Engines > From Plans
JC attempts the MEM Corliss
derekwarner:
JC...thinking that you have 4 of the linkage adjustments to achieve......
I have zero knowledge in the installation of Corliss valving, so does the geometric orientation provide correct timing?, or does each of the 4 valve spools require any +/- positioning?
If you used the same bolt pitch [0.3P] as the M1.4 diameter bolts as the linkage rod, would 0.3P [x .5= 0.015mm per 180 degrees] allow sufficient alignment?....or would you have slip fit & solder both ends of the connecting rod to ensure absolute accuracy in the timing of the arm?
Derek
JCvdW:
Derek, I would think that if all components are accurate, that geometric orientation should provide correct timing. But I expect that in my case I will have to make small adjustments.
On real Corliss valves, the linkages are adjustable, and your suggestion makes for a more realistic model. In fact, this is also how it is shown on the plans. But making adjustable linkages seems really difficult. Hence the attempt to make adjustable valve levers instead.
I started off the adjustable levers by squaring off two pieces of 303 stainless steel.
The ears were milled, drilled and then rounded off on the rotary table. The four yaw chuck on the rotary table allows for easy adjustment of the pivot point.
The M3 holes for the valve stems and the M2 threaded holes for the connecting rods were then drilled and tapped, and rounded on the rotary table.
The 0.5mm slots for the ears were then cut on the lathe. The lever was clamped in a tool holder, with the slitting saw in the four yaw chuck. This way the saw could be accurately centred using the lathe DRO.
The angled sides were then set and milled on the rotary table.
The levers were then separated and the connecting rod side also rounded on the rotary table.
The final result is not perfect, but will do for now. Next time I will rather use the M3 hole as reference point for all operations, rather than the end of the ears.
Only the connecting rods now, and then the engine should hopefully move under its own steam!
Kim:
Very nice work, JC! :popcorn:
I found it interesting how you used the slitting saw and held the part in the tool rest on your lathe. I've never seen that done before. Pretty interesting!
Kim
JCvdW:
Thanks Kim for the feedback. Probably a bit of fools rush in where angels fear to tread...
The disk arms were made from 6mm brass rod. First the one end of each work piece was centre drilled.
The rod was then held in the vice with a square ER25 collet block. The other end of the rod was supported by a 60 deg pointed tip in the vice stop. The 2mm holes were then drilled, and the arm milled down to a thickness of 2.25 mm.
The arms were then moved to the lathe. 2mm drills in the holes were used to locate the centre of the arm with the DRO. A HSS bit with a 60 deg point was ground for turning.
The end of the arm is supported by a live centre in the tail stock.
All four arms turned, and the ends parted off with a slitting saw, ready for the ends to be rounded on the rotary table:
The arm was bolted to a piece of sacrificial aluminium and held in the four yaw chuck on the rotary table to round the ends with a 2mm end mill.
All four arms completed, ready for assembly.
I am contemplating using 2mm screws to connect the arms to the valve disk and levers, and to fill the section of thread inside the arms with epoxy. The epoxy will then be turned to form a 2mm rod to prevent unnecessary wear of the brass arms.
Will have to find a supply of compressed air somewhere...
Olli-Matti:
Well done JC, arms look sharp. How do you center your mill to the rotary table for rounding off? I always find that hard to do and that shows so easily in the part being made..
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