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Header Tank?? - 4/2/2005 12:14 AM

jpalmer

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I am just finishing my Raptor .50 V2, first heli. Do I need the header tank to just learn to hover around?? Seems it would be less complicated to just run off the main tank for now. Thanks, Joe...

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RE: Header Tank?? - 4/2/2005 12:24 AM

ptarp

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You don't NEED it, but it really isn't complicated at all to setup. Do you have some questions? I could snap some pics of my setup if you need it.

The header tank is a simple/effective way to ensure your engine gets a consistent fuel flow.

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RE: Header Tank?? - 4/2/2005 12:58 AM

WhtBronco

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As said it will run without it, but it's super easy to hook up and is a good idea to have. Just connect the pick up line from the main tank to the pressure side of the header, or what would be the pressure side on a single tank setup, and then connect the pickup line from the header tank to the carb. As usual the pressure line from the exhaust goes to the pressure fitting on the main tank. That's it.

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RE: Header Tank?? - 4/2/2005 4:33 PM

IslandSavage

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can i install a header tank laying flat on it side? will it have issues?

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RE: Header Tank?? - 4/2/2005 5:59 PM

BarracudaHockey

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You can install it however you want but you want the middle of the header tank on level with the carb.

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RE: Header Tank?? - 4/2/2005 6:40 PM

rusirius

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quote:

ORIGINAL: barracudahockey
You can install it however you want but you want the middle of the header tank on level with the carb.

No, that's incorrect... See my post here.. http://www.rcuniverse.com/forum/Can_I%25%25%25%25%25%25%25%25%25%3F/m_2834021/tm.htm

To install it on it's side would completely negate the whole reason for having a header tank... I think a lot of people think the header tank is used to "smooth" the flow of fuel to the carb... Hence needing to be in line with the carb... (something kind of borrowed from the fellow plank flyers...) It's very true that wherever your MAIN tank is is going to effect how well fuel flows... It is best to be positioned somewhere close to center of the carb... However, as for a header tank, it has nothing to do with the fuel flow.. just air...

Think of it like this... You have a 5 gallon bucket filled with water sitting on the ground... You run a tube up out of the bucket all the way up a 15ft ladder... If you try to use the tube as a straw to suck water out of the bucket it's going to be VERY difficult to draw... By putting a header tank in the straw... Lets say a 1 gallon sealed can sitting in front of you... It won't suddenly get easy to draw fuel... because to draw fuel from one tank you still have to REPLACE it with fuel from the main 5 gallon tank... the 5 gallon tank is the ONLY tank that's open to the atomsphere... If the 1 gallon one (header tank) was open to the atmosphere, then it WOULD be much easier to draw fuel.. But then it would also empty and never replenish it's supply from the 5 gallon tank... In other words, the placement of the header tank in no way effects how the fuel flows to the carb... It's the main tank... the one that's open to the atmosphere that effects that... What it WILL do however, is if the tube comes out of the 5 gallon bucket for a second, the air resulting in the line will get sucked into the 1 gallon can, and stay there, rather than being transfered into the line your sucking on....

< Message edited by rusirius -- 4/2/2005 7:05 PM >

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RE: Header Tank?? - 4/2/2005 8:09 PM

ptarp

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The position of the header tank relative to the carb will have an effect on fuel flow from the header to the carb. The position of the main tank relative to the carb won't (directly) because its not supplying the carb, its supplying the header tank. So...

Its my opinion that barracudahockey is correct, and the header does need to be in line with the carb. And in turn, the main tank needs to be in line with the header tank. Each supplier needs to be inline with whatever it is supplying for the most consistent flow.

< Message edited by ptarp -- 4/2/2005 8:10 PM >

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RE: Header Tank?? - 4/2/2005 11:26 PM

rusirius

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quote:

ORIGINAL: ptarp
The position of the header tank relative to the carb will have an effect on fuel flow from the header to the carb. The position of the main tank relative to the carb won't (directly) because its not supplying the carb, its supplying the header tank. So...

Sorry, that's just not correct... Okay, let's think about fluid dynamics here... First off, think of a manometer..

