Post by buttybach1932 on Feb 2, 2024 21:45:46 GMT
Hi Norton John
Further to your comment about automatic lubrication systems on two strokes. Most early two strokes used either a gravity drip feed or a small drip feed pump driven off the engine. The same or very similar pumps were used on early four stroke engines. Most early two strokes had bronze bush main bearings that also acted as crankcase seals and some had a bronze bush big end bearing so they needed a decent supply of clean oil.
Velocette introduced their first two stoke engine in 1913 and it was fitted with a mechanical oil pump. The engine was an overhung crankshaft design with a single long plain main bearing and a plain big end. The oil compartment formed part of the crankcase and the pump was submerged in the oil compartment. Oil was pumped along the plain main bearing then centrifuged out to feed the plain big end. The cast iron piston and cylinder bore were lubricated by splash. The oil pump output could be adjusted via a knurled knob on the top of the crankcase that adjusted the stroke of the oil pump.
The problem with the Velocette system was cost, so they came up with a cheaper system for their economy models. There was no pump and the oil was sucked into the engine via timed ports in the plain main bearing. The oil quantity could be regulated by a needle valve via either a lever or a knurled knob on the top of the crankcase.
The de-luxe versions of the overhung crankshaft two strokes continued to use an oil pump.
For 1930 Velocette introduced a completely new two stroke design the GTP. This had a conventional crankshaft but still had bronze main bearings. The big end bearing was a crowded roller design. The oil pump was located in a separate compartment of the crankcase and was driven off the end of the crankshaft via a worm gear at 1/50th engine speed. The oil was located in a small tank within the fuel tank. Up to 1932 the oil pump output was adjusted via a knurled knob. On later machines the oil pump was linked to the throttle via a bent spoke connected to an arm lifted by the throttle slide.
The only petrol / oil lubricated two stroke engine that Velocette manufactured was the 1960-64 250cc flat twin Viceroy scooter engine.
Regards
Butty Bach
Further to your comment about automatic lubrication systems on two strokes. Most early two strokes used either a gravity drip feed or a small drip feed pump driven off the engine. The same or very similar pumps were used on early four stroke engines. Most early two strokes had bronze bush main bearings that also acted as crankcase seals and some had a bronze bush big end bearing so they needed a decent supply of clean oil.
Velocette introduced their first two stoke engine in 1913 and it was fitted with a mechanical oil pump. The engine was an overhung crankshaft design with a single long plain main bearing and a plain big end. The oil compartment formed part of the crankcase and the pump was submerged in the oil compartment. Oil was pumped along the plain main bearing then centrifuged out to feed the plain big end. The cast iron piston and cylinder bore were lubricated by splash. The oil pump output could be adjusted via a knurled knob on the top of the crankcase that adjusted the stroke of the oil pump.
The problem with the Velocette system was cost, so they came up with a cheaper system for their economy models. There was no pump and the oil was sucked into the engine via timed ports in the plain main bearing. The oil quantity could be regulated by a needle valve via either a lever or a knurled knob on the top of the crankcase.
The de-luxe versions of the overhung crankshaft two strokes continued to use an oil pump.
For 1930 Velocette introduced a completely new two stroke design the GTP. This had a conventional crankshaft but still had bronze main bearings. The big end bearing was a crowded roller design. The oil pump was located in a separate compartment of the crankcase and was driven off the end of the crankshaft via a worm gear at 1/50th engine speed. The oil was located in a small tank within the fuel tank. Up to 1932 the oil pump output was adjusted via a knurled knob. On later machines the oil pump was linked to the throttle via a bent spoke connected to an arm lifted by the throttle slide.
The only petrol / oil lubricated two stroke engine that Velocette manufactured was the 1960-64 250cc flat twin Viceroy scooter engine.
Regards
Butty Bach
