Linner Strømlinet Vogn (Now with 3D model!)

[Sven7]

Originally Posted by NeilBlanchard

Two things that I would change a bit; that both related to the side profile that you sketched: the grill to hood transition needs to get a radius. (It looks like you dropped the stagnant point which is a good thing, I think; so it won't look like the sketch, but it would negate the sharp-ish corners on the top outsides of the grill.)

Originally Posted by Sven7

The hard edges will need to be filleted and whatnot. This is just blocking in the basic form.

This will have a large radius fillet. I am also planning on tapering the front end in plan view. It's like a block right now.

Yes, the stagnation point is lower

The windshield needs a bit of a "vertical" curve to blend it with the roof. This would bring it closer to the sketch, I think. You have a lot of "horizontal" curve in it now, which is fine, though this shrinks the interior volume, and could allow for the front fenders to sweep in at the front a bit more?

I have to admit the sketch was "cheated" and unrealistic.

Due to the nature of glass (and the extreme plan view curvature) I believe it is impractical to put a compound curve on the windshield. It is done on side windows because the curves are very subtle. Well, that's what my all car design professors tell me. I will be moving the A Pillars forward and the leading edge of the roof will get a radius. Still looking for alternative solutions or suggestions to get the air to behave nicely over that area.



I don't know what "Cp" is but it appears the airflow over at roof is quite low pressure, leading me to believe it's not too big of an issue. Thoughts?

Would there be an advantage to moving the windshield form forward more and making it a "one box" design like a dustbuster van?

If you leave the wheel track where it is, then you will have to integrate strakes and/or fairing and/or skirts into the model. I would narrow the rear track more than you have already; to let the fender curve you already have cover the rear wheels. And maybe the curve of the sides that are shown in the top/plan view be a little larger radius and to start the taper a little closer to the front.

I will be making strakes on the wheels. You make a good point though- the bodyside could be wider until after the wheels. I'll work on that.

I read somewhere on this site that air hits the rear wheels at like a 15* angle. Should the strakes be angled like that? Also, should the underbody have any sort of aero aids (a la splitter) if it's smooth anyway?





Thanks for the input It's always good to hear comments/criticisms because designers sometimes forget things lol.

PS- Does anyone have that airflow visualization thing with the blue and pink "air"? I'd love to throw a tuned up version of this into it.

[Arragonis]

Engines - IMHO - The Aygo KR-FE unit is very much an up to date 3cyl petrol, probably better for compactness and lightness than excellent torque / performance. In my Aygo the gearing is about 22 mph / 1000 (based on sat nav) in 5th, but you do feel the air resistance at anything over 60. With such a streamlined shape maybe a longer geared and higher torque setup would be better.

The equivalent Hyundai engine is the Kappa 3cyl from the i10, similar spec to the KR-FE but heavier, but does have a start stop and intelligent alternator system - reduced load on hills for example.

What is the target weight for this car ?

The FIAT Twin Air is good on paper, it has good performance for the size especially. Reports "from the field" though seem to suggest that even in it's low-boost "eco" mode it can't match the claimed economy figures and isn't as good as the 1.3 Multijet Diesel.

General: Twinair - Rubbish mpg with City Driving - The FIAT Forum

Fiat 500 Twin Air MPG - myth or con!

Twin Air MPG

General: TwinAir - real world consumption - The FIAT Forum

The 1.2tdi from the Lupo 3L / Polo Bluemotion may be a better bet if you want the best torque / economy compromise. Heavier than both and would need more space but a great engine all the same, and has the option of a 6speed.

There is the 1.2 TDI Insight as an example of course. And Vekke is aiming for 2l/100km from his.

[NeilBlanchard]

Low pressure means it is close(r) to separation?

The radii on the front will be good. I would look at the usefulness of the interior volume and see if the windshield plan curve works with it.

And the wheels on your model are in a very different situation than the wheels on the Ferrari. I think that the 15 degree angle is an outward flow, not inward? Which is good, and this is the reason why the back is tapered in.

Have you seen the 4 wheel designs by Jason Hill?




If the rear wheels are at least partially engaged, then the strakes do not have to be this large, but the basic idea would help, I think?

[Frank Lee]

One wonders why bother putting two wheels on the back when there is no load capacity back there; one would do perfectly well then.

