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 Post subject: Locost aerodynamics
PostPosted: August 28, 2008, 11:34 am 
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Seems like everyone agrees that the locost's aero sucks as the 0.7 Cd proves.

However, with such small frontal area, couldn't one improve the bodywork to make the little car much more efficient?

I can see how turning it into a coupe with a curved windshield, with better designed fenders, flat bottom and general attention to details can probably lower the drag by a good bit.
Of course this means a boatload more work, but hey - building is fun! 8)

Moti

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PostPosted: August 28, 2008, 12:17 pm 
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I would expect the biggest aero benefits would be to clean-up the cockpit area (window +roof + sloping rear deck), clean-up protrusions from the body paneling (headlights, exhaust, etc), and divert air around the front of the wheels. But when you start doing all that you get a _very_ different looking car. My guess is that the Donkervort coupes are going to be reasonably close to as slippery a shape as you can get and still have the car look like a seven.

That said I'm by no means an expert. :)

here's an example:
http://www.donkervoort.info/gallery/Don ... onkervoort


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PostPosted: August 28, 2008, 1:29 pm 
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Who knows about 0.7, maybe that's a seven with clamshell fenders. This is a good topic and it will be fun to discuss.

We can do lab experiments! Seems we have a decent number of folks that know how much power they have, now we just need to see how fast they can go...

It's also pretty easy to make water column manometers ( like a barometer ), so you can compare pressure on different parts of the car...

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PostPosted: August 28, 2008, 1:49 pm 
Why did I know that it would be Moti starting this topic? :)

I think the exposed tubes in the front suspension are a significant contributor, plus of course those front wheels. EVO magazine did a good article on the aero work done by Caterham when designing the CSR, see if you can dig up a copy of the issue. It's about 4 years old by now. Go with oval or teardrop tubing for control arms, a pushrod suspension to get those shocks and springs out of the way and cover as much of the wheel as possible. There's the easy stuff.


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PostPosted: August 28, 2008, 1:57 pm 
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Taken to the extreme, you might end up with a Lotus eleven-like shape. Much the same way the Panoz morphed from this:

Image

to this:

Image

Lots of chassis changes and they aren't even close to being the same car, but you can see where it starts and ends.

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PostPosted: August 28, 2008, 2:07 pm 
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It would seem like venting the radiator out the top of the nosecone could improve aero quite a lot. The 'real' nose behind the radiator could be streamlined, though not much, probably like a 1914 Renault. But at least the nose would not be so much like an open wind sock.


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PostPosted: August 28, 2008, 2:29 pm 
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many examples of full bodied sevens here:

http://www.clubmans.org.uk/gall.htm


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PostPosted: August 28, 2008, 3:54 pm 
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My brother's Super Stalker goes >150mph. How fast do you guys really want to go in a Locost?

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PostPosted: August 28, 2008, 3:58 pm 
Part of the fun of a Locost is doing more with less - I have a 148 rwhp car that will spank a Z06 at an autocross because of it.

The Super Stalker bludgeons its way to 150 mph with sheer power. Moti's bike engine won't have that option, so he has to choose the clever (aka slippery) method. And if the Stalker was more aerodynamic, it would get to 150 a lot faster...


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PostPosted: August 28, 2008, 4:17 pm 
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KB58 wrote:
My brother's Super Stalker goes >150mph. How fast do you guys really want to go in a Locost?


Cd is not all that important. If we could get some downforce to go along with the brick-like drag, it'd be awesome. Unfortunately, we get a high cd AND lift.


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 Post subject: Re: Locost aerodynamics
PostPosted: August 28, 2008, 5:13 pm 
However, with such small frontal area, couldn't one improve the bodywork to make the little car much more efficient?


Moti[/quote]

In hind sight this for me brings the question: why build a Locost if drag or lift are an issue. As soon as high speed became a stability and performance issue Uncle Chapman himself built the Eleven and anything that followed with smooth bodies. Today the market offers kits capable of better air penetration and higher speed stability. The Lotus 23 for instance can be built as a kit, the Fury and dozens of others. I modified my first Locost to make her smoother but if I was going to build a Locost again I would'nt. The picture below is not my car.

Philippe


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PostPosted: August 28, 2008, 5:53 pm 
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Jack at Kinetic is currently making fiberlass bits to assemble a more aerodynamic body for the book chassis for his "max" project. I figure he will offer them for sale to us Locosters after that. Hopefully it will be on the market by the time you get to that point.


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PostPosted: August 28, 2008, 5:57 pm 
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Well said, Philippe. We're building Locosts, not Formula Atlantic cars. Locosts are a known quantity, simple, easy to build, with little composite work which keeps costs down. But once we step outside that box (in this case, meaning <130mph) things get a lot more complicated.

Sure, we can design a 170mph car, but that entails a full body shell and more money. There's nothing wrong with that, but it moves away from the keep-it-simple-and-cheap mentality that keeps the Locost movement alive and well.

I say go for it, but really, the right way is to start with a clean design in order to get everything tucked out of the wind. At higher speeds, aero is everything.

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PostPosted: August 28, 2008, 6:49 pm 
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 Post subject: Re: Locost aerodynamics
PostPosted: August 28, 2008, 6:54 pm 
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Philippe wrote:
As soon as high speed became a stability and performance issue Uncle Chapman himself built the Eleven.

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