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Cheeky · September 2nd 04, 06:42 PM posted to uk.transport.london

On Wed, 01 Sep 2004 20:40:39 GMT, (Neil
Williams) wrote:

On Wed, 01 Sep 2004 20:36:44 +0100, Stephen Richards
wrote:

the pdf at the link above talks about an electric motor to drive the
bus, so what is with the gear changes? Or was I imagining them?

If the electric motors are of the three-phase type often employed on
recent[1] rail stock, the "gear change" is actually a change in the AC
frequency being applied to the motors as they speed up. It (put
simply) has broadly the same effect as a gear change, but no physical
"gear" is being "changed" as such.

[1] While all EMUs built since the 1990s have this technology, it's
not always audible for various reasons. The Class 323 EMUs used in
the Manchester area seem the most obvious.

Neil

Thanks Neil - that's answered a question I've often thought when on
those trains :-)
--

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