If a standard artic is doing its maximum 56mph, how close to it would your car need to be to gain from being in its slipstream?
And at what distance would you actualy be in the most "turbulent" area?
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I have done this, when I got 47mpg from a tank. You choose your truck and your stretch of road, and only really works on Motorways. If you jump from truck to truck you can find one that cruises at more than 56mph.
To really slipstream you need to be very close - a few feet, but there is a kind of boundary layer further away that gives almost as much, drive up close and you can feel the two distinct levels, you drive through a buffeting layer and you have it. About 5 yards away.
I managed to get hauled up some hills on the A1 on trailing throttle behind a transporter full of land rovers. Square and turbulent lorries are best, fuel tankers or bulk powder products are useless.
Its not safe and its not relaxing.
Last edited by: Zero on Wed 15 Jun 11 at 19:54
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Why not just reach out and grap the back and get a tow
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We used to grab onto the tail of flatbed trucks to get a pull up the hills in Edinburgh on our bikes as kids. One rather more eccentric friend used a reversed walking stick to hook on to lorries or buses for the same purposes as a teenager.
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>>>>
>> Its not safe and its not relaxing.
>>
Presumably if cars had buffers like railway wagons then it would be safe?
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Tenous old Volvo link there Cliff?
:-)
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That confirms it, you are mad ! :-)
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Who Cliff? Nah, one of the sanest here I'd say !
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I was thinking more of Zero, he actually admits slipstreaming. I don't like driving behind anything I can't see through or around, I like to be able to see any problem ahead so that I don't become part of it.
Last edited by: Old Navy on Wed 15 Jun 11 at 20:31
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Which is why I said it was dangerous and not relaxing.
Last edited by: Zero on Wed 15 Jun 11 at 20:33
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They did this on Mythbusters, and measured all the distances and mpg improvements (on a track). From memory, it does make quite a big improvement in consumption (about 30% I think) from a moderately close distance - one they said was really dangerous but seemed quite ordinary to those of us used to UK roads I thought.
You could probably find it at the Discovery channel website if you cared - straight googling for "Mythbusters Driving" videos is interesting but doesn't seem to throw up that one.
Last edited by: Crankcase on Wed 15 Jun 11 at 20:26
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If you get close enough to the back of my lorry, you'll notice a sign which states "If you can't see my mirrors I can't see you". It's there for a reason; because I really do not want some clown terminating himself whilst piddling about trying to read his GPS to find out if he's managing to achieve 0.001 mpg more by tailgating me. You would have to be that close to get the benefit of my slipstream.
If you're really that concerned about saving petrol, buy a bicycle instead.
I really can't believe that anyone would be dumb enough to try it regularly; there are enough legitimate complaints on here about tailgating already without giving them encouragement.
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Given that most lorry drivers drive fagpaper close to the one in front, I find most of them not qualified to comment about slipstreaming.
Not to mention the trucker that was deliberately terrorising the car in front on the M1 northbound in the luton roadworks on Tuesday because he was not doing 53mph in the 50 limit.
Last edited by: Zero on Wed 15 Jun 11 at 20:44
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>> Given that most lorry drivers drive fagpaper close to the one in front, I find
>> most of them not qualified to comment about slipstreaming.
>>
>> Not to mention the trucker that was deliberately terrorising the car in front on the
>> M1 northbound in the luton roadworks on Tuesday because he was not doing 53mph in
>> the 50 limit.
>>
>>
Two wrongs don't make a right Zed. For the record, I don't approve of 'em either, I've been known to get out of the cab at traffic lights, open the rear doors and ask the tailgating driver behind me if he'd like a closer look inside. Either that or I slow down till he gets the message.
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Oh agreed HM, but I have to say its a far more common site to see truckers doing it to other truckers and cars, than cars tailgating truckers.
I passed a very severe crash at cathorpe, where one trucker had tailgated into the back of another, the cab clearly not remaining a survivable place to be, yet the the trucks sailed on by with less than a third car length between them
I have no idea, but is there some form of limiter induced hypnotism at work sometimes?
I have come to the conclusion that speed limiters on trucks cause more issues than they solve.
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>>
>> I have no idea, but is there some form of limiter induced hypnotism at work
>> sometimes?
>>
>>
>> I have come to the conclusion that speed limiters on trucks cause more issues than
>> they solve.
>>
It does make you wonder. Back in the day, I drove old British tanks such as ERF's and Seddon-Atkinsons, which had linkage-operated throttle pedals much heavier than the fly-by-wire job on my current Volvo; cramp was an obvious problem on long motorway journeys but (combined with the radio-drowning noise which modern drivers would find intolerable) it did at least keep your mind focused.
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I used to do it on my Honda 250N for an entirely other reason. Didn't do it for long as I became aware of the meanings of the words bold and old. A fool's game on a bike.
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A fool's game on a bike.
>>
Or any other form of transport.
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A Vespa rider found that out when I had to do a sharpish stop in an old 15CWT van that had no rear windows. I had no idea he was there. He insisted on the BIB being called as he maintained I'd stopped too quickly. He then told BIB he was following about 3 feet behind me to try and keep dry in the heavy rain!
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Been there and done that BT (there is a vortex of less wetness behind a truck) These days, I close all the zips on a rather excellent BMW suit, crank up the heated grips, turn on the heated seats, tuck in behind the trick electrically adjustable screen.
Last edited by: Pugugly on Wed 15 Jun 11 at 21:10
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>> Tenous old Volvo link there Cliff?
>>
>> :-)
>>
Surprisingly, not.
