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Effluent Man
11th Apr 2014, 10:19
Driving from East Kent to Suffolk in the early hours in a car with a digital fuel read out.I was doing a steady 55-60 and the readout showed 55.4mpg.A Norbert Dentressangle juggernaut entered from a slip road.I tucked in behind him and the gauge went up to 67.2mpg,same speed.I dropped back and it returned to 55,moved into the slipstram again..67.
So,where does the extra MPG come from.Science tells me it can't come from nowhere so logically pulling back into Norbert's slipstream must take it from him by dirtying his vortex? Opinions?

500N
11th Apr 2014, 10:26
Depending on how far back you are, the truck pulls the car along so the car engine isn't working so hard.

I have tried it, up close behind a truck and the car does stay at the same speed and if you take your foot off the accelerator you don't slow down quite as quick.

barry lloyd
11th Apr 2014, 10:32
up close behind a truck :eek:

Really - so you can't be seen in the mirrors?

angels
11th Apr 2014, 11:08
He is pulling you along. He's creating lower air pressure behind him as he punches a hole in the air and your car is being sucked into it. Whatever happens, he will be punching the hole in the air, so you aren't slowing him down per se.

This the first time I've ever attempted to answer an engineering question on JB, so no doubt I will be proved wrong very shortly. :}

Lon More
11th Apr 2014, 11:25
If this is being effective you're way too close to the truck for your own safety if he brakes suddenly

http://www.mrcorfe.com/KS4/Edexcel/Physics/P2-9-AsFastAsYouCan/images/2SecRule.gif

If a cop sees in the UK it you can expect an on-the-spot fine for tailgating (http://money.uk.msn.com/news/on-the-spot-fines-for-tailgating-2) which will cancel out any potenntial saving for quite a while

rh200
11th Apr 2014, 11:31
Really - so you can't be seen in the mirrors?

Slipstreaming is natural, birds do it, cyclists do it and truckies do it. Though on the road it is illigal and dangrous.

Its not just a suction thing, it breaks up the air so you don't get the effective head wind.

The most pronouced of this is the Nullabour plains where you can get several truckies going east west all up each others @rse. Its all well and good until something goes wrong up front.

ShyTorque
11th Apr 2014, 11:39
The self righteous brigade were soon on the scene!

The worst group for tailgating are the truckers themselves.

I don't condone doing it either but you are riding on the "positive side" of the vortices created by the truck.

cattletruck
11th Apr 2014, 11:47
Just fit magnets to one side of your car and drive in the slow lane this way you get an influential tug along by the faster moving cars.

alisoncc
11th Apr 2014, 11:48
It is even more fun if you can do it in a small Piper up behind a 747 or A380. :ok:

Lon More
11th Apr 2014, 11:49
Shyttorque wrote The self righteous brigade were soon on the scene

Presumably directed at me.
You've obviously never been rear-ended (or were you in the navy?)

Truckers do it all the time; I'm not defending them.

They can't overtake, all on the limiter - and on many roads it's forbidden leading to a train of some 15-20 trucks.

Leave a 2 second gap and some numpty is going to dive into it, guaranteed, endangering everybody

Lon More
11th Apr 2014, 11:56
It is even more fun if you can do it in a small Piper up behind a 747 or 380

But only if it's cleared for aerobatics :p

Shaggy Sheep Driver
11th Apr 2014, 12:09
The most pronouced of this is the Nullabour plains where you can get several truckies going east west all up each others @rse. Its all well and good until something goes wrong up front.

So why not mechanically couple them together then only the front one needs an engine and driver. And to ensure they are guided, and to vastly reduce the rolling resistance and therefore reduce fuel consumption, run them on steel wheels on steel rails. You could transport 100 containers at a time that way, in perfect safety and much more cheaply!

A vehicle, an engine, and a driver for each container, running on energy-absorbing pneumatic tyres? It'll never catch on!

panda-k-bear
11th Apr 2014, 12:10
The most pronouced of this is the Nullabour plains where you can get several truckies going east west all up each others @rse. Its all well and good until something goes wrong up front.

