Close tolerance crankshaft oil scraper
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The invention allows the well-known class of crankcase oil windage control devices known as “crank scrapers” to achieve greater efficiency. The efficiency of a scraper is inversely related to the clearance present with moving parts sweeping past it. Typically constructed of metal, scrapers have had recommended running clearances of 0.035″ to 0.060″ for many decades. By using a material in the scraper than can safely contact the moving parts this clearance can be reduced to zero. Many versions of this new class of device built by the inventor have been tested and are in successful use worldwide in passenger car and racing engines.

Johnson, Kevin Liddell (New Port Richey, FL, US)
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International Classes:
F01M1/02; F01M9/10
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Primary Examiner:
Attorney, Agent or Firm:
Kevin, Liddell Johnson (9330 Lakeview Drive, New Port Richey, FL, 34654, US)
1. A “Close Tolerance Crankshaft Oil Scraper” is a well-defined class of device that can directly and safely contact moving parts to physically remove crankcase windage oil in engines. Members of this class comprising: 1. a structure to securely locate the device with respect to the moving parts and 2. a material that can contact and not harm the moving parts.



60/628,700 Provisional application filed on Nov. 18, 2004

Background of the Invention

A so-called “crank scraper” or “oil wiper” is a device that strips adhering oil from the rotating bottom-end assembly and/or from the windage cloud that forms around these components in many internal combustion engines with both wet and dry sumps. At higher rpms the rotational and reciprocal movements of the bottom end create a pressure differential that entrains oil in a so-called “windage cloud.” The proximity and extension of the scraper into this pressure differential helps to disrupt it and thereby allow entrained oil to be expelled from it. These various oil adhesion and windage effects are well-known to professional automotive engineers and can result in surprising parasitic losses of power output and friction and in severe cases even lead to oil foaming and engine failure. These effects are very often counter-intuitive since they involve increased friction and heat generation from the presence of the very oil used to otherwise both lubricate and cool the same area. Also, many people remember pure splash lubricated automobile engines of essentially pre-World War II design and needlessly worry about insufficient oil being thrown about the interior of the crankcase. These typically low rpm engines are quite different from the modern positive pressure lubricated hi-speed motors.

The bottom-end assembly of these modem designs consists of the crankshaft and attached connecting rods with pistons. Adhered oil and/or a windage cloud can result from: the reservoir oil splashing onto the spinning bottom-end; the ejected oil from the pressurized main and rod bearings; the oil directed from cooling or lubricating jets or squirters at the undersides of pistons or cylinder walls; the draining of oil from other components through the crankcase. Loosely defined, crank scraper technology has existed for at least 40 years in OEM passenger car engines (the mid 1960s Pontiac GTO 389 V8 engine had a reverse louver incorporated into its windage tray and the early 1960s Ford FE engines had a relieved plate extending upwards from the floor of the oil pan that allowed the rotating assembly to sweep through it). The term “scraper” is actually something of a misnomer since the “scraper” never actually contacted the component because of the damage that would result from metal to metal contact.

It is useful at this point to differentiate between a windage tray, crank scraper and oil pan baffle since these are often confused. A windage tray is primarily intended to inhibit the splashing of the sump reservoir oil onto the spinning bottom-end whereas a crank scraper is intended to strip away adhered or windage-cloud entrained oil from the bottom-end. A baffle is intended to help ensure that reservoir oil remains around the oil pump pickup. Often these components are combined such as when a windage tray has crank scraper type louvers or edges.

A crank scraper is most efficient when it has the minimum possible running clearance from the rotating assembly. The running clearance is typically a value ranging from 0.035″ to 0.060″ or more. Some engine builders will reduce these values down to as little as 0.010″ if they dare. Since the typical crank scraper is constructed of metal, direct contact with it and subsequent parts damage is carefully avoided through a fitting process. Besides allowing for normal wear and bearing tolerances the clearances are needed because engine components flex and shift slightly, especially during high speed or high output operation.


As mentioned, the Pontiac 389 had reversed louvers in its windage tray which wrapped around the crank and the Ford FE had a plate extending upwards from the floor of the oil pan. The Pontiac style of scraper technology continues to this day with engines such as the BMW M52 and the Ford style can be seen in the oil pans of engines such as the Porsche 2.5 (in the 944 series). Many other scraper styles exist and use single or multiple blades/louvers arrayed along the central axis of the crankshaft sometimes being attached to the oil pan directly and sometimes being attached to a windage tray or other component. The modern Ford 4.6 modular V8 engine uses several such devices arrayed around the bottom-end. After-market oil pan manufacturers such as Milodon and Canton sometimes attach long metal strips along the sides of their pans to act as scrapers. Many common designs bolt in between the oil pan and block (see example drawings) or bolt along the main bearing caps. Normally the optimal placement of a scraper is in the 180-270 degree quadrant of engine rotation as measured from top dead center (TDC) as 0 degrees in a clockwise rotation engine. This allows removed oil to drain directly down into the oil pan reservoir or into the scavenge ports in the case of a dry sump equipped engine.

