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It's called an isometric projection. Three axes at 120 degrees. All measurements show as true length parallel to one of the axes. Easy to handle on the drawing board for a scale representation in 3-D.Parallel lines stay parallel rather than converging at a horizon, but an always be measured. Not like a perspective drawing. Distant parts appear to be over size as we normally see with a perspective view where parallel lines converge at the horizon. As Pete says, it tends to look a little strange until you are used to it, but it is useful when it is desirable to show at scale rather than just an artistic presentation. Obviously both have their places.I always enjoy looking in on the inspiring work on this model, thank you Chris for your trouble in writing it up so well for us all to follow and enjoy.MJM460Thanks for the info I did wonder if it was isometric ,perspective ,trompe d'lol or just good old "should have gone to specksavers" and i have now cancelled my appointment to Specksavers !!! Its a good job that cad doesn't work to Pespective although it might introduce some extra realism to our models !!
Chris--I have always been faintly interested in Stephenson reversing links. Not enough to really pay close attention to them.--Just enough to think, "Gee, that's rather neat." After seeing the ones in your 3d model, I went on an "in depth search" about them and even downloaded a 3d model from "Grabcad" to follow the workings a little more closely. Very interesting mechanism.---Brian
Quote from: 90LX_Notch on March 21, 2017, 08:07:22 PMChris-An ironic thread about machining the bevel gears for a Lombard restoration over at PM:http://www.practicalmachinist.com/vb/general/machining-bevel-gears-332469/?s=982f369009d6d1f6aa251517a2b5c5fd-BobSounds like as much confusion on making model ones as full size ones! They got all wrapped around the pole confusing straight form and gleason form teeth.
Chris-An ironic thread about machining the bevel gears for a Lombard restoration over at PM:http://www.practicalmachinist.com/vb/general/machining-bevel-gears-332469/?s=982f369009d6d1f6aa251517a2b5c5fd-Bob
In looking at your model, I am wondering how motion of the eccentric straps get transmitted to the levers with the valve rod. Certainly an interesting setup.
Your a man after my own heart!!---If the part doesn't match the plan, then change the plan to match the part. Only those people who design in 3d cad and then build the parts they designed know how often that happens!!!
Quote from: Brian Rupnow on March 22, 2017, 08:48:29 PMYour a man after my own heart!!---If the part doesn't match the plan, then change the plan to match the part. Only those people who design in 3d cad and then build the parts they designed know how often that happens!!!Isn't that why they invented shims and sandpaper?!
I bet you were glad to get back to cutting metal. I like the clever use of the lathe tool to register where the gear needed to go on the shaft. Filed that one away. Jim
Hi Chris,Referring back to your comment on the rocker arm connection to the valve rods, this is similar to the monitor engines on another thread. It has a short vertical slot instead of a close fitting hole in the rod end connector to allow for the vertical part of the rocker arm motion. It would be pretty difficult to see this in looking at the original. While it does not seem ideal due to the vertical friction force which will still tend give a little side load to the packing, it would be much better than trying to bend the valve rod as it passes through the packing. In any case it will be a wearing part and I would suggest some care in making the rod end and the pin easily replaceable. I would also suggest making a spare set of pins and rod ends as part of your two years spares kit. (You did order two years spares with this machine, didn't you?). Some sort of rod guide and Conrod type connection would seem better, but not true to original, and clearly one of the necessary compromises in fitting everything in on the original. It is also a machine that would probably flex enough on rough conditions to offset any advantage in the extra complexity.MJM460