Impact loading on driveline 1

[jp_1726]

Hi,

I work in a company that design driveline components for on-road truck, from light duty f450 to full size city buses.

I’m routinely doing stress analysis on different component (flange, splined connection, shaft..) that are located somewhere in the driveline between the differential and the engine. Unfortunately, we aren’t integrator so we don’t have that much information about real life load cases for these component.

I’m curious about the dynamics/inertia loading in the driveline caused by impact, pothole, wheel slippage on ice… The worst I can imagine is wheel spinning on ice then catching on the asphalt. I wondering if this kind of event lead to significant torque loading in the driveline. Does the driveline components between the road and the engine have enough compliance to filter the shock. We usually suppose an amplification factor on the maximum engine torque to do the stress analysis. What kind of amplification factor is realistic?

Machinery’s handbook specify some amplification factor varying from 1 to 2.8 for involute spline calculation depending on power source and load type.

Does anybody have some experience on that subject?

Thanks

 

[gruntguru]

"The worst I can imagine is wheel spinning on ice then catching on the asphalt."

In that instance a significant portion of the torque generated by hitting the asphalt, is dissipated in slowing the spinning wheels, so the shock loading is not as bad as you think.

Far worse is the clutch-dump launch on asphalt, where the torque required to accelerate the wheels is added to the torque required to break traction.

je suis charlie

 

[jp_1726]

You are right. The clutch-dump situation is probably harder on the drive line that the wheel spinning on ice.

In both situation, I think the main source for the shock loading is the high inertia of the diesel engine. In both cases, there is a rapid engine deceleration that leads to high torque on the driveline. This load case is severe because the driveline see the max engine torque (if the throttle is wod) + the inertia torque. I tend to think that driveline compliance has a great influence on the inertia torque. A more rigid driveline leads to quicker deceleration and higher inertia torque.

I don't have any kind of real life value for these situation. I'm looking for these number.

 

[GregLocock]

The proper way of doing it is this, or equivalent

http://www.kasensors.com/en/products/drive-shaft-torque-transducer

If you can't instrument a vehicle then one option would be to build a dynamic system model of the driveline and then use an accurate RPM trace from the engine, and ideally the output from the ABS tone wheels, and then stuff around until you get a good match. The rate of change of rpm tells you a great deal.



Cheers

Greg Locock


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