There I am, pootling at 50MPH in my diesel, slipstreaming lorries.
Setting aside stories of amazing MPG's for the moment, does the lorry work harder in front pulling along someone behind? My guess is that filling the low pressure hole behind might even help the front half a little. I'm sure roadie bikers will have a feel for this one.
apparently a slipstreamer helps the car/bike in front
On a road bike you don't really feel a benefit but in cars, if you're going fast enough and you're close enough together, the car in front will go faster/use less fuel - filling in the low pressure hole as you suggested helps reduce drag effectively it makes the car/truck in front more streamlined.
The two vehicles essentially become one longer vehicle, so possibly less drag for both.
its minimal, your saving your 30-40%, he probably barely notices as he's already measuring economy in gallons per mile.
Wouldn't you have to be really too close for comfort thou, you know in a car?
Yes - this is something that works for racing cars on an oval - not so good on the motorway though I think that lorries do seem to be trying it...
I wonder if this will be a development of the forward facing radar thingy that Volvo and some others seem to have developed. I could imagine a version for lorries that keeps them x meters away from the lorry in front and automatically brakes the vehicle if the vehicle in front slows down.
"Wouldn't you have to be really too close for comfort thou, you know in a car?"
Yes and no. To get the maximum out of it very definitely yes.
If you are sensitive to the car, you can feel the air pressure drawing the vehicle forwards from as much as 30 metres behind. 20 is much more obvious and rather more dodgy, any less would work brilliantly for anyone silly enough to take it further (not me). But at 50MPH in quiet dry conditions whilst the lorry itself has nothing in front of it, then I can personally sometimes take a risk at about 20M, and a MPG hound can still get a clear benefit.
Theoretically you should be able to stay fairly close to a lorry in front if you keep aware as a car should always out-brake a lorry. The question is would you really want to? 
Theoretically you should be able to stay fairly close to a lorry in front if you keep aware as a car should always out-brake a lorry. The question is would you really want to?
There's the small matter of your reaction time to consider as well....
Further more, lorries slow down pretty rapidly when they crash into other lorries or walls etc
That is one small snag. Roadies don't seem to care though. It's all about PERFORMANCE 
The lorries do it. You'll see them sandwiched together in a convoy in the inside lane. The lead lorry will be on the CB keeping them updated on the traffic ahead. They'll take turns as the lead.
Slipstreaming a bus at about 25mph on the bike is tremendously efficient if you can handle the exhaust fumes...
This was covered in an episode of Mythbusters.
IIRC you had to be about 10-12 FEET behind the truck at 50mph for maximum benefit but there was an improvement in economy for the rear vehicle from further back.
Theoretically you should be able to stay fairly close to a lorry in front if you keep aware as a car should always out-brake a lorry.
Empty lorries and buses will slow down just as fast as a car. It's only when they are loaded that it becomes harder to stop. The front of the car will still stop before it reaches the front of the lorry though 
Having been the victim of an extreme tailgator, it does make a different, almost like you've left the handbrake on a couple of clicks and just released it.
When they undertake you and the traffic ahead its also scary how much the pressure change can make your car swerve as their front wing passes within a foot of your rear wheel!
Mythbusters did a feature on tailgaters, but not the effects on the lead vehicle... interesting thought though.
oops double post, sorry.
so if an hgv is towing a plane on a conveyer belt will it take off more or less easily or not at all?
IIRC when the British track cycling team looked at the efficiency of the team pursuit positions, three came out the best.
A double shielding effect from one and two and four to smooth out the air behind them, so there appears to be some benefit. The figure was something like 60% of the energy required to ride in position three compared to position one.
Matt
so if an hgv is towing a plane on a conveyer belt will it take off more or less easily or not at all?
Wouldn't move, let alone take off 
your MPG is also probably greatly improved by being forced to stay at 56mph.
i know if ive ot a clear run ahead of me, i get a twitchy right foot, in average speed sections, i have to sit behind someone, to stop myself creeping up to NSL.
"your MPG is also probably greatly improved by being forced to stay at 56mph."
Very true. Over the weekend I was maxing out big time in a sort of personal contest, because I wasn't in a hurry (visit to the in-laws!). I could make only 76 MPG till I sat behind a few lorrries and it went up to 84. In the end I achieved a return trip of 273 miles on 16 Litres of diesel which is average 79MPG. The parts I was slipstreaming were clearly about 8MPG better than the parts when I was just cruising at 50-55MPH.
I have small children.
I'm more than willing to pay hard cash to get somewhere even slightly quicker but with a reduced mpg.
If they complain later about inheriting a planet that's too warm I'll blame them for asking 'Are we there yet?' at 5 minute intervals throughout every car journey they ever went on.
One of the lorry companies was working on a radar system a while back that would allow lorries to form large 'trains' the front lorry would guide the ones behind and keep all the lorries in the 'train' a constant distance from each other.
Seems to work fro NASCAR racers, but they do run almost touching, at 200 odd mph.
I do not understand it, if you crash once through your own miserly stupidity it will take 24.11 years to gain you cash back (assuming average car and mileage and you do not crash again owing to being a stupid miserly feckwit).
i know if ive ot a clear run ahead of me, i get a twitchy right foot, in average speed sections, i have to sit behind someone, to stop myself creeping up to NSL.
cruise control is your friend here,
+1 Best optional extra on any car I think.
regularly used to drive work trucks within inches of each other, nothing to do with fuel economy just for the fun of it and the interesting rub marks, in these situations our consumption was probably worse, but that may have been the other pissing around
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