Just to develop this concept further, what you could do to prevent accidents to fit each vehicle with spring-loaded plates front and rear so that if they were to hit each other, the damage would be minimised. We could call them oooh, I don't know something like 'buffers'.

If we were to link those juggernauts together somehow, you wouldn't need a cab and driver with each lorry, would you? You could connect only the trailers together, with one single vehicle with a large motor being located at the head of the ... erm.... train of wagons.

Just think how much fuel could be saved.

I wonder if it would be possible to somehow make it that you'd no longer have to dawdle in your car behind great trains of lorries that are all taking the same two-lane road, like the A1 or the A14 for example? Any ideas anyone? :}

panda-k-bear
11th Apr 2014, 12:11
SSD - snap!

ShyTorque
11th Apr 2014, 12:31
"Lonmmore",

As is often the case here, someone asks a question, on science in this case, and someone lurking in the wings immediately jumps out and tries to "get one over" on the poster and belittle them, rather than take part in the thread as intended. It stifles debate.

No, I was never in the Navy and even so I will not allow anyone to tailgate my vehicle. My in laws were severely injured when an HGV hit them from behind and totally destroyed their car, also propelling them into the path of other traffic, which did thankfully manage to stop in time. The HGV was unable to stop because he didn't leave sufficient room in front bearing in mind the prevailing conditions.

I fully understand why truck drivers try to maintain their road speed, but not if it is at the expense of safety of other road users. Most HGV tailgating I've seen occurs where overtaking is allowed, such as on motorways. That said, some HGV drivers do obviously think they have a right to exceed the relevant 40 mph limit on single carriageways and to attempt ot "push" other drivers along! Obviously, any error by an HGV driver is likely to have far more serious consequences than a car running up the back of his truck by someone silly enough to tailgate him. I've been unfortunate enough to have seen what happens first hand on more than one occasion. We had to attend and take photos and video footage of a fatal accident where five people in an estate car were crushed flat by an HGV (up against the rear of a container lorry) when its driver failed keep his distance as traffic slowed to a standstill on the A1. All the other traffic stopped, except him and the result was extreme. Another accident we attended, was again caused by an HGV driver, who drove his fully laden car transporter into the back of a slow vehicle on a dual carriageway - it was in the slow lane with orange flashing hazard beacons on it. The other driver was thrown from his vehicle and run over by it.

Apologies to the OP for maintaining thread drift. However, I did attempt to answer the question. :)

chuks
11th Apr 2014, 12:40
Exactly this is in the works, "drafting" performed by automated vehicles, a train of uncoupled artics running very close together but "talking" to one another by some sort of short-range radio link, perhaps "Bluetooth." They would have radar to keep the distance, along with automated braking.

It's a brilliant idea, except that it leaves out the notion of the first vehicle having a crash that makes it stop real short, perhaps a head-on collision. Then the whole train would crash.

The odd thing is, it's win-win, because two vehicles close together have an increased "fineness ratio," which creates less drag. This is why you see those NASCAR boys running nose-to-tail without the leader trying to shake off the follower, until he wants to do that

On the other hand, it's extremely unsafe. I often see fellow motorcyclists doing this on the German Autobahn at 100 km/h., right up the chuff of a big lorry. All it would take is for the lorry to brake and then the bike, usually a small one, would go right up underneath it, as does happen here. On the other hand, you do get a nice ride, especially in winter, in the warm draft of the big lorry.

TBirdFrank
11th Apr 2014, 12:47
SSD - A lovely idea, but cn you imagine a set of rails into every customer's premises and along every street, and just imagine the marshalling yards and break bulk depots.

Its why the road haulage industry will always murder the rail industry for short haul and small haul.

I rember Roger Bailey one time lecturing on rail freight and pointing out that in the good old days the average speed of a consignment from despatch to customer was 7mph.

Can't see Amazon, Argos, etc buying that today!

