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I realise that cars which travel crab-wise do so because of misalignment/mispositioning of one or more of the wheels, but what causes the misalignment/mispositioning in the first place? Is it manufacturing tolerances, accident damage, or incompetent assembly?
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I knew a chap who rolled a TR6. Repaired, but crab-like ever more. The car, not the chap BTW.
Edited by nick on 04/11/2008 at 09:29
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Due to some sort of optical illusion, I always think 911's are 'crabbing' when I follow them. Next time one overtakes you on the motorway, or you get chance to follow it from behind and to one side, have a look. It's really quite remarkable.
Something to do with the marked difference in front/rear track perhaps.
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And crabbing Minis (the old little ones) used to be quite a common sight. Usually due to faulty rear subframe IIRC.
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Crabwise is nothing:
uk.youtube.com/watch?v=B3O_S0FMuYU
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Artic trailers frequently.
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Artic trailers can often look like they're crabbing because from following driver's viewpoint, they're seeing the trailer from an off-centre viewpoint.
However, sometimes artic trailers and rigid lorries do crab because of misalignment of rear axle(s),
When I used to drive grain lorries I turned up at a mill behind a 6-wheel tipper whose 2 rear axles were way out of alingnment, transversely - one axle offset to left, other to right. The driver had made a tight turn and the axles had shifted in their U-bolts!
Edited by Sofa Spud on 04/11/2008 at 10:59
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Ive also seen a few Transit tippers doing this, either builders ones or scrap mans, clearly overloaded.
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Marvellous what you see nowadays. A snail writing about a crab.
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Could be RAF personnel returning to base?;-)
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I was in a small Japanese long-distance bus in Kenya once when the shackles holding the axle to one of the rear leaf springs came loose and the axle shifted causing the bus to crab. The driver and his henchman did a running repair while everyone else stood around gazing over the Rift Valley as the sun went down. Took about five minutes, but stopped for longer in the next town to do the thing properly.
Only in the third world does one find real genuine gritty old-time motoring. I often miss aspects of it, but it would certainly pall quite quickly if one was stuck with it without very substantial means.
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I saw an MGF doing this once, so badly I was moved to report it to the police. Dunno whether they did anything about it, mind.
Actually, to be more clear, what led me to report it was the drivers incapability of taking account of the crabbing, and the way they therefore swerved violently into the verge or across the white line at various points in their journey.
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I recently followed a large lorry mounted crane along a fairly narrow well cambered road. Gravity took over, and his N/S rear wheels were dragging along in the gutter - his O/S front wheels on the road centre line. Completely blocked the road, but I could only admire the driver as he negotiated parked cars and other obstructions.
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I recently followed a large lorry mounted crane along a fairly narrow well cambered road. Gravity took over and his N/S rear wheels were dragging along in the gutter - his O/S front wheels on the road centre line.
Are you sure he didn't have rear-wheel steering? It's quite common on large cranes (and increasingly on HGV's) and to the uninitiated it does look like the vehicle's crabbing.
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Harleyman, there was no rear wheel steering on this crane. I could see the rear tyres scrubbing as they slipped towards the kerb and transmitted the drive.
The driver did a superb job controlling the the thing, it really was as though the back end (heavy) bit was influenced more by gravity than anything else.
I suppose it was heading for a job and this particular (unsuitable) road was the only way there. I guess that this sort of slippage goes on whilst they're hurtling down the motorway at 30mph but isn't a problem as there's more time and space to correct things.
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