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.Friction |
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Lubrication -
Sealing design -
Cage
shape and material -
Manufacturing precision -
Bearing materials |
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Friction is "the" enemy
when you talk about bearings for good skating. From 100 years experience
we know that internal bearing friction mainly depends on following
criteria
Lubrication
Using an appropriate lubricant is a must to obtain low-friction.. But
lubricant quality and quantity are equally important, since too much
lubricant increases friction. SKF has decades of experience in
lubricants testing and selection.
Oil-lubricated bearings give better rolling than greased bearings, due
to less friction between the components: balls, cage, seals and raceways.
Free running time can even be doubled if one replaces the bearing grease
by an appropriate oil. However oiled bearings needs to be lubricated
very often. Greased bearings can also rotate very well, using an
appropriate quality and quantity of grease. Trust SKF to get bearings
with the right lubricant and quantity having lowest friction. |
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Sealing design
Standard rubber seals protect the bearings very well but at the cost of
friction increase, resulting from the friction between seal and inner
ring and also from the grease churning inside the bearing.Standard
metallic shields avoid the sealing friction but do not avoid possible
grease churning. They also have only a fair protection against dust and
water.
How did SKF solve this problem?
- SKF has developed a non-contacting seal for inline skate. This seal
ensures no friction from the seal with the inner ring and gives better
protection compared to shields.
- SKF has managed to reduce grease churning by applying a lower and
controlled grease quantity.
Cage shape and material
There are 2 main types of cages: moulded polyamide cages and steel
embossed cages.SKF low-friction bearings use both cage types. They have
the smallest contacting surfaces with the balls, and are equipped with
lubricant retainers to avoid any direct contact of the cage with the
balls.For tough use fibreglass reinforced polyamide cages are produced
to ensure better strength and stress resistance. This does not create
any additional friction.
Manufacturing precision
The manufacturing precision of the bearing main dimensions is roughly
described by ISO, ABEC or JIS standards (Read more on precision pages).
Nevertheless, internal bearing friction mainly depends on the finishing
quality of raceways and balls, which is not described by standards! SKF
super-finishing process is the best way to ensure that lowest bearing
friction can be expected.
Bearing materials
The materials used for rings and balls impact significantly the friction
values. Also, some special high quality steels have better hardness and
smaller roughness after super-finishing, which contributes to reduce
friction. SKF has always used the best steels in order to reduce
friction and to help the world move forward. It has been known for years
that friction between ceramic balls and steel raceways is lower than
friction between steel balls and steel railways, especially with reduced
lubrication conditions. |
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