-=> Quoting Alec Cameron to Gregory Procter <=-
 AC> Hi Gregory
 AC> On (11 Aug 97) Gregory Procter wrote to Alec Cameron...
 AC> Well, I don't know what you mean by steam MOTOR. Reciprocating
 GP> engine?
 AC> Cross compound? Vee 12? Turbine?
 GP> I'd stick with a reciprocating engine design, a; because it would need 
o
 GP> run
 GP> from zero RPM to xxxx RPM and b; because I don't know about turbines 
other
 GP> than turbos on car engines (and that's minimal)
 GP> First principal of the type would be simplicity and using currently
 GP> available
 GP> machinery for manufacture.
 GP> So; an in-line single acting motor with poppet valves. (and lower barrel
 GP> ports?)
 AC> I have had a lot to do with steam turbines but I never did see a steam
 AC> engine with in- line cylinders. I *suppose* that a conventional two
 AC> cylinder steam loco would have total cylinder volume of roughly 3000
 AC> cubic ins.
      20 inch x 24 inch = 7540 cu.in. x 4 = 30160 cu.in. total at 200 rpm 
ax.
      would be an approximation for a medium size loco.
      Working 30160 cu.in. backwards, 8 cylinders, 2500rpm would give a 7.5in 
x
      7.5in cylinder which would be workable.
 GP>     Without getting out my slide-rule, 200mm bore and stroke per 
linder
 AC> I don't have a slide rule, but your 200mm cylinder would be about 400
 AC> cu ins, so as a first approximation you have in mind a 6 or 8 cylinder
 AC> steam engine. Has there ever been such a thing? [I cannot see why not].
 AC> And if not, why not??  Apart from the fact that for a given HP, engine
 AC> costs of mfr and maintenance increase with the number of cylinders
 AC> used.
 AC> Maybe, that kind of engine was used on the large steam lorries that
 AC> once operated.
      There was a German loco with twin cylinders on each of 4 indivdually
      driven axles in 1942, but the war got in the way.
      I think the design picked all the worst features: Individual axle drive
      without individual control, 4 complex steam motors, 4 sets of flexible
      gear drives, rigid frames.
 GP> I found with the steam car design that a two speed gearbox made a major
 GP> difference to the engine design. 3 speeds didn't appear to be worth 
while.
 AC> Epicyclic with no clutch required, would probably be the choice.
      Agreed.
 GP> At 515 KM/hr, any unsprung weight would count as heavy! An axle hung 
motor
 GP> would soon smooth out any uneveness in the track ;-)
 AC> Not so according to a paper I once saw. The writer was trying to show
 AC> that in a network having emu car sets of one uniform design, the
 AC> rhythmic pounding of axle hung motors would tend to synchronise with
 AC> the local hill- and- dale deterioration, making the hills higher and
 AC> the dales lower, as each car set traversed the worn sections. Writer
 AC> said that this would tend to self- correct, if assorted train carsets
 AC> including loco hauled were instead used so that no one carset design
 AC> would predominate.
 A good reason for non-standardisation? ;-)
 He/you are correct of course, things will always get worse if left!
 Oscillations will create a ryhtmic pounding if all spring and damper rates 
are
 the same. This could be countered by using slightly different spring rates 
n
 the axles of a bogie. It is done in some automobiles to improve ride.
Greg.
  
... Reality-ometer:  [\........]  Hmmph!  Thought so...
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