Kenton Posted October 14, 2009 Share Posted October 14, 2009 Over on my blog I have reached a point of indecision and though I would air the subject here for wider discussion: Briefly - I have an 0-4-0 chassis to build in OO (with the added complication of a jackshaft). As I see it (ignoring the kit for the moment) there are the following options: 1. Rigid - bearings soldered in the frame for all axles. 2. Semi-sprung - fixed bearing drive axle and jackshaft and independent hornblocks on non-driven axle. 3. Independently sprung - fixed jackshaft and hornblocks on both axles. 4. Beam equalised springing -fixed jackshaft and hornblocks on both axles with a sprung pivot beam on each side. 5. Compensated - unclear beam arrangement that I'll leave you to ponder upon from the kit instructions: For the compensated option parts (2) are swinging arms pivoted at the rear of the frames and passing round the jackshaft axle. Four of these are provided, solder together in pairs, this should provide sufficient bearing surface for the trailing axle. A pin or a rivet can be used as a pivot, the knife edge (5) locates in a half etch on the frames spacer above the axle. [Ed.] More details of this in the blog comments section. Your opinions and suggestions on the subject would be most welcome Link to post Share on other sites More sharing options...
5XP Posted October 14, 2009 Share Posted October 14, 2009 Over on my blog I have reached a point of indecision and though I would air the subject here for wider discussion: Briefly - I have an 0-4-0 chassis to build in OO (with the added complication of a jackshaft). As I see it (ignoring the kit for the moment) there are the following options: 1. Rigid - bearings soldered in the frame for all axles. 2. Semi-sprung - fixed bearing drive axle and jackshaft and independent hornblocks on non-driven axle. 3. Independently sprung - fixed jackshaft and hornblocks on both axles. 4. Beam equalised springing -fixed jackshaft and hornblocks on both axles with a sprung pivot beam on each side. 5. Compensated - unclear beam arrangement that I'll leave you to ponder upon from the kit instructions Your opinions and suggestions on the subject would be most welcome Hi Kenton it all depends how much work you want to make for yourself, Im a b*ugger for this as I always seem to complicate things here. You probably have more experience here than me so Im not going to try and teach you to suck eggs Ive pondered that piece from your instructions and without really seeing the chassis its complete gobblety ###### to me.... It would function perfectly ok as a rigid chassis but as I said you already know all this otherwise I would go for one fixed axle and one on a fixed beam or I cant see why it cant be made sprung on both axles if you dont mind the extra work, I dont know if you have enough room for springy beams as your gearbox may hinder this. Of course we both know this is overkill for 00....... Darren. Link to post Share on other sites More sharing options...
Adam Posted October 14, 2009 Share Posted October 14, 2009 I can't see any reason* to do anything more complicated that what Darren or Industrial suggest. All the 0-4-0 chassis I've built were done this way, and the most recent (a Fowler diesel) does indeed have a jackshaft. All seem to work just fine, so long as the wheels are clean at any rate... Adam *Other than personal whim of course. Link to post Share on other sites More sharing options...
Bruciethefish Posted October 15, 2009 Share Posted October 15, 2009 In my experience, a 4-coupled chassis just needs a central bar bearing on the unpowered axle, which can be allowed a little float by making the chassis holes slightly oval, or done properly with hornblocks... Beams & springs aren't neccessary, just allow one axle to rock, & you're sorted.... Link to post Share on other sites More sharing options...
Kenton Posted October 15, 2009 Author Share Posted October 15, 2009 The S4 people have a thorough document on their site about it: Iain Rice has written a book on chassis construction, worth a read anyway, but generally uses the same principles. ISBN 1874103100 Thanks - the S4 link was given in the blog page along with my overall opinion on it. I have, and am well aware of the book and can also recommend it to anyone new to kitbuilding out there. However, I was really looking for a consensus of opinions on here, along with personal experiences, rather than a specific how to do it. it would have been nice to have been able to include a poll Link to post Share on other sites More sharing options...
