Combined Roller Bearings and Rails can readily be used in multi stage telescopic applications. Track bearings and rails are commonly used for the telescopic masts of fork lift trucks, but they are equally suited to horizontal applications (for example vehicle pull-outs or furnace lances) and even overhead situations as shown below.
Telescopic arrangements maximise the space available as the system can be designed to fully extended and neatly pack away.
This example shows a two rail system extending with a cantilevered load carried on the forks. Many other configurations are possible and sometimes it can be beneficial to use a four rail system, or a pair of two rail systems working simultaneously.
Our technical sales team have decades of experience and can offer help with configurations and bearing selection. Please do contact us with your enquiry.
Euro-Bearings Ltd specialises in bearings for linear motion and can offer technical support when designing and specify products. With over 40 years’ knowledge of combined roller bearings, you can be sure that you are asking the experts.
How to use Combined Roller Bearings?
Combined Roller Bearings were originally designed for forklift trucks. The assembly consists of two bearings in one, hence “combined”. The radial bearing carries the main load whilst the smaller axial roller resists any side load to help keep the system running true.
A simple horizontal application requires just two special profiled rails and four standard bearings. The bearings can be supplied welded to mounting plates so they can be bolted into place. The combined roller bearings are available from ø52.5mm to ø390mm making them suitable for loads of just ten kilograms right through to tens of tonnes.
More complex applications include vertical, telescopic and cantilevered arrangements, and they can even be used on all 3 axes to make an XYZ machine. See our application examples for inspiration.
How to select the size? Every application is different and it is important to check the loads to ensure the correct bearing is specified. In some instances it makes sense to use more rails or bearings to share the load, for example on a vehicle chassis, rather than simply increasing the size of the bearing.
The critical factor is the Hertzian Pressure which is the point load exerted on the profiled rails by the bearings. This force must be limited to prevent the deformation of the rails. The Hertzian Pressure can be calculated using Moment-Balance. In most instances, simple formulae (given on our website) can be used to calculate the force on the bearings and the size of bearing can be selected from our Hertzian Pressure table.
Our technical sales team can support you with this together with design recommendations.
How to set up the rails? Setting up the system accurately will ensure that the Combined Roller Bearings operate to the best of their ability. Ideally the rails should be absolutely parallel with a clearance between the bearing and rail of 0.3mm to 1.0mm. It is important to test the clearance of the system over the entire length to ensure the axial rollers do not bind in use.
The rails are made from S450J2 steel which is similar to S355 structural steel. The rails can be welded or bolted into place. If it is difficult to set up the system accurately then it can be useful to weld tabs with slotted holes onto the rails to facilitate more accurate adjustment.
Should further adjustment be required, then our eccentric adjustable or shim adjustable bearings can be specified, or the mounting plates can be shimmed from behind.
How to weld the bearings? The combined roller bearings incorporate a weldable hub made from C22E. The unit does not have to be disassembled for welding, but heat from the weld should be kept to a minimum. The hole into which the bearing is fitted should be 50 to 100 microns larger than the diameter of the hub. It is important to ensure the axial roller is orientated correctly before welding the back using a continuous 45º weld fillet. Normal mild steel (non-alloy) welding techniques can be used. Alternatively the bearings can be supplied pre-welded to mounting plates for ease of assembly.
How to set up the adjustable bearings? The eccentric and shim adjustable bearings have adjustable axial rollers to alter the height (h) of the bearings. The eccentric type has a splined shaft which can be finely adjusted to achieve the required clearance. There is a video showing how to do this on our website. The height of the shim adjustable type can be altered by placing shims behind the axial roller. When the final height is achieved, the screws should be thread locked to ensure they are secure.
How to protect the Bearings and Rails? In harsh environments it might be necessary to protect the bearings from rust. This can simply be in the form of shielding or an anti-rust spray, or it may be necessary to coat the bearings to provide corrosion resistance.
The bearings can be supplied with Thin Dense Chromium (TDC) plating which offers a high level of corrosion protection. This is available for all sizes and the mounting plates can be coated too.
The rails can be painted or galvanised to offer protection, but the surface in contact with the bearings must remain bare as the force exerted by the bearings is likely to damage these coatings. The bare steel can be lightly oiled to prevent rust. Alternatively, if full corrosion resistance is required, the rails can be TDC coated over their entire surface.
How to grease and maintain the Bearings? In a dry environment, such as a warehouse, the rails and bearings can be lightly oiled to keep the surfaces free from rust.
The bearings should be inspected and re-lubricated as required every 6 months. The standard bearings (apart from the smallest 4.053 bearing) have a lubrication hole which is plugged with a grub screw.
If the bearings are in continuous use or harsh conditions, they should be checked more frequently.
A grade 3 bearing grease should be used (e.g. Shell Gadus).
How to replace the bearings? Should the bearings need to be replaced, the screws holding the bearing to the weldable hub can be undone and a new bearing slid on. A video on our website shows this procedure. The bearing needs to be square to the hub for ease of assembly.