Take a piece of tubing, say 3/4 flexable plastic clear tubing... Fill it with some colored water (food coloring will work well).... Now, hold both ends up in the air (so it forms a U) now, raise one side and lower the other... Notice how the water ALWAYS stays at the exact same level? That's because each side has the SAME atmospheric pressure equalizing it... If 3/4 of length of the tubing, you were to insert a glass bulb, which can be any size you'd like, the water will STILL equalize to the exact same level on both sides... It doesn't suddenly get lower on one side because more of the fluid is in the bulb... Now if you take your "U" tubing again... This time instead of just moving one side up and down, PLUG one end of it instead... What happens now? This time the water will raise and lower on the unplugged side... It's happening this way now because the pressure cannot equalize between the two points...

Okay, one last demo... Think about it this way... You state "The position of the main tank relative to the carb won't directly [sic] 'effect the flow' because it's not supplying the carb, it's supplying the header tank..." First and foremost, you can NOT break these two things into seperate sections... As far as the fluid dynamics go, it is ONE system, not two seperate systems... You don't have a main tank supplying a header tank with ONE unique set of properties, and one header tank supplying a carb with ANOTHER unique set of properties... You have ONE unified system with ONE set of properties...
Okay, here's another thought experiment for you... If you don't agree with this one then we'll just not be able to agree...

Here goes...

You take a 5 gallon bucket and set it on the roof of your house... You stick a hose in it and run it down to the ground.... Now if you get a little fluid in the tubing to get it flowing we all know what happens correct? It creates a syphon... You'll drain every bit of the 5 gallons up top if you let it go (open to atmosphere on both sides that is)...

Now... In your theory where the placement of the header tank CAN affect the flow, here's what would happen... If we were to take a 1 gallon can, SEALED to the atmosphere (just like our header tanks), and had the tubing coming from above feeding it, and another tube coming from the header tank out... In your theory if we then RAISED the tubing (coming from the header tank) ABOVE the level of fluid in the 1 gallon can, the flow of fluid would then STOP...

However, this obviously isn't going to happen... BECAUSE THE 1 GALLON CAN (or header tank) IS NOT! OPEN TO THE ATMOSPHERE... It cannot, and WILL NOT effect the FLOW across the system... This is the same situation with the placement of the header tank... it is SEALED to the atmosphere.. It's acting no differently in the system as any of the fuel tubing is...

IF!!! You were to punch a hole in the top of the header tank (1 gallon can), THEN!!! and only then, that it's open to the atmosphere, would you be able to raise the tube above the can to stop the flow... There would STILL be fluid flowing from the 5 gallon bucket up top... No way to stop that unless you raise the tubing above the roof... but the flow from that tank will then be exiting the hole in the top of your header tank, NOT your tubing... NOW the main tank (5 gallon) and header tank (1 gallon) are working independently as far as flow... The main tank is feeding the header tank, and the header tank is feeding the exit... ONLY because the header tank is now open to the atmosphere...

Get it?

I'm sorry if this comes off harsh in any way... It certainly is not intended to be so... I do know a bit about fluid dynamics though

, and I can definately tell you first hand that placement of the tank will have NO bearing on the FLOW of the system...

< Message edited by rusirius -- 4/2/2005 11:36 PM >

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RE: Header Tank?? - 4/3/2005 1:37 AM

ptarp

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No offense taken at all

I appreciate you taking the time to write such an exhaustive "lesson"

I was (erroneously) thinking that raising the header tank would inhibit flow from the main tank while increasing flow to the carb. This is not correct because if fuel is flowing from the header, SOMETHING has to be flowing in it to replace the vacuum. The increased pressure required to push the fuel up higher is equalized by the increased pull of gravity on the downside to the carb (because the resulting vacuum helps "pull" the fuel up from the main tank).

< Message edited by ptarp -- 4/3/2005 1:39 AM >

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RE: Header Tank?? - 4/3/2005 1:50 AM

IslandSavage

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So basically I can place my tank anway i want right? Like laying it down flat (Horizontally).

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RE: Header Tank?? - 4/3/2005 2:41 AM

rusirius

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quote:

ORIGINAL: IslandSavage
So basically I can place my tank anway i want right? Like laying it down flat (Horizontally).

