Active aero system on track car

Projects General Guidance
1

Hello !

New on here, and in no way am i a tech or engineer guy. Completely no idea how any of this works, but more than willing to learn. I'm not too shabby at figuring out what needs to be done but not always able to work out how to do it :smile:

I am in the process of building a track car, chassis pictured below :

1067×800 221 KB

Yes it has 3 wheels, and thats the reason why i'm here.

Although generally fine on the road in normal use, a three wheel chassis like this will not handle bends at higher speeds.

Rear wheel drive, the engine where it is, and no wheels in the corners at the front make turning somewhat of a wonky situation.

Basically, the front corner of the car inside a bend will want to lift due to the centrifugal force that applies to the car.

My theory is that if downforce was applied to that lifting corner during cornering, that would help ?

However, here comes the challenges :

  • It needs to be only on the one corner

  • Therefore it needs to be able to alternate from left side to right side depending on the bends in the road

  • So if the system can be deployed thanks to a lateral G sensor type thing, that would be awesome. The force input at the entry of the bend would trigger the corresponding flap ?

  • Maybe the flap deployment needs to be gradual ? Not necessarily needed to be full open on a faster bend ? (That i have no idea)

  • Not always needed to be there, when the car is driven moderately or in town/quick runaround i wouldn't need flaps to be in and out, so being able to disconnect it at a switch would be great.

My idea is to make two flaps, fitted and hinged to the front crossmember, either side of the front wheel.

After searching and getting lost through the internet, i discovered Arduino, and what seems to be an enormous technical potential.

I have seen items that have multi axis accelerometers, for example ?

This and this would be good for my project ?

  • Nano 33 iot
  • Nano motor carrier

I read on another website that the Nano 33 IOT has a 3 axis accelerometer ? Is that true and sufficient for my needs ?

Coupled to something like these high torque compact servo motors, with leverage calculated to open it enough

?

Does any of this sound like a good idea ?

Thanks !!!

2

Welcome to the forum

Before going any further I would test your assumption that you can apply enough downforce to a front corner to prevent the tipping. You can do this with a fixed vane initially

3

That is a good point.

Extra info : the car will weigh 425kg, and the engine swapped in will make it good for 140 mph.

As for the downforce effect potential, these cars were sometimes fitted with this glassfiber splitter, like this :

720×537 57.6 KB

I've recently asked if this was of any effect at higher speeds to keep the nose down, or if it was just for looks, but two owners confirmed it was an addition to the driving experience they wouldn't go without

Obviously, on that example, it is quite a surface, and i wouldn't be able to equal it due to where i plan on fitting, however, flaps under the car will be in direct line of the underside airflow, so i'm hoping it can work ?

I have no engineer degree and absolutely no knowledge on how to simulate this, i'm just trying to figure it out on an amateur level :slightly_smiling_face:

4

Don't simulate it, do it by fixing a deflector on the car and testing whether it is effective

As to the Bond Bug, I came very close to buying one when it was announced but though better of it

1 Like
5

Yes indeed it'll be on the road unfinished/unpainted first so i can easily weld temporary brackets on the chassis to fix a mock up to test.

Other than that, if confirmed it is effective, it would be possible to parameter a functional system ?

Thanks

6

You could certainly detect the forces involved in tipping the car and deploy anti-roll vanes to counteract act it. You should consider using a PID to control the deployment in proportion to the forces

However, you need to know how large the vanes need to be, their best angle of attack and their best position on the chassis. For instance, suppose that your experiments showed that the vanes had to be a square metre in size, would you still pursue using them ?

7

Good points

PID is acronym for ? And how does that function ?

Looking at current sports/supercars that have active aero or airbrake systems, the size of the vanes do not seem massive in relation to the size and weights of the cars

Obviously, many many items factor in to how these real car equipments are built and sized to be efficient.

If i do need 1 square meter of surface for a sizeable downforce effect i might have to go without indeed, thats about half the frontal surface of the car :smile:

Lots to think about.

