Apparatus for measuring frictional torque in at least one bearing under test

Abstract

An apparatus 2 is provided for measuring frictional torque in a bearing (11, figure 6) under test. Apparatus includes a main body 4, and hub 6 projecting upwardly from a surface 5 of main body, fixed

Description

Axially loaded rotary test machines for tribological testing of lubricants and materials are known. For example, the “four ball test machine” is a known axially loaded rotary test machine. Axially loaded rotary test machines typically comprise a rotating component. The rotating component may be axially loaded against a non-rotating component. For example, the rotating component may apply a load to the non-rotating component which acts parallel to a longitudinal axis of the rotating component. In some examples, axially loaded rotary test machines can be used for investigating sliding friction and wear. In some examples, axially loaded rotary test machines can be used for performing tests on axially loaded bearings. For example, axially loaded rotary test machines can be used for performing tests on bearings which have a rotational axis that is parallel to the axial load applied by the rotating component of the machine. In this way, axially loaded rotary test machines are able to measure the friction generated in bearings which are subjected to an axial load. A different class of machines is known for measuring friction generated in bearings that are subjected to radial loads. For example, some machines can be used for performing tests on radially loaded bearings (e.g., bearings which have a rotational axis that is perpendicular to the load applied by the machine). In such machines, four identical bearings may be tested under the same applied load, by mounting two central bearings in a housing, with two supporting bearings mounted on either side of the two central bearings. In some examples, the two central bearings and the two supporting bearings are mounted on a common shaft, with an opposing force applied to each pair of bearings. The common shaft may be rotated and the resulting torque on the shaft, resulting from friction generated by the bearings, can be measured e.g., with a torque transducer. As identified in co-pending patent application GB2501479.6, an axially loaded rotary test machine may be used to measure frictional loss and / or frictional torque in radially loaded bearings, wherein the radially loaded bearings are arranged in an apparatus such that the outer races of the radially loaded bearings are configured to rotate (via a rotating mechanism of the axially loaded rotary test machine) but the inner races of the radially loaded bearings do not rotate. For example, the outer race of the radially loaded bearing may be secured to a component that is arranged to rotate, such thatthe outer race of the bearing rotates and the inner race of the radially loaded bearing may be mounted and secured to a non-rotating component (e.g., a non-rotating axle), such that the inner race of the bearing does not rotate. Therefore, currently an axially loaded rotary test machine may be used to measure frictional loss and / or frictional torque in bearings (for example, vehicle wheel bearings) that are typically subjected to radial loads and are mounted such thatthe outer race of the bearing rotates but the inner race of the bearing does not rotate. However, in other engineering applications, rolling element bearings may be used. In use, rolling element bearings may be arranged such that the rolling element bearing inner races are connected to a component that is configured to rotate (and therefore the rolling element bearing inner races rotate) and the outer rolling element bearing races are connected to a non-rotating component (and therefore the rolling element bearing outer races do not rotate). This arrangement of rolling element bearings may be typically associated with the arrangement of bearings used in rotating machinery such as electric motors, pumps, turbines and shafts in gearboxes. For pumps and turbines, the load on the bearings is primarily an axial load. For electric motors, the load on the bearings may be an axial load or a radial load (e.g., where power is transmitted through a pulley or gear mounted on a motor shaft, resulting in a radial load on the shaft bearings). For gearboxes, the torque transmitted between gear teeth may result in the generation of radial forces on the gear shaft, and hence the shaft bearings. For spur gears, the load on the shaft bearings may be purely radial. For helical gears, the load on the shaft bearings may be a combination of axial thrust and radial load. It is identified in the present disclosure that currently, axially loaded rotary test machines are not able to measure frictional loss and / or frictional torque in radially loaded bearings where the inner races of the radially loaded bearings rotate in use, but the outer races of the radially loaded bearings do not rotate in use. For example, axially loaded rotary test machines are currently not able to measure frictional loss and / or frictional torque in rolling element bearings (e.g., as described above) and / or bearings used in rotating machinery. Further, it is identified in the present disclosure that known machines suitable for measuring friction and / or frictional torque in radially loaded bearings in which the inner races are arranged to rotate but the outer races do not rotate are larger and more expensive than axially loaded rotary test machines. In this way, measuring friction and / or frictionaltorque in radially loaded bearings where the inner races are configured to rotate and the outer races do not rotate may not be accessible and / or may be expensive to users. It is an aim of the present disclosure to overcome or mitigate these drawbacks. The present disclosure aims to provide an apparatus and system for testing bearings and / or lubricants for bearings that are radially loaded and that comprise an inner race that is configured to rotate and an outer race that does not rotate, using an axially loaded rotary test machine. The present disclosure aims to provide an apparatus for enabling the measurement of frictional torque in said radially loaded bearings, in a more efficient and more economical manner. The present disclosure further provides a system for enabling the measurement of frictional torque in radially loaded bearings with an inner race configured to rotate and an outer race that does not rotate, in a more efficient and more economical manner. Summary Accordingly, in a first aspect the present invention provides an apparatus for measuring frictional torque in at least one bearing under test, according to claim 1. In a second aspect the present invention provides a system for measuring