1. Timken Cylindrical Roller Bearing Product Overview Part A
Cylindrical Roller Bearing Overview
5/7/2007
Timken Cylindrical Roller Bearing Product Overview Part A
Narrated by
David Beach
Motion Industries Retired
Hello! This session will give a detailed product overview for cylindrical roller bearings.

2. Cylindrical Roller Bearing Overview
5/7/2007
Agenda
Features of CRB’s
Basic designs
Roller-raceway profiles
Cage design
Precision
Application considerations
Part numbers
Our agenda includes …..
5/7/2007
CRB Product Overview

3. Features and Advantages
Cylindrical Roller Bearing Overview
5/7/2007
Features and Advantages
We will discuss the design characteristics of cylindrical bearings.

4. Cylindrical Roller Bearing Overview
5/7/2007
CRB Features
Assembly
Separable races for easier installation
Line contact for high radial loads
Single or multi-row designs
Cylindrical or tapered bore
Preset radial clearance
Size range mm bore
Separable Races - Simplifies the assembly process by allowing races to be installed individually. CLICK
Line Contact – More contact for higher loading. CLICK
Single or multi row design - allows for increase capacity.
Cylindrical or tapered bore - selection based on assembly procedures.
Preset Radial Clearance - Manual adjustment of the bearing is not possible during installation, consequently simplifying the assembly process. Since clearance is not adjustable during assembly, clearance is set during manufacturing of the bearing and the optimum clearance must be calculated prior to ordering. Clearance values (C0, C3, etc.) are commonly standardized across manufacturers.
Line Contact
5/7/2007
CRB Product Overview

5. Cylindrical Roller Bearing Overview
5/7/2007
Advantages of CRBs
P (radial load)
Maximum radial load capability
Low friction, high speed capability (under pure radial load)
Extensive float capability
Separable design - flexibility at installation
What are the reasons we would use CRB’s?
As we have discussed Cylindrical Roller Bearings provide the highest available radial load capability in a given envelope compared to tapered, spherical and ball designs.
Cylindrical bearings have Low friction compared to other roller bearings due to no inherent sliding in the bearing unless flanges or side plates are added to handle thrust.
Extensive float capability is limited by the length of the inner race minus the lead in chamfers. Float capability is generally measured as +/- from centerline. Float capability accommodates shaft and thermal growth.
Separable design means that the separable ring which could be inner or outer depending on design type can be mounted to shaft or into housing independent of the rest of assembly. CLICK Note that separable races does not necessarily mean interchangeable. Some bearings are serialized at final assembly and the inner and outer races must be used as a set.
Inner Race Installation Feature
5/7/2007
CRB Product Overview

6. Cylindrical Roller Bearing Overview
5/7/2007
Disadvantages of CRBs
Very limited (up to 10% of radial) or no thrust capability
Limited ability to handle misalignment conditions (<0.0005”/ in)
T (thrust load)
Cylindrical Roller Bearings are not designed to handle thrust. Flanges or side plates can be added to allow bearing to be used in a fixed position, but should only be used for “positional loads”. Thrust load limit is approximately 10% of bearing radial load based on sliding contact stress against flange. The bearing will generate significantly more friction and heat with the extra contact surfaces.
Misalignment capability is limited to what is accommodated in the roller/ race profiling. We design for a limit of in/in as standard. Same as baseline for TRB’s. To determine if the bearings can handle more misalignment, the application can be modeled with Timken analysis tools..
5/7/2007
CRB Product Overview

7. Cylindrical Roller Bearing Overview
5/7/2007
Basic Designs
Now let’s discuss the different cylindrical configurations that are offered.

8. Single Row CRB - Basic Designs
Cylindrical Roller Bearing Overview
5/7/2007
Single Row CRB - Basic Designs NU
Outer ring has two integral ribs
Inner ring has a cylindrical OD without ribs
Supports heavy radial load
Accommodates axial expansion or contraction
Axial displacement between rings with minimum friction while rotating N
Inner ring has two integral ribs
Outer ring has a cylindrical bore without ribs
Before we get into specific design styles, let’s look at part numbering systems. RU, RN, RJ, RF, RT, RP are metric boundaries with Torrington developed internal geometry. We sometimes call these “Torrington max capacity” designs as these geometries will generally have larger rollers/ more capacity than competitor designs.
RIU, RIN, RIJ, RIF, RIT, RIP are inch designs with imperial boundary dimensions. These are usually exclusive to Timken.
Industry standard nomenclature is slightly different and is shown in parentheses. The product that is made in Olomouc follows this part numbering scheme RU=NU RN=N
The next 6 designs will have the same cage configuration. The most popular cage design is the window style with machined bronze cage and riveted ring. The NU configuration is most popular with the separable inner ring with the cage and roller complement mounted to the outer ring.
The next design configuration is the N. This has 2 integral ribs on the inner ring that retains the rollers and cage. Both the N and NU designs cannot handle any thrust since the rollers would slide off the non-ribbed ring if thrust would be applied through the shaft.
5/7/2007
CRB Product Overview

