Articulated Gas Strut DoorsTurning Your Avant-Garde Sign Concepts Into Realities...

I have had upon reflection, only one major life changing episode. This job almost made it to number two...

I was approached by one of my clients, to come up with an idea as to how we could fabricate an illuminated plinth sign, which had a face size of 2500 x 1400, whereby they could regularly change the transparencies.
The sign was to be placed on the bottom tier of a garden bed at the Adelaide Convention Centre, right on the North Terrace entrance. All I had to go on was a drawing as to how it was to look, nothing else.

When I looked at their proposal deeper, I saw that the simple side hinged doors they were wanting, would not work, for two reasons. The first, was because they would possibly catch wind, and break whilst open, and more importantly, how does a person get to the top of the door to change the large transparencies, seeing that the top of the door was to be 3300 above ground level. A ladder wouldn’t do, as it sits in a soft garden bed, and they were quite fussy about the plants being trampled on.

I flippantly suggested to my client, that we could possibly build the sign, whereby the doors articulate downwards, so the transparencies could be changed at ground level... very silly move on my behalf...

They bought the idea, paid my client a massive deposit, and I now had to come up with a system to enable this! They wanted a quick build, and I managed to buy six weeks, which would turn into six weeks of hell.

Well, the fun and games began, let me tell you. The garden bed is actually sitting atop a concrete roof for an underground car park, so deep footings were out of the question, and the Convention Centre was really quite anal about the finished size of the sign, which had to be EXACTLY 4500 high by 1600 wide x 300 deep. I had to fight tooth and nail to get them to allow me to crib the image width down to 1300 from the original 1400 that they wanted, so I could place my mechanical workings along the insides of the sign.

Once they allowed this, I had to magically dream up some sort of double acting door mechanism that would work like I said it would. Absolutely nothing come up on google pertaining to the actions I wanted, so back to the table, and I started to fabricate something akin to what I had in mind at 1:8 scale. Now, imagine if you can, a simple bi-fold door, either on your kitchen, pantry, or patio. They are relatively easy to operate, but sometimes they do go askew. Now, imagine the very same door, but tilted over ninety degrees... you have NO hope of controlling which section will open or close first! The doors on the sign, according to my calculations (which later proved to be correct), weigh sixty two kilograms each, and my own criteria was to have them set, so a small female could operate them with ease, with no danger of a door crashing down, causing injury.

I eventually came up with a very steampunk looking model, duplicating the actions I needed, and I soon found out that things were going to get worse, I needed to have the two actions to have a very definite separation point, so at any given time, only ONE action could work, THEN the other action would cut in, and take over, so in essence, I always had to have one of the actions in lock up mode. Thank goodness I have a mill, and cutting slots to achieve this on the model was a breeze.


I took my model home with me, and set up a large drawing area, and started designing the rest of the sign both from the outside in (to follow the brief), as well as from the inside out (to enable my linkages to fit.

This, is the only job, where I had to do a full set of working drawings, because of the complexity, and also, to send on to the structural engineer for certification. Once the engineers certification came back, I was aghast, he had called for thicker sections inside the sign, allowing me no room for my linkages! Again, back to the negotiating table, and I managed to meet him halfway.

Time was ticking, and new problems were surfacing. There were four sets of linkages to build, and I had to cut them all from 10mm. steel, in house, as well as slot them, bore them for bearings, and work out gas strut pressures. This took an inordinate amount of time, which was quickly eating into my six weeks... I soon learnt that boring under the mill, for the thirty two sealed ball bearing races was the most fiddly job in the whole universe!


The linkages became quite heavy, and complex, and I found I was going to have to use some extremely heavy gas struts, in the order of between 800 Nm - 1200 Nm. Now, the boot of your car may have a strut of say 150 Nm, and they alone are difficult enough to try to compress, let alone hold in the closed position by hand, so, new tool required. I quickly made up a compression tool, to allow me to repeatedly compress, and change out the struts, until I got the balances correct.


Once I managed to get all the linkages finished, I simulated a full scale mockup of half of a door against the wall, and weighted the arm to thirty one kilograms in a linear fashion, so I could work out the correct balance of pressures required, this took two full days, I couldn’t believe it! Anyway, we nailed it, and Louise was easily able to manipulate the arm, repeatedly, with only one hand. This was a major victory, and I was able to relax for the first time in three weeks, but not for long.

I was then informed, that my client could not get a crane on-site, to install the backbone structure, and how can I now make it easy for him to install? I changed the footing details so that all he now had to do, was to place a 400 mm. high section on the concrete, and chemical anchor it into place, then using a clever one-shot hinge system on the posts, two men could easily stand up the posts, then simply bolt the horizontal sections together. The engineer thankfully signed this change off very quickly for us.


As you can see, the one shot hinge is quite simple, and made everyones job on-site a whole lot easier.


This frame, when assembled, weighed a lot, so I had to fabricate a temporary gimbal to hold it at a comfortable working height, as well as being able to fully rotate the job 360º. This was a real back saver!
The next task, was to fit the linkages within the ever decreasing confines I had left, after the Convention Centre and Engineer eroded them away. I kid you not, it came down to two millimetres!
There were a lot of slots I had to hand cut in the 6.0mm. thick posts, to allow the sliding mechanisms to work properly, and with only two millimetres of space, I had no room for adjustment or error.


Once the linkages were in place, I had to fit the respective doors, flush mount the compression latches, and ensure that they registered correctly, before placing dowel pins to keep them in line.


Now I had to clad the beast. Every panel HAD to be free of visible fixings, so a lot of time was taken to sort this aspect out, as it still had to be a bolt and screw together affair.


The skins were a mixture of 2.0mm. and 3.0mm. Aluminium Panels, whilst the edge recessed fins were made with Zincanneal.


From the outset, because of the enormous amount of moving parts, and the overall complexity of the job, I offered to supervise the second stage of installation, once the main frame was set and firm.
This task took me two hours, and all that was left, was for the installers to apply the skins and internal LED array.


Before we started to apply the skins and trims, we had to tweak the doors a little, which only took a few minutes.



This section of North Terrace is the pinnacle for me, to have one of my signs installed here.


I have most definitely arrived! A lot of work, some sleepless nights, but hey, looking back now, it was worth it.


The Convention Centre are now making noises about having another one made...

Articulated Gas Strut Doors For Adelaide Convention Centre Sign, South Australia