Allan_s2rx7

I have an idea and have some carbon fibre sheeting to test it on.
Basically i want to make a wider than normal Cf chassis for my sprint 2.
Hoping to get the wind to travel under my car and out the back rather than being "trapped" under/inside.
Also anyone tried this or a diffuser etc when running at high speed? Eg anything over 80kmh. My 1/10 pushes 95kmh and im worried it will take flight.

I Might also design a rally style sealed cf sprint 2 chassis.

mleemor60

iTrader: (28)

I am currently working on a similar idea. Not for terminal velocity but for a combination of protecting the rear corners of the car from angular impacts which tend to knock corners off the car and creating a smoother air flow under the chassis to combat the parachute effect of air build up under the body thereby adding lift. There are some unanswered questions to be addressed in a road racing environment such as dragging the edge of the chassis during cornering without compromising the existing set up.

Keep us all up to speed on your progress.

MatsNorway

That is why you cut out the rear bumper to get that air out

TOM MAR

iTrader: (3)

CRC has this for the rear...
https://www.teamcrc.com/crc/modules....prodID=7719473

VegasHB

Read this thread

http://www.rctech.net/forum/electric...o-secrets.html

stormridersp

I never simulated the aerodynamics of RC cars, but in reality, any on-road chassis has a lot less grip running without the bodyshell than with it, which leads me to believe that the bodyshell is actually providing a convenient low pressure volume by itself.

Nerobro

iTrader: (2)

You also end up with the volume of the shell as "weightless mass" to allow the suspension to work against it. Even without "aerodynamics" The free weight to work against is going to give better traction.

Allan_s2rx7

That does work. I know that method. Does not work as well as having it go under and away..

Allan_s2rx7

Umm do you have a version in english??

Nerobro

iTrader: (2)

Sure! How about a physical demonstration?

First things first. Air is springy, and sticky.

Grab an uncut r/c body. Set it down on the table. Go wash your hands, dry them well, then rub them till they're warm and tacky. Put your hands on both sides of the body, and try to pick it straight up. You'll feel the body try to "suck" to the table. It'll fight you.

This is a combination of air wanting to rush under the body, and you trying to move a big chunk of air as well! Probally 40-50g of air.

Drop the body, watch how fast it falls. As it gets near the table it'll try to hover and run away. That's the body trying to squeeze the air out from underneath it.

Basicly, any motion of the body near the ground has effects with the chunk of air around it, and interactions with the ground, that make the body seem much heavier than it is, when you look at it at the speeds that our suspensions work at.

If you'd like to see the same weight, and how it behaves when it's not grabbing a big chunk of air with it when it moves, cut out a sheet of cardboard that's the same weight as the body, and stand it on edge. See how fast it can go up and down in comparison to the body. Especially in proximity to the table.

scirocco14

iTrader: (5)

Interesting.

I did a quick calculation and came up with a volume of around .006 cu meters of air in the body. 420mmx200mmx100mm, with an adjustment for the shape of the greenhouse. Air density at stp is 1293g / cu meter.

So 1293 x.006 = 7.8g of air.

Still not insignificant!

Airwave

iTrader: (1)

Why do you say that the air is trapped under the body?

With a wide chassis you will have other problems...
Bernex 07/09/2002

Nerobro

iTrader: (2)

The body will also be moving a large amount of air "outside" the body. The whole "air is sticky" thing. Lets be fair, and call it 15g. :-)

Now I really wonder, what kind of difference that makes.

DesertRat

iTrader: (2)

For straight aero efficiency and keeping lift out of the car, you will probably not do better than a straight air dam as low to the ground as you can get it.

You want air to go over or around the car, not under it. Every sedan-type car has, for lack of a better term, an 'air bumper' of high-pressure turbulent air in front of the nose. You want this high-pressure air to go over or around the car, not under where it can generate lift.

https://robrobinette.com/S2000Aerodynamics.htm I came across this in a google search, it illustrates what I mean.

Racermac73

iTrader: (3)

I tried it on 8th nitro on-road and 12th scale, both cases the cars were MUCH slower. Tons of downforce and corner speed seems great.. also takes tons of horsepower to pull it around the track. Good advice.. don't waste your time and money