The aerodynamic test "buck"

[TEG]

Along with "the Mule (http://www.teslamotorsclub.com/showthread.php?t=723)" (a drivable pre-prototype), Tesla build a clay model (to refine the body styling), and an aerodynamic "Buck" to go through the wind tunnel.

These are pictures of "The Buck" at Tesla HQ:

http://farm1.static.flickr.com/155/393801228_c4436f89fa.jpg
http://farm1.static.flickr.com/170/397175385_6d99a6c67c.jpg
http://farm1.static.flickr.com/174/393766369_ca88cd2662.jpg

[Martin]

The black car in the background is not clay. It is a machined aerodynamic "buck" that was later used for some styling experiments. We still have that buck as a museum piece. We did build a clay model in the UK, and that model was indeed destroyed. Perhaps one day I will post pictures of its destruction :-)

[vfx]

"...clay model ...was indeed destroyed. Perhaps one day I will post pictures of its destruction."

Would those be sold as cancellation proofs?

[TEG]

The black car in the background is not clay. It is a machined aerodynamic "buck" that was later used for some styling experiments. We still have that buck as a museum piece. We did build a clay model in the UK, and that model was indeed destroyed. Perhaps one day I will post pictures of its destruction :-)

Thanks, Martin...

I updated the comment on the photo in this topic.

Your MPG talk slides (http://www.teslamotors.com/display_data/pressguild.swf) (page 62) do show a sledgehammer job on the (silver) clay model in Aug 2006.

So it must be the "buck" ("museum piece") that showed up at Burning Man?
http://farm2.static.flickr.com/1212/1332823601_80896a6338.jpg
http://farm2.static.flickr.com/1099/1378444402_5f95927f77.jpg
http://www.mrjoe.com/MrJoe/Creative_Greenius/Entries/2008/7/12_Plugging_Plug-Ins_Part_I__The_Greenius_Guide_to_EVs,_Hybrids_%26_Plug-In_Hybrids_That_Will_Rock_Your_World_files/01-lifeport-1207.jpg

[TEG]

Perhaps this was the 'buck' before it got painted?
http://www.teslamotors.com/display_data/aerodynamic1.jpg

[TEG]

http://photos-a.ak.facebook.com/photos-ak-sf2p/v190/204/27/18790602800/n18790602800_358984_7422.jpg
http://photos-j.ak.facebook.com/photos-ak-sf2p/v190/204/27/18790602800/n18790602800_358985_7639.jpg
http://photos-k.ak.facebook.com/photos-ak-sf2p/v190/204/27/18790602800/n18790602800_358986_7845.jpg

[doug]

http://www.teslamotors.com/display_data/aerodynamic2.jpg

[TEG]

From here (http://www.flickr.com/photos/steve_simms/643171724/in/photostream/): "The clay model... This was shipped form Norway after the wind tunnel tests. Normally the factory in Norway would break the model but the wise people at Tesla respected the future value that this historic model will have and shipped it to the US!"

[Cobos]

Why was the clay model ever in Norway ? Do we have any companies doing that kind of stuff?

Cobos

[vfx]

Why was the clay model ever in Norway ? Do we have any companies doing that kind of stuff?

Cobos


"we"?





.

[TEG]

"we"?

As in him and all those other Norwegians...

[Cobos]

As in him and all those other Norwegians...
Yes, using we was maybe a bit presumptious, but I was refering to the collective Norwegian we :)

Cobos

[vfx]

As in him and all those other Norwegians...

So how would "we" know?

[Cobos]

I don't know :) I was just hoping someone had read or heard something?

Cobos

[TEG]

Nope, just the one reference on the Flickr photo.
My guess is that there is/was a "buck factory" in Norway, and they did the aero testing at a wind tunnel in Europe (perhaps the MIRA one in the UK). Apparently the buck was shipped back to the USA as a "conversation piece" as (from what I can tell) it had already served its' purpose.

[vfx]

... :)
:rolleyes::smile:

[Archaeopteryx]

http://www.teslamotors.com/display_data/aerodynamic2.jpg

Hmm... I've been using FLUENT 6.3 for a little while now, and I'm pretty familiar with the interface - It puzzles me that the above image has apparently been plotted as a graph of "Contours of Velocity Magnitude", when velocity magnitude graphs are used to describe fluid flow fields, rather than surface contours.