No, remember, it's purpose is to elimnate air from getting in your tank... The "air" in the header will always go to an edge... The edge opposite gravity... Since your heli will spend the majority of it's time upright or inverted, not laying on it's side, you want the header tank installed vertically... Since it's much less likely to suck air into the clunk that way...

quote:

ORIGINAL: ptarp
if fuel is flowing from the header, SOMETHING has to be flowing in it to replace the vacuum. The increased pressure required to push the fuel up higher is equalized by the increased pull of gravity on the downside to the carb (because the resulting vacuum helps "pull" the fuel up from the main tank)

Jesus... Wish I could have stated it that easily without taking a 1 hour dissertation... LOL!

But yeah, your exactly right!

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RE: Header Tank?? - 4/3/2005 5:27 AM

RotorNut

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Just going to throw in my observations of header tanks. I agree with most of what rusirius says but don't agree with the part that it makes no difference where the header tank is positioned in relation to the carb. If a header tank is positioned to far below the carb It will work fine but when you fly inverted your mixture will richen a little due to fact you just made a gravity feed system of sorts. The weight of the fuel in the header tank although minimal will cause a difference in pressure in the carb supply line. The opposite will happen if your to high above your carb. Any pressure change in the supply line to the carb will effect mixture as most system are not pressure regulated. That is why an engine will lean out when it has less fuel in the tank. rusirius explanation a fluid dynamics is correct but is not taking into consideration of system pressure. Fuel flow is directly proportional to fuel pressure and the resistance to the flow.

< Message edited by RotorNut -- 4/3/2005 5:53 AM >

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RE: Header Tank?? - 4/3/2005 5:39 AM

ptarp

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quote:

If a header tank is positioned to far below the carb It will work fine but when you fly inverted your mixture will richen a little due to fact you just made a gravity feed system of sorts.

The amount that gravity might "feed" the system is cancelled out by the extra force required to counter the same gravitational force when pulling fuel UP from the main tank into the header.

Now, if the main tank were above the carb, then your mixture would change a bit when upright vs inverted. But, as Dr. rusirius said, header tank position doesn't contribute

< Message edited by ptarp -- 4/3/2005 5:46 AM >

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RE: Header Tank?? - 4/3/2005 5:59 AM

RotorNut

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There is less weight of fuel in the fuel line going to the header tank so the pressure created by gravity is not as much as the 1oz of fuel in the header tank so there will still be a pressure difference.

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RE: Header Tank?? - 4/3/2005 9:56 PM

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quote:

ORIGINAL: RotorNut
There is less weight of fuel in the fuel line going to the header tank so the pressure created by gravity is not as much as the 1oz of fuel in the header tank so there will still be a pressure difference.

But remember... You aren't just pulling against the weight of fuel in the line... Your pulling against the weight of ALL the remaining fuel in the main tank... You are correct though, theoretically the position of the header tank WILL affect the flow SLIGHTLY... but not enough to even be considered in our application... At least not until the amount of fuel in the header tank becomes close to or more than the amount of fuel in the main tank... For general purpose though, it just won't make any noticable difference...

(Ohh, and it's Dr. Sirius to you!

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RE: Header Tank?? - 4/3/2005 11:37 PM

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Thats a lot of schooling on fluid flow and such, but to keep things simple the best position is just below the center of the carbuerator. This way, no matter what attitude the heli is in it will get the most consistent fuel flow. I agree with RotorNut that if you place the tank in some other position the consistency of flow will not be close to equal when the attitude of the heli is changed.

I mean think about it guys... where is your header tank??? Does anyone fly with the header tank anywhere else besides on center with the carb, I request that someone move their header tank to a noticable extreme away from the standard placing and see if there is a difference when flying, I am not just talking about hovering either, inverted and such...

Obviously its there for a reason, otherwise I am sure these innovative heli companys would find other places for them. I dont honestly believe that all the helis just HAPPEN to have the same mounting place for a header tank by conincidence.

Just my 02 cents...

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RE: Header Tank?? - 4/4/2005 12:02 AM

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rander1 I have flown with a header tank not in the correct location I'm not speculating here. Just so you know I'm not attacking anyone just a friendly discussion, rusirius the fuel in the main tank doesn't make a difference because on most all heli's the main tank outlet is inline with the carb so flipping inverted doesn't change the pressure in the main tank supply line because essentially the fuel hasn't moved in relation to the carb. But when your header tank is to far above or below the carb the position above or below changes proportionately from right side up to inverted hence the pressure difference. Here is a picture that shows what I'm talking about. The fuel in the main tank is still creating the same amount of pressure because its elevation relative to the carb hasn't changed. The fuel in the header tank however has. The change does make a noticeable difference on a non pumped system I've seen it personally. It is very noticeable on smaller engines that are picky about needle settings.

