OT: tipper lorry crash in Bath

Which wouldn't have resulted in loss of braking.

It could have resulted in an unintended application of the brakes and resulted in the lorry coming to a halt on the road and not a reasonably safe lay-by.

Reply to
Peter Hill
Loading thread data ...

It would have resulted in loss of the service brake (footbrake) because its air activated, however the emergency brakes should have kicked in once the tank pressures fell below around 90 psi

Reply to
steve robinson

A few reasons come to mind, overheating brakes causing fade out water in the compressed air system possibly freezing up.

If he had missed a gear attempting to change down on the hill, he would have been in neutral with the engine at tickover as he tried to bring it under control by the service brake. At tickover the compressor may not have been able to keep up with the demand. (AIUI a witness said he was repeatedly pressing the footbrake) In this event, low air pressure may have brought the spring brake into play. But remember the primary function of the spring brake is to prevent driving off from rest without sufficient air. Whether it alone would be able to arrest this vehicle going downhill in neutral fully loaded is doubtful IMHO.

A couple of other slightly related issues.-

Don't many insurance companies insist on a minimum age for drivers of commercial vehicles? ISTR hearing many years ago one of my neighbours couldn't drive his firms escort van because he was only 20.

The entrance to Lansdown lane at the top of the hill has a 6' (except for access) width restriction. There are roads joining further down below the restriction, but these are residential roads, unlikely to have been used in this case, unless he lived there.

Steve

Reply to
shazzbat

That could also just be a restriction of the individual firm.

Reply to
Dave Plowman (News)

steve robinson put finger to keyboard:

I thought the air pressure was required to hold the brakes off. A broken airline would result in brakes locking on.

Reply to
Scion
[...]

AIUI, that only applies to the emergency brake. The service brakes require pressure to apply them.

Chris

Reply to
Chris Whelan

Tht only applies to the emergency brake

Reply to
steve robinson

We've done this one already. The parking brake system works like that but the main brakes use positive pressure to actuate them. I doubt a parking brake is up to stopping a full tipper lorry on a hill.

Tim

Reply to
Tim+

What are you meaning by "emergency brake"? There is no separate "emergency brake" - just the normal air-pressure-released footbrakes. Scion's right. The pressure holds them OFF, and a pressure failure will lock them firmly on.

That doesn't mean they're utterly infallible, of course - mechanical or friction failure would render them useless, but only on one wheel. Unless, of course, other wheels were already not contributing much.

Reply to
Adrian

Did you read the wiki? Okay, Wiki ain't infallible but no one has posted links suggesting that the regular brakes rely on pressure to hold them off, only the parking brake.

formatting link
Tim

Reply to
Tim+

The emergency brake is often refered to as the parking brake, in cars its known as the handbrake, a diaphram in the brake actuators holds back a large spring , usally fitted to the rear breaks or trailer brakes, the front wheels/ stering wheels do not have this system fitted to them.

The service brake/ footbrake operates the brakes by applied air pressure within a secondary chamber within the actuator

both the service brake and the emergency brake operate a pushrod which through a lever rocks a cam which applies the shoes to the drum.

Reply to
steve robinson

Self explanatory, surely?

That's not how air brake systems work. You need to Google it.

He's not.

That only applies to the emergency brake; the service (or 'foot brake') requires air pressure to stop.

Chris

Reply to
Chris Whelan

The lorry is a Scania 8 wheeler, the emergency or parking brake operates on the second and third axles, so effectively half of the total braking available. So it would need quite a lot of failures to reduce emergency stopping power dramatically. The witnesses say that the driver lost control after swerving to avoid an accident, I wonder if he then got the pedals mixed and just stood on the clutch thinking it was the brake and froze in that position, and did not think fast enough to hit the emergency brake (the lever of which has three positions, off, the next a sort of retarder position giving half braking and the final position full park brakes) That vehicle also has an exhaust brake operated by the foot pedal.

Reply to
Mrcheerful

And is fully dual circuit, so even if one tank loses pressure the other will still stop via the footpedal, there are also flashing lights and gongs to warn of low air pressure. There is an air dryer on the compressor circuit to avoid water in the system. If everything falls off at the same time the emrgency brake will still have massive capability as it runs on the two middle axles. I note that one front wheel assembly was torn off, so it must have received a massive impact.

pictures of the truck on the recovery vehicle:

formatting link

Reply to
Mrcheerful
[...]

So driver inexperience may well be a factor then.

Chris

Reply to
Chris Whelan

Tht only applies to the emergency brake

There is no such thing as the emergency brake. All vehicles from cars upwards are required to have a service brake and a parking brake. The service brake, normally referred to as the footbrake, is actuated by the brake pedal and is used for braking of the vehicle in service, ie whilst being driven. The parking brake, normally referred to as the handbrake, is actuated by a hand-operated lever with a facility to lock on in order to prevent the vehicle being set in motion whilst parked.

Various heavy vehicles can also have a variety of auxiliary devices such as exhaust brakes, electric retarders etc. As has already been mentioned, some have a facility for an intermediate position of the parking brake lever to be used as an aux brake, either to use some of the brakes whilst leaving others relatively cold and unfaded, also this means can be used on articulated vehicles to help prevent jack-knifing by means of using the trailer brakes and not the tractor unit brakes, although most artics nowadays have other means of achieving this.

Steve

Reply to
shazzbat

Tim+ put finger to keyboard:

Yeah, I posted without reading the rest of the posts first.

Reply to
Scion

Two arrested on the radio news today, no more details. One post said the initiating event might have been the driver swerving to avoid an accident.

Reply to
newshound

R4 lunchtime had more news.

One 19yo male, named, "believed to be driver". Death by dangerous driving and manslaughter by gross negligence.

One 28yo male, unnamed. Manslaughter.

formatting link

Reply to
Adrian

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.