitan, GMPCrickett, Visa

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06-08-2009 02:08 PM  8 years agoPost 60
dos boss

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Broken Arrow, Oklahoma - USA

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I could be wrong but I believe that is what started all my issues in the first place. I could flush my carb out and get several flights out of it then would have heating problems so I removed it and started on the header tank adventure. I haven't had a heating issue since I removed the magnet but I have done so many other things it is hard to tell for sure. I think I will stay with the header at least for now.

Thanks,

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HelicopterAlignT-REX 700N › HeaderTank-standoff
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