Post by GraemeIn the early 60s the SR did quite a lot of experiments with different
formations. Generally when operating a class33 and and an EMU the traction
motors on the later were isolated so the EMU was effectively a 4TV for
control purposes.
I think you might possibly have confused two different test set ups
and/or confused with some of the early days of Bomo line working when
Reps were delivered out of sequence.
The first push pull test set out to establish two different results,
and used EL or EDL (i.e. 71s or 73s) with various formations of Ceps
MLVs and LH stock. In these the Ceps had motors isolated.
One group of tests was to prove to MoT or whoever it was at the time
that trains up to 90 mph with a driving tralier could be allowed.
Until that time, SR EMU were globally limited to 70 mph, and all main
line express units had end motor coaches (Pul/Pan Bel Cor/etc Lav),
only the 2car sets like Hal and Bil had one end driving trailer and
they were (I believe) limited to 60 mph at that time. Propelling
driving trailers at 90 mph had to be proved, not only for the Rep/TC/
EDL etc operation but for the forthcoming Cig units, the first SR
express unit with one intermediate motor coach, AM9 (Clacton units)
AM10 etc etc. Those tests started out using a 71 pushing various test
sets of hauled stock, motor isolated Ceps, and MLV as control cars.
Tests were not to prove push pull per se although rigged up control
cables were laid through the stock involved if not already cabled,
The second set did use motor isolated Ceps, this time with 73s and
again MLV as control heads, in various lengths (there was a special
3Cep involved) with one or 2 73s and/or one or 2 MLV. These were the
push-pull control tests and used to make alterations to the already
established 1957 27-way control equipment (i.e. Cep as built) into
1966 control equipment (Rep TC). ((1963 on Cogs control was another
step that allowed the intermediate motor coach and was not in itself a
push pull evolution step)).
The 33+dead EMU tests were again something different. These were
primarily to evolve the EP braking braking control mods and diesel
loco engine control mods. D6580 was used, and yes, while it did run
around with old EMU cars they were not really push pull rials in the
sense they need to prove anything with push pull, it had already been
done with the EDLs. The 33 had to have the modified brake
controllers (and don't forget 33s have 4 driving positions) and
configured a Westcode device to respond to electric logic signals to
create stepped engine control pressures.
Yet another thing was the 6Cor - 601/701 yes that was a de-motored EMU
but was a real trailer set, not a motors isolated set up, and had end
ETH connections.
The last bit was that Rep motor caches were delivered out of sequence
and one or two apparently without motors. Thus it was possible for
short durations to see 33s working ''4Rep'' that were made of TC DTSO
and Rep trailers, and dead 4Rep wih DL/EDL haulage. Push pull yes,
push pull tests no.
--
Nick