Not sure how accurate this "toy" is but should be close enough for general trends. I'm scanning a ~1:25 scale car, not a ~1:64 scale matchbox type. This was my first shot at the scan and as you can see it needs additional angles and better resolution but I thought I'd give you an idea what's in store.... This was my first time using a 3D scanner!



Once I get a good composite point cloud put together (STL file) there will undoubtedly be a fair amount of clean up in CAD before sending to CFD (CD-adapco STAR-CCM+). I'll probably run the first case with a smooth underbody and no internal flows. Putting together a halfway representative underhood is going to take some time but that will be the next step, and the rear space around the diff and spare. I've got a '70 sitting outside that I'll use to verify the scale and establish baseline ride heights and whatever other dimensions I'll need going forward. Its engine is coming out soon so I'd better measure first!

Planned runs so far are:
Without internal cavities:
-Baseline ride heights and 2" increments F and R, probably 4" in each direction.
-Variable air dam lengths in stock position.
-Extended "duck tail" spoiler, like Pace Car. 1 or 2 lengths, I predict ineffective.

Anything beyond that is pointless without internal flows so once I get those CADed up:
-Rebaseline with ride height sweep again, now 1" resolution.
-Air dams again, probably more extensive variations. Radiator block-off.
-Deck lid spoiler again.
-Side skirts, smooth underbody panels, diffuser (the latter I'm sure will be ineffective). Then whatever other speculative ideas I/we can come up with!

Note that the absolute numbers from these studies should be taken with a large grain of salt. Beyond the questionable accuracy of the toy model, this CFD software isn't awesome at matching drag numbers, though usually okay on lift. Without validation it's even more an unknown but at least A-to-B comparisons of major changes should decently reflect reality.

That's about as far out as I'm willing to predict. Note this won't be done tomorrow! It will probably be sporadic but I'll try to maintain forward progress and keep you all interested with some colorful pictures now and then. If anyone has done this before, let me know, I've never seen it! The 3D scanner is brand new to me but (automotive) CAD and CFD are what I do.

Using: http://www.nextengine.com/ via http://www.techshop.ws/


-Chris

 

Subscribed.

FWIW, it might help dial in accuracy to take into account the PC package (dam & spoiler) was said to have reduced CF by ~15% vs the standard '78-79 fastback body. You've probably seen that before, but didn't want to assume...

Also, I don't recall ever seeing any specific lift/downforce numbers between those two particular configs, but the instrument I sit on definitely regerstered greatly improved high-speed stability in seriously fast sweepers, so I wouldn't categorically count out the rear PC spoiler altogether based on its function (or lack thereof) on pre-'78's.

In any event, count me in as one who can't get enough of this kind of stuff. Ought to be very interesting to see what the modeling yields...

 

 

Some interesting video

 

WOW. Very cool. Just one question, please.
At what speed/speeds are the lift, drag, and HP required measured?

 

Kj

 

Also subscribing.

College for me was Cal Poly Pomona. While there another studentin an Aero class did a real wind tunnel test using 1/8th scale models of a 63 Vette and a mid 70's Vette. The big Monogram models built as supplied, so side windows down, radiator was solid, whatever concessions to making a scale plastic model. The 63 showed better numbers in his tests that the later C3 type car.

Interested in following this thread.

Best,
Tom

 

Please note that the C3 data in the Accumulative C1-C6 Aero Breakdown doesn't cover all five primary itterations of the C3 body during the model run ('68-72, '73, '74-77, '78-79, '80-82), not to mention the PC dam/spoiler package.

 

I'd love to see the differences between a hardtop on a convertible and a t-top coupe with the flat back window. My gut tells me there would be a big improvement with the hardtop. The fast road racers and salt flat cars of the time mostly used hardtop cars. There must have been a reason.


Pete

 

This was interesting.

Historic Mercedes-Benz Measured in Wind Tunnel

http://www.sportscardigest.com/histo...n-wind-tunnel/

 

I agree that is very important, big differences in the years especially when you hit '80-82. My '70 Cuda had standard steering and at 120mph it felt like there was power steering because of the the lift on the front end.

My '80 Corvette's rubber piece along the bottom of the the air dam is only 2 inches off the road and I believe at speed it is even lower and very stable and easy to drive at 120mph while my Cuda scared the crap out of me at 120+mph due to the lift instead of down-force it should have