Coal, Steel and Stone were always the stuff that sat happiest on rail. Today even the rail industry is bandoning itself for haulage - fuel to depots and rolling stock for repairs!

(written on a Bendyleano coasting down to Carlisle at circa the ton! - that's what we do best now)

goldfrog
11th Apr 2014, 13:17
If a cop sees in the UK it you can expect an on-the-spot fine for tailgating (http://money.uk.msn.com/news/on-the-spot-fines-for-tailgating-2) which will cancel out any potenntial saving for quite a while

No such things as 'on-the-spot fine' in the UK, you can be issued with a Conditional Offer of a Fixed Penalty which you can reject and go to court if you wish!

Lon More
11th Apr 2014, 14:16
Goldfrog wrote:
No such things as 'on-the-spot fine' in the UK
On the spot fines introduced (http://news.uk.msn.com/uk/on-the-spot-fines-for-tailgating)last year

RAC/OPS
11th Apr 2014, 14:41
On the spot fines introduced last year

Still not "on the spot" as in some countries in mainland Europe where you have to pay the cop who pulls you over. Spain, for instance.

May be wrong...

Dak Man
11th Apr 2014, 14:46
I travel 65kms to and from work, I slipstream trucks every day, as a result I get 800kms out of 45 litres as opposed to about 650kms out of 45 litres. In terms of braking, the braking performance of my car is far superior to a truck's and the difference in inertia ensures that my velocity is invariably reduced faster than the truck's even in an emergency braking scenario and given reaction times etc.

I've driven and driven with people who refuse to draft because they say "it's dangeraous", I counter that their refusal is a resut of the fact that their situational awareness is so shockingly bad and it's evident in all aspects of their driving.

Trucks here (Canadia) are limited to 105kmh (65mph). If I tucked in being a Greyound or GO bus I could draft at 120kmh but the buses lane hop constantly.

Drafting rules, it's good for the environment :ok:

Fareastdriver
11th Apr 2014, 15:18
Very foggy day on the Beijing/Tianjin expressway. The temperature is below freezing and there has been no ice or snow clearance so my driver is proceeding cautiously at 30 k.p.h. In the centre lane we come across a police Mitsibishi 4X4 with nobody in it. In front of that is another police 4x4 that has heavily rear-ended a big Mercedes. The reason it rear-ended the Mercedes was because it had even more heavily rear-ended another police 4X4 which had slammed into the back of an articulated truck.

The police in from the rear 4X4 weren't interested in their fellows in the jeeps, they were panicking around the rear doors of the Mercs.

As we passed the truck I thought of helping out with the injured but my driver steadfastly carried on. They were too important for him to worry about.

It probably cleared out a bottleneck in the Party's promotion ladder.

Shaggy Sheep Driver
11th Apr 2014, 16:30
Tbird - rail freight is actually a fast-growing sector in UK. It's true that final delivery might require road transport, though major flows such as coal, stone, oil etc. go direct from source (or docks) to customer (or docks). But that's often the case with road transport as well - depot to depot long distance transport, depot to destination short distance transport.

It's the long distance multi-modal container traffic, to / from docks and railheads and warehousing, that's growing fast. Its growth is hampered, however, by lack of paths on our over-full rail network - hence we need HS2 to free up slots on the conventional network for stopping trains and for freight. And get a lot of those tailgating trucks off the motorways!

cockney steve
11th Apr 2014, 17:23
^^^^ arguing semantics! As far as joe public is concerned, "fixed penalty"= "on the spot"...IE the penalty is fixed "on the spot"...if you don't get a "tug" you don't have a spot at which you became liable for a penalty, OK? makes sense?

In 1975 I hired a 7.5 ton GVW lorry to move from Southend , Essex, tomy current abode (Lancashire) It would do about 60 mph, flat out...trying to overtake a HGV was impossible, the slipstream just shoved you back,
So, I did what every other HGV attempted to do, tucked into the "still" zone behind the vehicle in front,eased off the throttle and saved a good few MPG. It was a quite remarkable demonstration of how much energy is needed to push-aside the air at those sorts of speeds.

