DRIVING/TOWING - RECOVERY TECHNIQUES
We’ve heard recently about issues with snatch blocks failing during winching operations, which creates a very dangerous situation that is potentially fatal, if the snatch block pulley becomes a missile.
At Outback Travel Australia we’ve been using snatch blocks of varying brands for years and never had a problem, so we decided to look at what could go wrong.
The majority of snatch blocks have pressed steel cheeks and a cast or spun central pulley that rotates on a steel shaft. Some snatch blocks have grease nipples, but the majority require disassembly to perform periodic greasing.
The most common types of shaft retainers are circlips, but there are also ‘C’ and ‘E’ clips and spring locking pins.
Heavy duty snatch blocks have large-diameter pulleys and shaft bearings, but the bulk of 4WD snatch blocks have non-bearing shaft-to-pulley attachment.
All the failed snatch blocks we’ve been told about had circlip attachment, which made us think that dislodgement or failure of a circlip was the most likely cause of the snatch block coming apart during loaded operation.
We dismantled one of our own snatch blocks that was due for maintenance and expected no drama. As normal, we used circlip pliers to expand one clip and withdrew the shaft and pulley. We gave the pulley and the shaft a clean and put fresh grease on both of them. We gave particular attention to the circlip groove in the shaft, making sure it was completely clean.
When we put the snatch block back together, we expanded the circlip and found that it wouldn’t seat properly. It had expanded for removal and simply wouldn’t recompress. It was an original circlip, so it had obviously been made from sub-standard spring steel.
We pulled the snatch block assembly apart once more and threw both circlips into the rubbish bin.
We visited our local parts supplier and picked up four brand new, quality ‘C’ clips. We’ll evaluate them as alternatives to circlips and report on our findings. They’re certainly much more robust and don’t require circlip pliers to fit.
The last thing you need when doing snatch-block winching – normally more heavily loaded than simple, single-line winching – is for a clip to fly off and let the snatch block cheeks open up, releasing the loaded pulley and winch line.
In that event, if the driver inside the vehicle being winched isn’t quick enough to react, the vehicle could run away out of control. Not a pretty thought.
Improved snatch block design
We’re testing a new-design TJM snatch block, during 2021. This model is rated for 10,000 pounds load and has a recessed grease nipple for easy lubrication.
It also has screw-on retaining nuts – not clips – to secure the shaft in the cheeks and the nuts are locked by tabs against accidental loosening during winching operations.
We’ll report on progress mid-year.