RMweb Premium Compound2632 Posted August 28, 2018 RMweb Premium Share Posted August 28, 2018 Are these angles measured from the normal to the axle centreline rather than, as Keith assumes, the total angle subtended by the cone in each case? Comes to the same thing for the axle point, of course. Link to post Share on other sites More sharing options...
Simond Posted August 29, 2018 Share Posted August 29, 2018 However you measure the angles, provided you do it the same for both cup and point, the point has to be sharper than (ie fewer degrees) than the cup for a “pin-point” bearing to work. The whole point (sorry) of any “wheel & axle” with a plain bearing is that the radius of the effective bearing is as small a fraction as possible of the radius of the wheel, as this minimises the effects of the bearing friction. Best Simon Link to post Share on other sites More sharing options...
RMweb Premium NCB Posted August 29, 2018 RMweb Premium Share Posted August 29, 2018 However you measure the angles, provided you do it the same for both cup and point, the point has to be sharper than (ie fewer degrees) than the cup for a “pin-point” bearing to work. The whole point (sorry) of any “wheel & axle” with a plain bearing is that the radius of the effective bearing is as small a fraction as possible of the radius of the wheel, as this minimises the effects of the bearing friction. Best Simon Don't think so. If the angle is measured from a normal to the axle centreline, then to get a sharper axle point the angle needs to be greater (more degrees) than the angle of the bearing cone. "Sharper" can be misleading. The point itself shouldn't be sharp i.e. it should be a tad blunt. The bearing surface of the axle is then a very small circle, rather than a sharp point. Link to post Share on other sites More sharing options...
Simond Posted August 30, 2018 Share Posted August 30, 2018 (edited) I’m not sure what you mean by measuring from a normal to the centreline of the axle, as that would be a plane. I can’t see any advantage in measuring in such a way. I think most designers would specify either the included angle, or the angle from the cone to the centreline, ie half the included angle, ie the angle by which you would set over the top slide, if using a lathe to make your own axles. In simple terms, the point has to go to the end of the cup. If the point is less pointed than the cup is, it will not reach, as the full diameter of the axle will touch the cup first. That will be less free running than if the point touches first. Best Simon Edited August 30, 2018 by Simond Link to post Share on other sites More sharing options...
81E Posted September 21, 2018 Share Posted September 21, 2018 I'd try and find a K's kit on eBay. Most are white metal, but there was a plastic version available for a while. The roof profile is much the same as the Ratio one. AFAIK the roof profile only changes with different body widths. I've modified one to an arc roof O4 for variety. Standard P4 and EM axles* are 26mm over pinpoints with a 60° angle on the pin-point and 2mm diameter. This mates with 55° top hat bearings designed to fit axleguards at 24mm spacing. (I believe there are drawings on the EMGS website). Hormby (metal wheel) axles used to be 26mm too, but now appear to have adopted the NMRA specification of 25.4mm/1". Why? * Should be used for 00 too. Note Romford/Markits axles are 26mm, but their bearings are non-standard - details on their website. EDIT Continental axles are different again, shorter still, but they are intended for H0. Details on the MOROP site (in French and German - they are looking for someone to translate into English.) Having had some trouble getting hold of the Ks kit I decided to 3D print my own. These too are available from Shapeways as a 3 part kit (excluding buffers and wheels) with two different body types. Diagram O2 https://www.shapeways.com/shops/stafford_road_model_works?section=00+GWR+Dia+O2+6+Wheeled+Siphon&s=0 Diagram O4 https://www.shapeways.com/shops/stafford_road_model_works?section=00+GWR+Dia+O4+6+Wheeled+Siphon&s=0 (please note I had to turn the flanges off the centre wheels). If anyone is tempted by one of these I would recommend using Markits turned brass coach buffers rather than my own as mine are a bit fragile. 3 Link to post Share on other sites More sharing options...
sp1 Posted September 21, 2018 Share Posted September 21, 2018 Having had some trouble getting hold of the Ks kit I decided to 3D print my own. These too are available from Shapeways as a 3 part kit (excluding buffers and wheels) with two different body types. Diagram O2 https://www.shapeways.com/shops/stafford_road_model_works?section=00+GWR+Dia+O2+6+Wheeled+Siphon&s=0 Diagram O4 https://www.shapeways.com/shops/stafford_road_model_works?section=00+GWR+Dia+O4+6+Wheeled+Siphon&s=0 (please note I had to turn the flanges off the centre wheels). If anyone is tempted by one of these I would recommend using Markits turned brass coach buffers rather than my own as mine are a bit fragile. Those look nice - I already have a K’s one purchased from eBay a few years ago from ‘Hayfield’ of this parish (if my memory is correct) but I think I’ll be saving up some pennies for a few of yours! Link to post Share on other sites More sharing options...
