55ant
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| posted on 23/10/09 at 12:23 PM |
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aerodynamics.....
The 7 as we know it is often described as having the aerodynamics of a brick, i cant see why such a car hasnt had this problem resolved? the car in
its rough guise has been around for more than 40 years and always owned by 'enthusiasts' of going faster, so why has this been left so
untouched?
after looking around there are loads of long threads on this site discussing the advantages of diffusers, spoilers, downforce, lift etc, just do a
search on this site alone there is a good few hours of reading! also the wiki page states that the 7 has the highest drag co-efficiant of any
production car!
''In general, cars with non-optimized aerodynamics tend to be free of adverse aerodynamic effects on handling, but the front wheel arches,
of all but the Series I, cause lift at high speeds. Like the good straight line performance, the car's nimble handling is limited in speed
range. It can be argued that this is not usually important in a car intended for public roads.
While the car's frontal area is small, the Lotus Seven has the highest drag coefficient of any known production car--ranging from 0.65 to 0.75,
depending on bodywork. The introduction of the Series IV Seven improved the car's Cd.''
wiki site
wiki also states that wolverine drove one? not sure how true this is?
Anyway, there have been some 'specials' that have attemted to solve the issue,
but this isnt exactly what im after, its a bit too much! what im asking really is not some crazy fibreglass kit, or for some wise fury owner to chirp
in! but is there any benefit to be had from making small changes, such as flat bottom throughout, small head lights, diffuser (simple design, shed
egineering, just a 7 degree angle etc,) venting radiator air out through the nose cone etc? and is it all worth is in terms of weight and/or the cost
v's spent on power?
Diffuser design doesnt look easy!
the technicalities of aerodynamics start to get comlicated when making your own stuff, but when working with such a simple shape, can you make it much
worse?
away from cars, now cycling and building TT bikes
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balidey
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| posted on 23/10/09 at 12:38 PM |
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Kind of reminds me of something I read a while ago....
If you get a brick, round off the corners, its still got the aerodynamics of a brick. 
So, why take an un-aerodynamic shape and try and make it aerodynamic? Surely it would be better to do something else completely, ie fit a 23 style
body
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Hammerhead
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| posted on 23/10/09 at 12:39 PM |
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caterham did this
http://www.carpages.co.uk/caterham/caterham-seven-27-07-06.asp
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StevieB
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| posted on 23/10/09 at 12:41 PM |
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You could easily make it worse, and flat bottoming a car doesn't always make it better
like this
I suppose you could always try this method as a means of trialling small
changes to see which is worth pusuing the most.
I don't know how you would trial a flat bottom/diffuser installation quite so easily - maybe mounting a bullet cam and filming what happens to
the bits of wool under the car?
I did once see an episode of Mythbusters where the trialled aero mods to a model pick up truck by flowing water over the model and chucking a handful
of oats in the water so the could see the flow easily. Probably not all that scientific, but there again you're not looking to build something
an F1 Aerodynamacist would build...
ETA - I agree re. the Type 23 comments. Chapman wouldn;t have ever put a heavy full body on one of his cars if it didn't add performance...
[Edited on 23/10/09 by StevieB]
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Rob Bartley
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| posted on 23/10/09 at 12:44 PM |
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That Caterham just looks awful though! 
Rob Palin may be able to shed some light on this subject as it's his job..........Rob.........u there?
I WILL get out again!!
I have a little bit......need more......
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speedyxjs
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| posted on 23/10/09 at 12:45 PM |
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This is the main reason i am trying to design a new 'enclosed' front.
How long can i resist the temptation to drop a V8 in?
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balidey
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| posted on 23/10/09 at 12:59 PM |
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OK, if you want some real input, my company last year commisioned a large vehicle design specialist to look into vehicle aerodynamics. it was a huge
study, we spent A LOT of money. It took FEA and aerodynamic specialists a long time to work out all the variables we were interested in.
