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Cant
Jan 5, 2008 1:09:14 GMT
Post by angelislington on Jan 5, 2008 1:09:14 GMT
What is 'cant'? I see from this that it means that one track is slightly higher than the other 'to counteract the centrifugal force of a train travelling around the curve'. Um - I'm a bit bewildered by this [1] - to counteract? Surely it would actually assist the train round the bend (like leaning a motorbike into a bend) than counteract any forces? Hmm. Please explain in words of one syllable if at all poss! [1] a permastate for me, so what the hey...  |
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mrfs42
71E25683904T 172E6538094T
Big Hair Day
Posts: 5,922
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Cant
Jan 5, 2008 1:29:50 GMT
Post by mrfs42 on Jan 5, 2008 1:29:50 GMT
Wheels are not turned parallel, there is a 1 in 20 cone [1] increasing from the outside towards the root diameter of the flange, the forwards motion of the train and the downwards motion of the train due to the mass (think of the fishplates moving up and down at St Dunstans LC) all conspire against the train going around a flat and level curve - wheels wear against the rails causing rolling resistance. Cant eases this by lifting the outside rail - balancing the centrifugal force. Or for the really simple version - think of the racing track at Brooklands - the elevated bits (going up towards the outside of the curve) are canted.) If you really, really want I've got a copy of the Permanent Way Institute Textbook - it's 625 pages of fairly dense maths. I'm fairly sure it has been around in the pile of books in the 'bedtime reading material ' [2] recently (you know the one I mean). [1] so the wheels can go round curves. [2] usually a selection of stuff guaranteed to send me to sleep. EDIT: look at your Designworks book - white one next to the box on the bottom shelf with the Jubilee signalling notice in - there's a cross section of Mansion House that shows the cant through the platforms |
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Colin
Advisor
My preserved fire engine!
Posts: 11,347
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Cant
Jan 5, 2008 4:05:17 GMT
Post by Colin on Jan 5, 2008 4:05:17 GMT
EDIT: look at your Designworks book - white one next to the box on the bottom shelf with the Jubilee signalling notice in - there's a cross section of Mansion House that shows the cant through the platforms My book isn't next to a box - nor is it on a shelf!  ;D ;D ;D ;D ;D I just thought it'd be useful to mention that tilting trains where invented as another way of countering the centrifugal forces when going round bends and thus allows trains to go round bends faster without passengers noticing any difference. |
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Deleted
Deleted Member
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Cant
Jan 5, 2008 7:09:05 GMT
Post by Deleted on Jan 5, 2008 7:09:05 GMT
Cant is more for passenger comfort than for safety. When a train goes round a curve, the passengers feel they are being pushed towards the outside of the curve (actually, it's inertia making their bodies want to go straight ahead, but no matter). Raising the outer rail reduces this effect.
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Cant
Jan 5, 2008 7:36:33 GMT
Post by cetacean on Jan 5, 2008 7:36:33 GMT
A passenger's momentum means they naturally go straight forward. When a train goes round a left hand corner, this means they get pushed towards the right hand wall of the train. With cant, the train is tilted so that gravity provides an equal pull to the left, balancing the forces.
Tilting trains do exactly the same thing. They're used when providing enough cant in the track isn't possible. For example, more tilt is needed the faster a train is going, so with tilting trains the cant of the track is usually set for slow speed trains and the faster tilting trains add the extra tilt themselves.
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Cant
Jan 5, 2008 14:31:36 GMT
Post by angelislington on Jan 5, 2008 14:31:36 GMT
Hey guys, thanks for all your replies - I realised last night I was on the right kind of path thinking in terms of bikes leaning into corners, but of course they only have two wheels, not four, so when I thought about how my lil Micra corners (or doesn't, compared to my old Mini  ) it all made sense. I still think the word 'counteract' was what threw me, I appreciate the word 'balance' more, that kind of works in my little noddle better! (Odd: I just remembered that someone posted last night with a Wiki article, and that post isn't there any more. I found that useful too, so ta, mystery peep) |
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) it all made sense. 
