Tipper crash in Bath

Commuting, Day rides, Audax, Incidents, etc.
User avatar
DaveP
Posts: 3227
Joined: 9 Mar 2007, 4:20pm
Location: W Mids

Re: Tipper crash in Bath

Postby DaveP » 15 Feb 2015, 5:34pm

I think its more likely to be simply because its a small engine. Accelerates well with the help of a turbo, but on overrun there's no turbo assistance. I have been told that the reason for preferring slowing on the brakes these days is because it uses less fuel and produces less pollution.

A couple more technical points: Trucks have something more than the engine braking that car drivers might experience. It's variously called the retarder or the exhaust brake - a metal flap in the exhaust manifold swings into place and almost completely blocks the exhaust. At the instant this happens the fuel supply is cut off and the work of compressing air and forcing it through the exhaust has a braking effect that can help avoid overheating the brakes on a long descent. It often only works on the top couple of gears. You can't do this on cars and vans because the engines just aren't built strongly enough to survive the pressures.
Its been a while since I've used a truck with a crawler gear but the ones I saw were a super low gear, non synchromesh and quite difficult to get into if moving. More for steep ascents really. Automatic trucks have a crawler (snail actually!) setting, but that is strictly for manoeuvring. You have to be briefly stationary to be able to select it.

I was shocked by his age too - when I took my class2 you had to be 21 even for 7.5 tonnes, so I looked it up. Today, as long as you successfully complete a New Driver CPC first you can hold an LGV provisional from your 18th birthday. Personally I feel that some practical experience of driving would be appropriate too, but the law doesn't. A loaded tipper is a bit of a beast to cut your teeth on.
I feel as much sympathy for those who have perished, and their friends and families as anyone. I also feel a deal of sympathy for the young truck driver. He and his family have invested a lot of time and money to get him his licence, and at the time of writing there is no reason to believe that he has done anything outrageous. Something went horribly wrong and he didn't have much experience to help him cope (but then he wasn't required to have that experience). I see a young man who has worked hard towards a goal and now sees his dreams in ruins. I imagine it'll be a while before he can sleep without "assistance".
Trying to retain enough fitness to grow old disgracefully...

User avatar
bigjim
Posts: 3138
Joined: 2 Feb 2008, 5:08pm
Location: Manchester

Re: Tipper crash in Bath

Postby bigjim » 15 Feb 2015, 6:42pm

Dave. That truck will have had a rangechange or splitaxle so in High the crawler would be more than walking pace. Even so going down the box would have been sufficient to hold the weight to a manageable level.
Nothing left to prove.

User avatar
661-Pete
Posts: 9749
Joined: 22 Nov 2012, 8:45pm
Location: Sussex

Re: Tipper crash in Bath

Postby 661-Pete » 15 Feb 2015, 8:52pm

Regarding the engine braking issue, how do you explain this sign? It's on a French Autoroute which I'm very familiar with, we often drive along this stretch and there are several signs like this one, giving out the message in German/Spanish as well as English/French. In my car I don't really need to bother since the slope is very gentle, but does it indicate that the French traffic authorities are out of touch with the rest of the world?

Somehow, I think not. However, for a car towing a caravan, or an artic with a trailer, using brakes in this situation is obviously a lot safer than engine braking: I'll grant you that.
Suppose that this room is a lift. The support breaks and down we go with ever-increasing velocity.
Let us pass the time by performing physical experiments...
--- Arthur Eddington (creator of the Eddington Number).

User avatar
bigjim
Posts: 3138
Joined: 2 Feb 2008, 5:08pm
Location: Manchester

Re: Tipper crash in Bath

Postby bigjim » 15 Feb 2015, 9:31pm

Somehow, I think not. However, for a car towing a caravan, or an artic with a trailer, using brakes in this situation is obviously a lot safer than engine braking: I'll grant you that.

No it's not! That looks like the start of a long steep stretch of road. Imagine you have 40 ton behind you. The more you travel downhill the more that load will push you. You will have brake fade. So now you are going too fast and cannot downshift because you cannot get the engine revs, road speed to match. Now you are out of control!
Truckdrivers should be aware of this caravanners less so. The French are correct. Steep roads in the Uk used to have emergency run offs for this.
Last edited by bigjim on 15 Feb 2015, 9:49pm, edited 1 time in total.
Nothing left to prove.

