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Thread: Fuel Tank Baffle

  1. #1

    Fuel Tank Baffle

    Has anyone ever done a fuel tank baffle to prevent weight transfer in cornering? With a 4 gallon fuel tank that's
    about 30lbs sliding around and that would have some effect in the balance of the car. Any ideas?

  2. #2
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    Why would you want 4 gallons of fuel in an FSAE car?

  3. #3
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    Typically baffles are installed out of necessitity as the first order consequence of not having baffles is fuel starvation. In my opnion, weight transfer is at best a second order effect (ie: less important) than fuel starvation since any VD effects of fuel movement do not matter if you lose engine power while under accelleration (lateral or longitudinal).

    Take a look at the fuel economy scores for the last competitions to benchmark fuel tank sizes; we did this on our first car, put some conservatism into the estimate (maybe 15%), and built a tank to great success. As Kevin pointed out yours is not a typical size.
    Jim
    "Old guy #1" at UCONN Racing

  4. #4
    List what your fuel tank must do, after search how it can do this and what are problems (like what longitudinal or lateral acceleration will make on the fluid), With this you can design it in order to reduce the problems that you have found.

    The main goal, NUMBER 1, is to have fuel and mainly provide fuel to the engine during all endurance event. If your design is a bit heavy but sure at 100% to work, it's can be fine for a first attempt. But it's not a reason to have 15 liters, so see how much is the mean consumption, or better, calculate it or if you have a car, do test and take a safety factor, like 20% and this would be enough...

    Define the problem, search what are the possible solutions, select best solutions and eliminate useless and design it. If you can, after, test it on the car, because the fuel tank design for FSAE is often an iterative design with experimental test to validate solution.

  5. #5
    There is also special types of foam made expressly to reduce fuel movement in racing fuel tanks.

    If you do a functional analysis like Thibault HUGUET suggested, don't forget to include everything that it should do when the car is not racing! I.e. : Can be filled AND emptied easily.

    The fuel tank may seem as an easy task, but many things can go wrong ( I have witnessed too much, my team or others ). Leaks on the weld caused by flexing on the tank (Should have been softly mounted), Inner wall coating disintegrating into fuel at comp, Engine starvation in slaloms, Bubbles in the tank (Destroyed our fuel economy, at the filling station they will move the car to make sure there is no bubble, ONLY when filling after the endurance).
    :::::::::::::::::::::::::::::::::::::::::::::::::: :::::::::::::::
    2007-2012 - Suspension, chassis, and stuff (mostly stuff)
    Université de Sherbrooke

  6. #6
    I agree with you francis !

    Design a fuel tank is easy, design a good fuel tank less.

    I think you have list the main things that must be keep in mind for design of this part. And yes, think to manufacturing too, no leakage is permit for well know safety reason, so before put fuel in, test it with another fluid like water, that you permit to weld again (No weld again if fuel is introduced in the tank, even after long time...)

  7. #7
    A go-kart tank holds 9 liters of fuel. It picks up fuel with a bobweight on the end of the fuel tube. I never had fuel starvation issues even in an ICC.

    If you must build your own tank, make it out of thin-gauge steel (0.035" or thinner), not aluminum - small vibrations will eventually crack an aluminum tank - there is no endurance limit with aluminum and thin folded'n'welded sheets of aluminum create textbook stress raisers.

    Stationary baffles work fairly well and are unlikely to break. Separate it into three sections, with the pickup in the narrow middle section, and provide small holes for fuel to drain slowly between the three sections on the straightaways to keep the level even.
    Charles Kaneb
    Magna International
    FSAE Lincoln Design Judge - Frame/Body/Link judging area. Not a professional vehicle dynamicist.

  8. #8
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    Quote Originally Posted by Charles Kaneb View Post
    If you must build your own tank, make it out of thin-gauge steel (0.035" or thinner), not aluminum - small vibrations will eventually crack an aluminum tank - there is no endurance limit with aluminum and thin folded'n'welded sheets of aluminum create textbook stress raisers.

    Stationary baffles work fairly well and are unlikely to break. Separate it into three sections, with the pickup in the narrow middle section, and provide small holes for fuel to drain slowly between the three sections on the straightaways to keep the level even.
    I agree with Charles on the latter part, but do not agree with building only from steel. Aluminum and rapid prototyped tanks both work quite well as long as you understand their limitations (mostly fatigue). You want to use a 3000 or 5000 series aluminum in annealed state. Since this is your first tank you'll want to go a little thick (about 0.060" is good). These bend quite well and also easily weld. After welding you want to leak check with water and then coat with epoxy (Caswell Platings makes good stuff) to ward off any future leaks or chemical attack by the fuel. Mounting is pretty simple, just isolate from the frame with some rubber and concerns of fatigue cracking is greatly reduced. If you pick up Carrol Smith's "Engineer to Win," it contains a good section on forming aluminum.

    In further years it's pretty simple to reduce weight by using a thinner sheet, but until you get the hang of welding and mounting you'll want to keep your tanks thick. Our latest tanks have been about 0.020" thick, but our welders are also good enough to weld cans and razor blades together.
    Jim
    "Old guy #1" at UCONN Racing

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