chaz Posted December 13, 2012 Share Posted December 13, 2012 Btw, given that a fixed axle confers complete lateral body stability, could you amplify your "Any slackness in the control of axle height is likely to lead to a measure of instability." "instability" was possibly the wrong word. You can set up compensating beams so that the loco sits level. If, for instance, the axle centres and beam pivots are all in the same plane (or the same height above rail level - the natural datum) then the model will sit level and upright, or very nearly so, regardless of what the beams are doing. However if the beams are springy there is an element of unpredictability. This is one of the reasons that I find compensating beams better than springing. Springs are notoriously difficult to adjust in a 7mm model. How do you set them to get the loco sitting level? Making the beams springy means that have sacrificed one of their merits; once they are set up they don't need adjusting. "I suspect our mutual target here is the single compensation beam method." Not entirely. I have an 0-6-0T which has just such a single beam, resting on the top of axles 1 and 2, axle 3 is rigid. The disadvantage of this is that the axles are in sliding hornblocks (but no springs). I moved to twin beams because this eliminated the need for hornblocks - the wheel bearings are soldered into the beams. Works just as well and is arguably easier to set up and certainly cheaper. But there is no one right way - what suits me may not suit you - Rule One applies. Chaz Link to post Share on other sites More sharing options...
chaz Posted December 13, 2012 Share Posted December 13, 2012 For another variation to throw into the melting pot, how about a fixed rear axle, a front axle which has a central pivot and a lightly sprung centre axle, just enough to hold the axle down on the track? I have done it and it works a treat. No beams and the triangle of the three point suspension is spread as widely as possible over the wheelbase. On a six coupled loco with no carrying wheels, I can't see how it matters very much if the weight distribution is equal over all the wheels or if it is mostly on the front and back axles. Tony No reason why this shouldn't work Tony. You will however have to use hornblocks or some equivalent to allow your centre axle to react to the springs. You are quite right about weight distribution. Providing there is enough weight on the centre axle to keep it accurately on the track you can have most of the weight on the outer two. One of my 0-6-0T locos runs with two sprung axles. The leading axle is sprung but with stops to keep the loco level. The centre axle is sprung and can move both up and down. The third axle is rigid. The two sprung axles are in hornblocks. Not that different to the scheme you suggest. I wouldn't do another one this way - but it works fine and will not be subject to a rebuild. And just to restate - a rigid chassis will work fine - no doubt about that - but a compensated or sprung one will work better. The choice between the latter two is not clear-cut but I am now on the side of beam compensation with no need for springs. Need I mention Rule One again? Chaz Link to post Share on other sites More sharing options...
RMweb Premium t-b-g Posted December 13, 2012 RMweb Premium Share Posted December 13, 2012 Btw, given that a fixed axle confers complete lateral body stability, could you amplify your "Any slackness in the control of axle height is likely to lead to a measure of instability." "instability" was possibly the wrong word. You can set up compensating beams so that the loco sits level. If, for instance, the axle centres and beam pivots are all in the same plane (or the same height above rail level - the natural datum) then the model will sit level and upright, or very nearly so, regardless of what the beams are doing. However if the beams are springy there is an element of unpredictability. This is one of the reasons that I find compensating beams better than springing. Springs are notoriously difficult to adjust in a 7mm model. How do you set them to get the loco sitting level? Making the beams springy means that have sacrificed one of their merits; once they are set up they don't need adjusting. "I suspect our mutual target here is the single compensation beam method." Not entirely. I have an 0-6-0T which has just such a single beam, resting on the top of axles 1 and 2, axle 3 is rigid. The disadvantage of this is that the axles are in sliding hornblocks (but no springs). I moved to twin beams because this eliminated the need for hornblocks - the wheel bearings are soldered into the beams. Works just as well and is arguably easier to set up and certainly cheaper. But there is no one right way - what suits me may not suit you - Rule One applies. Chaz I couldn't agree more! The only thing wrong in a discussion like this is when one person tries to say that their ideas and methods are the only way to do something! I have done single beam compensation a couple of times on 0-6-0 tank locos and done away with seperate axle boxes on the leading two axles. As far as I can tell, they don't carry any weight, which is all taken by the beam. All they do is stop the axles moving fore and aft. So I just ran the axles in an axle sized slot in the frames, reinforced front and back with angle soldered directly to the frames. You can set it up easily using the usual coupling rod type jigs. On my centre sprung axle, I just ran the axle in a tube and had a wire spring acting on the top of the tube, one would do in the centre but I chose to put one each side, so they were not visible between the frames. I have played around with many different systems and found that, basically, they all work! My personal preference is still for a well made, square, rigid frame, coupled with well made, flat baseboards and track! If everything is flat to start with, you really don't need wheels that move up and down, especially in my chosen EM Gauge. Decent crossing noses on points and well finished blades do away with the dreaded "lurch", so often put forward as a reason to spring/compensate. Anyway, a good lurch through poor pointwork is probably more realistic than a sprung glide! I have a right mixture of systems running on a number of my layouts and I defy anybody to look at a loco running and tell me which is rigid/sprung/beam compensated. I certainly can't tell the difference and often have to pick up a loco to check which they are, if somebody asks! But as you say, it is very much a case of each to his/her own and I would never dream of telling anybody what they should or shouldn't do. Tony Link to post Share on other sites More sharing options...