The 2-second gap is a total myth EXCEPT IN A CASE OF AN ACCIDENT AND ABRUPT, UNFORSEEN STOP Otherwise, you just need your reaction-time to hit the brakes when you see the one in front light-up.
Like any other field of human endeavour, it could be done a lot more safely, but HGV drivers handle the extra risk pragmatically.....the fact is, millions of lorry movements take place daily in the UK with very few "ass enders" .....It could be argud that the national fuel-saving more than offsets the cost of the accidents that Commercial Vehicle tailgating causes.

Once was enough for me, and cars are a different ballgame altogether, so don't all jump on the outrage-bus at once!

Krystal n chips
11th Apr 2014, 17:46
About this 2sec rule......the one that's, allegedly, a "total myth"..... albeit this comment was followed by a nice piece of contradiction...

Keith Lane - 2-Second Rule (http://www.keithlane.com/page4.htm)

And, if the last time you drove a 7.5 tonne vehicle was '75, errm, their performance has improved "ever so slightly" since then.

Which leads back to the OP whose probably wishing he'd never asked a reasonable question here on JB.

Actually, when I saw the title, I thought it was about a popular pastime in Manchester.

ShyTorque
11th Apr 2014, 17:50
Believe it or not, but ....
Exactly this is in the works, "drafting" performed by automated vehicles, a train of uncoupled artics running very close together but "talking" to one another by some sort of short-range radio link, perhaps "Bluetooth." They would have radar to keep the distance, along with automated braking.

Another problem with this idea is one that already affects some motorway stretches at busy times. The HGVs are driven so close together (two lanes full of them) that they block out traffic trying to exit. I pass one particular junction at the bottom end of a long downhill stretch. Unless you are aware of the problem in advance and get into lane one about a mile and a half or more further back, you might not be "allowed" in by these less than professional drivers. I've seen cars in lane three indicating left for hundreds of metres and no-one lets them change lanes so they try to force their way in at a late stage, not a safe procedure, which can cause sudden braking in all three lanes. I've seen a few miss the exit completely. The "knights of the road" in HGVs are still out there, but in diminishing numbers, it seems.

Physically tie a line of HGVs together and no-one will be able to join or leave the motorway.

Shaggy Sheep Driver
11th Apr 2014, 18:12
"drafting" performed by automated vehicles, a train of uncoupled artics running very close together but "talking" to one another by some sort of short-range radio link, perhaps "Bluetooth." They would have radar to keep the distance, along with automated braking.

Still needs a driver and an engine / transmission / fuel system / cooler group per container and still has the high rolling resistance of pneumatic tyres. Much of this 'depot to depot' or 'depot to/from docks' stuff could go by rail and eliminate all that waste, inefficiency, congestion, accident potential, and pollution.

Effluent Man
11th Apr 2014, 18:37
Thanks for all your replies,rather more as I suspected focused on the legal and safety aspects rather than the science.On a sparsely populated M2 at 0300 seemed the perfect place to experiment.I suppose there exists the tiny possibility that young Norbert might have hit something solid and stopped dead.If he had braked then my one ton Peugeot would most likely have outbraked his 44tonne truck.But these risks have to be taken for the science.

I am puzzled where the extra 12mpg came from.I think his vortex being messed about with by my presence may have a dragging back effect but still awaiting a definitive answer.

Dak Man
11th Apr 2014, 18:51
The truck, as he moves through the air, produces a turbulent wake behind himself. It makes vortices, the vortices actually make a low pressure area behind the truck and an area of wind that moves along with the truck. If you're following in the low pressure area you can gain an advantage. The low pressure "sucks" you forward and the eddys push you forward, so you need to use less fuel for a given speed.

Drafting not only helps you following the truck, but the truck gains an advantage as well. The interesting thing is by filling in its eddy you marginally improve the trucks performance as well. So two vehicles that are drafting can put out less energy than two vehicles (who are not drafting) would covering the same distance in the same time.

