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Welcome to the Inside Track with ARC. The Auto Research Center is a specialized research facility serving the motorsport, production, commercial, government and bicycle industries. The ARC global headquarters is located in Indianapolis, Indiana which hosts their 50% scale wind tunnel, 7-post, drivetrain test rig, bicycle test facility and CFD cluster center. ARC offers a wide range of solution packages to further speed and efficiency.
DIFFERENTIAL TESTING
The drivetrain test rig, developed by ARC, is one of the most powerful test rigs for public use. The dyno is able to simulate race conditions with input power of over 600 hp and speeds of 9000rpm. On the ARC Drivetrain Test Rig, the performance of a gearbox and rear end or transaxle can be accurately measured and optimized.
The ARC drivetrain rig allows for independent control of RPM on each absorber. This opens up the possibilities of testing beyond the standard efficiency testing of oils, coatings, etc.
Various types of differentials can be tested on the rig and their performance characteristics quantified. Other differential test rigs only test the differential in isolation. The ARC Drivetrain Test Rig allows for the testing of the differential as it is installed on the rear end or transaxle, so all of the losses and effects are accounted for.
To learn more about the drivetrain test rig, download the brouchure, email sales@arcindy.com, or call 317-291-8600.
STYLING STUDIO CLAY MODELS IN
ARC's WIND TUNNEL
Getting faster feedback on aerodynamic changes to early prototype body styling by using scale clay model in the ARC rolling road wind tunnel provides for more innovation. It will allow active sculpting to be done on a model and then a test run to get instant results. This will help transform the development of a vehicle and give the styling studio more direct impact on results.
By shaping the car in the wind tunnel, it will push the design to the optimal performance quicker. ARC has the capabilities to take the clay model and add the elements needed to put it into a rolling road wind tunnel. Wheels can be made at ARC, testing with a simple suspension for wheels or mounted externally on wheel arms. ARC designs the wheels to fit various platforms that can be used over several projects in order to make it more effective. Mounting of the model to the ARC wind tunnel measurement system would be done in-house at ARC. All this allows a clay model to go into a wind tunnel faster than ever.
To learn more about ARC's offerings for the Production Car OEM Industry, visit the ARC website, call 317-291-8600 or email at sales@arcindy.com.
REYNOLDS NUMBER FACTS
It has been falsely recommended by some parties that a single Reynolds number is needed for all commercial vehicle testing. Based on the methodologies and testing methods used in the commercial industry, ARC finds that the Reynolds number is not the biggest contributor to accuracy of results. There are bigger hitters to impact the accuracy of testing numbers than Reynolds number effects.
At its core, Reynolds number is characterized by model scale, test speed, air density and viscosity. To correlate different testing methods, there are a large number of factors that have to be accounted for. These include:
| Model scale |
Test speed |
| Model fidelity |
Rolling vs. stationary road |
| Size of rolling road |
Blockage ratio |
| Horizontal pressure gradient |
Correction methods |
| Mounting interference effects |
Boundary layer thickness |
| Flow uniformity |
Flow angularity |
| Turbulence levels |
Temperature control |
| Yaw range covered |
Repeatability of test method |
| Compromises due to model length (e.g. half-length trailer) |
Testing Center/Software |
This list has a much larger areas of refinement that can have an effect on what produces different Cd.
To learn more about ARC's offerings for the Commercial Industry, visit the ARC website, call 317-291-8600 or email at sales@arcindy.com.
NACFE HOSTING EFFICIENCY
CONFERENCE AT ARC
On December 9th, NACFE (North American Council for Freight Efficiency) will be hosting a daylong event in a non-commercialized format at the ARC Indy Headquarters. There will be discussions on general trucking issues, expert panel, open forum, roundtable topic discussions and real time wind tunnel testing education. Sign up will begin soon at the NACFE website.
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TECH ZONE
"I am hearing a lot about Reynolds number and testing at a specific number. What does this all mean?"
Reynolds number is one way of ensuring good correlation between different test methods, e.g. wind tunnels, CFD, track and road. However, it is not necessarily the most significant aspect. There are numerous other factors that can be more important, such as the accuracy of the model, whether a rolling road is used, steady state vs transient CFD, use of an appropriately sized rolling road, etc.
The fact of the matter is that ARC's 1/8th scale models and tunnel were compared to track data by the EPA and found to be more accurate than all the CFD methods that were also evaluated.
TECH ZONE is an additional area of our newsletter where each month a customer question will be answered by the related expert at ARC. So, please send in any questions you might have, from wind tunnel test instrumentation, CFD workings,to tuning your shocks.
Ask your questions at techzone@arcindy.com
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