david.hill64 Posted February 19, 2015 Share Posted February 19, 2015 I am in the process of building a 7mm kit of a J36. Neither the smokebox wrapper nor the smokebox front plate have any provision in the etch for embossing the rivet detail. This will not be a problem for the wrapper, which is a flat sheet that I can set up on my GW models rivetting tool, but how do I mark out the locations of the rivets on the front? They clearly follow the circular section of the smokebox at the upper part of the plate and transition in the area of the smokebox saddle. I am thinking about marking them on tracing paper or similar and then using that as a template, but how do I mark out a circular curve of evenly spaced dots? It's at least 45 years since I have done any technical drawing, and if I knew the technique then I don't now! I have access to the full range of Microsoft Office programs, including Visio, so that might present an option. The only comfort I have is that looking at photos the pitch of the rivets is far from even! Thanks David Link to post Share on other sites More sharing options...
JeremyC Posted February 19, 2015 Share Posted February 19, 2015 I assume you're modelling a particular engine at on a particular date? Having just completed a 4mm model of one I can say that J36 smokeboxes are a nightmare (as are D30s)! Some locos have visible rivets, some don't and whether they have them or not can depend on the date. There are also some engines that have the front plate riveted, but not the wrapper etc. Unfortunately photos often aren't very clear. As to working out the spacing if you know the pcd of the rivets you can calculate the circumference, then divide by the number of rivets to get the spacing. If you then mark out the pcd you can then step out the rivets with dividers. Sorry! pcd = pitch circle diameter, the diameter of circle that marks out the centres of a series of bolt/rivets Jeremy Link to post Share on other sites More sharing options...
david.hill64 Posted February 19, 2015 Author Share Posted February 19, 2015 I assume you're modelling a particular engine at on a particular date? Having just completed a 4mm model of one I can say that J36 smokeboxes are a nightmare (as are D30s)! Some locos have visible rivets, some don't and whether they have them or not can depend on the date. There are also some engines that have the front plate riveted, but not the wrapper etc. Unfortunately photos often aren't very clear. As to working out the spacing if you know the pcd of the rivets you can calculate the circumference, then divide by the number of rivets to get the spacing. If you then mark out the pcd you can then step out the rivets with dividers. Jeremy Thank you. The loco is Maude in the late 50's early 60's when she (or should I say he?) does have the rivet detail on both wrapper and front. I think my concerns are 1) making the rivets concentric with the edge of the smokebox and 2) marking them reasonably evenly. That's why I think I will do it on tracing paper and then use that as a template. Link to post Share on other sites More sharing options...
Pebbles Posted February 19, 2015 Share Posted February 19, 2015 My GW came with instructions to produce a circular pitch of rivets. Best ask George. Link to post Share on other sites More sharing options...
david.hill64 Posted February 19, 2015 Author Share Posted February 19, 2015 My GW came with instructions to produce a circular pitch of rivets. Best ask George. Magic thanks! When in doubt read the instructions! Edit to add that I am back in teh apartment and have rooted out the instructions, which certainly help. Looks like I am going to have to do some trigonometry. Link to post Share on other sites More sharing options...
hobbyhorse Posted February 19, 2015 Share Posted February 19, 2015 In the past I've mounted the smokebox on the dividing head, worked out the degrees of the rivets around the circumference and then scribed each position. This can also be done on the lathe using the screw cutting gears, and mounting the marking tool in the tool post. Simon Link to post Share on other sites More sharing options...
david.hill64 Posted February 20, 2015 Author Share Posted February 20, 2015 In the past I've mounted the smokebox on the dividing head, worked out the degrees of the rivets around the circumference and then scribed each position. This can also be done on the lathe using the screw cutting gears, and mounting the marking tool in the tool post. Simon Another reason why I need to invest in some machine tools! Thank you, David Link to post Share on other sites More sharing options...
cobach47 Posted February 20, 2015 Share Posted February 20, 2015 i assume you are using proper rivets get some thin plasticard make a template mark the spacing drill out and wrap it round the smokebox. i have been making rivets on my locos by using thin plasticard and marking the rivets using a blunt needle. this method works well on buffer beams Link to post Share on other sites More sharing options...
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