I can't give out any real details of the study, but their results from FEA were then backed up by real prototype trials, and the real road
results very closely matched the predicted results.
Now what we noticed was that what we thought would give good results DID give good results, and what we thought would not, did not.
So, what I'm saying is, common sense approaches to aerodynamic design can give you the results you think without you having to invest thousands
of pounds or make dozens of scale models.
Yes, I realise that its possible to make the aerodynamics worse, but if you see a large front edge sticking up, common sense says to round it off or
remove it, and our results proved that. Same with teardrop shapes and NACA ducts. Stick to proven ideas, they do work.
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55ant
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| posted on 23/10/09 at 01:03 PM |
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hmm, im feeling a wind tunnel mock up and a model, hmmmmm.
away from cars, now cycling and building TT bikes
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Mr Whippy
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| posted on 23/10/09 at 01:09 PM |
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quote:
Originally posted by speedyxjs
This is the main reason i am trying to design a new 'enclosed' front.
yeah I can see you have a lack of power to contend with
Fame is when your old car is plastered all over the internet
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procomp
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| posted on 23/10/09 at 01:20 PM |
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Hi
What makes you think that there has never been any serious Aerodynamic work done on a seven. Caterham have done extensive work in the wind tunnel With
a certain forum member. All in all you can do a certain amount of modification and see a small benefit. But all that happens when you go as far as the
work carried out on the car pictured above is it goes slower. Already been proved 18 odd yeard ago.
 
westfield 7 with full areo kit and works renault v6 300 bhp
[/img]
Cheers Matt
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MikeRJ
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| posted on 23/10/09 at 01:31 PM |
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quote:
Originally posted by 55ant
The 7 as we know it is often described as having the aerodynamics of a brick, i cant see why such a car hasnt had this problem resolved?
Because then it wouldn't be a Seven would it? If you want the aerodynamics and the handling, then go for a Fury/Phoenix or similar enclosed
cars.
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David Jenkins
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| posted on 23/10/09 at 01:47 PM |
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quote:
Originally posted by MikeRJ
Because then it wouldn't be a Seven would it? If you want the aerodynamics and the handling, then go for a Fury/Phoenix or similar enclosed
cars.
Just what I was going to say! It's the classic story, like asking a yokel how to get to a place - "Well, oi wouldn't start from
'ere!"
If you want a slippery car, buy a slippery car kit.
On the other hand, if you're not interested in high speeds but do want it to stick to the road, then the wings and stuff start to mean
something.
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55ant
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| posted on 23/10/09 at 02:04 PM |
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quote:
If you want a slippery car, buy a slippery car kit.
are you saying you never have, or never will change anything on your car? im not saying i want a differant car, just like most people, im interestd in
making it better, be it in power, weight or in this case aerodynamis (downforce), if it was proven that £20 worth of diffuser made an increase in
downforce, then is it not worth doing?
away from cars, now cycling and building TT bikes
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thunderace
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| posted on 23/10/09 at 02:17 PM |
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hes bolted on a dutton back end to make it look cool
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ettore bugatti
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| posted on 23/10/09 at 02:20 PM |
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I think the main aero problem areas are:
Headlights
Front suspension
Lift
Donkervoort has in their latest cars some hints what to about these items.
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David Jenkins
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| posted on 23/10/09 at 02:27 PM |
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quote:
Originally posted by 55ant
are you saying you never have, or never will change anything on your car? im not saying i want a differant car, just like most people, im interestd in
making it better, be it in power, weight or in this case aerodynamis (downforce), if it was proven that £20 worth of diffuser made an increase in
downforce, then is it not worth doing?
What did I say at the end of my post?!
If you want better grip, etc...
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nick205
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| posted on 23/10/09 at 03:11 PM |
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IMHO the issue come sback to the fact that 7 type cars are not built as high speed machines. By high speed I mean 120+ mph.
The whole point (a la Chapman) was the weight or lack of.
A 7 to me is about rapid acceleration and good handling.
