Public Meeting with ROHVA, SEA, and CPSC Staff

Advance questions/requests of ROHVA

Re: ROHVA Presentation to CPSC Staff on November 10, 2011

1. The SSF data presented by ROHVA does not specify loading conditions for the various bar graphs. Is it 

possible for ROHVA to share those details regarding the data with the CPSC staff? The data is meaningless 

without this information. Also, please provide the track width data for each vehicle (A through K) that was 

used to calculate the SSF values.

2. Would ROHVA share the data (angles and weights) obtained by the “SAE suspension” method that was used 

to determine the center of gravity (CG) height measurements for each vehicle?

3. For the J-turn data presented by Carr Engineering, please provide data plots for each J-turn event conducted 

for each vehicle. Please include for each set of data plots the test vehicle load condition and total weight. 

Also, please include plots verses time of corrected Ay, speed, yaw rate, roll rate, and steer angle.

4. In the presentation slide titled “Off-Highway Steering / Vehicle D” Carr Engineering compares four test 

conditions for vehicle D. Please provide the load conditions for each of the four test conditions.

5. Several of the presentation slides are titled “Off-Highway Steering” and present data for steering tests 

allegedly conducted on a dirt surface. Other ROHVA vehicle dynamics experts have stated that reliable and 

repeatable steering testing is not possible on dirt surfaces, please quantify the reliability and repeatability of 

the steering tests conducted on dirt by Carr Engineering Inc. (CEI).

6. Please provide wheelbase measurements for each of the vehicles (A through K) tested By CEI.

7. Did Carr Engineering Inc. (CEI) allow the outriggers to contact during the drop throttle J-Turn tests as 

indicated in the title of the slides? If so, why did they test to outrigger contact instead of 2 wheel lift per 

SEA’s test protocol?

8. Why does ROHVA believe the OPEI analysis of the SEA data represents a 19% variation in Ay? The report 

clearly states that the range for ONE vehicle was .03 g which is 19% of the .16 g range for all 11 vehicles 

tested. If the Ay of the ONE vehicle is .8 g (typical for this class of vehicle) the range of .03 g represents 4% 

variation...not 19% variation as represented by ROHVA in its presentation.

9. Will CEI share the raw data on the drop throttle J-turn Ay test variability tests of the vehicle that show a 22% 

variation in measured Ay (.72 g one run, and .88 g in another run)? Did CEI verify the accuracy of their Ay 

reading or calculation by comparing the yaw rate and velocity (V x r) or velocity and radius (V2

/R) during a 

steady state circle test?

10. Will CEI share the raw data on the drop throttle J-turn minimum Ay tests that show CEI’s inability to 

determine the Ay for 3 of the 11 vehicles tested? Why were the tests run to outrigger contact when such 

contact prevents measurement of the minimum Ay threshold?

11. Did CEI run drop throttle J-Turn minimum Ay tests repeatedly to compare maximum Ay just before tip-up 

and minimum Ay at tip-up? SEA used this method to verify the minimum steering magnitudes required for 

tip-up...did CEI do the same?

12. Why did ROHVA present a graph of SEA’s data showing vehicle G in the GVW condition in the 30 mph drop 

throttle J-Turn test to the left? The slide points out .68 g and .72 g Ay points on the plot. The plot was 

presented in the SEA report alongside other plots of the same vehicle but showing the steer angle, speed, 

roll angle, and yaw rate. If one reads the roll angle and yaw rate plots, it’s clear that .68 g is the Ay value for 

rollover and the .72 g value is a spike that occurs well after the event.

13. How many drop throttle J-Turn runs were performed on Vehicles J and Vehicle B? The graphs showing 1.03 g 

and 1.10 g Ay defy explanation as those values exceed the SSF value of the vehicles. Is there video of the 

run that showed a peak Ay of 1.10 g, with sustained (over 1.0 sec) Ay over 1.0 g?

14. Does ROHVA have any reference from NHTSA or any other independent vehicle dynamics experts in support 

of oversteer as a desirable vehicle characteristic for a vehicle? Any text book references or SAE papers that 

refute understeer as a desirable inherent characteristic of the vehicle that should be part of the vehicle’s 

design?
15. Does ROHVA/CEI distinguish between (1) oversteer as a vehicle characteristic due to the design of the 

vehicle and (2) oversteer caused by vehicle kinematics such as drop throttle or braking in a turn or 

maneuvers on variable friction surfaces such as dirt or ice?

16. What is the SAE reference that describes the SAE Suspension Method for CG Height measurement?

17. In addition to the CG height information, would ROHVA share the data on CG lateral and longitudinal 

locations for each vehicle and loading condition?

18. Please provide information on the outriggers used during the Carr Engineering dynamic tests. What is the 

weight of the outriggers used? What are the corner weights of the vehicles with the dynamic test 

instrumentation, outriggers, and driver? Were any measurements made of vehicle CG heights with the 

outriggers mounted on the vehicles? Were any efforts made to adjust vehicle loading during the dynamic 

tests to match any specific operator/passenger loading conditions?

19. For the J-turn data presented by Carr Engineering, the ground plane lateral accelerations are plotted. Are 

the ground plane lateral accelerations measured directly by a sensor, or are they derived from 

measurements made using a sensor that measures body-fixed accelerations? If a calculation is used to 

compute ground plane (roll corrected) lateral acceleration, please provide the equation(s) used to make the 

correction. If roll angle is used in the correction equation, please describe in detail the method used to 

measure or compute roll angle.

20. Please provide a list of all instrumentation (on vehicle sensors and data acquisition equipment) used during 

the dynamic tests. Also, please provide descriptions of where the instrumentation is mounted to the 

vehicles during the dynamic tests.

21. Please provide information on the data sampling rates and data filtering used for all dynamic tests.

22. The data from the Carr Engineering circle tests appear to be discrete points. Describe the process used for 

collecting and measuring data for the circle tests. Please be specific on how the data collection is triggered, 

the data collection duration and sampling rate, how the data is averaged or filtered, and how the lateral 

acceleration is determined (is it V2

/R as indicated on the graphs).

23. A slide titled “J-Turn Ay Measurement” from the November 10, 2011 ROHVA presentation to CPSC contains 

a bullet that says, “Results generated by CEI (using SEA methodology) show a wider range of rolling 

motions.” Please provide more details for the basis of this comment. On the few plots from J-turn tests 

provided, the roll rate traces from CEI do not appear to be too much different from roll rate traces from SEA. 

Is there a wider range of roll angles? No roll angle plots are provided in the November 10, 2011 

presentation. 

24. A slide titled “J-Turn Ay Measurement” from the November 10, 2011 ROHVA presentation to CPSC contains 

a bullet that says, “Some vehicles displayed rolling motions which prevented an accurate or reliable 

measurement of Ay”. Please provide more details for the basis of this comment. Does this issue have to do 

with the CEI measurements of roll angle only, and how the roll angle is used to compute the Ground Plane 

Lateral Acceleration?