Atom 4 - Just a no no no...

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hamtt
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Atom 4 - Just a no no no...

Post by hamtt » Sat Jul 04, 2020 9:43 pm

It's that time again where I stick my neck out and get slaughtered by the factory die-hards...

BUT

I can't just sit and watch things like this and not get irked by them.

The Atom 4 wings. The factory have really dropped the ball on this. The design I just don’t understand or get. I've spent days/weeks trying to understand it and looking at it and it still doesn't make sense. They've been telling customers and potential customers that unlike the previous cars, the 4 was designed with aero in mind and so the wings have a significant impact and provide significant downforce. They may very well provide downforce but the sacrificial price to pay is ridiculously high.

What am I talking about? DRAG - the enemy of speed.

Both the front and rear wings have vertical lips on them that do absolutely nothing except provide drag at a ridiculous rate. Drag increases at a rate proportional to speed-squared. That means as you go faster, the drag increases exponentially, so the drag caused by these lips at higher speeds is going to be ridiculous.

Image Image

A car aero wing is basically an upside down aeroplane wing. Do you ever see aeroplanes wings with these lips? What about any F1 cars?

A wing is supposed to create lift or downforce by creating a difference in pressures above and below the wing. This is achieved by splitting the air in half and creating a cross-sectional shape of an aerofoil that makes the air travel faster on one side of the wing than the other (they have to meet at the trailing edge so if on one side of the wing the air has to travel further, it will go faster, thus less pressure). This difference in airspeeds (and thus pressures) above and below the wing is what creates lift or downforce. This lip design not only causes drag but also interferes with the meeting of the air at the trailing edge that's been split. It's just messy all over.

If you don't understand what I mean, the next time you're in your road car going on to a motorway, stick your hand out of the window and hold it perpendicular to the road. As you accelerate you'll notice the wind pushing your hand back significantly more as you go faster. At about 60-80mph you'll be struggling to to keep it steady. This lip is basically your hand, except going all across the width of the car and at two points. Not only that, it;'s going to distrupt any downforce created by the wing from the "proper" way too.

If the wings are meant to be purely a cosmetic accessory then fine. But at 6k a pair and being marketed as providing real downforce then I'm sorry, it's just no from me. You'll get better grip around corners in spending 1-2k on a set of custom wider rear wheels and going up 20mm a tyre size (or slicks) and increasing your mechanical grip than you will with these. And as for your top speed and your acceleartion at 60mph+, that's gonna suffer no doubt.
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Re: Atom 4 - Just a no no no...

Post by CAG3D » Sat Jul 04, 2020 11:49 pm

Definitely gonna get slaughtered.........


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Re: Atom 4 - Just a no no no...

Post by hamtt » Sun Jul 05, 2020 5:08 am

I've written my last will and testament...
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Re: Atom 4 - Just a no no no...

Post by phil4 » Sun Jul 05, 2020 6:40 am

It's just not that clear...

As you know, drag slows you down, but what you didn't mention is that with a wing, increasing down force increases drag. So even with the conceptually very simple wing you're already making trade offs as to how much downforce/drag you have.

Then there's the more complex aspects, what happens to the air before and after it goes over the wing, how that affects drag, stability and downforce.

It's why F1 teams spend so much money and time tweaking their wings year in year out... because there's not a "perfect" easy solution they can all apply, and why they have wind tunnels and use CFD to try and predict how it'll work. Because it's not as easy as just looking at it and going "that will work".

Take that small lip on the front spoiler. Yes, in rudimentary wing design you don't want that. But this isn't rudimentary 101. It could do all sorts of things that you'd only find out from testing/CFD, things like kicking the air out from the front tyre and reducing drag and lift there, or creating a vortex off the wing, which then carries the air up over the car. And as above, even then it'll be a trade off.

I guess what I'm saying is it's not as simple as you state.

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Re: Atom 4 - Just a no no no...

Post by stupot » Sun Jul 05, 2020 6:43 am

Those vertical lips are called gurney flaps.

I am no expert but a gurney flap is a small lip placed at the trailing edge of a wing, used to dramatically sharpen the exit angle of the airflow, thereby creating more downforce without the downside of drag that a car would have from a steeper wing angle. It's named after ex-Formula 1 driver and team owner Dan Gurney.
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Re: Atom 4 - Just a no no no...

