RMweb Premium Siberian Snooper Posted February 19, 2016 RMweb Premium Share Posted February 19, 2016 If the wheels only derail on that turnout, check the gauge as it may be a little tight. Too reduce the axle length slightly use a smooth engineers file, with the safe edge on the face of the square, I have used this method on errant Romford axles in 4mm. (The safe edge is the one with no teeth on it). Link to post Share on other sites More sharing options...
chaz Posted February 19, 2016 Author Share Posted February 19, 2016 I have just had a look on the gauge 0 guild site for the b 2 b gauge and they quote 29mm for fine scale wheels and 28 mm for coarse scale wheels, so I would try reducing the b 2 b slightly. It's how to do this that's my problem.... If the wheels only derail on that turnout, check the gauge as it may be a little tight. Too reduce the axle length slightly use a smooth engineers file, with the safe edge on the face of the square, I have used this method on errant Romford axles in 4mm. (The safe edge is the one with no teeth on it). OK. I will check the turnout for gauge - my suspicion is that if it is tight it will be between the blades - a bit of gentle filing might be in order. "Too reduce the axle length slightly use a smooth engineers file, with the safe edge on the face of the square...." Fraught with risk? I have no confidence in my ability to do this accurately. What I will try is to remove the wheelset and try replacing the axle (I have some spares) and see if I can get a true 29mm B to B. Chaz Link to post Share on other sites More sharing options...
Giles Posted February 19, 2016 Share Posted February 19, 2016 "If your springs are doing their job, It's possible that they're inhibiting the sideways movement of the pony truck..." That's a valid point, however should that be the case the solution is not to move the spring contact point closer to the pivot - the nearer the spring acting point is to the pivot the less they would press down. If they were level with the pivot they would have no effect at all - think about it! Unfortunately removing the springs does not solve the problem - the loco was built without springs and derailed in reverse. I have progressively increased the spring pressure, to no avail. A low friction sliding plate might answer but the unpainted nickel silver footplate underside is close to that already, don't you think? Chaz Absolutely - that's why I said 'towards', rather than 'to'...... The n/s footplate is good, but the wire has a very high point load because of it's small area. On 10 1/4" locos (for instance) I use two flat plates with grease for this very application. If sorting the back-to-back doesn't cure it (and I hope it does) then you may need to look at the geometry to help - as the pivot is likely to be too close to the pony wheels. Baldrey's Rule defines the ideal position. Since you have the drive gear in the way, the pivot could be simulated either by two splayed links, or by using a radial truck. However, let's hope it's the back to back. Giles Link to post Share on other sites More sharing options...
chaz Posted February 19, 2016 Author Share Posted February 19, 2016 Absolutely - that's why I said 'towards', rather than 'to'...... The n/s footplate is good, but the wire has a very high point load because of it's small area. On 10 1/4" locos (for instance) I use two flat plates with grease for this very application. If sorting the back-to-back doesn't cure it (and I hope it does) then you may need to look at the geometry to help - as the pivot is likely to be too close to the pony wheels. Baldrey's Rule defines the ideal position. Since you have the drive gear in the way, the pivot could be simulated either by two splayed links, or by using a radial truck. However, let's hope it's the back to back. Giles "However, let's hope it's the back to back." I'm hoping, I'm hoping..... changing the pivot geometry would be a nightmare. having a quick look at Baldrey's Rule suggests that the pivot point is ideally somewhere between the rear two driving wheels - that's not going to be possible without a complete rebuild of the frames. I'm not keen. Chaz Link to post Share on other sites More sharing options...
John R Smith Posted February 19, 2016 Share Posted February 19, 2016 Two-tenths of a millimetre on b2b should not cause any problems. On "Maristow" I deliberately set all my wheels to 29.5mm and got much smoother running (less sideways slop). I suspect the use of two springs may be the issue - I would try one central spring, making absolutely sure the pony truck can still pivot sideways freely. John Link to post Share on other sites More sharing options...
Fettster42 Posted February 19, 2016 Share Posted February 19, 2016 Before you start trying to change the b-2-b have you got another set of wheels you could temporarily put in the pony with exact 29mm to see if that does solve it? Link to post Share on other sites More sharing options...
Guest Isambarduk Posted February 19, 2016 Share Posted February 19, 2016 "see if I can get a true 29mm B to B." It's not the back-to-back that is important, it is the back-to-flange-face that matters; for 0 Gauge Fine Standard this is defined by the Gauge 0 Guild Standards as 30.0mm maximum. Incidently, the the Gauge 0 Guild standards give 29mm as a minimum for back-to-back - and I agree with John, +0.2mm is not going to make the difference on its own. I believe the problem lies elsewhere entirely, quite possibly with the PECO Y turnout. David Link to post Share on other sites More sharing options...