chaz Posted December 13, 2012 Share Posted December 13, 2012 I couldn't agree more! The only thing wrong in a discussion like this is when one person tries to say that their ideas and methods are the only way to do something! I have done single beam compensation a couple of times on 0-6-0 tank locos and done away with seperate axle boxes on the leading two axles. As far as I can tell, they don't carry any weight, which is all taken by the beam. All they do is stop the axles moving fore and aft. So I just ran the axles in an axle sized slot in the frames, reinforced front and back with angle soldered directly to the frames. You can set it up easily using the usual coupling rod type jigs. On my centre sprung axle, I just ran the axle in a tube and had a wire spring acting on the top of the tube, one would do in the centre but I chose to put one each side, so they were not visible between the frames. I have played around with many different systems and found that, basically, they all work! My personal preference is still for a well made, square, rigid frame, coupled with well made, flat baseboards and track! If everything is flat to start with, you really don't need wheels that move up and down, especially in my chosen EM Gauge. Decent crossing noses on points and well finished blades do away with the dreaded "lurch", so often put forward as a reason to spring/compensate. Anyway, a good lurch through poor pointwork is probably more realistic than a sprung glide! I have a right mixture of systems running on a number of my layouts and I defy anybody to look at a loco running and tell me which is rigid/sprung/beam compensated. I certainly can't tell the difference and often have to pick up a loco to check which they are, if somebody asks! But as you say, it is very much a case of each to his/her own and I would never dream of telling anybody what they should or shouldn't do. Tony It's always nice when there is agreement, Tony. The bit I like the best in your posting is where you say "I have played around with many different systems and found that, basically, they all work!" I think I might have done a bit of playing around with many different systems myself. Chaz Link to post Share on other sites More sharing options...
N15class Posted December 14, 2012 Share Posted December 14, 2012 Here's three photos of a compensated 0-6-0 chassis I'm working on for a friend... It's 9mm gauge/HOn30 and will have a 50:1 gearbox with a Mashima 1220 motor when it is complete. It's built up from laser cut brass and steel parts, steel turnings, etc... I can build the same chassis down to 5.26mm gauge, using fine scale wheels, with a slightly narrower gearbox. JeffB How did you find the laser cut brass? Thirty years ago we tried it when I was in the clock trade. It left very bad edges, as unlike steel it does not melt spit out. We found that a guilotine left the edge easier to machine. Link to post Share on other sites More sharing options...
JeffB Posted December 14, 2012 Share Posted December 14, 2012 How did you find the laser cut brass? Thirty years ago we tried it when I was in the clock trade. It left very bad edges, as unlike steel it does not melt spit out. We found that a guilotine left the edge easier to machine. I didn't find laser cut brass, I laser cut it myself... I work in the R&D department for an industrial laser manufacturer, and have access to a few different types of lasers. One laser cuts brass much more cleanly than another, and that's the type that I use primarily for cutting my parts. Chaz... I agree with everything you've said about rigid beam compensation. Springy beams, and continous springy beams seem to be the rage now, but I can't really do that effectively in 009/HOn30/HOn2. I prefer rigid beam compensation, and it is much better than a rigid chassis for all the reasons stated. I too have built compensated 0-6-0 chassis with a pair of beams and one rigid axle. In these chassis', I built in a pivot that allows the beams to pivot side to side, as well as fore and aft. As you or someone else has stated, with the one rigid axle, the entire chassis will move (often violently) up or down in areas of trackwork that there's large vertical transistions. Especially point frogs with a large gap between the point and heel. The two beam and single pivoting axle handles such situations better, but still exhibits a visible reaction. I get around this by hand building my points using the narrowest flangeway clearance through the frog as can be used. A razor sharp frog point is also needed to minimize that gap. In instances where commercial points are used (like my son's HOn30 layout that uses Peco "Mainline" 009 points), I've taken to filling the bottom of the frog flangeways with epoxy putty, to minimize the distance that the wheel/chassis has to drop. As someone said... A rigid chassis can be made to run very well, but a compensated one can run better. After building compensated chassis for about 12 years now. I'm fully convinced that this is an undeniable fact. Jeff Link to post Share on other sites More sharing options...
