Since it was invented, there have been countless iterations but ultimately it remains largely the same.
The search for 'better' doesn't always mean different either, but sometimes different can be better. Bigger isn't always best and what is actually best is always subjective. So when we were approached to re-design a multi-message sign frame leg, we thought "how are we going make a better wheel?!".
The impetus for change (like with many things) came about from a general feeling of need. The trusty old Y leg used to stand multi message frames hasn't seen much change for about 3 decades. Yes we have seen all sorts of updates including hinged versions, larger versions and of course, new pretty colours and the infamous T leg that posed more questions than the problems it solved.
Many of these changes have address usability and storage issues, however none have really tackled the issue of improving the primary function of the leg; to keep the sign standing up in forever changing conditions.
The go to mitigation for strong winds is to simply throw on more sandbags. A sensible, practical approach I'll grant you. But at 7-10Kg each, how many can one fully stocked sign ute carry?
The challenge was thrown out to the industry body by a state government: A MMS leg solution was needed with universal application to make lost messaging through blown over signs an issue of the past.
Back to the drawing board we went. Working out the compliance requirements, expected environmental conditions, the force and load requirements and certainly, the handling and stowage needs of the user. Engaging with people much smarter than myself, we mapped all of these requirements, created a 'nice to have' list and then went about understanding the relationship between a multi message sign and a B double at 100 KPH in close proximity, with the help of a mechanical engineer mate of mine.
Frankly, the numbers were staggering! The amount of force applied to a 1.08 sq meter, flat, thin surface in the wake of a B double passing was unexpected. Add in the complexities of low pressure air systems and we came to realise a traditional leg had little chance of holding up a important road safety signage, regardless of the number of sandbags you put on it.
Give me a lever long enough and a fulcrum on which to place it, and I shall move the world.
Archimedes
So back to Mr Little's year 11 physics class I trudged. Once we understood the forces, the application and the major variables and then what they all meant, we had a good idea of what we needed to do.
What ensued was copious amounts of modelling and experimenting, product research for ballast and materials, estimating mass and build times, practicalities of use and stowage with the 400 versions of a TC sign ute rack out there (something I can't wrap my head around but will be the topic of a post for another day). The next few weeks were a mess of welding and grinding, experiments and load testing. Balancing the minimal amount of ballast to add maximum leverage to the structure.
Thus the Gravity Anchor was born!
After a long testing time we realised that we may have over done it... That the rigidity of the structure that the arms provided were in fact not allowing flex of the sign, in effect, maximising the wind load applied to it. So Like all good designers, we start with a design and then start peeling the useless parts off it. with a 1.44 sq meter footprint, the device wasn't small, but we were able to make it foldable and about 30mm thick. We managed to nail a 1kg frame mass and tick all the compliance boxes, making it mechanically simple and durable and essentially creating a 1400% better performing sign leg compared to the budget Y leg versions in a B-Double frequented, high speed, regional area.
What did we learn?
We confirmed that better is not best.
We realised there is a lot more to fluid dynamics than any of us thought.
We learned that it can be done - better can be better without loosing out on something else that's not part of the main goal.
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