M450 Steer Tire BlowOut

[davidbrady]

All I can do is point out some differences between my H3 and the M450. Given that Prevost has billions of road miles of experience this may not be for naught.

Here's a frontal view of my suspension.


You can see the Prevost kingpin that Ross talks about, circled in red. Having the kingpin inside the wheel gives the designers the ability to get kingpin inclination (KPI) and scrub radius as close to zero as possible - as opposed to SLA (short long arm) ball jointed suspension with uprights which necessarily have to fit outside the tire/wheel assembly. (Given the size of the hub, brake, wheel, and tire there are practical limitations). I don't know of any good result from either of these suspension characteristics with the exception that some KPI adds a degree of positive camber in a turn. Additional caster tends to add negative camber in a turn; with KPI the camber can be balanced out. KPI, caster, and scrub radius all lead to less steering feel, axle weight jacking in a turn, and greater loads on the steering system. The takeaway is that Prevost has more control over KPI, scrub radius, and caster, and Prevost takes steps to minimize stresses on steering components.

Another way they minimize stress is by adding a hydraulic cylinder to their power steering. Prevost uses a ZF power steering gearbox along with externally mounted hydraulic cylinder assist. This assist increases and balances the forces acting on the IFS steering system. Here's a view of the system:


The hydraulic steering box provides power to the bell crank; the power hydraulic cylinder provides power to the idle arm. The Prevost Docs go on to say:

"The hydraulic power cylinder provides an added source of assistance and being connected to the R.H. wheel, makes it such that the total steering forces are produced with minimal stress on mechanical linkages."