Lotus 7/Locost Aero Rebody

[JackMcCornack]

Originally Posted by Christ

...the seating arrangement probably has the driver about as close to laying down as you can comfortably get...

Racer comfort is different from street comfort. I'm sure everyone concerned--including the drivers--was more interested in the records than in comfort.

One thing that's missing in all the promo pieces (that I've found) is pics with a driver inside, and all the driving videos are edited to obscure the driver. The car has 7/8 the frontal area of the standard Opel Speedster and it has all come out of the cockpit. After a couple of hours in the driver's seat going round and round a racetrack, a GT-40 would feel like a limo. But I want one anyway.

Christ wrote...

> I might be pissing in the wind here, but I thought you could get away with
> almost any size model as long as it was scaled properly and proportionate
> to the full-size chassis?

Pissing in the wind isn't too bad if you do it downwind. I've always wondered why that phrase is never qualified, e.g. "...into a quartering headwind."

Re the model size, my background (such as it is) is small aircraft design and all my testing has been full scale. I'm not going to have any measuring equipment, I'm going to be limited to tufts and maybe oils, I'm looking for how simple it can be and still keep flow attached back to the tail. I'm suspecting the front half will be fairly easy, but from the cockpit back will be challenging. If I can get most of the failures out of the way with quarter scale models, that would sure be a time saver.

PS--my car in the first post? It's 41 inches tall with 5" of ground clearance.

[lunarhighway]

the height of the normal speedster is 1117 mm / 44.0 in
it would seen the eco speedsters dome is much narrower than the original speedster, if the driver is shifted to the center seating comfort could be the same as on the original speedster at the expense of passenger confort wich as far as i know is not an issue on the eco speedster.

[Christ]

Originally Posted by JackMcCornack

Racer comfort is different from street comfort. I'm sure everyone concerned--including the drivers--was more interested in the records than in comfort.

One thing that's missing in all the promo pieces (that I've found) is pics with a driver inside, and all the driving videos are edited to obscure the driver. The car has 7/8 the frontal area of the standard Opel Speedster and it has all come out of the cockpit. After a couple of hours in the driver's seat going round and round a racetrack, a GT-40 would feel like a limo. But I want one anyway.

Christ wrote...

> I might be pissing in the wind here, but I thought you could get away with
> almost any size model as long as it was scaled properly and proportionate
> to the full-size chassis?

Pissing in the wind isn't too bad if you do it downwind. I've always wondered why that phrase is never qualified, e.g. "...into a quartering headwind."

Re the model size, my background (such as it is) is small aircraft design and all my testing has been full scale. I'm not going to have any measuring equipment, I'm going to be limited to tufts and maybe oils, I'm looking for how simple it can be and still keep flow attached back to the tail. I'm suspecting the front half will be fairly easy, but from the cockpit back will be challenging. If I can get most of the failures out of the way with quarter scale models, that would sure be a time saver.

PS--my car in the first post? It's 41 inches tall with 5" of ground clearance.

Normally, I'd want to be pissing from upwind, so that the result was a urine stream which went downwind. Though I assume that's what you meant.

Of course, the actual phrase is "Pissing into the wind", which suggests that one is doing the opposite of what's desirable, but I digress. (Quite often, actually.)

Unfortunately, I don't know enough about aero testing to really give an accurate answer that's anything more than a guess about whether a 1/4 model will give you a good estimate of Cd or not.

I can say, with great confidence, that if it were me, I'd make the 1/4 or 1/3 scale model and tweak it for the best design, then scale it up, hoping for the best. I can't imagine that even small intrusions to the flow stream (outside the boundary layer) will cause enough of an issue to really be an issue. Besides, your design doesn't appear to have too many things hanging out in the breeze, so to speak.

[jamesqf]

Originally Posted by JackMcCornack

For me, models are ridiculously easy to make. The Foam Ranger (my car sized 3 axis CNC low density foam router) was ridiculously hard to make--took me a few years--but now that I've got it I can make an accurate scale model in styrofoam the day after I'm done concocting the Rhino files.

A little aside: if you have this (I'm so jealous!), why can't you easily do almost any body shape as fiberglass over foam? I don't know the cost of materials, but if it works for experimental aircraft, why not cars? The more so as you'd basically be doing an aeroshell over a donor chassis, or tube frame with donor running gear?

[botsapper]

Just to add more enthusiasm (or maybe more confusion) for the project. I took your preliminary chassis dims. & 'Tank' themed models and quickly sketched some views. I made some tweaks on making front & trailing spats around the wheels. Added Acura Integra headlights & Vette rear lights. I know your plan to make a roadster w/ minimal windshield + tonneau cover, but I added a two-passenger teardrop canopy/capsule. Hope to see your project continue into reality.

