procomp
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| posted on 19/12/07 at 08:55 AM |
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Hi Having spent nearly 20 years with cars of this type crashing on a regular basis at quite high speed and sometimes above 100 mph. You learn a few
things.
1. Never bolt a petrol tank direct to a frame/chassis. Mount it with straps over it. Gives it more chance to move rather than just getting sheared of
it's mountings witch will always cause it to lose it's contents.
2. If independent mount it above the diff area. Not ideal for CoG. But it dose give better protection. And it is how the likes of westfield HAVE to
mount it for there race championship to satisfy the MSA.
3. if live axle mount is either above the axle or a combo of in front and above. Again not ideal for CoG but it has proved to work very good on our
own race cars.
4. Always if you can use a roll-bar that has rear stays as these will add strength to the rear section. But will still allow the rear to become a
crush able area with the tank mounted above the rear diff.
5. Side impacts or a T-bone situation are not as bad as you might imagine. This is due to the fact that these type of cars are relatively light and
means that they are more lightly to just get pushed sideways rather than remain stationary and absorb the impact. However side protection is required
to stop the offending vehicle from reaching you. But the rear wheel/tyre will take a lot of the impact unless you get hit further forward toward the
leg area. In which case one of the better ideas is to use the diagonal bar that most now fit as std ( and fitted by ourselves to every racing kitcar
we have prepared for 20 years) to the top frame at the bottom of the dash area that goes to the tunnel/intermediate crossbar above your feet. This
proved to be a good way of protecting that area from deforming when one of the locost race cars was hit in the drivers side by 4 cars all doing in
excess of 50 mph. The car was relatively untouched and the driver only suffered a badly bruised foot from where it caught the brake pedal. Car was
repaired and is back racing. But of-course if you are being assaulted by a large 4x4 then threes not a lot that will really help you if it's
trying to climb over rather than push your vehicle.
HTH Cheers Matt
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AdamR
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| posted on 19/12/07 at 10:07 AM |
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Thanks for that Matt. Lot's of interesting stuff there. No tales of locost fireballs included which must be a good thing!
I'd originally planned to build a tank to fit above the diff, but I don't think I've got enough space there to accommodate my
rather tall in-tank pump. Will look at it again.
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02GF74
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| posted on 19/12/07 at 11:01 AM |
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quote:
Originally posted by procomp
Hi Having spent nearly 20 years with cars of this type crashing on a regular basis at quite high speed and sometimes above 100 mph.
some good points but presumably these are based are locost vs locost crashes?
On the road which I imagine is most folks concern, we are most likely to be hit by a montego, 4x4, lorry, bus etc that weigh considerably more than a
locost and are much stronger.
the bottom line is, as someone already stated, drive a SAAB if safety is a concern.
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AdamR
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| posted on 19/12/07 at 11:27 AM |
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I really don't understand that attitude. Obviously no one would reasonably expect to build a seven that is as anywhere near as safe as a bigger,
heavier, more modern car. Therefore it's not worth thinking about at all?
It's a bit like saying "I notice that you're car has a passenger seat. What's the point in that when you could have bought a
bus?"
[Edited on 19/12/07 by AdamR]
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kb58
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| posted on 19/12/07 at 02:34 PM |
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It's worthwhile dicussing this. I think that far more frequent than catastrophic accidents will be fender benders or getting rear-ended at a
light at 5-10mph. In this last case is exactly where the tank is most vulnerable. Having the tank compressed at the back pressurizes the contents
until a seam bursts, spraying fuel into the air... bad news!
OTOH, many (most) "real" cars have bumpers so high that they'll completely miss the gas tank, and may in fact try to roll up and
over the car  . Regardless, doing what we can to help the situation is better than not trying at all.
"You're jumping from a plane at 10,000 feet, why bother messing with a parachute that may not work." I'll take my chances with
the chute.
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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procomp
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| posted on 19/12/07 at 03:07 PM |
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Hi one other area of the fuel tank that is always going to be a problem. Is if you have the tank filler mounted to the body and connected to the tank
via a joining hose. This will always be the weak link when the body and tank move in different directions.
This is why for MSA events the tank filler must not be connected to the bodywork of protrude through the bodywork.
Cheers Matt
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David Jenkins
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| posted on 19/12/07 at 03:37 PM |
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I worried about this for a while - then decided that a balanced approach was required (for me, that is).
1. It's much, much safer than the motorbikes I used to ride (400+ miles per week).
2. It will be slightly less safe in an impact than an ordinary car.
On that basis, plus my intention to drive it like I used to ride the bikes (i.e. everyone else is an idiot, plus the 'see and be seen'
philosophy), then I can accept the risks.
David
[Edited on 19/12/07 by David Jenkins]
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kb58
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| posted on 19/12/07 at 03:55 PM |
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quote:
Originally posted by procomp
Hi one other area of the fuel tank that is always going to be a problem. Is if you have the tank filler mounted to the body and connected to the tank
via a joining hose. This will always be the weak link when the body and tank move in different directions.
Real fuel cells have a rubber flap that closes off the filler hose in case the cell is compressed or the car ends up upside down.
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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JB
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| posted on 19/12/07 at 05:00 PM |
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Rear Safety
As has been stated it is risk management.
A home built car will never be as safe as a developed and tested production car. Especially considering that the US fuel integrity requirement is a
1368kg honeycomb barrier travelling at 88kph hitting the rear of a stationary car 70% offset.
Production cars are designed to have the filler pipe detach from its mounting/s to the body.
Most production tanks also have a valve at the entrance of the tank, that prevents reverse flow in a roll over. These would be quite easy to retrofit
into an aftermarket tank.
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vinnievector
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| posted on 22/12/07 at 12:45 AM |
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Good discussion so far , some good ideas there.
I think you have two problems one is impact resistance and the other is fuel containment.
I to had some concerns with fuel splashing around in the event of a rear shunt ,so i put a stainless rear bulk head between driver and tank this
should contain any fire long enough for you to get out and also wrap the tank in a fire blanket this should contain most of the fuel .
not sayin this by any means will save your life but some is better than nowt .
the impact side is a matter of weight to beef up the rear structure and is down to you .
[Edited on 22/12/07 by vinnievector]
[Edited on 22/12/07 by vinnievector]
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Doug68
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| posted on 22/12/07 at 05:42 AM |
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I'm looking into using a plastic fuel cell such as those made by JAZ. If I can get one to fit in my design.
If I had a bigger budget I'd go for a bladder tank, but the bladders have a fixed lifespan too.
Plastic tanks do not have seams to split and are highly deformable so I think that they are a good compromise between a plain welded item and a full
race tank.
Doug. 1TG
Sports Car Builders WA
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kb58
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| posted on 22/12/07 at 05:53 AM |
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Except that the plastic used is (I think, polyethylene) which is very slippery. What I mean is, you can easily stick a knife through it. This very
topic is touted as a reason by the fuel cell companies why you're supposed to use only "real" cells.
It's always something.
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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Doug68
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| posted on 22/12/07 at 06:12 AM |
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I guess you cant win.
KB58 what did your cell cost BTW?
Doug. 1TG
Sports Car Builders WA
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kb58
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| posted on 22/12/07 at 06:08 PM |
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About US$800. All my gloom and doom aside, I don't know if I'd spend that much next time. I may concentrate on protecting it to the point
that I feel comfortable with a plain box (though it will still have a roll-over valve and foam.)
[Edited on 12/22/07 by kb58]
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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