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Post by q8 on Oct 19, 2005 17:29:31 GMT
Now although a passenger will never see it a driver looking closely will. As you leave Tower Hill westbound you come to number 8a points that lead into the sand drag on the site of the old station westbound platform. The left hand rail of said points has no gap in it for a wheel to pass through.
So if a train were to somehow get to them when they are set for the sand drag it would be derailed. I always wondered why that was so?
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Post by Deleted on Oct 19, 2005 18:00:40 GMT
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Post by q8 on Oct 19, 2005 18:24:23 GMT
Yes I realise that AET but I wonder why there was no gap left in the rail in the first place?
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Tom
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Post by Tom on Oct 19, 2005 19:10:44 GMT
Do you mean there is no gap in the crossing nose?
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Colin
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Post by Colin on Oct 19, 2005 20:01:49 GMT
Same thing at Earls Court Eastbound from Olympia!!
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Post by q8 on Oct 19, 2005 20:47:39 GMT
Do you mean there is no gap in the crossing nose?
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I dunno what you call it but there is no gap in the left hand running rail of those points. Have a look next time you are down there. ( No 8's)
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Post by Deleted on Oct 19, 2005 21:02:12 GMT
I don't quite understand - when you say "left-hand rail", you sound as if you are referring to the left-hand stock rail and the left-hand switchblade. Are you saying that 8a points are half of a dual-driven indepedent-bladed points, with only the right-hand switch rail mobile?
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Post by q8 on Oct 19, 2005 21:10:35 GMT
Thats what I mean TOK, there IS no left hand switch blade just plain rail. As you say, only the right hand blade is moveable.
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Chris M
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Post by Chris M on Oct 19, 2005 23:13:39 GMT
Q8 - Could you draw a simple diagram, I'm interested but as I'm not au fait with the technical terminology I can't quite grasp what you're saying. I thought I had it but your lastest reply has confused me again!
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Post by igelkotten on Oct 20, 2005 0:02:17 GMT
Here in the Stockholom metro, we have a few points with "obruten korsning", "unbroken crossing" -that is, the stock rail in the crossing is not cut, so the wheels of the train do climb over the stock rail when running through that points when they are set in reverse. Those points do have two point blades, though. They are mostly found in little-used crossovers, but there is nothing prohibiting them from being used by any train, including trains in passenger service. An image of said type of crossing, courtesy of AGR:  |
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Post by q8 on Oct 20, 2005 2:36:51 GMT
There you are. Igelkotten has posted a view of exactly how it is at Tower Hill except there is no rail lift and its the right hand divergence that has the continous rail.
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Colin
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Post by Colin on Oct 20, 2005 2:42:58 GMT
I wouldn't fancy taking a train over that!! I know there is a check rail, but aint that taking a massive chance in not derailing a train?
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Post by Deleted on Oct 20, 2005 3:54:02 GMT
I wouldn't fancy taking a train over that!! I know there is a check rail, but aint that taking a massive chance in not derailing a train? Yeah -- Perhaps I've got the wrong attitude, but I think if a manager told me to drive a train over that, my first reaction would be to say "F**k off! You've got to be joking."  Hmmm..... Perhaps at EXTREME caution, but it still looks dodgy to me. Good thing they're not used very often. BTW there's the same arrangement as No.8 points at Tower Hill when coming out of Uxbridge sidings into the platforms. Start up against the outlet signal MW 51 and you'd be very close to a derailment on No.33 points. |
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Post by Deleted on Oct 20, 2005 8:11:08 GMT
Whoa. That's certainly an interesting setup!
Are there any photos of the points at Tower Hill or Uxbridge? I must confess that I'd never seen a set of points that look like those AGR points at Uxbridge before.
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Post by igelkotten on Oct 20, 2005 10:28:04 GMT
I wouldn't fancy taking a train over that!! I know there is a check rail, but aint that taking a massive chance in not derailing a train? Yeah -- Perhaps I've got the wrong attitude, but I think if a manager told me to drive a train over that, my first reaction would be to say "F**k off! You've got to be joking." Hmmm..... Perhaps at EXTREME caution, but it still looks dodgy to me. Good thing they're not used very often. Wimps! ;D The points are limited to 15 or 20 km/h, but I have seen engineer's vehicles go through them at higher speeds than that. The one thing that was drilled into our little heads during driver training was to never, ever come to a standstill with a set of wheels over the crossing, since that was begging for the wheels to starts slipping away, but apart from that, they aren't anything special. The points depicted in AGR's picture were used by every train to and from Farsta Strand during the single-track running period last summer when Sandsborg station was rebuilt. In other words, about three trains per hour (reduced service) day in, day out for two months. Not one derailment or incident. The check rail is mounted much closer to the running rail than is normal, and it is the main device preventing a derailment. After a few days of running through those points, the inside of the check rail was very shiny and polished! The idea behind these points is that since the running rail is kept unbroken, there is less maintenance to do. However, since we got our new signalling system on the green line, quite a few of these points have been removed and replaced with standard crossings and less acute point curves, to enable higher speeds through them and more efficient bi-directional running. There are several left on the red & blue lines, though. Oh, and drving a train through them feels a bit different, with the wheels on one side climbing over the railhead and the train lurching. C20 trains, havign flexible wheel mountings, does give an extra bit of a wobble, but the lurch when they go back on to the railhead is more pronounced on older stock. The feeling is quite different from the feel of a derailment, though. |
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Tom
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Post by Tom on Oct 20, 2005 10:43:16 GMT
As I thought, it is a similar situation to Stockholm. Having travelled over the crossover in the photo I can tell that the nose isn't broken, however that's mainly from travelling over it and seeing the crossover. I doubt the majority of travellers would notice.