ShyTorque
11th Apr 2014, 18:51
I'd say that his truck had already imparted energy into the air to make the vortex wake, so you "recycling/borrowing" that energy would have little effect on his mpg.

Shaggy Sheep Driver
11th Apr 2014, 18:57
OK - as he bores a hole in the air a low pressure area forms at the back of the truck while the displaced air from in front slipstreams round the sides and over the top then curls in to fill the partial vacuum behind the truck.

If you follow close enough you get pulled along by the curling-in slipstream air, and because the front of your car is in the low pressure area behind the truck, you have less of a headwind to overcome. Both these effects give you more speed for a given fuel consumption, or less fuel for the same speed.

You presence or not has no aerodynamic effect on the track at all. In fact if anything it might help the truck by your helping to 'fill in' the partial vacuum behind the truck with the 'bow wave' of air pushed along by your car.

EDIT - crossed with Dak Man.

wings folded
11th Apr 2014, 18:58
I don't have a scientific answer, nor a relevant PhD thesis to lend support, but I always believed that energy is neither created nor lost in the global scheme of things.

So I think that you are nicking some energy off old ND's lorries, but given the rate that they guzzle diesel, he would hardly notice the reduction in mpg with or without a Peugeot in tow.

Shaggy Sheep Driver
11th Apr 2014, 19:01
You're not 'nicking' anything from the truck, as I and Dak Man posted. The energy you are taking advantage of would otherwise be dissipated by creating more air turbulence, and slightly heating the air by so doing. So by tailgating you are also doing your bit to combat global warming!

Effluent Man
11th Apr 2014, 19:09
When my son was about five and we were on long car journeys I used to amuse him with stories of Norbert Dentressangle.We passed his depot just outside Calais and It was filled with red and white trucks."Ah Uncle Norbert with his three sons,Humbert,Egbert and Siebert".Tales were told of them all sitting drinking red wine around the fire while old Grandad Gilbert regaled them of his days in the French Resistance.He always wanted to stop and meet them all but we invariably had a ferry to catch or an onward destination offering Vin Jaune and wild trout teased from a bubbling Jura stream.

Windy Militant
11th Apr 2014, 19:23
The fact that it's dangerous aside, if you want to see a good explanation of how this works have a look at "Guy Martins Speed on Channel 4oD if you can get it. The episode you want is the one with the Bicycle speed record. They show how the Pace truck causes a pocket of still air that Guy then rode the bike in.
It also shows how dangerous tailgating is!

Mythbusters have also covered this phenomenon. ;)

chuks
11th Apr 2014, 19:28
"Fineness" is the ratio of frontal area to length; an object longer than another of equal frontal area has a greater "fineness ratio," which results in it also having less drag. Think of a flat plate square to the relative wind, versus the same flat plate stuck to the front of a long cylinder, when the latter has less drag. The shape behind the front sorts out those pesky vortices, up to a point.

Modern aerodynamics has a lot more stuff, stuff that is totally counter-intuitive, such as square trailing edges on some surfaces that look simply "wrong."

Now all we have to do is wait for those "treadmill people" to show up, and then we shall be ready for a very entertaining discussion!

Anytime you are close to a lorry, if you cannot see his mirrors then you are at risk of squashification, and that certainly goes for drafting him, too! The idea of sitting there right behind a 40-tonner, counting on your quick reflexes and shorter braking distance to keep from running into the back of it ... I envy your optimistic nature, but Darwin may have already made plans for you!

Saintsman
11th Apr 2014, 19:37
So, you are driving at a 'safe' distance behind said lorry. Does that mean your fuel consumption will increase because of all the additional air that is coming from the vortex, which is now right in front of you?

John Hill
11th Apr 2014, 21:48
I dont know why no one has ever taken up my idea for an inflatable tail cone for trucks.

Some sort of fabric tail cone attached to the rear of trucks that would be inflated when entering a highway and 'sucked back' into its stowage area when leaving the highway.

