billbedford Posted October 23, 2014 Share Posted October 23, 2014 Can this really be happening,,,after all these years it has suddenly dawned on someone that having flanges just a tad under half the size of a mosquito's willie might not be conducive to reliable running!!!! People who understand these things know that flanges have little to do with keeping wheels on rails Link to post Share on other sites More sharing options...
salmonpastures Posted October 23, 2014 Share Posted October 23, 2014 "P4 light", "accurate EM", "course P4", "scale EM", "mongrel 4", "M4", "E4", "PE4", "EM extra", "P4 plus"...what ever you choose someone will take offence ;-) Cheers Duncan Duncan, Don't forget P4-ME,,,, easily understood and hardly offensive. SAD Link to post Share on other sites More sharing options...
Tim Lewis Posted October 23, 2014 Share Posted October 23, 2014 People who understand these things know that flanges have little to do with keeping wheels on rails Worth having a look at that link - a very clear explanation from a true genius! Link to post Share on other sites More sharing options...
Penlan Posted October 23, 2014 Share Posted October 23, 2014 Don't you start.....! Does anybody remember the 4mm (Scale) Broad Gauge layout at Bristol, at what's now called the Waterfront, many moons ago which had the track set at a height somewhere around 5' 6" to 6' above the floor ? Link to post Share on other sites More sharing options...
davidbr Posted October 23, 2014 Share Posted October 23, 2014 Does the Scalefour Society (of which I am a member) have an official policy on the use of EM wheels? It is possible to envisage the situation where a layout built to P4 standards is exhibited at Scaleforum but the operator is found to be using some stock with EM wheels. Would he/she be asked to leave or would the stock with EM wheels be impounded for the duration of the show. I realise that I am being somewhat flippant but I do think this is a reasonable question to put to the society. My view is that each to their own and if someone wants to use EM wheels on a P4 layout, it is entirely up to them. Why should the Society have a policy? The Society sets a standard that is known as P4 but is not some form of railway modelling police. I appreciate the flippancy of your comment though don't see why you think your question a reasonable one. I don't see any reason for the Society even to consider the matter. If track is built to the appropriate P4 standard, wheels have to be thinned down and if the flange is some microscopic amount deeper, for one thing I doubt anyone other than someone using a magnifying glass looking for 'fault' would notice and another, if the whole thing runs more reliably, who cares? For me the matter is simple - does it run on P4 track? I do agree wholeheartedly with your last sentence. It's my railway and I will make it as I wish. David (also a Scalefour Society member) Link to post Share on other sites More sharing options...
RMweb Gold martin_wynne Posted October 23, 2014 RMweb Gold Share Posted October 23, 2014 I do agree wholeheartedly with your last sentence. It's my railway and I will make it as I wish. It is odd how often this sentiment is expressed on RMweb -- bearing in mind that in over 7 years and more than 1.6 million posts I can't recall anyone ever suggesting otherwise. Link to post Share on other sites More sharing options...
RMweb Premium t-b-g Posted October 23, 2014 RMweb Premium Share Posted October 23, 2014 People who understand these things know that flanges have little to do with keeping wheels on rails In theory...... once again! If flanges have little to do with wheels keeping on rails, how come model wheels with the only change being bigger flanges seem to stay on the rails better? Due to our tighter than scale curves, model flanges make contact with rails far more often than they do on the real railways. When you have a scale (ish) wheel profile, with a curve at the place where the tread and the flange meet, a coned tread and a curved flange, if the flange touches a rail at all, it will ride up and over it ever so easily, especially if it is sprung or compensated. So a deeper flange helps it stay on the track as it has to ride up further before it derails. This is, to me, the simplest of common sense answers as to why many, many people, struggle to get P4 to run well. If flanges make no difference to running, perhaps somebody would like to build a model railway with no flanges at all and show us how well they can get it to run. Perhaps it will be a superb running layout but only in theory! Tony Link to post Share on other sites More sharing options...
RMweb Gold Captain Kernow Posted October 23, 2014 RMweb Gold Share Posted October 23, 2014 It is odd how often this sentiment is expressed on RMweb -- bearing in mind that in over 7 years and more than 1.6 million posts I can't recall anyone ever suggesting otherwise. Perhaps because this is one of the Fundamental Truths of the Universe?... Link to post Share on other sites More sharing options...
