Automating Sliding Gates on a Slope
The issue of installing automatic sliding gates on slopes has come up over the years and has been the subject of much debate. It concerns gates mounted on two wheels that run along a track fixed to the ground that are opened and closed by a sliding gate motor.
Many years ago, installers were told by manufacturers of gate automation equipment that an incline of up to 4% was acceptable for sliding gates. That gives a height change of 4 cm for every metre of track. With a typical 6 m track length, that means a total height change of 24 cm.
Anyone who has ever done basic physics or has ridden a bike will know that things with wheels are pulled down slopes by gravity. And on a slope, a sliding gate is exactly the same, requiring energy from the gate motor simply to stay in one position. Once it is moving downhill it will require substantially more force from the gate motor to bring it to a stop. And to start a stationary gate rolling uphill takes considerably more force than it would do on a level track.
Sliding gate motors are designed to move an automated gate backwards and forwards and stop it on level ground. They are not built to cope with the completely different forces at work when either driving automatic gates up hill or controlling them as they descend.
The different forces involved when operating a sliding gate motor on a slope will also affect its operation and there are likely to be difficulties even in setting it up. Also, without clever electronics, this type of use is likely to lead to rapid problems with mechanical elements such as gearboxes that bear larger forces than their original design specified.
The suggestion that sliding gates could be automated on sloping ground was made prior to the more recent tragedies caused by automatic gates. These have illustrated how a badly designed and installed automatic sliding gate produces incredible shearing forces and consequently acts as a horizontal guillotine.
Today, we have additional safety devices such as safety edges and obstacle detection that is built into the gate motor or control panel electronics. However, gate safety features are only as good as the engineer designing and installing a safe automatic gate system.
Now gate automation manufacturers that recommend their equipment for use with gates on a slope of any kind are hard to find. Even with safety edges it would probably be impossible to guarantee that such an installation meet current requirements for gate automation safety.
Today, safety is rightly placed as the major consideration when designing and installing automatic gate systems. So, if you have a slope and need a sliding gate, the best answer is either to level the ground or to use a cantilever gate.
Written by: Steve Jones A