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So I think I can make the 60/30 pulleys work if I make the end crank diameter .375, once I bore the id some. So to attach the lower pulley I could just machine a flat in the crank and have a setscrew in the pulley like in the pic?Also tensioning the belt is a little tricky because it has to go around the water pump passages in the front cover. I'm thinking one idler at the inspection cover in the head and a tensioner closer to the crank?
Quote from: theeoracle on February 12, 2019, 04:48:02 PMSo I think I can make the 60/30 pulleys work if I make the end crank diameter .375, once I bore the id some. So to attach the lower pulley I could just machine a flat in the crank and have a setscrew in the pulley like in the pic?Also tensioning the belt is a little tricky because it has to go around the water pump passages in the front cover. I'm thinking one idler at the inspection cover in the head and a tensioner closer to the crank? The hub dia. of a 30T cog is about .550in. You will be catching about 4 threads of a #6 set screw with a .375 in. overbore. Dual setscrews with a flat seat on the crank "may" be enough. A solution to inadequate hub diameter is to make a collar to press fit / epoxy around the existing hub and re drill for a longer setscrew and more thread area. You can pre- drill the collar to line up with the hub setscrew holes and drill the next thread size up.Your water pump box is an issue working a belt around by idlers. You would need to be dead nuts on the belt tooth count too. What I would think about, looking at your photo, is eliminate the water pump box section under the cam drive cog for an external cam drive set-up with idlers on engine mounted brackets to give you more lead way as well as a sprocket guard bolted to the engine or as part of the valve cover.
I think I might even be able to use a 42/21 pulley if I bore the 21 pulley out to .375. That leaves .047" of wall thickness, I think that will be enough, what do you think?
If you are determined to an authentic recreation, then that decision is made for you! Which Nissan engine are you modeling and how did they drive the cam?
Quote from: theeoracle on February 12, 2019, 06:19:23 PMI think I might even be able to use a 42/21 pulley if I bore the 21 pulley out to .375. That leaves .047" of wall thickness, I think that will be enough, what do you think?If the wall thickness refers to the cog hub on the crankshaft....you are now down to less than two threads.
They look great Let me guess - you have access to a nice CNC mill ... - don't get me wrong, as this still requires creating a good tool path in order to avoid some not very nice mishaps (if you haven't got a clue about those, you don't know CNC yet ).
I'm making an L16, used in a bunch of different Datsuns from pretty much 68-79...............
Lubrication is always a good question and not always an easy one to answer as there are several factors involved.The size of the workload is one of the biggest factors, so let's start here. :How big is the engine - bore, stroke and compression (the last can usually be answered with the CAD program you're using) ?How big will the load be ? - RPM ?What kind of fuel will you be using ?Cylinders / pistons can usually get plenty of oil from the fuel with 1-2% oil in it and splash lubrication is in most cases plenty in this area. Con rods again, can often get away with plash lubrication and all ball bearing are very happy with an oil mist (actually preferred). Camshafts and crankshaft bearings vary, as plain bearing often require pressure to work, but that is again VERY load dependent. The cams themselves are happy with splash lube.OS model latest FS series four-stroke aero engines are only lubricated from a bit of oil in the fuel and a genially simple system of channels that uses the unavoidable higher pressure in the crankcase + the fact that some of the oil in the fuel ends up there, to move that oil through the crank bearings to the camshaft. From there it goes through the pushrod tubes to the cylinder head where it lubes the valves etc. and goes back to the inlet through a very small hole, get sucked back in and the hole thing repeats
That amount of CC's is enough to warrant pressure oiling of the mains if it is loaded for sure or sustained runs …. but Roger might be right about just a plash in all the right places before a run - I hope some of the builders of bigger 4, 6 & 8 cylinder engines here will chime in, though I'm sure that they all have presure oiling. This should be possible in an engine of this size and to an extent required for a scale model.The next part of your question - yes all oil lines / galleries have a certain internal diameter and a much smaller outlet at each oiling point in order to keep the presure in the system + make sure all places get what they need. On full size engines you will often find jets like the ones in an old carb in the oil lines (except that you can't change them). The jets over the cams create a spray pattern as it both cools and lubes better than a constant flow of oil there - in performance engines.
You "only" need to drill a small hole from the main bearing to the throw in the crank in order to lube the big-end of the con-rod as the small end never is pressure lubricated.There are several engines here on site where you can see it done with pictures and accompanying text.George Britnell comes to mind as one of the masters here, but he is absolutely not the only one - have a look under Engines - your own design.