Shopping on line can be easy, simple and save you lots of money. It can also take a lot of your time, frustrate you, and result in unwanted purchases. Now the same can be said for regular high street shopping, but with the vast opportunity presented by the Internet it will pay you to spend a few minutes reading this and understanding how to better optimize your Foil Bearings shopping experience:

1. Compare - without doubt the biggest advantage that the Foil Bearings offers shoppers today is the ability to compare thousands of Foil Bearings at a time. This is a great thing, but not necessarily all the time! Too much can be daunting at times so take advantage of the great comparison sites and where possible let them do the hard work for you.

2. Research - if it has been said it will be on the internet. Ignorance is no longer a justifiable reason for buying the wrong thing. Take the time to research in detail everything that you could possible want to know about

3. Testimonials - don't know anybody that has bought a Foil Bearings? Wrong! If the Foil Bearings is good the internet will let you know. Use the Internet as a friend and get testimonials before you buy.

4. Questions - Got a question about Foil Bearings then search the Forums, FAQ's, Blogs etc. Don't be afraid to ask .....

5. Reputation - Never heard of the company selling Foil Bearings? Don't worry, no reason why you should know every company in the world, but you know someone that does! Use the internet to find out what people are saying about Foil Bearings and build up a picture of their reputation for sales, returns, customer service, delivery etc.

6. Returns - still worried that even after all of the above your Foil Bearings wont be what you want? Check out the returns policy. There is so much competition now that someone, somewhere is bound to offer the terms that you are comfortable with.

7. Feedback - happy with your Foil Bearings then let people know, after all you are depending on others people input in your buying decision, so why not give a little back.

8. Security - check for the yellow padlock on the Foil Bearings site before you buy, and the s after http:/ /i.e. https:// = a secure site

9. Contact - got a question about Foil Bearings, or want to leave a comment then check out the sites contact page. Reputable companies have them and respond.

10. Payment - ready to pay for your Foil Bearings, then use your credit card or PayPal! Be aware of companies that don't accept them, there may be genuine reasons but given the huge amount of choice you have when buying online there is no reason at all not to buy via credit card or PayPal.

Foil bearings are a type of fluid bearing. A shaft is supported by a compliant, spring loaded foil (chemistry) journal lining. Once the shaft is spinning fast enough, the working fluid (usually air), pushes the foil away from the shaft so that there is then no contact. The shaft and foil are separated by the air's high pressure which is generated by the rotation which pulls gas into the bearing via viscosity effects. A high speed of the shaft with respect to the foil is required to initiate the air gap, and once this has been achieved, no wear occurs. Unlike aero or hydrostatic bearings, foil bearings require no external pressurisation system for the working fluid, so the hydrodynamic bearing is self-starting.

Development Foil bearings were first developed in the late 1950s by AiResearch Mfg. Co. of the Garrett SystemsSee entry for Garrett Systems — later acquired by Honeywell. using independent R&D funds to serve military and space applications.Some early history is reported in Giri L. Agrawal, "Foil Air/Gas Bearing Technology — An Overview," American Society for Mechanical Engineers, Publication 97-GT-347 (1997) and Giri L. Agrawal, "Foil Bearings Cleared to Land," Mechanical Engineering 120 (July 1998): 1978-80. They were first tested for commercial use in United Airlines Boeing 727 and Boeing 737 cooling turbines in the early- and mid-1960s.Scholer Bangs, "Foil Bearings Help Air Passengers Keep their Cool," Power Transmission Design (Feb. 1973). Garrett AiResearch air cycle machine foil bearings were first installed as original equipment in 1969 in the DC-10's Environmental Control System. Garrett AiResearch foil bearings were installed on all U.S. military aircraft to replace existing oil-lubricated rolling-contact bearings. The ability to operate at cryogenic gas temperatures as well as at very high temperatures gave foil bearings many other potential applications.M. A. Barnett and A. Silver, "Application of Air Bearings to High-Speed Turbomachinery," Society of Automotive Engineers International, Technical Paper No. 700720 (September 1970), available at http://www.sae.org/servlets/productDetail?PROD_TYP=PAPER&PROD_CD=700720.

Current Generation foil bearings with advanced coatings have greatly exceeded the limitations of earlier designs. Anti-wear coatings exist that allow over 100,000 start/stop cycles for typical applications. New third generation bearings can hold 9000 times their weight, at extremely high speeds.Hooshang Heshmat, "Major Breakthrough in Load Capacity, Speed and Operating Temperature of Foil Thrust Bearings," American Society of Mechanical Engineers, Technical Paper No. WT2005-63712 (September 2005), available at http://store.asme.org/product.asp?catalog_name=Conference%20Papers&category_name=%26nbsp%3b_WTC2005T-5&product_id=WTC2005-63712.

