The 2-Part Aero-Body Concept

[kach22i]

Here is the concept, in two parts.

1. You start with four wheels, it is defined as a rectangular box once the wheels are enclosed. The front, nose or bow deflects the air mostly over the top.

2. The cabin greenhouse or canopy, known simply as the area above the wheel-wells can be closer to the idea aerodynamic shape; the teardrop.

1 + 2 = 3 seater in this case.

Back on 11/11/11, I posted in this forum a red pen sketch of this 2-body part concept, I forget the reason. That sketch is included in the "Inspiration Board" shown below.



As kids, my brother and I used to race our slot cars, he had a Jackie Stewart 1971 L&M Lola, I think I raced a Porsche 917 or Ford GT40. anyway, the blunt simple lines of the L&M car left some kind of impression on me, even though it was the ugly duckling of the bunch.

This concept has little to do with "pretty", and everything to do with "simple". Hopefully aerodynamic forms have their own sort of beauty.

I built a less than perfect study model to help get the feel for this concept car, it is real 3D. There are some differences between the sketch on grid paper and what I built. I like to change things on the fly and just go with the flow.



As you can see, it's not following the green template very well.



The Morelli shape is more forgiving, but I'm not sure that I'm using it right.

The glue is still drying on the model, and I have to sand down the balsa wood targa roof yet, but it is at a review point, or at least pour a glass of wine point.
Industrial Design - Transportation pictures by kach22i - Photobucket






Many more photos in my album:
Industrial Design - Transportation pictures by kach22i - Photobucket

Side headroom is a bit tight, and the rear passenger is just about sitting on the floor. I think there is some working room here, and problems can be smoothed out given more time and a better more accurate model.

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QUESTIONS: On a scale of comparable cars, where would this one fall?

What kind of Cd would you predict?

There is this product call Monopan which I would make this car out of (model is out of plastic poster board). I would fill the cavities with carbon foam, which would hold a charge (absorb energy upon impact too) and act as a giant capacitor in combination with batteries driving an electric motor at each wheel.

[Sven7]

I think you need to sell us more on each of your design decisions. What is the purpose of the car? Why ignore the template and avoid plan taper?

Who's your customer? Why would he/she buy it? Honestly I feel like I'm missing half the story on it... sell us on the concept, whatever that is!

[kach22i]

Originally Posted by Sven7

I think you need to sell us .........

Think less marketing, and more about forum.

The attraction of building a car in the same manner I would a hovercraft, with Monopan is an important part of this concept. It is just not as important at the model stage.

MonoPan :: The Future in Material Technology



Curving glass would not be so simple, but the windshield is just a slice of a cone in this design.

This would be a car for myself, screw what anybody else wants, I'm creating art here.

[Sven7]

Ok, so you're designing a kit car for yourself. So what does it matter what we think! :P

I guess I'd suggest more room for the passengers. Possibly look into lexan/polycarb for windows?

Bring that rear surface up to nearly match the template. It looks like you're trying to make a greenhouse that mixes the Ley T6 and GM EV1. I'd say concentrate on the body more than the greenhouse at this point. The air will see the thing as one form- not two- no matter how much thought you put into them. Think about cross-winds. How will that boxy body deal with them?

[ERTW]

Your "2 part body" is actually called a "composite body", invented by Jaray in the 1930s...but well done on your logic

you can basically add the drag on each separate basic shape to come up with a composite value. since the bottom is basically a brick - 0.40 - and the top is a tear drop - 0.080 - i'd say, just eyeballing proportions, that final Cd is 0.32, plus about 30 counts for wheels, and 20 counts for surface detailing...around 0.37 plus generous lift.

the wing isn't helping anything dynamically. it's too close to the body to add downforce, and downforce will just add drag. losing the wing will likely reduce drag.

i like the lotus evora greenhouse, and the way you dimpled the tiny helmets. the ridged body work will help guide streamlines...kinda like shark denticles (the new name for scales). radii are your friend. with a little streamlining, and watching the details, i'd say you could drop into the 0.2xx. you could do tuft testing on the model...If only you had a large quantity of string cut into 3" lengths. hth

[Sven7]

Remember if you want to aero test it you have to drive at many times the normal speed to make up for its small size.

1/1- 20mph
1/2- 40mph
1/4- 80mph
1/8- 160mph

I'm not sure what scale this car is but if you wanted to get accurate measurements you might need to either go to a wind tunnel or build a third or half scale model.

[kach22i]

Originally Posted by ERTW

Your "2 part body" is actually called a "composite body", invented by Jaray in the 1930s...