I was thinking that railway wagons have proper buffers with springy rams, designed for shunting.
When the train does an emergency stop, the tailgating wagons all run into each other harmlessly. So perhaps if slipstreaming a lorry with a 6" gap it wouldn't matter that you couldn't see anything - if he slowed, you would slow too.
My father once described being a passenger in a guards van at the back of a long train of old fashioned wagons, in about 1950. They used to be coupled by dangling bits of chain, so each wagon was free to an appreciable distance in relation to its neighbour.
He said that as the engine pulled away, you could hear a rapidly quickening crescendo of bangs as each wagon was accelerated. By the time the pull reached the back of the train, the front was already travelling quite fast, and the guard warned him to sit down and brace himself for the considerable shock as the van suddenly went from 0-20 in about 1 second.
So if Zero fitted railway buffers to his car ...
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>> at what distance would you actualy be in the most "turbulent" area?
Look at the cloud of mist behind a 56mph lorry in heavy rain. Without too much of a crosswind the area of most intense turbulence can be seen to be about 2/3rds the length of the lorry, ie about 30ft. So it seems that a following driver would gain some aerodynamic advantage by staying closer than 30ft - of course they would be well inside their safety braking buffer zone doing that.
I slipstreamed an artic down the M1 one very windy night a few years ago. I was in an old (non speed-limited) 7.5 tonner with a 12ft high body and no air deflector on the cab roof. It was struggling to hit 45mph into a headwind. The traffic was very light, so when two irish registered trucks (Scania 143 V8s IIRC) came barrelling past me at 65mph or so I swung out behind the second one and found it was like driving in a gentle Spring breeze. I was able to comfortably keep up with it for about 40 miles until I reached my junction. When I peeled off onto the sliproad the reintroduction of the headwind was like stepping outside the house in a gale.
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I confess I did something similar soon after getting married.
Funds were short and I had an old 100E with a rattling bottom end (a lump of box section with attached spring hanger was also poking through the boot floor). I found that following large vehicles closely, dramatically reduced the amount of noise from the crank. I was doing weekly 40 mile round trips to college and occasional 250 mile round trips on training courses (Yarnfield - anyone with memories?).
That old car did several months in that condition, gawd only knows how.
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Some lorry drivers are paid a bonus if their fuel consumption is lower than average.
Perhaps that's why some of them tailgate the truck in front.
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That's the converse of my point - the fuel saving could only be at the expense of the lorry being tailgated. So you would expect drivers to get really angry about other drivers "stealing" their fuel, and start taking measures to prevent it. Flicking their brake lights, and powerful or unladen lorries deliberately slowing on hills in order to lose a freeloader.
Also you would expect to see 56mph lorries jostling to be at the back of the queue rather than the front. It doesn't happen, does it?
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...So you would expect drivers to get really angry about other drivers "stealing" their fuel...
The driver at the front may not know he is being tailgated, depending on the length of the lorry doing the tailgating and how close it is.
I appreciate the front driver would only need to see the back of the second lorry, but there is a significant mirror blindspot behind a large lorry.
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>> ...So you would expect drivers to get really angry about other drivers "stealing" their fuel...
>>
>> The driver at the front may not know he is being tailgated, depending on the
>> length of the lorry doing the tailgating and how close it is.
If the driver at the front got angry it would be a bit dog-in-the-manger - (s)he isn't using any more fuel than he would if the tailgaters weren't there.
But of course they ought to take it in turns to be fair.
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>> >> ...
>> (s)he isn't using any more fuel than he would if the tailgaters weren't there.
>>
>
>>
But if the tailgaters are saving fuel that can only be because the one at the front is "towing" them? Where else can the energy come from but extra fuel used by the one at the front?
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>> >> >> ...
>> >> (s)he isn't using any more fuel than he would if the tailgaters weren't there.
>>
>> But if the tailgaters are saving fuel that can only be because the one at
>> the front is "towing" them? Where else can the energy come from but extra fuel
>> used by the one at the front?
As I understand it Cliff, and hopefully someone will correct me if I'm wrong, the leader has already burnt his extra fuel causing the turbulence, whether there is someone behind him or not. The tailgaters are just making use of that turbulence - I guess the energy in the air is being transferred to the tailgater rather than going into other forms (noise/heat?).
A boat makes waves as it goes through water - if you surfed on one of those waves, you wouldn't slow the boat down.
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>> >>
>> When I peeled off onto the sliproad the reintroduction of the headwind was like stepping
>> outside the house in a gale.
>>
And the lorry driver would have felt that his trailer had uncoupled?
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>> And the lorry driver would have felt that his trailer had uncoupled?
I suppose they would, I hadn't thought of it like that!
It was sometimes the case in this 7.5t (on less windy days) that it could begin to overtake a bigger lorry but not have enough power to "push through" the volume of air being displaced to the sides of the bigger vehicle's cab. So you'd come up beside an artic and then be slowed down to its speed alongside it.
Last edited by: Dave_TDCi on Thu 16 Jun 11 at 08:58
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I haven't got the equations to back this up (where's NC when we need him?) but intuitively it seems to me that the front lorry's fuel goes into creating the vortex / partial vacuum behind it, whether there's another vehicle there or not. That partial vacuum then fills itself by sucking in whatever's in the vicinity, usually air but in this case the second lorry. I don't see that the second lorry has any effect on the fuel consumption of the first.
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>>I don't see that the second lorry has any effect
>> on the fuel consumption of the first.
