On Thu, 17 Jan 2008 15:44:51 -0800 (PST), D7666
wrote:

various snipped out

I don't know what the current limit relays were set at on 501s but
being 4 motors per unit would be likely to draw more than a two motor
2EPB.

Published ''spotting book'' values of a 2EPB are 2x250 hp and 501
4x185 hp so that makes a 501 in round figures 50% more powerful than a
2EPB - but I'd caution those numbers with similar comments I have made
before about DC EMU in that the current limit relay setting needs to
be known to understand peak current draw.

As regards another part of the thread, I thought 2x313 operation was
killed by platform length limits. 501 units were on 57 foot frames
and platforms that could take 6cars laid out for that length - but
could not take standard 6car sliding door trains with 20 m bodies.

And I can't see why a 6car 313 would draw siginficantly more power
than a 6car 501 to trip traction supplies. Again using ''spotting
book'' values, without current limit values, a 313 has 8x82 kW motors
that in round figures is 880 hp per unit - while a 501 is 740 hp.

I would have expected the LNWR DC supply to have been a bit more
robust than that as the overall load increase taking all traffic is
not 20% from a simple 313 and 501 comparison - but is Bakerloo+501
c.f. Bakerloo+313 with the Bakerloo load unchanged.

Must admit never thought about this aspect before, I might be wrong,
its not a route thats easy to obtain gen on the traction supplies.

Don't the motor control systems of a class 313 present a more "peaky"
load than older stock ? This would in some way seem to be comparable
behaviour to computer switched-mode power supplies which blow plug
fuses if said fuses are rated purely on the current drawn after
switch-on. While I heard drivers allege that a 6-coach train tended to
trip sub-stations, I never heard any comment about being unable to fit
the trains in the stations which ISTR usually had about a
carriage-length to spare with c501s; when the 313s were first
introduced one difficulty was getting them to stop with any carriages
in the station and I don't think the cause was purely "driver
technique".