3 link Posted February 19, 2016 Share Posted February 19, 2016 (edited) Chaz, If you do decide to go down the route of trimming back the axles, you will be surprised at just how soft a metal that the axles are made of. Martyn. Edited February 19, 2016 by 3 link Link to post Share on other sites More sharing options...
chaz Posted February 19, 2016 Author Share Posted February 19, 2016 Two-tenths of a millimetre on b2b should not cause any problems. On "Maristow" I deliberately set all my wheels to 29.5mm and got much smoother running (less sideways slop). I suspect the use of two springs may be the issue - I would try one central spring, making absolutely sure the pony truck can still pivot sideways freely. John Thanks John. very helpful - I did think that as you say "Two-tenths of a millimetre on b2b should not cause any problems". I will spend some time watching the loco running over the Y point - I will also do some very careful measuring of the gauge through the point. Should that not resolve the problem I will redesign the springing. Link to post Share on other sites More sharing options...
chaz Posted February 19, 2016 Author Share Posted February 19, 2016 (edited) Before you start trying to change the b-2-b have you got another set of wheels you could temporarily put in the pony with exact 29mm to see if that does solve it? No, although I do have some spare axles - but look at my posting #3888 above.... Edited February 19, 2016 by chaz Link to post Share on other sites More sharing options...
John R Smith Posted February 19, 2016 Share Posted February 19, 2016 (edited) Thanks John. very helpful - I did think that as you say "Two-tenths of a millimetre on b2b should not cause any problems". I will spend some time watching the loco running over the Y point - I will also do some very careful measuring of the gauge through the point. Should that not resolve the problem I will redesign the springing. Chaz In my limited experience with the present-day O Gauge scene, I have recently found that the Peco points are, shall we say, somewhat dimensionally challenged in places. The radius of the curved part of the switch should be the same for both the standard RH and LH turnouts and the Y turnout, if you check Peco's specifications. The crossing itself should be straight, not curved, in both. What I have found in my samples is a significant gauge narrowing through the curved side of the switch, which might affect both sides on a Y turnout. One of the problems we face if we use a mix of kit-built and R-T-R stock is an unholy mix of wheel standards too, it would seem. Just compare Heljan with Dapol and Slaters, for example. They are all rather different on flange depth, width and profile, yet we expect them all to glide through the same set of switches and crossings. John Edited February 19, 2016 by John R Smith Link to post Share on other sites More sharing options...
Simond Posted February 19, 2016 Share Posted February 19, 2016 There is the rule, if it falls off all over the place, it's the vehicle, whereas if everything falls off there, it's the track. In this case, it appears that you've sorted everything, except one axle of one vehicle in one place. We've all looked at the "suspension" and even allowing for Baldry's rule, my guess is that the kit wasn't "wrong" and not all N7s fall off regularly. Indeed, there are a lot of locos running round with no springing on their pony trucks, and theoretically wrong pivot positions, and they all manage, fine. And this example manages other paintwork without problem. So perhaps suspicion should be directed at the track. Flangeways, gauge, "top"? Best Simon Link to post Share on other sites More sharing options...
alant Posted February 19, 2016 Share Posted February 19, 2016 Interesting debate and advice. I am no expert on these matters but if all other stock runs through the Y without problem, doesnt it point to the loco as being the problem? Alan. Link to post Share on other sites More sharing options...
Simond Posted February 19, 2016 Share Posted February 19, 2016 Alan Yes, but... this loco (apparently) runs everywhere else without problems! My initial hunch was the loco, well, the pony truck, too. So it is likely some kind of interaction between the loco and that particular piece of track. The truck seems able to droop, and roll, and has a pretty-much acceptable wheelset, and the pivot isn't "right" but isn't "dreadfully wrong" either, so the conclusion seems to be that the track could be the likely culprit. Best Simon Link to post Share on other sites More sharing options...
