Lotus Elan Central

Whilst I'm in an aramid fiber funk, has anyone thought of doing a front Carbon/Kevlar front undertray for the Elan to give better ground effects? A problem I have is when the car reaches around 120-140MPH the front end begins to lift abit. I think this is because on the Fed versions of the car the radiator is angled slightly downward allowing too much air under the car creating lift. Would this seem feasable? I was thinking of building an "undertray" of sorts to angle the air back up and out the vents I placed in the top of the engine bonnet. In essence creating more downforce or at least counteracting the lifting that happnes at those speeds. I have an Esprit front splitter on the car currently, and though it helps the effect I'm ready to take it to the next level.

http://new.photos.yahoo.com/lotusgirlma ... 8770149/39

You can see the splitter in the pic of my car.

Yo, Marie, pretty sure it was Alan Betts of AB Motorsport fame who did a CF undertray exactly as you ask -- not sure if anyone ever bought one?? Had a pic of it somewhere? You should contact him to ask more info. Knowing you, you would probably make your own, but you could get R&D info and use info from him likely.

When i had my car at Pheonix for wheel alignment, Oli the mechanic was supprised not to see an undertray and said the car would benefit from having one fitted. He showed me the ones he has made up for the elise and there just a sheet of aluminium. So i was thinking of something similar in the future, at the very least it`ll stop the gravel get in when i go of track lol.

Just after the war, my father used to work at Frazer-Nash, helping to build cars like this;

http://www.carandclassic.co.uk/car/C07246

They had BMW328 engines with magnesium sumps and were concerned because the sumps used to get damaged by stones .. ... so they fabricated an alloy sheet under the engine bay. When my Dad went out to test drive one of the cars after the mod was in place he was surprised to find no steering effect above 120 m.p.h. This was because the front wheels were more or less off the ground. So, take care with this sort of mod.


Cheers

Jim

lotusgirlmarie wrote:Whilst I'm in an aramid fiber funk, has anyone thought of doing a front Carbon/Kevlar front undertray for the Elan to give better ground effects? ....
You can see the splitter in the pic of my car.

I was talking about this today and then saw your post!
There is a small under tray as a product; fitted each side of the bumper with a turned outside edge (to reduce the vortex I suppose) I saw them on a German Elan; Might be worth integrating to your neat project, I would.

Your tray should reduce the turbulent air both around the outside of the bumper and inside the engine bay for stability.

The Elise was designed for air to flow up through the front end to give down force on the front wheels (although it didn't have an engine in the air flow).

Good idea by the way!

Phil, Any pics? I'd love to see what the German Elan's look like on the underside.

Muley, I hear ya loud and clear, This is part of the reason why I was only going todo a bellypan that goes to the downpipe. The other reason is basic aero-dynamics: "....... if air moves faster under an object than above lift will result. If air moves faster over than under the converse is true. Votecies created under an object by the positive preasure flowing over said object (i.e. a gurney flap or the back side of the lip on the uppermost part of a wing) can create sucction."

This is what I was looking at. Creating an undertray with a "lip" or a slight wing to counteract the effect of the dwnward facing radiator in the Fed Elans. I also want to avaiod this...

http://www.youtube.com/watch?v=3nLwMZgRNhw

Comprimised Mercedes aerodynamics. Who said refridgerators couldn't fly.

lotusgirlmarie wrote:Phil, Any pics? I'd love to see what the German Elan's look like on the underside.

I saw it at stoneleigh parts fare 2005, it's owned buy a guy on this forum called Albert.

Pics:
http://www.elanse.plus.com/lec/stoneleigh2005/index.htm

Discussed here (catch it before it dissapears from the forum);
http://www.lotuselancentral.com/forum/v ... c&start=20

Cheers,

Phil

lotusgirlmarie wrote:The other reason is basic aero-dynamics: "....... if air moves faster under an object than above lift will result. If air moves faster over than under the converse is true.

I believe you meant to say NEGATIVE lift will result?
Higher speed = lower pressure. You speed-up the airflow beneath the car to create negative lift [downforce]

lotusgirlmarie wrote:Votecies created under an object by the positive preasure flowing over said object (i.e. a gurney flap or the back side of the lip on the uppermost part of a wing) can create sucction."

