structual help (lightening a track car)

[Disturbed1]

im building up an extremely budget track car to be used mainly for drifting however will be dragged also and possibly some timed events also.

now the approch to this car at the start was to make it as light as possible and aim for a 10 sec pass on a very small budget and although that is a goal i will attempt, i dont have an engine package to get those numbers yet so concentrating on the chassis side of things.

the car in question is a mk3 supra which hit the scales at 1180 kg (ready to race) but will prob weigh closer to 1200 now that i have the bolt in cage and heavier wheels on. and currently has 350 rwhp (still a huge power to weight increase form 1550 kg and approx 200 hp)

anyway, im keen to know what is actually considered structual in a car chassis, im trying to make the car lighter still and theres a couple of parts im keen to cut out but dont know if they are of any importance




if its not obvious - this is the b-pillar which has a fair bit of support for the factory seatbelts




and this is the seat mounting spot which i would like to remove inorder to hard mount the front seat lower as currently - my head touches the roll cage

is there any other common places i can drill holes/cut out which could help my diet? i know im only fighting over a few kg's here and there but every bit helps

[BlitzRacing]

use a hole saw and saw out nonstructural parts of the vehicle.. Even on structural, holes wont be too bad, much better than cutting the complete area out

its the easiest way to reduce dead weight for cheap.

I'll start by,
hole sawing the bonnet, and boot lids, then with area in which the cage supports, then hinges, front and rear inner fender areas,

[oldcorollas]

your B pillar and roof, contribute to the structural rigidity of the car.

however for drifting and drag, this may not be so much of an issue as the side/twist loading will be much lower.

that seat rail adds some rigidity.

i wonder what would help to support the rear of the cage.. if you cut out that yellow sectin in firts pic... it is then mounted to an unsupported flat surface.... kinda useless really.

if you were adding a comprehensive cage, braced at specific points, then it can provide a fair bit of structural stiffness. but you might wanna check CAMS manual to see if you can tie into suspension points or not.

you might wanna consider safety over 10's of seconds, since dorifto is not even timed, and drag is more abotu the power and traction, than the last 2% of weight

[Sam_Q]

I would of thought that if you had an X section in the rear part of your brace it would negate any need for strength in that area. Good job in getting the weight that low in the first place. Do you have any more interior pictures?

I assume the doors are already gutted right?

[Disturbed1]

yeah ill dig up some more pics orelse take a few but the doors dont have the actual trims on but i havent hacked them up as i still retain the power windows. dont like idea of trying to make them manual or converting to fixed lexan as i like being able to get fresh air

[Disturbed1]

dont laugh too hard - i know its messy and needs tidying up, the wiring and most other aspects of the car were rushed inorder to get it running for a particular event












im not runnin any dash or anything

[Sam_Q]

just a few random ideas:

have you cut the intrusion bars out of the doors?

how about have a lexan window that has a removable clip or something to hold it in place?

lexan or acylic windows for every other window in the car?

what about that hatch, hatches are normally heavy, assuming it isnt already can you change that with something composite with an acrylic window

how heavy is that big metal dash support bar? can you replace it with a piece of 44 x 0.9mm Cro-mo?

that roll cage, is it cams approved or can you change that to a thinner cro-mo cage?

[oldcorollas]

LOL, cos side impacts never happen in racing.. or when you are sideways with another car

lexan windows are very hard to break, some say that side windows shouldn7t be lexan so if you roll you are not trapped in burning car...
lexan and acrylic are also reasonably heavy..
glass is abotu 2.6g/cm^3 (almost same as aluminuium!)
lexan and acrylic are abotu 1.2g/cm^3

anyway, work out the area of the glass, multiply by thickness = weight (or divide weight by thickness to get area), then see how much weight you could save by changing...

chromoloy is starting to get into cubic dollar weight reduction
but hey, if you have cash to spare, and the weight means that much..,.?

edit: is that a sealed gel battery? would suck to roll onto side of car and have acid dripping on you

[Sam_Q]

well I would of thought thats the cage would be for.

I see what you mean about the calculations for the weight saving on the glass, however I would of though it would be possible to reduce the thickness of material as well? I dont know as I havent played with it.

[Sam_Q]

oh and thats an interesting point about not being able to get out of the car if you have lexan/polycarbonate windows, I never thought of it. On another note it probably burns faily well too unlike glass. Acrylic is tough but can be broken though, from experience I found it can burn but slowly.

[Disturbed1]

yeah the battery is a sealed dry cell.

thought about lexan windows but for andra specs, it needs to be 5mm thick i think, not only expensive but couldnt justify it for the weight savings

the doors are standard from factory, i havent cut any metal from them at all

that dash bar is light as but will be replaced by a chromolly bar as im going to fun a fixed steering column to save the weight in that department

[greatbuzup]

Nice working getting down to 1200kg.

CAMS recomend mounting seats on bars that run laterally from sill to transmission tunnel as it provides a higher level of safety in a side impact. If you're gonna weld in other lateral bars to mount the seat on then you could ditch the factory one, but otherwise leave it.

The B-pillar adds a lot of rigidity to the car and will help you in a roll over. I dont see a problem cutting a few holes in it though. There i a science to cutting holes though, you need to figure out the force flow through ay component before you cut any material away.

Gut the doors for sure. ditch he intrusion bars and add in roll cage from B pillar to A pillar instead. it'll be better in a crash and add rigidity, probably wont weigh much more than the intrusion bars either. You really only need doors to keep the wind out so go bananas on them.

Also, weld a bar between the rear struts. Pretty much anything behind this line will do very little for strenth/rigidity so go bananas there too.

[oldcorollas]

CAMS recomend mounting seats on bars that run laterally from sill to transmission tunnel as it provides a higher level of safety in a side impact. If you're gonna weld in other lateral bars to mount the seat on then you could ditch the factory one, but otherwise leave it. .

it might be worth running a bar under the floor, and bolting the seat to that.. and tieing it back into the bit that goes over the tunnel to keep stiffness.

[Sam_Q]

I second that, I think its an ingenius idea, if you dont want to have something hanging down too low there is a loopy idea thats somewhere inbetween: you could take out the current support and in its place chop a slot right though the floor thats the same width as a cro-mo pipe and weld the pipe in so the floor ends up being welded back to the middle of the pipe. Its my reasoning that there will be a very direct flow of force and it will be somewhat easy to package, please excuse me if its a dumb idea.

[Disturbed1]

i like the idea of un-picking the spot welds or original support and just welding in a another lower 1