Making a more efficient, aerodynamic soapbox gravity race car

[orengomotors]

Originally Posted by freebeard

That looks like a good effort. I like the 'ablative safety panels'. They could be block styrofoam with a vinyl wrap.

Your nose mimics the Atom. Current best practice in the off-road racing builds is a forward leaning A-shaped bumper similar to the VW Cal-look baby buggy bumper. Here's an example from a more modest random build thread on thesamba.com:



I think the idea is if you hit something it's only going to go down and to one side or the other. It could fit well with the style of nose you proposed.

formula as uses this forward leaning bumper very much:

[orengomotors]

Udapted version with wheels, track is 900mm:



https://drive.google.com/file/d/0B1c...ew?usp=sharing

[freebeard]

I see four areas to resolve—the nose, tail, cockpit and suspension. It looks like it will be as your examples minus the side pods.

You're set on the nose. Your examples have no boat tail at all, room for improvement there. Open or closed cockpit? Will you reuse you current A-arm setup?

Exposed suspension parts and the roll bar will be a big part, maybe half as the body is optimized, of the total drag.

[orengomotors]

Originally Posted by freebeard

I see four areas to resolve—the nose, tail, cockpit and suspension. It looks like it will be as your examples minus the side pods.

You're set on the nose. Your examples have no boat tail at all, room for improvement there. Open or closed cockpit? Will you reuse you current A-arm setup?

Exposed suspension parts and the roll bar will be a big part, maybe half as the body is optimized, of the total drag.

The rules allow closed cockpit. i'm thinking to reuse my current A-arms but doing this:

https://youtu.be/qJZoqGHAIDE

but symmetric, to cover te A-arms, what do you think?

[orengomotors]

I have to finish the body shell before December 4 for a scholar project.
Now, i have acces to a laser cutting machine, so i can cut wood in the exact shape to make the molds using a .dxf file (autocad) or similar.

[aerohead]

Originally Posted by orengomotors

The rules allow closed cockpit. i'm thinking to reuse my current A-arms but doing this:

https://youtu.be/qJZoqGHAIDE

but symmetric, to cover te A-arms, what do you think?

I saw Danika Patrick's Indycar at the Texas Motor Speedway some years back.All the suspension components were streamlined this way.They also had MOON-type wheel covers on the inside.For an exposed-wheel (monoposto) type race car,it was about as 'clean' as one might expect.
From the following drag table you can see the benefit of the streamlining,as the tiny cylindrical rod has the same drag as the gigantic airfoil section

[freebeard]

All respect to aerohead but I'd follow Mair rather than Hucho for the A-arms, for less frontal area.



Wrap the front tube, flat between the tubes and a nice tapered trailing edge. The outer extent of the trailing edge will be limited by the wheel-and-tire swing in near-side turns but the trailing edge could be angled to increase the fineness ratio. The trailing arms would start to act like fences, breaking up vortexes down the side of the car.

Are the steering linkage and brake line above, below or between the upper and lower arm?

Here's the best open-wheel treatment I've seen:

[Imgur is running around with it's hair on fire, I'll edit in the Mariani Farms roadster later]

[aerohead]

Originally Posted by freebeard

All respect to aerohead but I'd follow Mair rather than Hucho for the A-arms, for less frontal area.



Wrap the front tube, flat between the tubes and a nice tapered trailing edge. The outer extent of the trailing edge will be limited by the wheel-and-tire swing in near-side turns but the trailing edge could be angled to increase the fineness ratio. The trailing arms would start to act like fences, breaking up vortexes down the side of the car.

Are the steering linkage and brake line above, below or between the upper and lower arm?

Here's the best open-wheel treatment I've seen:

[Imgur is running around with it's hair on fire, I'll edit in the Mariani Farms roadster later]

My comment would be that the Mair contour is for 3D flow about a cylindrical section,or half-body,while the flow between the wheels and body would require a 2D airfoil/strut section,like on aircraft landing gear.
From the table below,we find the drag minimum at the bottom of the curve's 'bucket',at a chord to thickness ratio of 3.92:1

It would fall in between section 4,and 5.
Technically,the section in the center of this following table would satisfy the drag minimum for the 2D flow.

I've done this to my driver's side mirror for a couple months now,and the flow is absolutely perfect coming off the struts,as far as I can tell from tufts.
I'd also use this profile for the plan-view body taper.Some land speed record cars have used it to good effect.

[freebeard]

Could you not take Section 5 and add a short cylindrical section to make up the length?

How would you apply this to the suspension members? There are an upper and lower pair of tubes. Would you wrap each tube separately, enclose each pair or have the upper and lower arms in the upper and lower surface of a single blister?

Imgur is back up; here's the Mariani Farms 34 Ford

[orengomotors]

Originally Posted by freebeard

How would you apply this to the suspension members? There are an upper and lower pair of tubes. Would you wrap each tube separately, enclose each pair or have the upper and lower arms in the upper and lower surface of a single blister?

i will do two separate blisters.