Recovering from tipover

[carryfast]

Rjan:

Carryfast:

Rjan:
And if you do feel that you’re about to enter a curve at too high a speed (or you’re about to hit adverse camber or mount a kerb), the best pre-primed reaction would be to go for the footbrake immediately, and if possible ease any turn that you have to make.

On the brake, you could well be stopped dead (or at least back well within a comfortable margin) before you even have to make the fatal turn or before the trailer wheels have even hit the uneven surface, and any loss of forward speed will immediately reduce any lateral forces sustained.

As for those who talk of flooring their way out of a rollover, that seems to me like the ravings of a lunatic!

You can brake your way out of trouble so long as it’s all still in a straight line on the approach.But don’t try to do it after you’ve turned in because all the previous forward G forces then get transferred into lateral ones.

Obviously the earlier you catch things the better, and a hard brake application even just milliseconds before a turn, is far better than any fumbling you can manage with the steering once you’re turning.

Also bear in mind, the lateral forces are a product of the forward momentum and the degree of steering input (the vehicle doesn’t move crabwise). Even braking whilst turning, will immediately reduce lateral forces.

As for using power to over come roll it only works if it’s got enough power and it helps if it’s a rear engined rigid but definitely don’t try it with an artic. That thing will,or at least should,also have a full load of water on board.

A rear-engined rigid? Like a passenger bus?

With most automatic transmissions, once the wheels were up you’d be on your side before the gearbox had found the right gear for maximum power.

I’d stick by the principle that the answer to any perceived rollover risk is to brake as hard as necessary at the earliest opportunity. Whatever else you do, your right foot should be on the footbrake.

As I said braking from high speed in the middle of the bend certainly will usually result in a lateral off either in the form of under steer,over steer,or even both ends at once or with a high c of g and/or one of those weird artic things more likely to trip itself up and throw itself over on its side unless you can take off enough lock to straighten it up which is more or less the correct action described by Juddian.

As for the vid as I said ‘enough’ power and the right weight distribution to create mild over steer over roll.While a ‘bus’ might just about manage the weight distribution side but just doesn’t fit the definition of enough power unless you can put a 500 hp + motor in it.While notice the driver rightly applied power in the bend he didn’t dare brake.On that note you won’t make a fire truck test driver.

[rjan]

Carryfast:
As I said braking from high speed in the middle of the bend certainly will usually result in a lateral off either in the form of under steer,over steer,or even both ends at once or with a high c of g and/or one of those weird artic things more likely to trip itself up and throw itself over on its side unless you can take off enough lock to straighten it up which is more or less the correct action described by Juddian.

I don’t see how a braking application can apply an adverse lateral force to a trailer. The lateral force which induces the rollover is either a centrifugal force induced by the turn, or a change in camber, or both.

I agree straightening the vehicle up or steering back into the direction of the roll will always be recommended if possible in addition to braking.

But if you’ve steamed onto the inside of a roundabout, for example, you might not be able to ease the steering without knocking someone out of the way or putting yourself on a collision course with something. Or if you’ve mounted a trief kerb, it’s quite likely to be because someone has hemmed you in.

So I would never say “don’t brake”, because you will buy yourself extra moments to think, and by going slower you ease any lateral forces being imposed - by scrubbing off speed as fast as you can, you may be able to proceed on your pre-planned course, bring things back within safe margins, and render any other tactic irrelevant.

As for the vid as I said ‘enough’ power and the right weight distribution to create mild over steer over roll.While a ‘bus’ might just about manage the weight distribution side but just doesn’t fit the definition of enough power unless you can put a 500 hp + motor in it.While notice the driver rightly applied power in the bend he didn’t dare brake.On that note you won’t make a fire truck test driver.

But without considering whether that is right or wrong, we’re simply not talking about testing a fire truck on a track (a rigid vehicle specially designed to be driven like the clappers and stay upright), where an experienced test driver is mentally prepared and is intentionally taking things to the limit in a safe environment.

We’re talking about what to do in the situation where a driver has made a grave error through inattention or radical misjudgement (or unexpected behaviour of other traffic), and suddenly realises he’s about to roll the vehicle and has one last throw of the dice to avoid catastrophe. I say hit the brakes all the way.

[carryfast]

Rjan:

Carryfast:
As I said braking from high speed in the middle of the bend certainly will usually result in a lateral off either in the form of under steer,over steer,or even both ends at once or with a high c of g and/or one of those weird artic things more likely to trip itself up and throw itself over on its side unless you can take off enough lock to straighten it up which is more or less the correct action described by Juddian.

I don’t see how a braking application can apply an adverse lateral force to a trailer. The lateral force which induces the rollover is either a centrifugal force induced by the turn, or a change in camber, or both.

I agree straightening the vehicle up or steering back into the direction of the roll will always be recommended if possible in addition to braking.

But if you’ve steamed onto the inside of a roundabout, for example, you might not be able to ease the steering without knocking someone out of the way or putting yourself on a collision course with something. Or if you’ve mounted a trief kerb, it’s quite likely to be because someone has hemmed you in.

So I would never say “don’t brake”, because you will buy yourself extra moments to think, and by going slower you ease any lateral forces being imposed - by scrubbing off speed as fast as you can, you may be able to proceed on your pre-planned course, bring things back within safe margins, and render any other tactic irrelevant.

