-=> Quoting Alec Cameron to Gregory Procter <=-
 AC> Hi Gregory
 AC> On (04 Jul 97) Gregory Procter wrote to Alec Cameron...
 -=> Quoting Alec Cameron to Gregory Procter <=-
 AC> Isn't the gearing ALWAYS arranged for ultimate speed? hence freight
 AC> locos geared different from express passenger, and suburban multiple
 AC> untis geared differently again.
 GP> I was refering to the potential speed for the locomotive only, not
 GP> locomotive
 GP> and train.
 AC> Gotcha. That seems a rather airy fairy speed that doesn't mean much
 AC> but I see what you mean. Rather like holding down the clutch pedal on
 AC> an automobile at full throttle. Interesting but keep, out of MY car!!
 AC> :-)
It doesn't happen of course, a loco with NO load pulling ability at max speed
would be pointless. However I've built cars and motor cycles on that 
principle.
Works fine there, but why don't people come for the ride?
In automobile terms, it compares to the different back end ratios you can 
order
when you buy a pickup. Do you want the Interstate gearing for long distance 
high
speed work, or are you intending to haul a house-truck body and a 2.5 ton
trailer over the mountains? You will want different gearing. The truck's
"Ultimate Speed" might be 120Mph with wing mirrors and mudflaps off, but only
50Mph with the load hauling gearing. If you kept your foot down with 50Mph
gearing and no load, you would be collecting motor parts from all over the
place. You might not be allowed to drive my car either ;-)
 AC> The record holding TGV (515Km/hr or whatever) gearing was a
 GP> compromise that went only as far as replacement gears which would fit 
he
 GP> standard gear housing and oversize wheels. It's ultimate speed would be
 GP> greater.
 AC> And is compromised by a few other things- like the fact that with
 AC> coupled drive wheels, a slip on greasy or leafy rails leads to almost
 AC> total loss of traction.
 GP> These factors are exactly the same for steam, Diesel, electric and
 GP> etc.
 AC> The "factor" may be the same but the results are quite different.
Granted, I get the same result on my front path with moisture and leaves, 
've
ended up feeling decidedly uncoupled!
 AC> Not really. Steam locos' drive wheels are always coupled but the
 AC> others, hardly ever.
 GP>  Would you like a list of all the Diesels and Electrics built with rod
 GP> drive?
 AC> Sorry I was dealing with the majority, and you are right of course
 AC> there have been quite large numbers of weirdos.
I was thinking in terms of European Diesel Hydraulics and our local 0.6.0
shunters with rod drive.
 GP> Diesels and elecs having independent drive to
 AC> each axle, some may grip while others slip and a decent drawbar pull
 GP> is
 AC> maintained by the loco as a whole.
 GP>  Once the limit of traction is reached, if one axle slips, the load
 GP> will
 GP> go on
 GP>  to the otheraxles and they will slip to.
 AC> Not all the load will transfer, the inevitable drop in speed will see
 AC> a reduction in wind and friction forces.
Yes, if you loose the tractive effort of one axle, the speed will drop
considerably.
I was employed as a mechanic
 AC> on emu trains, wheel slip was a single car problem, the other cars in
 AC> the train would battle on without loss of adhesion. I lived near the
 AC> steepest bank on the local line so wheel slip was a frequently observed
 AC> situation and [surprise surprise!] it was the steamers that were most
 AC> affected. The bank was such a nuisance that the emergency coupler [emu
 AC> to steamer] was permanently kept under a seat in the passenger waiting
 AC> room of Denistone down platform.
I can imagine! Did they ever consider changing to rope haulage? (sorry, 
getting
silly there)
 AC> Some "smart" control systems apply less power to the lead axle, while
 AC> loading up those further back.
Better equalization would have been more effective!
The smartest, just regulate the slip so
 AC> that the drive power to each motor is different from all its buddies,
 AC> and the drive power ramps down and up rhythmically at the onset and
 AC> recovery from slip. And the extremely smart locos provide constant
 AC> positive slip at each wheel so as to win adhesion considerably above
 AC> the conventional "25%" figure.
 GP>  You could do the same thing with a 1997 steam locomotive also.
 AC> No I couldn't. But yes, NASA or some other smart scientists could do
 AC> as you wish given the funds! Where is this 1997 steam loco?! I wanna
 AC> ride....
 Just raise a few billion for me and I'll build it! It's a little outside my 
HO
 and 3.5" experience but what the heck!
 GP> We started this discussion with me postulating a modern steam engine 
ith
 GP> individual axle drive, without coupling or connecting rods to the 
heels.
 GP> A Diesel or electric with coupling rods is not perfect at high speeds.
 AC> I don't feel constrained to follow exactly in your steps, discussion-
 AC> wise.
Fair enough but the "Rocket" vs "Euro Star" isn't going to be a fair 
comparison!
It is quite hard to consider a modern steam loco, because there
 AC> are none. If by individual axle drive you mean electric motors, then
 AC> that is a gross abuse of the steam loco design process. A steam loco
 AC> should have a steam engine fed by its boiler. I too would like another
 AC> steam loco design to be undertaken and more important! would like it to
 AC> be applauded for its efficiency, durability, performance and low
 AC> running cost. I see not the slightest chance, that this will ever
 AC> happen. ====
 No, I was thinking along the lines of a Diesel Hydraulic chassis, ie bogies
 driven by cardan shafts and gearing, with a high speed steam motor in the
 center, all powered by a semi-conventional/semi-flash boiler. MU'ing and
 traction control via computer electronics with track radar. There, that's 
ot
 so difficult! The South African " Red Devil" experiments showed promise for
 cooking the coal and burning the gas given off. Admittedly it wasn't good 
enough
 to convince the railway to go further, but imagine experimenting with the
 "Fell" Diesel and judging the future from that!
 AC> Noted remarks re stiction and pulses
 AC> =====
 AC> Sorry, you are not up to date. There are many large locos today where
 AC> positive slip is maintained for long periods. What you have
 AC> [correctly] described is now obsolete technology.
 GP> I admit to not being up to date on the latest technology, but I have a
 GP> passing
 GP> knowledge of the laws of nature, and even a little knowledge of physics. 
I
 GP> assume that the latest technology hasn't managed to by-pass the laws of
 GP> physics?
 AC> Those "laws" are changing! Like gravity, Einstein and Newton gave
 AC> conflicting "laws" but who cares! The end results are OK whichever
 AC> physicist is followed.
 GP> I do know that once the wheel slips, the coefficient of friction drops
 >> CONTINUED IN NEXT MESSAGE <<
 AC> ... ....Horsepower was a wonderful thing when only horses had it
 AC> -!- PPoint 1.92
 AC>  ! Origin: Bundanoon, Southern Highlands, NSW AUS (3:712/517.12)
  
... Catch the Blue Wave!
--- FMail 1.02
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