I'm about to move our furniture in a 7.5 tonne lorry, to a house where access is across a cattle grid. The cattle grid looks very iffy - some bars have already bent slightly.
Does someone know where I might be able to hire one of those big metal plates (a cm or more thick) which contractors use when they're doing roadwork? I mean the ones which, when they've dug a hole outside your driveway, they put on top of the hole to let you get in and out.
Cattle grids are designed to cope with all normal road traffic. You might just trouble an old one with an HGV but a 7.5 tonner won't even be an issue. The minimum British Standard even for private driveway use requires them to cope with oil delivery tankers up to 26 tons. Highway spec ones will cope with much heavier vehicles. If the bars are bent on yours then maybe something really extraordinary once went over it but it'll still be ok for a small truck.
Even if you could hire a plate as you suggest it would weigh a ton - literally. An 8' x 6' x 1 inch steel plate would be about 850 kg. You'd never move it without a crane and I can't imagine the hilarity which would ensue if you phoned up someone and asked them to deliver, put down and then take away a plate over your cattle grid because you thought your little furniture truck might fall through it.
Would it be easier to get hold of 4 railway sleepers and bolt a pair together side by side on short face for each axle? Then at least when its done you can use them in the garden afterwards.
I expect if you go into a hire shop and ask for a flat plate to go over a hole they'll look at you as if you have just landed from another planet.
Scaffold planks or similar would be my first guess too - wood is appropriate for that sort of one-off.
Though as Dave says, is it just fretting over nothing? How iffy is "very iffy"? I know to some people that means the entire thing is at the point of collapse, with bars rusted through and the supports crumbling away. But a slightly bent bar is no way near that.
Also, don't forget that the cattle grid is there for a purpose - if some poor farmers livestock escape or are harmed by traffic it'll be you picking up the tab. Remember - sheep are in lamb at the moment so even slight disturbances can dramtically increase the still born rate.
Thanks for this - I had no idea there was a British Standard covering cattle-grids on private driveways, but I've seen several in rural areas that are home-made. I actually watched one at a house we used to own get its bars bent by a removal lorry. After that, even the postman was afraid to drive his van across it, and eventually I had it removed, filled in the pit, and put up a gate. As for the oil delivery tankers, they always waited outside when pumping the oil in!
It's at my sister's house and on her land at the start of her driveway, and there's a gate too. No chance of endangering any livestock. I will have to ask her about the oil lorries. If they do go across it to refill her oil tank then I'll be OK.
A lot of electrical white goods etc are delivered using large vans. If it has been crossed by an oil tanker it should be OK. If not better be checked before a vehicle gets damaged and a claim results. Liability insurers require that property be properly maintained.
There's a British Standard for just about everything if one does but know where to look them up. If this government we're afflicted with has its way there'll be one for taking a dump soon and we'll all have microchipped intelligent toilets to make sure we're dropping regulation size turds that won't block the drains.
Anyway, back to cattle grids. The issue is of course not total vehicle weight but axle loading given that with a normal length cattle grid only one axle, or maybe just two, will be on it at a time. Even if it is long enough to have two axles on it they'll be close to either end and so not such as an issue as weight in the centre. The biggest risk of bending is therefore 3 axle oil tankers which can mass 26 tons in total and 10 tons per axle. 40 ton HGVs will usually have 5 or 6 axles and a lower mass per axle than the smaller vehicle. A twin axle 7.5 tonner won't have more than about 4 tons per axle. Almost inconsequential compared to what might drive over one of these.
If you're worried even a 1" wooden plank will spread a considerable amount of load amongst adjacent spars of the grid. So will dropping the tyre pressure of the vehicle because it's tyre pressure that determines the contact patch size and point loadings. If the tyre pressure is 100 psi then there must be at least 100 pounds per square inch pressure on the ground. The tyre sidewall stiffness itself can only add to that. The biggest risk comes from a heavy vehicle with very high tyre pressures so that the tyre is effectively solid and all the mass is concentrated on one spar at a time. Lower the pressure and the contact patch will change to a longer one which will intersect more than one spar at a time. Do both, plank plus lower tyre pressure, and you'll float over it like a fairy tripping lightly over marshy ground. However don't even be worried. Your tiny truck won't hurt it.
The fact that there is a British Standard is almost irrelevant. I would be surprised if more than a tiny fraction of cattle grids on private land had been designed in strict compliance with that standard.
There is already a British Standard Turd for testing toilet flushes. However, it looks nothing like a turd (more like a solid rubber tennis ball) which is presumably why water-saving toilets that won't actually remove a real one with one flush can still pass.
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