John Hill
11th Apr 2014, 21:53
Your family Volvo should really have better brakes than most trucks so tailgating a truck should be OK provided you can brake when he does and not sometime later.

Some sort of wireless coupling between your brakes and the truck might be an idea worth looking at. Maybe something that can detect his brake lights faster than your already lighting fast reactions.

Radar on the car is hopefully going to do the same thing.

G-CPTN
11th Apr 2014, 22:02
Volvo have a system called 'collision protection':-
This is how it should work:-
http://www.youtube.com/watch?v=b1eBEUbN-ZE

This is how it was demonstrated:-
http://www.youtube.com/watch?v=0eChAKm1t3U

You have to click on the YouTube icon on the bottom.

RatherBeFlying
11th Apr 2014, 22:42
Drafting does reduce drag for all participants.

But hydroplaning onset speed is a function of tire pressure. It can become suddenly painful when the shopping HGV in front is not hydroplaning when you are. This may depend on whether his wheels have cleared away the water and how wide are your axles;)

Krystal n chips
12th Apr 2014, 07:33
" The energy you are taking advantage of would otherwise be dissipated by creating more air turbulence, and slightly heating the air by so doing.

Physics for beginners then....


" So by tailgating you are also doing your bit to combat global warming


Alas, no. You are in fact more likely to be contributing to global warming....by becoming a source of methane. Although as this compliments your views on flying over water, sans life jackets, all we need now is your Darwinesque entry for sea travel and the trilogy will be complete!

ORAC
12th Apr 2014, 09:18
Volvo SARTRE driverless convoy completes road test (http://eandt.theiet.org/news/2012/may/volvo-convoy.cfm)

the SARTRE Project (http://www.sartre-project.eu/en/Sidor/default.aspx)

magpienja
12th Apr 2014, 11:24
Used to do this on our bike when we where kids following with our front wheels 18ins from the rear end of an Atlantian D/D bus on our way to Liverpool Airport on spotting duties....40mph no probs with just light input on the pedals,

Daft yes...fun....yes.

Effluent Man
12th Apr 2014, 14:02
On a similar note a friend got a Lambretta LD150 scooter when I was sixteen.One night we decided to go out to a pub in the country about five miles from where we lived.He was a learner so not allowed to carry a passenger.He said" Hold onto my shoulder and get a tow" We had our shandy and set off back,reaching an indicated 50mph on the Lambretta speedo.the problem was I had a fixed wheel and the pedals were rotating at a fantastic rate of knots.I had to raise my legs out of the way of the whirring metalwork.As you say dangerous but fun.

cockney steve
12th Apr 2014, 14:30
@ K'n C The move of abode was not the last time I drove a wagon! less than 10 years ago, I hired another for a couple of days, moving stuff from Preston to Stalybridge....apart from the intervening trips to Ministry for plating, driving recovery wagon etc.

Your reference was "defensive driving" all statistics are biased, as the author had an agenda......here, we're specifically discussing the fuel-efficiency of tailgating/slipstreaming. Iwas playing Devil's Advocate , pointing out the "-sec. rule is a fallacious premise.......the author demolishes his own position when, after giving delay for bulb to light, delay for air system to operate, etc. the following HGV apparently, will run you over because his brakes aren't as good or fast as yours!
FLAWED LOGIC, REASONING AND FACTS

Only a few years ago, the "experts" such as AA and RAC were claiming that it was scientifically impossible to exceed 1G of retardation.....that is, until a motoring magazine published a road-test showing a higher figure and was able to repeat it at will!
clue--tyre compound allows road surface to penetrate surface of tread, giving a mechanical "ratchetting" action)

When the vehicle in front starts braking (again, most lights are mechanically switched,as soon as the pedal leaves the stop) it does not stop dead....which is why you never normally hit the vehicle in front

REPEAT..UNLESS AN ACCIDENT STOPS IT INSTANTLY!

if the 2-sec rule were to be applied in urban areas, the country would grind to a standstill.

