The Revetec Design
The REVETEC Engine design consists of two counter-rotating “Trilobate” cams (1&2) geared together, so both cams contribute to forward motion. Two bearings (3&4) run along the profile of both cams (four bearings in all) and stay in contact with the cams at all times. The bearings are mounted on the underside of the two inter-connected pistons (5a&5b), which maintain the desired bearing to Trilobe clearance throughout the stroke.
The two cams rotate and raise the piston with a scissor-like action to the bearings. Before the top of the stroke the air/fuel mixture is fired, just like a conventional engine. The expanded gas then forces the bearings down the ramps of the cams spreading them apart ending the stroke.
The piston assembly slides rigidly through the block via an oil pressure fed guiding system (6a&6b) eliminating piston to cylinder-bore contact. This reduces wear and lubrication requirements in the cylinder, and also reduces piston side shock making ceramic technology suitable.
The counter rotation is performed by a reverse gear set (7a&7b - Other gears not shown) at a 1:3 ratio shaft providing two strokes of the piston, to 360 degrees of output shaft (8) rotation.
This is the same as a conventional engine.
The mechanical advantage or torque lever is increased around 20-80deg ATDC making the most of the high cylinder pressure. This compares to a conventional engine that reaches maximum mechanical advantage around 40-90deg ATDC.
The effective cranking distance is determined by the length from the point of bearing contact to the centre of the output shaft (not the stroke). A conventional engine's turning distance is half of the piston stroke. The piston acceleration throughout the stroke is controlled by the trilobe cam “grind” which can be altered to suit a wide variety of fuels, torque requirements and/or rev range.
One module can either comprise of two trilobate cams and either two, or four pistons in an “X” configuration.
Reducing Mechanical Losses
A Conventional engine produces a side thrust on the piston which is controlled by the piston skirt (Refer 1 below). This side thrust is a result of the piston applying pressure on the crank via a connecting rod which is applying that force at an angle to the crankshaft. The resulting angle also produces a great down-ward loading on the crankshaft (Refer 2 below). This downward force is a great mechanical loss which reduces engine efficiency. The total mechanical losses in this area of a conventional engine are approximately 36%.
The mechanical losses are reduced in the CCE design by deflecting the side thrust that is produced from the bearing to Trilobe cam angle of attack (Refer 3 below) into the counter-rotating cam. This deflected force increases the torque lever, further increasing overall torque application. Downward thrust on the output shaft is reduced to a minimum resulting in total mechanical losses of approximately 12% compared to 36% of a conventional engine.
Main Features of Technology
Increased Torque Lever
Below is just one example of the increase in torque lever. The Revetec design allows the easy customisation of this torque lever. Trilobe shape is almost infinitely variable, so customisation of engine characteristics are also as variable.
Rather than waste deflected forces which create friction and mechanical losses, the Revetec engine deflects these forces into useable torque. (1) Wasted force from piston side thrust. (2) Wasted down force on crankshaft main bearing. (3) Deflected side thrust into usable torque (shown in blue). (4) Reduced waste down force.
Increased Piston Dwell
By using Asymmetrical Trilobes, extended piston dwell can be achieved. It is well known that piston dwell creates better combustion efficiency. Normally a downside is poor early mechanical transfer, so this is normally associated with high RPM engines. Revetec engines extend the dwell on the compression side of the stroke (Not the power side) which increases dwell, maintains good torque lever and raises the piston position at ignition.
This provides an increase in fuel particle density allowing leaner mixtures to be used and lowering the chance of detonation. By decreasing the chance of detonation, a higher compression ratio can also be used.
With a higher piston position at ignition and burn, less heat energy is absorbed into the cylinder due to decreased cylinder wall exposure. This also increases engine total efficiency.