28ten Posted October 15, 2009 Share Posted October 15, 2009 Fixed jackshaft and CSB. I wouldn't bother with indivudal springs. Link to post Share on other sites More sharing options...
buffalo Posted October 15, 2009 Share Posted October 15, 2009 However, I was really looking for a consensus of opinions on here, along with personal experiences, rather than a specific how to do it. it would have been nice to have been able to include a poll Your mention of "...personal experiences..." suggests that you are really after informed opinions. I very much doubt whether a poll would give you that Fixed jackshaft and CSB. I wouldn't bother with indivudal springs. I'm reasonably convinced that CSB is a good solution for more complex chassis with three or more axles. How well does it work on an 0-4-0? Does it offer any real advantage over a simple three-point suspension, i.e. one fixed, one rocking axle? I would be concerned that it might result in a lot of pitching motion, especially if the weight was fairly evenly distributed and so the spring rates on each axle were similar. I hasten to add that I haven't tried it so may be completely wrong, so any personal experience or informed opinion, especially from those who have tried both would be very interesting. Nick Link to post Share on other sites More sharing options...
Kenton Posted October 15, 2009 Author Share Posted October 15, 2009 I'm going to ask - because I reckon others may also be wondering - the abbreviation CSB ? Link to post Share on other sites More sharing options...
buffalo Posted October 15, 2009 Share Posted October 15, 2009 I'm going to ask - because I reckon others may also be wondering - the abbreviation CSB ? CSB is Continuous Spring Beam. A piece of springy wire (guitar string, etc) runs along each side of the chassis. The 'beam' passes through an attachment point on each hornblock. At each end and between the hornblocks, the beam passes through attachment points on the frames. Thus each hornblock is individually sprung, but the beam provides some compensation between adjacent axles. See another of the CLAG articles: http://www.clag.org....eam-annex3.html Nick Link to post Share on other sites More sharing options...
28ten Posted October 15, 2009 Share Posted October 15, 2009 Your mention of "...personal experiences..." suggests that you are really after informed opinions. I very much doubt whether a poll would give you that I'm reasonably convinced that CSB is a good solution for more complex chassis with three or more axles. How well does it work on an 0-4-0? Does it offer any real advantage over a simple three-point suspension, i.e. one fixed, one rocking axle? I would be concerned that it might result in a lot of pitching motion, especially if the weight was fairly evenly distributed and so the spring rates on each axle were similar. I hasten to add that I haven't tried it so may be completely wrong, so any personal experience or informed opinion, especially from those who have tried both would be very interesting. Nick As long as the CoG is between the wheels it shouldn't be a problem. My experience is 7mm so I could be wrong for 4mm! The thing to avoid is excess movement, about 1mm should be sufficient. Link to post Share on other sites More sharing options...
Kenton Posted October 15, 2009 Author Share Posted October 15, 2009 CSB is Continuous Spring Beam. A piece of springy wire (guitar string, etc) runs along each side of the chassis. The 'beam' passes through an attachment point on each hornblock. Ah ! Option 4 or another variant of it. But doesn't this conflict with 28ten's description Fixed jackshaft and CSB. I wouldn't bother with individual springs. Either hornblocks or no hornblocks ? CSB ? <br />As long as the CoG is between the wheels it shouldn't be a problem. I was trying not to be too specific to the kit - trying to keep that for the blog discussion thread - but with the drive on the leading axle of an 0-4-0 it is going to be quite unlikely that the CoG (center of gravity) is going to be central. Even more so if the motor/gear combination is selected different from the kit-designer's recommended. True, there may be space for addition weight to be added to adjust this - but a precise CoG ? Link to post Share on other sites More sharing options...