The 'Gurney Flap' increases the speed / pressure differential between the upper and lower surfaces of the airfoil at the expense of increased drag and lower efficiency. The resulting vortices are not really desirable [in this instance] and for this reason many techniques (winglets, endplates, vertical fins, washout etc) are employed to minimise drag. There are some exceptions to this, notably 'delta-winged' aircraft such as Concorde; another example being Vortex Generators, which use the high energy vortices to break-up / energize stagnating boundary layer 'flow'.

lotusgirlmarie wrote:This is what I was looking at. Creating an undertray with a "lip" or a slight wing to counteract the effect of the dwnward facing radiator in the Fed Elans. I also want to avaiod this...

Radiators act like turning vanes for the airflow, and it's quite possible the downward angled Fed' radiator disrupts airflow more than the European installation? - The side-exit F1 radiators' outflow would actually deflect the slipstream, effectively making the cars' body wider, and for this reason blanking plates were used in qualifying and whenever possible to dramatically reduce drag. No recent F1 car designs have side exiting radiators... So, a minimal baffle directly below the radiator might do something??? But the air flowing through the upper part of the radiator is probably too far off the deck to affect anything???

Something you may want to check first is, what the airflow is doing through your hood vent as speed increases? Usually there is a high-pressure 'bubble' at the hood/winshield junction [good place for cabin intake vents] and we try to achieve a low pressure beneath the car; maybe your hood vent is connecting these two regions

Simple wool tufts should give some indication what's going on there

The wing aerodynamics (principles of lift) should be handled at the back of the car, if you raise the leading edge you reduce lift but this is a car not an aircraft so you will increase the pressure under the front as it hits the ground.

The under tray stops the air dropping town the front of the car, this stops the build up of pressure at the front which would destabilise and may cause lift.

Vortex is created at the edge or wing tip where air spills off the side loops back under and spins. The vertical tips keep the air flowing in the desired direction over the wing/surface and reduce the vortex. This happens on most wings not just delta that’s why 'Westland' redesigned the AH64 wings when they started making them.

Concorde had huge vortexing and you could see it because it had so much air passing over the wings (too much!) at low altitude.

The shape of the car gives lift because the air pressure is lower on top, the vents should be a good balancer as the lower pressure draws air up through the rad and engine bay, instead of the air compressing under the car.

Cheers,

Phil

Edit: keep the bottom of the car as flat as possible

Wow, this is turning into a really interesting discussion.

While I don't claim to be any sort of aerodynamic authority, I have spent countless hours in wind tunnels developing a broad range of road and race vehicles.

I would agree entirely with Brian's comments but would further add a couple of notes of caution.

One thing that I have found is that it is surprisingly difficult to make a generic aerodynamic device work effectively. Apparently similar body shapes can have quite different flow regimes. What works on one vehicle may have very different results on another. For sure, broad assumptions can be made, but when it comes to detail design of specific devices, more often than not you will find that it either has little effect or results in something quite unexpected.

Underbody aerodynamics (ground effect) can produce startlingly good results when properly sorted, however, this tends to be very sensitive to changes in ride height and pitch angle. Road cars have relatively soft springing and consequently large suspension travel. The attitude changes considerably dependant on when the vehicle is braking/accelerating, driving over a crest/compression or laden/unladen. Any of these effects could be enough to create transient flow over the underbody, making the response unstable and therefore unpredictable. This could produce a dangerous condition and is the reason most road car manufacturers leave this area well alone.

I wouldn’t want to spoil the party (I’m all for aero development), but I would suggest that when experimenting with aerodynamics, you proceed with caution.

Kuching wrote:Wow, this is turning into a really interesting discussion.

While I don't claim to be any sort of aerodynamic authority, I have spent countless hours in wind tunnels developing a broad range of road and race vehicles.

I wouldn’t want to spoil the party (I’m all for aero development), but I would suggest that when experimenting with aerodynamics, you proceed with caution.

