Originally Posted by AsianPersuasian:
I can see where USAC is trying to go with the concept of limiting RPMS. They comissioned Ilmor to perform dynamic analysis of the typical midget engine setups. This most likely included an analysis of modal performance (i.e. vibrations & harmonics) as well as strength/materials analysis given the engine operating at various RPMS. The numbers presented were probably the ranges with the best compromise of power vs. reliability. In other words, perhaps 8,700rpm for a pushrod engine hurts the HP/TQ, but yields gains in the modal performance department. Less vibration due to operating within an RPM range that does not contribute to harmonics would significantly increase the life of an engine. Apply the same concept to strength/materials of the engine components...you see where this is going.
Having said that, I like the eco-tech....bring it on.
Possible...Possible. You're right....they could have taken all of the motors, put sensors on them and gathered base information on the material properties used to assemble the individual componets.
They could have ran all of the motors on a spintron doing extensive RPM simulations based on the various tracks that are run. Using the base information; they could have then inspected the used parts verses the new parts and found an optimum operating range.
That....or they could have taken three people on staff....placed blindfolds on their faces with the names of the different motors.....and bobbed for apples with RPMS on them. Whatever they pulled out....was the RPM.
More than likely....the scenario was that they took RPM readings during the season and came up with what they felt the average was.
I doubt a sincere investigation into harmonics was performed. If it was....there may have been a case for higher RPMS. Thing about a dirt racecar...it's those things like corners and heavy clay and traction and things like that which makes motors do an extensive amount of grunt work.
Using a high RPM reading as basically a guide for making motors live longer is pretty short sided. Those numbers are often a "flash" number. A number that is just for a brief moment. It's not a sustained number except at somewhere like Pheonix or Belleville or the alike. These motors don't operate constantly at the 10,200 range or 9,200 range. They spend most of their lives in the 4,200 to 6,000 range. That isn't going to change.