Applications Turbomachinery is the most common application because foil bearings operate at high speed.R. M. "Fred" Klaass and Christopher DellaCorte, "The Quest for Oil-Free Gas Turbine Engines," SAE Technical Papers, No. 2006-01-3055, available at: http://www.sae.org/technical/papers/2006-01-3055. The authors report: "Since the 1960s, aerospace research and development (R&D) has been on a quest to eliminate oil lubrication systems from gas turbine engines. Beginning with small solar power dynamic engines for space applications, U.S. Government and industry have invested millions of dollars to mature this technology for incorporation into modern aircraft propulsion engines. . . . However, this technology has yet to be fielded in aerospace products." The main advantage of foil bearings is the elimination of the oil systems required by traditional bearing designs. Other advantages are:

• Increased reliability
• Higher (unlimited) speed capability
• Higher and lower temperature capability (40 Kelvin to 2500 K)
• No scheduled maintenance
• High vibration and shock load capacity
• Quieter operation

Areas of current research are:

• Higher load capacity
• Improved damping
• Improved coatings

The main disadvantages are:

• Lower capacity than roller or oil bearings
• Wear during start-up
• High speed required for operation

References

See also

• Fluid bearing

External links

• Mohawk Innovative Technology, Inc.
• NASA Foil Bearing Research
• NASA Glenn Research Center

Foil bearings are a type of fluid bearing. A shaft is supported by a compliant, spring loaded foil (chemistry) journal lining. Once the shaft is spinning fast enough, the working fluid (usually air), pushes the foil away from the shaft so that there is then no contact. The shaft and foil are separated by the air's high pressure which is generated by the rotation which pulls gas into the bearing via viscosity effects. A high speed of the shaft with respect to the foil is required to initiate the air gap, and once this has been achieved, no wear occurs. Unlike aero or hydrostatic bearings, foil bearings require no external pressurisation system for the working fluid, so the hydrodynamic bearing is self-starting.

Development Foil bearings were first developed in the late 1950s by AiResearch Mfg. Co. of the Garrett SystemsSee entry for Garrett Systems — later acquired by Honeywell. using independent R&D funds to serve military and space applications.Some early history is reported in Giri L. Agrawal, "Foil Air/Gas Bearing Technology — An Overview," American Society for Mechanical Engineers, Publication 97-GT-347 (1997) and Giri L. Agrawal, "Foil Bearings Cleared to Land," Mechanical Engineering 120 (July 1998): 1978-80. They were first tested for commercial use in United Airlines Boeing 727 and Boeing 737 cooling turbines in the early- and mid-1960s.Scholer Bangs, "Foil Bearings Help Air Passengers Keep their Cool," Power Transmission Design (Feb. 1973). Garrett AiResearch air cycle machine foil bearings were first installed as original equipment in 1969 in the DC-10's Environmental Control System. Garrett AiResearch foil bearings were installed on all U.S. military aircraft to replace existing oil-lubricated rolling-contact bearings. The ability to operate at cryogenic gas temperatures as well as at very high temperatures gave foil bearings many other potential applications.M. A. Barnett and A. Silver, "Application of Air Bearings to High-Speed Turbomachinery," Society of Automotive Engineers International, Technical Paper No. 700720 (September 1970), available at http://www.sae.org/servlets/productDetail?PROD_TYP=PAPER&PROD_CD=700720.

Current Generation foil bearings with advanced coatings have greatly exceeded the limitations of earlier designs. Anti-wear coatings exist that allow over 100,000 start/stop cycles for typical applications. New third generation bearings can hold 9000 times their weight, at extremely high speeds.Hooshang Heshmat, "Major Breakthrough in Load Capacity, Speed and Operating Temperature of Foil Thrust Bearings," American Society of Mechanical Engineers, Technical Paper No. WT2005-63712 (September 2005), available at http://store.asme.org/product.asp?catalog_name=Conference%20Papers&category_name=%26nbsp%3b_WTC2005T-5&product_id=WTC2005-63712.

Applications Turbomachinery is the most common application because foil bearings operate at high speed.R. M. "Fred" Klaass and Christopher DellaCorte, "The Quest for Oil-Free Gas Turbine Engines," SAE Technical Papers, No. 2006-01-3055, available at: http://www.sae.org/technical/papers/2006-01-3055. The authors report: "Since the 1960s, aerospace research and development (R&D) has been on a quest to eliminate oil lubrication systems from gas turbine engines. Beginning with small solar power dynamic engines for space applications, U.S. Government and industry have invested millions of dollars to mature this technology for incorporation into modern aircraft propulsion engines. . . . However, this technology has yet to be fielded in aerospace products." The main advantage of foil bearings is the elimination of the oil systems required by traditional bearing designs. Other advantages are:

• Increased reliability
• Higher (unlimited) speed capability
• Higher and lower temperature capability (40 Kelvin to 2500 K)
• No scheduled maintenance
• High vibration and shock load capacity
• Quieter operation

Areas of current research are:

• Higher load capacity
• Improved damping
• Improved coatings

The main disadvantages are:

• Lower capacity than roller or oil bearings
• Wear during start-up
• High speed required for operation

References

See also

• Fluid bearing

External links

• Mohawk Innovative Technology, Inc.
• NASA Foil Bearing Research
• NASA Glenn Research Center