My R had once been in a Fahlin SF1,I suspect it had been sent back to Pobjoys at Hooton Park for an overhaul.
The power to weight ratio of a 7 cylinder original Pobjoy was incredible and the 'Thrust' with the reduction box well ahead of a basic American flat 4.
In fact the reduction box on a Pobjoy is a work of art in itself, and is built with the precision of a swiss watch.
Once you get over the valve issues, the rather speedy running of the BTH mags was countered by the half speed Rotax version.
Cooling and the basic oil system is not an issue but I suspect the cost of the unit was rather high and the market for 90hp catered for by a manufacturer that also made light aircraft (DH) . With the factory destroyed by bombing and Pobjoy killed in a post war accident there were no more designs from this talented designer.
The Pobjoy was essentially the equivalent of a 'racing' unit with weight (lack of) a major factor. The rotating parts are minimal but strong and 'polished'. The pistons are only just big enough to hold the rings and are both sculptured and polished. The aforementioned reduction drive gives it incredible thrust and is totally reliable. The associated two blade prop looks like a railway sleeper rotating ahead of you. The combination gives the Swift a very nimble performance.
Last edited by POBJOY; 26th Sep 2021 at 19:49.
Reason: content