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Discussion Starter #1 (Edited)
Ok this is a once in a lifetime opportunity. At LaPorte High School we have a program for students who want to explore the world of engineering. It is called Project Lead the Way. Students have to write technical papers and use science to prove theories.

Here is the problem (It would make Mythbusters proud!) Does a 1:64 Diecast car have the same Drag Coefficient as a 1:1 car? Interesting science at work here. The teacher who runs this project at LaPorte High School asked me to supply the 1:64 cars. I wonder where he got the idea that I would have some? I digress...I brought in my Gravity racing case full of assorted racing cars, Muscle Cars and of course a couple of VWs.

My request to the teacher is to present findings at AutoFest. This could be interesting.....


Supplied cars by make:
Johnny Lightning:
1964 Classic Plastic VW Bug
1964 Black with Flames VW Bug
2003 Import Heat Mitsubishi Lancer Evolution (WL!)
1970 Plymouth Barracuda - Going to Gerald after the experiment...His contribution to the world of science!
1969 AMC AMX (Plastic Base)
1990's Nissan 350Z - Bobby Williams Special!
Shelby Daytona - Bobby Williams Special!
1960's Topper (Commerative) Custom L
1973 Pontiac Grand Am
Mach Five (the devil made me do it)

HotWheels:
1967 Pontiac Firebird 400
1941 Willies Drag Car (For you Bill!)
1969 Dodge Coronet Super Bee
Ford GT LM
George Barris Batmobile

Matchbox
1962 Jaguar E-Type Coupe (always loved this car)

Tom Z. want to get on board and make an educational (and tax deductable)donation? Contact me!

Any thought on the results?
 

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Sure!
I will say that even if it is scaled down correctly, the 1:64 vehicle will not come close to having the same coeffient. The drag is totally different and it probably doesn't have the consideration of the designers.
The reason I say this is that most of the designs of the models were to replicate the body of a 1:1 car, not how it would perform on the road/track.
For instance; the HW Bugatti Veyron with the FTE wheels technically should have blown the wheels of of a JL Mustang Mach 1 with rubber tires. The lime green Mustang jumped off the track 2 times and still beat the bugatti by 2 car lengths. If there was a drag on the cars then it must of been on the bugatti because the stang did not appear to have any.
This is just my observation.
Richard
 

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There are varialbles at work here. The Cd will be the same on the upper part of the body if the casting is correctly done ie; spoiler angles, hood and truck area rake, flush windows etc....

The underside is where it's trickier, tires and wheels must be spot-on in scale, likewise the smoother undercarriage of a model is much differant than a muffler hanging down.
What was the question :confused:
 

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Discussion Starter #4
I hear what your saying and I don't expect a perfect match. I'm wondering if the results would be close. If the scale is correct and the details are close then the numbers should be reasonably close. The question might be asked, What is close?
 

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I'm going to say no,a 1/64th scale car will not have the same drag coefficient as a 1:1.
Downforce and aerodynamics come into play.
At the slower speeds of a toy car,downforce and aerodynamics have no bearing on the drag coefficient.Toy cars just don't travel fast enough to have any measurable amounts of either downforce or aerodynamics.
At the faster speeds of a 1:1 car, downforce and aerodynamics are directly related to drag coefficient because there is a very large measurable amount of downforce and aerodynamics.
I hope you guys understood what I just said because I didn't. :D

When my Son and I were into racing pinewood derby cars,we seen some very sleek and aerodynamic looking cars beat by rectangle blocks of wood with wheels attached.
:wave:
 

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I just tried this experiment and found that it's easier to drag a bagful of 1:64 cars down the street than it is even just one 1:1 car. I could have dragged the bag of diecast cars for a mile or so with ease, but the 1:1 was so hard that I only got about a foot or so before I ruptured myself. I hope this helps Chris. I need a medic.:drunk:
 

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It wont for multiple reasons, but could be reasonably close provided they properly test for the CD of the 1:64th. How to properly test the model would have to be part of their "DISCOVERY".

