sp1 Posted October 19, 2016 Share Posted October 19, 2016 But without it it we would possibly have Donald T to look forward to (sorry, NOT meaning to be in any way political). Link to comment Share on other sites More sharing options...
sp1 Posted October 19, 2016 Share Posted October 19, 2016 Sorry, not sure what happened there! ps I'm sure Donald's a great guy! Link to comment Share on other sites More sharing options...
RMweb Premium Downer Posted October 19, 2016 RMweb Premium Share Posted October 19, 2016 What on earth would give you that idea? 2 Link to comment Share on other sites More sharing options...
RMweb Gold Budgie Posted October 19, 2016 RMweb Gold Share Posted October 19, 2016 I am aware of that, but the discussion was about O or 0, and OO or 00? Really? Then why is it entitled "Peco announces bullhead track for OO"? Link to comment Share on other sites More sharing options...
Jeff Smith Posted October 19, 2016 Share Posted October 19, 2016 I think it is a moot point - or maybe it should be a mute point - as long as it is in context everybody understands the meaning. Link to comment Share on other sites More sharing options...
Jeff Smith Posted October 19, 2016 Share Posted October 19, 2016 Sorry, not sure what happened there! ps I'm sure Donald's a great guy! What on earth would give you that idea? He said so himself, what more do you need? Link to comment Share on other sites More sharing options...
RMweb Premium Coryton Posted October 19, 2016 RMweb Premium Share Posted October 19, 2016 http://www.rmweb.co.uk/community/index.php?/topic/105495-Hornby-b12/page-6 There was also the delight of sorting out whether or not the wheel bosses should be green or black. Great stuff and very informative! Good news about the foot of the rail. I knew that bullhead rail was designed to be turned over when the rail head was worn but wondered why it wasn’t done. Thanks to the experts here, I now know. What I've never understood is that - given that it wasn't turned over - what the advantage of using bullhead actually was... Link to comment Share on other sites More sharing options...
frobisher Posted October 19, 2016 Share Posted October 19, 2016 It's no accident that instead of 000, 0000, and possibly 00000 we got N, Z & T. Though we did briefly have 000 as a semi-precursor to N back in the 60's... Link to comment Share on other sites More sharing options...
frobisher Posted October 19, 2016 Share Posted October 19, 2016 What I've never understood is that - given that it wasn't turned over - what the advantage of using bullhead actually was... Flat bottom rail is a slightly more difficult profile to manufacture "back in the day" perhaps? Plus, in theory it doesn't have a preferred way up of the two when first installed. Link to comment Share on other sites More sharing options...
RMweb Gold Colin_McLeod Posted October 19, 2016 RMweb Gold Share Posted October 19, 2016 Can anyone confirn if the idea of turning bullhead rail over is flawed if the underside gets indented where it is resting on the chairs. Link to comment Share on other sites More sharing options...
Jeff Smith Posted October 19, 2016 Share Posted October 19, 2016 I thought that once the idea of turning it over was abandoned (due to indentations) it was changed to a non-symmetrical design. I'm sure there is a right way up for B/H rail! Link to comment Share on other sites More sharing options...
RMweb Gold martin_wynne Posted October 19, 2016 RMweb Gold Share Posted October 19, 2016 (edited) What I've never understood is that - given that it wasn't turned over - what the advantage of using bullhead actually was... A significant advantage is the speed of rail replacement. A 60ft bullhead rail can have all the keys knocked out, rail replaced, keys and fishbolts replaced, and back in service, quite quickly. There is only one fixing per sleeper per rail to be replaced -- and the keys as tapered wedges are easily replaced tight. Early flat-bottom rail tended to be spiked directly to the timber or through a baseplate. Requiring the spikes to be withdrawn, rail replaced, and spikes hammered home again. At least two and often 3 per sleeper per rail, and difficulty in getting a tight fixing for the second time. Pandrol clips were not invented and patented until 1957. Can anyone confirn if the idea of turning bullhead rail over is flawed if the underside gets indented where it is resting on the chairs. That was the problem. But also unless the rail head is worn down to exactly the same size as the rail foot, it won't fit properly in the inner jaw of the chair when turned over. It could be too loose or too tight. Early bullhead rail was the same size head and foot, so there was never any chance of worn rail fitting snugly in the chairs, it was always too loose, allowing it to move vertically in the chair under traffic, loosening the keys until they fell out. regards, Martin. Edited October 19, 2016 by martin_wynne 1 Link to comment Share on other sites More sharing options...