RMweb Gold martin_wynne Posted October 23, 2014 RMweb Gold Share Posted October 23, 2014 The argument for using P4 wheels is nothing to do with how well they run. It's the fact that they are scale models of the real thing, and look better for that. In most other areas of modelling we strive to make models as close to scale size as possible, and P4 simply extends this to the wheel profile. Obviously it is going to be harder to keep such tiny flanges on the rails, especially if the treads acquire a layer of crud reducing the flange depth even further. But most P4 modellers accept the challenge for the sake of the improved appearance. Lots of them succeed. Comparing the dynamics of small scale models with the prototype coning effect is daft. Deeper model flanges will tolerate more track defects, but don't look so good. Martin. Link to post Share on other sites More sharing options...
Horsetan Posted October 23, 2014 Share Posted October 23, 2014 "P4 light", "accurate EM", "course P4", "scale EM", "mongrel 4", "M4", "E4", "PE4", "EM extra", "P4 plus"...what ever you choose someone will take offence ;-) "I Can't Believe It's Not P4"? Link to post Share on other sites More sharing options...
salmonpastures Posted October 23, 2014 Share Posted October 23, 2014 The argument for using P4 wheels is nothing to do with how well they run. It's the fact that they are scale models of the real thing, and look better for that. In most other areas of modelling we strive to make models as close to scale size as possible, and P4 simply extends this to the wheel profile. Obviously it is going to be harder to keep such tiny flanges on the rails, especially if the treads acquire a layer of crud reducing the flange depth even further. But most P4 modellers accept the challenge for the sake of the improved appearance. Lots of them succeed. Comparing the dynamics of small scale models with the prototype coning effect is daft. Deeper model flanges will tolerate more track defects, but don't look so good. Martin. Now that I do understand,,, and it all sounds like common standards/sense to me,,, In my world and on my railway I'd like all my drivers to look like my grandad,,, my firemen to look like my father and the shed foreman to look like me,,, but I'd have to spend an enormous amount of effort to achieve it and the reality is times just too short. But perhaps I could give it a go,,, now where did I put them horsehair undies,,, I need to be comfy before I accept the challenge. SAD Link to post Share on other sites More sharing options...
Will L Posted October 23, 2014 Share Posted October 23, 2014 In theory...... once again! If flanges have little to do with wheels keeping on rails, how come model wheels with the only change being bigger flanges seem to stay on the rails better? Due to our tighter than scale curves, model flanges make contact with rails far more often than they do on the real railways. When you have a scale (ish) wheel profile, with a curve at the place where the tread and the flange meet, a coned tread and a curved flange, if the flange touches a rail at all, it will ride up and over it ever so easily, especially if it is sprung or compensated. So a deeper flange helps it stay on the track as it has to ride up further before it derails. Why is it that people have so much difficulty believing the science that underlies all this. There are no differences between the performance of scale and full size wheel when it comes to the self steering effect so ably explained by Dr Feynman. Your suggestion that the flange touching the rail side causes derailment, particularly when well suspended is (how do I put this without causing offence), suggestive that you've never been actively involved in fettling stock till it runs well. In truth, exactly the opposite it true. The reason why larger flanges can help is this. Where a vehicle has insufficient suspension to ensure the wheel treads stay firmly in contact with the track, any small deviation from perfectly flat track means one (or more) wheel will lift. Once lifted, the self steering effect of the cone shaped wheels is lost and, unless the flange is deeper than the amount the wheel has lifted, derailment will follow. Hence the slightly unfashionable view that a proper P4 modeller should fit suspension to his vehicles. Yes you can get away without doing it and then fitting over scale flanges may well help save the day, but you can see why those of us who want to do the job properly would see this as both unnecessary, and a form of cheating. ..Can this really be happening,,,after all these years it has suddenly dawned on someone that having flanges just a tad under half the size of a mosquito's willie might not be conducive to reliable running!!!! So no, it's the failure to understand, and act upon, the relationship between track, vehicle suspension and wheel profile that causes unreliable running The argument for using P4 wheels is nothing to do with how well they run. It's the fact that they are scale models of the real thing, and look better for that. In most other areas of modelling we strive to make models as close to scale size as possible, and P4 simply extends this to the wheel profile... That is exactly the point, Once you've decided you don't want to distort the shape of your wheels any more than you don't want to fit the wrong shape of chimney, then adopting toy train compromises to keep train on track is out too. Will Edit for spelling- my English is very easily derailed I must fit larger flanges to my brain! Link to post Share on other sites More sharing options...