The idea of using an appropriate material to safely remove excess oil while in contact with the moving surface that oil adheres to is certainly not a new one. For example, Teflon and polymer valve stem seals have been in successful use for decades in automobile engines. However, it has heretofore simply never occurred to anyone to transfer this successful technology to the area of crankcase windage control. Teflon is a registered trademark of DuPont for PTFE polymers; the general use of this trademark in this application in no way implies that other brands of PTFE polymers are any less suitable per se.


An improved class of device that can directly and safely contact moving parts to physically remove

crankcase windage oil in engines, comprising:

1. a structure to securely locate the device with respect to the moving parts and

2. a material that can contact and not harm the moving parts.


Drawing 1 depicts a steel frame with a polymer (for example, Teflon) insert for a Suzuki G10 engine. The assembled scraper bolts under the main bearing cap bolts.

Drawing 2 depicts a steel frame with a polymer (for example, Teflon) insert for a Toyota 4AGE engine. The assembled scraper is held in place between the block and oil pan.

Drawing 3 depicts a series of steel frames and polymer (for example, Teflon) inserts for a Ford Zetec engine. This system is designed to bolt under the main bearing cap bolts and be contained within the confines of the stock windage tray typically found in the engines.

Drawing 4 depicts a steel frame with a polymer (for example, Teflon) insert for an AMC 401 engine. The assembled scraper is held in place between the block and oil pan. The spacer is provided for the opposing oil pan rail so that the oil pan is displaced evenly.

Drawing 5 depicts an idealized windage tray often found in OEM and aftermarket oil pans. A typical feature of such trays is a louver that acts as a scoop to strip out oil from the windage cloud. The drawing shows how a polymer (for example, Teflon) insert can be incorporated into this system, again using a steel clamping plate to retain it securely.

Drawing 6 depicts one aftermarket style of combination windage tray and scraper. The illustration shows how a polymer (for example, Teflon) insert could be incorporated into this style of device.

Drawing 7 depicts a popular style of aftermarket oil pan with a scraper bar attached to the interior wall. The diagram illustrates how a polymer (for example, Teflon) insert could be incorporated with this style of device.

Drawing 8 depicts an end view of a crankshaft in clockwise motion. As parts of the assembly sweep past the Teflon scraper blade it can be seen how the scraper physically strips away an oil film that may be present. Normal metal scrapers need far more clearance to operate safely. With the Teflon insert the blade can actually be in safe contact with the rotating crankshaft.


Prototypes of one example of the “Close Tolerance Crankshaft Oil Scraper” have been constructed and successfully tested in operating wet sump automobile engines. In one case, a stock 993cc engine returned an average of 3% more hp despite already being equipped with a full windage tray. Horsepower increased from approximately 2750 rpm through to the 5300 rpm maximum for the camshaft used. This example used a mounting substructure of 12 gauge steel that attached to the main bearing caps. A blade or trimmed piece of ⅛″ thick Teflon sheet was clamped into place by another carefully cut piece of 12 gauge steel. The clamp was retained by multiple small studs with locknuts. Teflon is an ideal material for such use because of its low friction characteristics and good stability in a hot and oily environment. The scraper can be initially fitted to be in direct contact with the parts that sweep past it during each revolution of the rotating assembly. During operation the Teflon deforms and sacrificially abrades at these points of contact ultimately yielding an optimized pattern for each individual engine. Many of the attached drawings illustrates how this particular material could be used to modify existing crank scraper designs so that they could safely operate while in direct contact with the moving parts. One added benefit of this particular design example is that it acts as a natural frequency damper which can be helpful in some engines. It should not be construed that this example, particularly the use of a polymer, for example Teflon, is the only material or method for constructing a “Close Tolerance Crankshaft Oil Scraper.” The important missing element in the existing art was to be able to safely reduce the clearance down to actual contact in order to obtain the best efficiency. Since the construction and use of the prototype numerous working devices have been constructed by the inventor and are in successful use in street and racing engines worldwide. It is foreseen that a suitable material may have mechanical properties to simultaneously act as a supporting structure and to have safe contact with the moving parts. For example, there are reinforced types of Teflon and Nylon that may be suitable for just such an application.