Page created: 13-May-05

Re-published: 1-Nov-09

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Ancillary Wiring

Desert Wolf Trailer

My requirement for a tank guard wasn’t driven so much by the protection it offered as by the fact that it was an easy way to achieve a removable tow bar.

The standard Discovery tow bar is commonly referred to as ‘the plough’ and with good reason. It severely limits the departure angle and is invariably dragged through or over rough ground, particularly at the foot of steep hills. It is probably the single biggest limiting feature to easy progress off-road. Also, whilst the tow bar is pretty robust, it’s always seemed to me a little reckless to abuse a tow bar on an off-road course somewhere and then tow a caravan home again, which many people seem happy to do. Admittedly, the Discovery tow bar is more substantial than those fitted to the Series Land Rovers I’ve owned previously, but it’s still a risk I’d rather not take.

The only realistic solution to this problem at the time I was looking was the Southdown tank guard with removable tow pack. A number of alternatives have come on to the market since from a variety of manufacturers but I still believe the Southdown solution is the most elegant. Essentially the system comprises a substantial steel tank guard and a large wedge shaped drop plate with four pairs of holes to accept a standard tow ball at a variety of heights. The tank guard has two 10mm thick flanges on the bottom face and the drop plate is secured to these flanges with two 19mm steel pins. It is a simple operation to pull out the pins and remove the drop plate, which instantly restores the departure angle back to the factory maximum dictated by the rear bumper.

One of the fundamental problems of having a tow bar that can be completely removed is what to do with the towing electrics. The options are to leave them attached to the back of the vehicle or to also make them removable in some way. On my previous Land Rover I mounted the 12N and 12S sockets high up on the bodywork, which kept them out of the mud, and used a pair of extension cables and duplicate sockets on the tow bar itself. Unfortunately, I couldn’t replicate this on the Discovery, as there isn’t enough space on the rear of the body and the bumper projects out too far.  It was also complicated by the fact that there is potentially a high current draw when charging the two on-board batteries in our Desert Wolf trailer. After a bit of searching I found a small waterproof multi-pin plug and socket with two high load pins produced by AMP that I could fit out of harms way under the rear wing. This combination only has ten pins but in practice this is sufficient for a standard installation, as there are several spares in the usual pair of 7 pin sockets.

I’ve flush mounted the socket in a waterproof enclosure, which in turn seals the hole in the body where the towing electrics wiring exits. Standard 12N and 12S sockets are fitted to the removable tow bar and these are connected via a flexible umbilical. When the tow bar is removed a waterproof cap protects the socket under the wing.

The tank guard itself is a well-engineered piece of underbody protection. It is supported by being fitted to the four existing tow bar mounting points, although the bolts through the chassis where the diagonal braces for the original tow bar were fitted are substantially bigger. The front edge of the guard has an upturned lip that is designed to be pressed tight up against the chassis cross-member in front of the fuel tank. This means that any severe impact on the guard is more or less evenly distributed directly to the chassis whilst a gap of approximately half an inch between the underside of the tank and the guard ensures that the tank is effectively isolated from any shocks.

In addition to the standard removable tow pack, Southdown also make a low profile jacking and recovery hitch that mounts to the guard in the same way but without affecting the departure angle. This provides a horizontal towing ring cut from 10mm steel plate, to which a rope can be attached with a shackle, and a tube designed to accept a 90/110 hi-lift jack adapter. As, having removed the tow bar, there is little else on the back of a Discovery to attach a rope to, it seemed like a worthwhile addition!

Finally, I had Southdown fabricate a special version of their removable drop plate for use with our Desert Wolf trailer. The hitch on this trailer is at the same level as the rear cross member and, as it’s designed for use off-road, the depth of the standard drop plate would prove to be a hindrance. I therefore had them make me a special drop plate that only has the top pair of tow ball mounting holes. To this I’ve added a Dixon Bate 3.5 tonne ball and pin combination hitch which provides a good quality tow ball with a convenient place to attach the substantial safety chain that’s fitted to the trailer. As an aside, this chain probably isn’t strictly legal for use in the UK and the trailer also has a standard safety cable connected to the brakes. However, in the sort of terrain that the trailer is designed for the safety chain is a much more practical solution.