Ian Abel Posted October 19, 2016 Share Posted October 19, 2016 (edited) Sorry, not sure what happened there! ps I'm sure Donald's a great guy! I'm sure cat turds taste great also, my dog seems to think so! Edited October 19, 2016 by Ian Abel 3 Link to comment Share on other sites More sharing options...
Pacific231G Posted October 20, 2016 Share Posted October 20, 2016 (edited) A significant advantage is the speed of rail replacement. A 60ft bullhead rail can have all the keys knocked out, rail replaced, keys and fishbolts replaced, and back in service, quite quickly. There is only one fixing per sleeper per rail to be replaced -- and the keys as tapered wedges are easily replaced tight. Early flat-bottom rail tended to be spiked directly to the timber or through a baseplate. Requiring the spikes to be withdrawn, rail replaced, and spikes hammered home again. At least two and often 3 per sleeper per rail, and difficulty in getting a tight fixing for the second time. Pandrol clips were not invented and patented until 1957. If you've seen the movie The Train you may have noticed how much easier it was for the La Biche character (Burt Lancaster) to remove a length of bullhead rail track than a length of Vignoles (flat bottom). In the latter case he has to unbolt the fishplates and then unscrew the fang bolts that fix the foot of the rail to the sleepers. For the double champignon (bullhead) rail, as Martin says, it's just the fishplates and keys. It just so happened that the disused line they used for filming those sequences south of Acquigny had both types of rail. That section has since been lifted and the surviving section north and south of it long since replaced with Vignoles but at Pacy, on the preserved section of the line south oif where the filming took place, some DC rail still survives in sidings. This is not my best ever photo but does show both types of rail and the fixings used. I'm pretty sure the rail in the sidings is asymmetric double champignon i.e. bullhead as the head does seem larger than the foot. Each of the pre SNCF companies had their own preferences for rail with both symmetric and asymmetric (bullhead) double champignon being used until the end. Some companies only used vignoles (They also had different ideas about sleeper spacing) Edited October 20, 2016 by Pacific231G 6 Link to comment Share on other sites More sharing options...
Derekstuart Posted October 20, 2016 Share Posted October 20, 2016 Oh for god's sake... I'm sure cat turds taste great also, my dog seems to think so! Link to comment Share on other sites More sharing options...
2750Papyrus Posted October 20, 2016 Share Posted October 20, 2016 What I've never understood is that - given that it wasn't turned over - what the advantage of using bullhead actually was... I have always understood that, historically, bullhead track was more robust and/or stable. As pointed out in another post, early F/B rail was spiked directly to sleepers whilst B/H had a reasonably substantial chair increasing contact with the sleaper, to which it was attached by a threaded fastener. Maybe a bit like the difference between a nailed or screwed joint? This also gave early FB advantages in component cost and laying time. Link to comment Share on other sites More sharing options...
andytrains Posted October 20, 2016 Share Posted October 20, 2016 Any news on the Peco track? This seems to be way off topic. Link to comment Share on other sites More sharing options...
gr.king Posted October 20, 2016 Share Posted October 20, 2016 I'm not sure this topic could stand any more news on the product just yet. Look how much heat has been wasted just following the release of one image on Twit-book or Face-ache or whatever they call it...... Link to comment Share on other sites More sharing options...
RMweb Gold martin_wynne Posted October 21, 2016 RMweb Gold Share Posted October 21, 2016 Early flat-bottom rail tended to be spiked directly to the timber or through a baseplate. Requiring the spikes to be withdrawn, rail replaced, and spikes hammered home again. At least two and often 3 per sleeper per rail, and difficulty in getting a tight fixing for the second time. Just to add that the tapered bullhead keys also add a significant protection against rail creep (if driven the right way round). Rail creep is dangerous if it causes the expansion gaps to close up, leading to buckled track in hot weather. Spiked flat-bottom track is very vulnerable to rail creep, often requiring rail anchors to be used. Sometimes lots of them. Imagine changing this lot to replace a broken rail: linked from http://www4.radioparadise.com/graphics/tv_img/33210.jpg http://radioparadise.com Notice also that traffic has loosened almost all of the spikes. Martin. 1 Link to comment Share on other sites More sharing options...
