Curious re: Lorry and speed camera.

Justintime · 3 Dec 2010 at 20:04

To put it into a nutshell : Coming home, North circular, Semi lorry in the outside lane doing well over 60 in a 50 (heh, he ripped past me while i was doing 57

i also thought they were limited to 56mph?).
Obviously he did not know the area and blew past a gatso. Got flashed, but to me the trailer end of it is what got the brunt of the flash, the rear end cleared after the second flash so no pic of that, is the plate on the tractor visible to the camera or do they usually get away with it?

Not a fan of cameras but i think this was was deserved as he tailgated a few people and forced them inside plus the road wasn't all that wide in that area, just basically a big bully.

Clarkey · 3 Dec 2010 at 20:15

Probably a foreign truck if it was unlimited, in which case they will get away with it regardless.

icyshore · 3 Dec 2010 at 20:18

He should have a number plate on the trailer anyway, so it might still get back to him.

Rich1988 · 4 Dec 2010 at 00:31

the trucks throttle limited to either 52, 54 or 56 mph however they are physically limited at 60mph, meaning they can only get to either 52,54 or 56mph under their own steam but can get up to 60mph on a downhill stretch, also 56 on your speedo will be about 50mph real speed.

Clarkey · 4 Dec 2010 at 00:41

Rich1988 said:
the trucks throttle limited to either 52, 54 or 56 mph however they are physically limited at 60mph, meaning they can only get to either 52,54 or 56mph under their own steam but can get up to 60mph on a downhill stretch, also 56 on your speedo will be about 50mph real speed.

Physically limited in what way, puts on the brakes when you hit 60?

Rich1988 · 4 Dec 2010 at 00:57

yea the brakes are applied automatically, its why if you look youll notice lorries braking on hills not because they are doing it but because of the limiters

[TW]Fox · 4 Dec 2010 at 01:03

Rich1988 said:
yea the brakes are applied automatically

Really?

Because limiters have been around for ages yet it's only reasonable recently that cars with cruise control have also had the ability to apply the brake if the speed creeps above the predefined setting. I would therefore be suprised if trucks have had this feature for many years..

Rich1988 · 4 Dec 2010 at 01:10

not sure i said many years anywhere? I spoke to a lorry driver on the m25 when traffic was at a standstill in the summer and he told me thats what his truck did

Sin_Chase · 4 Dec 2010 at 02:24

I would never get in any vehicle which arbitrarily and automatically applied its brakes to limit the speed.

InvaderGIR · 4 Dec 2010 at 02:31

Certainly followed many lorries in the past years where they have had their brake lights come on when going down hill at ~56mph. I agree with gingerboy!

tigerstyle · 4 Dec 2010 at 03:11

Sin_Chase said:
I would never get in any vehicle which arbitrarily and automatically applied its brakes to limit the speed.

Apart from the obvious fact that the trucks brakes work completely nothing like that? They come on above 60, not 'arbitrarily' :confused:

No one just happens to find themselves at 60mph in a truck, it will take time and a long time on the gas pedal to reach that speed.

Justintime · 4 Dec 2010 at 04:04

Rich1988 said:
also 56 on your speedo will be about 50mph real speed.

56 on my speedo is about 55mph GPS, i never had a car that was that far off the mark, usually only 2-3mph tops at such a low speed.

atpbx · 4 Dec 2010 at 09:19

[TW]Fox;17927448 said:
Really?

Because limiters have been around for ages yet it's only reasonable recently that cars with cruise control have also had the ability to apply the brake if the speed creeps above the predefined setting. I would therefore be suprised if trucks have had this feature for many years..

No not really, it just cuts the power until the speed drops below the limiter setting.
You can free wheel down hill to any speed mavity and the engine breaking will let you in a lorry (because they still rev as if you are doing 56mph and in top gear).

atpbx · 4 Dec 2010 at 09:22

thepedster said:
Apart from the obvious fact that the trucks brakes work completely nothing like that? They come on above 60, not 'arbitrarily' No one just happens to find themselves at 60mph in a truck, it will take time and a long time on the gas pedal to reach that speed.

The limiter doesnt work the brakes.
Its an engine speed limiter.

atpbx · 4 Dec 2010 at 09:24

InvaderGIR said:
Certainly followed many lorries in the past years where they have had their brake lights come on when going down hill at ~56mph. I agree with gingerboy!

Thats the driver, if the lorry is effectively free wheeling because the limiter has cut the power, you are not building any air pressure, every time you use the brakes, you loose some of your air reserve.

mattyprice4004 · 4 Dec 2010 at 09:40

Surely the engine will still be turning over, thus making air pressure? :confused:

atpbx · 4 Dec 2010 at 10:06

mattyprice4004 said:
Surely the engine will still be turning over, thus making air pressure?

Kind of.

Its dependant on engine speed, what else is being asked of the supply etc etc.

For instance, I was in a seven and half the other week and was driving around the wolds, that even though I was maintaining engine speed, couldnt generate enough Air to work the clutch at all and the brakes effectively when going down hill.

tigerstyle · 4 Dec 2010 at 10:41

atpbx said:
Kind of.

Its dependant on engine speed, what else is being asked of the supply etc etc.

For instance, I was in a seven and half the other week and was driving around the wolds, that even though I was maintaining engine speed, couldnt generate enough Air to work the clutch at all and the brakes effectively when going down hill.

not a faulty truck then?

Atom · 4 Dec 2010 at 10:53

atpbx said:
Kind of.

Its dependant on engine speed, what else is being asked of the supply etc etc.

For instance, I was in a seven and half the other week and was driving around the wolds, that even though I was maintaining engine speed, couldnt generate enough Air to work the clutch at all and the brakes effectively when going down hill.

Something wrong with it then.. The air in a truck holds the brakes off until you press the brake pedal. Some air pressure is released and the brakes start to come on. more you brake more air is released..

Trucks are not limited to 60mph. It will do whatever spped you let it down hill until you apply either the foot brake or exhaust brake.. Even on idle the brake compressor is working building pressure and at revs it should be able to produce more than enough even under heavy braking..

Jonnycoupe · 4 Dec 2010 at 10:58

[TW]Fox;17927448 said:
Really?

Because limiters have been around for ages yet it's only reasonable recently that cars with cruise control have also had the ability to apply the brake if the speed creeps above the predefined setting. I would therefore be suprised if trucks have had this feature for many years..

Why?

The whole of a truck system is based on air actuation rather a very simple hydrualic system, cruise brake is only really a feature from safety legislation I guess as fundamentally its no different to EBD or ASC.

I have no idea if trucks will brake, but it may be a more recent requirement. That said I wish they would do more, say 65, its half the reason the traffic flows so much better in France.