Clem Posted May 7, 2013 Share Posted May 7, 2013 A quick question for anyone in the know..... After modelling for some years in P4, the size of my proposed layout has dictated that a move to EM is sensible due to the quicker progress that can be made on rolling stock. However, I have a part built LNER K2 chassis in P4 which I build with a slightly narrow width (for P4) of 16.0 mm. The back to back of EM is 16.5mm - Does anyone know what is the maximum recommended with of an EM chassis? I can't seem to find any information on that in the EM Society manual. I realise it's not ideal but I was originally thinking of building a new chassis in EM for the K2 (which is an old Nucast kit already built) but if it saves me the time of measuring it out and cutting out again, it would be a help. Thanks in anticipation.... Link to post Share on other sites More sharing options...
RMweb Premium t-b-g Posted May 7, 2013 RMweb Premium Share Posted May 7, 2013 I am not sure that there is a set standard for the width over the frames. It can vary quite a bit depending on such things as the wheel arrangement, curvature of track and even types of wheel used. A 4 coupled loco needs virtually no sideplay so the frames can be wider etc. Some EM modellers, myself included, have been using a slightly wider B2B for a while. The 16.5mm was set way back when, at a time when most EM modellers were still using old fashioned Romford and Hamblings wheels. Most more recent wheels, such as Gibsons or Ultrascale (plus Sharmans) are narrower and will work perfectly well with a B2B of 16.8mm. I do know of one loco in EM, built from a Dave Bradwell J27 kit with the fold up frame built as intended, to the P4 dimensions, which manages well round 3' radius curves. At 16mm though, you will only get away with it if you have a tiny amount of bearing on the outside of the frames, wheels without big bosses on the back and large radius curves with little or no sideplay but given those, you have a fighting chance! Good luck! Tony Link to post Share on other sites More sharing options...
Miss Prism Posted May 7, 2013 Share Posted May 7, 2013 Your choice of wheels is likely to be a critical factor. If the rear bosses protrude (typically) 0.25mm from the flange back, that gets the frame width down to 16mm max, and a little bit of sensible sideplay (typically 0.5mm, on both sides of course) on the middle axle brings the frame width down to 15mm max, but you might not need quite this amount of sideplay in EM with 16.5mm back-to-backs. Any protrusion of hornblock face outside of the frame will also affect the sums as well. In extremis, you could cheat and detach the middle frame spacers and take say 1mm off their width, i.e. squeeze the middle of the frame in. Link to post Share on other sites More sharing options...
Gordon A Posted May 7, 2013 Share Posted May 7, 2013 I suggest the maximum width of your frames is determined by the minimum radius you wish the loco to go round and its wheel base. The longer the wheelbase the more sideplay you will need for a given radius. I tend to draw out a section of curve to the minimum radius, then mark the axle centres on a straight piece of card. Place the two fixed axles on the curved line then measure the distance from the straight card edge to the curve, and add any other things like bosses on the back of wheels and any wheel bearing protrusion to ensure you have enough sideplay. Gordon A Bristol Link to post Share on other sites More sharing options...
Clem Posted May 7, 2013 Author Share Posted May 7, 2013 Cheers, thanks for replies. The P4 wheels on at the moment are Sharman but in EM I intend to use either Gibson or Ultrascale. The chassis is sprung with the old plastic kean-maygib springing units. I never felt happy gluing these to brass frames as the instructions suggested, so the method I used was to use thixofix to glue an inner plasticard skin on the inside of the frames (pinned also in 2 or 3 places) and then set the hornblocks in position with the usual perseverence jigs and butatone to fix them in position. It's worked well on other chassis I've built. The reason I've explained all this is that the hornblocks ride flush, even just inside of the frame exteriors. My big worry is the wheel rims touching and shorting on the frames. Thanks for reply Miss Prism - I think the measurements you've suggested make complete sense but I don't want to squeeze the middle as this would throw the measurements of the coupling rods (already made up of course) out. I think, Tony, your advice to set the wheels at 16.8 may just be worth a shot, although some of my pointwork, particularly in the hidden sidings, leaves a bit to be desired and anything other than 16.5 may, just may cause problems. On the other hand it may be just a case of implementing a route availability over the layout! I have got tight curves on the layout (3'1" minimum) but I suppose the worst that can happen is I have to make a new chassis in EM. Although trying this out is not imminent, I will be looking to do it in the next couple of months. Thanks again. Link to post Share on other sites More sharing options...