>>
Then wouldn't it follow that a long lorry would have no greater fuel consumption than a short lorry?
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Of course not but it does make a difference if the trailer is close coupled or not.
Also if the cab air deflectors are set at the right height for the trailer too.
Pat
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>> Then wouldn't it follow that a long lorry would have no greater fuel consumption than
>> a short lorry?
>>
Actually given the same engine and gear ratios, weight, rolling resistance and frontal area the longer lorry may be more fuel efficient because its drag coefficient will be better.
Needs some working out though.
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>> Then wouldn't it follow that a long lorry would have no greater fuel consumption than
>> a short lorry?
Using my boat/surfer comparison above, a longer boat makes more waves and will need more fuel. But the number of surfers riding on its waves doesn't affect the amount of fuel used.
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>> But the number of surfers riding on its waves doesn't affect the amount of
>> fuel used.
>>
Hey man cool, peace man!
Sounds almost Cantonaesque.
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>> Sounds almost Cantonaesque.
You should see my flying kicks.
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>> Then wouldn't it follow that a long lorry would have no greater fuel consumption than
>> a short lorry?
There's something in my dim and distant physics memory called IIRC 'skin drag'. It means the greater the surface area of an object, then the greater the wind resistance. Therefore the longer lorry will presumably have a greater area and greater drag.
Of course it may not be very applicable to the relatively low speeds of road transport compared to air.
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>> >> Then wouldn't it follow that a long lorry would have no greater fuel consumption
>> than
>> >> a short lorry?
>>
>> There's something in my dim and distant physics memory called IIRC 'skin drag'. It means
>> the greater the surface area of an object, then the greater the wind resistance. Therefore
>> the longer lorry will presumably have a greater area and greater drag.
>> Of course it may not be very applicable to the relatively low speeds of road
>> transport compared to air.
And don't two lorries tailgating become "one" aerodynamically, and therefore increase skin drag on the powering unit up front?
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>>And don't two lorries tailgating become "one" aerodynamically, and therefore increase skin drag on the powering unit up front?
I don't think so. The overall skin drag of the two vehicles will of course be greater than one. The following vehicle will be moving into air that's already moving in, generally, the same direction and at a speed approaching that of the following vehicle, as opposed into a mass of stationary air that it has to push aside.
I can't see how one vehicle slipstreaming another can have an effect on the leading vehicle. The second vehicle is sitting in the air that's left the first. However I've heard verbatim reports from F1 drivers who claim they can feel when a following car moves out of their tow.
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I've been watching this and smiling:)
I wish it was that easy, I would be rich!
Believe me, to get a fuel bonus a lorry driver has to save a much larger amount of fuel than it would use having anyone tailgating them.
It entails not revving out of the green in any gear, anticipating when the load can do the braking for you and where to stop accelerating to allow this to happen, and probably the biggest saving is not leaving the engine ticking over.
The reason we don't like cars tailgating is that we're always aware that if something happens in front, and we have to brake suddenly, then we have to worry about not hitting it, the load moving forward under braking as well as the car/lorry hitting us up the bum.
At the risk of annoying you all, we do always question how an UNqualified driver (car driver) thinks he's able to make a judgement on whether the distance he sees between two lorries is safe or not.
He doesn't have any experience of air brakes (Rattle does!) and usually has a very poor judgement of length when it comes to allowing a lorry enough room to manoeuvre.
One of the most frequent calls on the O800 'Hows my driving' number are complaints to TM's about tailgating and good ones ask in reply, what qualifications the car driver has to judge since no accident happened.
Pat
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>> One of the most frequent calls on the O800 'Hows my driving' number are complaints
>> to TM's about tailgating and good ones ask in reply, what qualifications the car driver
>> has to judge since no accident happened.
>>
>> Pat
thats extremely arrogant and patronising, and is a classic reply indicating why lorry drivers tailgate cars and other lorries. it seems because they think they know better.
I can stop my car, from any speed, faster than you can stop your loaded lorry. And my thinking time is the same as yours. Seems to me that if a car driver who can stop his car shorter than your truck, then they are qualified to know when you aint got a hope in hell of stopping yours.
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I agree with Zero I am afraid.
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Pat, we appreciate your view from the cab, and much of what you give us is valuable, but that really is utter rubbish. No accident happened, therefore it wasn't dangerous? Zero is spot on - and even if an HGV driver's superior observation and texting anticipation skills mean he won't need to brake sharply, it's just plain discourteous to drive intimidatingly close to another road user.
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It might be extremely patronising but it also happens to be true when you look at the fact that I was talking about two lorries tailgating each other.
Utter rubbish in your opinion but total reality in all lorry drivers.
If you're talking about the TM's attitude to the caller then maybe you should spend some time answering the phone to the complaining public.
The last one rang and complained that the lorry in front of him 'wont get over 40MPH and I'm in a hurry'
When it was explained to him that the legal limit for a lorry on that road was 40MPH he asked why it hadn't pulled over to let him by.
Asked if there had been anywhere to pull over, he said 'not yet'
I've sat in a busy traffic office hot seat and there's more to do than deal with idiots like that, I'm afraid.
The simple fact is that someone tailgating a lorry is a pain, just for a moment.
First you decide if it's an unmarked police car, then you decide if they look dodgy and could be trying to stop you.
Once that's sorted, it's eyes and observation to the front and let the idiot driving too close behind sort himself out, and it happens so often it tends not to worry us anymore.
Now if you want to talk about lorry drivers texting WdeB, I can tell you that I've had far greater vision into overtaking cars than you'll ever get into a moving lorry cab, and you wouldn't believe what I've seen car drivers doing.
