"Arfa Daily" wrote in message
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"John Rumm" wrote in message
et...
John wrote:
"Graham." wrote in message
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Graham.

%Profound_observation%
wrote in message
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On 24 Mar, 20:49, "mark" wrote:
The warning says something like: Will come to a Sudden Stop at the Red
Line.

How does that work?

mark
Inductance loop buried in the ground at red line.Puts the brakes on.
Assuming you`re talking about shopping trolleys but just forgot to
mention it?

Assuming the trolley side is passive, it can't have too much
range can it?
Couldn't one just lift the trolley over the sub-surface coil, or
are trolley thieves not that bright?


A cover sort of flips around the wheel. It requires a tool to reset it.

Trolleys - I think those that can travel up and down moving
escalator type ramps are clever.

Those usually have a fixed inner part of the wheel and rotating discs on
the outside edges. The edges of the discs only clear the fixed bit by a
few mm and are fairly slim. Hence on the travellator the wheel edges drop
into the grooves on the surface leaving the fixed bit of wheel grounded
on the raised bits of the surface.

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Cheers,

John.

I thought that the ones that I had seen, had the grooves in the moving
walkway, slightly off-parallel, so that when the wheel edges dropped down
into them, they 'locked' in place, as gravity tried to drag them deeper
into the diminishing gap ?

Arfa


The ones I have seen also have a claw / sawtooth type feature.