Talltim Posted October 23, 2014 Share Posted October 23, 2014 Now that I do understand,,, and it all sounds like common standards/sense to me,,, In my world and on my railway I'd like all my drivers to look like my grandad,,, my firemen to look like my father and the shed foreman to look like me,,, but I'd have to spend an enormous amount of effort to achieve it and the reality is times just too short. But perhaps I could give it a go,,, now where did I put them horsehair undies,,, I need to be comfy before I accept the challenge. SAD Laser scanner, 3D printer and Bob's your (4mm) uncle! Link to post Share on other sites More sharing options...
Buckjumper Posted October 23, 2014 Share Posted October 23, 2014 "I Can't Believe It's Not P4"? JLTRP4? Link to post Share on other sites More sharing options...
highpeak Posted October 23, 2014 Share Posted October 23, 2014 Worth having a look at that link - a very clear explanation from a true genius! This animation is also quite interesting: Link to post Share on other sites More sharing options...
Nimbus Posted October 23, 2014 Share Posted October 23, 2014 If flanges make no difference to running, perhaps somebody would like to build a model railway with no flanges at all and show us how well they can get it to run. Didn't Dick Ganderton do just that with some species of DMU Bubble Car, and run it reliably on an early P4 exhibition layout of Ashburton? The Nim Link to post Share on other sites More sharing options...
Bernard Lamb Posted October 23, 2014 Share Posted October 23, 2014 "P4 light", Cheers Duncan I remember seeing Bodmin at Chesham many moons ago. The floor in the hall was very springy and as people walked past the layout wagons in the yard would move. I did think at the time a bit more weight would have been an advantage. As for other standards than P4 at their expo. I am sure I have seen 3.5mm to the foot models on more than one occasion. I know I have mentioned this before but has any body built a WD with the correct variation in wheel profile on the tender wheels? I presume that it could not be called P4. (other locomotives with similar variation in wheel profile are available) Bernard Link to post Share on other sites More sharing options...
Guest Lyonesse Posted October 23, 2014 Share Posted October 23, 2014 People who understand these things know that flanges have little to do with keeping wheels on rails There is a world of difference between a single, coned wheelset and a multi-axle rail vehicle --- not to mention a train of such. Add to that poor gauge tolerance, flatness, wheelset axial runout (all far, far bigger than the prototype, when compared to the TG), throw in a huge dollop of friction and it's not hard to see that model flanges are very necessary. Link to post Share on other sites More sharing options...
RMweb Premium t-b-g Posted October 23, 2014 RMweb Premium Share Posted October 23, 2014 Why is it that people have so much difficulty believing the science that underlies all this. There are no differences between the performance of scale and full size wheel when it comes to the self steering effect so ably explained by Dr Feynman. Your suggestion that the flange touching the rail side causes derailment, particularly when well suspended is (how do I put this without causing offence), suggestive that you've never been actively involved in fettling stock till it runs well. In truth, exactly the opposite it true. The reason why larger flanges can help is this. Where a vehicle has insufficient suspension to ensure the wheel treads stay firmly in contact with the track, any small deviation from perfectly flat track means one (or more) wheel will lift. Once lifted, the self steering effect of the cone shaped wheels is lost and, unless the flange is deeper than the amount the wheel has lifted, derailment will follow. Hence the slightly unfashionable view that a proper P4 modeller should fit suspension to his vehicles. Yes you can get away without doing it and then fitting over scale flanges may well help save the day, but you can see why those of us who want to do the job properly would see this as both unnecessary, and a form of cheating. So no, it's the failure to understand, and act upon, the relationship between track, vehicle suspension and wheel profile that causes unreliable running That is exactly the point, Once you've decided you don't want to distort the shape of your wheels any more than you don't want to fit the wrong shape of chimney, then adopting toy train compromises to keep train on track is out too. Will Edit for spelling- my English is very easily derailed I must fit larger flanges to my brain! So we now have some people saying that model wheels behave just like the real ones and others saying they don't. Both