And Zero, you admit tailgating and hogging the middle lane but call me patronizing.......could it be drivers with your attitude have given me the view I have?
Pat
Last edited by: pda on Thu 16 Jun 11 at 13:01
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>> >> And Zero, you admit tailgating
At least i had the sense to say its dangerous and risky. But then I am just a car driver, what the hell would I know
>>and hogging the middle lane
Conveniently missing out the vital word "empty" motorway?
>>but call me patronizing.......could it
>> be drivers with your attitude have given me the view I have?
No. Drivers with your attitude, the "poor lorry drivers who can do no wrong and we know better" one.
Oh and pat, there is, the slight excuse that you can see over the top of a car, but when tailgating another lorry, all you can see is the padlock on the locking bar.
Last edited by: Zero on Thu 16 Jun 11 at 13:06
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>>poor lorry drivers who can do no wrong and we know better<<
Here we go again Zero.
Whenever your faced with the real facts of lorry driving you have to throw the same old line:)
Padlock? Locking Bar. Ah yes that would be a container driver then, that explains it!
Pat
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>> >>poor lorry drivers who can do no wrong and we know better<<
>>
>> Here we go again Zero.
>>
>> Whenever your faced with the real facts of lorry driving you have to throw the
>> same old line:)
As reinforced by you not a few posts up this thread.
Anyway whatever, you have done the damage, you can live with it.
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What damage is that Zero?
The truth hurts sometimes but if you want to know what it's like from the 'other' side, I will tell it like it is.
The basic facts are that if a lorry develops a major fault on the air brakes they come on instantly and without any warning, or action, by or from the driver.
If that happens and you or someone else, is tailgating, I will stop quicker than your car because I don't get a say in it. The thinking time we both have is eliminated.
Pat
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The damage you have done to the reputation of other lorry drivers.
As far as failing air brakes go, what about the truck in front you are tailgating? what if those brakes fail?
Anyway, i am not going any further with this, you clearly can't see the implications of your original post on this subject, and its not place to try and point it out to you.
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This is a motoring forum, exactly the place for you to explaim my great damage to other lorry drivers.......or is that too hard to do?
I've done no damage whatsoever to other lorry drivers, according to your theory they don't have a reputation to damage.
>>As far as failing air brakes go, what about the truck in front you are tailgating?<<
Exactly my point.
The one behind is aware of this and knows only too well the dangers so maybe they might not be as great as they are made out to be by an amateur judgement of the situation.
Pat
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>> The one behind is aware of this and knows only too well the dangers so
>> maybe they might not be as great as they are made out to be by
>> an amateur judgement of the situation.
yes Pat, tailgating is safe. clearly us amateurs have it wrong on that point.
Thank you for putting us right.
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Going to Pats training day this year, Zero, or wimping out again?
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Sarcasm is what you always resort to when you could possibly be a little bit wrong!
Pat
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For the benefit of group harmony, i shall say nothing.
Last edited by: Zero on Thu 16 Jun 11 at 15:40
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Very comendable...by the way you felt the need to point it out:)
Pat
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A lesson you could learn.
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Zero
I think there is a lesson to be learnt from this post......posssibly for both of us.
I posted a controversial, yet accurate reply from the lorry drivers cab and waited with baited breath for a full and frank discussion to follow.
I hoped my points would be queried in a robust but fair manner with a few regular posters, and that I could then elaborate on the more technical points and promote a better understanding in general, between lorry and car drivers.
However, as happens in so many cases, and not just my posts, there was 90 mins when everyone waited for someone to say something (anything would have done!)
Along comes Zero with his brash, opinionated style of aggressive posting attempting to shoot me down in flames.
The result has been a long series of willy waving between you and I, ( and you are better equipped than I to do that, although I've give you a run for your money any day!).
Everyone else, except a couple of posters at the beginning agreed with you as is their right, but no-one else wanted to contribute to what could have been a very good discussion there.
This way of attacking the poster and not discussing the post has seen off quite a few old regulars in the past, that don't have the time or the energy to try and 'score points' with you.
Is it really conducive to 'group harmony' to shoot down everyone else's opinion that differs from your own, without at least a civilised discussion on it?
Pat
Last edited by: pda on Thu 16 Jun 11 at 16:03
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>> Is it really conducive to 'group harmony' to shoot down everyone else's opinion that differs
>> from your own, without at least a civilised discussion on it?
Exactly so why did you do it.
You were the the one who brought personality into it. Not I.
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Do stop squabbling darlings. I'm trying to work.
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At the end of the day Pat, you said that slip-streaming was ok for lorry drivers to do, and that as car drivers we didn't know what we were talking about.
If you think that a valid argument, then that's fine. Don't get upset with me if you find that position increasingly difficult to defend.
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>>>you said that slip-streaming was ok for lorry drivers to do<<<
Can you point out where I said that please?
Pat
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In direct response to the posts about lorries tailgating lorries
"At the risk of annoying you all, we do always question how an UNqualified driver (car driver) thinks he's able to make a judgement on whether the distance he sees between two lorries is safe or not.
One of the most frequent calls on the O800 'Hows my driving' number are complaints to TM's about tailgating and good ones ask in reply, what qualifications the car driver has to judge since no accident happened"
So that was car drivers dismissed as know nothings, anbd Lorry drivers knowing what they were doing when they were tailgating.,
Last edited by: Zero on Thu 16 Jun 11 at 16:27
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looking back at a 300 miles of motorway driving I have done this week, I reckon the average distance between trucks is about the length of the cab, from radiator grille to back of the sleeper section. Whats that? 10 to 12 feet? With no view of the situation in front?