As for the vid as I said ‘enough’ power and the right weight distribution to create mild over steer over roll.While a ‘bus’ might just about manage the weight distribution side but just doesn’t fit the definition of enough power unless you can put a 500 hp + motor in it.While notice the driver rightly applied power in the bend he didn’t dare brake.On that note you won’t make a fire truck test driver.

But without considering whether that is right or wrong, we’re simply not talking about testing a fire truck on a track (a rigid vehicle specially designed to be driven like the clappers and stay upright), where an experienced test driver is mentally prepared and is intentionally taking things to the limit in a safe environment.

We’re talking about what to do in the situation where a driver has made a grave error through inattention or radical misjudgement (or unexpected behaviour of other traffic), and suddenly realises he’s about to roll the vehicle and has one last throw of the dice to avoid catastrophe. I say hit the brakes all the way.

Firstly the fire truck vid was only meant as an example as to how applying power can and does work.But obviously not in the case of the average commercial vehicle which was the point.

However not braking after turning into a bend and especially if the entry has been over cooked generally applies regardless.While in the case of an artic trailer it’s effectively just a big rigid vehicle steered by the tractor unit’s drive axle at the end of the day.But with the downside that the more lock that’s applied the less support it has at whichever corner of the front end is on the outside of the bend.At which point the handling characteristics become like a three wheeler car but on a much bigger scale and let alone if it’s also combined with a high c of g.Which just magnifies the effect I described of the forward momentum being turned into lateral force most likely roll in this case.Because 1 the thing just doesn’t want to go where the steering wheels are pointing and 2 that lateral force conversion obviously takes place and is applied before you can shed the speed with the brakes and 3 an artic doesn’t have the same amount of support at it’s front end when it’s turning with the drive axle at an angle to the trailer as a rigid does.While c of g is king regardless in that a high c of g will just as happily throw a rigid on its side as an artic at virtually any speed in which case trying to ease off the steering is better than panic braking in the middle of a bend.In addition to making sure not to go from one lock to the other without pausing at the straight ahead position.

[ezydriver]

I think I’ll just drive extra steady.

[drempels]

Carryfast:

Rjan:

Carryfast:
As I said braking from high speed in the middle of the bend certainly will usually result in a lateral off either in the form of under steer,over steer,or even both ends at once or with a high c of g and/or one of those weird artic things more likely to trip itself up and throw itself over on its side unless you can take off enough lock to straighten it up which is more or less the correct action described by Juddian.

I don’t see how a braking application can apply an adverse lateral force to a trailer. The lateral force which induces the rollover is either a centrifugal force induced by the turn, or a change in camber, or both.

I agree straightening the vehicle up or steering back into the direction of the roll will always be recommended if possible in addition to braking.

But if you’ve steamed onto the inside of a roundabout, for example, you might not be able to ease the steering without knocking someone out of the way or putting yourself on a collision course with something. Or if you’ve mounted a trief kerb, it’s quite likely to be because someone has hemmed you in.

So I would never say “don’t brake”, because you will buy yourself extra moments to think, and by going slower you ease any lateral forces being imposed - by scrubbing off speed as fast as you can, you may be able to proceed on your pre-planned course, bring things back within safe margins, and render any other tactic irrelevant.

As for the vid as I said ‘enough’ power and the right weight distribution to create mild over steer over roll.While a ‘bus’ might just about manage the weight distribution side but just doesn’t fit the definition of enough power unless you can put a 500 hp + motor in it.While notice the driver rightly applied power in the bend he didn’t dare brake.On that note you won’t make a fire truck test driver.

But without considering whether that is right or wrong, we’re simply not talking about testing a fire truck on a track (a rigid vehicle specially designed to be driven like the clappers and stay upright), where an experienced test driver is mentally prepared and is intentionally taking things to the limit in a safe environment.

We’re talking about what to do in the situation where a driver has made a grave error through inattention or radical misjudgement (or unexpected behaviour of other traffic), and suddenly realises he’s about to roll the vehicle and has one last throw of the dice to avoid catastrophe. I say hit the brakes all the way.

Firstly the fire truck vid was only meant as an example as to how applying power can and does work.But obviously not in the case of the average commercial vehicle which was the point.

However not braking after turning into a bend and especially if the entry has been over cooked generally applies regardless.While in the case of an artic trailer it’s effectively just a big rigid vehicle steered by the tractor unit’s drive axle at the end of the day.But with the downside that the more lock that’s applied the less support it has at whichever corner of the front end is on the outside of the bend.At which point the handling characteristics become like a three wheeler car but on a much bigger scale and let alone if it’s also combined with a high c of g.Which just magnifies the effect I described of the forward momentum being turned into lateral force most likely roll in this case.Because 1 the thing just doesn’t want to go where the steering wheels are pointing and 2 that lateral force conversion obviously takes place and is applied before you can shed the speed with the brakes and 3 an artic doesn’t have the same amount of support at it’s front end when it’s turning with the drive axle at an angle to the trailer as a rigid does.While c of g is king regardless in that a high c of g will just as happily throw a rigid on its side as an artic at virtually any speed in which case trying to ease off the steering is better than panic braking in the middle of a bend.In addition to making sure not to go from one lock to the other without pausing at the straight ahead position.

Have you more experience of artics or 3-wheelers?