richmond:
So where will i end up, 4.7m wide,30m long, but a gross weight of 30t…, i know, still cream crackered…
damoq:
In normal language, I think what he is trying to say is, if you are pulling a loaded decker, without a sloping roof and you have no air deflector on your tractor you are pretty much screwed if you go over 40mph in the hope of getting 12mpg.
Basicly, the flat front fo trucks does them no favors, although some seem to be addressing this with the slightly sloping windscreen.
Air deflectors providng they are the correct hight for the trailer will make a big diffrence to MPG as will the tear drop type trailers
For air deflectors on the cab roof to work, there has to be a very small gap between that and the front of the trailer. If it is more than 50cm or so then it is doing more harm than good.
Well where I do most of the driving the law is 80km/h and so is company policy. Company MPG target was 9.0 mpg, but someone saw sense and revised this to 31.0l/100km (speed limits are in km/h, clocks are in km/h, trip computers are all metric and I fill the tank with litres).
I was driving one particular truck the other week and despite grossing 27 tonne, driving it gently it did a dismal 32.3l/100km (8.7mpg) that shift. Same truck, following week, similar weight, similar route. The only things different were a) on the way out, I stayed on the motorway and incurred two tolls (instead of going through every one-horse village on the old road roughly parallel) and b) set the cruise at 75km/h (as I had spare time). Ended the shift on 29.0l//100km (9.7mpg). For the approx distance, I saved 8.75 litres (around €13 but clocked up €6.60 in tolls)
That truck was the donkey of the fleet and I told them so (I think a) the engine management wants looking at and b) the fifth wheel moved forward, there’s quite a gap with fridges). Given any other one and I can manage (with the same everything) 25-27l/100km (10.5-11.3mpg).
A couple of things I do, when heading down a hill, I’ll know the (80km/h) cruise off as the retarder kicks in at 5km/h over the set speed. I let over run without tripping the tacho overspeed. Also might do over 80km/h where the law permits.
Here’s an old example of a good day, mostly motorway, grossing about 26 tonnes for half that distance - (42.4mph /11.4mpg / 311 miles)
AHT:
If you just want to get good MPG then basicly the slower the better given that most of the energy used is wasted as air resistance (providing you are with in the efficient working limits of the mechanical parts) so probably around 30-40mph,
In terms of family car drag coefficients the fuel consumption increses exponentialy with speed, once you reach speeds above 50mph the fuel consumption increses drasticaly.
For a truck with the far less aero dynamic shape i would say the tipping point is about 40mph
the formula for drag is below
Drag force = (1/2)p(v^2)Cd*A
As you can see speed v is squared hence the exponential increse
Cd is the drag coefficient witch is dependant upon the shape(I am a mechanical engineering student BTW looking for HGV work to fill up my spare time (and because I enjoy driving))
“The cost of fuel is about to rocket”
What you didn’t state, AHT, is that the power needed to overcome drag is proportional to the cube of speed because if you are going twice as fast you are doing the work (in this context Force x Distance) in half the time. So, basically, if you were to go twice as fast you would need 2x2x2 (8) times the power, but you would get there in half the time so you would only have used 4 times the fuel overall. What this means is (all other things being equal) e.g. you need 2.25 times as much fuel to do 60 compared to 40 (but you would get there a third quicker if you could!) - and of course time is all-important nowadays. Tesco would get a theoretical reduction in fuel of ((9090/(8080) = 1.265) c. 26% by restricting their vehicles from 90KPH tops to 80KPH. 47 MPH is supposedly the most efficient. I am too lazy/thick to check these figures but I challenge any of our regular readers to prove I am wrong!
Snudger:
AHT:
If you just want to get good MPG then basicly the slower the better given that most of the energy used is wasted as air resistance (providing you are with in the efficient working limits of the mechanical parts) so probably around 30-40mph,
In terms of family car drag coefficients the fuel consumption increses exponentialy with speed, once you reach speeds above 50mph the fuel consumption increses drasticaly.