LollyKat
Posts: 2935
Joined: 28 May 2011, 11:25pm
Location: Scotland

Re: Tipper crash in Bath

Postby LollyKat » 15 Feb 2015, 9:32pm

IME engine braking doesn't work as well on modern cars as it does on older ones. In town near me is quite a long, quite steep (?10%) hill, the top approached from a junction. Going down it in our 1993 Volvo 240 estate - a heavy car - I can keep to the 30 limit just by staying in 3rd gear and coasting, no brakes required.

A few years ago, though, I drove down it in my son's Ford Focus. The speedometer wasn't working but I stayed in 3rd gear as usual. Half-way down I thought it felt rather fast and applied the brakes....as I did so a policeman with a speed gun jumped out :shock: . I was really cross with myself and in a sweat for a fortnight, but they must have given me the benefit of the doubt, and I retained my unblemished record.

A couple of driving instructors I know confirmed that modern cars don't behave the same as older ones (duh!)

User avatar
661-Pete
Posts: 9749
Joined: 22 Nov 2012, 8:45pm
Location: Sussex

Re: Tipper crash in Bath

Postby 661-Pete » 15 Feb 2015, 10:56pm

bigjim wrote:No it's not! That looks like the start of a long steep stretch of road. Imagine you have 40 ton behind you. The more you travel downhill the more that load will push you. You will have brake fade. So now you are going too fast and cannot downshift because you cannot get the engine revs, road speed to match. Now you are out of control!
Truckdrivers should be aware of this caravanners less so. The French are correct. Steep roads in the Uk used to have emergency run offs for this.

But with an artic truck or a caravan, indeed any sort of trailer, there is no drive to the trailer. Hence there cannot be any engine braking to its wheels. If you rely entirely on engine braking, you are in effect applying resistive force to the front part of the vehicle only, in front of the coupling to the trailer. This can't be ideal!

I have never driven this kind of vehicle, but I would have to assume that in modern trucks etc. there are anti-fade measures on the brakes, which I also assume to act on all wheels equally.

I wonder whether another reason for the change in emphasis away from engine braking, is because so many cars are front-wheel drive nowadays? Once again, my old banger (first car) was indisputably RWD, as were the majority of cars in those days (Minis and the like excepted).

Incidentally it's not a steep stretch of road in my Streetview grab - it's a motorway with a gradient of just 5% (1 in 20). A steep hill on a motorway would be an alarming prospect, to say the least!
Suppose that this room is a lift. The support breaks and down we go with ever-increasing velocity.
Let us pass the time by performing physical experiments...
--- Arthur Eddington (creator of the Eddington Number).

User avatar
Mick F
Spambuster
Posts: 48178
Joined: 7 Jan 2007, 11:24am
Location: Tamar Valley, Cornwall

Re: Tipper crash in Bath

Postby Mick F » 16 Feb 2015, 9:26am

DaveP wrote:I think its more likely to be simply because its a small engine.
No, not in my experience.
I've diven enough small engined cars in my time, and the Fiat 500 Twinair is very very different.
LollyKat wrote:IME engine braking doesn't work as well on modern cars as it does on older ones.
Yep. Agree.
I think it might have something to do with variable valve timings and stuff??

Our Fiat's (eight - four per cylinder) valves are actuated by hydraulics controlled by computer. Lift your foot off the throttle (even the throttle pedal is connected to the computer), and the car just coasts along in gear with little or no resistance from the engine - how, I'm not sure, but it's excellent for fuel conservation.

As for HGVs, engine braking is paramount.

Living on the side of a steep valley, we see and hear all the lorries coming down into the village. Them coming down on just the brakes fills me with dread, as there's nothing to stop them running into all the other vehicles at the traffic lights or the people crossing the road if their brakes had faded. :shock:

Two miles from the top to the bottom! :shock:
Mick F. Cornwall

User avatar
bigjim
Posts: 3138
Joined: 2 Feb 2008, 5:08pm
Location: Manchester

Re: Tipper crash in Bath

Postby bigjim » 16 Feb 2015, 9:44am

But with an artic truck or a caravan, indeed any sort of trailer, there is no drive to the trailer. Hence there cannot be any engine braking to its wheels. If you rely entirely on engine braking, you are in effect applying resistive force to the front part of the vehicle only, in front of the coupling to the trailer. This can't be ideal!

