Hi Day
On (02 Sep 97) Day Brown wrote to Alec Cameron...
 AC>  DB> Could you make a piston big enough cheap enough to do anything  
 AC>  DB> useful with 15 PSI? 
Remember in my reply, I mentioned the steam liner "Great Britain"? The
designer/ builder was Isambard K Brunel. He designed and built a railway
called the Atmospheric Railway in the south of England. Bits of it have been
preserved. 15psi, and leather! were primary elements in the locomotion
arrangements.
 DB> Spoze you could do a leather diaphram a foot across to get the big 
 DB> area you'd need? At 15 PSI, that's 1500 lb or so on maybe a short 
 DB> two inch stroke, 250 ft/lb per stroke.  howze leather react to steam? 
On the assumption that steam at 15psi wouldn't be very hot, I guess the
leather could be OK. It might help to laminate the leather with an open weave
polyester netting, to give it hot tensile strength.
But I'd rather talk about Brunel!!
The atmospheric railway ran on a vacuum tube laid between the rails. The ties
were lengthways instead of cross from rail to rail. The vacuum tube was
slotted on top and the slot was sealed by a continuous leather flap.
Vacuum was held by trackside pumping stations.
The lead car of the train had a piston underneath, the piston travelled thru
the vacuum tube and the thrust was provided by the driver's controller- a rod
of some kind would push the vacuum tube leather sleeve aside so as to admit
air to the desired side of the piston.
Thus the train was propelled by air pressure [15psi]. Neat. It worked.
OK, it worked but there were problems. I imagine it would be tough to shunt 
n
a busy depot or junction, 'cos one train moving would slow down any other
nearby. Collision protection? ;-).  More important by far, the rats loved to
eat the leather which [I think] was smothered in lard [edible] to improve the
sealing.
The system was not a hilly one, and I am sure it was for passengers only.
Isambard K Brunel was a practical engineer, many of his great achievements 
re
still in everyday use and he was not driven by Managers or Bean counters!!
And, he was not familiar with the appetites and tastes of rodents.
Cheers....ALEC
... Wunce i coodn even spll ingineer. Now i are wun!!
--- PPoint 1.92
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