Last edited by: Zero on Thu 16 Jun 11 at 16:38
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So you agree, I didn't say that it was just your 'robust' interpretation of it allowing you to try and browbeat and shame me into submission!
Let me explain ( as I would have done earlier, given the chance)
I wouldn't dream of telling you how far your Lancer needed to stop,
I can tell you exactly how long my CRV needs to stop on both wet and dry roads.
One lorry driver wouldn't dream of telling another how far their lorry needed to stop.
There are too many variables such as if it's fully loaded, partially loaded, where the weight of the load is placed and the condition of the brakes and suspension. Not to mention the state of the road, wet dry, concrete, tarmac etc.
When I'm driving a lorry, just like any lorry driver, I can tell you by the seat of my pants after the first few miles just how far I need to stop it.
I should be able to do that, it's the most basic thing a lorry driver learns.
So why does a car driver, who has never driven THAT lorry, doesn't know if it's loaded or not, feel he/she is a better person to judge that distance?
If an accident hasn't occurred from the reporting car drivers unqualified and impossible to make observation, why would a TM take their word seriously against an employee with an accident free and long standing work history?
I certainly wouldn't make that judgement if I saw two lorries running together.
Sometimes you have to accept that you are the expert at driving your car, no one else can even get near you and that's how it should be.
It doesn't make you the expert at driving everyone else's vehicle though.
Pat
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No, but given my 12 foot average, I wouldn't stop my lancer, and therefore I know you wouldn't stop your truck, loaded or unloaded. You cant dispute that if i cant stop my barely a tonne car, you can't stop your 48 tonnes of truck.
At the end of the day, If I cant do it, neither can you, and that makes me qualified to judge if your distance is safe or not.
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>>At the end of the day, If I cant do it, neither can you<<
I rest my case:)
You have just endorsed everything I took the trouble to explain above, thanks Zero.
Pat
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So you can stop your truck in a shorter distance than my car at the same speed?
yes or no
Last edited by: Zero on Thu 16 Jun 11 at 16:54
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Which truck, what load, what's the weather like, how much sleep did you get last night........read my post Zero, I don't like wasting my time typing.
I have never driven your car....
If you don't believe me pull into Hilton Park lorry park on Saturday and go and ask the other lorry drivers their opinion.
Pat
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In an emergency stop situation, a car will always outbrake a truck - by a significant margin.
There are two reasons which dominate all others when deciding this.
First, the coefficient of friction between tyre and road. Tyres fitted to trucks are always biased towards long life, and away from ultimate grip. They will tend to give co-efficient of friction close to 0.6, while a car's tyres can safely be assumed to give 0.7. Of course, wet surfaces will reduce these values, and car tyres biased more towards high grip will make the difference greater.
Second, the car is typically designed in the knowledge that the difference between laden and unladen weight is not massive, and therefore, the braking ratios between the axles are much closer to being optimal than the truck axles. Yes, trucks are fitted with load sensing valves which can partially deal with changing loads, but, the compesation is not ideal.
So, in this case, Z is correct. Sorry Pat.
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Thanks Number Cruncher, but the matter in question is the ability of any other driver to make a judgement on how close, and indeed, whether they can stop or not.
It's the old scenario of lorries 'thundering through villages at 70MPH', when we all know they are limited to 56MPH.
Zero needs to take his tape measure with him on Saturday up the M6.
The uphill stretch just before Keele services is the best spot:)
Pat
Last edited by: pda on Thu 16 Jun 11 at 17:12
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We both know that some trucks do tailgate other trucks - it's quite common, and impossible to deny or justify. Effectively, the driver behind is placing his trust in the driver in front, and is generally safe in the knowledge that the truck in front can't and/or won't stop suddenly.
The thing is, if trucks didn't tailgate, they would spend longer in the outer lane, and this would upset some people (probably some of the same people hot under the collar about tailgating!), and from this point of view, I do sympathise - there's no winning!
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Its almost entirely down to speed limiters. You have to assume that every modern truck is capable of easily obtaining the max limited speed, which in turn is guaranteed to have lorries bunching into lorries, unable to overtake lorries and general mayhem
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>>Its almost entirely down to speed limiters
I tend to agree.
However, remembering back to the mid / late 80's where trucks were routinely doing silly speeds on the motorways, the justification for speed limiting was quite clear - effectively by not keeping to the rules, the industry had the solution forced upon it. In that sense, the industry got what it deserved.
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At the risk of being pedantic Zero, it isn't down to speed limiters, even though I hate them with a vengeance.
The odd cases of true tailgating that we see, are down to bull headed, bad driving by the lorry driver behind the wheel of the lorry.
Pat
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Thanks Number Cruncher, that was the point I've been hoping to make since I posted this morning but to make it without malice or willy waving.
That appears to be impossible if Zero's around, and the point he hasn't considered is that both drivers are usually chatting to each other on a CB anyway, so the one at the back has first hand knowledge of what's going on at the front!
It really is nice to talk to someone from the real world of lorry driving!
Just a quickie for you.....
I've spent many a mile on ice pondering over the fact that as I have 18 wheels, and 18 tyres to grip with, does that make me grip more effectively or not?
It's really been a 'how not to scare yourself' exercise and always worked:)
Pat
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>
>> That appears to be impossible if Zero's around, and the point he hasn't considered is
>> that both drivers are usually chatting to each other on a CB anyway
OFFS Pat, cant you see its you that makes this personal? like that very comment of yours.
