CARB® toroidal roller bearings – a revolutionary ... - Acorn Bearings

1 Product information 2 Recommendations 3 Product data
Page ............. 3 Page ............. 12 Bearing data
Cages
Depending on their size, CARB toroidal
bearings are fitted with one of the
following as standard (➔ fig 5 ):
• injection moulded cage of glass
fibre reinforced polyamide 4,6,
roller centred, designation suffix
TN9 (a),
• window-type steel cage, roller
centred, no designation suffix (b),
• window-type brass cage, roller
centred, designation suffix M (c), or
• machined brass cage, inner ring
centred, designation suffix MB (d).
CARB bearings with polyamide
4,6 cages can be operated at temperatures
up to +120 °C. With the exception
of a few synthetic oils and greases
with a synthetic oil base, and lubricants
containing a high proportion of EP
additives when used at high temperatures,
the lubricants generally used
for rolling bearings do not have a
detrimental effect on cage properties.
For bearing arrangements that are
to be operated at continuously high temperatures
or under arduous conditions,
SKF recommends using steel or brass
cages.
Influence of operating temperature
on bearing material
All CARB bearing rings undergo a special
heat treatment so that they can operate
at higher temperatures for extended
periods without causing detrimental
dimensional changes. Of course, the
maximum temperature is dependant on
the cage, lubricant and seals, However,
the rings are heat treated to withstand
200 °C for 2 500 h, or for short periods,
even higher temperatures.
Minimum load
In order to provide satisfactory operation,
CARB toroidal roller bearings,
like all ball and roller bearings, must
always be subjected to a given minimum
load, particularly if they are to
operate at high speeds or are subjected
to high accelerations or rapid
changes in the direction of load. Under
such conditions the inertia forces of
rollers and cage, and the friction in the
lubricant, can have a detrimental
effect on the rolling conditions in the
bearing arrangement and may cause
damaging sliding movements to occur
between the rollers and the raceways.
The requisite minimum load to be
applied to a CARB toroidal roller bearing
with cage can be estimated using
P 0m = 0,007 C 0
and for a full complement bearing
using
P 0m = 0,01 C 0
where
P 0m = minimum equivalent static load,
kN
C 0 = basic static load rating, kN
(➔ product tables)
In some applications it is not possible to
obtain the requisite minimum load. However,
for caged bearings that are oil
lubricated, lower minimum loads are
permissible. These loads can be calculated
when n/n r ≤ 0,3 from
P 0m = 0,002 C 0
and when 0,3 < n/n r ≤ 2 from
Fig
5
P
n
0m = 0,002 C 0 ( 1 + 2 n – 0,3 r
)
where
P 0m = minimum equivalent static bearing
load, kN
C 0 = basic static load rating, kN
(➔ product tables)
n = rotational speed, r/min
n r = reference speed, r/min
(➔ product tables)
When starting up at low temperatures
or when the lubricant is highly viscous,
even greater minimum loads than P 0m
= 0,007 C 0 and 0,01 C 0 respectively
may be required. The weight of the
components supported by the bearing,
together with external forces, generally
exceeds the requisite minimum
load. If this is not the case, the CARB
bearing must be subjected to an additional
radial load.
Equivalent dynamic bearing load
For CARB toroidal roller bearings
P = F r
Equivalent static bearing load
For CARB toroidal roller bearings
P 0 = F r
CARB bearings on adapter sleeves
For CARB bearings with a tapered
bore, SKF also supplies adapter sleeves
(➔ fig 6 ) and withdrawal sleeves.
These enable the bearings to be quickly
and easily secured on smooth or
stepped shafts. Detailed information on
CARB bearings on adapter sleeves can
be found in the product table starting on
page 58.
Where appropriate, modified
adapter sleeves of the E, L and TL
designs, e.g. H 310 E, are available for
CARB toroidal roller bearings, to prevent
the locking device from fouling
the cage. With adapter sleeves of
• series H … E, the standard lock nut
with locking washer (KM + MB) is replaced
by a KMFE lock nut (➔ fig 7 ),
a b c d
Cages for CARB bearings
42