[brucepick]

Originally Posted by Sven7

... Due to the nature of glass (and the extreme plan view curvature) I believe it is impractical to put a compound curve on the windshield. It is done on side windows because the curves are very subtle. Well, that's what my all car design professors tell me. ...

I assumed my Civic's front and rear glass were simple curves. Not so. There is a modest curvature that's perpendicular to the main wraparound curves.


Somewhere else there was a discussion of 3 wheels vs. 4. If I recall, that discussion came down in favor of 4 wheels for the additional safety/handling/traction benefits. If you want "Aunt Martha" to be willing and able to drive it like a car, four wheels help a lot.

The Aptera opted for 3 wheels, with a single (driven??) wheel in the rear. That configuration is already established as better handling than 1 front + 2 rear, but the Aptera had serious handling difficulties at the X-Prize competition and did not win its class.

[Sven7]

Looks like some good commentary up there. However I'll be away from the computer at a rally race this weekend and will try to reply when I get back on Sunday.

Later!

[basjoos]

3 wheel cars, especially lightweight ones, can have some problems when driven on snow covered roads since its wheel pattern doesn't fit the ruts left in the snow by 4 wheeled vehicles, especially after the snow has refrozen into hard icy snow and is wanting to push your wheels back into the pre-existing ruts. Traction could get interesting if the middle wheel is the driven wheel and is always having to cut a new rut in the snow.

[kach22i]

Originally Posted by NeilBlanchard

Have you seen the 4 wheel designs by Jason Hill?

Nice, these images are new to me there certainly seems to be some Aptera lineage (same designer).

Sven7, I'm sort of bummed out. Not that the changes make the car look conventional, just that the mission of changing it slightly and retaining it's original character seems lost now.

I've played with similar concepts for many years, I have yet to do what I'm about to suggest (at least on a 4 wheel car). Make a Styrofoam plug of what you consider the minimum passenger area (don't forget the wheels) and then add globs and globs of clay to it.

Remove as much of the clay as you can while forming the shell matching your first sketch. Three wheel cars take kindly to this method, the one 4-wheel car I started this method on kept having the windshield pushed back because it looked too much like a bubble car. However, the final result was pretty good, I took photos of each major change and step.

This style of developing a form is very sculpture and "hands-on", something I think your latest effort is lacking a little in.

Thank you for sharing your work, please keep going with it.

Below is car I drew around 1988, I too cheated a little, but did not really know the extent until I worked in clay on another car design years later.

George Kachadoorian, Architect PLLC


This 3-wheel rough study below I did about six years ago may have similar curves up front. However the front wheels will need to be tucked way inboard to match up with what you are trying to do, or what I was trying to do in 1988.
Industrial Design pictures by kach22i - Photobucket


Check out those fender mounted rear view mirrors - snazzy!

Cheers, George/kach22i

[NeilBlanchard]

I think 4 wheel designs are far more stable, and they provide more interior room, too. The main choice then is to either taper the rear track, or do something like Jason Hill has done to let the air flow around the main chassis to flow in around the rear wheels.

This taper and flow are key to a low drag design.

[euromodder]

Originally Posted by Sven7

Having a nice discussion over engines and such. Anybody want to chime in about the 870cc FIAT Twin Air Turbo?

It's not easy to get near the brochure numbers with Fiat's Twin Air.
EM-er savefuel got it down to 3.72 L/100km - 63.2 mpg
Details: Fiat - 500 - TWINAIR - Spritmonitor.de

The next one is a lot less impressive @ 44.5 mpg:
Overview: Fiat - 500 - Spritmonitor.de


Unless you want to go really fast, it's likely overpowered.


If you want tight packaging, look at the new 1L VW 3 cyl. engine used in the VW up!
On CNG in the projected Blue Motion version, it's expected to deliver 75g CO2/km - 2.5kg CNG / 100km - that's lower than anything out there with an ICE.
CNG adds weight though and needs a lot of volume to get some decent range.

The Kia /Hyundai 1.1L diesel is newer and more efficient than the 1.2L VW TDi
In the Kia Rio - not exactly a small car - it's EU rated for 85 g CO2/km / 3.2 L/100km or 73.5mpg