I did not know this, thanks I will look it up.

The front part of the bottom section I'd argue is not a brick at all, but the best shape to divert air over he top as 98% of cars and trucks do, but they do it in a less clean manner.

The blunt curve is very much like the green template building just enough pressure to insure adhesion of the air. One thing the real L&M Lola has over the slot car model is eased front corners. I can see myself taking an Xacto blade to the model and doing the same to my front corners.

The rear is not a brick either, minimal area for tail lights and bumper provided. I disagree about the rear wing being out of the airflow, but would have to wind tunnel it to be sure.

I read recently that air moving over the top of the vehicle should be prevented from spilling over to the sides where it will mix with that air-flow and cause turbulence. I did consider building a McLaren ridge (not sure of the correct term for this body rake) into this design but did not want to stray from the main concept. Funny thing is this car is a contemporary to the Lola, so maybe I'm stuck in the 1970's and trying to relive my childhood in some manner.

Tyler/Sven the scale is 2" = 1'-0"

If I build models any larger I will need a larger work area to work in. Right now my studio is turned into a storage area and filled with stuff from my old office. I built this in my living room, much to my wife's disappointment. I do clean up after myself, but the house is a mess for several days during a work frenzy.

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The material will require a jig to be set up so that everything is square, but no full sized clay body required to cast a mold, and then to hand lay fiberglass or other complex composite methods using foam.

I'm pretty sure I can heat the Monopan to bend it like I did the Coroplast, but I think I can also get the Monopan glass layer unresined, curve it over a buck/form and vacuum bag it into the final form.

Like I said, I used this same thinking (Monopan) in building a hovercraft model (Coroplast - five feet long). The hovercraft would be a 50 foot long patrol hovercraft and is very stealth looking because of the faceted surfaces.

[ERTW]

ok...the base is 1/2 brick, 1/2 streamlined. Cd 0.28 your rear end treatment is complex...so it's no longer a simple a + b.

i didn't say that the wing was out of the airflow. i said it wouldn't generate downforce. wings need to be at least 2 chord lengths (iirc) away from the body to work. imagine the low pressure below the wing, is the same low pressure above the body...they cancel each other out. imo at best it will add drag.

1970's thinking was that spoilers, dams and fences would "fix" aero problems. they're bandaid fixes. a radius on all the vertical surfaces that's >10% of the thickness (of the base) will do more for you than fences. can you put a fillet where the greenhouse meets the base? taper the nose and tail a little? i like the P4/5 nose/tail treatment.

thanks for the pic. i was actually thinking of raking the body a few degrees (like a wedge) to reduce lift. taper the rear of the body 13* (my research indicates this is optimal in your situation). it's all in the details.

[kach22i]

Originally Posted by ERTW

............. a radius on all the vertical surfaces that's >10% of the thickness (of the base) will do more for you than fences.

Great information, can you lead me to a white paper PDF in case I ever need to argue this point?

Beautiful red car in the attachment you made. This exercise I'm going through is almost the opposite in it's brutal and simplistic geometry.

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I did myself a disservice with the original overlays as they did not embrace the unique concept applied in this particular design. With a fresh set of eyes that a good nights sleep brings I offer up these new overlays, of the "canopy only". Gosh darn, the shoe does fit after all, don't it?

Industrial Design - Transportation pictures by kach22i - Photobucket



The glue is still drying on the targa roof, hope to do some grinding and sanding Tuesday evening.





I have thought about side winds while proceeding with this concept. My feelings were at the start, that the sides as drawn were 24 inches high. As built around 27 inches high, add 5 inch ground clearance to both dimensions for the above grade height.

Anyway, compare that broadside figure (height x length) to any other road car. Traditional near vertical side windows, stylized sculpting of the side body and accent trim do little to nothing to lessen the actual area the wind catches and can push on. I argue that this catchable wind load area is far less with my 2-part body concept. Mostly because the upper half is so optimized for three dimensional aerodynamics, but the lower half also represents less actual area than in most cars on the road today.

About half the cars on the road today are actually trucks, and trucks and or SUV's make my argument/case even more self evident.

RE:

Originally Posted by ERTW

............. and the way you dimpled the tiny helmets.

You are joking, right? I used old golf balls as helmets (+ Sharpie marker), cleaning them first was the hardest part.




I'm having a blast if you didn't notice.

[drmiller100]

mclaren mk6, circa 1969, complete with 3 seats.

Your car would be more aerodynamic if you ran it backwards.