frictional torque in at least one bearing under test, according to claim 21. Preferred features of these aspects of the present invention are defined in the respective dependent claims. It will also be noted that unless expressly stated otherwise features of the various aspects can be combined in any way to form other aspects of the invention. Brief description of drawings Figures 1 and 2 schematically show a perspective view of an apparatus according to an embodiment of the invention; Figures 3 and 4 schematically show a plan view of an apparatus according to an embodiment of the invention; Figure 5 schematically shows an interaction between a mechanism of the apparatus and a shaft of a rotary test machine; Figures 6 to 9 schematically show a perspective view of the apparatus according to an embodiment of the invention; Figure 10 schematically shows an example system according to an embodiment of the invention; Figure 11 schematically shows an example system according to an embodiment of the invention; and Figure 12 schematically shows forces acting on a bearing support assembly of the apparatus. Detailed description Some examples will now be described in more detail with respect to Figures 1 to 12. Figures 1 and 2 schematically show an apparatus 2 according to an example. An x-y-z coordinate system is schematically shown in Figures 1 and 2, and will be referred to hereon. In examples, thex-y plane may be considered to define a horizontal plane, and the z-axis may be considered to define a vertical axis that is orthogonal to the horizontal plane. The apparatus 2 comprises a main body portion 4 and a hub 6. In some examples the hub 6 is fixed to a surface 5 of the main body portion 4. In some examples, the hub 6 is fixed for rotation to the surface 5 of the main body portion 4. In other words, the hub 6 does not rotate relative to the surface 5 of the main body portion 4. In some examples, the hub 6 projects from the main body portion 4. For example, the hub 6 projects upwardly from the surface 5 of the main body portion 4. Using the x-y-z coordinate system, the surface 5 of the main body portion 4 lies in a plane that is parallel to the x-y plane. In some examples it may be considered thatthe surface 5 is generally flat. In some examples, the hub 6 may project upwardly from the surface 5 of the main body portion 4 along the z-axis or parallel to the z-axis. In some examples, the hub 6 may be circular in outer profile in plan view. The hub 6 may be cylindrical. For example, the hub 6 may comprise a cylindrical bar. In some examples, the hub 6 may comprise a hexagonal bar. In some examples, the main body portion 4 is circular in outer profile in plan view. In some examples the main body portion 4 is cylindrical. The main body portion 4 may be configured to rotate about a longitudinal axis of the hub 6. The longitudinal axis of the hub 6 is shown in Figure 1 by the dotted line Z-Z. In other words, the main body portion 4 may be configured for rotation around axis Z-Z which passes centrally through the hub 6. In some examples, the main body portion 4 may comprise aluminium. In some examples, the hub 6 may comprise steel. For example, the hub 6 may comprise tool steel or bearing steel. The apparatus 2 comprises a bearing support assembly 43 for supporting / carrying a bearing assembly 10. The bearing assembly 10 may comprise: at least one bearing 11 (e.g. including the inner race 48, outer race 47 and rolling element(s) of the bearing 11); and a lubricant coating the at least one bearing 11. In some examples, the rolling element of the at least one bearing 11 may comprise a bearing cage. The bearing support assembly 43 may comprise a first bearing support portion 44 for engaging with the hub 6, a second bearing support portion 45 connected to the first bearing support portion 44 and for supporting an outer race 47 of at least one bearing 11 of the bearing assembly 10 and a third bearing support portion 46 for supporting an inner race 48 of the at least one bearing 11 of the bearing assembly 10. The bearing support assembly 43 may be circular in cross section. Each of the first bearing support portion 44, second bearing support portion 45 and third bearing support portion 46 may be circular in cross section. In some examples (and as shown in Figure 6), the first bearing support portion 44 comprises an inner portion 44a and an outer portion 44b. The inner portion 44a may be configured to be inserted or screwed into a recess (or hole) 51 in the hub 6 for connecting the bearing support assembly 43 and the hub 6. Stated differently, an outer surface 52 of the hub 6 may comprise a recess 51 or hole in which the inner portion 44a of the first bearing support portion 44 can be inserted or screwed into. In some examples, there is a threaded engagement or connection between the first bearing support portion 44 (e.g., the inner portion 44a) and the hub 6. For example, the recess 51 in the hub 6 may comprise a threaded recess (e.g., a female thread) and the inner portion 44a may comprise a male thread such that the inner portion 44a can be screwed into or connected to the recess 51 of the hub 6 via a threaded engagement. In cross section, the first bearing support portion 44 may be generally shaped as a brace (e.g., “ } ”). In some examples, the outer portion 44b of the first bearing support portion 44 extends out of the recess 51 of the hub 6 such that the outer portion 44b engages with an outer surface 52 of the hub 6. In some examples, the hub 6 comprises a cylindrical bar with one or more spot faces (or flat faces). In some examples, the hub 6 comprises a hexagonal bar with one or more flat faces. The outer portion 44b of the first bearing support portion 44 may engage with a spot face or flat face of the hub 6 so that the outer portion 44b of the first bearing support portion 44 lays flat against the outer surface 52 of the hub 6. In some examples, the second bearing support portion 45 may be connected to the first bearing support portion 44 via a threaded engagement or connection. In examples, when the second bearing support portion 45 is secured ortightened to the first bearing support portion 44 (e.g., via the threaded engagement), this enables the outer race 47 of the at least one bearing 11 to be located and clamped in a fixed position (e.g., such that the outer race 47 is not able to move). In some examples, the third bearing support portion 46 comprises an outer sleeve portion 49 and an inner sleeve portion 50. The third bearing support portion 46 may be “E” shaped in cross section. The third bearing support portion 46 may comprise a crowned radius outer diameter. The inner sleeve portion 50 may be configured to be inserted through a centre of the at least one bearing 11. The inner sleeve portion 50 may