As a percentage of vehicular movements, accidents are infinitesimal.

cattletruck
12th Apr 2014, 14:42
So there you are in your sports shopping trolley using your F1 skills to save a few petrol dollars by slipstreaming behind a truck.

But what you perhaps didn't know is that the driver of this truck is also the owner and last week he was rear-ended by another vehicle which broke his cargo lifting unit and made the rear doors difficult to close. Unfortunately the driver who caused this damage gave false details and left the owner of the truck you're now following a few feet away with a repair bill of a few thousand dollars.

Now the owner of the truck saw you sneak up behind him but can now no longer see you. Then he thinks about the repair bill he has to pay....

Where did that dog on the road suddenly appear from?

Lightning Mate
12th Apr 2014, 17:31
"if the 2-sec rule were to be applied in urban areas, the country would grind to a standstill."


You silly person.


I have a clean 1966 issue driving licence and drive a very high powered Mercedes.


In my opinion, two seconds is a ridiculously short time.


I use distance. Even at 60mph on a dual carriageway, I always maintain 100 yards minimum between my vehicle and the one in front.


On a three hour journey this adds about a minute to my time to destination.

Krystal n chips
12th Apr 2014, 18:17
CS......

We agree on one point, the author does have an agenda.....it's called "staying alive".....and I am all in favour of it !

There is a significant difference between urban and motorway driving as we know, however, whilst the "2secs" rule which you deride so vehemently....why may I ask ?..........is not really practical, the distance apart criteria remains the same....as much as you can get, even in heavy urban traffic.

I know the HGV world slipstream and why they do it....but, frankly, I have never seen the value to a car driver in getting that close to an HGV.

As for the accidents vs journey stats being infinitesimal, do have a look at the fatalities involved....let alone the serious and life changing injuries....then come back and tell me the stats are, as you implied, of no relevance.

A few years later than LM, but, I also have a life long clean licence and that includes commercial driving for a while....vans / 7.5 tonnes.....wonder why this could be ?

Capot
12th Apr 2014, 22:47
I use other peoples' slipstreams all the time, but nearly always a largish van, usually white and usually doing 75-80 mph, which is exactly right.

Doing that when practicable, and when the opportunity is offered, increases my average diesel consumption (Focus Estate) from 55 mpg to 60+ mpg. That's about 50L a year less, worth about 70 and a 10% saving, very roughly.

If this is being effective you're way too close to the truck for your own safety if he brakes suddenly

Yeah, yeah, whatever. I can bring the Focus to a complete stop in a lot shorter distance than the van (or HGV) in front can do the same. It's the effin' tailgater behind me that I worry about.

Avtrician
13th Apr 2014, 06:01
In Oz, we wouldnt dream of slipstreaming a truck on the open road, especially on a bike. Encountering shredded Roo, pig, wombat, camel or other wild life is not so much fun

mad_jock
13th Apr 2014, 09:52
Quite often lorrys out brake cars.

The new artics have all the bells and whistles when you slam the brakes on.

At a full load you won't touch them but if they only have 5-10 tons on the back they have loads of more rubber on the road to get rid of energy.

2 front tyres

2 tyres on the ridding axle

4 on the drive axle

then 2 on each of trailer axles so 6 total. So 14 rubber footprints.

The only time my arse started twitching in an artic with breaking was when some idiot whizzed by me and then pulled in and started breaking like hell to either slow down for a roundabout or to turn a corner and I was 44 tons of drill pipe on the back trying to keep 2 artic lengths as my safety zone.

Three of the lads did rear end cars in similar situations and the occupants received life changing injurys. Unfortunately for the car occupants every incident was on CCTV and they didn't receive the expected insurance pay out.

I really don't understand why car drivers go anywhere near lorry's on the road. Honestly when we clip a gear changing there is more of a jot than if we hit a car. If lorry hits a car fully loaded it doesn't matter what the make or model is, its just a beer can getting squashed.

