Do you know the difference between a reversible (‘non-locking’) gate motor and an irreversible (‘locking’) gate motor?
The first allows an automatic gate to be pushed open or closed by hand in the event of an emergency when there is no power. The second usually features some physical mechanism to prevent this from happening. This could be a hydraulic non-return valve or the way the motor and gears are connected. However, it is possible with enough effort, to force a ‘locking’ gate motor but you will break something in the process.
Most manufacturers will recommend additional locking for any leaf of 2.5m or longer. This is to protect the mechanism and not the entrance. This is why you will often find ‘locking’ and ‘non-locking’ versions of the same motor specified for different length leaves.
You must understand that the leverage that even a small child can exert on a long leaf is immense. As the mathematician Archimedes is said to have commented on the lever, ‘Give me a place to stand on, and I will move the Earth.’
I have seen with my own eyes the 10mm thick steel brackets holding a motor on a 4m five-bar gate (which did not have a lock to hold it shut) being bent by a 9 year old pushing at the opening end.
So if reversible gate motors and even ‘locking’ gate motors do not lock a gate shut, what’s the point of having them? Where is the security they’re supposed to offer? Where is the resistance to winds, falling objects or children pushing against them?
The answer is simple and not expensive. It’s also the recommended additional security for any gate over 2.5m in length. It is a simple mag lock.
Traditionally, reversible motors have been used for applications that include a requirement for opening in the event of a fire without power. In this situation, if the power fails, a mag lock will release and the gates can be pushed open. This design has been superseded by the advent of 24V systems which can be backed up easily by batteries and allow a gate to be powered open in the event of a fire.
Mag locks are generally simple to fit and allow for a certain amount of play in a gate. It is enough that the lock and plate meet face to face for it to hold the gate locked, although you must remember that if the power to the lock fails it will release.
So don’t be fooled by the promise of ‘locking’ gate motors – they don’t exist. If you want to provide your customers with genuinely locking gates that lock shut at the end of their closing cycle and are released when their opening cycle starts, simply fit a mag lock.
Automate My Gate 
Nice article, good to see someone write genuine information for consumers rather than sales pitch.
Read the article after seeing a tweet about it. What sort of force can mag locks take before being opened i.e. how secure are they against unauthorised access?
Thanks for your comments Fenland Fencing, they are much appreciated.
You will find that most external magnets on the market have a holding force of either 250/300 KG for a small gate or a larger one will be 500/600Kg. On even the small one it is likely that the fixings, or something else on the gate will give before the magnet does. It would not surprise to see a gate bashed off its hinges dangling off a magnetic lock. Having said that, as I note above, if the supply cable can be cut the lock will open, and although this type of risk can be overcome with electromechanical locks of course with the wonderful wealth of battery operated tools we have these days, any isolated gate can be interfered with and most can be opened by using a transit van applied at the right speed. For additional security you really need to look at various means of surveillance which will warn of an attack