What if my spring drawing does not specify torque?

For a custom power spring, a strip drawing alone may not tell the manufacturer how the finished mechanism should perform. If the torque requirement is missing, the project can still be reviewed. The useful starting point is the motion the spring must create and the space in which it must work.

Describe the mechanism

Tell us what the spring operates: a cord reel, hose reel, cable retractor or another rotating mechanism. A sketch or photo of the complete assembly can show the drum, shaft, housing and spring attachment points. If an existing mechanism is available, a sample can help identify details that are absent from the spring drawing.

Share the working range and load

The number of working turns matters as much as the maximum rotation. State where the mechanism starts, where it finishes and how the load changes across that range. For a reel, useful inputs include the drum diameter, cable or hose length, approximate moving load and the desired behavior at the beginning and end of rewind. If you have measured pull force at the cable or hose, include where and how it was measured.

Confirm the available space

Provide the shaft or arbor diameter, housing dimensions and any limits on spring outside diameter or width. Note the required end connections and assembly direction. These details affect whether a spring can be installed and whether it can operate over the intended turns.

Define the acceptance test

Specify the operating environment, expected number of cycles and the way the finished mechanism will be judged. A single peak torque value may be less useful than a target output at several points in the working range. If you do not have an existing test method, describe what a successful rewind should look like so an appropriate sample evaluation can be discussed.

An initial review can identify missing inputs and a possible design direction. Final torque, material, dimensions and life targets still require project-specific calculation and sample validation. Send the latest drawing or a sample together with the application details above, and identify any requirements that are still estimates.