be configured to engage with the inner race 48 of the at least one bearing 11 for causing the inner race 48 of the at least one bearing 11 to rotate. The outer sleeve portion 49 may be configured to fit over the second bearing support portion 45 such that the outer sleeve portion 49 is separated from the second bearing support portion 45 by a gap. The outer sleeve portion 49 may be configured to fit over a portion of the second bearing support portion 45 such that the outer sleeve portion 49 covers a first portion 45a of the second bearing support portion 45 but does not cover a second portion 45b of the second bearing support portion 45. In examples, the gap between the third bearing support portion 46 and the second bearing support portion 45 is to ensure that when the third bearing support portion 46 (and thus the inner race 48 of the at least one bearing 11) is caused to rotate (as described in more detail below), the second bearingsupport portion 45 remains stationary or still (and therefore the outer race 47 of the at least one bearing 11 does not rotate). Said gap between the outer sleeve portion 49 and the second bearing support portion 45 may be, but is not limited to, between 1 mm to 2mm. The apparatus 2 may comprise a holding arrangement 38. The holding arrangement 38 may be configured to extend through a centre of the at least one bearing 11 and / or a centre of the inner sleeve portion 50 of the third bearing support portion 46. The holding arrangement 38 may be configured to provide an axial load (e.g., a pre-axial load) to the at least one bearing 11, wherein said axial load may be for holdingorsecuring the third bearing support portion 46 to the inner race 48 of the at least one bearing 11 of the bearing assembly 10. In some examples, the holding arrangement 38 comprises a screw (or bolt) 39 and nut 40 arrangement. In some examples, the holding arrangement 38 may comprise at least one wave washer or spring washer 41 configured to engage with a head 42 of the screw (or bolt) 39. The at least one wave washer or spring washer 41 may allow control of the axial load tension (e.g., pre-axial load) provided by the holding arrangement 38. Stated differently, the wave washer or spring washer may be tightened and / or loosened to adjust the pre-axial load applied to the at least one bearing 11. Where the bearing assembly 10 comprises more than one bearing 11a, 11b, the holding arrangement 38 may provide the pre-axial load to the bearings 11a, 11 b by squeezing or pushingthe respective inner races 47 of the respective bearings 11a, 11b together. In examples, the bearingsupport assembly 43 maybe assembled with the at least one bearing assembly 10 as follows. The at least one bearing assembly 10 may be mounted in the second bearing support portion 45 (e.g., with a sliding fit). Stated differently, the second bearing support portion 45 may slide over the bearing assembly 10. Where the bearing assembly 10 comprises more than one bearing 11 a, 11 b, a bearing spacer may be used to separate the respective outer races 47 of each respective bearing 11a, 11 b. A first portion of the holding arrangement 38 may be positioned (e.g., loosely positions) against the inner race 47 of one of the at least one bearing 11. For example, a nut 40 may be positioned (e.g., loosely positions) against the inner race 47 of one of the at least one bearing 11. The second bearing support portion 45 may be connected to the first bearing support portion 44 (e.g., via the threaded engagement as described above). The inner sleeve portion 50 of the third bearing support portion 46 may be inserted into the centre of the bearing assembly 10, such thatthe innersleeve portion 50 engages with the inner race 47 of the at least one bearing 11. A second portion of the holding arrangement 38 (e.g., the screw 39) may engage with the first portion of the holding arrangement 38 (e.g., the nut 40) to secure or clamp the third bearing support portion 46 in place. Wave or spring washers 41 may be used to provide an axial pre-load on the at least one bearing 11. The assembled bearing support assembly 43 (e.g., comprising the bearing assembly 10, first bearing support portion 44, second bearing support portion 45, third bearing support portion 46 and holding arrangement 38) may be connected to the hub 6. For example, the inner portion 44a of the first bearing support portion 44 may be inserted into a recess 51 in the hub (as described above in further detail). The assembled bearing support assembly 43 may be connected or secured to the hub 6 by rotating or screwing the second portion 45b of the second bearing support portion 45 (e.g., the portion of the second bearing support portion 45 that is not covered by the outer sleeve portion 49 of the third bearing support portion 46). In examples, the second portion 45b of the second bearing support portion 45 may comprise spanner flats or lateral holes / slots for a spanner (e.g., a C-spanner) to aid the rotation of the second portion 45b of the second bearing support portion 45. In examples, connecting or securing the hub 6 and the bearing support assembly 43 by rotating the second portion 45b of the second bearing support portion 45 may ensure that the outer race 47 of the at least one bearing are clamped orfixed in place (e.g., such thatthey cannot move) and / or that the connection between the bearing support assembly 43 and the hub 6 is tight or secure (e.g., such that when the third bearing support portion 46 is configured to rotate, the bearing support assembly 43 remains connected to the hub 6). In some examples, the bearing support assembly 43 may comprise steel. For example, the bearing support assembly may comprise tool steel or bearing steel. In some examples, the bearing support assembly 43 (e.g., each of the first bearing support portion 44, the second bearing support portion 44 and the third bearing support portion 46) may be made or manufactured by turning parts (e.g., to achieve the basic geometry and dimensions of the bearing support assembly 43 and by heat treating the steel of the bearing support assembly 43 for hardening. Some surfaces (e.g., mating surfaces) of the bearing support assembly 43 may be ground to precise tolerances and surface finish, for enabling an optimised fit and performance of the bearing support assembly 43. In some examples, the hub 6 may be configured to support more than one bearing support assembly 43. For example, and as shown in Figure 3, the hub 6 may be configured to support three bearing support assemblies 43. Each respective bearing support assembly 43 may be configured to supporta respective bearing assembly 10. An outer surface 52 of the hub 6 may comprise a plurality of recesses (or holes) 51 in which a respective inner portion 44a of a respective