If the bearing is welded to a mounting plate, the whole bearing and plate unit can be easily replaced. There is a standard range of rectangular and square plates, or alternatively a custom plate can be specified.
How fast can the Combined Roller Bearings travel? The linear speed should less than 1.1m/s for optimum performance. For short intervals and moderate loads, a maximum speed of 1.5m/s is permitted but this may affect the service life.
When to specify Precision (PR) Combined Roller Bearings? The precision bearings offer a tighter tolerance between the bearings and the rails. In most applications the standard bearings will suffice, but in some cantilevered applications it may be preferable to have a tight tolerance to limit the play in the system.
When to specify High Temperature Bearings? The standard combined roller bearings can be used for temperatures of up to 80ºC. When the temperature is continuously above 80ºC, we recommend the use of High Temperature (HT) bearings. The HT bearings can operate in temperatures up to 200ºC.
What is S450J2 Steel? S450J2 is a non-alloy steel that has been developed specifically for use with bearings. The addition of Niobium (Nb) and Vanadium (V) improves both the tensile strength and yield strength which increases the allowable Hertizian Pressure (point load exerted by the bearing).
What seals are used? The majority of the combined roller bearings feature a ZRS seal which is a metal-rubber hybrid seal. The seals help to prevent dust, water and debris from entering the bearing and retain the grease inside.
What are the Benefits of Combined Roller Bearings? There are many benefits to Combined Roller Bearings, with their versatility probably being the main one.
Combined Roller Bearings are used with matching C or I section profiled rails to provide a simple yet versatile linear motion system that can be used in many applications and environments.
The Combined Roller Bearing handles both the axial and radial forces in one unit hence reducing the number of working parts required.
The axial roller runs on the web of the steel to provide lateral guidance. This helps to keep the slide running true and prevents jamming or crabbing.
The bearings and rails can be used horizontally and vertically, and can also be arranged telescopically in both orientations to allow for full extension.
The bearings can be supplied pre-welded to a mounting plate and then simply bolted on for ease of assembly. Alternatively they can be welded directly to the structure for a more compact arrangement.
The system can be used in harsh environments and offers good resistance to dirt. High temperature bearings can be specified.
The Combined Roller Bearings can be coated to provide corrosion resistance.
A precision (PR) version is available for applications requiring higher positional accuracy.
Combined Roller Bearings offer a robust heavy duty linear system at a reasonable price which is easy to set up and maintain.
What applications can Combined Roller Bearings be used for? Typical applications for combined roller bearings include:
Oil drilling and exploration equipment
Marine cable and pipe-laying equipment
Palletisers and packing machines
Goods & vehicle lifts
Material handling equipment
Furnace chargers/dischargers
Concrete and aggregate conveyors
Brick and concrete block making machines
Machine tool positioning and storage
Agricultural equipment
Specialised vehicles and trailers
Theatre and film applications
Medical equipment
Forklift truck attachments
Warehouse automation
A range of application examples are shown on our website including cantilevered, 1 and 2 stage telescopic, and full extension arrangements.
Want to find out more? Or ask another question? Contact our Technical Sales team.
Euro-Bearings Ltd stocks a wide range of linear motion products. We are able to offer a variety of products in stainless steel when corrosion resistance is required. Our technical sales team have many years of expertise and are able to guide you with selecting the best product for your application.
Stainless Steel Linear Bearings and Stainless Steel Shafts:
These linear bearings offer high corrosion resistance due to the special characteristics of martensitic stainless steel. The hardening process leads to an increased service life and a higher load capacity.
The linear bearings are available in closed (KB50) and open (KB53) types along with a range of round flanged versions including FK10 (standard length), FK90 (tandem length) and TF00 (centre flanged).
In addition to this, the SK-n super ball bushings and CLBn compact ball bushings are available with electroless nickel coating to the bush and stainless steel balls. Alternatively the LBBRn is a stainless steel linear bearing with compact design.
The X90CrMoV18 stainless steel shafts are hardened and polished linear bearing shafts, and are available from ø3mm to ø50mm. They can be supplied cut to length or machined to your requirements.
Stainless Steel Linear Guide Rails:
The profiled rail linear guides of the motion guidance systems offer high precision and smooth operation.
All of the Miniature Motion Guidance range (sizes 7 to 20) are made from stainless steel as standard.
The Aluminium Motion Guidance range is also corrosion resistant as the raceways and balls are made from stainless steel. It is available in sizes 15, 20 and 25.
The Track Guidance System can also be supplied as corrosion resistant – the carriages can be supplied with stainless steel bearings and the rails with stainless steel shafts.
Stainless Steel Spline Nuts and Shafts:
The SSP and SPF spline nuts can be supplied in stainless steel with a resin cage, for diameters up to 25mm. The ground spline shaft is available in stainless steel for the corresponding sizes. Other diameters are available with black chrome plating on request.
Stainless Steel Vee Bearings:
When used in conjunction with the Vee rail and Vee bushings, the Vee bearings linear system is suitable for harsh environments with high speed capabilities, medium accuracy and low noise. The Vee bearings, Vee bushes and Vee rails are all available in stainless steel.
