stand in miniature esprit almost finished

[Kimbers34]

Teigan you know who I am and that is hardly a rough model it's a proper wind tunnel test model. I will personally speak to him who knows all and find out for you what was and wasn't done. If I was wrong I'll be honest and eat humble pie.

If you are wrong I expect the same from you, but this will be a first I think!

[green_meanie]

Kimbers,

Don't rise to it mate !
Teigan is a TIT

You know it!
I know it!
The forums (note plural) he's been banned from know it!
Most of this forum know it!
and probably on some deep down level, (talking deep deep down) he knows it!!!!!

We all know the "wedge" as it is probably isn't the most aerodynamic shape known to man, and I'm sure that all the different transoms, spoilers and bits and bobs all have an effect one way or another but, what's he (TIT as he shall be known hence forth) going to gain from all this?

1 MPG better fuel consumption!
5 MPH better top speed!
the ability to go round a corner 2 MPH quicker!

oooooohhhhh! score...............

I say, LOVE the car for what it is,
A piece of motoring history.
A piece of motoring art.

If he can't do either of those then he should sell it and give us all a break from his constant whining.

Those in agreement say "Aye"

[GKP]

Aye.

[big-si]

whats the name of this local airframe tunnel facility please tiegan, theres a few questions i would like to ask them reguarding the facility in an non flowed cfm state , i would also like to know the ratio of air desnsity per ci over a linear or transverse surface there. amongst other things.

[teigan]

hey simon. it's a teaching facility in california. you can only get miniatures in there. up to about 1/16 scale for cars. i'll have to check on the max CFM, but the machines take 120psi at the regulator. i know it pulls over mach 1 at 1/24 scale. do you have a model you wanted to test?

[green_meanie]

To quote Teigans first post on this subject
"so i made a miniature esprit to stick in a real wind tunnel at a local airframe technology center."

and now it's

"it's a teaching facility in california. you can only get miniatures in there. up to about 1/16 scale for cars."

so it's not a "real" wind tunnel but a few carpet roll inners stuck together with a desk fan at one end.

Teigan, please, please show us pictures of this amazing facility that can produce real world results from MAX 1/16 miniatures, results that you will ultimately produce parts for your car to improve it's handling.

You really are in cloud cuckoo land aren't you !

[teigan]

so according to you, wind tunnels for miniatures aren't real? the reason for miniatures is to avoid building something full size until proven. everyone works in miniature. besides, the title of this thread reads "minature esprit". you have a serious reading comprehension problem. poor you.

[green_meanie]

Teigan, Teigan, Teigan!

Wind tunnels for miniatures.......... really, do they exist, well slap me with a wet kipper.

In case you didn't know there's miniatures and then there's miniatures.
1/16 scale is a ridiculous size to get real world results. In your case the Esprit "model" can be no larger than about 120mm wide if that's the largest that can fit then this really is a miniature wind tunnel. If they're testing airframes in this thing then I don't want to fly in anything they've looked at.

To quote some aerodynamicists

Scale Effects

Very seldom the models tested in a wind tunnel are in true size. Most likely they are scaled. Models on scale are hard to build and generally very expensive (just think of the surface roughness, tolerances, small details, etc.) To simulate the real conditions the aerodynamicist must keep the dimensionless parameters constant.

For example, a model 1:4 must be tested at four times the real speed. Hence the smaller the model, the higher the speed in the test section, the other parameters being constant


I'd still like to see photos of this tiny tiny welded chassis, all the body panels that you've made for your car that you've mentioned in other threads, and other "improvements" that you've made to your Esprit. If your not talking out your ar5e show us, and we'll probably stop baiting.