Miss Prism Posted October 15, 2009 Share Posted October 15, 2009 Short-wheelbase sprung 0-4-0s, whether CSB or individual springs for each axle, can be quite 'lively' in terms of pitch motion, as Bullalo notes. Much depends on the actual springrate adopted. My experience of seeing sprung 0-4-0s is that the springs should be as hard as possible - soft coils are definitely not to be recommended in my opinion. A hard-sprung 0-4-0 will not be as adept at coping with gross track irregularities as a compensated 0-4-0, but at least the sprung version will not be prone to tranverse roll instability like a compensated 0-4-0 can be. Choose your poison. Levelling a CSB 0-4-0 can be difficult, and demands a precise CofG positioning. The length of Kenton's particular loco helps in this respect, there being a bit of room both fore and aft to balance added weight to get the thing level. Levelling an 0-4-0 is easier if it has individual adjustable axle springs (a la Bradwell), such height adjustability allowing a bit more leeway on the actual CofG position. Again, choose your poison. In the meantime, Kenton has to take a view on whether any of the above should be applied to his actual build, or whether a simpler compensation solution may be more appropriate for the time he is willing to spend on the thing. Kenton's problem with his particular kit is that the CofG is likely to lay aft rather than forward, and that could bring significant instability problems in a compensated solution if the fixed axle is the front driver. Link to post Share on other sites More sharing options...
28ten Posted October 15, 2009 Share Posted October 15, 2009 Short-wheelbase sprung 0-4-0s, whether CSB or individual springs for each axle, can be quite 'lively' in terms of pitch motion, as Bullalo notes. Much depends on the actual springrate adopted. My experience of seeing sprung 0-4-0s is that the springs should be as hard as possible - soft coils are definitely not to be recommended in my opinion. A hard-sprung 0-4-0 will not be as adept at coping with gross track irregularities as a compensated 0-4-0, but at least the sprung version will not be prone to tranverse roll instability like a compensated 0-4-0 can be. Choose your poison. Good point, I should have mentioned spring rate, one of the plus points of CSB's is the ease of tweaking the spring rate. I have never successfully set up individual sprung axles, there is always some slight difference in one corner! I would imagine this is worse in 4mm I assume you are using wipers? whatever you choose weight distribution will be a key factor in success, but my gut feeling is that a CSB will be more 'tweakable' Heres the CSB at CLAG if you haven't seen it Link to post Share on other sites More sharing options...
28ten Posted October 15, 2009 Share Posted October 15, 2009 I should add that on my 14xx I went for CSB on the front drivers and a beam on the trailing axle this being the most pragmatic solution, after I experimented with springing at the rear, obviously in 7mm I have a bit more mass to worry about. Link to post Share on other sites More sharing options...
Miss Prism Posted October 15, 2009 Share Posted October 15, 2009 I would imagine this is worse in 4mm The 7mm scale devils have all the best tunes... (where's the green with envy emoticon?) Link to post Share on other sites More sharing options...
RMweb Premium Michael Edge Posted October 15, 2009 RMweb Premium Share Posted October 15, 2009 I've tried to make the instructions as short and clear as I can, they should be read in conjunction with the drawing provided. The leading (driving) axle is fixed, the trailing axle runs in the beams (swinging arms), which are pivoted as far back as possible, i.e. behind the jackshaft. to provide more bearing surface they are doubled. The axle is thus free to move up and down in the larger hole in the frames (axle bush size). The knife edge fits over the centre of this axle to allow it to rock, thsi gives full three point compensation without fiddling around with hornblocks, springs or anything else. Since all the components run in etched holes, the accuracy of the wheelbase is preserved without any fitting. Michael Edge Link to post Share on other sites More sharing options...
Miss Prism Posted October 20, 2009 Share Posted October 20, 2009 Given the wheelbase is held from the fixed front axle by the pitch of the coupling rods, and that hornblocks have been intentionally omitted on the rear axle, what function do the 'swinging arms' provide? Link to post Share on other sites More sharing options...