[JackMcCornack]

from Christ:

>Normally, I'd want to be pissing from upwind, so that the result was a urine stream which went downwind.

Today it would be an icicle stream, but other than that, good assuming there! Downwind = from upwind. South = from the north, etc. I expect the attorneys will want that clarified in the published instructions, this being America and all.

> I can say, with great confidence, that if it were me, I'd make the 1/4 or 1/3 scale
> model and tweak it for the best design, then scale it up, hoping for the best.

Good enough. Then, with great confidence, that's what I'll do. 1/3 scale takes almost twice as long to carve as 1/4 scale (and uses more than twice the materials, but big deal--a 2' x 5' x 1' block of styrofoam, in 2x4x8 billets the stuff costs me about $1.50 per cubic foot) I'll maybe try a couple of quarter scale and move up from there.

from Jamesqf:

> A little aside: if you have this (I'm so jealous!), why can't you easily do almost any
> body shape as fiberglass over foam?

:-) I can! That's why I made it. But don't be too jealous, the time and money invested in it is more of each than I have in the car.

>I don't know the cost of materials, but if it works for experimental aircraft, why not
> cars?

No reason, I hope. If it turns out there's a reason, you'll soon see the Foam Ranger under "Tools, Misc." in Trade a Plane.

And now the biggie:

from botsapper:

> I took your preliminary chassis dims. & 'Tank' themed models and quickly sketched
> some views.

Holy smokes, botsapper, you quickly sketched those? Even if you've been mooching Ritalin off the school nurse and worked on it all night, that's incredible!

And darned right it'll continue into reality, and hopefully with your assistance. A PM is coming your way--want to trade art for foam shaped to your specs? Want to work on commission? Want my first born child? Heck, if you'll collaborate with me I'll give up the crude-yet-primitive concept and we can do something classy.

PS--Not quite as classy as that canopy, though, because A) It ain't legal anywhere in the States (windshields must be laminated glass) and B) The first one would cost about 15 grand.

[Christ]

Jack - Somewhere in the world, there is a company that will make safety glass to your specifications. You send them a series of hard cardboard templates and instructions on how to tape them all together so that the smooth surface is the shape/size you need, include a probably hefty check, and they send you back a rather oddly misshapen piece of laminated safety glass.

[samandw]

Man botsapper, I'm jealous. You've got some serious skilz there!

Christ, I was thinking about that too. Perhaps one could settle for a "close" design using plate glass ala the Dymaxion car? Or perhaps hack of a few junkyard windshields with a glass-cutter and piece them together so the curves all work together to give a nearly smooth shape?

http://www.washedashore.com/projects...dworld/e44.jpg

Wait, what about seeing if you can buy an Aptera windshield?

http://streetknowledge.files.wordpre...5/aptera_6.jpg

[Christ]

I wonder if it's just the windshield that has to be glass, though.

I've been told different ways on this, ranging from all glass must be glass, to being able to replace all but the windshield.

The most common answer is windshield and front passenger windows must be glass, all else doesn't matter. I've never gotten an official answer on it.

[JackMcCornack]

Originally Posted by Christ

Jack - Somewhere in the world, there is a company that will make safety glass to your specifications.

There's one in Ankara, but they want a polished steel male pattern included with the order...or send them the cardboard and they'll make the pattern for you. It is a whole heck of a lot of money and I think that the 15 grand for that canopy in plexi would turn into triple that in glass. And it would weigh, oh, 150 pounds I'd guess.

If anybody knows of a local (like this side of the Atlantic) equally inexpensive source, I might be tempted to do a curved windshield and conventional roof. botsapper has me thinking that a beautiful body could be attainable*, just not quite that beautiful. It all costs the same on the screen, but as a wise man once said, necessity is a mother.

This just in...sandmandw, Christ, only the windshield has to be (DOT approved laminate) safety glass, the other windows can be tempered and may be plastic in many cases. So botsapper's shape could be done, just not one piece...and I've never cared for the George Jetson lift-canopy-for-egress look anyway, except in concept cars.

*Which reminds me; I was a member of a weight loss group many years ago. I was the only guy in the group (weight loss hadn't entered our culture yet as a guy thing) and I got teased some. Anyway, one week for motivation we were supposed to look through magazines, cut out a photo of the body we wanted, and stick it on our refrigerators. I chose Cheryl Tiegs, which got me a mixed bag of grins and puzzled looks.