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RE: Header Tank?? - 4/4/2005 12:58 AM

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Indeed! Just a friendly debate... It's good to exercise the mind every now and again.. Blow the cobwebs out...

I'm actually enjoying this conversation more than any I've had for a long time! Anywho... As for why everyone keeps it level with the carb, let's face it, generally it IS the easiest and most conveinent place to mount it... Why wouldn't you put it there?

Rotornut, think about this for a second... I added some notations to your drawing...

In the "right side up" section... Let's FORGET about the fact that the entire system is pressurized... Let's just assume an open vent, atmospheric pressure... In this drawing, if you were to unplug the carb, what would happen? The fuel will flow OUT of the tubing if you keep it at the same height (level of equalization)... This is because in the overall SYSTEM you have more fuel ABOVE that point... Science therefore dictates that the fuel will flow since ALL things in a system will ALWAYS work towards becoming equal... Now think of it in this regard... Does it matter that you have 2oz of fuel BELOW the carb? The 2oz of fuel in the header tank is CERTAINLY more heavy, weight wise, than the fuel in the line between the header tank and the carb... Or, even heavier than the weight of the fuel in the line between the main tank and the header... Yet it will still flow.... It will flow and keep on flowing until the fuel in the overall system reaches equilibrium... Or, all levels are at the level of equalization... Get it? It doesn't matter how much fuel is under in the header tank, or what it's weight is compared to the fuel in the lines.. It all works together as one entire system...
One more thing to think about on the same point... Let's say there is only 1oz of fuel left ABOVE the level of equalization... Does that mean that it's weight cannot push against the 2oz of fuel in the header to keep a flow going? Nope... It will STILL flow until the level of fuel is exactly at the level of the output (in this case the carb)... It doesn't matter if the header tank is an inch below the carb, or a foot below the carb... The fluid will STILL flow until it levels out both sides at the level of equlization... This is the whole principle behind a syphon... It doesn't matter that the fluid has to flow UPHILL to get where it's going... It still wants to equalize out...

Now in looking at the bottom pic "upside down"... We have to change things around just a bit... See... IF this were still nothing more than an "atmospheric" system, then every bit of the fuel in the system would run right out the vent and be gone.... To make this picture WORK, and to keep the level of equalization where I drew it, we'd actually have to move the vent to the opposite side of the main tank... If we were to do that, the fuel would actually flow BACKWARS into the main tank... Filling it till it reached the vent, and the overflowed until the level of fluid was exactly at the vent level or "level of equalization"... The WEIGHT of the fluid in the header tank does not matter, nor does the WEIGHT of the fluid in the main tank that it's pushing against... The fluid in the main tank weighs MUCH more than the 2oz in the header... Yet it doesn't prevent it from pushing it down... The WEIGHT of fluid in the header tank doesn't PUSH itself down and out the carb even though the WEIGHT of the fuel in the other line isn't very much... Again, the entire thing functions as a SYSTEM... And at the end of the day, no matter how you slice it, a SYSTEM will always fight for one thing... EQUALIBRIUM!

BTW... These last two expierments are very easy to do yourself if you don't believe the results... Just grab a main tank and a header tank and give them a try!

I'll tell you this though.. LOL... JUST to make sure I was thinking straight, and wasn't going to make a fool of my self, I DID try both of them myself just to verify the results... and indeed it is just as mother nature dictates it should be...

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RE: Header Tank?? - 4/4/2005 1:00 AM

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BTW ptarp... Feel free to jump in here and sum up my last three or four posts in 7 words or less... LOL!!!

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RE: Header Tank?? - 4/4/2005 1:45 AM

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I dunno know about the the fuel flowing, did you take into consideration that the exit hole of both tanks have a clunk line? I know that simple physics works for a hole in the side of a container, but when I disconnect the fuel line from the carb the fuels drips out, doesnt flow, and that is only when I hold the fuel line below the outlet, when it is held level, no matter what the level of the tank, the fuel does not come out.