Il Grifone Posted October 8, 2018 Share Posted October 8, 2018 (edited) Is that correct? If so the pin point won't do anything as the axle cannot reach right into the bearing. The bearing surely must have a greater angle than the axle. Cheers Hi Keith, It looks like I've got it the wrong way round! The pin point angle is not unduly critical anyway. I always turn them by eye. The problem I find is getting the axle length right as it's easy to take too much off. I'll see if I can unearth the drawings. They're stashed away somewhere. I did find this http://www.clag.org.uk/bearing-interface.html David Edited October 8, 2018 by Il Grifone Link to post Share on other sites More sharing options...
81E Posted January 16, 2019 Share Posted January 16, 2019 As a bit of an experiment and by way of using up some surplus Airfix siphon bogies I have developed a GWR Siphon J I hope to develop a couple of passenger coaches or a Milk brake but haven't decided which yet. However, I will need to test the water post Brexit as I am worried that import duties will make the process beyond my price range 1 Link to post Share on other sites More sharing options...
timbowilts Posted June 22, 2019 Share Posted June 22, 2019 On 16/01/2019 at 00:22, 81E said: As a bit of an experiment and by way of using up some surplus Airfix siphon bogies I have developed a GWR Siphon J I hope to develop a couple of passenger coaches or a Milk brake but haven't decided which yet. However, I will need to test the water post Brexit as I am worried that import duties will make the process beyond my price range Any development on this? Tim T Link to post Share on other sites More sharing options...
Coach bogie Posted June 23, 2019 Share Posted June 23, 2019 You can produce a reasonable Siphon J by sanding down a Lima Siphon G body, clad in planked plasticard, ad your home made fittings. Replace bogies and buffers. This one must be thirty years old now and needs a bit of a makeover. Mike Wiltshire 10 Link to post Share on other sites More sharing options...
GWR8700 Posted July 31, 2019 Share Posted July 31, 2019 Anyone know if Slater's are intending to re-introduce their GWR coaches like they have done with their Midland wagons? Link to post Share on other sites More sharing options...
The Great Bear Posted July 31, 2019 Share Posted July 31, 2019 2 hours ago, GWR8700 said: Anyone know if Slater's are intending to re-introduce their GWR coaches like they have done with their Midland wagons? There was mention of this on this site at the start of the year, well in relation to the toplights, but I haven't seen any more news since then 1 Link to post Share on other sites More sharing options...
GWR8700 Posted July 31, 2019 Share Posted July 31, 2019 3 hours ago, The Great Bear said: There was mention of this on this site at the start of the year, well in relation to the toplights, but I haven't seen any more news since then That would be great too. Link to post Share on other sites More sharing options...
lofty1966 Posted July 31, 2019 Share Posted July 31, 2019 Doesn't Dynamic Dunn at CooperCraft empty space emporium have the moulds ? Link to post Share on other sites More sharing options...
RMweb Premium Siberian Snooper Posted August 1, 2019 RMweb Premium Share Posted August 1, 2019 8 hours ago, lofty1966 said: Doesn't Dynamic Dunn at CooperCraft empty space emporium have the moulds ? Don't think so. Link to post Share on other sites More sharing options...
RMweb Premium Compound2632 Posted August 1, 2019 RMweb Premium Share Posted August 1, 2019 Apparently, one thing that held up the re-issue of the Midland wagon kits was that David White didn't have any copies of the instructions. So if you have instructions for the carriage kits, it might be worth letting him know? But another part of the story seems to be, it'll happen when it happens, given other commitments. No inside knowledge myself, this is just what I've gleaned from the comments of others. Link to post Share on other sites More sharing options...
Denbridge Posted August 21, 2019 Share Posted August 21, 2019 On 01/08/2019 at 09:04, Compound2632 said: Apparently, one thing that held up the re-issue of the Midland wagon kits was that David White didn't have any copies of the instructions. So if you have instructions for the carriage kits, it might be worth letting him know? But another part of the story seems to be, it'll happen when it happens, given other commitments. No inside knowledge myself, this is just what I've gleaned from the comments of others. I provided him with a full set of toplights and clerestory instructions many months ago. So that excuse isnt valid. 1 Link to post Share on other sites More sharing options...
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