For a truck with the far less aero dynamic shape i would say the tipping point is about 40mph
the formula for drag is below
Drag force = (1/2)p(v^2)Cd*A
As you can see speed v is squared hence the exponential increse
Cd is the drag coefficient witch is dependant upon the shape(I am a mechanical engineering student BTW looking for HGV work to fill up my spare time (and because I enjoy driving))
“The cost of fuel is about to rocket”
What you didn’t state, AHT, is that the power needed to overcome drag is proportional to the cube of speed because if you are going twice as fast you are doing the work (in this context Force x Distance) in half the time. So, basically, if you were to go twice as fast you would need 2x2x2 (8) times the power, but you would get there in half the time so you would only have used 4 times the fuel overall. What this means is (all other things being equal) e.g. you need 2.25 times as much fuel to do 60 compared to 40 (but you would get there a third quicker if you could!) - and of course time is all-important nowadays. Tesco would get a theoretical reduction in fuel of ((9090/(8080) = 1.265) c. 26% by restricting their vehicles from 90KPH tops to 80KPH. 47 MPH is supposedly the most efficient. I am too lazy/thick to check these figures but I challenge any of our regular readers to prove I am wrong!
I challenge any of our regular readers to understand it, let alone prove him wrong !lol
I continued my studies today whilst running empty and noticed that I was uing slightly more fuel than when I was loaded yesterday. Although this sounds odd, the load yesterday weighed about 2t and comprised 2 stacks of solid metal fence panels that were about 3’ high each stack.
Running a beavertail with no sides I’m guessing there is a low pressure area behind the cab, I’ve had the roof hatch open before and had a dumper against the headboard and had fine grit and dirt sucked in through the top. Perhaps having the panels there made a less turbulent area.
I’m thinking that those short height curtainsides that block wagons have would also make a noticable difference to the fuel consumption, when we looking at buying a new wagon with a new body I suggested that we had these fitted so that I would have some lightweight sides for moving site materials, these could have been signwritten for extra presence and rolled up and stored when not in use. I thought it was a great idea, but it got crossed off the list. Although we ended up with a second hand vehicle so it didn’t matter anyway.
Tipper drivers are told to keep the body sheeted; This works if it’s a complete coverage sheet (like Hanson lorries do) but our front to back ones (the ones with the arms sticking out) I’d say make no difference as there’re gaps down the sides.
You don’t see so many ribbed bodies nowadays either…
There’s just no extra pleasure to be had anywhere these days. 
richmond:
Snudger:
AHT:
If you just want to get good MPG then basicly the slower the better given that most of the energy used is wasted as air resistance (providing you are with in the efficient working limits of the mechanical parts) so probably around 30-40mph,
In terms of family car drag coefficients the fuel consumption increses exponentialy with speed, once you reach speeds above 50mph the fuel consumption increses drasticaly.
For a truck with the far less aero dynamic shape i would say the tipping point is about 40mph
the formula for drag is below
Drag force = (1/2)p(v^2)Cd*A
As you can see speed v is squared hence the exponential increse
Cd is the drag coefficient witch is dependant upon the shape(I am a mechanical engineering student BTW looking for HGV work to fill up my spare time (and because I enjoy driving))
“The cost of fuel is about to rocket”
What you didn’t state, AHT, is that the power needed to overcome drag is proportional to the cube of speed because if you are going twice as fast you are doing the work (in this context Force x Distance) in half the time. So, basically, if you were to go twice as fast you would need 2x2x2 (8) times the power, but you would get there in half the time so you would only have used 4 times the fuel overall. What this means is (all other things being equal) e.g. you need 2.25 times as much fuel to do 60 compared to 40 (but you would get there a third quicker if you could!) - and of course time is all-important nowadays. Tesco would get a theoretical reduction in fuel of ((9090/(8080) = 1.265) c. 26% by restricting their vehicles from 90KPH tops to 80KPH. 47 MPH is supposedly the most efficient. I am too lazy/thick to check these figures but I challenge any of our regular readers to prove I am wrong!
I challenge any of our regular readers to understand it, let alone prove him wrong !lol
There is a point where,assuming that there’s enough work out there,going slower to save fuel gets cancelled out by the loss of productivety.It makes no sense at all to provide modern wagons with 10 hp per tonne and then drive the things around at 48 mph max and it’s also why the Americans decided to ditch the 55 mph federal speed limit.