I doubt there is an ideal. But thats how it is. You slow the Unit and the trailer is not going anywhere. There is considerable weight in the unit and usually more wheels on the road. Engine brake is the priority.

As to steep hills on motorways. Well yes, not steep in a nice car, but when you have 40 tons pushing you downhill for a long stretch, miles at a time, then it becomes a different matter.
Nothing left to prove.

User avatar
[XAP]Bob
Posts: 17178
Joined: 26 Sep 2008, 4:12pm

Re: Tipper crash in Bath

Postby [XAP]Bob » 16 Feb 2015, 9:47am

661-Pete wrote:
bigjim wrote:No it's not! That looks like the start of a long steep stretch of road. Imagine you have 40 ton behind you. The more you travel downhill the more that load will push you. You will have brake fade. So now you are going too fast and cannot downshift because you cannot get the engine revs, road speed to match. Now you are out of control!
Truckdrivers should be aware of this caravanners less so. The French are correct. Steep roads in the Uk used to have emergency run offs for this.

But with an artic truck or a caravan, indeed any sort of trailer, there is no drive to the trailer. Hence there cannot be any engine braking to its wheels. If you rely entirely on engine braking, you are in effect applying resistive force to the front part of the vehicle only, in front of the coupling to the trailer. This can't be ideal!


Larger domestic trailers have braking which will kick in on that - as the car is slowing the pressure on the tow hitch controls the brakes on the trailer - when you start pulling there is obviously no overrun pressure.
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.

User avatar
squeaker
Posts: 3588
Joined: 12 Jan 2007, 11:43pm
Location: Sussex

Re: Tipper crash in Bath

Postby squeaker » 16 Feb 2015, 10:28am

Mick F wrote:Our Fiat's (eight - four per cylinder) valves are actuated by hydraulics controlled by computer. Lift your foot off the throttle (even the throttle pedal is connected to the computer), and the car just coasts along in gear with little or no resistance from the engine - how, I'm not sure, but it's excellent for fuel conservation.

Suspect you are on the right lines there, Mick.
IF 'throttle pedal up' THEN 'do not open valves' would be a good way of minimising pumping losses in the engine (the work done pulling air into the cylinders and exhausting it).

Edit - Just looked up Multi-air: only the inlet valve opening is modulated.
Last edited by squeaker on 17 Feb 2015, 1:59pm, edited 1 time in total.
"42"

User avatar
hondated
Posts: 2388
Joined: 27 Mar 2008, 7:59am
Location: Eastbourne

Re: Tipper crash in Bath

Postby hondated » 16 Feb 2015, 2:41pm

DaveP wrote:
I was shocked by his age too - when I took my class2 you had to be 21 even for 7.5 tonnes, so I looked it up. Today, as long as you successfully complete a New Driver CPC first you can hold an LGV provisional from your 18th birthday. Personally I feel that some practical experience of driving would be appropriate too, but the law doesn't. A loaded tipper is a bit of a beast to cut your teeth on.

Dave just to agree and add to your point years ago now at 21 I passed my Class 2 HGV and drove various lorries for a while many of which were Tippers. Anyway I later got a job with the Gas Board and after some time they decided that they needed Butane Plants to back up the gas mains system for when we have bad Winters to back up the gas mains system. So part of the process was to buy artic tankers to transport the Butane Gas.
As a consequence of that they put me through an HGV course and I got my Class 1 licence. They then sent me on a tanker conversion driving course with Smith and Robinson up North in Rothwell.
Now I had been driving lorries for some years by this time so I couldn't see that being too much of a problem, but boy was I wrong.