[green_meanie]

Just to add this is from MIRA (Motor Industry Research Association)

Model Scale Aerodynamic Wind Tunnel
Typical Model Scales
Model testing can be undertaken with a wide variety of scale model types including clay, milled foam, fibre glass or a combination of each. The easy at which these can be altered allows for flexibility in product design and styling. The following is a guideline for typical model sizes used in the wind tunnel:
- 40% scale for single-seat racing cars
- 3/8 scale for GT cars and large passenger cars
- 1/3 scale for small to medium -size passenger cars, 4x4s, MPVs and light vans
- 1/8 scale for trucks and buses
- 1/15 scale for rail vehicles
- Maximum model weight: 50kg

Teigan
Still think you're going to improve the handling of your car with your tests?

Edited by green_meanie on Sunday 11th February 11:09

[teigan]

green_meanie said:

Teigan, Teigan, Teigan!


Scale Effects



For example, a model 1:4 must be tested at four times the real speed. Hence the smaller the model, the higher the speed in the test section, the other parameters being constant

so you can't do basic arithmetic either? a model at 1/4th the size is already at 4 times real speed with the same wind velocity. if you want actual speed you slow down the wind by 4. get some concept of scale.

judging from the way you've blown an internet discussion way out of proportion, it'll be a long struggle.
i hope you spend more time trolling the inter-net for facts and figures because it amuses me to see how much personal time i can make you waste with no effort on my part.

[green_meanie]

Teigan

Just shows how much you know!

The bold bit of my post was a direct copy and paste of details from a web site called
ADVANCED TOPICS IN AERODYNAMICS.

here's the URL www.aerodyn.org
which is linked to by
http://formula1.about.com/od/technolo
just click on the wind tunnel link

So.....

1. Not my maths.
2. I think most people agree they're more likely correct.
3. You're in no way making me waste time. I'm having fun with this baiting game, took about 5 mins to find the info.
4. Give it up, you're wrong.

P.S.
Still want to see pictures.

[teigan]

you are so unsure of your own knowledge that you have to flash the names of supposed authorities to boost your claims. too bad you don't comprehend what you are quoting and take other people's writings out of context. for example, you take suggested scales for wind tunnel models to be scientific law. given we can computer mill models accurate to 1/1000th " smooth, those guidelines do not apply today. furthermore, the shapes of wave phenomenon seen in a wind tunnel are scale independent. you get the same interference patterns to scale whether your model is 1/8th or 1/16th. some single digit multiplication to struggle with again: poor you.

[gixxer]

I think Mr.-Meanie has you on that one teigen.
The company I work for has a transonic wind tunnel south of Seattle, and since I was in a meeting with the guy in charge of the tunnel models, they let me watch a test. If I recall correctly they were testing a model of the 747 LCF in what was no bigger than 1/20 scale. The true air speeds in the tunnel were in excess of 650 MPH (hence "transonic". It took about 5 minutes for the air to slow down enough so you could open the door to the test cell after the test. The test cell was also air conditioned to stay at 100*F.
Of interest, the model also sprouted vortex generators on it that the the real airplane doesn't have, probably due to scale effects. It was also made mostly of stainless steel.

[green_meanie]

Teigan

You keep saying poor me, as if I'm the one with some sort of problem, psycologists have a word for that.
I never professed to be an expert on wind tunnels.
I never professed to be an expert on wind tunnel testing.
I'm not an expert model maker.

I just pointed out to you that.
Again you don't know what you're talking about, and that it doesn't take much to do a little research to find out that your model Esprit is going to be next to useless in testing aerodynamic properties, and that all you'll end up doing is ruining an otherwise well balanced car.

[quiksilver]

The idea of quoting references is to provide a basis of a point of view or to back what you're saying up with some credability.

Greenie is right I'm affriad...

Scale has a HUGE effect on wind tunnel reading effectivness, and where possible the scale needs to be as close to 1:1 as possible. The Elise tested by Lotus was about 1/4th scale. It was tested at MIRA and used a rolling 'road' underneath it to also simulate the air disturbance under the car which is very important.

Apart from wind readings you also need weight transducers measuring lift, downforce and yaw on the design to see the effects on the model.