first bearing support portion 44 of a respective bearing support assembly 43 can be inserted or screwed into (as described above). The plurality of recesses 51 may be spaced equally around the outer surface 52 of the hub 6 and as such, the respective bearing support assemblies 43 inserted in the respective recesses 51 may be spaced equally around the hub 6 .For example, where the hub 6 is configured to support three bearing support assemblies 43, the hub 6 may comprise three recesses 51. The three recesses 51 may be equally spaced around the outer surface 52 of the hub 6 at an angle of 120 degrees from each other. In this way, when the three bearing support assemblies 46 are inserted into a respective recess 51, the three bearing support assemblies may be equally spaced around the hub at an angle of 120 degrees from each other. In some examples, the at least one bearing 11 may include at least one of: a pair of angular contact ball bearings; a pair of taper roller bearings; a deep groove ball bearing; a roller bearing; a needle roller bearing; a spherical roller bearing; or a plain bearing. In some examples, the at least one bearing 11 is coated in a lubricant (e.g., an oil or a grease). In some examples, the at least one bearing 11 is dry (e.g., is not coated in a lubricant). This is also equally applicable to bearings 12 and 13. In some examples, the bearing assembly 10 may comprise only one bearing 11 (as shown in Figure 9). As an example, the bearing 11 shown in Figure 9 may be a deep groove ball bearing. In some examples, the bearing assembly 10 comprises more than one bearing 11. Where the bearing assembly 10 comprises more than one bearing, an inner race 48 of each respective bearing 11 may be separated from each other by a gap. Figures 6, 7and 8 show an example where a bearing assembly 10 comprises a pair of opposing bearings 11 a, 11 b. An inner race 48a, 48b of each respective bearing of the pair of opposing bearings 11 a, 11 b may be separated by a gap. In some examples, the pair of opposing bearings 11a, 11b may include two identical types of bearing. For example, the pair of opposing bearings 11 a, 11 b may include two angular contact ball bearings or two taper roller bearings. In some examples, the pair of opposing bearings 11a, 11b may include two different types of bearing. For example, the pair of bearings 11a, 11b may comprise one cylindrical roller bearing and one deep groove ball bearing. In some examples, the pair of opposing bearings 11a, 11b may be mounted back-to-back. In some examples, each of the pair of opposing bearings 11a, 11b are coated in a lubricant (e.g., an oil or a grease). In some examples, each of the pair of opposing bearings 11a, 11 b are dry (e.g., are not coated in a lubricant). The apparatus 2 may comprise a mechanism 14. In some examples, the mechanism 14 may be termed a loading and driving mechanism. In some examples, the material of the mechanism 14 comprises steel. In some examples, the mechanism 14 comprises a rotatable disc 19. In some examples, the mechanism 14 is connected to a shaft 30 (or a spindle) of a rotary test machine 16 (e.g., an axially loaded rotary test machine). This shaft 30 may be configured to rotate. Figures 5 and 7-9 schematically show the connection between the mechanism 14 and the shaft 30 of a rotary test machine 16. Figures 10 and 11 schematically show example systems 32 of a rotary test machine 16 connected to the apparatus 2. Suitable examples forthe rotary test machine 16 include the Phoenix Tribology Limited TE 92 Rotary Tribometer and the Phoenix Tribology Limited TE 92HS Rotary Tribometer- High Speed. In some examples, the mechanism 14 is configured to contact the third bearing support portion 46. The mechanism 14 may be configured to apply a radial load to the third bearing support portion 46. The radial load may be applied in a direction that is parallel or substantially parallel to the longitudinal axis (Z-Z) of the hub 6. As the third bearing support portion 46 supports an inner race 48 of at least one bearing 11, the mechanism 14 may apply a radial load to the inner race 48 of the at least one bearing 11. Said radial load applied to the inner race 48 of the at least one bearing 11 may be transmitted through rolling elements of the at least one bearing 11. The radial load transmitted through rolling elements of the at least one bearing 11 may be reacted by an equal and opposite force applied by the outer race 47 of the at least one bearing 11 (and therefore by the second bearing support portion 45). The radial load may be applied in a direction that is parallel to the longitudinal axis (Z-Z) of the hub 6. Stated differently, the mechanism 14 may be configured to apply a load to the third bearing support portion46 (and as such the inner race 48 of the at least one bearing 11) along the z-axis, wherein the load applied by the mechanism 14 acts downwardly on the third bearing support portion 46 and the inner race 48 of the at least one bearing 11. The mechanism 14 may also apply a rotational drive force to the third bearing support portion 46 for causing the inner race 48 of the at least one bearing 11 to rotate about a direction orthogonal to the longitudinal axis of the hub 6 (X-X). The second bearing support portion 45 is configured or arranged to hold the outer race 47 of the at least one bearing 11 still so that the outer race 47 does not rotate whilst the inner race 48 is rotating. As the third bearing support portion 46 supports an inner race 48 of at least one bearing 11, the mechanism 14 may apply a rotational drive force to the inner race 48 of the at least one bearing 11. In this way, the rotational drive force may be configured for causing the inner race 48 of the at least one bearing 11 to rotate about a direction orthogonal to the longitudinal axis of the hub 6 (X-X). In this way, the radial load applied by the mechanism 14 may be applied to the third bearing support portion 46 (and / or the inner race 48 of the at least one bearing 11) in a direction that is orthogonal to the rotational axis of the inner race 48 of the at least one bearing 11. In some examples, the bearing support assembly 43 may not contact the surface 5 of the main body portion 4. For example, there may be a space or gap between the periphery of the bearing support assembly 43 and the main body portion 4. As shown by double-sided arrow 29 in Figure 12, there is a space or gap 29 between the surface 5 of the main body portion 4 and a base 33 of the bearing support assembly 43. In some examples, the bearing support assembly 43 may be supported by the hub 6 such thatthe top of the bearing support assembly 43 (e.g., the top of the outer diameter of the third bearing support portion 46) projects, along the z-axis, above the hub 6. In this