Making a more efficient, aerodynamic soapbox gravity race car

[freebeard]

Xist -- That's all I was saying. All criticism as constructive, just trying to move things along.

...and, good on you.

aerohead -- I'd wondered what the rules would say about head-first position. I've heard bicyclists go supine, but they have to pedal. Maybe prone?

One thing you lose with the more upright driving position is forward visibility. The Varna body is almost like taxiing a tail-dragger airplane.

Have we lost the OP?

[aerohead]

Originally Posted by freebeard

Xist -- That's all I was saying. All criticism as constructive, just trying to move things along.

...and, good on you.

aerohead -- I'd wondered what the rules would say about head-first position. I've heard bicyclists go supine, but they have to pedal. Maybe prone?

One thing you lose with the more upright driving position is forward visibility. The Varna body is almost like taxiing a tail-dragger airplane.

Have we lost the OP?

The supine position is used so far,but maybe not where Joan is competing

http://twwhlspls.com/wp-content/uplo...gravity_04.jpg

[orengomotors]

Originally Posted by aerohead

If you're going to do an exposed-wheel car,an 'automotive' application of the NACA 0015 won't have any remarkable benefit for you.
The center airfoil section in the table below is the lowest drag.It's right in the pressure/friction bucket.

It's like the section at the bottom here.Very good flow.

Just turn the section on it's side like Soapbox Derby cars have done,then treat the top of the body as a wingtip.
Enclosing the suspension system inside struts as the Edison-2 X-Prize winner has done would be great.
Also,the wheel fairings,just as Edison-2.

Thank you Aerohead! i will adapt this shape to the body!

[orengomotors]

Originally Posted by Xist

I did a quick search to see if anyone ever calculated the cD of a soapbox derby car. I just found this page, which talks about racers achieving 25-35 MPH.

Apparently, the United States does not have hills like Spain does!

well, the actual gravity racer record is hold by an American guy:

https://youtu.be/Q1ndyA0UW2w
https://youtu.be/olF1WM7TMLM

the record is 84.4 mph!!

[orengomotors]

Originally Posted by freebeard

Xist -- That's all I was saying. All criticism as constructive, just trying to move things along.

...and, good on you.

aerohead -- I'd wondered what the rules would say about head-first position. I've heard bicyclists go supine, but they have to pedal. Maybe prone?

One thing you lose with the more upright driving position is forward visibility. The Varna body is almost like taxiing a tail-dragger airplane.

Have we lost the OP?

Freebeard, i'm still here! learning a lot from all of you!

[Xist]

Orengo, it is great to hear more from you.

Darcane, can you tell us about your son's racer? Perhaps in a dedicated thread?

[orengomotors]

the actual dimensions of the soapbox:


-Aerohead, Something like that??:

[renault_megane_dci]

I love this thread so far !

Could you describe a typical race like how many bends and their variety so we could get a good idea of the compromise between speed and handling ( for instance a narrower rear track should help speed through aero at the expense of stability) ?

I am already thinking spring brakes to get energy back after the braking

[aerohead]

Originally Posted by orengomotors

the actual dimensions of the soapbox:


-Aerohead, Something like that??:

You're gaining on it!
*Letting air go under the body is a no-no,so dropping the nose down to ground level would be a good move.Here's 'Kamm's' pumpkin seed body at top,notice how he did the nose

For the rear underside,for lowest drag,about a 2.5-degree up-slope angle has been found to be best.Here's Jaray's pumpkin seed of 1922.Really good pressure recovery (1st diffuser on Earth).

If you look above the wheel fairings on the Template you can see the 2.5-degree slope
[IMG]http://i1271.photobucket.com/albums/jj622/aerohead2
/Scan12.jpg[/IMG]

Getting the nose down and gentle diffuser will give you extra stability when at speed.

[freebeard]

I am already thinking spring brakes to get energy back after the braking

Regen/KERS. The big dogs use a flywheel.