Recent content by RigTest

gt6racer: we must label our quadrants differently, as I would refer to the 2nd and 4th quadrants (Force-Velocity) as the active-only regions (energy input) and the 1st and 3rd quadrants as the passive regions (energy dissipated). These 'semi-active' systems where damper or spring...

ttx40: In addition to Greg's example you can picture a Force-Slip Angle curve. At the force peak the force sensitivity to slip angle (slope of curve) necessarily drops to zero (definition of a peak), so the tire will not respond to small changes in steer. It may or may not be sensitive to...

ttx40, nobody owes me an apology. You asked a question, probably wanting to tap into the wealth of knowledge and experience of the members on this site. I think Cibachrome's answer is fine, but I felt that the context was missing and I wanted to clarify...he/she may still disagree anyway...

Note: I'm the author of the F1-Technical post, but my normal username (GSpeedR) has registration issues. Cibachrome: I think that you've (inadvertently) taken the post out of context, and completely ignored/missed the first sentence: "The yaw moment contribution from steer can be quite...

Yes, he pointed out that I was using the wrong force. Our argument was about one of the equations.

I think we're on the same page now. Good points, especially regarding contact patch mass. My tire models are more complicated than what we've discussed (ungrounded, more elements than just parallel-spring-damper) but certainly not an FTire model or anything. They are probably inadequate for...

Fair enough, I will stop posting. GregLocock obviously doesn't agree with me, any future readers can see what we've posted and draw their own conclusions. I appreciate the help.

The point I have been trying to make is that F_pad = F(tire to hub). The reason is that ideal spring and damper elements transmit force directly, so the force is unchanged from the pad up to the hub mass. I have done plenty of FBDs, I can represent this in simulation, and I have measured...

You wrote this: "tire work= Fpad.xpad-F(tire to hub).xhub" Please, explain to me where 'F(tire to hub)' would be measured at?

Greg, when you say "component" do you mean "masses", and therefore you are referring to a multi-DOF system? For SDOF, assuming ideal elements (mass-less springs/dampers and rigid masses), force is transmitted instantaneously through an ideal spring and an ideal damper, without change in...

I don't want to come across as dismissive of Greg's post. I feel that I did not properly describe the setup and the problem that I am attempting to solve. Let's just simplify to a single spring-mass-damper system, with the spring/damper attached to the actuator pad. It seems as Greg is...

Thanks for the reply, Greg. I don't know if this changes your opinion, but I am attempting to determine the energy dissipated by the damper(s). If we simplify to a single DoF system as a tire on a pad, then the input force is transmitted directly into the tire damper/spring. My thoughts are...

Sorry for all the editing (I guess there's no way to edit posts). To clarify the spectral calculation: cpsd(x(t),F(t)) = E_real(w) + E_imag(w)*j I take the real part, which is the dissipated energy, while the imaginary part is stored. Hopefully I'm not off base here.

I'll add that I expect the summed energy of the tire + damper to equal the input energy - environment losses. E_total = E_tire + E_damper = E_input

Hello everyone, I have been struggling to properly calculate energy ratios (energy dissipated/energy input) in servo-hydraulic test systems. Specifically, the test specimens are quarter-car (2DoF) suspensions, which include tire compliances. The rig is capable of many excitation waveforms...