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What is personal or wrong about a simple fact of our every day lives on the road.
We often run 'together', it makes the job easier, it makes the miles shorter, it makes the gossip better.
I wish I was still on the road, I'd take you with me so you can see what it's really like..
.. and drop you off in Scotland to argue with ON:)
Pat
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I know about the CB pat. I was illegally importing them and selling them to truckers in the mid 70's. I also earned a shed load of money legally importing Firesticks from phoenix, and fitting them in pairs to trucks, and teaching some of the drivers the lingo.
No I was referring specifically to this,
" that was the point I've been hoping to make since I posted this morning but to make it without malice or willy waving.
That appears to be impossible if Zero's around"
As personal.
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>>I've spent many a mile on ice pondering over the fact that as I have 18 wheels, and 18 tyres to grip with, does that make me grip more effectively or not?
The quick answer is yes. You're less likely to lose grip on all 18 wheels at once, and sharing the load out between all these contact points is beneficial.
As a tyre gets loaded up, although the amount of grip it can generate increases, it doesn't increase pro rata. This means, oddly enough, that the coefficient of friction is higher when the tyre is lightly loaded. So, if you lifted an axle, the remaing tyres would be more heavily loaded, and would have a lower coefficient of friction.
Ice and snow is a bit odd, however, as you can sometimes benefit from high tyre loadings being able to push into the snow and ice more effectively. Thin snow tyres "biting" through being the obvious example.
However, being a complete chicken, I would inform the agency I was not available for driving when there was any real danger of snow and ice.
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>>However, being a complete chicken, I would inform the agency I was not available for driving when there was any real danger of snow and ice.
<<
What a wuss:)
Good to know that I did right when I lifted my axle on ice, I was never quite sure but it sort of felt more secure.
Now, can you give me the answer to the eternal argument of the use of an exhaust brake on ice and snow?
So many arguments in so many cafe's and bars after a long day about that one, and we're roughly divided half and half.
Would you use one on ice and snow or not, from a technical point of view, of course?
Pat
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>>the use of an exhaust brake on ice and snow?
That's a much easier question.
The answer is leave the exhaust brake well alone.
The reasons are;
Exhaust brakes only brake the drive axle(s) - these axles are the ones you really do not want to lose grip on, especially on an artic.
Also, using an exhaust brake, the level of braking is not under your control, it's either on or off.
Compare this with gentle use of the service brake - the braking is applied to all axles, and the level is under the control of the driver, you are far less likely to come to grief.
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... is that both drivers are usually chatting to each other on a CB anyway...
The fact that numpty driver is further distracted by chatting to sensible driver on the CB is hardly reassuring.
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In your eyes that must make sensible driver a numpty driver too:)
I really do wonder how I ever managed a 30 year accident free record!
Pat
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...I really do wonder how I ever managed a 30 year accident free record!...
Same as the rest of us, by driving sensibly and safely, with a little luck for those occasional moments of stupidity.
Your record is more commendable than most because you have done many more miles than an average car driver.
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>> both drivers are usually chatting to each other on a CB anyway, so the
>> one at the back has first hand knowledge of what's going on at the front!
>>
>> >>
You can't be serious? It is safe to tailgate as long as you are talking to the driver in front and relying on him to tell you if he is about to slow suddenly?
The basic point seems to me to be inescapable - SOME lorries tailgate. Not all, not the highly trained and aware drivers like Pat, but just enough to ensure that whenever there is a major accident or sudden fog, lots of lorries shunt into each other because they can't stop in time.
That's not being being anti-lorry driver - car drivers are just as bad, or worse.
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>> Thanks Number Cruncher, but the matter in question is the ability of any other driver
>> to make a judgement on how close, and indeed, whether they can stop or not.
>>
>> It's the old scenario of lorries 'thundering through villages at 70MPH', when we all know
>> they are limited to 56MPH.
Pat, then my judgement stands. as i said If i know I cant do it I know you cant.
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>> Zero needs to take his tape measure with him on Saturday up the M6.
Would that be for the willy waving contest?
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I have invoked a foolproof plan to ensure there is no longer any strife between pat and I.
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Last edited by: Zero on Thu 16 Jun 11 at 17:19
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I have only been skimming this thread for fear of suffering collateral damage, but was amused by N_C's reminder that brake compensation for varying loads in heavy goods vehicles is less than perfect. I have watched many a lightly- or unloaded truck doing an emergency stop with smoking back tyres.
With an empty flatbed trailer, its rear tyres would sometimes get into a dynamic oscillation and draw one or two fat black dotted lines down the road, the trailer meanwhile bouncing up and down with a horrendous rattling and banging. Haven't seen many of those dotted lines recently. The fruit of technical progress no doubt.
I wouldn't mind being driven by either Pat or Zero (or N_C come to that) although they might not like driving me.
In the days when trucks in this country were governed to 38 mph, they used to freewheel down hills. Had a lift in one of those big chunky Tate&Lyle trucks once with a big chunky trailer to match, perhaps 30 tons or more of golden syrup or whatever in tanks, late night in East Anglia. I swear he was doing 70 at the bottom of some of those dips, where the village street always was.
Last edited by: Armel Coussine on Thu 16 Jun 11 at 19:51
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Mentioning older trucks reminded me about these pics which were scanned in (and so aren't brilliant quality). Here are some piccies of some of my father's trucks;
s949.photobucket.com/albums/ad338/Number_Cruncher_album/
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Sorry guys, its all my fault!