way, the mechanism 14 may come into contact with the third bearing support portion 46 but not the hub 6. The apparatus 2 may further comprise an outer casing 24. This is schematically shown in Figure 2. In some examples, the outer casing 24 may project vertically / upwardly from a surface 5 of the main body portion 4. For example, the outer casing 24 may project along the z-axis from a surface 5 of the main body portion 4 (e.g., wherein the main body portion 4 lies in a plane that is parallel to the x-y plane). In some examples, the outer casing 24 may be circular in outer profile in plan view and / or cylindrical. For example, the outer casing 24 may conform to the circular (or substantially circular) shape of the main body portion 4. In some examples, the outer casing 24 may extend vertically / upwardly / along the z-axis from an outer periphery of the main body portion 4. In some examples, the outer casing may surround at least one of: the hub 6; the bearing support assembly 43; and the bearing assembly 10. In some examples, the outer casing 24 comprises aluminum. In some examples, the outer casing 24 is for containing a lubricant that is coating the at least one bearing 11. For example, the outer casing 24 may prevent the lubricant (e.g., grease or an oil) from ejecting outside of the outer casing 24. As shown in Figures 6 to 9, a portion (e.g., an underside) of the main body portion 4 may be configured to be connected to a ball thrust bearing 22 of a rotary test machine 16 (e.g., an axially loaded rotary test machine). For example, the main body portion 4 is configured to be mounted and / or seated on a ball thrust bearing 22 of a rotary test machine 16. The apparatus 2 comprises an arrangementfor measurement of a reaction torque against rotation of the main body portion 4 caused by the rotational drive force applied to the inner race 48 of the at least one bearing 11 by the mechanism 14. In examples the arrangement comprises an engagement portion that is arranged to engage with a corresponding reaction torque measurement device. Two main embodiments for the arrangement are disclosed herein. Afirst embodiment is shown in e.g. Figure 4 which shows an engagement portion 18 that is arranged to engage a reaction torque measurement device 26, the reaction torque measurement device 26 comprising a load cell 31. A suitable example of the load cell 31 is the Applied Measurements Ltd. 10Nm Flange type Static / Reaction Torque Transducer- DTD-F. A second embodiment is shown in e.g. Figure 10 which shows an engagement portion 36 that is arranged to engage a reaction torque measurement device 37 comprising a torque transducer 34. These are discussed in more detail below. In some examples, the apparatus 2 comprises an engagement portion 18, 36. The engagement portion 18, 36 may be configured to engage with a reaction torque measurement device 26, 37. The reaction torque measurement device 26, 37 may comprise a load cell 31 or a torque transducer 34. In some examples, the reaction torque measurement device 26,37 is configured to measure a reaction torque against a rotation of the main body portion 4. For example, the reaction torque measurement device 26, 37 is configured to measure a reaction torque against a rotation of the main body portion 4 that is caused by a rotational drive force applied to the inner race 48 of the at least one bearing 11. The reaction torque may be indicative of frictional torque in the bearing assembly 10. For example, the reaction torque may be indicative of frictional torque in the at least one bearing 11. In some examples, the engagement portion 18 comprises a torque arm 23. In some examples, the torque arm 23 projects outwardly from the main body portion 4, as shown in Figures 1, 2, 3, 4 and 11. For example, the torque arm 23 projects outwardly from the main body portion 4 by a length of 100mm. The length of projection of the torque arm 23 may differ based on the size of the apparatus 2. In some examples, the torque arm 23 comprises steel. In some examples, the torque arm 23 is configured to be restrained for rotation by a restraining member 35 (as shown in Figure 4). For example, the restraining member 35 may react against rotational movement of the main body portion 4. In some examples, the torque arm 23 comprises the reaction torque measurement device 26. For example, the torque arm 23 comprises a load cell 31 (e.g., the load cell is located on the torque arm 23). In some other examples, the restraining member 35 comprises the reaction torque measurement device 26. For example, the restraining member 35 comprises a load cell 31 (e.g., the load cell 31 is located on the restraining member 35). In some examples, the load cell 31 is configured for measuring a reaction torque against rotation of the main body portion 4. In some other examples, and as shown in Figure 10, the engagement portion of the apparatus 2 comprises an engagement portion 36 located on an underside of the main body portion 4. In some examples, the engagement portion 36 is configured to engage with a reaction torque measurement device 37. In some examples, the reaction torque measurement device 37 comprises a torque transducer 34. Therefore, in the example of Figure 10 it may be considered that the engagement portion 36 is configured to engage with a torque transducer 34 located below the main body portion. In some examples, the engagement portion 36 is configured to engage directly with a torque transducer 34. For example, the main body portion 4 is configured to be mounted on the torque transducer 34. In some examples, the torque transducer 34 is part of the rotary test machine 16. In some examples, the torque transducer 34 is configured for measuring a reaction torque against rotation of the main body portion 4. Figures 10, 11 and 12 schematically show a system 32 for measuring frictional torque in at least one bearing 11 under test. Figures 10 and 11 schematically show a system 32 comprising the apparatus 2 of any of Figures 1 -9 and a typical axially loaded rotary test machine 16. Figure 12 schematically shows the forces acting on the bearing support assembly 43of the apparatus 2 shown in any of Figures 1 to 9, when the apparatus 2 is connected to a rotary test machine 16 (e.g., an axially loaded rotary test machine). In particular, Figure 12 schematically shows the forces acting on the third bearing support portion 46 of the apparatus 2. As the third bearing support portion supports the inner race 48 of at least one bearing 11, Figure 12 also shows the forces acting on the inner race 48 of the at least one bearing 11 .The forces acting on the third bearing support portion 46 and the inner race 48 of the at least one bearing 11 of the apparatus 2 are shown using labels A, B, C and D in Figure 12. In some