More MU Issues (formerly Boosters/Slugs)

["Steve Palmano" <steve719@GTE.net>]

Aus loco discussion mailing list


Hello Ben, more MU issues I see!

Although, as Melanie has said separately, the MU issue does not arise in
respect of the proposed YS slug, the Y/Z MU possibility is still an
interesting technical question.

Here there's a fundamental difference in control system, the Y having 9
notch electromagnetic (9EM) and the Z the "standard" EE air throttle (EP).
I'm not aware of any EE diesel locos anywhere that were equipped with dual
MU systems, so that they could work with other EEs whether EM or EP
equipped.  And the EP/EM MU issue does seem to be a bit more complicated
than say the GM 8EM74/EE 10EM110 interface system used in New Zealand and
kindly described by John Regan and Bruce Bellingham in this forum a couple
of months back.

Nevertheless, there are indicators that an appropriate two-way EE EM/EP
interface could have been worked out if someone had wanted to do so, even
without the benefit of electronics.  Firstly, AFAIK, some of the QR Locotrol
remote control wagons allowed leading GMs to control mid-train EEs.  This
would have required one-way translation from the 8 notch electric throttle
signals to 8 distinct air pressures for the EE throttle pipe.  If you can do
it for 8 notches, then you could also do it for 9 or 10.  Secondly, the
complex MU system used by British Rail Southern Region allowed EMUs with 4
notch EM controllers to control air throttle locos (EE electro-diesels and
Sulzer diesels) and vice versa.  (I still haven't found out how the air
throttle-to-notches conversion was done, but 4EM to EP was done using a
Westcode multi-step EP brake valve.)  From the latter, one can infer that
the right kind of service-proven electro-mechanical-pneumatic interface
equipment was available from the mid-1960s.

With modern electronic control systems, the EP/EM interface probably
resolves to a case of analog-to-digital and digital to analog conversion.
Maybe some of the electronic/air interface equipment used for modern braking
systems could also be used for electrical control of an EE air throttle
line.

Then there's the brake compatibility issue, although I'd guess that in the
air brake era, both the Y and the Z followed a common standard.  In the
vacuum brake days I don't know.  Here I'll risk a speculation that there
might have been differences, although be warned that my knowledge and
understanding here is quite limited.  (Often the quickest way to get the
right answer to a question in one of these forums is to articulate the wrong
one!!!)

The Z might have had an American-style schedule braking system (l think the
number is something like 28-LV).  AFAIK these are usually based on
engine-driven compressor-exhausters (expressors) with vacuum reservoirs, the
latter trainlined throughout the loco consist by a VR pipe.  And the loco
independent air brake release function is controlled pneumatically through
the appropriate pipe or pair of pipes.  The Y might also have been like
this, or maybe it had a "British" style system.  I say this because the Y
would have needed to be compatible with the X, which could well have
followed British precepts of the time.  Here there are usually two-speed
motor driven exhausters and no vacuum reservoirs, the exhausters being run
at high speed to evacuate a train.  In an MU consist, trailing unit
exhauster speed and exhauster cutoff/choke operation are controlled
electrically - from switches inside the leading unit vacuum brake valve - by
trainwires in the MU jumper cable bundle.  Also, loco independent air brake
release is controlled electrically by magnet valves, and so is also a
trainwired function, although independent application would be controlled
directly through the straight air brake pipe.  Maybe Melanie can add
something here, or correct any errors in my musings about Y/Z brake systems.

By the way Ben, it has occurred to me that braking system differences might
explain why the ex-MRWA F and G class EEs didn't MU with the C, R and RA
classes, which I think was an issue that you raised a few months back..
AFAIK, all these EEs had EP control, but the Fs and Gs had motor-driven
vacuum exhausters, so maybe a "British" style braking system?  You know, if
we develop answers to all of these questions, we might have to ask Kevin
Lawrence to expand his EE database to include entries for MU compatibility
and brake systems (3 or 4 pipe, etc.) so that the information is recorded
for posterity. :)))

Steve Palmano


----- Original Message -----
From: ben scaro <bscaro@hotmail.com>
To: <Ausloco@listbot.com>
Sent: February 22, 2000 07:54 PM
Subject: Re: Boosters/Slugs (Was RE: BU1)


> Aus loco discussion mailing list
>
>
> I'm not sure of the mechanics of it, but what work would be needed to
enable
> a Y to mu with a Z ?
>
> Cheers
>
> Ben
>


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