Cable Tray Threaded Rod Calculation

Although the chosen tray specification is well beyond the application safety requirement, the customer may have have some cost constraints and limitations that need to be factored in and considered..

I wouldn't think you'd go below M8 rod for practical reasons, but without knowing the details of the job, it seems a bit odd to hang the trays on 2m of threaded rod.

I concur as you noted without knowing the details of the job, it seems a bit odd to hang the trays on 2m of threaded rod.

Universally in the US trays are hung with 1/2” threaded rod. Anything smaller is tough to work with, tools, handling, storage. My sympathy for you working with a client who wants you to justify threaded rod cost hanging cable tray. 2 meters of hanging is not that unusual, I would be concerned that 1/4” rod would give you very poor lateral stability. When the guys start pulling wire in the tray, that’s when those spindly M8 rods are going to be a problem.

Agree, I thought lateral stability could be a problem, but without more detail...........

See attached B-LINE recommended threaded rod for cable trays

See:

https://www.eaton.com/us/en-us/products/support-systems/cable-tray-and-ladder-systems.html

Consulting the Eaton data as suggested in post#8 is good engineering!

It has to last 30 years despite corrosion [plating quality??]. Experience matters.

In practice, it is more likely a nut will fail [stripped thread] than a rod break- calculations on area of rod given by one post are misleading - shear strength is lower than tensile. How strong is the fastening to the ceiling/wall?? - they are less predictable than a rod/washer nut etc. which are testable.

Here’s the rough breakdown I followed: the load per rod is about 12.775 kg, so if you convert that to Newtons (just multiply by 9.81), you get around 125N per rod. The 8mm rod I used had a yield strength of 475.63 N/mm², which was more than enough when you factor in its cross-sectional area, around 36.6mm² for M8.

As long as your load per rod doesn’t push that limit, you should be safe. If you’re looking for more specs or want some options, I found tecnotools.com.au to be a pretty handy source for cable tray supports.