I had a school visit in Harpenden on Wednesday, so took the opportunity to drive on to Peterborough to collect the ABC Vee 4 I bought off E-bay on Tuesday night. It is a bare engine, although complete except for its magnetos (more of which later) but once formed the heart of a "power pod", an encased Auxiliary Power Unit used in Beverley aircraft for charging batteries etc whilst the main engines were not running. According to the loose leaf manual that accompanies it, it was taken out of service in 1958.
ABC engines are not common at the best of times and this Vee4 is the only one that I know of in private hands, although I understand Duxford have one in a more complete state. I've taken some pictures this morning, some of the engine itself and others from the manual, and you can see them atI love these aircraft APU's, the engineering is to the highest standard and the engineering solutions are s-o-o-o elegant.
I'm told that sometime in the last eight years, the previous owner but one removed the BTH magnetos, imagining that they might be used on a motorcycle. I need a brace of clockwise, flange-on-the-base mounted, BTH MC2 magnetos, preferably the S25 model, air ministry spec They are not going to be leaping off every table at Sodbury next weekend, are they? So if anyone has one (or two!), I'd be glad to hear from them. Base mounted magnetos off any flat twin (Petter, Norman, Coventry-Victor) will do fine.
Why does a pair of flat twin mags fit a vee 4? Because there is effectively only one crankpin - there are two separated by a centre main, but they are in line. So the crank throw is 360o, each pair of cylinders being offset in vertical plane, the rods being simply side-by-side on each crankpin. Therefore, if you visualise the engine not as two vee twins (as I did to start with!) but as a four cylinder engine with both pistons in one bank arriving at TDC together, it follows that one must be on the firing stroke and the other on exhaust. So, although it might be some little trouble to find them, at least I'm not looking for a pair of BTH mags with a firing angle of 90o!