Kuchingers has tons of experience with open and, closed wheel cars, whereas my experience is pretty much confined to open-wheel [F1] and aircraft work, but we both have a 'reasonable grasp' on how these things work

Here's a selection of fairly typical surface pressure plots - the red bits are regions of higher pressure

Kuching wrote:I wouldn’t want to spoil the party (I’m all for aero development), but I would suggest that when experimenting with aerodynamics, you proceed with caution.

I agree! It's all theory until you test! and I'm just coming from a theoretical point of view talking generally and reading intently!

These kind of bodyshell developments are generally for track use, which is of course a relatively controlled environment compared to the road. Lowering my road car would render it useless on our roads!

On the bottom of F1's models (I'm guessing it's a CAD Geometry model) you can see the creation of a vortex it would be great to see this information for the Elan with and without the German wing tips!

Cheers,

Phil

Racecar Engineering Magazine did an interesting series about windtunnel testing a Honda Touring Car. I seem to recall this had a similar 'winglet' type feature on the front spoiler/splitter, and I 'think' it worked most effectively when they closed the end of the channel in front of the tyre - kind of opposite of what you might expect
I recall from my days of aero testing, you fit some really trick elaborate piece of kit to the car (possibly inspired by a competitors ) and it would make zero difference, or adversly affect performance greatly Conversly, the application on an aluminium tape 'fillet' could have enormous benefit That's why Teams spend huge amounts of dosh on wind tunnels and CFD analysis - all interesting stuff

Maybe once I get the lightweight chassis project going, I'll see about getting it into the Mira tunnel.

Kuching wrote:Maybe once I get the lightweight chassis project going, I'll see about getting it into the Mira tunnel.

Sounds like a great idea! any idea how much it would cost?

As much as I find myself day-dreaming the same 'ultimate Elan', I always come back to the same conclusion - that it would no longer be an Elan You might as well take a race car and fit an Elan-style body to it

A change of engine seems 'aceptable' (a nice all-aluminium one - V8 Hayabusa ) to me, and replacing some of the production parts with custom made racing components for track use seems logical, maybe junk the windshield assembly and go for a M200-inspired look?...



Ooops...wandered off topic

Look forward to seeing what you're able to create next LGM

Fascinating posts!
Many years ago (when I was just a lad!) I fitted a very deep front spoiler to an MGB GT which I had trouble keeping on the road at now illegal speeds. It would not go over today's anti-speed humps and even scraped a few cats-eyes but made a noticeable difference at speeds as low as 55mph. The M100 already has a front spoiler with a small sacrificial rubber lip. I wonder what would be the effect of taking that down to a suicidal height?

Fascinating posts!
Many years ago (when I was just a lad!) I fitted a very deep front spoiler to an MGB GT which I had trouble keeping on the road at now illegal speeds. It would not go over today's anti-speed humps and even scraped a few cats-eyes but made a noticeable difference at speeds as low as 55mph. The M100 already has a front spoiler with a small sacrificial rubber lip. I wonder what would be the effect of taking that down to a suicidal height?

gtm100 wrote:Fascinating posts!
Many years ago (when I was just a lad!) I fitted a very deep front spoiler to an MGB GT which I had trouble keeping on the road at now illegal speeds. It would not go over today's anti-speed humps and even scraped a few cats-eyes but made a noticeable difference at speeds as low as 55mph. The M100 already has a front spoiler with a small sacrificial rubber lip. I wonder what would be the effect of taking that down to a suicidal height?

This idea is the current trend on the WRC cars. The air recirculating behind the lip reduces the pressure acting on the surface above it. However, it needs a reasonable flow of air under the vehicle to energise the recirculation. If you were to lower the lip too far it would block off the flow and stop this effect working.

F1 LOTUS wrote:As much as I find myself day-dreaming the same 'ultimate Elan', I always come back to the same conclusion - that it would no longer be an Elan You might as well take a race car and fit an Elan-style body to it

A moot point and maybe a topic for a whole new thread. Should our cars be preserved as Lotus intended them or is it valid to develop them to the point they lose their origins.

I guess its in my nature to always want to create something new and different. I suspect that Colin Chapman would have felt similarly.

But this is a clear case of thread hijacking so I'll hand it back to LGM