The clunk line changes everything because the atmosphere conditions are different, as fuel has to be pushed up and out of the tank, due to the icline from the clunk head to the outlet of tank as oppossed to the hole in the side where the fuel would leak out, there is simply not enough weight of fuel in the header tank to push the fuel up and out of the header tank. The main tank is different because the outlet for the clunk line is on top of the tank.

And even though your syphon there is valid, in order for the syphon to work you need to have the line on such an incline to get the fuel to come up and out of the tank. So if you put the header tank below the carb the engine would lean due to not being able to suck the correct amount of fuel, sure you could correct this with the needle setting, but what about when you flip it upside down, bam rich and flooding.

I also dont think you can disregard the fact the system is pressurized, thats like saying lets pretend that the gas is actually a vapor and not liquid.
Pressure has everything to do with the system. In fact the system doesnt work without pressure, upright or inverted. The engine vaccum is not strong enough by itself to pull the fuel it needs to run consistent at all. This is where the pressurizing comes in, but even still with the pressure, if the header tank is placed below or above the carb, of course it will work, but it wont be consistent, I think that the discussion is about consistency, not feasibility. Straight up, header tank will work in any position, but not well.

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RE: Header Tank?? - 4/4/2005 2:38 AM

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Absolutely rander1 consistency is my point exactly. I myself like to have as much consistency in performance as I can get. Just for the hell of it here is the formula for figuring out flow, pressure and resistance. E=IxR. E = force or pressure, I = intensity or flow, R = resistance to flow.

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RE: Header Tank?? - 4/4/2005 4:44 AM

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quote:

ORIGINAL: rander1
I dunno know about the the fuel flowing, did you take into consideration that the exit hole of both tanks have a clunk line?

Yes, in the closed system it doesn't play any part... remember, CLOSED system... That's assuming no variables are thrown in like bubbles of air in the fuel line, etc...

quote:

I know that simple physics works for a hole in the side of a container, but when I disconnect the fuel line from the carb the fuels drips out, doesnt flow, and that is only when I hold the fuel line below the outlet, when it is held level, no matter what the level of the tank, the fuel does not come out.

If the line is full of fuel (no air) and you disconnect it, the fuel WILL flow at the rate gravity, atmospheric pressure, and tubing diameter allow... If you hold it level with the carb, but BELOW the level of equalibrium, it WILL flow no matter what... Do the experiment above, you'll see...

quote:

The clunk line changes everything because the atmosphere conditions are different

The clunk in no way relates to the atmosphere

quote:

, as fuel has to be pushed up and out of the tank, due to the icline from the clunk head to the outlet of tank as oppossed to the hole in the side where the fuel would leak out, there is simply not enough weight of fuel in the header tank to push the fuel up and out of the header tank.

Wait... You just made my point for me... Of course the weight of the fuel in the header tank cannot push the fuel up and out of the header tank... UNLESS OF COURSE it was open to the atmosphere... Here's another example... Take your header tank and FILL it with fuel... Now seal off the fill line (not the carb line)... Pinch the tubing, cap it off, whatever... SEAL it from atmosphere.... Now if you place the carb line anywhere, what happens? Nothing... The fuel won't flow... But as soon as you OPEN it to the atmosphere what happens? If you keep the carb line below the tank, it will empty... if you place it anywhere above the bottom of the tank, the fuel will drain to just that point, put it above, and it stops... EVEN with the incline, if you hold that carb line below the tank, it will drain every last bit of fuel out of that header tank... That's the syphon effect... The system is trying to reach equalibrium... Unfortunately in this case, since the carb line is way below the tank, it can't.... so it just empties itself...

quote:

The main tank is different because the outlet for the clunk line is on top of the tank.

where the outlet is has no bearing on the system.

quote:

And even though your syphon there is valid, in order for the syphon to work you need to have the line on such an incline to get the fuel to come up and out of the tank.

Not at all... See above... even though the line NEVER goes above the level of fuel in the header tank it STILL functions as a syphon and will drain every last drop of fuel out...

quote:

I also dont think you can disregard the fact the system is pressurized, thats like saying lets pretend that the gas is actually a vapor and not liquid.