I think the Uxbridge situation might be different - they're spring trailing power facing points, and I haven't noticed any oddities with the P/Way.
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Post by Deleted on Oct 20, 2005 16:43:17 GMT
there are points (parsons green springs to mind 21road) where there is physically only one switch rail and these are known as throw off sets but i have not worked on the points at tower hill for at least 5 years so i can not remember if this type of layout is there
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Post by Deleted on Oct 20, 2005 17:24:57 GMT
I think I've seen these types of points before - they're basically a type of catch point with only one switch rail that pulls inwards - when a train passes these points when they are reversed, they simply 'fall off' the stock rails and into the ballast.
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Post by Harsig on Oct 20, 2005 18:08:05 GMT
This article reproduced from the Railway Gazette for May 1948 should explain all.  |
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Post by russe on Oct 20, 2005 18:48:01 GMT
Nice one, Harsig. Anyone know the purpose of the longitudinal baulks in the 4-foot of the left-hand track?
Russ
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Post by q8 on Oct 20, 2005 19:38:56 GMT
Personally I am just trying to suss out where the location of the photo is?
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Tom
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Post by Tom on Oct 20, 2005 20:10:50 GMT
I think I've seen these types of points before - they're basically a type of catch point with only one switch rail that pulls inwards - when a train passes these points when they are reversed, they simply 'fall off' the stock rails and into the ballast. Single switches where the phrase I knew them by - they're fairly common. |
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Post by Deleted on Oct 20, 2005 21:04:26 GMT
Are the type used in reversing sidings called double switches then? (i.e. Rayners Lane, West Hampstead, White City CLR, etc)
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Tom
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Post by Tom on Oct 20, 2005 22:21:53 GMT
They're wide to gauge.
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Post by Harsig on Oct 20, 2005 22:26:37 GMT
Personally I am just trying to suss out where the location of the photo is? My best guess is Queens Park looking north through the sheds. If I'm correct then the road we are looking at is the one used by southbound trains from north of Queens Park. The line on the extreme right would be the Up DC line. |
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Post by Tom on Oct 20, 2005 23:00:30 GMT
Looks like Queen's Park No.24 road to me too. I don't think the points are like that any more, but I'll check next time I have a night shift there.
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Post by Deleted on Oct 20, 2005 23:59:32 GMT
Wimps! ;D The points are limited to 15 or 20 km/h, but I have seen engineer's vehicles go through them at higher speeds than that. The one thing that was drilled into our little heads during driver training was to never, ever come to a standstill with a set of wheels over the crossing, since that was begging for the wheels to starts slipping away, but apart from that, they aren't anything special. The points depicted in AGR's picture were used by every train to and from Farsta Strand during the single-track running period last summer when Sandsborg station was rebuilt. In other words, about three trains per hour (reduced service) day in, day out for two months. Not one derailment or incident. The check rail is mounted much closer to the running rail than is normal, and it is the main device preventing a derailment. After a few days of running through those points, the inside of the check rail was very shiny and polished! The idea behind these points is that since the running rail is kept unbroken, there is less maintenance to do. However, since we got our new signalling system on the green line, quite a few of these points have been removed and replaced with standard crossings and less acute point curves, to enable higher speeds through them and more efficient bi-directional running. There are several left on the red & blue lines, though. Oh, and drving a train through them feels a bit different, with the wheels on one side climbing over the railhead and the train lurching. C20 trains, havign flexible wheel mountings, does give an extra bit of a wobble, but the lurch when they go back on to the railhead is more pronounced on older stock. The feeling is quite different from the feel of a derailment, though. Thanks Igelkotten. Very interesting to see what is tolerated and accepted on other people's railways... that almost certainly wouldn't be accepted here in the UK. Especially in today's 'ultra-safe' environment. 'Wimps'?? -- I like that!! Yes, perhaps now I'm getting older it's true. But take me back a few years, and I'd have had the handle right round through that crossover!! ;D ;D |
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Post by russe on Oct 21, 2005 1:10:22 GMT
Looking at the drawing for such a 'Burland type' unbroken crossing, the lateral gap between the knuckle end of the wing and the unbroken running rail is 2 1/16", which is indeed wider than the normal crossing flangeway setting. The level part of the raised wingrail is 1 1/4" (i.e. flange depth) above the unbroken running rail height, with on and off ramps inclined at 1:80 and 1:60 respectively. Russ |
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Post by igelkotten on Oct 21, 2005 10:07:59 GMT
Thanks Igelkotten. Very interesting to see what is tolerated and accepted on other people's railways... that almost certainly wouldn't be accepted here in the UK. Especially in today's 'ultra-safe' environment. On the other hand, LU's insistance on running trains without dynamic brakes would certainly raise a few eyebrows over here. 'Wimps'?? -- I like that!! Yes, perhaps now I'm getting older it's true. But take me back a few years, and I'd have had the handle right round through that crossover!! ;D ;D I hope you would let me off first! And I personally prefer to operate in "milquetoast mode" You live longer that way.  |
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