Tom Kubler, Aerospace engineer
 

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I would say that it would even go beyond the smooth chasis of the dicast (which is no small thing) to the thickness of the metal used in dicast, compared to the relatively thin meatal, or fiberglass used in most 1/1s these days. And what about the plastic insides compared to the various materials in a 1/1? Much like Richard observed on a track, I've also seen bulky cars that wouldn't stand a chance against their competition in real life, blow away cars that should be more streamline and faster. Then again, you have gravity vs. an engine on a track. And even if you push two different cars with equal thrust on level ground, it has to be a lot different than an engine, which has way more power, not to mention wieght that will also be missing from any diecast, no matter how acurate the scale. I would also wonder how correct and to scale the hight is from ground to base on various brands of diecast, where you can have varients from company to company on the same car, compared to any given 1/1 model, which is factory made by one company. That theory would also apply to various wheels, bases, every detail, in point of fact, when you consider each die has to have their subtle (if not great) differences from company to company. All this provided you can actually get some type of scale for the speed needed to generate such a test. I agree with Triple20 on that.

I'm not sure how all this, or any of this, will factor into your school's test--since I'm not certain how they are actually going to perform these tests. But I would say there has to be a substantial difference in there somewhere--possibly even with the same car made by various companies with different dies.
 

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I would say that it would even go beyond the smooth chasis of the dicast (which is no small thing) to the thickness of the metal used in dicast, compared to the relatively thin meatal, or fiberglass used in most 1/1s these days. And what about the plastic insides compared to the various materials in a 1/1? Much like Richard observed on a track, I've also seen bulky cars that wouldn't stand a chance against their competition in real life, blow away cars that should be more streamline and faster. Then again, you have gravity vs. an engine on a track. And even if you push two different cars with equal thrust on level ground, it has to be a lot different than an engine, which has way more power, not to mention wieght that will also be missing from any diecast, no matter how acurate the scale. I would also wonder how correct and to scale the hight is from ground to base on various brands of diecast, where you can have varients from company to company on the same car, compared to any given 1/1 model, which is factory made by one company. That theory would also apply to various wheels, bases, every detail, in point of fact, when you consider each die has to have their subtle (if not great) differences from company to company. All this provided you can actually get some type of scale for the speed needed to generate such a test. I agree with Triple20 on that.

I'm not sure how all this, or any of this, will factor into your school's test--since I'm not certain how they are actually going to perform these tests. But I would say there has to be a substantial difference in there somewhere--possibly even with the same car made by various companies with different dies.
Chassis smoothness is definately a big factor on 1:1 cars. They make belly pans for some cars on the dry lakes runs. Ride hieght too is crucial.

Thickness of metal is an interesting point I've never heard disscussed. The only way that would matter in a 1:1 is if the extreem forces at high speeds would make large spances of un-reinforced sheet metal "oil can"...pop up or down - changing it's shape would effect aerodynamics. Sheet metal or 'glass shouldn't make a differance unless one would hold it's shape better than the other.
 

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Chassis smoothness is definately a big factor on 1:1 cars. They make belly pans for some cars on the dry lakes runs. Ride hieght too is crucial.

Thickness of metal is an interesting point I've never heard disscussed. The only way that would matter in a 1:1 is if the extreem forces at high speeds would make large spances of un-reinforced sheet metal "oil can"...pop up or down - changing it's shape would effect aerodynamics. Sheet metal or 'glass shouldn't make a differance unless one would hold it's shape better than the other.
Didn't think about flexibility of the metal...but sounds like that won't apply from what you're saying.
 

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Discussion Starter #16
It wont for multiple reasons, but could be reasonably close provided they properly test for the CD of the 1:64th. How to properly test the model would have to be part of their "DISCOVERY".

Tom Kubler, Aerospace engineer
The school does have a small wind tunnel to test the Cd of wings that are build by the students. The set up allows for the object (Wings or 1:64 cars to be Zeroed out to eliminate down force or lift. (they can be tilted up or down and results can be measured)
 

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Discussion Starter #18
I just tried this experiment and found that it's easier to drag a bagful of 1:64 cars down the street than it is even just one 1:1 car. I could have dragged the bag of diecast cars for a mile or so with ease, but the 1:1 was so hard that I only got about a foot or so before I ruptured myself. I hope this helps Chris. I need a medic.:drunk:
Oh Zeb! You didn't take in consideration the Cd of yourself (Because of the additional drag of your moustache!)
 

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Discussion Starter #20
I hope to have a power point at AutoFest as there might be some people interisted. I can also post some things here when the students are done. I don't know how long it will be, I don't teach that class.
 
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