The Australian Army took delivery of its first operational Land Rovers in March 1959, after a year-long trial of the vehicles. By the middle of 1963 the Army had purchased 1,841 Series 2 Land Rovers, in both 88” and 109” wheelbase, for a variety of roles – from General Service to Wire Laying and Ambulance, and even in an offensive role carrying the 106mm recoilless rifle.
This association continued with the release of the Series 2A Land Rover, with 4,776 purchased by the Army by April 1977, and was on-going through Series 3 and the Perentie 110 (see Issue 12).
The Government of Robert Menzies announced increased involvement in the Vietnam conflict in March 1965 and Land Rover looked to supply Australian forces with the perfect vehicle for operations in South-East Asia. Issues with crossing heavily flooded paddy fields had come to the fore and the Army thought it may have a need for a rapid all-terrain vehicle with the ability not just to wade, but swim.
Land Rover Amphibians
In 1961-’64 Land Rover had experimented with an amphibious Air Portable General Purpose vehicle to meet a British Army requirement – FV 18051 (Scheme A) APGP in Army-speak. Although field-tested by the Army, the vehicle was rejected mainly on the basis of its cumbersome separate floatation bags that had to be assembled, strapped to the body and inflated, its slow speed on water and the vulnerability of its air bags under fire.
The FV 18061 (Scheme B) of 1962 was a forward-control truck that reached mock-up stage and featured a 97” wheelbase with a body with inherent floatation abilities. An air-portable 4x4 with a 1-ton payload, powered by the 77bhp four-cylinder engine, confirms Land Rover had amphibious ambitions prior to the Australian requirement.
The OTAL (One Ton Amphibious Land rover) was constructed by Land Rover Military Engineering Department, especially for the Australian Army as a Commanders/Radio car. Their brief was for “a vehicle which has all the characteristics of a Land Rover but in addition is able to cross inland water without special preparation and without using applique flotation kits”.
Unlike the APGP, the OTAL had a boat-shaped flotation hull, similar to that of the GPA (sea-going Jeep) from the Second World War. This did away with the long setup times of the APGP to fit and inflate it’s flotation bags.
Although a similar overall size to existing Land Rovers of the time, the OTAL didn’t share their 88” or 109” platform, but was constructed on the same 97” wheelbase of Scheme B. Most of the running gear was standard Solihull fare, thus parts availability should not have been an issue.
However, it was powered by what was, at the time, a new and rare engine; a specially adapted and modified 2.6 litre straight-six petrol engine, with its origins from the P4 Rover 90 saloon, fuelled by a single SU carburettor.
In his definitive history of the marque, Land Rover – 65 Years of the 4x4 Workhorse, James Taylor says of the OTAL engine: "Exactly why the 6-cylinder engine was chosen for this vehicle remains unclear. Australian military Land Rovers of the time all had 2.25-litre petrol engines, and so it is unlikely that the customer demanded the engine. It is more likely Solihull thought it was necessary because of the OTAL's great weight. At 3,950lbs (1,791kg) unladen it was approaching the weight of a Forward Control..."
Fully loaded the OTAL tipped in at 2.83 imperial tons, which justifies the 83bhp and, more importantly, 128 ft lbs torque at just 1500rpm, provided by the increased capacity.
The first Land Rover with the 2.6lt six-cylinder was the 109” station wagon available in US from summer 1966, as a 1967 model. It may be that Land Rover was at that stage pushing the 6-cyl and wanted the Australian Army as a customer of the engine, which would have given them great kudos, but this is purely conjecture.
It may not be purely coincidental that the Australian Army Series 3 Land Rovers, introduced in 1977, featured the six-cylinder engine.
The all-aluminium body of the OTAL was built in a sealed pod-style in four separate sections, with hand-constructed rear and centre/cab sections. The front fenders are bolt-on watertight units, offering buoyancy, with easy removal providing greater access to the engine area, with a sealed toolbox hatch on top of each.
Any space suitable on the vehicle, including the chassis, under the floor and the front wing buoyancy tanks, was filled with polyurethane foam. As well as adding buoyancy it is unaffected by small-arms bullets, unlike the earlier floatation bags.
Interestingly, the conventional engine bay is not watertight and the waterline was level with the head gasket. This was successful on the prototype, but it is expected that in production the engine compartment would have been completely sealed, to provide even greater buoyancy and to give greater protection to the engine’s electricals. The distributor, from a wartime Daimler Scout car, is sealed and sits on an extended 8” alloy housing.
Both engine and gearbox are sealed units, vented by pipework that remains above the waterline. Intake is via a snorkel sitting just behind the heavy-duty drum winch mounted on the front of the vehicle. The exhaust exits at the rear behind the driver, right on the waterline. An additional section of pipe would be attached before the vehicle entered deep water, which extended the exhaust to roof height.
Crew entry is via a folding door on each side, with non-slip step installed. Once closed these form a watertight seal, which was important as the OTAL had a very low freeboard (the height above the waterline).
The four-speed gearbox is of 1-ton specification, while a hydraulic pump powers the winch which is controlled from inside the cab.
The UK tests were carried out on and around the calm lake at Packington Park, a nature reserve in Warwickshire, and possibly at Eastnor Castle, home of Land Rover testing since 1961. There are also a few photographs of initial controlled water tests in a wading tank, that look precarious.
While few reports from the UK trials are available, one undated report from the Land Rover Engineering Department did confirm; “Cross-country performance is up to normal Land Rover standards with good approach and departure angles and adequate floatation on large tyres”.
A silent, six-minute long, black & white film of these tests has recently been discovered, which confirmed the OTAL’s off-road performance and ruggedness.
On-road performance was reportedly very good due to the six-cylinder engine.
However, the film shows that on the water, the OTAL’s operation was, at best, marginal. Propulsion and steering were effected by the vehicle’s wheels, which restricted its speed to an estimated 4 or 5 knots (nautical miles per hour).
However, according to the above report, reproduced on remlr.com (the Australian Registry of Ex-Military Land Rovers); “experiments with deflectors near the rear wheels and with propellers driven by the power take-off, suggest that the vehicle could be given enough speed to cope with most inland water flows.”
Heading To Australia
Sadly, Army records of the tests carried out in Australia either no longer exist or are lost deep within the archives, as a search by the Army History Unit has failed to turn anything up.
However, we do know that the OTAL arrived in Australia for vehicle trials in the first half of 1966 and was tested at the Army’s Trials and Proving Wing at Monegeetta, near Lancefield in Victoria.
Only one photo of the vehicle during this time is known to exist, which shows the OTAL exiting the Deep Wading Pool at Monegeetta and reveals the Army registration number (ARN): 108-430.
According to REMLR, research on this ARN has turned up a one-ton truck prototype, indicating that ADE (Australian Design Establishment) re-used these registrations.
Although we don’t know to what extent the OTAL was tested in Australia, or over exactly what period, we do know that it was given a run on Lake Burley Griffin in Canberra, on 6 August 1966, "in front of Army and Industrial observers." A single photo and very brief description was published in the Canberra Time newspaper the following day, while another colour image shows the vehicle beside the lake.
Due to the lack of information available, it would appear that the OTAL never progressed on to tropical or outback trials. (NB: the Tropical Trials Establishment at Cowley Beach, near Innisfail, Queensland, was only established in that year.)
The BMC Experience Issue 22. Jul-Sep 2017 Magazine
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