chaz Posted February 19, 2016 Author Share Posted February 19, 2016 (edited) Interesting debate and advice. I am no expert on these matters but if all other stock runs through the Y without problem, doesnt it point to the loco as being the problem? Alan. The N7 is my only loco with a pony truck (apart from the V2 - which because of its size never shunts and so never runs over this point), all the others are either 0-4-0 or 0-6-0 or are diesels with bogies. it may well be that the propelled pony truck is more sensitive to track problems than the other stock. None of the other locos have ever derailed on the point but when the Tortoise throw crept out of adjustment a few of the lighter wagons did so. I corrected the throw, the wagons stopped derailing but the N7's pony didn't; that's the essence of the problem. But I am much persuaded by John's posting above, with his views on track. Some careful investigations will be made of the point. Ironically I have already done some testing - the N7 was run through the point over and over, at a variety of speeds when I corrected the throw. During those tests I was unable to provoke a derailment. However at the next show it fell off - very frustrating. Chaz PS - I think we have all contributed about as much as we can to what might be going wrong - might I suggest that we put this subject on hold until I have had a chance to do some measuring and further tests. I will report back! Edited February 19, 2016 by chaz Link to post Share on other sites More sharing options...
chaz Posted February 21, 2016 Author Share Posted February 21, 2016 Oy! What's going on? Logged on, went to post in this topic - discovered several postings have vanished. Are gremlins loose in the forum? I think we should be told. Link to post Share on other sites More sharing options...
chaz Posted February 21, 2016 Author Share Posted February 21, 2016 (edited) Uncanny! As I was typing that last post a message came up that "there are 19 new postings - show me". After clicking "Post" I checked and all the missing ones are back. A software problem rather than a loss of data? Chaz PS - If this is the worst thing that happens this year I'm sanguine. Small beer compared with a burst pipe or the stuff that Syrian refugees are having to endure.... Edited February 21, 2016 by chaz Link to post Share on other sites More sharing options...
chaz Posted February 21, 2016 Author Share Posted February 21, 2016 ...and another thing! The counter that counts views has lost 500 or so. Probably the views of those "missing" posts. It's a small matter of little consequence but might help someone to work out where the fault is..... Link to post Share on other sites More sharing options...
raymw Posted February 21, 2016 Share Posted February 21, 2016 The forum software is changing from dc to dcc, and they need a few frog juicers. Link to post Share on other sites More sharing options...
keefr2 Posted February 21, 2016 Share Posted February 21, 2016 The N7 is my only loco with a pony truck (apart from the V2 - which because of its size never shunts and so never runs over this point), . This is probably a completely stupid question Chaz, but is that reason purely because of prototypical practice, or is it that the loco is physically too big to shunt over that point? If the former, could you not try the loco just to see what happens? Keith Link to post Share on other sites More sharing options...
chaz Posted February 22, 2016 Author Share Posted February 22, 2016 This is probably a completely stupid question Chaz, but is that reason purely because of prototypical practice, or is it that the loco is physically too big to shunt over that point? If the former, could you not try the loco just to see what happens? Keith it's not a stupid question Keith. The V2 could run across the point, the clearances etc would allow it - we don't do it "because of prototypical practice" (in fact it's very doubtful if such a big loco would ever have run into a small yard like Dock Green). I could try it when I put baseboard BC up to measure the gauge through the point, check alignments and any cross level variations. Not too sure though if it will tell me much if it derails or if it doesn't.... I suppose if it does derail it points the finger more at the point - but I will still need to do the measuring I plan to do. Chaz Link to post Share on other sites More sharing options...
Simond Posted February 22, 2016 Share Posted February 22, 2016 Chaz When you do your tests & measurements, perhaps try both locos in both directions, and borrow one of MrsChaz' handy little make-up mirrors to watch the other side of the loco as well... Waiting with bated breath... Simon Link to post Share on other sites More sharing options...
Robin Gristwood Posted February 22, 2016 Share Posted February 22, 2016 Another option to see what's happening is to use your video camera to record the movement through the potentially defective Peco Y point and hopefully capture the moment it derails. That will allow you to re-run the video to see exactly where its happening. Just a thought. Link to post Share on other sites More sharing options...
chaz Posted February 23, 2016 Author Share Posted February 23, 2016 Chaz When you do your tests & measurements, perhaps try both locos in both directions, and borrow one of MrsChaz' handy little make-up mirrors to watch the other side of the loco as well... Waiting with bated breath... Simon I will have no difficulty watching the loco's progress from both sides as the retaining wall adjacent to point #2 is removeable - it has to be as it crosses a baseboard join. In fact should I have to, any of the retaining walls can be removed as they are fixed with wood screws. "Waiting with bated breath..." Breath again - I plan to do the testing on Thursday. Link to post Share on other sites More sharing options...
chaz Posted February 23, 2016 Author Share Posted February 23, 2016 Another option to see what's happening is to use your video camera to record the movement through the potentially defective Peco Y point and hopefully capture the moment it derails. That will allow you to re-run the video to see exactly where its happening. Just a thought. Good idea, it will cost nothing (let's hear it for digital compacts). Link to post Share on other sites More sharing options...
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