examples, the base 21 of the main body portion 4 is configured to receive an axial load from the rotary test machine 16. In other words, the rotary test machine 16 comprises means 28 for applying an axial load to a base 21 of the main body portion 4 of the apparatus 2. This axial load may be thus indirectly applied to the third bearing support portion 46. This axial load is shown in Figure 12 by dotted arrow A. The axial load is applied in a direction that is parallel to a longitudinal axis (Z-Z) of the hub 6 (e.g., in a direction parallel to the positive z-axis that acts upwardly on the third bearing support portion 46. This axial load may be for raising the main body portion 4 (and thus the third bearing support portion 46) to the mechanism 14, when the mechanism 14 is attached to the shaft 30 of the rotary test machine 16. Figure 11 shows a pneumatic bellows as an example means 28 for providing this axial load to the apparatus 2. In some examples, the means for providing an axial load to the base 21 of the main body portion 4 of the apparatus 2 may comprise at least one of: one or more pneumatic bellows; one or more pneumatic cylinders; a dead-weight; a servomotor; or a spring. In some examples, the apparatus 2 may be connected to a rotary test machine 16. For example, the rotary test machine 16 may be connected to the mechanism 14 of the apparatus 2 (e.g., via a rotating shaft 30 of the rotary test machine 16). In this way, when the shaft 30 of the rotary test machine engages the mechanism 14, the shaft 30 of may apply an axial load to the mechanism 14 of the apparatus 2. For example, the rotary test machine 16 may apply an axial load to the mechanism 14 that is parallel to the longitudinal axis shaft 30. For example, where the shaft 30 extends along the z-axis (as shown in Figures 1 and 2), the rotary test machine 16 and / or shaft 30 may apply a force along the z-axis that acts downwardly on the mechanism 14. The shaft 30 of the rotary test machine 16 may be configured to rotate, for example about axis z-z. In this way, when the shaft 30 of the rotary test machine 16 engages the mechanism 14, a rotational drive force of the shaft 30 may be applied to the mechanism 14, causing the mechanism 14 to rotate. In some examples, the shaft 30 may rotate clockwise. In other examples, the shaft may rotate anticlockwise. The mechanism 14 will rotate in the same direction as the shaft 30. In some examples, the mechanism 14 is configured to engage with the third bearing support portion 46of the apparatus 2. In this case, the mechanism 14 may apply a radial load to the third bearing support portion 46 (and therefore the inner race 48 of the at least one bearing 11). This radial load is shown by dotted arrow B in Figure 12. As shown, the radial load may be applied to the inner race 48 of the at least one bearing 11 in a direction that is parallel to the longitudinal axis (Z-Z) of the hub 6 (e.g., in a direction parallel to the negative z-axis that acts downwardly on the third bearing support portion 46. The radial load applied to the inner race 48 of the at least one bearing 11 acts in a direction perpendicular to the rotational axis of the inner race 48 of the at least one bearing 11. As the mechanism 14 is caused to rotate via the shaft 30 of the rotary test machine, the mechanism 14 may also apply a rotational drive force to the third bearing support portion 46 (and as such the inner race 48 of the at least one bearing 11). The rotational drive force is not applied to the first bearing support portion or the second bearing support portion 45, and therefore the rotational drive force is not applied to the outer race 47 of the at least one bearing. The outer race 47 of the at least one bearing remains stationary whilst the inner race 48 of the at least one bearing 11 rotates. The rotational drive force is schematically shown in Figure 12 by dotted arrow C. The rotational drive force C is applied to the inner race 48 of the at least one bearing 11 in a direction that is orthogonal to the radial load B applied to the inner race 48 of the at least one bearing 11. In some examples, the rotational drive force C may be applied in the opposite direction to that shown in Figure 12, dependent upon the direction in which the mechanism 14 is rotated. For example, the mechanism 14 may rotate clockwise or anticlockwise. The rotational drive force may be configured for causingthe inner race 48 of the at least one bearing 11 to be rotated about a direction orthogonal to the longitudinal axis (Z-Z) of the hub 6. In some examples, when the inner race 48 of the at least one bearing 11 is caused to rotate by the mechanism 14, total frictional losses of the at least one bearing 11 may cause a frictional torque to be generated in the at least one bearing 11 (e.g., between the inner race 48 and the outer race 47 of the at least one bearing 11). This frictional torque generated in the at least one bearing 11 (e.g., between the inner race 48 and the outer race 47 of the at least one bearing 11) may be caused by, for example, at least one of: rolling contact / friction of the inner race 48 of the at least one bearing 11; frictional losses caused by shearing and / or churning of lubricants (e.g., grease or oil) coating the at least one bearing (e.g., coating the inner race 48 and / or outer race 47 of the at least one bearing 11); rolling friction between the inner race 48 and the rolling element(s) of the respective at least one bearing 11; slidingfriction between the rolling element(s) and the respective bearing cage; and rolling friction between the rolling elements and the outer race 48. In some examples, the rolling friction between the inner race 48 and rolling element(s) of a respective bearing 11 and / or the rolling friction between the outer race 47 and the rolling element(s) of the respective bearing 11 may depend on the radial load applied to the inner race 48 of the at least one bearing 11 .In some examples, the frictional losses caused by shearing / churning of lubricants coating the at least one bearing 11 may depend on the speed of rotation of the inner race 48. In examples, the faster the inner race 48 of the at least one bearing 11 rotates (e.g., the larger the rotational drive force on the inner race 48 of the at least one bearing 11), the higher the churning of lubricants and / or the higher the shearing of lubricants (which may primarily occur between the rolling element(s) and the outer race 47 and / or inner race 48).In some examples, the sliding friction between the rolling element(s) and the respective bearing cage may depend on the speed of rotation of the inner race 48. In some examples, the frictionaltorque generated in the at least one bearing 11 is reacted by a resisting force. This resisting force acts in the