Not at all, quite different indeed... By pressurizing the system, all we have done is INCREASE the amount of flow over the ENTIRE system... We have not in any way changed the WAY the system functions, or varied pressure unequaly across seperate parts of the system. The system still functions exactly as it would without pressure, just with increased flow because of the pressure differential between the pressurized side and atmosphere side...

quote:

Pressure has everything to do with the system. In fact the system doesnt work without pressure, upright or inverted.

Yes, it makes the ENGINE work... It makes the carb, which really has little to no drawl or pumping action (it can't establish it's OWN differential in pressure, well actually it can, but very little)... But I think you misunderstand when I say "SYSTEM"... I don't mean system in the since of your fuel system, or power system for the heli... I mean system in the physics definition... Basically the "system" we're refering to here is from the VENT line of the main tank, to the Carb line of the header tank... Everything else is null and void... nothing else will effect the WAY the system operates...

quote:

I think that the discussion is about consistency, not feasibility. Straight up, header tank will work in any position, but not well.

Let's just put it this way...

The placement of the header tank WILL effect the system as a WHOLE (though not for the reasons stated above), but... and here's the big one... It does it on SUCH a minute scale, that it would be undetectable... ESPECIALLY compared to the effect your main tank has while it's emptying out... In fact, I just remembered a site I read a while back talking about setting up a tank to elimnate the flow differential from full to empty on the main tank... Take a look, it actually covers a lot of the principles already covered in this post, and in fact, mentions specificaly about the header tank location... Note the part where is says some people think mounting the header tank ABOVE the main tank will give more pressure? (since as you stated this would give more flow because of the weight of the fuel in the header tank) It however does NOT because (and he states the same exact reason as me... It's all part of a CLOSED system... (here's the link...) http://www.fraserker.com/heli/uniflow/how_uniflow_works.htm

Anyway, if you STILL won't take my word for it... Seriously, find someone local that has a strong background in physics, fluid dynamics, etc... Show them your setup and ask them if moving the header tank higher or lower would effect the pressure (i.e. flow) at the carb...

< Message edited by rusirius -- 4/4/2005 4:45 AM >

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RE: Header Tank?? - 4/4/2005 4:56 AM

rander1

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ummm wow

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RE: Header Tank?? - 4/4/2005 9:09 AM

RotorNut

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Rusirius, one thing your completely wrong about is its not a closed system it is a BI-flow system. There is nothing in a non pressurized system that is closed off. Here is a quick experiment to prove my point. Fill you heli completely full of fuel including the lines to the muffler and carb then squeeze the header tank. What happens? Fuel goes into the muffler and into the carb right. Same thing but squeeze the main tank this time. Same thing happens. Fluid is moving in and out of the header tank. BI-flow, fluid can move in and out so its not a closed system at all. This being proved does kinda make your examples of a closed system although correct unrelated to a fuel system. If you don't think this minute amount of pressure difference will effect your mixture try this, fill your tank half full of fuel with your header tank full of fuel and strapped to your skids tune your engine. Then go hover and have someone tach your blades. Then flip inverted and hover and tach the blades. When inverted your blade speed will change. After that put the outlet of the header tank inline with the carb and do it again. Btw make sure you have your throttle is at the same setting with the negative pitch angle as with your positive pitch. just an example 6 deg pitch at 50% throttle and -6 deg pitch at 50% throttle. I have done it and have seen the results. As you say " You have ONE unified system with ONE set of properties." This statement being true would also mean that according to your own statement moving the main tank would have no effect either as it would have the same properties as the header tank. And you and I both know that's not true. The statement is true but your conclusion is wrong. Being one unified system moving either tank will create a difference. Not the exact same differences as the size of the tanks are different. Again this is by no means an attack on you.

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RE: Header Tank?? - 4/4/2005 4:44 PM

rusirius

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quote:

ORIGINAL: RotorNut
Rusirius, one thing your completely wrong about is its not a closed system it is a BI-flow system.

Ahh, sorry about that, you misunderstood when I said closed system... I don't mean the entire system is closed... There are two points open to atmospheric pressure (or one to exhaust pressure and one to intake pressure to be more exact). When I say a "closed system" what I am refering to is that the header tank itself is PART of a system... The header tank is not in any way open to the atmosphere... It's intake is connected to the main tank and output to the carb.. I guess what I was trying to get across is that the main tank and header tank function as a whole, not as two completely seperate systems with seperate properties... LOL, we could however venture into chaos theory and debate that the entire UNIVERSE is a closed system, therefore so would the main and header tank system as well... We'll leave that one for another thread though..

