What are suitable applications for thin-section bearings?

Thin-section bearings have proved a favourite with designers of military, aviation and space hardware across both the USA and much of Europe. However, it appears that now, much of the rest of the engineering world is also proving keen to embrace them, something reflected in a recent announcement that Silverthin Bearings will soon be releasing its new multi-lingual catalogue in two additional languages: Mandarin and Portuguese.

Whilst the US-made Silverthin brand has in many cases become the bearing of choice for key contractors in the sectors mentioned, (where failure options are frequently non-existent) the need for maintenance-free, ultra-high precision movement is not restricted entirely to defence, space or aviation applications, as a recent experience has confirmed.

Not long ago, Carter Bearings was approached by a UK manufacturer of precision cinematic mounting hardware and asked to assist in the design of some new, world-class equipment for use by some of the industry's leading names in cinematography. Mark Roberts Motion Control Ltd (MRMC) is a global leader in the field of robotic and motion control systems, providing the hardware and equipment with which great films are made (think Sherlock Holmes, X-Men, The Avengers, Cinderella). The Surrey-based manufacturer was keen to provide film-makers with an all-new series of platforms that used the latest engineering technologies in order to deliver greater freedoms as films were being shot. MRMC equipment is also widely used in outside broadcast, live broadcast and photographic applications, and the range of products it designs and sells includes camera booms, cranes and robotic camera control rigs, two and three-axis motion control systems, as well as camera heads, sliders and controllers.

The business was established more than 40 years ago, and MRMC's Chief Mechanical Designer Ronan Carroll observes: "These days, camera motion control systems such as cranes and rigs need to be as compact, space efficient and lightweight as possible in order to minimise the costs associated with transporting them around the world, from one film location to another. Our customers also demand solutions that are reliable, accurate, repeatable and that provide a steady, vibration-free line-of-sight for the camera at all times. In order to design and manufacture systems such as these, we need to source high precision engineered components for our equipment."

A pivotal engineered component

One pivotal engineered component on an MRMC camera rig is the bearing. As Carroll explains: "For camera rigs, the overall system rigidity or stiffness is critical to provide the camera operator with repeatability in terms of filming a scene. Therefore, when we engineer a camera rig, the elimination of system backlash and the minimising of clearances in the supporting bearings is essential. The rigidity of the system starts with the basic mechanical structure of the rig, but the bearings are absolutely vital to the overall stiffness and accuracy of the complete, fully assembled system."

A specific example of an MRMC camera rig that utilises thin section bearings from Carter Manufacturing is the SFH50, a camera motion control pan-tilt head. This system is a high precision, highly repeatable one that is said to be ideal for virtual studios, virtual reality, animation, time-lapse and web promotional video shooting. The system has an optional 360-degree roll axis, and is compact and lightweight for both location work and between-shoot transportation. MRMC's SFH50 uses Silverthin thin section bearings from Carter Manufacturing to support the circular motion of the camera roll housings. The bearings are supplied as sealed, preloaded (K-Preload) units in 6" and 7" bore diameters.

Carroll continues: "The SFH50 is a super-sensitive piece of equipment and so we require bearings that eliminate camera "rock'. The Silverthin thin section bearings are of the four-point contact X-Type which are preloaded to our precise specification to give us the system rigidity and repeatability that our customers require. We need weather-resistant components, so the thin-section bearings are sealed units, because the camera rigs are used in both outdoor as well as indoor applications. In addition, as the bearings are preloaded, this simplifies and reduces mounting and assembly of the bearings to the rigs."

Other robotic motion control systems from MRMC also utilise Silverthin thin-section bearings from Carter Manufacturing. The "Modula' range of camera motion control rigs from MRMC provides users with very high accuracy and rigidity for filming at very high speeds of movement. This system is capable of providing a wide range of shots at filming speeds in excess of 3m per second, and has the strength to carry heavy payloads, whether it be a full film camera package or a 3D stereoscopic rig. The main pivot on the arm of the Modula is supported by a Silverthin thin-section bearing from Carter. This 2.5" bore diameter four-point contact (angular, radial and moment loads) bearing is preloaded to maintain rigidity and ensure accurate repeatability throughout its entire life.

Carroll concludes: "Carter has been supplying us with thin section bearings for the last five years or so. It's been a mutually beneficial relationship, and deliveries, product quality and technical support from them has always been first class. We therefore look forward to continuing this relationship in the future as we begin to develop even more sophisticated robotic motion control systems for our customers."

Other applications in which thin-section bearings are known to have played an interesting role include one of some gravity, or more accurately zero gravity on the robot arms seen on the outside of NASA space shuttles. The arm, with its associated control mechanisms, is officially known as a Remote Manipulator System and is operated remotely by an astronaut from within the crew compartment. It is both controllable enough and precise enough to place a large satellite within +2 in. and +1 degree of its designated perfect position. In this other-worldly example of thin-section bearing accuracy, lightness and durability, the 50-ft long arm is stated to weigh only 900lb on Earth, with the boom made from a graphite epoxy composite featuring joints of lightweight aluminium alloy. In this application, a thin-section bearing functions as the pivot for what is effectively a "hand' at the end of the arm.

Handy thin-section bearing selector tool

Silverthin and Carter will soon be announcing the arrival of a new facility designed to assist the design engineer in the process of selecting the correct thin-section bearing. The soon-to-be-launched web-based programme is a thin-section bearing selection tool which will be accessible at both the Silverthin and Carter websites. Here, design engineers will be able to input a whole raft of essential criteria such as internal diameters, outside diameters, the preferred thickness of the bearing, the type of design preferred and whether the bearing needs to be open or sealed. Handily, the selector will also include a useful part number cross-reference tool allowing users of other products to upgrade as easily as possible. Immediately adjacent to the selector will be some handy tips on each of the various types of thin-section bearing, together with pointers on which bearing designs are best suited to particular types of application. In the UK, Carter Bearings also offers engineers access to a significant thin-section bearing application knowledge base built from many years of hands-on bearing specification expertise. It was this expertise that Ronan Carroll referred to previously and which other equipment manufacturers have also found useful.

Learn more at www.carterbearings.co.uk.