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Originally Posted by Divefire
Oh dear, this might not go down so well but bear with me…
Aerodynamics, down force, on a scale buggy doesn’t really exist. Ok now before you throw your chair at me, let me explain a bit.
Yes I know, body shells and wings make the cars handle differently, and that’s a fact but it happens because of the drag being produced not because of downforce. Why not? Well because air density increases with speed, and at the speed the buggies get up to, plus their rather small size, it’s not enough to produce downforce. There’s not the surface area or the speed there.
So how are your normal wings and bodies producing more grip? Basically drag. If you look at a high downforce wing or a touring car body that people say gives more front end, usually they have a very steep front profile. This produces the drag. Drag itself doesn’t produce more downforce but what tends to happen is a cushion of air is built up, increasing the density more then in other areas and thus pushing the car down a bit. Of course at this point the air is having trouble flowing over the car so it isn’t terribly efficient but that doesn’t matter so much on scale racers.
So how does this relate? Well making parts aerodynamically efficient is a bit pointless in this scale. Yes if you’ve got a giant front upright you’d want to try and find a way to minimise it’s drag impact, but that’s about it. Making things like wishbones so they’re an aereo device won’t help, they’ll be no better then a conventional one.
Of course on the subject of wings there is a school of thought that says a multi element wing would produce some efficient downforce, but it would be rather fragile and at the end of the day be no better then a drag inducing wing for our purposes.
Sorry if that comes out a bit know it all, and feel free to argue, aerodynamics is a black art at the best of times. Now if we could just come up with some decent body shell cooling ideas…
Oh on the subject of the actual car design itself, I’d go with mass centralisation, a balanced left to right weight distribution and then find out what front to back weight distribution works best, probably around 55/45. And then there’s suspension geometry and all that fun stuff to play with… Good luck!
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I am throwing the chair at you .... Due to chavs thinking sticking a wing and body kit on a car dosen't produce drag.
Drag co efficient is a contant for a particular body it is usally work out in the wind tunnel or doing a coast down test.
All object passing through a fluid produce drag the more the is fluid displaced the larger the drag. Two of the biggest factors of drag is frontal area and the wake it produces the bigger the wake the more drag, wake can be considered a vacuumm sucking the object back in opposite direction to which it going. Note tricks have being done to over come this such as the ford KA it actually produce a positive pressure on the back of the car which pushes the car forward.
Wings work by creating a pressure diffence by being asymetrical profile this forcing the air to move faster over one surface than the other. The longer suface of the profile will create the lower pressure as the air is moving faster look up bernoulli equation. the diffence in the pressure creates a lifting moment (effect) around the center of pressure.
As a since a wing is a body being passed through a fluid it has a drag co efficient naca wings can vary bettween 0.1 to 0.5.
Next thing is the relativity air isn't scalable but it has a scaleable behaviour inorder to allow very small thing such as bee to fly and very large things to fly such as 747s.
When bee is flying the bee wings are flying through treacle , when a scale aircaft flys the air density factor is something like water otherwise scale wings just wouldn't work. Note air desnity is a constant relative to altitude and temperature. air pressure drop due to increase in speed but drag force increase due to increase in speed.
so buggy wing do provide a large contributing factor.
Any body or object that has an asymetric profile can by considered as wing in term of produce + - monment of lift. most road car produce + lift due to fact that the body upper profle is longer (bonent font window roof rear hatch) than the lower profile ( bottom of the chassis). Modern car use of good ground effect and front splitters and rear wake minimiation have contributed to reduce +lift and creating - lift. Where the air has to change direction in severe manner such as where the bonnet meets the windscreen create high point of pressure pushing agianst the body. This produces a - lift force but it also is considered ineffient way of produce - lift as too much drag is created for the amount of - lift. A touring car shell it will produce + lift due it has a longer upper profile but by creating -lift at the front rear of the car you can conter act it and over come it but with the price of increasing overall drag.
I have mention soming called the center of pressure c.o.p this the point of the sum total of lift force act on the body your main aim here is to create equal moments of either side of for a body to keep the c.o.p in the center of the body to feels stable if you don't you get a moment of torque or the c.o.p shift towards the front of the rear of the body. some bodys do shift the cop to the back or the front to reduce or increase steering.
Sorry for long post but i would rather point out the correct facts of the black art than have everyone think incorrect facts are right,
