Fuel tanks, baffles and assymetry.

[hollus]

Scarbs just posted one of his usual gems:

http://scarbsf1.wordpress.com/2012/06/0 ... el-system/

One bit got me intrigued, from his drawing of a simplified baffle system:

The footnote reads: "Baffle system simplified: the inside of the tank is crossed with baffles with one way trap doors to direct fuel to the rear centre compartment."

My question is: why to the rear center compartment? I understand why to send the fuel down and to the rear, but why to the center? Could it be better to direct it either to the rear left or rear right, in a circuit dependent manner?

One desings an F1 car laterally symmetric within reasoneable limits, as the car has to complete a season, but in certain circuits most corners, or at least the most important corners, have a predominant direction. Montmelo is a prime example, where most critical corners are right handers, and we know that teams do not shy out of assimetry when needed, at least Mclaren doesn't.
The fuel tank is a piece that one could design specifically for each circuit, that can be changed even in between sessions, and that controls the placement of a lot of weight in the car. At the start of the race it is symmetric, but with its 160Kg (give or take) of fuel, as it empties it would be easy to place some 20Kg of extra weight either to the right or to the left of the centerline (up to 40cm). Note also that it can be done without placing the fuel any higher than if sending it to the center.
If this makes the car too unstable, one could use the trick only for the last 10-20Kg, making it a qualifying only feature. Specially in qualifying this could be useful, as tyre life doesn't come into play.

So again:
1) Why send the fuel to the center rear and not left rear or right rear?
2) Where would the shifted weight be more beneficial in critical corners: in the inside or in the outside?

[Richard]

I'm not sure why Scarbs is emphasising vertical baffles. The Sauber video explained the use of horiz baffles. viewtopic.php?f=1&t=12855

Also the ATL diagram in Scarbs' blog shows horz baffles

[flynfrog]

I would venture to say there is not much to be gained by shifting the fuel one side to another. The tank hugs pretty close to center line so shifting a few kilos a few cm is not going to have that big of an effect. Also the tanks are a royal pain to change and the teams don't want to be doing it all the time.

The reason for putting the pickup at the rear is you don't want to fuel starve under accell. The highest fuel demands are when the car is going strait. ( you don't use much throttle on the brakes or in most corners) So the rear center makes the most sense.

[hardingfv32]

Maybe to keep the CG lower of the fuel load.

Brian

[strad]

Your answer
IT IS:

drawing of a simplified baffle system

[quoteto keep the CG lower of the fuel load.

][/quote]

[Sombrero]

To me, the ultimate fuel tank is still the Piëch Druck-Kugeltank.. =D>

[MadMatt]

Out of topic Sombrero, but very interesting ! You should start a new thread about it so we can know a bit more ! It looks to be a Porsche 917 but I am not sure

EDIT : That's the 909, sorry !

[aussiegman]

IMHO and from my experience (with non-F1 cars but touring and other Formula cars) it is for the reasons previously stated as well as a few others:

1: To try and keep the fuel as close to the cars centre line as possible (optimisation of weight balance for consistency);
2: To keep the CG of the fuel load (160kgs) lower in the car (Centre of gravity and optimisation of weight balance);
3: To prevent fuel starvation under acceleration immediately after a braking event such as during acceleration on corner exit where the fuel has been forced forward and to one side (multiple pickups also help in this situation);
4: To reduce the effect of 100kg+ of fuel sloshing around mid corner, mid race after the first 60kgs has been used up (100kg's+ of fuel gets up some momentum and can unsettle the car mid corner once it hits the side the the tank and the force of the weight transfer works its way through the car);
5: To stop foaming of the fuel due to excess agitation (heats the fuel and can also result in starvation at low fuel levels);
6: Having the fuel low, centred and further back in the tank, even if only by a small amount, preserves the original weight balance and places a more even load on the rear tyres aiding to rear tyre grip.
7: Additionally, if the fuel load can move side to side, the weigh transfer unloads the inside tyre and overloads the outside tyre giving a net reduction in tyre performance and if substantial enough can result in unsettling the car enough to loose traction or spin the car

I have seen these effects in a recently completed late 1970's model touring car with a 140Lt "drop tank" that was located behind the rear axle line that had minimal/ineffectual internal baffles. It had issues with fuel loads moving around at anything under 60% capacity (84lts) unsettling the ear of the car mid corner and at lower tank levels with starvation. Tank foam, better baffles and multiple pickups fixed the problem.

Exaggerated when compared to an F1 car, but still relative when you are trying to get every last % point of performance from car and tyre while giving the most consistent car to the driver.

[aussiegman]

So again:
1) Why send the fuel to the center rear and not left rear or right rear?
2) Where would the shifted weight be more beneficial in critical corners: in the inside or in the outside?

Further to answer your questions:

1) for the reasons previously posted which is primarily to give a consistent car that does not have a large variant from moving fuel loads.

2) if you were to move the fuel (removing the mechanical components required to quickly shift fuel from side to side), the fuel would be most beneficial if you could hold it against the "inside" wall of the tank to offset the natural tendency for that side of the car to lift due to centripetal force. However the pumping requirements and short time periods in which to achieve fuel movement would be difficult as you would need to move and hold the fuel through the corner fighting against the centripetal force, move the fuel back across the tank when the car exits the corner and in the case of a chicane shift immediately across to the other side of the tank. It is easier to simply try an centre the fuel load, not introduce the complexity of a fuel transfer system and work through other ways to improve the weight balance of the car.

All that being said, Renault in 2006/07 IIRC used an approximately 9kg movable mass damper that was mounted inside the nose of the 2006 R26 car. So using a mass to effect the body attitude under acceleration or cornering is certainly effective, however it should always prescribe to the K.I.S.S system and be as simple as possible.

The simplest way of moving the fuel I could think off the top of my head would be to use an internal bladder that was mounted on a pivoting board or plate. This is in turn mounted on a weighted ball that moves across the short axis of the car from side to side. As the car enters a corner, centripetal force pushes the ball to the outside of the tank and so angles the pivoting plate to move the fuel to one side. If you could keep the weight of the ball low enough so that it does not defeat the purpose of moving the fuel it might work. There would also be packaging issues of lifting the fuel cell up in the chassis and other variables as well as you would have to deal with the force of the ball and fuel eventually settling into position which may have enough momentum to unsettle the car if the energy is released virtually instantaneously when it reaches maximum travel and stops.