Corrosion Resistant Combined Roller Bearings and Rails:
For heavy duty linear motion applications, Euro-Bearings Ltd’s Combined Roller Bearings are often the best solution.
The bearings can be Thin Dense Chromium (TDC) coated to provide corrosion resistance and the rails can either be TDC coated for maximum protection, or galvanised / painted. If the rails are galvanised or painted, the surface of the rail in contact with the bearing must remain free of coating to preventing flaking. The standard combined roller bearings are available from ø52mm to ø149mm, with sizes up to ø390mm in the Jumbo range. The rails are available in C or I sections and are cut to the required length.
The bearings and rails can be configured for vertical, horizontal or cantilevered applications and can be used to make telescopic arrangements too. Example arrangements can be found on our website. This system is particularly tolerant of dirt as the bearings are sealed.
Conclusion:
With a wide range of corrosion resistant linear bearings to choose from, you can be certain to find something suitable for your linear motion application. Our technical sales are always happy to help, so please call or email to discuss.
Euro-Bearings Ltd’s Combined Roller Bearing range offers one of the most versatile linear motion systems.
The combined roller bearing is a unit consisting of two roller bearings assembled on a weldable hub and it is designed to carry both axial and radial loads. The bearings are used in conjunction with special steel profiles (C or I) to form a heavy duty linear sliding system.
The bearings and rails can be used both horizontally and vertically, and can also be arranged telescopically to allow for full extension. The simplest system consists of just four bearings and two rails. Some application examples are shown below.
With the standard range of bearings offering diameters from 52.5mm to 149mm, and the Jumbo range offering sizes up to 390mm, the system is suitable for a wide variety of applications.
The bearings can be supplied pre-welded to a mounting plate which can then simply be bolted on, or they can be welded directly to the structure for a more compact configuration.
Our knowledgeable technical sales team can offer advice on applications, design, corrosion resistance and sizing. Please call or email to discuss your requirements.
Application Examples for Combined Roller Bearings and Profiled Rails:
Our Combined Roller Bearings are designed to be welded into place. But if you want to be able change the bearings quickly then you may want to weld them to a mounting plate. Our standard (rectangular) mounting plates have four threaded holes to bolt into, from the back of the plate. Or you can use the four thru holes to fix from the front of the plate.
3D STEP Files of our range of Radial Bearings can now be downloaded from our website.
Our Radial Bearings are designed to run in our standard steel channels. They can be welded into place. Or they can be welded to a mounting plate and then bolted into place.
In some applications, it is necessary to specify corrosion resistant products (e.g. food, drink & pharmaceuticals) while in other applications it may be desirable but not essential (e.g. offshore, external use). While a few linear motion products are available in stainless steel, there are often high prices, long lead times & lower load capacities associated with specifying stainless steel.
For heavy duty applications there is little choice but some products can be made corrosion resistant by the use of coatings. The most effective coating for linear motion systems is Thin Dense Chromium (TDC). TDC coating provides a hard finish which is able to withstand the high contact load between the bearing and its corresponding track.
Which Products are available?
Euro-Bearings Ltd can offer Combined Roller Bearings with TDC coating to provide a heavy duty corrosion resistant linear motion system. The bearings retain their load capacities (unlike stainless steel alternatives) and maintenance and downtime can be reduced. The TDC coating can also be applied to the rails (channel) and flanged clamps if desired. The combined roller bearings offer a versatile linear motion system which can be used in horizontal, vertical or cantilevered applications.
Another linear motion system to benefit from TDC coating is Vee bearings. While the Vee bearings themselves can be supplied in stainless steel, the T rail to suit the bearings is not so readily available due to the high costs associated with stainless steel. The rails can be TDC coated after any necessary fabrication work and the lead time can be as little as two weeks.
What should I choose?
Every linear motion application should be assessed individually. Use our flow chart to help select which product might be suitable, or ask our technical sales team for advice.
If corrosion resistance is required then consider the following products:
Traditionally, corrosion resistance of linear motion products has been provided in the form of stainless steel. However, today, coatings such as Thin Dense Chromium can provide corrosion resistance to bearings without compromising on load capacities and incurring long lead times.
Euro-Bearings Ltd’s new e-commerce website offering a wide range of products including Anti-Vibration Mounts, Linear Bearings and Linear Housings, Vee Bearings and Vee Rails, and Combined Roller Bearings and their corresponding Steel Profiles.
Linear Motion without noise – Vulkollan coated bearings for use with steel C rails
Are you looking for a quiet linear motion system? Then look no further. Our new Vulkollan coated bearings are designed to run in our steel C channels to make a sliding system that is both smooth and quiet.
Choose from V.053P (52.5mm ø) or V.054P (62.5mm ø). V.054P is also available in stainless steel.
The Oilamid rubbing block can be adjusted – by simply turning a screw – to provide axial guidance and support which helps the system to run true.
