Profile Joints – Part 2
As a person who is regularly building all manner of things using T slot aluminium extrusions, I occasionally come across a situation where a simple joint using a fixing screw just isn’t going to cut it. Today I am going to introduce you to just a few of the many different methods of joining T slot aluminium profiles using items found in the Fixing Accessories section of the Alusic catalogue.
Late last year I was putting together a batch of custom designed workbenches when the owner announced that they wanted an LED light panel mounted about 1200mm above the main work surface of each workbench. No problem, I thought. Just add a pair of upright sections at the back of each workbench, build a frame to hold each panel and attach to the uprights.
That was all fine until it was let slip that some of the workbenches were to be indirectly attached to pieces of equipment that would put some not insignificant vibrations into the workbenches a number of times per day. I quickly realised that the simple jointed cantilever design I’d thought of would likely not cope with the dynamic loads generated by oscillations, caused by vibrating machinery, of the panel and frame on the uprights. Even though that simple jointed cantilever design would be fine with the panel as a static load.
So, a quick design review later. It was decided to use fixing angles (084.305.033) for the main joints and make braces for the uprights using some joint angles (084.305.011).
The fixing angles made the joints very much stronger than they would have been otherwise. Using joint angles to make braces for the uprights stiffened the structure enough to almost eliminate oscillations that would be generated by the vibrating machinery. Thinking about it now, just the braces may have been adequate to keep oscillations, and hence joint loads, down enough for the original simple joint design to cope. Oh well … I think there is a saying in the engineering world that has something to do with “belts and braces”.
A few months after that, the same owner said they wanted some more workbenches (different design of course) also with the LED light panels. This time though, they wanted to be able to adjust the braces up or down a little for operator head clearance.
At first that seemed a bit complex, not to mention costly. A stock of different length braces to be removed and replaced by maintenance people as and when required. I could see there would be no way to guarantee that adequate length braces would not all soon be replaced by the shortest braces, or even removed completely. Not a viable option in my view.
Then the Alusic catalogue came to the rescue. Instead of using a joint angle at the end of each brace and making different size braces it was decided to use a screw swivel joint (084.311.010) at the end of each brace. That would ensure every LED panel support would be adequately braced as well as have a small amount of adjustment using just a hex key.
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