From: pierson@cimcad.enet.dec.com (Dave Pierson)
Subject: Re: Diesel vs. Electric Locomotive Maintenance
Organization: Digital Equipment Corporation
Date: Wed, 7 Oct 1992 22:23:23 GMT

Firstly,  a reference:
	US DoT
	Dual Mode Locomotive Systems Engineering
	FRA/ORD-80/82.II

	They assign a value, for maintenace of straight electrics, of 50% of
	the equivalent diesel-electric.  These are professionals, tho the
	number is estimated, not measured.

	Among others, they cite:
	Engineering Cost Data Analysis for RR Electrification
	E G Scharm/Arthur D Little/US DoT, 1976
	(which I haven't a copy of...) 

In article <35621@cbmvax.commodore.com>, grr@cbmvax.commodore.com (George
Robbins) writes, in part:

>In article <1992Oct6.170801.16310@engage.pko.dec.com>
>pierson@cimcad.enet.dec.com (Dave Pierson) writes:

>> In article <35601@cbmvax.commodore.com>, grr@cbmvax.commodore.com
>> (George Robbins) writes, in part:

>> >In article <1992Oct5.233132.27383@s1.gov> lip@s1.gov (Loren I. Petrich)
>> >writes:

>> >> 	I have seen it claimed that electric locomotives usually need
>> >> much less maintenance than diesel ones. Is there any truth to that
>> >> claim?

>> >Well, the are a couple of problems with your assertions.  First of all
>> >electric locomotives aren't particularly simple.  In the case of the
>> >diesel locomotive, you can regulate power output simply by changing
>> >the engine speed and simple switching of the traction motor series-
>> >parallel arrangements.

>> >An electric (we'll deal with a powerful AC one) has to in effect
>> >have a power sub-station
>> 	Consider that most power substations are expected to operate unmanned,
>> 	24 hours a day 365 days a year.  Such subs are highly reliable.
>> 	Bouncing them around a railroad will cut into that, but not a lot.

>Assertion.  Substation equipment need not meet size/weight concerns
>that traction equipment is subject to, operates under effectively
>constant or slowly chaging load and is not subject to vibration or
>impact.
	True enough (btw is that your assertion, or mine...).  BUT.  There is
	a little recognized (outside the loco building business problem with
	electics and to a lesser extent, diesel electrics:  The things can
	easily be too light.  In either case, frames are commonly built to
	heavy to add weight.  A broken down electric is no fun.  I suggest that
	after 90 odd years of building them, they are built tough enough
	(weight not being critical) to survive as well as their stationary
	equivalents.


>> 	Similar swirch gear is need on some diesels.  Many modern ones use
>> 	solid state gear, just like the modern straight electrics.

>Not so.  Most of the diesel gear is on the control side of things and
>switches substantially less power, as opposed to  switching full power
>under load.

	Modern electrics also use solid state gear.  Certainly an electric
	road car would (no hv).  The normal, new, straight electric is all
	solid state except, perhaps, the maind disconnect.  The control is
	solid stae, whether chopper=> dc series motor or inverter=> ac
	induction traction motor.

>> >All of these needs to be cooled and controlled so you have quite a
>> >pile of auxilliaries
>> So does a diesel prime mover.  Needs rather more cooling, in fact.

>Could be, not sure it's a given though.
	I consider it a given.  Assume 1000 hp at the drawbar.  (and, set aside,
	for now, the short term adavantage of the straight electric...).
	That means:
		traction motor efficiency
		control gear efficiency
		transformer efficiency

	for a straight electric.  for a diesel electric:
		traction motor efficiency
		control gear efficiency
		alternator efficiency
		diesel engine efficiency.

	Toss the first two, assume them equivalent.  (not unreasonable)

	Transformers of that size are not acceptable under 90%+ efficiency.
	so the transformer "wastes" (requires cooling for) roughly 100 hp.

	Alternator efficiencies not relavant to "how much cooling does the
	diesel" require. (for interst, assume them to be 90%ish.)

	Diesel efficiencies are roughly 30%, maybe 35%.  So for 1000 hp on the
	draw bar, the cooling system has to dissipate 2000 hp.
	(all the efficiencies can be verified in standard engineering
	handbooks.)

	(on the unrelated (since we started talking about engine cooling) note
	of efficiency: gasoline engines will run a bit less (say 25-30% range)
	than a simlar diesel.  A Gas turbine rather more _AT_ _FULL_ _LOAD_.
	The diesel electric and the straight electric are actually fairly close
	in energy efficency, since the straight electric does have some losses
	in the distribution/transmission system.)

(in another note on the same thread, yes the GG1s (and everything else of the
vintage had PCBs.  BUT, as noted, the mechanicals were starting to flat wear
out.  Look real close at some of the preserved specimens: patches on patches,
bodies fixed with bondo and rusting out, windshields held in with silicone
caulk.

They were TIRED.  Some years back i made an expedition to ride behind 4935,
the first to get repainted in PRR colors.  Thay had substitute another,
disappointing people who had travelled great ditances:  The break rigging had
failed.  More signs of age.  I admire/love the GG1, but they had done their
duty.)

thanks
dave pierson			|the facts, as accurately as i can manage,
Digital Equipment Corporation	|the opinions, my own.
200 Forest St			|I am the NRA.
Marlboro, Mass		01752	pierson@cimnet.enet.dec.com
"He has read everything, and, to his credit, written nothing."  A J Raffles
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