stand in miniature esprit almost finished

[teigan]

i had a 3D computational model of the espritS3, left over from the navier stokes fluid simulations i did last year to diagnose the aerodynamics. those tests showed no consideration for car performance was involved in the body design. any wind tunnel tests done by lotus were for marketing photo opportunities only. it can be argued that computer wind tunnel simulations are imperfect, so i made a miniature esprit to stick in a real wind tunnel at a local airframe technology center. it still needs a chassis, powertrain, and wheels. when i get around to finishing it, i can prove once and for all that the esprits fare worse than most blocky sedans at high speeds because of a lack of basic understanding of flow dynamics on part of their engineers. this wastes fuel and adversely affects steering even at moderate speeds. here's a few snapshots of the miniature if anyone is curious:

http://pg.photos.yahoo.com/ph/i_teiga

[teigan]

i'd have thought a wedge was a great shape too, but not any random wedge is going to work. a lot of stochastic factors are involved which can cause turbulence and unintended lift. you also want a shape that that doesn't change resistance rapidly when rotated through a steering maneouver. sorry about the dark pictures. they were taken with a motorola V3 indoors. better photos at a later time then.

[teigan]

a simple machine like the esprit shouldn't cost a fortune to run. maybe you got cheated by dishonest mechanics who persuaded you into unnecessary repairs and upgrades. why vent your frustration on others who didn't fall into that trap? the wind tunnel miniature is going to help determine the exact shape of my lower engine tray. it'll henceforth be used each time i make a new part for the car. seems an efficient workflow strategy; and debunking the critics of my initial computer based simulation will be a bonus.

[teigan]

i would do that on a bet, but it would probably void the warranty. i took laser level measurements off the actual car, with an autoart toy for cross reference. in most cases, the toy was misleadingly wrong.

[teigan]

looks great. the biggest problem we have is the turbulence behind the car. if the tail section were a little longer, things would improve noticably. handling would improve too.

with regard to my mini project, i got a little carried away, and am in the middle of welding myself a tiny chassis. on hindsight i should have made it out of wood. i'll keep you posted. i think i can at least verify your undertray theories for you.

[teigan]

i didn't know the esprit began with a giant chair in place of wheels. lotus has come a long way since those early days.

[teigan]

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]

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?

[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.

[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.

[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.

[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

[teigan]

thanks mike. do you not agree though that my car from 1984 suffers aerodynamically from the kick tail at the back? i think a lotus employee confirmed years ago that the lip on top of the louvres was a last moment hack to stop air ever reaching the kicktail. i removed my louvres last year to take a mould, and i confirmed that at highway speeds, the front end gets lifted enough to make steering squirrely. colin would have agreed that an aft wing needs to be balanced with a small wing or canard up front. although the louvre lip solves the steering problem, it effectively cuts short the trailing edge of the car, which needs to be longer if anything.

[teigan]

danster72 said:

danster72 said:

Can I suggest you post a full apology to Mr Kimberley and to Lotus for claiming:

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.

and then just shut up and accept that you were wrong.

Is it my imagination, or have you gone awfully quiet in the past 24 hours, Teigan?

Looking forward to reading a nice polite apology, and then we can close this sorry little chapter...

unlike you, i come on this forum only as an aid to working on my vehicle. i have a life and couldn't care less what you and others happen to be saying about me. yes i disappear for days at a time. i wasn't here over valentine's day and i wasn't here past weekend which was a holiday. get a life. as for apologising to mike kimberly. he gave me a media blurb, and there was no useful or new information in his answer. as would be expected, i queried him a little further and more specifically since he was already here. i hope he was impressed by the sycophantic posturings of you and your internet friends. if you all had some actual skills, you wouldn't need to cowtow to people in an affort to get ahead.