Post by autobackup » Sun Jul 05, 2020 9:33 am

Looking at it carefully it appears to me as if, in addition to providing downforce, it's designed to lift/deflect the turbulent (draggy) airflow up over the car to reduce body drag and also increase the airflow towards the rear, much higher mounted Atom 4 wing, in an attempt to achieve a double effect by making the air work harder?

Many modern aircraft wings have rear flaps that float up to create a small negative camber angle (-1° to -3°)
when fully retracted during high speed cruise which has a very similar effect to what I think Ariel is attempting to achieve?
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Re: Atom 4 - Just a no no no...

Post by CAG3D » Sun Jul 05, 2020 11:02 am

Isn’t the top speed still 155mph ish? If so, other than aesthetically, I’m not sure how much of a difference it can make, with a car that is made of scaffold poles.
When a car can get to 100mph is 6 seconds, logic tells you it don’t take long to get to 125mph, the top speed being 155mph, then the Aeros don’t have too much work to do.
I was hitting 150mph on the straight at Bedford, and I can’t feel the Aeros of the car struggling. I know mine has the old wings (3.5R) but I don’t believe they are anything but for looks.
I’m not keen on the 4’s wings, I’ve only seen pics, but the rear one looks particularly odd, I’d be concerned by low level bridges....


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Re: Atom 4 - Just a no no no...

Post by autobackup » Sun Jul 05, 2020 11:56 am

CAG3D

Like you I have a 3.5R with the factory wings and at Silverstone 2 years ago I was getting 162mph indicated (both on the digital display and the satnav) down the start/finish straight.

I have tried with and without the wings fitted and have come to the conclusion that in my opinion that they do work but not with any noticeable effect until a speed of 50 - 60mph is achieved and even when driving faster I think that while ok in a straight line the wings lose efficiency in the corners due to the cross turbulence created by cornering effect?
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Re: Atom 4 - Just a no no no...

Post by Spikey_head » Sun Jul 05, 2020 4:40 pm

What were the results of the FEA?

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Re: Atom 4 - Just a no no no...

Post by GraemeW » Sun Jul 05, 2020 5:25 pm

Hamtt’s explanation of airflow across an aero foil is correct, but I just googled F1 aero foil and looked at them. Most of them have the same small vertical lip on the trailing edge of the rear aero foil. So there must be a reason for it ?

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Re: Atom 4 - Just a no no no...

Post by CAG3D » Sun Jul 05, 2020 5:29 pm

But these cars don’t do 200mph


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Re: Atom 4 - Just a no no no...

Post by GraemeW » Sun Jul 05, 2020 5:50 pm

I think this explains it. The Gurney flap added to increase downforce without having to increase the angle of attack which causes excessive drag. Increasing the angle, increases downforce, but causes the drag. The Gurney flap is the compromise solution to get the same effect but without the same drag. I think Ive understood that right?
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Re: Atom 4 - Just a no no no...

Post by GraemeW » Sun Jul 05, 2020 6:14 pm

another explanation. So Ariel are right in this design
http://www.formula1-dictionary.net/gurney_flap.html

Anon

Re: Atom 4 - Just a no no no...

Post by Anon » Sun Jul 05, 2020 6:37 pm

F1 has been using Gurney flaps since at least 2012.

Mercedes 2012 - looks like the Atom 4 wing.
Mercedes w03.jpg
Mercedes w03.jpg (82.83 KiB) Viewed 1077 times
Mercedes 2016:
Mercedes 2016 wing.jpg
Mercedes 2016 wing.jpg (140.16 KiB) Viewed 1077 times
Mercedes 2019
Mercedes 2019 wing.jpg
Mercedes 2019 wing.jpg (193.56 KiB) Viewed 1077 times
Just because we don't drive at 200mph on track like an F1 car, try driving a car with proper aero like a Radical and even corning at 100mph you can feel it pushing you into the tarmac.

We know gurney flaps add drag in fact all wings do which is why F1 added DRS recently. But the benefit is more down force and more stable air flow. I am excited in trying them on track and even on the road - the road less so of course. Plus they look great, really thick carbon fibre.

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Re: Atom 4 - Just a no no no...

Post by CAG3D » Sun Jul 05, 2020 7:09 pm

I clearly can’t push a car like you guys do, downforce, 100mph cornering etc, the 2 track days I did last year, I just put my foot down and hold on for dear life! Still, not many cars can get past my average driving.
I will be interested to see if I get to follow some of you more experienced F1 esk drivers around a track, to see how much faster you’ll be against an old SC car with a fat bloke driving.


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