Clem Posted May 7, 2013 Author Share Posted May 7, 2013 Cheers for the reply, Gordon - I may have to gauge-widen a little round the curves to get it to run. It is a long wheel base - 7'3"-9'0" ..... And then again, if that takes too much work, maybe it will require a new chassis... Link to post Share on other sites More sharing options...
RMweb Gold Enterprisingwestern Posted May 7, 2013 RMweb Gold Share Posted May 7, 2013 If your tracklaying is half decent, I'd give a b to b of 16.8 a shot using the existing wheels, saves spending more money than you are forced to? Mike. Link to post Share on other sites More sharing options...
Clem Posted May 7, 2013 Author Share Posted May 7, 2013 If your tracklaying is half decent, I'd give a b to b of 16.8 a shot using the existing wheels, saves spending more money than you are forced to? Mike. Mike... Ha ha! that's the big question. I've recently completed a scissors crossover into the goods yard/low-loading bay. Nothing derails on it but it is a bit clunky... not to mention some of the tight curves through crossings in the hidden sidings. No... I might get to a quarter decent but half is stretching it. :-) I did run a fully compensated twin-set for a while with P4 wheels for a while but I found that they did derail more often than any other vehicle. I've now replaced the wheels and they no longer derail. I think it's difficult with P4 profile wheels over the wider check rails in EM. At this stage, I'm going to try Gibson or Ultrascale EM wheels set to 16.8. I'll save the other wheels for some small P4 project in the future. Link to post Share on other sites More sharing options...
RMweb Premium t-b-g Posted May 7, 2013 RMweb Premium Share Posted May 7, 2013 Shorting of the wheels against the frames may well become a factor, especially if they are on some form of springing/compensation sytem. One of the reasons I usually build my EM locos rigid is so that the wheels can be close to the frames and brakes etc. with no risk of touching. A couple of slightly off the wall suggestions for you! Insulate the outside of the frames behind the wheels with something like thin black plasticard or even a thin smear of araldite. Or replace the frame spacers (one at a time so they don't all fall apart) with pcb/fibreglass so that you can split the frames electrically, then it doesn't matter much if the wheels are close. Either that or solder some PCB onto the existing spacers then gap them afterwards. You will still need to sort the cylinders/brakes etc. out but that shouldn't be too difficult. Interesting project! I hope you let us know how you get on. Cheers, Tony Link to post Share on other sites More sharing options...
Gordon A Posted May 7, 2013 Share Posted May 7, 2013 How difficult would it be to cut through all the spacers, set both halves up on an assemly jig and rejoin the two halves the correct distance appart? Gordon A Bristol Link to post Share on other sites More sharing options...
Clem Posted May 7, 2013 Author Share Posted May 7, 2013 Shorting of the wheels against the frames may well become a factor, especially if they are on some form of springing/compensation sytem. One of the reasons I usually build my EM locos rigid is so that the wheels can be close to the frames and brakes etc. with no risk of touching. A couple of slightly off the wall suggestions for you! Insulate the outside of the frames behind the wheels with something like thin black plasticard or even a thin smear of araldite. Or replace the frame spacers (one at a time so they don't all fall apart) with pcb/fibreglass so that you can split the frames electrically, then it doesn't matter much if the wheels are close. Either that or solder some PCB onto the existing spacers then gap them afterwards. You will still need to sort the cylinders/brakes etc. out but that shouldn't be too difficult. Interesting project! I hope you let us know how you get on. Cheers, Tony Shorting of the wheels against the frame - yeah that's my worry. And if I think if it comes to altering the frame spacers, I may as well dismantle and rebuild with narrower spacers. I think if the wheels begin to touch, araldite or plasticard would soon wear through. it is interesting as it is so tantalisingly close to being definitely useable. I have also thought of removing the paint and thinning the width of the frames from the 0.6mm depth each side. - I might make another 0.4mm that way. - Anyway, I will report back on all attempts to solve the problem. Thanks again for replies. Link to post Share on other sites More sharing options...
Clem Posted May 7, 2013 Author Share Posted May 7, 2013 How difficult would it be to cut through all the spacers, set both halves up on an assemly jig and rejoin the two halves the correct distance appart? Gordon A Bristol Thanks for the suggestion. Not that easy as it has a locator at the back of the chassis which has been set up just so to fit into the Nucast body. Also I think it may be as easy to just cut out new side frames if it comes to that. I suppose I want it all ways really. I'd like to think that if I ever wanted to re-wheel it in P4 I could. However I have seriously thought along those lines. Thanks Gordon. Link to post Share on other sites More sharing options...
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