Swashplate oil pump

[dave bushell]

Does anyone know whether the swashplate oil pump used a twin pull throttle or a splitter box on the throttle cable?
Dave

[BRIAN MARSHALL]

Hello Dave,
I currently have one and three-quarter swashplate oil pumps here. They are not mine, but I hope to acquire one of them for my next project, a sort of 1934 semi-Grand Prix/Flyer. About 25 years ago ( ? ), I did own another one, and that came complete with control cable and a little chrome-plated splitter box, but I have no idea if that was original. I think that we have to ask the question “What bikes had twin carburettors, needing a twin-pull twistgrip, in the early 1930’s?” I can’t think of any, except for a handful of Brough Superiors fitted with the “Two of Everything” JAP engine; two carbs, two magnetos, and two Pilgrim oil pumps. I can’t recall seeing one with a twin-pull twistgrip, and so they might not even have existed at the time, and so a splitter gizmo would be essential.
Brian

[BRIAN MARSHALL]

Incidentally, there are three different versions of the swashplate oil pump, one with a very heavy bronze manifold on the back, and then one with a magnesium manifold, presumably intended for the racing fraternity, and then the one with the much bigger diameter built-in crankcase door, intended only for the pukka Grand Prix engines. The trouble with magnesium is that it can suffer from intense corrosion once the passivated outer skin gets damaged. That is why magnesium crankcases, like on the AJS 7R and Matchless G50 racers, have a gold-coloured coating for protection.
Brian

[dave bushell]

Hi Brian
My pump has an aluminium crankcase door and fits the rep engine crankcase.
Dave

[BRIAN MARSHALL]

Hello Dave, I THINK that they all had alloy bodies and door sections. By “manifold” I mean the bit on the back where all the oil distribution pipes attach.
Every one that I have seen has got ‘SMC Co Ltd’ on the outer casing, but upside down ! Also if you remove the bezel from the dial, you should find a serial number, scratched by hand, on the face of the dial. You might even be able to see it without removing the bezel and the face, but most of the celluloid faces have gone very yellow by now.
Brian

[dave bushell]

Hi Brian
Checking my pumps, they both have magnesium manifolds, at least I presume that they must be magnesium, they are both dark grey in colour and certainly not bronze. As for serial numbers, one is visible through the celluloid but not very legible and it could be difficult to remove the bezel as it appears to have been well Hermitited on! The other pump is unreadable due to lens discolouration. Both have different numbers stamped on the alloy bodies (not the manifolds). One is 5P [] 1030, the other 5P [] 1059. One manifold has c3w stamped on the inside face, the other has nothing. Both have SMC Co Ltd upside down on the outer covers!
Dave

[scott596]

Hi David I can confirm that the chrome type splitter box was available about 1933 as a while ago I bought a pair of Bowden carburettors from an Excelsior mechanical marvel these had two pairs of cables and two splitter boxes, one pair to the twistgrip and one pair to the choke lever. What you have be carefull of is to make sure that the splitter box has enough free length inside to allow your carburettor to open fully, the other problem to consider is that the cable movement required to open the carb fully may not be the same as is required by the pump, so an adjustable arm might be needed on the pump or a tension spring between the cable and the pump if the pump needs to be fully open at 3/4 throttle, best of luck, Alan Noakes.

[dave bushell]

Thanks, Alan
Dave

[BRIAN MARSHALL]

Hi,
The two swashplate pumps in my workshop are numbered 5P2 No1010 and 5P2 No1095, and Colin Heath’s is 5P2 No1027. I think that they probably started at number 1000. The numerals 2 are both in Roman numerals, but I don’t know how to type in Roman numerals on my laptop ! Seems a bit quirky/archaic…
Scratched onto the dial on both of the ones here is 35848/32, and both have the magnesium type manifold . Presumably the number scratched onto both dials means something, but I haven’t a clue unless it is a part number, with the last two numbers standing for 1932 ?
Brian

[dave bushell]

I couldn’t do Roman numerals either, so I used “open and closed” brackets instead!
Dave

[Author]

Posts