I have a job at the moment to build a structure that will allow a four footed gazebo to spin on a stage which I can't fix to. I quite enjoy challenges like this especially when they are required to be built with regard to keeping costs minimal. Not having access to an excess of funds makes one disregard the obvious solutions and dig deeper to find answers that make use of a minimum of resources for a maximum return in usefulness.
So I suppose firstly I have to illustrate what I'm trying to achieve and what I have to achieve it with. The structure is a gazebo with four legs that holds up a circular "roof" and it is made of light gauge painted mild steel tubing. The four legs are about 400mm wide and about 15mm deep, the width of the tubing, and stand at 90 degrees to each other along a circumference of about 2.06 metres. This structure then needs to rotate around a fixed centre as the stage it is on is of a limited size and to make things difficult I can't affix anything to the stage.
The person I'm working for has a person qualified as a stage designer who has offered a solution but this solution though somewhat workable requires what I define as excessive materials and is somewhat problematic to use as required. The solution is to build a circular platform and put fixed wheels on it. What this means is that the circular platform needs to be built in one piece and hold up any weight applied to the stage only at it's outside edges as the wheels would be fixed at the edges. This means that to remain as thin as is possible the structure would either have a frame made in steel tubing with a thin plywood top or a thicker plywood of about 30mm so that any weight on its centre area wouldn't have the whole thing sagging. Also if four, five or six wheels (or even eight) are fixed on the outer perimeter then it would seem that it would rotate and each wheel follow the next in an orderly fashion but chances are that, with the impetus to spin applied from the outside, it would skitter somewhat and slowly move other than required... it would crawl unless the applied force to spin were exact and given that the nature of it's use requires that it spins when force is applied from within then the solution begs modification.
My own solution will work because when I was out getting my gas bottles I found a place that makes cast concrete garden slabs and found four rings of concrete, for putting around plants, in the refuse bin and was allowed to take them home. Initially I grabbed them as pieces to put in a wall but once I was building the stage I realised they where, well one of them was, exactly what I needed as a weighted centre. So what I'm saying is that serendipity played a part in supporting my solution so therefore it needs to happen.
Basically I use the concrete ring as a fixed centre, I'm going to add more concrete to the inside of the ring, and a stage of sorts goes around this and provides, at its outer edge, a bearing race for wheels on an outer ring, which the gazebo is affixed to and also has wheels that allow it to move ( so two sets of wheels on the ring; one set horizontal and the other set vertical) around the perimeter. Fairly complicated to explain but the gist of it is that the centre fixed stage can be made light weight, the wooden part, as it sits on the stage and is held by the weighted concrete ring, and the performer can stand on this and apply even force to the gazebo to make it rotate. The ring that holds the gazebo in place has one set of wheels, one under each gazebo legs so no weight offsets, vertically orientated that ride on the floor that allow it to rotate and another set of wheels, horizontally set, that ride around the perimeter of the circular fixed stage. By isolating the functions of load bearing and rotating then the ring and stage can be made light weight.
T his has to work basically because I've materials on hand that I found which packing crate plywood at about 10mm thick and a load of pine boards at 12 mm thick and 200mm wide as well as some 100mm x 35mm Baltic pine... all actually sourced from packing crates... plus a scavenged concrete ring. So these materials are actually more than suitable for the "stage" has to be light and loads distributed effectively to ensure the least amount of stresses on individual requirements. Isn't that a good plan for life as well.. walk and move lightly and only press as hard as the task requires... so stresses are minimised for all.
In ending I'd just like to say that this is about the idea of being resoureful. Not just buying new materials but taking the time to review whats availablethat would otherwise be burnt or tipped because the materials use is defined not only by what they have already been used for but also that idea of defining it's no longer useful renders them useless. It's called looking outside the square but over time that square has become a pinhead, things being as narrowly defined as they are now, so it's now "get off the pinhead"
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