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Mr Whippy
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| posted on 23/10/09 at 03:16 PM |
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quote:
Originally posted by nick205
IMHO the issue come sback to the fact that 7 type cars are not built as high speed machines. By high speed I mean 120+ mph.
The whole point (a la Chapman) was the weight or lack of.
A 7 to me is about rapid acceleration and good handling.
Ditto, it’s a country road blaster not an motorway missile
Fame is when your old car is plastered all over the internet
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andylancaster3000
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| posted on 23/10/09 at 03:40 PM |
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And the rear wings (they tend to be very large, flat front bluff bodies)... and the cockpit cavity.... and a big full cage.... Endless really.
You're obviously not going to make the aero of a seven good by any means but when you're starting from something bad it's always
easier to make improvements.
I think there are certainly improvements to be gained from reducing lift at the front, using a tonneau cover over the bits of the cockpit area that
haven't got people in them, prevent air from disappearing into the parachute of a rear panel (being careful to allow an exit for heat that comes
down the tunnel and off the diff) etc etc
How much you gain I dunno, nice to try though isn't it
[Edited on 23/10/09 by andylancaster3000]
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Rod Ends
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 posted on 23/10/09 at 04:43 PM |
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Lotus 11 - the original aerodynamic 7
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madrallysport
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| posted on 23/10/09 at 05:13 PM |
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S2000 engined car from over here, super quick and at race meetings looks very stable -
link 1
Link 2
UNDERSTEER is when you hit the wall with the front of the car.
OVERSTEER is when you hit the wall with the rear of the car.
HORSEPOWER is how fast you hit the wall.
TORQUE is how far you take the wall with you.
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A1
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| posted on 23/10/09 at 05:49 PM |
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why not try making it better? i notice the front end lift at about 95, im going to sort it, likewise im going to try and improve downforce with a
diffuser. i recon that taking out the passenger air brake and covering it over would be a good way to start too.
also though, they arent really about doing 150, are they? more about getting to 100 as fast as possible, then doing it through all the bends too
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jacko
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| posted on 23/10/09 at 06:51 PM |
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Hi All
 
Westfield
I was looking at this car last week and it has a rear de-fuser will this help aerodynamics much or is it just for show on this type of car
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speedyxjs
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| posted on 23/10/09 at 07:58 PM |
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quote:
Originally posted by Mr Whippy
quote:
Originally posted by speedyxjs
This is the main reason i am trying to design a new 'enclosed' front.
yeah I can see you have a lack of power to contend with
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Rob Palin
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| posted on 23/10/09 at 08:05 PM |
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There's a lot that can be done to reduce the front lift of a 7 but it is hard to reduce the drag much without extensive modifications (like that
131mpg Caterham). The fundamental problem is that the car is the wrong way around: the back is way wider than the front. Simply put, air *really*
doesn't like this, hence the CD range of 0.65-0.75 (similar to an older HGV in terms of efficiency). Tidying up the front end with smaller
headlamps and inboard suspension etc just means that fresher air hits the back of the car and causes the drag there instead. Frustrating but true.
The biggest single change to front lift is to sort out the front wheelarches. Wrap them around the front face and avoid the 'parachute'
style, bearing in mind that the air flowing at them is angled sharply upwards because of the blockage fo the tyre. Next up is minimising drag
generation from windscreens and roll cages, since those forces multiplied by their hight from the ground means a big contribution to the pitching
moment.
There's actually no need to do anything to the back from a downforce point of view as the overall pitching moment of the car is very much
nose-up, meaning that there is already zero rear lift or often mild downforce there already. As you sort out the front this 'relaxes'
back to about neutral or a small amount of lift, but that's only after a lot of modification.
Getting a diffuser working on a 7 is very difficult, primarily due to all the exposure at the front and the consequent upstream disturbance to the
flow. You have to do a lot of work at the front to get it working properly, although if you can it is a very efficient device. It's all about
protecting the flow you want to 'work' so that it's not beaten-up beforehand.
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