9. Single Row CRB - Basic Designs
Cylindrical Roller Bearing Overview
5/7/2007
Single Row CRB - Basic Designs NJ
Outer ring has two integral ribs
Inner ring has a single rib
Supports heavy radial load
Supports light unidirectional thrust load up to 10% of radial load
The thrust load is transmitted between diagonally opposed rib faces NF
Inner ring has two integral ribs
Outer ring has a single rib
The next 2 designs can handle thrust in 1 direction. When thrust load is applied it is accommodated only through roller sliding against flange. This does add additional friction and reduces speed capability of the bearing.
5/7/2007
CRB Product Overview

10. Single Row CRB - Basic Designs
Cylindrical Roller Bearing Overview
5/7/2007
Single Row CRB - Basic Designs NP
Outer ring has two integral ribs
Inner ring has a single rib
An abutting loose rib
Carries light thrust loads in both directions
Provides axial location
May be used with RN or RU bearing to accommodate axial expansion/contraction
Shaft end play (float) is determined by the bearing axial clearance
NUP
Inner ring has two integral ribs
Outer ring has a single rib
The next 2 designs can handle thrust in both directions. Typically these bearings are paired with a RU or RN in a fixed and float arrangement bearing system when loads are radial direction only. These bearings are designed to handle incidental thrust loads.
5/7/2007
CRB Product Overview

11. Cylindrical Roller Bearing Overview
5/7/2007
Double Row CRBs
Sold as complete assembly, ring roller cage assembly, or separable ring
Not currently a standard Catalog offering. Available in same size range as single row product.
Current designs use NN, NNU nomenclature
Standard cage design is a drilled pocket, finger style bronze retainer NN
Double row bearings are interchangeable so the dimensions - diameter under the rollers (NNU style) and diameter over the rollers (NN style) are held to an ISO/DIN standard. Interchangeability is designed for the ring without the rollers to allow interchange of competitors inner rings.
These are custom designed to meet a specific customer application.
Current designs use NN, NNU nomenclature, some older designs used the classic Torrington nomenclature of RA for NNU and RD for NN.
Standard cage design is a milled machined pocket with a finger style bronze retainer similar to spherical roller bearings. When G forces exceed 20, some applications require the traditional window style with machined bronze cage and riveted ring.
NNU
5/7/2007
CRB Product Overview

12. Thrust Cylindrical Roller
Cylindrical Roller Bearing Overview
5/7/2007
Thrust Cylindrical Roller
Good thrust capacity
TP – multi-row roller pocket configuration
TPS - self adjusting for initial static misalignment TP
TPS CLICK
5/7/2007
CRB Product Overview

13. Roller-raceway Stress Distribution and Roller Profiles
Cylindrical Roller Bearing Overview
5/7/2007
Roller-raceway Stress Distribution and Roller Profiles
In this section we will discuss the significance of roller and race contact.

14. Cylindrical Roller Bearing Overview
5/7/2007
Stress Distribution
Causes of non-uniform stress distribution
Angular misalignment between shaft and housing
Shaft bores not machined or aligned correctly
Housing bores not machined or aligned correctly
Bearings not installed correctly
Extreme loads
Overturning moments
Lead to edge loading, edge stress, reduced life
Roller profiling is a method for achieving more uniform stress distribution
Cylindrical and tapered roller bearings are MORE SENSITIVE TO MISALIGNMENT and edge loading than spherical bearings since the bearings try to maintain a rigid mounting.
Misalignment is defined as the angular difference between the shaft and housing centerlines. It is caused by a number of different factors including:
Shaft bores not machined or aligned correctly
Housing bores not machined or aligned correctly
Bearings not installed correctly
Or extreme loading from gears causing excessive shaft deflection
Higher stresses result in reduced bearing life due to rolling-element fatigue. Roller profiling will redistribute the edge stress along the bearing race. Inner and outer ring raceways are also candidates for profiling. Typically we use profiles on the rollers since this is the most cost effective component to make a change.
5/7/2007
CRB Product Overview

15. Roller Profile Considerations
Cylindrical Roller Bearing Overview
5/7/2007
Roller Profile Considerations
Optimize on load and misalignment
Flat rollers
End tapered
Multi-radius dub (MRD)
Timken analysis tools can predict the optimum bearing profile.
Under operating loads the greatest life will be realized with no edge stresses and maximum roller to race contact. Most of the time this is not realistic.
5/7/2007
CRB Product Overview

16. Cylindrical Roller Bearing Overview
5/7/2007
Roller Profile - MRD
Balanced stress distribution
Standard design
Or application specific
Multi Radius Dub (MRD) profiles give an even or balanced stress distribution without edge stresses. MRD profiles are generated numerically for each point along the raceway.
Timken MRD profiles
5/7/2007
CRB Product Overview

17. Timken Cylindrical Roller Bearing Product Overview Part A
Cylindrical Roller Bearing Overview
5/7/2007
Timken Cylindrical Roller Bearing Product Overview Part A
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