I have been trying all sorts of methods of saving fuel, from altering times I commute to work, to cycling 2 days this week to work, to sitting on the motorway at 56mph.
It was whilst doing this last one that I came up behind a lorry and the question came into my head of whether there was a point that I would gain, fuel wise. There was a point where I felt comfortable, and then another where I felt I was too close and would not be able to react on time, thus the initial question.
I seem to remember the last time Pat was having an open day at the yard, I posted a thread that ended with with her and Zero arguing on it! So all my fault but not deliberate - honest!
I think Zero hit the nail on the head with his recent post that the spped limiter on lorries causes more problems than it solves.
Pat I appreciate that lorry drivers need a certain amount of skill to do their job but you do sometimes seem to go overboard with the skills required. IMHO if it was a really skillful job, then surely it would attract a much higher wage and drivers wouldn't be working all sorts of hours to try and make a living from it?
Your note about all the factors a lorry driver needs to take into account, well, surely a car driver does the same? Is my load secure or are the kids not strapped in? Its wet so longer braking distances etc etc
Of course after a while it just becomes routine.
On a slightly different note, across all walks of life there are good and bad examples. We` all know there are bad lorry drivers, but there are also good. Same for taxi drivers, traffic police, cyclists. But every time there is a thread started regarding one of these, there will be a reply of you can't tell us when you (lorries, police, cyclists or whatever) are all so bad. Of course they are all not but that is just our perception.
If you had approached things slightly Pat and maybe said along the lines of "I am not excusing those idiot lorry drivers who think they can travel bumper to bumper" before making your point it would have came across a lot different than "car drivers think they know better"
Anyway, I think I, kind of, got the answer to my original question!
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is the point of tailgating to reduce ones contact with oncoming air resistance? if so then how does ones radiator work if starved of moving air? i imagine the electric fan would kick in just before the coolant boils putting more load on the alternator and requiring more fuel for the engine thus making any fuel savings null and void......or have i missed the point :)
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There's enough air still flowing through the radiator to cool it and because you're driving with a reduced throttle, you're not generating as much heat.
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>> IMHO if it was a really skillful job, then surely it would attract a much higher wage and drivers wouldn't be working all sorts of hours to try and make a living from it?<<
That remark has followed me around for the last 30 years and is probably the worst thing you can say to a lorry driver.
I sat for an hour early this morning and gave a long and exhaustive reply to you written primarily in a Word doc, to enable me to research facts and figures.
Word stopped working and I lost it.
I have searched the PC hoping to find an auto save copy to no avail, and have neither the time or the energy to defend my position to what I thought was a fair bunch of folk, with a pretty balanced outlook on life.
I was warned when I fist went over to the backroom almost 3 years ago that to mention 'lorry' was akin to committing forum suicide as no reasonable discussion would follow.
Sadly, nothing has changed.
Pat
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I cannot understand why some people get defensive about implied or imagined generalised attacks on their profession.
If someone attacks my profession I just think, yes, you might be right, and certainly are in some cases I could think of. But I'm not like that, nor are a lot of my colleagues, and that's all that matters. Water, ducks' backs, etc.
It's only personal integrity that matters.
It reminds me of the lines:
"Love thy country, wish it well,
But with not too intense a care.
'Tis enough that when it fell,
Thou its ruin did not share."
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Would the person who gave the thumbs-up to Cliff's poetry post care to explain what the verse means?
It's the last two lines I'm struggling with.
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>>>>
>> It's the last two lines I'm struggling with.
>>
Shall I give you my interpretation, or do you want to hear my admirer's first?
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...Shall I give you my interpretation, or do you want to hear my admirer's first?...
I suspect your admirer is finding the question too hard, so off you go.
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>> ...Shall I give you my interpretation, or do you want to hear my admirer's first?...
>>
>> I suspect your admirer is finding the question too hard, so off you go.
>>
>>
>>
It's always appealed to me because I thnk it is saying that there is a limit to how much one individual can take on the cares of a whole country, or cause. That ultimately we are only answerable for our own individual actions and motives, and that sometimes when everything crashes the best we have a right and duty to salvage and keep intact is our own honour and integrity.
Or may be not. It's an interesting idea anyway. I've no idea what George Bubb Doddington, Baron Melcombe, had in mind when he wrote the lines. Perhaps it was part of a longer poem, or a political statement referring to some current event.
Anyway, it seems to cover in a general sense my lack of deep identification with the "team" - football, profession, region, lifestyle, tastes, fashion, etc. I prefer to go it alone.
So coming back to the point, If I were a lorry driver and felt that lorry drivers in general were under real or imagined attack, I wouldn't care less.
Sorry, thread drift :)
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...I thnk it is saying that there is a limit to how much one individual can take on the cares of a whole country, or cause....
Thanks Cliff.
Were I forced to guess the meaning, it would have been along those lines.
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>> That remark has followed me around for the last 30 years and is probably the
>> worst thing you can say to a lorry driver.
>> Sadly, nothing has changed.
I've basically given up here, but will chuck in my tuppence in this case.
Twas always thus, truck drivers have always been regarded and treated as some form of low life by the ignorant, little wonder the negative attitude from many in our job that results from it....treat people as scum of the earth long enough, don't be surprised when they eventually become type.
A little while ago there was howling over the industrial action by Hoyer petrol tanker drivers, the prevailing attitude (with notable exceptions) from regular posters being that any fool can sit behind a wheel and drive a truck, so why should these unions fiends demand £35 or 40K for a job anyone could apparently perform better in their sleep.