GKP - "I used a toilet once after a lotus employee pooed in it. It was awesome"

[teigan]

i did read up before purchasing the car. however, what the esprit websites and the coffee table books say about the esprit turned out to be false. based on that information, i expected a no nonsense vehicle designed for high performance driving. i especially expected a solid suspension with quick responsive steering. turns out the car is as much a poseur as an entry level japanese car with the letters "GT" slapped on by the marketing department. so much about the car is just not functional, and the generally poor workmanship just makes it worse. i must admit i did buy a used '77 esprit as a teenager, and you could say i should have learned then what i know now. well i wasn't exactly a responsible person back then, and i hadn't driven enough cars to know what was good. i also must admit i blew 2 pistons showing off, and didn't have it long. a few dozen cars later, i now have a basis for comparison. i rate esprit performance far behind even the econobox fords i was issued as fleet cars. i've given up the idea of using my lotus as a weekend track car, but it'll still make an adequate grocery getter, and i've no plans to sell it. i'd sooner make it a lawn ornament than waste time demonstrating it to a line of gawkers. meanwhile, i'm refining all the rough edges, and it may someday be of acceptable quality despite lotus. this isn't the only car i've found to be overrated. i criticised the camaro and vette to no end. however, fellow owners didn't demand i sell the car when i pointed out the mechanical flaws. i guess the average lotus owner is more personally insecure. despite driving through rose colored asses, you subconciously suspect the shaking and squeaking does not a performance car make.

Mad Zero said:

Have to say I too am puzzled as to why you own an Esprit teigan - did you buy it before realising what you'd got yourself into? ..or maybe you'd had more modern sports cars prior to the Lotus? I ask because most (if not all) the Esprit's quirks actually add something for me. I've had the use of all sorts of sports/performance cars over the years and driven many miles in a Turbo Esprit - now that the time has come for me to buy my own car it HAS to be an Esprit due to it's sensational looks and racing heritage - sure it'll have it's faults, some of which will no doubt make me swear and cost me money but you don't seem to have a good word to say about the car, or the company that made it! I'm not offended by anything you've said/written incidentally because I'm not selling them but please enlighten me!

[teigan]

Mad Zero said:

teigan said:

i expected a no nonsense vehicle designed for high performance driving. i especially expected a solid suspension with quick responsive steering.

You should get the suspension and steering you want with the Esprit if not the performance you were expecting but I guess you've already ensured all is well with your example so I won't suggest getting someone to look at it for you!

I think SOME of the trouble with the performance issue is caused by the Esprit's styling, it looks so damned fast when it's stationary one's mind expects Formula 1 performance when you twist the key! I too had a Camero btw (yes, here in UK!) so I can imagine what you said about those! Over here we tend to see Cameros and Firebirds as equivelents to our Ford Capri i.e. not exactly a sports car!

Just a thought, have you thought about a different engine in your Esprit? Perhaps something a little more modern which would give you the power/weight ratio to put the smile back on your face?

Edited by Mad Zero on Sunday 25th February 10:57

[teigan]

[quote=toyroomJust a small fact I picked up once or twice. Scale model and toy cars intended for use as toys or ornaments are very rarely accurate. Due to the "impression" created by the huge difference in size, certain aspects of these objects are often very different in proportion to each other in order to look more realistic. I think it's a similar idea to the radiator fins of a Rolls Royce looking straight because they are actually slightly bent whilst they would look curved if they were, in reality, perfectly straight. For this reason, toy and ornamental cars are likely to be sufficiently innaccurate to be unsuitable for scientific research whilst still fulfilling their objective to entertain and give pleasure to their owner.

Edited by toyroom on Sunday 25th February 12:54

[/quote]

that makes a lot of sense. would have been nice though to have a true scale model available as well. have you seen the kyosho 1/64th scale esprit toys they gave away at japanese convenience stores? a friend bought me one off ebay. i've since bought 2 more in different colors.

[teigan]

Tuna said:

[quote=teigan]...You were wrong about wind tunnel tests being carried out, your own wind tunnel tests look pretty ropey and I'm amazed that you seriously thought a scale model toy should be accurate to the same dimensions as the full scale vehicle. It gives the overall impression that you really don't know what you're talking about.

to the contrary, the lotus voice talks of wind tunnel tests in 1972, more confirming my suspicions. my car is a 1984 and various plastic bits were added everywhere which would have required a whole new test. if lotus actually utilised the wind tunnel data to determine shape, then another series of tests would have been ordered. as i stated before, the only acceptable proof i am wrong, would be to provide the raw wind tunnel data, and evidence it was ever interpreted. releasing that raw data would also be of great social service to any and all wanting to improve their cars.