Bad Coach rollover

[Joyce M]

Well, My '88 Winnebago was built in the era when they picked-em up and dropped them on the roof...Anyone remember those ads?..
I feel pretty safe tooling down the old highways vs. the freeways whenever I can at usually 5 mph lower than the limit....New shoes on the front and I'm retired and in no hurry at all to get wherever...
Safe rides to everyone!

[NeilV]

Originally Posted by richard5933

Please - not another thread morphing into an endless conversation about tire blowouts and the science that is/isn't involved...

I would have thought that decades of commercial truck and bus driver training backed up by tire manufacturer empirical studies concluding that stabilizing by pressing on the accelerator to stop the drift and then gently pulling over had put a rest to this debate. A right front blowout for example with a left steer correction without accelerating is going to drop the right front harder to the ground increasing the need for more left steer to keep going straight until steering angle becomes so severe that you roll it over. Stunt drivers roll vehicles to the right with a hard left of the steering wheel along with an application of the brakes without a blowout or the assistance of a ramp. A blowout with its tire drag can act just like tapping the brakes so combine that with left steer before regaining control and just like that stunt man you can be rolling over very quickly. The videos showing the differing results of using just steering correction and then using the accelerator on vehicles equipped with outriggers to prevent a full roll over amply demonstrated this too. Most time with just steering correction the trucks ended up riding on the outriggers and obviously would have gone completely over if they had not been there. Unfortunately one can't drive down the highway with outriggers to prevent roll overs on their coaches.

[Cloud Dancer]

n2zon,
The torque that you speak of is NOT about the center of gravity of the motorhome. It will be about the axis of the spindle's kingpin. And because there is a mechanical link from the spindle to the steering wheel, the driver will feel it (if his hands are on the steering wheel). THAT's what triggers him to concentrate on the correct steering management. NOW, if the driver is temporarily incapacitated, this "torque" will quickly turn its spindle AND this will turn the other spindle AND the motorhome will end up in the ditch. It takes a steering action to make a change in direction. It's amazing how well it works.
Note:

[Brick Pilot]

"Benign?!"
It must have changed immeasurably in the last 6 months then.... I used to drive it both ways 4-6 times a month, at all hours, and 205 has never been less than stressful! Usually backed up, with cars pulling foolish stunts the whole way! Be glad -
We have had wildly different experiences on that highway!

[Brick Pilot]

this begs the question:
What brand/style/years of Class A motorhome do you all feel is the best bet in a serious crash...?

[richard5933]

Originally Posted by Couch Pilot

this begs the question:
What brand/style/years of Class A motorhome do you all feel is the best bet in a serious crash...?

I think that depends what type of crash you're talking about. Totally different protection needed for front impact protection vs. rollover protection.

I've seen videos showing front end crash tests on buses where the front few feet of the bus disappeared on impact with the wall, yet the same model bus was easily able to withstand the rollover test. Totally different type of stress placed on the structure. I'm sure the same would be true for a motor home.

Lots of motor home manufacturers claim to have steel caging in the front to help protect front seat passengers. But, do they have protections to keep the body shell from separating from the chassis on rollover or from disintegrating on impact?

[n2zon]

Originally Posted by Cloud Dancer

n2zon,
The torque that you speak of is NOT about the center of gravity of the motorhome. It will be about the axis of the spindle's kingpin. And because there is a mechanical link from the spindle to the steering wheel, the driver will feel it (if his hands are on the steering wheel). THAT's what triggers him to concentrate on the correct steering management. NOW, if the driver is temporarily incapacitated, this "torque" will quickly turn its spindle AND this will turn the other spindle AND the motorhome will end up in the ditch. It takes a steering action to make a change in direction. It's amazing how well it works.
Note:

Fair point. There is more than one axis for the torque generated by the drag from the flat tire. One about the kingpin that results in force on the steering wheel and one about the CG.

[n2zon]

Originally Posted by NeilV

I would have thought that decades of commercial truck and bus driver training backed up by tire manufacturer empirical studies concluding that stabilizing by pressing on the accelerator to stop the drift and then gently pulling over had put a rest to this debate. A right front blowout for example with a left steer correction without accelerating is going to drop the right front harder to the ground increasing the need for more left steer to keep going straight until steering angle becomes so severe that you roll it over. Stunt drivers roll vehicles to the right with a hard left of the steering wheel along with an application of the brakes without a blowout or the assistance of a ramp. A blowout with its tire drag can act just like tapping the brakes so combine that with left steer before regaining control and just like that stunt man you can be rolling over very quickly. The videos showing the differing results of using just steering correction and then using the accelerator on vehicles equipped with outriggers to prevent a full roll over amply demonstrated this too. Most time with just steering correction the trucks ended up riding on the outriggers and obviously would have gone completely over if they had not been there. Unfortunately one can't drive down the highway with outriggers to prevent roll overs on their coaches.

While I knew that coming off the gas and braking were bad before the vehicle was stable, I found the advice to accelerate surprising, but from dozens of sites (including some sponsored by tire manufacturers) I see you're entirely right. Learn something new every day.

[Cloud Dancer]

Originally Posted by n2zon

Fair point. There is more than one axis for the torque generated by the drag from the flat tire. One about the kingpin that results in force on the steering wheel and one about the CG.

*The reason it is NOT about the CG is because it is a resistive force. It's call a resistive force because it resists the FORWARD motion of the vehicle. Its direction of force is parallel to the principal vector of the vehicle, and it's in the opposite direction. Its strength is proportional to the forward speed of the vehicle. It exists only because the vehicle is in motion. It is "owned" by the vehicle.

[Diesel-Lover]

Originally Posted by Cloud Dancer

*The reason it is NOT about the CG is because it is a resistive force. It's call a resistive force because it resists the FORWARD motion of the vehicle. Its direction of force is parallel to the principal vector of the vehicle, and it's in the opposite direction. Its strength is proportional to the forward speed of the vehicle. It exists only because the vehicle is in motion. It is "owned" by the vehicle.

Perhaps if we think of the forces in terms of Vectors. Dunno if there is someone here with one o those design software pkgs, but this blow out and resulting processes could be nicely simulated..


Has any one seen those funky busses with dual steering front axles, now that would be my choice for a mega mega giga giga moving castle eh. If I was one o them Willie Nelson type blokes that would be my choice for a conversion. BTW did ya see the article about WN in the TX monthly mag wow wow https://www.texasmonthly.com/the-cul...-willie-rolls/

[Old Scout]

….this all sounds very scientific with "resistant" forces and vectors, etc--"you lost me at hello".... what I do know is that once you lose control and over correct for a skid, I would prefer to be in a "lower-slung" vehicle with a lower center of gravity, than in a vehicle that is top heavy with a higher CG--not very scientific, I know.
PS--as for crash worthiness--between TVs and cabinets tearing loose, location of passenger in the front cabin with no collapse zones, and varying degrees of construction stds….I don't want to be in a rollover with any RV--period!!!!!

[Cloud Dancer]

The corner of the motorhome (same corner as the failed tire) that "drops" is being incorrectly analyzed. It drops due to the ever-present force of GRAVITY, which is a vertical force. It is NOT a side force. There is NO in-house source of energy that pulls the front of the motorhome to the side. It's a steering action that displaces the failed tire.
In the video, the failed tire moves to the side about 7 inches. At a speed of 88 ft per second, it just takes a very small angle of steering action and less that ONE second to result in a 7 inch displacement.

[Lt Dan]

Thread Closed.

This thread has devolved into speculation and arguments so it's time to move on.

Thank you to all who posted within guidelines.