how does TX4 taxi achieve tight turning circle?

London taxis are supposed to have a 25-foot turning circle. Other RWD cars with same wheelbase would have turning circle over 30 feet. I am told the Chinese-made TX4 does achieve this tight circle as it uses a different steering rack. I had assumed that the front wheels were turned more than other cars, and it has narrow tyres that would allow this. I looked at videos of the taxi and front wheels only seem to twist about 45 degrees on full lock. Fork lift trucks twist wheels more than that. I have also seen an old LWB Bentley whose front wheels twisted more. Is the front end setup with some unusual combination of camber and scrub radius or whatever that permits tight turns? I would presume it is something others avoid as it increases tyre wear or degrades handling.

Reply to
bruce56
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Yep. The reason why? Scroll down to vehicle design:

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A friend once owned an ex-London taxi as a cheap runabout. They don't handle, and they do wear their front tyres fast! At the age his was, they were not allowed to have lockable rear doors. His solution was to tie them together inside...

There is nothing special about the steering arrangement, apart from being very old-fashioned on even the latest models.

Chris

Reply to
Chris Whelan

It was probably on crossplies which accounts for both...

They had 16" wheels in the days when 15" was about the largest common size so radials for them were rare and expensive. They also made the steering even heavier - before power steering arrived.

Reply to
Dave Plowman (News)

yet the new nissan taxi will have 14 inch wheels, bizarre.

Reply to
Mrcheerful

I'd guess they've relaxed the regs? (At one time all chassis nuts had to be wired - and so on)

Reply to
Dave Plowman (News)
[...]

Yes, partly due to the somewhat bizarre requirement to have a minimum of seven inches ground clearance.

Chris

Reply to
Chris Whelan

A quick google reckons not - the NV200 van's had the suspension raised to meet the ground clearance requirement.

What's most interesting about it, though, is that it meets the turning circle requirement - despite being FWD, and without having to resort to the rear-steer of the Merc Vito taxi (RWD). Any bets on how long the CV joints are going to last?

Reply to
Adrian

ten according to the nv200 specs

Reply to
Mrcheerful

Apparently only up until 1927 ;-)

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Chris

Reply to
Chris Whelan

The Triumph 1300/1500 FWD had an excellent turning circle. They achieved this by angling the driveshafts. Not quite as good as the Herald, but close.

Reply to
Dave Plowman (News)

It was required to have that turning circle so they don't have to do 3 point turns to collect a fare on the other side of the road. AND it's wall to wall turning circle - that wall will be a wall of people on the pavement.

While these days the local "taxis" bring the A511 in Burton on Trent to a halt doing a 3 point turn. 20m away from a nice quiet side road where they could that other "quiet road" driving test standard "reversing round a corner".

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1: Fabricated lower "A" arm with very curved front tension arm bolted to front of the lower arm. Normally the tension rod would be straight - it will tend to bend straight every time it brakes. 2: Lever arm steering with whacking long lever. 3: Lots of neg camber! 4: Upper A arm very high in a big wheel with a very small base at the chassis end.

So the answer is by having utterly shit handling.

Kerb to kerb you can deduct about 1-2ft.

Triumph Spitfire had 24ft - kerb to kerb?

72 Datsun 1200 coupe 26 ft, 4 inches Herald 27ft. 31.1ft (9.5m) does me and my 200SX just fine. Don't get many cars with that sort of turning circle any more, most are around 36ft (11m). MX-5 is about the only one and that's an impractical 2 seater.

On this claimed "TOP 10" list only the Yaris has a decent turning circle

- which means it's easy to park, either in short spaces when parallel parking or in car parks with narrow lanes between the rows. Yaris may be as good as the old Mini for turning circle. Old Mini had mods very early on as it was so crap when first produced they had to FIX it, while the NEW Mini is hopeless.

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This list starts off well with Smart Four2 28.7ft and Fiat 500 30.6ft, then they mess it up by claiming the 35.1ft Mini Copper as "good". Oops.
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Utterly clueless as what a "good" turning circle is or the value of it. What do you expect?
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A bunch of barge owners prove to be yet more clueless idiots.
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None are better than 35ft.
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While the Volvo 740 one mentions is a whole yard less at 32ft - it makes all the difference between a kerb to kerb or a 3 pointer becoming a 5. That C70 has to be wrong, how have they gone from fairly good to that sad joke at 38.4ft? Lost all their design rules, values and integrity under Ford ownership? Link below V70 seems to have a much bigger turning circle for Auto 40ft compared to Manual 36.7ft. Is it restricted by gearbox to wheel clearance? Both are barges.
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And when it comes to skidding the RWD car with most opposite lock and a back axle that doesn't throw a fit about it wins.

Reply to
Peter Hill

In the 1960s, oil millionaire Nubar Gulbenkian drove about in a custom-built gold and black taxi. He once exclaimed "It can turn on a sixpence - whatever that is."

Reply to
The Revd

The NV200 taxi has an extra universal joint to allow the increased angle. So the drivetrain is Cardan plus Birfield plus odd number of uni joints. Will no longer be constant velocity. I reckon it must wobble a bit going around the Savoy.

Reply to
bruce56

And as for the Merc London taxi, they used 4-wheel steering to achieve the 25-foot turning circle. So it probably has good handling, but must be fairly expensive.

Reply to
bruce56

Volvo 700 series was RWD. C70 is FWD. Usually the difference in turning circle is less than 4.7 feet.

Reply to
bruce56

Gosh, did they?

Reply to
Adrian

Well a cardan joint plus an odd number of inversal joints is an even number.

Reply to
Duncan Wood

I meant Cardan shaft (a joint at each end).

Reply to
bruce56

Ever owned a Triumph Herald?

Reply to
Mr Pounder

No. I have seen its turning circle quoted as 25' and also 26'4"" That requires a steering angle of 43 degrees. I think most cars today stop at 38 degrees. Anyway it is a 2-door car somewhat smaller than a taxi.

Reply to
bruce56

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