Reliability
[Home. About Us. Capabilities. Gallery. Contact. Clients & Links]
Reliability and longevity
Clients are often nervous about the reliability of interactives, and have misgivings about having something built by someone who can't be there in an hour to fix it should something go wrong. That's understandable, but it's anticipating problems that should be solved at the design stage.
It's worth taking a look at the general principles underlying the design of machines and which govern their lifespan. Beam engines built in the early stages of the industrial revolution often had extraordinarily long useful lives, up to one hundred years, whereas rocket engines often run for only a few minutes before being discarded. The main principle here is of course redundancy of strength, and the relative power to weight ratios, which indicate the amount of energy that is being transformed within the machine relative to its mass.
With interactives, it's also a matter of avoiding sudden high loadings which can break even a heavily built mechanism. This is why it is best to avoid levers, which amplify torque and often delivery high shock loads at the end of their travel.
We have built a number of extremely reliable mechanisms. Below is the Life Cycle Wheel at Phillip Island Penguin Parade. Since installation in 1997, over three million visitors have passed through the building, and while not every visitor has operated the interactive, it has had hundreds of thousands of users.
The small hand wheel in the bottom right hand corner is turned to rotate the larger wheel containing the graphic image. No matter how hard the hand wheel is spun, it cannot move the larger wheel very fast. Also, the inertia of the hand wheel is low, and the polyurethane belt connecting the two wheels is in contact with the two pulleys for most of its length, so it can't be 'wound up' through its elasticity. All bearings and shafts are massively oversized. This exhibit has never required any repair or servicing.
We didn't always get it right! The interactive below, 'Federation' at the Australian Electoral Commission's education centre in Melbourne, was originally actuated by an electrically driven cable winch which, through a sector plate, operated seven cables which pulled the hinged 'states' together.
The winch's main cable wound onto a fairly small drum, and broke regularly. The winch motor failed after eighteen months, and we replaced it with a linear electric actuator which has no internal cables and has been totally reliable. However, the individual cables to each state have begun failing, and if we built anything like this again, we'd use bell cranks and rods with aircraft type ball joints. Then it would really be bulletproof.
Before and after 'Federation'.
[Home. About Us. Capabilities. Gallery. Contact. Clients & Links]