Actually, it's not a bi-flow system either... Bi-Flow assumes two outputs.... TRUE if you squeeze one of the tanks with neither end connected you will have "two outputs", but really it is just equalizing the system because of the excess pressure you have placed on the system. In it's normal function it has one input and one output...

quote:

This being proved does kinda make your examples of a closed system although correct unrelated to a fuel system.

Not at all, if I were basing my points above on a true "closed system", in each case, the vent of the main tank would be connected BACK to the output carb line... All of the examples above do assume two points open to atmospheric pressure (regardless of rather those pressures are higher or lower than the current barometric pressure.

quote:

If you don't think this minute amount of pressure difference will effect your mixture try this, fill your tank half full of fuel with your header tank full of fuel and strapped to your skids tune your engine. Then go hover and have someone tach your blades. Then flip inverted and hover and tach the blades. When inverted your blade speed will change.

Do this experiment yourself, with the header tank in the SAME position (in line with the carb)... Your blade speed will change as well... Not because of any differences introduced by the header tank position, but because the heli itself becomes much less efficient when it's upside down... (Yes, even with fully semmetrical blades)... This is because the weight distribution has changed... You now have weight on top of the rotor, not hanging under it... Gravity also slightly affects the flapping of the blades, etc... Kinda a sad example, but I can't think of a better one... Imagine yourself hanging from a monkey bar... Not too difficult to stay that way a while right? Now try the same thing but standing on your head... Even if you have great balance and can pull it off, it requires much more effort to accomplish the same basic feat...

quote:

As you say " You have ONE unified system with ONE set of properties." This statement being true would also mean that according to your own statement moving the main tank would have no effect either as it would have the same properties as the header tank.

Not true... The main tank and header tank BOTH work together... Unified... Again, as stated in my previous post, moving the header thank WILL effect the flow SLIGHTLY... Just not enough to even be detected in our application... The main tank will affect the flow on a MUCH! larger scale... Because IT contains the bulk of the fuel... IF you wanted the absolute IDEAL location for BOTH tanks, you would have to average the two out... Given the ratio of fuel (2oz to the size of your main tank), and then based on this ratio calculate the exact heights for each tank to place the "level of equalization" (see previous post) EXACTLY at the carb.... The problem is... Remove even 1/2 oz of fuel, and you've moved that line... So does moving the header tank alone, just not enough to worry about... Again, losing 1oz of fuel in the main tank will effect mixture far more than moving your 2oz header tank say 4 inches up or down...

quote:

The statement is true but your conclusion is wrong. Being one unified system moving either tank will create a difference.

Exactly! your absolutely correct, but again, just not to any amount that is noticible... And in fact, in some cases it even affects in in the exact opposite way you would think (go back and look at the web page linked above... Moving the header tank ABOVE the carb, instead of INCREASING pressure on the carb line, actually REDUCES it because of the syphon effect of the system.)

quote:

Not the exact same differences as the size of the tanks are different.

Absolutely correct... and as stated above, the header tank plays such a SMALL role in the overall flow of the system, it just isn't worth worrying about... Technically, we're BOTH right... You in that the placement of the header tank DOES affect the flow of the overall system, but I in that the effect on the flow is such a small amount, that it's irrelevant to the operation of the overall system, ESPECIALLY when you have OTHER variables that are affecting it to MUCH larger extremes (like the main tank emptying out of the course of the flight)...
Actually, if one HAD set up the uniflow system, while there would be other variables that would effect flow as well, THEN the header tank would play a much larger role in the flow of the system... THOUGH, and don't quote me on this, because I would have to do the calculations on it, if the header tank was set up as a "uniflow" as well, then it's placement again should have negligable effects on the system as a whole...

quote:

Again this is by no means an attack on you.

Not at all!!!

I personally think this has been a terrific discussion... Like I said, it's good to blow the cobwebs off the mind once in a while!!

Usually it's hard for me to have conversations like this because once people find out I'm only 11 they don't take me seriously...

Okay, sorry, that was a joke, but you have to admit the look on your face had to be priceless for a moment...

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