Two lips seal better than one

Race car engine crankshaft seals are required to cause minimal friction at the same time as maintaining increasingly high crankcase vacuums.

Problem: Crankcase vacuum increases engine power and response because power is not wasted compressing air in the crankcase on the downward piston stroke and also improves piston ring seal because of the increased pressure differential across the ring.

Solution: Race-Tek Nak, based in Eastleigh, Hampshire, has come up with a an elastomeric seal with two PTFE lips. Designer Chris Gregory explained to Eureka that the configuration was adopted as a result of using MSC.MARC FEA analysis to model the performance of a number of possible alternatives. Seals often have a main lip and a dirt excluder lip but in conventional designs, where the dirt lip is a clearance fit, it does not provide satisfactory vacuum retention.
The company makes the seals using its own proprietary manufacturing and bonding processes. A sample shown to Eureka at the just held Autosport Engineering show was mainly made of silicone rubber, but manufacture in other materials is also available if required.

Applications: The PL6 seal extends crankcase vacuum to 25 to 29 inches of mercury at speeds of up to 20,000 rpm. Gregory claims that up to 20 HP may be absorbed in rotating seals in a typical performance car, but by replacing this by his company's low friction designs, it is often possible to at least halve this. The seals are not cheap, but cost a small fraction of that likely to be required to get 10 HP more out of the engine.
The company has 18 years of development experience with this type of product and also makes high performance seals for aerospace and chemical industry customers. TS
Race-Tec NAK
Email to Race-Tec NAK

Author
Tom Shelley

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