View all text of Subpart F [§ 1037.501 - § 1037.570]
§ 1037.526 - Aerodynamic measurements for trailers.
This section describes a methodology for determining aerodynamic drag area, C
(a) A trailer's aerodynamic performance for demonstrating compliance with standards is based on a ΔC
(1) Determine a baseline C
(2) Use good engineering judgment to perform paired tests that accurately demonstrate the reduction in aerodynamic drag associated with the improved design. For example, the gap dimension should be the same for all paired tests, and effective yaw angle between paired tests should differ by no more than 1.0°.
(3) Measure C
(b) The default method for measuring is the wind-tunnel procedure as specified in § 1037.530. You may test using alternate methods as follows:
(1) If we approve it in advance, you may instead use one of the alternate methods specified in §§ 1037.528 through 1037.532, consistent with good engineering judgment, which may require that you adjust your test results from the alternate test method to correlate with the primary method. If you request our approval to determine ΔC
(2) The principles of 40 CFR 1065.10(c)(1) apply for aerodynamic test methods. Specifically, we may require that you use coastdown measurements if we determine that certain technologies are not suited to evaluation with wind-tunnel testing or CFD, such as nonrigid materials whose physical characteristics change in scaled-model testing. You may similarly reference 40 CFR 1065.10(c)(1) in your request to use coastdown testing as an alternate method.
(c) The following provisions apply for combining multiple devices under this section for the purpose of certifying trailers:
(1) If the device manufacturer establishes a ΔC
(2) Trailer manufacturers may combine ΔC
(d) You must send us a description of your plan to perform testing under this section before you start testing. We will evaluate whether plans for wind-tunnel testing meet the specifications of § 1037.530, and will tell you if you may or must use any other method to determine drag coefficients. We will approve your request to use an alternate method if you show that your procedures produce data that are the same as or better than wind-tunnel testing with respect to repeatability and unbiased correlation. Note that the correlation is not considered to be biased if there is a bias before correction, but you apply a correction to remove the bias. Send your testing plan to the Designated Compliance Officer. Keep records of the information specified in this paragraph (d). Unless we specify otherwise, include this information with your request. You must provide any information we require to evaluate whether you may apply the provisions of this section. Include additional information related to your alternate method as described in §§ 1037.528 through 1037.534.