is it safe enough to put in the front?
under seats, behind seat?

any help appreciated

[Edited on 11/8/04 by liam.mccaffrey]

Hell, just put it anywhere you need the weight to be where it'll fit . I'm putting mine in the front because that's where I could use the weight of 16 gallons of fuel. It seems that first reaction to putting it in front would "be too dangerous" but I say, why does putting it in the back make things any safer? When you get hit in the rear, it's usually somone elses fault, they rear ended you.....but if you get in a front end collision, more of the time it was your fault. So I say putting it in the front is safer...if you're a good attentive driver.

what about using a beer barrel i know some of the mini crowd do it, its the perfect size for my chassis plus i could do with the weight up front

there is no safe place to store 16 gallons of explosive fuel
Having it in front of you probably makes you drive more attent!

any where is better than shifter carts, in between your legs, 2 years ago I bent a steering link which jammed the brake pedal up and I hit a curb head on (while down shifting, remember I had no brakes or steering), and had fuel splash straight into my face.

I would think the best place on an MR car is the front, mainly to balance the weight out, but thinking about it the weight would decrease over time as you burn the fuel up. Probably the best place would be dead center so any weight loss wouldnt be felt on the car

I'm building a mid-engine Mini. Since the engine is behind me, the fuel-cell went in front, where the transmission would be in a "normal" front-engine, rear-drive car. The reasoning is that in an impact, the cell will be pushed to the rear, between the two occupants.

You can see it here during construction:

Liam,

I'm putting mine behind the lower seat back bulkhead. It's fairly well protected and pretty close to the (calculated) CofG position.

Dominic

i think i will put it up front any thoughts on beer barell fuel tank

Are you at all concerned about the effect that the changing weight will have on the handling of the car?

You may have grip with a full tank, but it'll degrade into understeer as the level drops.

The most sensible place would be to put it behind the seats, behind a bulkhead. That way, your weight distribution and therefore handling won't be affected as much. And it's in one of the safest places in the car.

hi, I have just been playing with my fule tank witch sits in an alloy box made by the engin bay bulkhead and the angled sheat that comes down behind thoe seats giving a weaged shape hole the tank is basicly the with of the iner cell of the car the role hope extends down to the bace of the car so the is exelent protection ps if you are making up a foam seat or the like this can go straite back on to the paneling over the tank

Blake

[Edited on 12/8/04 by ceebmoj]

yes upon consideration behind the seat would be better, i could make it wedge shape to fill the space made between the angled seat back and the vertical made by dropping a line from the top of the seat back,

is this what people mean?

i will put a beer fuel tank in somthing, one day

quote:

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Originally posted by tadltd
Are you at all concerned about the effect that the changing weight will have on the handling of the car? You may have grip with a full tank, but it'll degrade into understeer as the level drops. The most sensible place would be to put it behind the seats, behind a bulkhead. That way, your weight distribution and therefore handling won't be affected as much. And it's in one of the safest places in the car.

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Okay, isn't Excel wonderful...

With a full tank (10gal) the weight distribution is 42/58 front/rear. With an empty tank (1gal), weight distribution becomes 40.9/59.1, a change of 1.1%. The CG moves only 0.8", not bad.

I then moved the fuel cell back to the CG of the car. This changed the weight distribution to 41/59 f/r, with the CG at 47.8" behind the front axle. (Obviously with the tank there nothing changes with the tank empty versus full.) With the tank at the front, the CG varies between 46.4-47.2". Notice the CG moves very little, and regardless, it is alway better (toward 50/50) then with it behind the seats.

In hindsite having it behind the seats would be better from a moment-of-inertia point of view, and getting it out of the way of stuff in front wouldn't hurt... but that's all knowledge for next time, right?


[Edited on 13/8/04 by kb58]

kb58 - you're application is wee bit more unique and I think that where you've put your fuel tank is a good compromise. Putting it in the front is a different matter.

Your point about it being to close to the exhaust manifolds if you put it behind the seat is a good one - we don't have that problem in the LMP because the engine runs north-south. However, I did think about the consequenses of a rear end shunt putting the engine through the tank and on the next car there will be double diagonal braces in an 'X' pattern across this bulkhead, at the moment it's in a 'V' and panelled. I have seen rival cars, that now use Audi engines instead of Hayabusa's (no names, but I'm sure you can guess...), without ANY sort of protection, not even a diagonal, between the fuel tank and the engine. That was shocking!