They want their cake and eat it, they want skilled professionals who'll doff their caps and work all hours God sends for nothing, and be grateful..
The incompetent driving standards of some truckers witnessed these days is in many cases from non professional drivers. ie, those who had other jobs and who have obtained licences to drive trucks when their previous jobs ended.
It's always been the case that a 2 week become a trucker course at jack spot's driving school doth not a driver make, it takes years of hard graft and miles and a wealth of experience to get that seat of the pants competence that Pat speaks of, many will never become truck driver's despite driving trucks of a fashion for donkey's years.
Cruising down a motorway in an automatic truck is not truck driving, we see what happens when some of these clowns try to blind side manoeuver into a tight spot, or there's a bit of ice or snow involved.
I could go on for hours too.
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GB, skilled truck drivers are worth their weight in gold though unfortunatley, along with car drivers, bikers etc, there is a significant minority that are frankly dangerous.
I see them regularly, early this week I was coming out of a 30 limit in whch the road narrows and a big artic was thundering the other way at 50+, had I been another truck there would have been no room to pass and no time to stop.
Likewise trucks tailgating, or rather simply following a car too close, I see it regularly and experience it often in which case I usually ease of the throttle so the truck behind has to slow a little and then accelerate so as to open up a gap.
--
However I would like to explore the aero points made above further, around about my post dated Thu 16 Jun 11 @ 12:25.
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>> However I would like to explore the aero points made above further, around about my
>> post dated Thu 16 Jun 11 @ 12:25.
I've felt the draw of an equally bulky vehicle following close, there must be a subtle change to the flow of air at the back of the lead vehicle, but that could be buffet effect and not actually detrimental to the efficient progress of the leader.
As to car drivers slip streaming, it's only really dangerous if they become the filling in a truck sandwich, having seen the resulting 2ft lump of metal sandwiched between 2 artics that was previously a car, it's not the place to put oneself...doesn't matter how many ncap rating stars the car has either, all bets are off, trucks have no crumple zone.
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>> There's enough air still flowing through the radiator to cool it and because you're driving
>> with a reduced throttle, you're not generating as much heat.
>>
hang on the engines running at half( full bore) not sitting in a traffic jam, its generating kws of heat...no air flow means boiled engine THUS failure...and if air is flowing through the rad then the tow effect isnt happening...QED aurgument fail big time
Last edited by: zookeeper on Sun 19 Jun 11 at 02:43
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>>no air flow means boiled engine THUS failure...and if air is flowing through the rad then the tow effect isnt happening
Of course there's air, otherwise the engine wouldn't be able to run. You seem to think the 'towed' vehicle's sitting in a vacuum, that doesn't happen. The 'towed' vehicle sits in a complex, turbulent mass of air which is, generally, moving in the same direction and at a speed approaching that of the vehicles. The 'towed' vehicle doesn't therefore have to push its way through a mass of still air and receives a mechanical advantage. It's not a tow like you'd get on the end of a rope, just some assistance.
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>> IMHO if
>> it was a really skillful job, then surely it would attract a much higher wage
>> and drivers wouldn't be working all sorts of hours to try and make a living
>> from it?
Don't know about driving lorries but I know my wife does a very skilful (and physically and mentally demanding) job in NHS operating theatres, where lives are at risk. I sit on my backside all day writing code with no management responsibility. Her salary is less than half mine.
Last edited by: Focus on Fri 17 Jun 11 at 09:15
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>>
>> I think Zero hit the nail on the head with his recent post that the
>> spped limiter on lorries causes more problems than it solves.
>>
Not necessarily, since lorry design has have evolved to deal with it. Back in the day, when I was but a callow youth, if you'd got a 240hp Cummins coupled to a 9-speed Fuller gearbox, pulling 38 tonnes GVW you had a top-line truck. Limiters weren't heard of, so you'd be doing a steady 60 on the flat, with a bit in reserve for overtakes; on night runs where there were no bobbies looking even more, especially on a slight downhill grade. Unfortunately it all went pear-shaped when you hit an uphill stretch, as anyone who was a regular user of the M1 southbound through Leicestershire in the 1970's and 1980's can testify.
Nowadays 240 ponies would be considered only just sufficient on an 18-tonne GVW 4-wheeler, but the difference is that it takes a decent hill to necessitate dropping a gear at all. Our 44-tonne outfit has a 460hp engine with a 16-speed box, and that's on the low side; 480-500 is becoming the norm. The result is that lorries keep up a pretty constant speed on motorways, which given the higher speeds that modern cars are capable of maintaining (as opposed to reaching) must be a positive step where safety is concerned. The downside is that IMO it contributes to boredom for the lorry driver, which adds to driver fatigue and therefore has the opposite effect.
And I totally agree with GB's sentiments.
Last edited by: Harleyman on Sat 18 Jun 11 at 14:33
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>> anyone who was a regular user of the M1 southbound through Leicestershire in the 1970s and 1980s
It's still not uncommon to find the odd artic lumbering over the top at Charley only doing 25mph today! They do tend to come from further afield though, UK based wagons generally keep going no problem.
I had a similar problem in the early 90s, driving a 3.5 tonne Transit pulling a 2-tonne trailer - "powered" by only 76bhp. One regular run to the Forest of Dean featured a short sharp hill that called for a change down to 1st gear to avoid stopping! The usual ascent speed there was under 10mph.
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Lorry slipstreaming - Zero