opposite direction to the rotational drive force C and the frictional torque generated in the at least one bearing 11. This resisting force is schematically shown by the dotted arrow labelled D, in Figure 12. The resisting force D acts on the holding arrangement 38 (e.g., the screw 39) that holds the third bearing support portion 46 to the inner race 48 of the at least one bearing 11. In some examples, the resisting force D acting against the rotation of the inner race 48 of the at least one bearing 11 may cause the main body portion 4 to try to rotate. As the hub 6 is fixed to the main body portion 4, the hub 6 will also rotate about its axis. In some examples, the rotational axis of the hub 6 and main body portion 4 is parallel to the z-axis. Stated differently, the hub 6 and main body portion 4 may rotate about the longitudinal axis (Z-Z) of the hub 6. In some examples, a reaction torque may act to resist the rotation of the main body portion 4. In some examples, and as shown in Figure 10, an engagement portion 36 located on an underside of the main body portion 4 engages with a torque transducer 34, wherein the torque transducer is located below the main body portion 4. In this example, the torque transducer 34 may apply a reaction torque which may act to resist the rotation of the main body portion 4. In this way, the torque transducer 34 may measure and / or determine the reaction torque for resisting the rotation of the main body portion 4. In an alternative example, and as shown in Figure 4, the apparatus 2 may comprise a torque arm 23. In some examples, the torque arm 23 is configured to be restrained for rotation by a restraining member 35. The torque arm 23 may comprise a load cell 31 or the restraining member 35 may comprise a load cell 31, to measure the reaction torque. A base 21 or underside of the main body portion 4 may be configured to sit on a ball thrust bearing 22 of the rotary test machine 16. In this example, at least one of the torque arm 23, restraining member 35 and / or load cell 31 are configured for torque reaction mounting the apparatus 2. For example, the ball thrust bearing 22 enables the main body portion 4 to rotate when the apparatus 2 is seated and / or mounted on the ball thrust bearing 22 (as shown in Figure 12). When the main body portion 4 rotates, the ball thrust bearing 22 may enable the main body portion 4 to freely rotate (e.g., with minimal resisting friction from the ball thrust bearing 22). The main body portion 4 may continue to rotate until the torque arm 23 comes into contact with the restraining member 35 (e.g., when the torque arm 23 is restrained by the restraining member 35). In this case, any friction generated in a plane perpendicular to the axis of rotation of the main body portion 4, may result in a force on the load cell 31. For example, where the axis of rotation of the main body portion 4 is along the z-axis, a reaction torque resisting the rotation of the main body portion 4, generated in a direction parallelto the x-y plane and provided by the restraining member35 restrainingthe torque arm 23, may result in an opposite and equal force on the load cell 31. The load cell 31 may then measure and / or determine the force on the load cell 31 (and as such the reaction torque for resisting the rotation of the main body portion 4). In some examples, the measurement of the reaction torque against the rotation of the main body portion 4, measured by the reaction torque measurement device (e.g., the torque transducer 34 or load cell 31), is indicative of the frictional torque generated in the at least one bearing 11. For example, a value of zero measured by the torque transducer 34 or load cell 31 may indicate that no frictional torque is generated in the at least one bearing 11 i.e. a hypothetical perfect bearing. In some examples, a value higher than zero measured by the torque transducer 34 or load cell 31 may indicate that frictional torque is generated in the at least one bearing 11. In some examples, a higher value measured by the torque transducer 34 or load cell 31, indicates a higher frictional torque generated in the at least one bearing 11. In some examples, the lowerthe value of measured reaction torque indicates lowerfrictionaltorque in the at least one bearing 11, and as such lower frictional losses in the bearing system. In this way, relative values of frictional torque can be compared for different bearings under test. In an example where there is more than one bearing support assembly 43 comprising more than one bearing 11, the average frictional torque per bearing 11 (assuming each of the bearings in the system is of the same type) can be calculated (or indicated) by dividing the value of measured reaction torque by the number of bearings in the system 32. For example, consideringthe example of Figure 3, where there are three bearing support assemblies 43, each comprising one bearing 11, the frictional torque generated in each bearing 11 can be calculated by dividing the value of measured reaction torque by three. Using Figure 3 as another example in which there are three bearing support assemblies 46, each comprising a pair of bearings 11a, 11b, the frictional torque generated in each bearing can be calculated by dividing the value of measured reaction torque by six. The present disclosure therefore provides an apparatus 2 and system 32 for testing frictional loss in different bearing types and / or different lubricants coated on different bearings, when the inner race of the bearings are subjected to a radial load and rotational drive force. As presented in this disclosure, bearings in which the inner race rotates in use but the outer race does not rotate, may be tested under a radial load, using an axially loaded rotary test machine and the apparatus 2 shown in Figures 1-9. By testing different bearings and / or different lubricants coating the bearings, using the system disclosed herein, a user may determine which bearings and / or combination of pairs of bearings and / or lubricants generate the lowest frictional torque under a radial load, and using an axially loaded rotary test machine. In this way, it may be determined, in a more economical manner, which bearings and / or lubricants and / or combination thereof can reduce frictional losses in systems that use bearings in which the inner race of the bearing rotates in use but the outer race of the bearing does not rotate in use, and therefore increase the efficiency in systems that use said bearings (e.g., rotating machinery). It will be understood that the foregoing is by way of example only. Also, unless where explicitly stated otherwise, features from different Figures and / or embodiments may be combined. The scope of the invention(s) is defined by the appended claims.