You see, the following is a graph of the velocity magnitude contours of a fluid flow field around a rudimentary circuit board represented as a box attached to a plane; the colors you see are plotted on a plane slicing through the fluid, and are correspondent with the velocities of the channels of fluid flowing around the box:

http://i354.photobucket.com/albums/r438/semi_automatic_pez_dispenser/001.jpg

But the image you posted was apparently a graph of the velocity magnitude contours of the actual surface of the car, which makes no sense to me. Plotting the surface of a car according to its velocity would yield an image like this:

http://i354.photobucket.com/albums/r438/semi_automatic_pez_dispenser/002.jpg

Because it's not the surface that's moving [that has velocity], it's the fluid around the surface which does, and thus can be plotted. I don't see how the image you posted was a plot of the contours of velocity magnitude of the surface of the car itself, as it appears to be, and I WOULD PAY GOOD MONEY for someone to explain to me what's going on here.

Seriously, if the aerodynamicist / computational fluid dynamicist of the Tesla Roadster does indeed participate in these forums, or can be reached via email or any other method, I would be extremely appreciative to ask him/her about this image.

Doug, if you have any idea how I might be able to find out more about this image, or if you know how to reach maybe one of the technical directors of the Tesla team I would wash your dishes & shine your shoes for a month. :smile:

[doug]

Ehh... my fluid dynamics is a bit rusty...
I might be misunderstanding you, but I don't see why the velocity magnitude contours have to be restricted to a plane. Can't you plot them on an arbitrary 2D surface existing in 3 space? Yes, the surface of the car isn't moving, and classically the flow directly next to the surface is zero. But shouldn't you be able to define a new surface a small distance, say a few millimeters, from the skin of the car and then plot your contours there?

At any rate, I don't know the guys at Tesla that work on this stuff. Your best bet would be to contact Fluent (http://www.fluent.com/), since they should have aero experts able to support their software. Or perhaps even MIRA (http://www.mira.co.uk/Services/Consultancy-Aerodynamics.htm) since they're the guys that likely produced the image.


.

[malcolm]

But shouldn't you be able to define a new surface a small distance, say a few millimeters, from the skin of the car and then plot your contours there?

Doug's right.

I think that if you do a plot of the true surface of the car then, as you would expect, the air in contact with the car body will be stationary and should be shown in blue.

I think the image of the Tesla is made by calculating the air flow at a fixed distance above/away from the true surface of the vehicle. I think this is why the struts supporting the wing mirrors look a bit too chunky and why the windscreen wiper has been ignored. Presumably the aim is to try to keep the air moving as fast as possible over the vehicle.

Since 30 m/s is about 108 km/hr or 68 mph does anyone know if the airflow over the wheels calculated with rotating or stationary wheels?

[doug]

Since 30 m/s is about 108 km/hr or 68 mph does anyone know if the airflow over the wheels calculated with rotating or stationary wheels?
Looks stationary.

[malcolm]

Looks stationary.


LOL

Sorry, stupidly worded question.

Although the wheels are shown stationary, is the airflow calculated with rotating wheels?

Depending on how you shape the sides of the wheel spokes could the wheels work as fans, forcing air outwards or drawing it inwards - or neither - if you have an even number of spokes and alternate their shape?

Would this do anything useful or would the effect be purely secondary - e.g helping reduce the build up of dirt on the alloys or creating harmonics which compliment the pitch of the motor?

Found this:

http://books.google.co.uk/books?id=XcFbEX-de4kC&pg=PA140&lpg=PA140&dq=vehicle+wheel+air+flow&source=web&ots=opJ4D6wwbN&sig=3U0GVe4AU7tjqHo2QdtRjEq6ygo&hl=en&sa=X&oi=book_result&resnum=8&ct=result#PPA141,M1

[doug]

I meant that the data look like the wheels are stationary.

[malcolm]

Yes I think you're right. How odd that the aerodynamic effect of rotating wheels isn't taken into consideration.

I guess the software can only model airflow over static obstacles.

[TEG]

http://farm2.static.flickr.com/1361/4726557574_ffd02b08e8_b.jpg (http://www.flickr.com/photos/wfryer/4726557574/sizes/l/in/photostream/)