Kenton Posted October 20, 2009 Author Share Posted October 20, 2009 Michael Thanks for your expanded information regarding the suspension design to the kitbuild in progress. I also welcome any other pointers and inside knowledge that you may have to offer along the way Those that are following my blog will see that despite my initial belief in hornblocks, I have plumped to build this one "as intended". But I hope that does not end this discussion on the general subject of 0-4-0 suspension. Link to post Share on other sites More sharing options...
Poor Old Bruce Posted October 21, 2009 Share Posted October 21, 2009 Many years ago I did a K's Midland Johnson 0-4-0ST. Having filed some vertical movement in the bearings of the non-powered axle I soldered a stretcher between the frames above that axle. The stretcher had a tapped hole for a 2mm screw which bore down on the axle so that the loco could be leveled. Solder or locktite a lock nut when set up. It workrd for me. Richard Link to post Share on other sites More sharing options...
buffalo Posted October 21, 2009 Share Posted October 21, 2009 Given the wheelbase is held from the fixed front axle by the pitch of the coupling rods, and that hornblocks have been intentionally omitted on the rear axle, what function do the 'swinging arms' provide? As I understand it, the arms provide the bearings for the rear axle and keep it parallel with the front axle. The rear axle passes through larger holes in the actual frames so, without them, the wheelbase is not constrained and the axle could rotate slightly about a vertical as well as horizontal axis. Nick Link to post Share on other sites More sharing options...
bertiedog Posted October 21, 2009 Share Posted October 21, 2009 Only a test posting as I tried posting on this thread and got nowhere, Stephen Well it seems to be working again, will post properly later. many thanks, Stephen. Link to post Share on other sites More sharing options...
Miss Prism Posted October 21, 2009 Share Posted October 21, 2009 As I understand it, the arms provide the bearings for the rear axle and keep it parallel with the front axle Nick - can one therefore assume the kit designer has little confidence in the rods keeping the axles parallel? Link to post Share on other sites More sharing options...
Adam Posted October 21, 2009 Share Posted October 21, 2009 Nick - can one therefore assume the kit designer has little confidence in the rods keeping the axles parallel? Hang on. My understanding of the system described, based upon Mike Edge's reply and viewing Kenton's workbench blog, is that these 'swinging arms' in fact have a similar function to hornblocks (i.e. allowing vertical motion of the axle), but because this is all designed in, it should be self-jigging. If other words, the bits designed into the kit will do the same job as hornblocks without the need to source, fit and set up hornblocks. The amount of vertical travel is limited by the hole in the frames - which is etched to the size of an axle bush. If everything fits and the dimensions match (from my experience of Mike's kits this is a given), it should work just as well as 'converntional hornblocks, have less margin for error, and be quicker to set up. Next time i build one of Mike's kits, I'll have to put my money where my mouth is and give it a go... Adam Link to post Share on other sites More sharing options...
Kenton Posted October 21, 2009 Author Share Posted October 21, 2009 For those not following the blog .... t't' so we can all see in detail what is being talked about. I've also commented on Miss Prism's question on the blog - just in case it was missed Link to post Share on other sites More sharing options...
buffalo Posted October 21, 2009 Share Posted October 21, 2009 Nick - can one therefore assume the kit designer has little confidence in the rods keeping the axles parallel? I don't think so, surely the coupling rods would only do this if the axles were fixed, or only allowed to move vertically? As it is, the hole in the frames is round and larger than the axle. You could only keep the axles parallel if it was a vertical slot that prevented fore and aft movement of the axle. Hang on. My understanding of the system described, based upon Mike Edge's reply and viewing Kenton's workbench blog, is that these 'swinging arms' in fact have a similar function to hornblocks (i.e. allowing vertical motion of the axle), but because this is all designed in, it should be self-jigging. If other words, the bits designed into the kit will do the same job as hornblocks without the need to source, fit and set up hornblocks. The amount of vertical travel is limited by the hole in the frames - which is etched to the size of an axle bush. Yes, other than minute differences in geometry, that is indeed the effect. Nick ps. as with the old RMweb, these parallel discussions in two different places can be a bit confusing... Link to post Share on other sites More sharing options...
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