[Archived]

Around page 92 of the report linked above is a pictoral summary of part failures. I presume the failures are the result of the test course and are not because of infancy failures. What those photos do show however is that when doing routine maintenance those are failure points worth getting a detailed inspection.

The coach is a Volvo engined coach so it is not going to be totally applicable to most of the coaches here, but it will give some insight into our coaches.

[jack]

I’m surprised at the sway bar related failures along with the bulk of suspension bolt failures. I assume the test track at Penn State is a real torture test.

It also appears that this bus was eating up steer and tag axle tires at an alarming rate. With the tests they were doing, I might understand the steer tire wear but the tag?????

[Jim/Chris]

I did not notice in the report if the test track was elevated or not, gary

[Rod]

Depending on how sharp the turns are it is entirely possible to eat up a tag axle tire. From my experience if a tag axle tire starts getting an unusual wear pattern the race towards that tire becoming trash is very fast. If I detected any unusual wear on the steers or tag I immediately put those tires on the drive which would usually correct the problem. I never ever put unusually worn steers on the tag because they not only wouldn’t straighten out the wear, the wear pattern would continue but at a seeminly rapid rate.

Of course all that is with all tires being 120 or 315. Now with 365 and 315 on the coach there is no way to remediate a tire with unusual wear.

I agree with the test being a torture test. I think it is supposed to emulate 500,000 miles of in service use. I was extremely pleased to see the chassis has so much structural integrity and does not twist.

[Rick & Denise]

If the buses didn’t break the test would be next to worthless. My hope is that the manufacturers take this information back to the design table and make modifications. I suspect manufacturers pay some attention to class 1 and 2 failures but let everything else slide. If you scan thru the test results of the various manufactures you’ll see that sway bar failures are epidemic. It seems sway bars are treated as an after thought and are woefully underdesigned; the bars, the attachment points, and the bushings. With air suspension, big pipes, high flow valves, and a lower center of gravity, sway bars may be eliminated. An active air suspension can level the bus. Instead we have to struggle with keeping bushings in our sway bars! We already have ABS, road hazard radar, stability control, and maybe even some semblance of active ride. Prevost doesn’t seem to shy away from electronic control systems.

[Archived]

I suspect (but don’t know) that the sway bars are the first and only line of defense in a bus to counteract a hard lean in driving. If a coach enters a sharp turn it’s initial reaction is going to be to lean to the outside of the turn. At some point the air bags on that side will get more air pressure to counteract the lean due to the ride height valves, but until then the sway bars are helping to compensate.

But I agree given the beating the sway bars and attach points get I would think the chassis engineers would be looking hard at solving the problems with breakage. I doubt if the bus would roll over when the sway bar breaks, but I have to believe it gets the driver’s attention with the sudden snap and rolling moment.