In reality , the only good place for 10's of gallons of higly combustible fuel to go is in a trailer, 200 yards behind you! You can do all you can to protect the tank, but if you're ever unlucky enough to be in a biggie, well, it then becomes a case of luck...

One of the solutions i found is to use a 400x800x150 cell, and to place it under the driver and passenger knees. Safe place, good for weight distribution and CG height, far from exhaust, but maybe a bit difficult for seat access. The driving position should so be something like in a F1, with feet higher than seat.

You can allways install a seat tank like they use on gyroplanes,dont know if it's safe but if it's allowed in the aircraft buisiness it should be ok i guess.
On the other hand... sitting IN a few gallons of gas...naaah.

Bering in mined that mine is a singe seater so it might be a bit different to other applications I have a citadel that is made from the front role bar the back roll bar and some side bracing between the two at the back role bar the is a bulkhead then a wedge shaped space with in its own frame and a second bulkhead witch makes up the support for the seat in the event of a big collision every thing out side of the citadel structure is designed to be shed and in doing so dissertate energy. Obviously at some point the impact will be sufficient to damage this are of car but there is only so much you can do.

any new thoughts on this one ?

The standard Seven, Book, Caterham etc. design scares me... A single "suppository" manoeuvre from the car behind and it's done...
The front box solution is only a little bit beter, since front crashes are often the most heavy ones.
In my case, a mid bike engine, between the seats and the engine is probably too close from exhaust manifold.
Remaining solution: in front of the passenger feet, symetrical to the pedal box, since the cockpit lenght can be 200 to 300 mm shorter on passenger side than on driver side.

side pods?

What about increasing the cross section of some of the chassis components and storing the fuel inside like some bike frames. It would also benefit chassis rigidity.

One thing I believe is missing from this discussion is the fact that gasoline isn't that dangerus on it's own, but it's deadly together with a spark or heat, so wouldn't it be a bad idea to put it next to the engine?

In the front, there's a larger risk that the tank would get busted, but a lesser chance get in contact with heat (?)

And half in the front, half behind seats and between engine ? It would double the pricetag, but would the risk be double or half ?

My preferred location is a triangle shaped tank area behind the seats. The main reason for this is actually structural. To get a really torsionally stiff spaceframe chassis is pretty much impossible unless there are elements in it that are complete boxes. This is hard to do round the engine, because of the access that is needed. It is impossible to do in the passenger area. The front suspension area can be done, but it is a small box and a long way from the weight etc at the rear. So a triangular prism behind the seats, with diagonals on the rectangular sides, is ideal. The tank(s)can then be slipped into this box from the side(s). This also is the base for the roll-over frame, so it is a good place to have some strength in the chassis. With this box in place, the engine mounts, rear suspension etc. can just be cantelevered of it. There is no need for any chassis rearward of the rear axle. Big weight saving. If necessary, the exhaust can intruded into this mid-section prism, but there should be several layers of well fixed metal with ventilation provission and a layer of heat proofing between this and the fuel tank. Cheers, Brian

quote:

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Originally posted by liam.mccaffrey
what about using a beer barrel

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quote:

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Originally posted by James

quote:

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Originally posted by liam.mccaffrey
what about using a beer barrel

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The problem would be finding an empty one... I mean, what one earth would you do with all that beer???



James

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Just a thought but surely it'd be safest up front anyway? I mean if you are in a frontal collision any fuel spillage will be in a forward direction due to the enertia of the fuel... AWAY from the occupants and with little to no chance of is splashing onto a hot engine which could ignite it.

I agree with the upfront part (or rather rear of the front axle.) I don't agree about the direction of fuel spray though.

You and your car are traveling forward, and so is the gas tank, and then you hit something. The front of your car stops, gas tank stops, but you keep moving for a couple feet, gas tank gets squished, spraying gas in air. Worst case, Boom.

In my mid-engine Mini, I put it just forward of the shifter, it's a long narrow cell, 10x10x24", oriented north/south. The thinking is that if there's a minor collision, nothing happens. If it's more major, meaning the car get's crushed in more then two feet (the front of the cell), it'll then begin pushing the fuel cell back into the car. It's just narrow enough that *theoretically*, it'll go between the seats without getting completely squished. And finally, using a proper *real* fuel-cell means if it does get squished, it'll minimize fuel spray, the source of explosions. The thought is that if the cell ever gets pushed back that far, it's "game over" for the occupants anyway...

Of course none of my theories have been tested yet, thank God, but then again the car's not done yet...


[Edited on 1/8/05 by kb58]