Mighty Mule MM571W Review: A Wi-Fi Swing Gate Opener for an 18-Foot, 850-Pound Gate

The first automatic door in recorded history opened a temple. In the first century AD, Heron of Alexandria described a machine in which the priest lit a fire on the altar; the heat expanded air in a sealed vessel, the air pushed water out of a container into a bucket, and the falling weight of that bucket turned the door pivots on ropes. The doors swung open by themselves. When the fire went out, the air cooled, the water siphoned back, and the doors closed. The congregation saw the will of the gods. It was a thermodynamic actuator.

Heron of Alexandria's automatic temple doors — fire, air, water, and a gate that opens itself (photo: Wikimedia Commons).

Two thousand years later the fire has been replaced by a 12-volt battery and the ropes by a linear actuator arm, but the sales pitch has not changed at all: you arrive, and the gate opens without you getting out of the truck. In Arizona, where the gate is often at the end of a long dirt drive and it is 108 degrees outside, that is not a luxury feature.

The MM571W, in numbers

We have one in stock: the Mighty Mule MM571W smart Wi-Fi automatic single swing gate opener kit, $379.99. The headline specs:

• Configuration: single swing gate, heavy duty
• Gate capacity: up to 18 feet long or 850 pounds
• Power: 12 V battery operated — battery and transformer included
• Operating range: -5°F to 160°F (the top end is the one that matters here)
• Certification: UL325
• In the kit: gate opener arm, control box with battery box, remote with visor clip, 12 V 7 Ah battery, transformer, mounting hardware set, instruction manual
• Gate materials: ornamental, chain link, tube, panel, vinyl and wood

What UL325 actually means for you

UL325 is the safety standard covering powered gate operators, and it is the reason a gate opener costs more than an equivalent-strength winch. It governs entrapment protection — the operator has to sense an obstruction and stop or reverse rather than crushing whatever is in the way. If you have kids, dogs or delivery drivers, buying a certified operator rather than an uncertified import is the single most important decision in this whole project.

Sizing: read the two numbers as an "or", not an "and"

Eighteen feet or 850 pounds. A long light aluminum gate and a short heavy wrought-iron one can both be at the limit for completely different reasons, and length is usually what bites first — leverage at the hinge grows with the leaf, and wind load grows with the panel area. A solid-infill gate catching a monsoon gust is a sail. If your gate is near either number, go up a class rather than running this one at its ceiling for ten years.

The things people forget to buy

Straight from the manufacturer's own notes, and worth knowing before the box is open:

• Ball-bearing hinges are required for gates over 250 lb, and they are not included. This is the number one cause of a "weak" opener — the operator is fine, the gate is simply hard to push.
• Low-voltage wire is not included. Measure your run from the control box to the operator before you start.
• Solar conversion and the smart-hub control are accessories sold separately and are not in this kit. The MM571W supports them; it does not come with them.
• A gate that does not swing freely by hand will never swing well under power. Fix the hinges, the sag and the drag first.

Condition, stated plainly

This one is open box. The retail carton has been opened and shows crushing, tears and a tape repair at one corner. Inside, the operator arm, control box, mounting hardware bag, wiring lead and printed manual are all present and still seated in the original moulded factory packaging. We did not remove components for individual inspection, we have not powered up or programmed the unit, and battery condition is not verified — a 12 V 7 Ah sealed battery is a cheap and common part if it has sat too long. Photos 2 through 5 are the actual item and its packaging as we received it.

The rest of the entrance

While you have the trencher out and the driveway torn up: a SLAWA outdoor post cap light, modern square, IP65 waterproof aluminium, at $109.95 for the gate pillars; a Mail Boss 7173 Townhouse locking anti-theft wall mount steel mailbox at $99.95; a 9-piece hardware lot with gate closer, hinges, kickplate, garage door seal and a Paslode battery at $87.99; a pair of Nilight heavy-duty rubber curb ramps, 7.9-inch rise, 7,000 lb rated, at $119.99 for the lip at the end of the drive; and if the point of the gate is really the dog, a yhpet GF02e GPS wireless dog fence with no subscription at $89.99.