I was wondering... How do gritting lorries get grip? Almost by default, they are travelling along roads which need grit or salt and (this is the daft bit) the grit is shed behind them. I envisage a team of two workers, standing on a platform built onto the front of the truck, shovelling grit/salt under the wheels as it goes, much like the sand boxes on steam locos. ;)
They sometimes don't and slide off the road or get stuck in drifts.
Remember along with the salt they are putting out the back they also have a plough on the front, there might be 2' of snow(*) in front but where the wheels are less than an inch. Our ploughs have very knobbly tyres with tread depth aroud an inch.
(*) 2' of wet sticky snow may well stop a plough or at least give it something to think about. Same depth of dry snow won't be a problem. I'm thinking of a plough with a pointy blade not a straight shove it to the nearside one. They also use momentum to get through drifts,
Road grit needs to be put out before the ice forms for best effect.
Colin Bignell
That as well, it's not really grit either but lumps of dirty salt. It takes time and traffic to melt the snow/ice. You can grit onto a ploughed surface but if there isn't much traffic it won't have much effect. You need the traffic to mix the salt into the snow/ice/slush.
Four wheel drive and dif lock axle
Snow tyres? And chains if really bad.
It's the wrong question. As other have answered it, I'll go no further, but the real question is, when the weather is unexpectedly bad and gritting hasn't started in time ... how do the gritter drivers get to work?
SteveW
BBC News have just shown an image of one on its side...
Ours walk... anyway there is no reason for "unexpected bad weather" forecasts out to 24 hours a pretty good and at 6 hrs accurate.
They're nearly always 6x6's over here (the wilds of Minnesota) with very deep treads on the tyres. Always combined plough / spreader trucks.
Every once in a while they'll send a grader through too; I'm not sure if they just call on those when the ploughs are running flat-out, or if there's some function they do that the ploughs can't (they never have grit spreaders on the graders, so they just clear snow/ice)
As Colin says, getting grit down before the ice seems to be key - and then repeating as much as necessary (they'll usually do a run past our place at least once a day, whether it's snowing or not)
cheers
Jules
Do they have a fleet of 4x4 work vehicles that the drivers get to borrow and take home? You can get through pretty much anything that nature can throw down with a 4x4, albeit sometimes slowly.
Then they don't get to work on time and the roads do not get gritted in time.
This is then followed up in the newspapers with stories from annoyed motorists blaming the council for not gritting the road and how they had "to walk and it's so unfair I pay my council tax etc etc"
Adam
Steve Walker gurgled happily, sounding much like they were saying:
A friend of mine looked into getting on the on-call gritter-driver rota for his local council.
The answer is "They've got to be able to walk to the depot"...
And about 11 tons of weight when full.
And it's usually new-ish snow, which even my dear old Corolla can have a go at, when it hasn't been mixed and polished by a lot of other cars.
(Aside, and apols to cross-group colleagues): I asked in the uk.rec.cars.maintenance group which car would be better for snow: our Corolla or our titchy Suzuki Alto (which has tiny wheels). The consensus was that little wheels go better. Hmmmmmmmmmmm I thought. On the days when I've braved the roads I've stuck with the heavier, wider-wheeled Corolla. (And the main answer was: if you're a crap driver, it doesn't matter which you use. (Fortunately I'm a brilliant driver -- as any fule kno.))
John
I've been checking the forecasts here regularly over the last few days and for our area they've been universally wrong. On Monday night they were forecasting intermittent snow showers and rain - while this was still the current forecast, it started snowing heavily and two inches arrived. Through the rest of the night, another six inches arrived (no rain). In the previous couple of weeks, we've got snow when the forecast said it was going to be dry, heavy snow when it's supposed to have rained, etc. We basically seem to be better off if we plan for any sort of weather at all, except what they're forecasting :(
SteveW
I saw one on its side today.
Living in a snowy part of the world, that subject gets discussed a lot. The general conclusion is usually that it depends on the type of snow; wider tyres with low pressure can be suited to certain types, but thinner tyres can do better on other stuff.
RWD does better than FWD, and 4x4 does better still. Tracks are even better :-)
cheers
Jules
Perhaps this also depends on the type of snow but from what I've seen RWD cars (mostly BMWs) seem to have a lot more trouble than front wheel drive.
That's down to the drivers of BMW's not RWD. B-)
Yes, the float or dig difference.
Big wide tyres and lower ground pressure will reduce how far you sink but at the expense of not reaching the tarmac so you have to rely for grip on whatever the tyres to surface can do. Narrow tyres will tend to dig down and find a firmer surface, if there is one or you might did to far...
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