Cable carrier support roller: when and how

Supporting a cable carrier with a support roller works when the travel length is just too long to be self-supporting and a guide channel is not an option. The roller is fixed to the machine and catches the upper run of the cable carrier before it starts to sag. That way the same type reaches a longer travel length. There are clear limits, though: the travel length, the position of the roller and the speed are fixed. Below you can read when a support roller works, how to position it and when another type is the better choice.

When does a cable carrier need support?

In a self-supporting arrangement, the upper run of the carrier hangs freely above the lower run. How far that upper run can carry itself is called the self-supporting length Lf. It is given per type in the load diagram of the catalogue and depends on the additional load: the weight of the cables and hoses per metre of carrier.

With the fixed point in the middle of the travel length, the rule is: the maximum travel length is twice Lf. If the fixed point is at the end, the travel length is at most once Lf. If the travel length gets longer, the upper run starts to sag. With a plastic carrier, a little sag is technically permitted, but we advise against it because it causes wear and unsteady running. With a steel carrier, sag is in principle not permitted. You can read more about the causes in cable carrier sag.

If the travel length is too long for Lf, you have three routes:

• A larger type with a greater self-supporting length.
• Support with a support roller or support bracket under the upper run.
• Gliding in a guide channel, with the upper run resting on the lower run.

You can read how to weigh self-supporting against gliding in self-supporting or gliding. This article is about the middle route.

How does a support roller under a cable carrier work?

A support roller is a freely rotating roller on a fixed support, below the path of the upper run. When the driver moves away from the fixed point, the upper run rolls over the roller. The roller takes over part of the weight, so the section that has to be self-supporting becomes shorter.

There are three variants:

• Support roller: a roller under the upper run. The usual choice for steel carriers.
• Support bracket: a fixed support over which the carrier glides. With a plastic carrier always with a lead-in chamfer, so the links do not strike against it.
• Side rollers: rollers that catch the carrier at the side, for situations with no room under the carrier.

Support is only of limited use with plastic carriers. A plastic carrier bends more easily between two support points, so it still runs unsteadily. Support is mainly a solution for steel carriers.

How long can the travel length be with a support roller?

The Tsubaki Kabelschlepp catalogue gives two limits, expressed in the travel length LS and the self-supporting length Lf:

Two conditions apply. With a support roller, preferably calculate with only 80% of the Lf from the load diagram. And the travel speed is 1 m/s at most. A support roller is therefore a solution for calm movements, such as a crane trolley, an operator carriage or a slow gantry axis. It is not suitable for a fast axis with high acceleration.

A second roller gains less than the first. From no roller to one, the travel length rises from two to three times Lf; from one to two rollers, from three to four times. The catalogue does not mention more than two rollers.

Worked example: a steel cable carrier over 11 metres

An operator carriage travels 11 m at a speed below 1 m/s. The cable package weighs 8.6 kg per metre. An S/SX S/SX0950 fits in the installation space. You can read how to determine the weight of your package in laying out a cable carrier: fill level and additional load.

According to the load diagram, the S/SX0950 may span 4.16 m unsupported at 8.6 kg/m. That gives these results, with the fixed point in the middle:

So it works with two support rollers. The first roller goes at 300 mm from the fixed point, the second at 11,000 / 4 − 150 = 2600 mm.

Now look at the next size up. At an additional load of 10.25 kg/m, the S/SX1250 may already span 6.36 m unsupported, and slightly more at 8.6 kg/m. Self-supporting, it therefore reaches well over 12.7 m of travel length. That is enough for 11 m, without rollers, without a speed limit of 1 m/s and without extra supports that you have to align and maintain. That is why the catalogue advises: preferably choose the next larger series if the installation space allows it.

Support roller or larger series: which do you choose?

A support roller is mainly a solution for existing machines and tight installation spaces. We see it in three situations:

1. (01)The installation height is used up. A larger series has a greater outer height and does not fit under the machine.
2. (02)The travel length is extended. In a retrofit a track gets longer, and the existing carrier has to stay. One or two rollers are then installed faster than a new carrier with different end connectors.
3. (03)A channel does not fit. A gliding arrangement needs a guide channel over the entire travel length. Space, the floor or the costs can make that difficult.

For a new machine, a larger series is almost always better. There are no extra parts that need to be aligned, and you are not tied to 1 m/s. If the larger series is not enough either, a gliding carrier in a channel is the usual step for long travel lengths. What to look out for is explained in cable carrier long travel length and guide channel for your cable carrier.

The position of the fixed point matters too. If it is at the end of the travel length, the self-supporting travel length is halved, with or without a roller. You often gain more by moving the fixed point to the middle. How that works out is explained in fixed point of a cable carrier: where do you place it?.

What should you look out for when installing a support roller?

A support roller only works if it is positioned correctly. Pay attention to these points:

• Height: the top of the roller is at the height of the upper run when it runs straight. Too high pushes the carrier up, too low does nothing.
• In line: the roller is square to the direction of travel and centred under the carrier, so it does not pull to one side.
• Width: the roller is at least as wide as the carrier, so the links are supported on both sides.
• Position: use the distances from the table and measure them from the fixed point.
• Inspection: include the roller in your maintenance. A roller that seizes wears through the links.

A support roller does not change the length of the carrier. You calculate it as always from the travel length, the bending radius and the pitch, for example with calculate the length of your cable carrier.

Rather have it checked?

The Cable carrier configurator checks, for your travel length and cable package, whether a type can be self-supporting, based on the load diagram. If the travel length falls just outside that limit, we calculate along with you free of charge: a larger type, a support roller or a gliding arrangement. Send us the travel length, the speed, the cable package and the space available in the machine via a quote request. Wisman Techniek can supply the carrier complete with cables, assembled in our workshop in Ruurlo.

ProductSteel cable carriersSteel and stainless steel cable carriers from Tsubaki Kabelschlepp (LS/LSX, S/SX, S/SX Tubes). For heavy and long applications, supplied and assembled by Wisman Techniek.View the product

Frequently asked questions

When does a cable carrier need a support roller?

When the travel length is longer than the carrier can handle self-supporting and a larger type or a guide channel does not fit. With the fixed point in the middle, that is the case when the travel length is longer than twice the self-supporting length Lf from the load diagram.

How much longer does the travel length get with a support roller?

With one support roller, the travel length may be up to three times Lf, with two support rollers up to four times Lf. Use 80% of the Lf from the diagram in your calculation.

Where do you place the support roller of a cable carrier?

With one roller at one sixth of the travel length from the fixed point. With two rollers, the first at 300 mm and the second at a quarter of the travel length minus 150 mm, also measured from the fixed point.

How fast may a cable carrier with a support roller travel?

At most 1 m/s. For faster movements, choose a larger type or a gliding arrangement in a guide channel.

Can I support a plastic cable carrier?

To a limited extent. A plastic carrier bends more easily between the support points. If you do use a support bracket, always with a lead-in chamfer. A larger type or a gliding arrangement is usually the better solution.

Series on this topic

S/SXVery robust steel cable carrier