Hell I had a Golf GTI try and go up my inside when I had taken half a lane to get round the corner. Unfortunately for him I had already kinked the cab when he tried this little manoeuvre so he got trapped between a wall and my side bars. And there was only one thing going to happen when I not knowing he was there floored it with 720 Brake horse power in third gear. Again thanks to CCTV I was in the clear he lost his car because he was only third party and it took 20mins with a sledge hammer to sort the side bars out. I believe he was 6 weeks getting operations to sort his ankle out and a further year in physio.

Cyclists are a bloody menace as well. And then they get all upset when go up the inside and get taken out.

BTW I used to cycle to work when I was driving artics as did quite a few of the guys so its not to say all lorry drivers don't know the deal about push bikes. We never went near lorrys on the road because of having a full understanding that the driver can see cock all to do with a cyclist be they in full dayglow with lights or black lycra. About the only thing you did see was those illegal led strobes.

Lon More
13th Apr 2014, 10:06
I can bring the Focus to a complete stop in a lot shorter distance than the van (or HGV) in front can do the same.

He thinks, he brakes. You think :mad: and brake as you hit him. It's not the fact that your car has better brakes, it's the reaction time (or distance) plus the braking distance.

It's the effin' tailgater behind me that I worry about.

He's probably thinking the same thoughts about you

ShyTorque
13th Apr 2014, 10:12
I really don't understand why car drivers go anywhere near lorry's on the road. Honestly when we clip a gear changing there is more of a jot than if we hit a car. If lorry hits a car fully loaded it doesn't matter what the make or model is, its just a beer can getting squashed.

I agree, so the HGV drivers tailgating car drivers have no excuse whatsoever.

Shaggy Sheep Driver
13th Apr 2014, 10:23
Everything mad Jock says points to ludicrous safety case (i.e. it's unsupportable) for mixing these dangerous behemoths with ordinary traffic, especially in towns and cities.

Lon More
13th Apr 2014, 10:26
I agree, so the HGV drivers tailgating car drivers have no excuse whatsoever.

I don't think anyone has said it's acceptable. It's something speed limiters, Overtaking bans, even the culure in todasy's haulage industry, make inevitable

So you're sat there, in your Morris Marinade doing 40mph in the middle lane of a deserted 3 lane motorway, thumb up bum and mind in neutral. You deserve more than being tailgated :ugh:

mad_jock
13th Apr 2014, 10:46
Problem is its what the consumers need and want.

Mostly I drove them in Aberdeen which because of years of history your high power heavily laden artic was pretty much 10-20% of the traffic load on the key routes between the various industrial sites. The locals is the main know not the mess about with them and stayed clear.

Have to go down to Edinburgh and Glasgow and its was a whole different ball game.

Most lorrys drivers would prefer to do there drops early doors before 7am or after 7 pm. But most large citys have banned lorry movements in that time slot inside city limits and also the customers won't let you deliver at that time anyway.

Using smaller lorrys actually makes things worse as you just have more of them. And using ridged is worse than artics I found much prefer a short couple unit with a metro trailer than a high volume class 2. Its easier to get round corners and you only have to do the trip once instead of twice.

John Hill
13th Apr 2014, 11:41
Tail gating trucks do annoy me somewhat but I do know that should I ever have to stop suddenly the truck driver on his elevated perch probably saw it before I did.

ShyTorque
13th Apr 2014, 11:44
So you're sat there, in your Morris Marinade doing 40mph in the middle lane of a deserted 3 lane motorway, thumb up bum and mind in neutral. You deserve more than being tailgated

I wholeheartedly agree that the middle lane hogs need pulling over and re-educating - but when do you last see a police "traffic" car? Our local force disbanded their traffic department some years ago, as usual on cost saving grounds.

But you will never see anyone having cause to tailgate any of my vehicles, especially in an HGV - and I certainly never drive in that way. My car lives at the top end of the speed limit, keeping well clear of HGVs.

If anyone comes up behind, I let them go past as soon as possible because I have no wish to hold any driver up, however quickly he/she wishes to go.