Derekstuart Posted October 21, 2016 Share Posted October 21, 2016 What was the reason for changing from bullhead to flat bottom? I have read that it is down to International agreement, but think that not the case here. Although now our tiny island cannot think for itself unless there's an Internationally agreed set of specifications for everything, but as FB started to become more popular in the 1960s- an era when we were capable of designing our own things, I can't see that being the reason. (historic appraisal of the Country, no political statement intended). So is there some reason why bullhead is not capable of being used as a high speed rail? It **LOOKS** stronger than flat bottom, but I am assuming it isn't. I know that when designing cants the limit is higher for FB than BH. Link to comment Share on other sites More sharing options...
AndyID Posted October 21, 2016 Share Posted October 21, 2016 What was the reason for changing from bullhead to flat bottom? I have read that it is down to International agreement, but think that not the case here. Although now our tiny island cannot think for itself unless there's an Internationally agreed set of specifications for everything, but as FB started to become more popular in the 1960s- an era when we were capable of designing our own things, I can't see that being the reason. (historic appraisal of the Country, no political statement intended). So is there some reason why bullhead is not capable of being used as a high speed rail? It **LOOKS** stronger than flat bottom, but I am assuming it isn't. I know that when designing cants the limit is higher for FB than BH. I would think continuous welded rail had something to do with it. Link to comment Share on other sites More sharing options...
Derekstuart Posted October 21, 2016 Share Posted October 21, 2016 Of course. But is there any reason why BH cannot be made as CWR? I would think continuous welded rail had something to do with it. Link to comment Share on other sites More sharing options...
RMweb Gold martin_wynne Posted October 21, 2016 RMweb Gold Share Posted October 21, 2016 What was the reason for changing from bullhead to flat bottom? I have read that it is down to International agreement, but think that not the case here. Hi Derek, Nothing to do with international agreement. Even the existing British Standard flat-bottom rails were found unsatisfactory for British Railways, who designed their own new flat-bottom rails to replace bullhead (the FB-109 and FB-98 sections). Have a read of pages 28-35 in BRT3. The problem with bullhead rail is the lack of stiffness, especially lateral stiffness. Flat-bottom rail is taller, giving additional vertical stiffness, and the wide foot gives it significantly greater lateral stiffness. With the increasing weights and speeds of traffic after WW2, the maintenance costs of tamping the main running lines to maintain good line and top were increasing significantly. It was felt that the increased cost of flat-bottom track would be offset by reduced maintenance cost. Bullhead remained perfectly satisfactory for branch lines and secondary lines, which lasted a long time that way because there was plenty of serviceable used bullhead rail being cascaded down from main lines which had been converted to flat-bottom. regards, Martin. Link to comment Share on other sites More sharing options...
RMweb Gold The Stationmaster Posted October 21, 2016 RMweb Gold Share Posted October 21, 2016 Of course. But is there any reason why BH cannot be made as CWR? It has been done - there were a couple of stretches of bullhead cwr on the Western at one time although i presume they were probably experimental rather than anything else as they pre-dated flat bottom cwr being used on a widespread basis. But just look at Martin's explanation for the change to flat bottom rail - higher speeds and increasing axleloads plus traffic frequency demanded more robust rail, simple as that. 1 Link to comment Share on other sites More sharing options...
RMweb Gold martin_wynne Posted October 22, 2016 RMweb Gold Share Posted October 22, 2016 Of course. But is there any reason why BH cannot be made as CWR? Hi Derek, In long-welded track, only the end sections of a long rail expand and contract. The middle section is prevented from expanding or contracting by being held tight by the Pandrol clips and heavy concrete sleepers. This creates enormous stresses in the rail. To prevent the track buckling under this expansion stress, deep ballasting is needed and the ballast is piled over the ends of the sleepers. Bullhead rail can be welded into longer lengths, and it has been done. But only for two or three 60ft lengths. It can't be welded into very long lengths because the chairs and keys are not capable of holding the rail firm enough to contain the expansion stresses and prevent the rail from buckling. regards, Martin. Link to comment Share on other sites More sharing options...
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