Can anyone shed any light on this mystery oil pump for an OHV Douglas racing engine? I think it belongs to 1928-31 time period, but I have not yet seem a picture of Douglas exhibiting such a pump setup-
It was used in conjunction with engines that had a large rectangular opening in the bottom of the crankcase; specifically the TT models that had a re-circulating oil system. Here is an example of such a crankcase-
First such was use on the 1925 factory TT machines, and the following year's catalog 26TT models. However that oil pump looked like this-
The gear pump is attached to the side of the sump, and it is a funnel that bolts to the opening in the crankcase. This leads the oil over to the side of the frame, and down into the top of the oil pump; the upper chamber containing the scavenge gears. These serve only to pump the oil to the front compartment of the sump where it drains through a gauze filter to the main compartment. For how long this setup was used is not known.
Forward to 1930, and a new shorter sump appeared on the racing models, heavily finned. The crankcase drained directly into the sump; which was a good idea in itself. However it had a built in design flaw in that every time you slackened the mounting bolts to slide the engine fore and aft to adjust the primary chain (the transmission mounting was fixed) you broke the sump gasket seal so encouraging leaks. Be that as it may, the pump still bolted to the side of the sump, but was much smaller and only required a pressure stage. They seemed to use this till there last serious effort in 1933. It looked thus-
This mystery pump does mate up to the "standard" rectangular opening as seen here-
But it does not seem that it is required to work in conjunction with a sump below the engine. Indeed the oil reservoir could be anywhere. If a sump were intended, they most likely would have continued the practice of mounting the pump onto the side of the sump. So a racing OHV engine with re-circulating oil, but no sump. There is also the possibility that it was made much later by a skilled privateer. The quality of the aluminum casting is quite high (though battered about on the 'leading edge'), higher actually that what one usually sees with pre-war Dougie bits! The foundry was very good with cast iron, but they did seem to struggle at times with aluminum.
Any ideas, pictures, period articles would be much appreciated.
-Doug
