Let’s analyze the design considerations for making custom control cable below before you order them for your project.
Cars, machines, and most machines have all their controls near the driver in the cabin or cockpit.
Some control mechanisms transfer signals to the end devices electrically directly or via relays, but the old-school way is via control cables.
At times, you can fail to get the specific control cable you need for your project. In such a case, it is necessary to get a custom control wire made.
Table of Contents
- What Is a Custom Control Cable?
- Types of Custom Control Cables
- Control Cable Sub-Assemblies
- Custom Control-Cable Assembly Design Considerations
- Custom Control Cable Applications
- Wrap Up
What Is a Custom Control Cable?
A control cable is a motion transmission wire that mechanically relays an action or signal from the control point to the endpoint device. Since these cables transmit signals or actions mechanically, they must meet these conditions.
- Deliver precise action
- Be easy to install and unmount in complex, hard-to-reach spaces
- Flexible and easy to recalibrate during their operational lifespan
- Ideal to use in specific application area environmental conditions (cold sub-zero temperatures, oil submerged, under dirt/dust exposure, in corrosive liquids, etc.)
Types of Custom Control Cables
Custom control cables come in two types defined by their mechanical action.
Push-Pull Control Cables
With push-pull control cables, the operator-applied motion is pushing/compressing them in one direction. On the other end, this pushing or compression motion gets transmitted as a pulling or tension force, hence the name “push-pull.”
A parking brake control cable
Pull-Pull Control Cables
Pull-pull cables require a pull operation on the user end and transmit action to the other end via pulling. Therefore, they need operator tensioning/pulling on the user end to create a pulling force on the other end.
Once you let go of the control cable, a mechanical spring actuator returns the core wire to its original position.
Clutch and accelerator control cables
Control Cable Sub-Assemblies
Regardless of whether a push-pull or pull-pull cable, the assembly consists of these three components.
Conduits are the cable housings that safeguard the core cable and provide a dedicated travel path for the wire to transmit the push or pull action from one end to the other.
This dedicated travel path is critical for the cable’s operation because it operates in non-linear motion.
On the protection aspect, conduits safeguard against the ingress of moisture or contaminants that can increase friction along the travel path. Also, they keep the core safe from corrosion and abrasion.
But conduits are not continuous single pieces. They have these three sub-assemblies.
- Outer Jacket: Outer sealant layer that keeps the environmental conditions out
- Wrap: Provides flexibility while adding a secondary protection layer
- Liner: Forms the channel of dedicated travel path for the core
The jacket and liner are usually standard, but the wrap can vary depending on the application. It can have either of these designs.
- Braided form
- Flat wire Bowden (round wire)
- Long lay or reinforced long lay
The cable core is responsible for transmitting action from the user to the opposite end. It travels inside the conduit’s liner and can be solid or stranded.
Solid cores are ideal for transmitting motion in push-pull cables, while the stranded types are suitable for pull-pull wires.
A clutch cable on a motorcycle engine (note the core wire and end fitting)
Core, intermittent transmission, bulkhead, and conduit-end fittings can differ depending on the cable specifications (type, length, and routing path). But they are usually either stainless steel, zinc die-cast pieces, or galvanized steel.
Custom Control-Cable Assembly Design Considerations
Consider these factors if designing custom control cable assemblies for your project.
Limit the Travel Dimensions
Long-distance travel paths cause a lengthy cable to exit either end, generating a lot of friction and reducing the output response.
The long travel can also cause buckling because the core won’t keep the cable rigid. So, keep the distance the inner wire travels inside the conduit’s liner to two inches or less.
Place More Load in the Pull Direction
Most of the working load should be in the pull direction. When using the compression mode, specify this load is 50% max of the pulling force unless the cable has an Armored core.
A choke control lever in a car
We recommend Armored core wires for high-performance control cables because they have higher compression-to-tension ratios.
Consider the Input Load Factor
The input load factor refers to the ratio of the input force needed to operate the control end to the cable’s output force.
The factor is critical when designing push-pull control cables because the lower it is, the smoother the control cable will operate and with a lower risk of fatigue or wear.
You can achieve the optimal input load factor by considering these elements.
- Select the construction materials carefully
- Optimize cable routing and construction
- Reduce friction by keeping factors like the travel distance low
Customize the Fittings
Although control cable fittings are primarily steel or zinc die-cast pieces, you can specify materials for the custom core conduit fittings that best suit your project.
A bicycle’s brake cable
Push-Pull Cable Alignment
The alignment of these cables should be as straight as possible when the core exits the conduit to the device attachment point.
Consider the Loss of Motion
The amount of cable assembly travel usually depends on the number of bends and cable diameter difference between the outer (jacket) and inner (liner) layers. This travel variation is known as motion loss.
Loss of motion in control cables occurs in these two ways.
- Backlash: This motion loss occurs when the core has some play inside the liner when there is a change of motion direction.
- Deflection: Deflection occurs when you don’t anchor the conduit firmly in the installation area.
You can rectify backlash losses in the design process, but deflection prevention is via careful installation.
Avoid Tight Bends (Short Radii)
Avoid complicated cable routing during installation. Use as few turns as possible. Each bend should have a generous radius, especially when using solid core wires.
Stranded cores are more flexible than their solid counterparts, meaning they can handle sharper turns.
Custom Control Cable Applications
- Clutch cable
- Parking brake
- Engine stop
- Throttle cables
- HVAC controls
- Construction Equipment
An airplane’s tail fin with a rudder
Control cables come in different types to mechanically run various parts of vehicles, motorcycles, and other machines.
If you can handle the design process, you can custom-make these cables for almost any project.
Handing the design means implementing the design considerations explained earlier to make the cable durable and efficient.
And speaking of cables, check out this “custom battery cables” article to help you link the power source in your car restoration or building project.