can't be right, or can they? Perhaps model wheels will behave like real ones as long as we can scale mass, recreate prototype springing and build in the "give" that real track shows as a heavy vehicle rides over it. Plus we need to do away with our silly tight curves. My trains run very nicely thank you and to test my points, of which I have built many hundreds, I run a vehicle through them before I put the check rails on as good point work doesn't need check rails if the path through the crossing nose is straight and the alignments are good. To suggest that I have never been involved in fettling stock until it runs well is a bit of a joke and if I was that way inclined I could take it as slightly offensive. Perhaps you haven't seen any of my dozen or more exhibition layouts or seen my video released through Activity Media on the subject of making you layout run well. I don't know if anybody on here recalls the 135 wagon train we ran round the 2' 10" curves of Tickhill & Wadworth at a scale 60mph with 2 9Fs on the front but please believe me when I say that I do know how to fettle model railways to make them work! My test on Tickhill was to take the usual length goods train, (15 plus brake van) and to reverse it, at full speed, round the layout. Once I could do that, I was satisfied that my running was not likely to give any problems. Which it didn't until visiting locos appeared. We had 3 0-8-0 tender locos on Tickhill. One was mine and built rigid. Two were visitors built by a good friend and were sprung. Round the tight curves, the leading wheels of the sprung ones would very occasionally, ride up and over the rail at baseboard joints, if there was the slightest misalignment. The rigid one sailed round and never gave a problem. I reckon that the reason (more science here) is that in order for the rigid one to derail, the wheel would have to lift the whole weight of the loco before it could go up and over. On the sprung locos, the wheel only had to lift a proportion (probably 1/8th depending on equal springing and weight distribution) and so it could do that so much more easily. I have worked in P4 and have some very fine P4 modellers amongst my friends (not counting the several who gave up because they couldn't get stuff to stay on the track) and have seen how much effort they put in to make their layouts work well. I have never said that P4 can't or won't work as I do fully understand what it is all about. I do say that it requires more care, probably more time to fettle and needs greater accuracy in vehicle and track construction than OO or EM. The people who have got good running in P4 have told me that themselves! A single pair of wheels running along a track may well exhibit similar behaviour to the real thing but as has been said, it is the vehicle as a whole that matters. Even a simple short 4 wheeled wagon running round a bend does not have the wheels running dead square along the track. The outer wheel is pointing slightly to the outside of the curve and can tend to want to run against the outside rail. Any idiot can build a straight track and stuff will stay on, maybe even with no flanges but as soon as you introduce curves you have the opportunity, especially if you are propelling vehicles coupled together, of flanges going against the rails. Once again, it is theoretical science versus practical experience and there is only one winner. Just as an afterthought, would those genius engineers like to describe the motion of a rake of 10 short wheel based wagons with slightly rounded buffer heads being propelled round a reverse curve. Thought not! Tony Link to post Share on other sites More sharing options...
billbedford Posted October 23, 2014 Share Posted October 23, 2014 If flanges have little to do with wheels keeping on rails, how come model wheels with the only change being bigger flanges seem to stay on the rails better? "Seem" being the operative word here......... Link to post Share on other sites More sharing options...
billbedford Posted October 23, 2014 Share Posted October 23, 2014 There is a world of difference between a single, coned wheelset and a multi-axle rail vehicle --- not to mention a train of such. Add to that poor gauge tolerance, flatness, wheelset axial runout (all far, far bigger than the prototype, when compared to the TG), throw in a huge dollop of friction and it's not hard to see that model flanges are very necessary. They are a fair number of people with P4 layouts that work to their own satisfaction that disprove your theory........ Link to post Share on other sites More sharing options...
Pyewipe Jct Posted October 23, 2014 Share Posted October 23, 2014 MRJ - the gift that keeps on giving... Link to post Share on other sites More sharing options...