chaz Posted December 14, 2012 Share Posted December 14, 2012 I didn't find laser cut brass, I laser cut it myself... I work in the R&D department for an industrial laser manufacturer, and have access to a few different types of lasers. One laser cuts brass much more cleanly than another, and that's the type that I use primarily for cutting my parts. Chaz... I agree with everything you've said about rigid beam compensation. Springy beams, and continous springy beams seem to be the rage now, but I can't really do that effectively in 009/HOn30/HOn2. I prefer rigid beam compensation, and it is much better than a rigid chassis for all the reasons stated. I too have built compensated 0-6-0 chassis with a pair of beams and one rigid axle. In these chassis', I built in a pivot that allows the beams to pivot side to side, as well as fore and aft. As you or someone else has stated, with the one rigid axle, the entire chassis will move (often violently) up or down in areas of trackwork that there's large vertical transistions. Especially point frogs with a large gap between the point and heel. The two beam and single pivoting axle handles such situations better, but still exhibits a visible reaction. I get around this by hand building my points using the narrowest flangeway clearance through the frog as can be used. A razor sharp frog point is also needed to minimize that gap. In instances where commercial points are used (like my son's HOn30 layout that uses Peco "Mainline" 009 points), I've taken to filling the bottom of the frog flangeways with epoxy putty, to minimize the distance that the wheel/chassis has to drop. As someone said... A rigid chassis can be made to run very well, but a compensated one can run better. After building compensated chassis for about 12 years now. I'm fully convinced that this is an undeniable fact. Jeff Jeff, a couple of points if I may.... "continous springy beams seem to be the rage now" I can't see any advantage to them, and I've have never been swayed by fashion. So, like you, having nailed my colours to the mast of stiff beams I will stay with them "In instances where commercial points are used (like my son's HOn30 layout that uses Peco "Mainline" 009 points), I've taken to filling the bottom of the frog flangeways with epoxy putty, to minimize the distance that the wheel/chassis has to drop." In the past I have glued a triangular piece of plastic into the bottom of the crossing flangeway myself. This obviously works best if all wheels have the same depth flanges. Of course with a little care the drop can be eliminated, all it takes is for the flange depth and height of the packing to match. I haven't done this yet on Dock Green. Chaz Link to post Share on other sites More sharing options...
Ruston Posted December 14, 2012 Author Share Posted December 14, 2012 "coupling rods that match the holes in the frames" - you might be surprised at how often they don't! Funny you should mention this. I've currently got an 0-4-0ST on the workbench. I decided from the start to fit compensation and had a pair of hornblocks and hornguides ready to fit. To align everything I fitted the hornblocks, which were turned on one side to locate in the holes in the frames so that the guides could be fixed to the frames around them, before the blocks were then removed and the material cut away from the frames - basically I ensured that the distance from one axle to the other was exactly the same as it should be. Imagine my annoyance when I fitted the wheels and then found that the rods would not fit, despite all I'd done to keep the distance correct! I must have done it wrong - or so I thought... I'd scanned the etches at actual size before I cut anything from them (I did this as I intend to make a plasticard version of the frames for a static, part dismantled loco) and when I measured the distance between centres on the frames and the rods there was almost 1mm difference! That's probably too much to open out and still expect a brass bush to fit in a round hole but, still thinking it was my fault, I'd filed the edge of the frame and hornblocks to the point that they are now useless. It took a lot of head-scratching, pushing the chassis up and down and watching things closely before I found a solution and it's a proper bodge but, fingers crossed, it looks like it may work and I'll still have compensation on the loco. Link to post Share on other sites More sharing options...
Horsetan Posted December 14, 2012 Share Posted December 14, 2012 ..."continous springy beams seem to be the rage now" I can't see any advantage to them, and I've have never been swayed by fashion. .... I'm not sure you could call CSBs a "fashion". They've been around far too long now to be called a phase or a dalliance or any of the other superficial things that constitute fashion. Link to post Share on other sites More sharing options...
chaz Posted December 15, 2012 Share Posted December 15, 2012 I'm not sure you could call CSBs a "fashion". They've been around far too long now to be called a phase or a dalliance or any of the other superficial things that constitute fashion. Fair enough. I was responding to Jeff's comment "Springy beams, and continous springy beams seem to be the rage now". I wouldn't denigrate their use, I just wouldn't use them myself. Chaz Link to post Share on other sites More sharing options...
JeffB Posted December 15, 2012 Share Posted December 15, 2012 I'm not sure you could call CSBs a "fashion". They've been around far too long now to be called a phase or a dalliance or any of the other superficial things that constitute fashion. I wasn't denigrating their use either, and would agree that they've been around for a long time. Not to create a long drawn out distraction here... But the fact that they've been around a long time, coupled with the fact that their popularity wained for a time, then has come back, would qualify them to some degree as "coming back into fashion"... That said... I think that CSB's are fine idea, but for the small narrow gauge modeling I'm interested in, they are not practical and rigid beam suspension (which has also been around for a long time) is a more viable option. RBS works well, and I like that I can easily set the chassis and coupling height to where I want/need it to be. CSB's make that a little trickier to do, though not impossible. Ultimitely, use what method achieves the desired outcome, for the amount of work you are willing to put into it. Jeff Link to post Share on other sites More sharing options...
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