As correctly pointed out when you scale down you have to speed up the air flow to simulate a scale air pressure, effective drag, scale lift and downforce to name but a few of hundreds of factors affecting a wind tunel model. Subsonic aircraft are commonly tested in hypersonic wind tunnels to simulate their scale effects.

If you divided by the scale factor :
Think of it trying to simulate a car at 80mph - using a 1/4th scale model, the wind speed would be car 20mph.
How much drag, lift and downforce would that generate on your model - bugger all is the answer !
You'll get next to nothing also at 1:1 air speed becuase of the size of the model and the air pressure, the air simply takes the easy route around it - yes you will get some note worthy readings but nothing that would equip you to re-design the aerodynamics of the car without increasing the forces inversly to the scale of the model.

Also as stated the model has to be extremely detailed which is why scales are built up as well to factor those in.


This is : http://en.wikipedia.org/wiki/Reynolds
We did this in thermo/fluid dynamics at college.

You're going through all this to make a lower engine tray ?
A flat piece of aluminium and a few fins should do it...

Edited by quiksilver on Wednesday 14th February 00:44

[big-si]

one of the other big problems of trying to simulate a wind tunnel at miniature levels is the fact that air density per-c/i-2" is no longer calculable as the fluid dynamics of the air and reflective nature of dispersion over turbulence means that areas of pressure can be cancelled out. to gain a true flow of air flow, fluid dynamics and linear through-flow of body to air ratios you would need to make sure the distances of the walls of the tunnels are a certain distance from the model or 1:1 version of the object. this then allows the air flow over any surface to be of a non interrupted nature, the reflective air flow has nothing to deflect of within the immediate area, this is why most wind tunnels are of the size they are, even a true flow dynamicist would not use a scale tunnel as the results would not allow a true reading within tolerable parameters, you also have not factored in vibration and movement from this tunnel you describe, which is why tunnels are of a concrete design to factor out structural vibration and movement, also there is the operating resonance of the tunnel to consider

The whole point of a large scale wind tunnel is to factor out reflective airflow and dissipation of turbulent areas caused by this and to allow a greater non interrupted airflow. the internal dimension of the tunnel in relation to the root flow of air channelled through it must be held in relation to the model and its surfaces, it isn't as simple as just sticking a non certified scale model in a possibly non calibrated tunnel and expect the findings to be right.

it is scientific fact that as soon as you break these parameters any conclusions are no longer scientifically sound.

I'm not being condescending or patronising in any way tiegan and I'm not jumping down your throat so no need for any form of backlash answer OK .

but these are factors which do render the tunnel you used useless.

if you can find a tunnel that allows non interference fluid dynamics and airflow then the results will be a lot different i for one would be interested in the results you find.

it is widely known that under car air flow guidance and ducting greatly increase a vehicles handling and road tolerances, the basis of formula1 racing body internals revolves around an inverse aerofoil system and ducted flow dynamics.

si

Edited by big-si on Wednesday 14th February 13:31

Edited by big-si on Wednesday 14th February 14:03

[teigan]

hey simon. the wind tunnel was formerly used by douglas aircraft to design intercontinental ballistic missles. there is plenty of room to avoid reflected air. you'll have a meter or more clearance around your model. the air is circulated by impellor under pressure, and there is no aparent vibration. standing wave patterns will be the plenty accurate at 1/16th, unless you're playing with intentional roughness to manipulate laminar flow. in those cases, it's better to test in a water tank anyhow. send me your model if it'll fit. best of all, there's no cost.