I first realise how different driving a tanker was when I was asked to turn right on an hill. After waiting for oncoming traffic to pass I then went to make the turn and the cab started to bounce because I had not given it enough throttle as the load was now on the tail end. Lesson learnt there.
I also learnt that with a fluid load the cornering and braking. even though it had baffles in the tank altered the vehicles characteristics loaded entirely.
So given I at least had some experience and I still made mistakes it must have been even more difficult for this young lad.

thirdcrank
Posts: 28687
Joined: 9 Jan 2007, 2:44pm

Re: Tipper crash in Bath

Postby thirdcrank » 16 Feb 2015, 2:46pm

In a probably vain attempt to relate this discussion about driving techniques for motor cars to a crash involving a runaway 32 tonne truck, I'll quote this from Vorpal's link to the Daily Mail
Mr Browne, who lives yards away on the steep residential road where the tragedy unfolded, said the driver claimed he had been following his boss down the hill.

(Read more: http://www.dailymail.co.uk/news/article ... z3Rv1aH4TI Follow us: @MailOnline on Twitter | DailyMail on Facebook)

If that's right, it would be interesting to know what type of vehicle he was following ie was it another tipper or a lighter vehicle such as a car? It raises other issues, like the difficulty of following another vehicle and keeping up with it.

Vorpal
Moderator
Posts: 17908
Joined: 19 Jan 2009, 3:34pm
Location: Not there ;)

Re: Tipper crash in Bath

Postby Vorpal » 16 Feb 2015, 2:49pm

thirdcrank wrote:In a probably vain attempt to relate this discussion about driving techniques for motor cars to a crash involving a runaway 32 tonne truck, I'll quote this from Vorpal's link to the Daily Mail
Mr Browne, who lives yards away on the steep residential road where the tragedy unfolded, said the driver claimed he had been following his boss down the hill.

(Read more: http://www.dailymail.co.uk/news/article ... z3Rv1aH4TI Follow us: @MailOnline on Twitter | DailyMail on Facebook)

If that's right, it would be interesting to know what type of vehicle he was following ie was it another tipper or a lighter vehicle such as a car? It raises other issues, like the difficulty of following another vehicle and keeping up with it.

And why his boss would deliberately lead him someplace that seems to have been unsuitable for the vehicle, unless it was bound for the construction site, there.
“In some ways, it is easier to be a dissident, for then one is without responsibility.”
― Nelson Mandela, Long Walk to Freedom

Vorpal
Moderator
Posts: 17908
Joined: 19 Jan 2009, 3:34pm
Location: Not there ;)

Re: Tipper crash in Bath

Postby Vorpal » 16 Feb 2015, 3:00pm

DaveP wrote:I was shocked by his age too - when I took my class2 you had to be 21 even for 7.5 tonnes, so I looked it up. Today, as long as you successfully complete a New Driver CPC first you can hold an LGV provisional from your 18th birthday. Personally I feel that some practical experience of driving would be appropriate too, but the law doesn't. A loaded tipper is a bit of a beast to cut your teeth on.

Some of the farm vehicles he may have experience driving can quite tricky to drive when loaded (e.g. a combine harvester full of corn, a 400 hp tractor pulling a slurry tanker, or a sprayer). The rules about trailer brakes are more relaxed on farm equipment, and they can be quite easy to jack knife. His age doesn't necessarily mean he doesn't have experience driving equipment that is difficult to manage.
“In some ways, it is easier to be a dissident, for then one is without responsibility.”
― Nelson Mandela, Long Walk to Freedom

User avatar
mjr
Posts: 14981
Joined: 20 Jun 2011, 7:06pm
Location: Norfolk or Somerset, mostly
Contact:

Re: Tipper crash in Bath

Postby mjr » 16 Feb 2015, 3:37pm

Mick F wrote:We have a Fiat 500. Two cylinders, 875cc Turbo. Goes like a rocket!
One thing I've found when driving it, there is little or no engine braking available. We live on the side of a steep valley and we need to brake far more than we ever did in other cars.

This is not limited to small engines. Our 1.4l (Alfa Romeo, so another Fiat group company) has little engine braking. The flipside is that the engine seems far easier to stop and start (which it does automatically in the increasingly common queues), including when accelerating. As Mick writes, it's excellent for fuel economy.

One point not yet covered here is: why do we still let heavy vehicles deliver to/near schools or drive past them (if avoidable) when there are large numbers of children entering/exiting?
MJR, mostly pedalling 3-speed roadsters. KL+West Norfolk BUG incl social easy rides http://www.klwnbug.co.uk
All the above is CC-By-SA and no other implied copyright license to Cycle magazine.