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