8

What speed do they travel at compared to your vehicle ?

1 Like
9

Thanks for that.

Regarding speed factor.

Original Bond Bug :

700cc, 29 hp, 4.8 kgm, 395 kg

Project Bug :

I can expect around 230 hp and 17 kgm torque for around 420 kilos of car with the engine being used.

230hp/420kg = 547 hp/tonne

Pagani Huayra (example of a super performant car with extensive active aero) :

740hp/1350kg = 540 hp/tonne

So although due to gearing, I know a similar top speed cannot be matched, and of course, motricity etc also not be as efficient due to shape of my car, 100% no computer assistance, but i know for a fact that i can still expect 0 to 60 time in around 4 sec.

Obviously i cannot aim for as good a peak road going capacity with what is basically a motorised wheelbarrow built in my shed, but there is concrete evidence that this car can be made to lay down serious power. In a straight line.

My endeavour being to do the best i can in the power use department while cornering :smile:

10

I am tempted to quote Marvin. :roll_eyes:

11

Please do, if the comment will be of any use at all to any of my questions about active aero vanes

12

The problem , as I see it , is you can roll one of those at 20mph - can’t see anything aero stopping that .
Why not have 4 wheels , could still get under a bond bug body - been done before !

13

Is that based on your experience watching Top Gear or actual experience of driving one ?

14

The logic seems very simple.... When you hit a certain G-force you activate the wing. The Arduino can handle that.

But mechanically it has to fast & powerful... The more downforce, the more power you need to activate it "against the wind".

Race cars usually have larger wings and other aero treatment and they would be even larger if there were no rules. Sprint cars seem to have the largest wings and I don't know if they have any limits.

The wings on F1 cars don't seem huge but there are multiple wings as well as the shape of the body and the underside (with low ground clearance) all working together.

F1 seems to be one of the few racing series that allow active aerodynamics ("DRS") but there are LOTs of restrictions.

15

Thanks for that constructive input

If i wanted pure efficiency, i would buy a Lotus Elise and build a 300hp turbo Hayabusa engine for it.

It is quite obvious that the chassis that i built pictured above has been majorly redesigned over stock form, in order to improve the road performance of the car. (Surely the extended wheel base, independant rear suspension and 50 extra cm of track width was obvious enough ? :thinking::smile:)

Now i just need assistance in seeing if aero is possible to increase it further. And on paper, if the system seems doable, its very encouraging.

I will not go into debating the clichés around driving a 3 wheeler, it's stale and boring, and this isn't a car forum :+1:t2:

16

@DVDdoug

Good points you mentioned

I've seen very very compact servo motors that quote dozens of kilos of force in pushing
Is that what you mean by needing brute force to deploy and counteract the airflow ?

I'm hoping that the very small and lightweight car that it is could be influenced thanks to not so enormous vanes ?

17

Not about that - you can’t generate downforce at slow speeds , three wheelers can turn over at low speed ( unless 2 wheels at the front , one at back ) . Both are facts that you must consider or you’ll waste a lot of time and money .

18

Maybe think about how the tilt train works.

19

you can’t generate downforce at slow speeds , three wheelers can turn over at low speed. Both are facts that you must consider or you’ll waste a lot of time and money.

What kind of experience do you have driving 3 wheelers ?

Is it possible to make a 1F 2R 3 wheeler handle as well as a normal car ? Simple answer, yes it is.

Is it possible for the bond bug to as well as that ? Simple answer, no, due to the dimensions of the car and engine position, among other things

However, is it possible to make such a car handle much better ?(and not roll over at 20mph ffs drop that bullshit) simple answer, is yes, because thats what i've done developing the chassis for the car i'm building.

And finally, whats this thing about no speed ? What part of 500hp/tonne don't you get ?

I am only looking for help on how i can setup the alterning airbrake type system i think could be of help to assist cornering with the car.

20

Frankly, I think you should just put "trainer wheels" on each front corner of the car. :grin: :+1: