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The Perfect Fill Ratio for Cable Blowing.

The Perfect Fill Ratio for Cable Blowing.

Fibre optic cable blowing isn’t a new technique for cable installation and, in fact, it has been in use since the late 1990’s. However, the cable blowing technique may be new to some installers. A range of CBS cable and fibre blowing machines  help get the job done with ease for both the seasoned installer or the novice. In this article, we discuss one of the key parameters to a successful installation, the fill ratio.

The Fill Ratio

The fill ratio can be calculated for a single fibre optic cable installed in an innerduct or microduct as: d2 ÷ D< 65%


d2  < 65%

The lowercase “d” stands for the outer diameter of the cable, while the uppercase “D” stands for innerduct’s inside diameter.

This means that when the cable outer diameter squared is divided by the innerduct inside diameter squared, the outcome should be less than 65% (or .65) for the most effective cable blowing. Also, the fill ratio should not fall below 35%, as the cable may have more of a tendency to “kink” in the innerduct due to excessive turbulence. Likewise, when the fill ratio is greater than 80% it becomes increasingly likely that there is insufficient space around the cable for the viscous drag principle of the air to act on the cable jacket.

The fill ratio is one of the parameters determining how far a fibre cable can be blown. A larger fill ratio is preferred when the cables are relatively stiff and the duct run is straight. A smaller fill ratio is typically preferred when there are multiple bends in the duct run, allowing more room in the innerduct for the cable to navigate the route.

The installer doesn’t specify the innerduct or the cable, but the installer can easily calculate the fill ratio and determine if the ratio is in the “sweet spot” or not. A fill ratio out of range may explain why the cable installation didn’t proceed as planned.

CBS Airstream

CBS Airstream

The AirStream Cable Blowing Machine is powered by the newest servo control technology making it a top-tier cable placement tool. This powerful, single operator machine is easily operated to allow for safe and easy cable threading. Highly reliable and requiring little maintenance the AirStream Cable Blowing Machine is suited to reach a wide selection of cables ranging from diameters of 2.5mm to 11mm to make a wide array of jobs easy to complete. 

This machine features a tabletop design giving it such user-friendly ergonomics. It also comes with variable torque and speed controls allowing you to adapt to what each job requires. And it engages a double belt drive that is powered by the latest servo technology giving the machine precise torque and speed controls to suit each job. Digital monitors allow for simple monitor readings of the cable speed and length, while an auto-stop facility can be employed with air stone fitting.  

An integral air valve and pressure gauge make cable threading easy. The AirStream is lightweight and compact making it able to be used in both outdoor and indoor work environments. It is a low maintenance machine that emits low noise levels making it a tool users will want to work with. The machine also comes with a polycarbonate safety guarding and a travel case for simple transportation. 

The AirStream Cable Blowing Machine was designed to make all jobs easy to complete for users.

CBS Tornado Cable Blowing Machine

CBS Tornado Cable Blowing Machine

CBS Tornado Cable Blowing Machine

We are the only company here in the UK that manufacture and sell our own range of cable blowing machines, the largest of which is the Tornado. This machine has been designed to to provide a safe and effective method of installing cables ranging from 6-32mm (0.25-1.25″) into a pre-installed duct. The Tornado is fast and will install the cable at a speed of 90m/min (300 ft/min) to maximise job efficiency.

An aluminium air box and cable pusher are the backbones allowing the Tornado Cable Blowing Machine to install the cable with or without an existing missile. While the machine is operating, hydraulically powered caterpillar belts controls the way the fibre optic cables are driven into the air ducts. An electronic monitoring system generates read-outs of the speed and distance of the cable, while also protecting the cable from any obstructions that may arise and being able to facilitate an emergency stop. 

The machine sits on a lightweight tubular-steel frame able to be tilted at a 30-degree angle to reach manholes, bending and strain on the wires are significantly reduced with this feature of the machine. The height of the frame is also adjustable so the entire machine is easy to maneouver and able to adjust to any terrain.

CBS Drum Handling Equipment

CBS Drum Handling Equipment

CBS Drum Stands & Drum Trailers

Designed to make your life on site easier our range of drum trailers and stands offer robust and reliable solutions to a wide range of tasks, from trailers for transporting larger drums to the work site or stands of various sizes for smaller drums.

C-751 Drum Trailer

The C-751 Drum Trailer has been designed to be a compact and manoeuverable drum trailer, capable of handling cable drums from 1800mm to 2185mm in diameter and a maximum drum weight of 1000kg to 1630kg. Manufactured in strong steel sections, it incorporates manually operated hydraulic lifting of drums. There is also an optional drum braking arrangement, this is particularly useful when pulling the conductor during conductor stringing operations. Trailer braking is of the over-run type and is supplied to EC specification. All versions are IVA approved.

C-1290 Triple Braked Drum Trailer

The C-1290 Triple Braked Drum Trailer is a uniquely versatile tool, a single operator can independently control the tension of all three conductors. Ideally suited to the needs of cost conscious installation crews who require fast turnarounds and maximum productivity. Supplied with a full set of detachable stabilisers to maximise trailer stability during tensioning. Fitted with smooth operating disk brake for conductor control. 

D-684 Braked Drum Stand

The CBS D-684 drum stand is compact in size and is available in up to either 2 or 4 tonne capacity. Each side is fitted with wheels to allow for easy transportation. Drum lifting is achieved with two hand operated hydraulic jacks. An adjustable band brake provides safe, controlled cable tensioning.

D-711 Braked Drum Stand

The CBS D-711 Braked Drum Stand has been designed in sections for ease of transportation and is simple to assemble without instructions. Accommodates drum weights of up to 1500kg. The stands incorporate a band brake to provide safe and smooth cable tensioning. Two hydraulic pumps provide drum lifting to the desired working height.

D-1156-01 Cable Drum Stand

The D-1156-01 Drum Stand has been designed in sections for ease of transportation and simply slots together to form a rigid and stable drum stand. Accommodates drum weights of up to 500kg. The shaft is fitted with bearings and drum location collars are also included. Two hydraulic jacks provide drum lifting.

Roll on Drum Stands

D-496-01 Roll on Drum Stand allows a range of drums up to 1500kg in weight to be accommodated to suit the majority of applications. Manufactured in steel, with ball bearings in the rollers, the stand is suitable for pulling off cable from the drum.

The D-998 is manufactured in steel, with sleeved bearings in the rollers, this portable lightweight unit is particularly suitable for small to medium drum sizes of up to 500kg.

Drum Jacks

The CBS range of cable drum jacks are maunfactured in a sturdy steel construction with heavy duty Acme screw threads to provide safe lifting. Available in 3 different sizes to accommodate up to 3, 6 or 8 tonne capacity – 2 x stands required – with a variety of spindles available to suit different drum sizes. Jack steady bases are also available to provide extra stability.

D-536 Hydraulic Drum Jacks, which are lightweight and almost indispensable for use in the cable yard. Versatile and easily adjustable within seconds to accommodate a vast range of drums. Excellent all-round stability, fitted with wheels to be easily moved by one person. Complete with spindle and collars. Available in 3 different sizes to accommodate up to 3, 6 or 10 tonne capacity.

CBS Cable Blowing Machines

CBS Cable Blowing Machines

CBS Range of Cable and Fibre blowing machines.

Our range of specialist blowing machines offer the fastest and most reliable method of installing cable and fibre into tubes and ducts. From our highly versatile Tornado, which can fulfill any cable blowing need from 6-32mm and has proven itself around the world, to the AccelAir2, which is our most compact unit and offers a portable solution for all smaller fibre blowing requirements.

C-1250 Tornado

The Tornado is the largest and most powerful in our range of cable blowing machines and has been designed to be a safe and effective method of installing cables from 6-32mm into ducts ranging from 25-63mm o/d. It’s sturdy design and ease of use means that is has proven highly successful, not just in the UK, but all over the world including Europe, Africa and the USA, where it can withstand even the most extreme climate and terrain. The system is driven by a hydraulic petrol powerpack, whist compressed air feeds the cable through with the aid of the hydraulically powered drive belts, which provide maximum cable protection.

C-1900 Jetstream

The Jetstream is one of our newer machines, having gone into production in 2014 after successful trails with our agent in Belgium. The unit is built with maximum cable protection in mind thanks to its double belt drive system, which installs cables ranging from 4-20mm into duct diameters 12-50mm. Power by a 32cc hydraulic motor, the JetStream offers high performance and reliability. The Jetstream has proved highly successful both in the UK and Europe, and more recently in the Middle East where it was more than capable of coping with the extreme conditions. Supplied with it’s own carry case the JetStream is easy to transfer between jobs and can be fitted with an optional Inlet and layflat hose which is smaller and lighter – taking up less room and making it easier to use.

C-1700 Airstream

Using a compliant, double belt drive system, which provides maximum cable protection, the AirStream is trusted by installers for fast and efficient installations. Table-top design and single person operation with safe, easy to operate ergonomic controls combines with low maintenance and high reliability to form the machine’s key features. The unit is adjustable to suit cable ranges from 2.5-11mm installed into tube sizes of 5-18mm. It has proven most popular in the UK and European markets, with the equally reliable pneumatic version also available.

C-1800 AccelAir2

The smallest in our range of blowing machines, the AccelAir2 offers a compact and simple but reliable method of installing even the smallest of fibres of up to 3mm into tubes up to 10mm diameter. Sophisticated buckle protection prevents damage to smaller fibres up to 1.6mm, enabling the unit to install at speeds of up 100m/min. The unit comes with its own handheld carrycase with storage for the remote, spare battery and required accessories therefore enabling easy transportation and storage. Mostly popular within the UK and European markets with technicians installing fibre to the home.

CBS in Saudi Arabia

CBS in Saudi Arabia

June 2019: 

Pictured above, Sales Manager James Shaw with our agent who cover Saudi Arabia and Dubai, Elfit Arabia. Over a 4 day visit, starting in the capital Riyadh, James worked with Elfit and some of their customers in various areas of the country to cover extensive training on the running and maintenance of their recently purchased Jetstream Cable Blowing Machines. The visit also included a conference where James was able to speak futher to the Elfit sales team about the benefits of buying from CBS. Until recently the Jetsream had not been tested extensively in the Middle East so this provided CBS with an excellent opportunity to see how the machine copes under such extreme conditions of heat and dust. The visit proved successful, with both Elfit and their customers impressed with the machines performance and ease of operation.

Oakham School Students win Innovation Award

Oakham School Students win Innovation Award

A group of students from Oakham School have a won a prestigous ‘Innovation Award’ after working with our design team on improvements to the Airstream Cable Blowing Machine as part of the Engineering in Education Scheme (EES). The team of 5 students, pictured with Technical Manager Andy Sibun, Managing Director Robert Davidison and Mechanical Design Engineer Arron Graham, were tasked with improving the already reliable Airstream after MD Robert, who had previously heard about the scheme, contacted the school offering them the chance to work on a project with CBS. The School has a long history of working with local engineering firms to take part in the scheme, which specifically challenges students to work with an engineering company to solve a real-world problem, and CBS would be keen to work with the school again on future projects.  To read more click on the link below.



CBS Portable Duct Rod Pusher

CBS Portable Duct Rod Pusher

The Portable Duct Rod Pusher is designed to assist with rodding operations and makes placing pulling lines or fibre cables into old or occupied conduits that much easier—even with fewer personnel.

Designed specifically to work well with our durable and high-performing 14mm Duct Rod (sold separately), the hydraulically powered Duct Rod Pusher powers the Duct Rod into and out of conduits, pushing and pulling with forces of up to 220kgs at 60bar. The Pusher is able to reach rod speeds of up to 30 metres per minute, when used with the C-1203-F Powerpack, and uses a totalising counter to keep accurate measurements of distance. Each unit is fitted with an extendable tilting boom, reducing the initial bending and potential damage of the Duct Rod, and chamber clamp for stability during underground use.

CBS Pneumatic Airstream Cable Blowing Machine – Where ease and efficiency combine

CBS Pneumatic Airstream Cable Blowing Machine – Where ease and efficiency combine

Compliant, double belt drive configured blowing machine, the CBS Pneumatic AirStream is trusted by installers for fast and efficient installations in the world of fibre to the home networks.

Compressed air is required for cable blowing which also powers the AirStream’s pneumatic motor, making the CBS AirStream a versatile choice that doesn’t require an external power source. Designed around a tabletop design, the AirStream is ergonomic and comfortable for using with a variety of microduct and microfibre combinations. Easy to use speed and torque controls, and an electronic display of speed or distance, the AirStream is the perfect choice to provide your team the tool they need to get the job done.

Robust construction, high reliability, and a low maintenance requirement helps to keep the AirStream and your team productive throughout the day, week in, week out which is why it’s trusted by the leading fibre installation companies.


CBS GentL Air Cable Blowing Machine – Practical and Safe

CBS GentL Air Cable Blowing Machine – Practical and Safe

Built to safely and efficiently install blown fibre into microducts using a battery operated drill and compressed air, the CBS GentL Air Blowing Machine is a portable and affordable solution that still offers a powerful array of features.

Designed around 1-3mm diameter cables in duct sizes of 4-7mm, the GentL Air is ideal for installing today’s popular small size fibre optic cables. These small cables can be delicate which is why the GentL Air is designed to put as little stress on them as possible. Supplied with a built-in clutch mechanism, the GentL Air protects the cables during installation and is fully adjustable so you can find the right settings for optimised blowing.

We recommend using a crash test to determine the clutch settings before blowing – simply take a piece of duct, put a cap on the end and run fibre into the duct until it hits the dead end. Start the test at a low clutch setting, increasing over time to find the optimal setting without over pushing the cable.

Due to its compact natural and external power source, the GentL Air is easy to transport between jobs and is supplied with a travel bag. Optional accessories include a tripod mount, and a drill stand for sturdy placement while blowing helping to make using the GentL Air Blowing Machine easier than ever.