[teigan]

there is no rolling road at the facility. however, the table is set up with dial indicators on up to 5 axis. there is an unidentified delta wing aircraft i've played with in there, and at anything more than scale airspeed, it is impossible to observe how and from what sources the turbulence develops. i assure you that your example of a 1/4th scale model hit with 20mph airspeed will exhibit the same flow dynamic behaviour as a full size model at 80mph. you don't need to search on the internet to understand natural laws. scale model RC aircraft would not fly if your claims were true, because the aerodynamics of the planes they were miniaturized from would not apply. you can prove to yourslef that is not the case. before making the final product, you must factor in gravity and molecule size, but the differences are minor and predictable.

last year i made a semi flat carbon fiber and kevlar undertray. it was missing and i needed an immediate replacement part. what i am designing now will a have triple curvature reverse airfoil. it will also make the side sill intakes on my car functional in cooling the inboard brakes.

do you have a link or photo handy of the original lotus undertray? i've yet to see one. everyone seems to leave the mechanic's shop without it, and never know it has gone missing.

quiksilver said:

The idea of quoting references is to provide a basis of a point of view or to back what you're saying up with some credability.

Greenie is right I'm affriad...
.......

If you divided by the scale factor :
Think of it trying to simulate a car at 80mph - using a 1/4th scale model, the wind speed would be car 20mph.
How much drag, lift and downforce would that generate on your model - bugger all is the answer !
You'll get next to nothing also at 1:1 air speed becuase of the size of the model and the air pressure, the air simply takes the easy route around it - yes you will get some note worthy readings but nothing that would equip you to re-design the aerodynamics of the car without increasing the forces inversly to the scale of the model.

Also as stated the model has to be extremely detailed which is why scales are built up as well to factor those in.


This is : http://en.wikipedia.org/wiki/Reynolds
We did this in thermo/fluid dynamics at college.

You're going through all this to make a lower engine tray ?
A flat piece of aluminium and a few fins should do it...

Edited by quiksilver on Wednesday 14th February 00:44

[quiksilver]

I'll agree you'll see the airflow at low speeds, but what you won't get is the effect to scale, it simply doesn't work.

Glad you bought the scale r/c aircraft issue up.
Models are vastly different than miniture versions of the real thing.

My Spitfire I flew was 1/8th scale and weighed 46 times less than it's scale equivalent (8kg as opposed to 370kg)
It could fly faster than it's scale speed but was way way down on fuel capacity. So the shape was the same but there the similarities end.

So take that model as it is, but make it it's scale weight of 370kg....how fast do you think the air flow over the scale wing will need to be to generate enough lift if at 8KG it was about 20mph. Even if it was linear (which it isnt) you're looking at 900mph +
In reality it's WAY more than this.

Very few things scale in a linear fassion, for instance to go twice as fast you need about 4 times the power.


If you stuck this in a wind tunnel, yes you can see how the air flows over it but in order to see how the air affects the object as fasr as drag force and lift are concerned you'd need a very fast gust of wind.
This is the same on the car, for certain things seeing the air flow is fine but if you want to simulate re-designing the car for aerodynamics you'll need a bigger model or a faster tunnel to replicate the results.

I dont have any undertray pictures although if memory serves me right they're not much as most of the back underside is open to cool the gearbox ?

Edited by quiksilver on Sunday 18th February 01:48

[Kimbers34]

teigan said:

wrong about what? i already stated that any wind tunnel tests done by lotus were for photo opportunities only. showing me a crude model is hardly the same as providing recreatable test data.

Teigan,

The Lotus Esprit WAS tested in the wind tunnel on a 1/4 scale model. I can assure you this is correct as it came directly from the Engineering Director of the Elite, Eclat and Esprit projects i.e me. In fact huge amounts of time and development were spent tuning the airflow management at MIRA. In fact the Elite has a Cd of 0.3 without wing mirrors and a static road tunnel. The Esprit wasn't at that level but for it's day (design in 72) it was good.

For your information Lotus was driven by F1 racing technology practices at the time, (e.g low mass, low COG, careful management of COP, etc) aerodynamics and high speed stability was a key part of all our designs with Colin and Myself, even during the Elan and Europa period.

Mike Kimberley.

Edited by Kimbers34 on Sunday 18th February 18:33