Guest Lyonesse Posted October 24, 2014 Share Posted October 24, 2014 They are a fair number of people with P4 layouts that work to their own satisfaction that disprove your theory........ Sorry Bill, you're the one who appealed to a theoretical physicist for support, not me. Nobody disputes that it's possible to make 4mm trains stay on the rails, most of the time. Although as people have been noting since the 1970s, the typical P4 layout is more of a diorama where a short train moves oh-so-slowy and carefully through the pointwork, rather than a Buckingham-like small railway. (Actually, P4 trains run very slowly, since non-scale gravity means model trains should speed up sqrt(76.2) to get roughly the same dynamic effects as the prototype.) I find it easier to build a scale model of a steam locomotive in P4 than the alternatives; you simply follow prototype dimensions. But I'm happy to accept that some folk need deeper flanges to keep running the trains they wish to run, over the curvatures and pointwork they are forced to adopt. Link to post Share on other sites More sharing options...
John_Hughes Posted October 24, 2014 Share Posted October 24, 2014 Sorry Bill, you're the one who appealed to a theoretical physicist for support, not me. Nobody disputes that it's possible to make 4mm trains stay on the rails, most of the time. Although as people have been noting since the 1970s, the typical P4 layout is more of a diorama where a short train moves oh-so-slowy and carefully through the pointwork, rather than a Buckingham-like small railway. (Actually, P4 trains run very slowly, since non-scale gravity means model trains should speed up sqrt(76.2) to get roughly the same dynamic effects as the prototype.) I find it easier to build a scale model of a steam locomotive in P4 than the alternatives; you simply follow prototype dimensions. But I'm happy to accept that some folk need deeper flanges to keep running the trains they wish to run, over the curvatures and pointwork they are forced to adopt. Well, that sounds clear enough, except that you can't scale down clearances, and the gnat's whisker which keeps the crosshead clear of the cylinders on the prototype will have to be enlarged, and then everything else goes funny too. No wonder so many P4 modellers like inside-cylinder jobs! Link to post Share on other sites More sharing options...
Jol Wilkinson Posted October 24, 2014 Share Posted October 24, 2014 There is a world of difference between a single, coned wheelset and a multi-axle rail vehicle --- not to mention a train of such. Add to that poor gauge tolerance, flatness, wheelset axial runout (all far, far bigger than the prototype, when compared to the TG), throw in a huge dollop of friction and it's not hard to see that model flanges are very necessary. Of those listed, axial runout, especially on loco wheels is probably the biggest factor and the one that caused most problems for me. For OO, with it's wider flangeways, etc. it is not much of a problem There are other factors at play too, bogies that don't rotate freely, gangway/corridor connections exerting side forces through reverse curves and crossovers, buffing forces. However, I choose to model to P4 track/wheel standards because I believe they give better appearance and that the effort is worth it. I learned lessons in modelling P4 which I would still apply if doing EM or OO (although the latter is most unlikely as I consider the compromises are too great). When a friend tried a coach with EM wheels gauged to P4 they hit the tops of the cosmetic chairs on London Road. When I inadvertently fitted a set of Sharman EM wheels to a compensated six wheel chassis, with the B2B set with S4 Society gauges it wouldn't run through the newly built pointwork. I didn't spend time finding out why, simply fitted the correct wheels (when I had I identified the error), which cured the problem. So for me, the option, (and the time/cost) of rewheeling my models isn't practical. It is also possible to see the EM flange solution as something of a sticking plaster, potentially covering up other problems. I'm sure that if you build your locos, stock and track well, then deeper flanges will overcome the occasional glitch, but probably is not the answer to "sloppy" model making. If it works for you, do it, but don't deride those who prefer to stick to the S4 Society's published standards. Some of us are happy to enjoy a challenge and get a lot of satisfaction from making things work. As for those wanting an easy route, I suggest 3 rail may be the answer, with original 1950's wheel specifications. My HD toys used to go around 15" curves at great speed, rarely falling off. Self cleaning pick ups with return through every wheel. Match that to today's motor/gear technology and DCC, what could be better? Well, that sounds clear enough, except that you can't scale down clearances, and the gnat's whisker which keeps the crosshead clear of the cylinders on the prototype will have to be enlarged, and then everything else goes funny too. No wonder so many P4 modellers like inside-cylinder jobs! Could be that, as model makers, they choose to recreate those early railways that tended to use inside valve locos. The majority of P4 modellers I know model the pre group era, the rest do one of the big four. Just out of interest, here is a picture of an outside cylinder loco to P4 standards, the kit designed with OO, EM and P4 chassis options and built by someone who usually models in OO. Link to post Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.