In Westbury's book 'Model Petrol Engines' is the description of a valveless reciprocating oil pump described as suitable for engines up to 30cc. Has anyone made one or an engine that uses one?
The drive is from a worm on the engine shaft coupled to a pinion on the pump shaft that reciprocates with the plunger. As the pinion moves axially it obviously cannot be a 'proper' worm wheel. I have found a commercial 0.5 MOD pinion that is long enough to allow for the plunger movement. My lathe clains to have a screw cutting setting for 0.5 MOD. I think that I should be able to cut a worm that will work with this pinion but am unsure on a couple of points (I could just try it and see what happens but I always like to ask first
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1) What sort of thread profile should I use?
2) The thread on the worm will have a pitch angle. Should I angle the pump pinion and pump shaft to match?
3) As it will be very lightly loaded do 1) and 2) really matter.
I think that Jo's Kiwi or Kitti used a screw thread based worm drive for an oscillating oil pump but I can't currently find the details.