Claims

1. An apparatus for measuringfrictional torque in at least one bearing under test, the apparatus comprising:a main body portion;a hub projecting upwardly from a surface of the main body portion, the hub fixed to the surface of the main body portion such that the hub does not rotate relative to the surface of the main body portion, the main body portion and hub configured to rotate about a longitudinal axis of the hub;a bearingsupportassemblyforsupportinga bearingassembly, the bearing support assembly comprising: a first bearing support portion for engaging with the hub, a second bearing support portion connected to the first bearing support portion and for supporting an outer race of at least one bearing of the bearing assembly and a third bearing support portion for supporting an inner race of the at least one bearing of the bearing assemblya mechanism for (i) applying a radial load to the third bearing support portion in a direction parallel to the longitudinal axis of the hub, and (ii) applying a rotational drive force to the third bearing support portion for causing the inner race of the at least one bearing to rotate about a direction orthogonal to the longitudinal axis of the hub, wherein the second bearing support portion is arranged to hold the outer race still so that the outer race does not rotate whilst the inner race is rotating; andthe main body portion having an engagement portion for engaging with a reaction torque measurement device for measurement of a reaction torque against rotation of the main body portion caused by the rotational drive force applied to the inner race of the at least one bearing, the reaction torque indicative of frictional torque in the at least one bearing.

2. The apparatus of claim 1, wherein the third bearing support portion comprises an outer sleeve portion and an inner sleeve portion, the inner sleeve portion configured to engage with the inner race of the at least one bearing for causing the inner race of the at least one bearing to rotate and the outer sleeve portion is configured to fit over the second bearing support portion such that the outer sleeve portion is separated from the second bearing support portion by a gap.

3. The apparatus of claim 1 or claim 2, wherein the first bearing support portion comprises an inner portion and an outer portion, the inner portion configured to be inserted into a recess in the hub for connecting the bearing support assembly and the hub, and wherein the outer portion extends out of the recess such that the outer portion engages with an outer surface of the hub.

4. The apparatus of any preceding claim, wherein the second bearing support portion is connected to the first bearing support portion via a threaded engagement.

5. The apparatus of any preceding claim, wherein the bearing support assembly is circular in cross section.

6. The apparatus of any preceding claim, further comprising a holding arrangement configured to extend through a center of the at least one bearing and configured to provide an axial load to the at least one bearing, for holding the third bearing support portion to the inner race of the at least one bearing of the bearing assembly.

7. The apparatus of claim 6, wherein the holding arrangement comprises a screw and nut arrangement.

8. The apparatus of claim 7, wherein the holding arrangement comprises at least one spring washer configured to engage with a head of the screw.

9. The apparatus of any preceding claim, wherein the at least one bearing comprises a pair of opposing bearings, and wherein an inner race of each respective bearing of the pair of opposing bearings are separated by a gap.

10. The apparatus of any preceding claim, wherein the engagement portion comprises a torque arm, wherein the torque arm projects outwardly from the main body portion and is arranged to be restrained for rotation by a restraining member.

11. The apparatus of claim 10, wherein the reaction torque measurement device comprises a load cell, the load cell located on the torque arm or the load cell located on the restraining member.

12. Theapparatusof any of claims 1 to 9, wherein the engagement portion comprises an engagement portion located on an underside of the main body portion, wherein the reaction torque measurement device comprises a torque transducer located below the main body portion, the engagement portion configured to engage with the torque transducer.

13. The apparatus of any preceding claim, wherein the main body portion is configured to be connected to a ball thrust bearing of a rotary test machine.

14. The apparatus of any preceding claim, wherein the mechanism is configured to be connected to a rotary test machine.

15. The apparatus of any preceding claim, further comprising an outer casing, the outer casing projecting vertically from the main body portion and surrounding the hub, the bearing support assembly and the bearing assembly.

16. The apparatus of any preceding claim, wherein at least one of the main body portion and the hub are circular in outer profile in plan view.

17. The apparatus of any preceding claim, wherein the hub is configured to support three bearing support assemblies, each respective bearing support assembly of the three bearing support assemblies for supporting a respective bearing assembly.

18. The apparatus of claim 17, wherein the three bearing support assemblies are equally spaced around the hub at an angle of 120 degrees from each other.

19. The apparatus of any preceding claim, wherein a base of the main body portion is configured to receive an axial load from a rotary test machine.

20. The apparatus of any preceding claim, wherein the mechanism comprises a rotatable disc.

21. A system for measuring frictional torque in at least one bearing under test, the system comprising:the apparatus of any of claims 1 to 20; anda rotary test machine, wherein the rotary test machine is configured to be connected to the mechanism of the apparatus, for (i) applying an axial load to the mechanism in a direction parallel to the longitudinal axis of the hub, and (ii) applying a rotational drive force to the mechanism, for causing the inner race of the at least one bearing to be rotated about a direction orthogonal to the longitudinal axis of the hub, wherein the outer race does not rotate whilstthe inner race is rotating.

22. The system of claim 21, wherein the mechanism is connected to a rotating shaft of the rotary test machine.

23. The system of claim 21 or claim 22, wherein the rotary test machine comprises means for providing an axial load to a base of the main body portion of the apparatus.

24. The system of claim 23, wherein the means for providing an axial load to the base of the main body portion of the apparatus comprises at least one of: one or more pneumatic bellows; one or more pneumatic cylinders; a dead-weight; a servomotor; or a spring.

25. The system of any of claims 21 to 24, wherein the rotary test machine further comprises a ball thrust bearing, the ball thrust bearing configured to be connected to the main body portion of the apparatus.T +44(0)30 0300 2000A

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