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Topik: Please tell me what does the physics of center of gravity do in RL |
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#1 dikirim Jun 5 2019, 16:55:42
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Aside from riding low or cutting your suspension to do so, does, for example, tyre diameter, seat position (low-hi height), and anything else influences this ?? Why are Porsches, Paganis and other cars with Rear engine and rear wheel drive, so suited for races (as F1 cars?) Please tell me some of the physics that goes into it in real life for racing cars.
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#2 dikirim Jun 5 2019, 18:31:38
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This is entirely based on the physics that go into a Skoda Fabia R5 and Subaru Impreza in rally trim as thats all I do.
The centre of mass should be as central as possible to the vehicle, this can be changed by adjusting the ride height on the four corners, adding balast etc. The way mass should be in the ideal situation is RR + RF = LR + LF, FR + FL = RR + RL. If its too heavy to the rear you get understeer, too heavy at the front and you get oversteer. On gravel especially the centre of mass has a big effect on braking stability.
Tyre diameter is fairly simple, the more tyre thats in contact with the surface the more grip you have, you can adjust this by changing the toe and camber, this is more for circuit vehicles where there will be more of one corner direction and a set ratio of corner/straight. With rally cars we just need a generally right set-up so we don't favour left/right hand corners. Camber and Toe can effect temperature gain and wear as you don't want scrubbing of the tyres when going straight and you don't want the entire tyre in contact when going straight in an ideal world for friction but when cornering you want as much as possible.
Seat position is a big thing with rally cars, the co-driver seat is low and backwards to bring the centre of mass to the centre and as low as possible to prevent roll when cornering as a high centre of mass will cause roll taking weight off the inner tyre and putting it all through the outer tyres causing understeer.
Some other interesting things is differentials, brake bias and brake discs. Diffs just allow the power output through the wheels to be independent, the Fabia has two, one for the rear and one for the front. This prevents one wheel slipping while the other is driving helping rotation and acceleration of the car. Brake discs are fun with rally cars compared to other sports, same with the springs. We have 3 different dampers, Tarmac(low ride height, small travel, stiff ride), Irish tarmac(low ride height, low-medium travel, fairly soft ride), gravel(can be anything from medium-high, high travel, soft ride). the smoother and harder the surface the 'harder' you can run your suspension set-up as you need to get the balance between, high corner grip, minimum necessary roll while preventing damage to the floor from bottoming out or rocks and not causing the car to bounce when the damper runs out of travel. Brake discs usually we only have tarmac or gravel as stock, Tarmac are larger discs so greater surface area, allows more pressure and greater braking force as more contact between disc and pads. We do sometimes mix gravel discs with tarmac with one of our drivers due to his style, this allows on loose tarmac(lots of debris) or clean gravel for a good braking efficiency without causing locking of the brakes but giving plenty of usable pedal without it being too touchy. Gravel discs are small and less effective, they prevent locking on loose surface and don't get as hot as gravel is usually slower and doesn't cool them as much.
Circuit racing is a bit different to rallying but its got a lot of the same basic concepts, there are some great tech guys on the internet who explain things well.
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