Russell's Bourke 30 Explained In Simple Terms
Care of Hot Rod Magazine, 1954.
Excerpted from the authentic original Bourke Engine Documentary, pages 111 thru 114, sold by Bourke-Engine.Com
Original author of this article, George Hill, calls the Bourke engine a 2-stroke. It is not a 2-stroke engine.
It is a 1 stroke engine taking care of all 4 cycles in one stroke 2 times per revolution!
Edited and reformatted for clarity and content by David Wolfe, Founder, Bourke-Engine.Com.
Free to copy, share and distribute as long as you refer to www.Bourke-Engine.Com as the originator and give credit to Russell Bourke and the editor.
Also, check out www.projectbourke.com for lots of current pictures and video clips on this remarkable little powerhouse! Updated regularly!
The crankcase is a precision machined aluminum casting with two face- plates (in which the crank bearings are contained) that is completely sealed off from the cylinders when the engine is buttoned up. No gaskets are needed or used, only o-rings.. No oil filter is needed and Bourke claims that the crankcase oil is good for the life of the engine. The level must be kept up, however, to compensate for any possible leakage and ring usage. As the case is sealed off from the cylinders, and consequently the products of combustion, the oil is free of contamination. Being devoid of any potential lubrication failures, the engine can be run up to top rpm under full load on a cold start. One test engine has run over 1100 hours at between 1,000 and 10,000 rpm with no sign of wear on either of the moving parts and the oil looks as good as new.
Cast of Alcoa 365 heat treated aluminum alloy, as are all the other aluminum castings, the two cylinder block contains many odd features.
At first glance, the inside walls of the cylinders appear to be full of holes. These are the ports for intake and exhaust and their arrangement is one of the reasons why the engine is so successful. They replace, in effect, the operation of valves, cams and all the other breathing mechanisms upon which the conventional four stroke engine is so dependent.
THE LUBRICATION SYSTEM
Both parts in the crankcase are bathed in oil. Oil is supplied between the two rings at the bottom of the stroke from a small hole in the cylinder wall. Oil reaches this opening via matching rifle drilled holes in both the cylinder block and the upper part of the crankcase. Pressure to drive the oil through this passage is in reality the centrifugal force of the oil as it leaves the whirling crankshaft and flies into the opening. As long as pistons and rings are well supplied with oil, no more oil feeds, but as oil is lost from the rings it is replaced by fresh oil, making lubrication automatic, economical and dependable.
THE BOURKE CYCLE
Now let's follow the piston-rod assembly through one crank revolution:
As the crank bearing rolls across the connecting rod shoe in the yoke assembly, the piston dwells at the top of its stroke for a measurable amount of crank travel, approximately 45 degrees, holding the burning gases until they are completely consumed, no further flame, and the maximum pressure has developed.
Just prior to that as the piston traveled upward toward tdc, the intake ports were opened by the piston skirt and the area between the piston and crankcase facing (approximately 30 cubic inches) had filled with an air / fuel mixture under a vacuum created by the pistons upward travel.
Pressure is generated at the top of the piston forcing it inward as soon as the crankpin reaches a point of mechanical advantage.
Moving inward, the piston transmits all energy to the crankshaft through the yoke assembly and the skirt closes the intake port and bottom transfer port so that the air / fuel mixture underneath the piston is compressed against the crankcase facing surface. The piston skirt drops deep into a recess that is machined into the crankcase facing, thus allowing compression of the air / fuel charge to a pressure of approximately 50 psi.
As the piston dwells at the end of its inward travel (for another 45 degrees of crankshaft rotation), a port in the piston skirt is alighted with a port in the cylinder wall. The air / fuel mixture (now under pressure), is allowed to escape into the transfer jacket outside the cylinder wall and enter the cylinder again through the port above the piston via the same transfer jacket. A turbulating fin and the surface design angle on the piston join in directing the air / fuel mixture in a swirling motion to the top of the cylinder.
As the pressure charge continues it's expansion, it moves down into the cylinder and forces the spent gasses through the now open exhaust port that is above the intake port on the same side of the cylinder wall.
At this time, the opposite piston is receiving it's power impulse and is ready to start inward, closing the transfer and exhaust ports on opposite sides of each other and compressing its fresh air / fuel charge as it moves upward.
The upward motion of the same piston also creates a vacuum beneath the piston to draw in the new air / fuel mixture (only air if injectors are being used), for it's next cycle as its skirt uncovers the intake port.
At about 90 degrees before top dead center, ignition occurs as compression continues.
As compression continues and pressure increases, the air / fuel mixture burns more rapidly and a force or cushion is built up sufficient to stop the movement of the mass (pistons and rod assembly) and as the crankshaft throw moves across top dead center, the burning charge is completely consumed and the pressure is released to send the piston back inward, so ending the second 180 degrees of crankshaft travel.
Since the same action takes place at each end of the mass (piston-rod-yoke assembly) and since the forces generated are equal, the moving mass can be likened to a tennis ball being batted back and forth by players of equal strength. As the mass is not tied solidly to the crankshaft, it simply imparts its energy to it in passing. Therefore no energy is absorbed from the crankshaft to complete the cycle.
An electronic copy of the original and authentic Bourke Engine Documentary, by Lois Bourke can be obtained here. Contains tons more information, pictures, theories and basis for Russell Bourke's designs and discoveries regarding his remarkable engine!
Return to the home page of www.projectbourke.com