SAISC FEATURE to full size to suit the outside diameter of pipe A. This“ wrap around” template would then be used to mark the pipe so that it could be cut such that if the development was correct( and many of them weren’ t) and centred correctly relative to the centreline of the pipe( taking into account perhaps a different development for the other end) when the pipe was cut using hand held oxy fuel cutting torches it would fit neatly to the bigger pipe( s).
After which if all went well the cut would be ground and if necessary prepared for full penetration welds if required. Clearly this really required a skilled artisan to do well, which even in those far gone days there were not many around.
And so with such a laborious and expensive process are you surprised then that“ tubular construction” was not popular.
But engineers and fabricators are resourceful fellows. They quickly realised that by flattening the end of the pipe you could actually eliminate the need for developing the ends and just cut the flattened ends with a saw. This technique was comprehensively written up in the“ Black Book”( The SA Structural Hollow sections handbook) in chapter 7.4. The end result was relatively easier to fabricate but when badly done surely did not look great in architectural applications, one of the reasons why architects chose tubular construction because it looked so elegant!
And then came a great advance when Tekla was able to draw to full size scale the wrap around templates to suit the tube to tube connections. What a pleasure, no more hand drawn developments or specialist companies who offered the service to produce wrap around templates. But even then this was not without its difficulties, especially when it came to centre lining the wrap arounds correctly at each end of the members, and just how to deal with full penetration welds and differing wall thickness of pipes.
But Tekla operators are also resourceful characters. By creating an outer wraparound and an inner wrap( into) around, and if they could be set up correctly on the correct centre lines, then it was just about possible to cut the development and the weld preparations correctly. So this became a double exercise requiring an extraordinarily capable artisan to do well.
But I am pleased to say that this is now all history.
What with the advent of 6 axis tube laser cutting machines, which communicate directly with Tekla and other computer packages in one station it is now possible to cut the development and weld preparation in that station. In addition, with clever detailing and understanding of the process slots can be cut into the primary pipe in exactly the right position for a tab cut on the end of the secondary pipe that needs to join the primary pipe resulting in a perfect fit without having to do a layout in the assembly bay.
Once again Spencer bemoans his age and not being able to directly experience the wonders of modern technology.
Partially flattened end
OPPOSITE PAGE BELOW: Figures 1 and 2. Source: www. thedraughtingacademy. co. za
TOP LEFT AND RIGHT: Examples of developed pipe to pipe connections. Source: http:// www. tboake. com / steel / waiward. html
CENTRE AND BELOW RIGHT: Figures 3 and 4 – Jig pressed ends for geodesic roof look just great if done properly. Source: http:// 45.79.160.8 / dome-basics / geodesic-domehub-connectors /
Steel Construction Vol. 40 No. 2 2016 19