I was trying to use the drawings in D.A.G. Brown’s book Miniature Injectors Inside and Out, mainly as an Alibre Atom exercise but also to see if if there is an easier way to make the overflow conduit than his method. I’m sure it works for him but I am not convinced it would for me.

I was hampered by the drawings having been reduced to fit the A5 pages, and by the random use of binary fractions among mainly decimals. Also, some parts were not very clear.

Anyway I came back to the exercise over the last few weeks and this evening completed it, for the 8oz/minute size. Mr. Brown uses a common body size for three or four capacities.

One aspect I was prepared to see fail was how I drew the two-part combining-cone. I started it as if solid, then used Revolve Cut to remove the centre section, not knowing if the two parts would stay together across the gap.

They do!

I don’t know if its location along the tube is right. I used an auxiliary plane set from the body’s steam-inlet face to place the downstream face of the combining-cone division, making the division symmetrical with the ball-valve. Though useful as part of a CAD exercise it might not be correct for the real version, in which the penetration of the steam cone in the combining-cone is critical.

Those threads are 1/32″ pitch but not helices, just symbolic parallel ridges.

Is it correct though? Or have I muddled up the original drawings? Is the gap between the combining-cone outlet and delivery-cone inlet usually in thin air? I had to examine one, using the same illuminated magnifier (bought at MMEX last week!) that helped me read the book’s drawings, to establish that is indeed so.

Whether I’ll try making the real thing I don’t know, but it was quite a challenge just to model it in 1s and 0s.