I think the ideas of driving trucks at ever slower speeds is just a desperate attempt to compensate for impossibly high fuel costs and reflects the fact that there’s not enough loads to carry over enough miles.
10bhp/ton? I think that died out with Gardner Turbos 
I’ve got 345bhp at 26t.
ive noticed with our scannys the older one does alot better sitting at 55mph and gets 11.5 mpg constantly although it still has the wind deflector on the roof where as my newer 57 plate prefers sitting at 50mph to get the same mpg if i sit at 55 it drops down to 9.8mpg
mind you its not much use trying to get a decent mpg figure as once the pto goes in for the crane they both drink derv like oliver reed in a free bar 
AHT:
If you just want to get good MPG then basicly the slower the better given that most of the energy used is wasted as air resistance (providing you are with in the efficient working limits of the mechanical parts) so probably around 30-40mph,
In terms of family car drag coefficients the fuel consumption increses exponentialy with speed, once you reach speeds above 50mph the fuel consumption increses drasticaly.
For a truck with the far less aero dynamic shape i would say the tipping point is about 40mph
the formula for drag is below
Drag force = (1/2)p(v^2)Cd*A
As you can see speed v is squared hence the exponential increse
Cd is the drag coefficient witch is dependant upon the shape(I am a mechanical engineering student BTW looking for HGV work to fill up my spare time (and because I enjoy driving))
You also have to take into account rolling resistance and mechanical drag, at speeds up to 55mph rolling resistance is the number one enemy to fuel economy, over 55mph aerodynamics take over, and as speeds increse more of the energy produced during combustion is lost in the process of turning the moving parts in the driveline, friction and oil churn being major sources of energy loss. Simple physics suggest that the slower you go the easier it is on the engine, optimum speed for maximum efficiency is around 42mph, with the engine turning at the lowest point on the specific fuel consumption curve and in a direct gear (1:1 ratio) not much use in the real world though
Testing has proven that, with all other things being equal, a 1mph reduction in speed will bring a 1/10th mpg fuel saving on aerodynamic efficiency alone, add the other factors and dropping from 56mph to 50mph could get you an extra mpg. I know some of you have experienced far greater savings, but there are so many variables, wind direction, the friction coefficient of the road surface and a million other factors, that you can’t work out savings off the dash readouts, sure it’ll give a rough idea, but you’ll need to drive everywhere at the reduced speed for at least a week to get an accurate picture
it takes longer to get there at a lower speed, so the truck earns less, therefore it will make no difference.
I am razzing around in a chipped and remapped volvo FH that is limited to 59 mph and always pulling 44t. Just over 6mpg average, my boss doesnt seem to mind as long as I get all my loads done without cooking the engine!
SwedishSteel:
I am razzing around in a chipped and remapped volvo FH that is limited to 59 mph and always pulling 44t. Just over 6mpg average, my boss doesnt seem to mind as long as I get all my loads done without cooking the engine!
Is it turquoise and red 
SwedishSteel:
I am razzing around in a chipped and remapped volvo FH that is limited to 59 mph and always pulling 44t. Just over 6mpg average, my boss doesnt seem to mind as long as I get all my loads done without cooking the engine!
6mpg. it’s [zb]ed. i’m 1mph behind you and getting 9mpg, but that’s in a proper lorry.
richmond:
I am very interested in this at the moment, with the cost of fuel about to rocket, but what is the optimum speed, i dont want the guys to crawl around, but with no hope of any rate rises, the only option is to try and improve the mpg, we run fh 12420 and 460 and man, a 440 and a euro 3 460.I think this will be crucial in the coming future, one truck last week cone £1500 in fuel, single shifted, anything to improve will help.
First off ditch them tall trailers that are not realy needed and run with 4.2m trailers,Give me a 4.0m euroliner send me over the water for a few weeks at a time where im not stopping and starting around the m25 all day and my mpg will have improved…And then hurry up with my scania for gods sake man 
Fatty, im sure your tpt manger often thinks, nay dreams of sending you away, over the water for weeks at a time …
richmond:
Fatty, im sure your tpt manger often thinks, nay dreams of sending you away, over the water for weeks at a time …
Now that is slanderous accusing the tpt manager of thinking he would be appuled…I need to be away as the dulsid tones of my boss is making me feel suicidle