Launch Vehicle

SEATRAC Launch Vehicle

On the 21st of March 2006, Sidmouth Lifeboat took delivery of the new DODO ( Drive On Drive Off ) launch and recovery system. The system comprises of 2 units, the Marinised Tractor unit and the Semi Submersible Trailer unit. The tractor is a specially modified Renault agricultural tractor, that has been waterproofed and fitted with a fresh water washing facility. This modification was carried out by P Bowler & Son. The Lifeboat trailer was built by Admiral trailers and features hydraulic lift capabilities, LED running lights and floodlighting.

DODO Specifications

Wheels

Seatrac is fitted with welded and Galvanised wheel centres shod in 30" wide tyres on the rear and 25" wide tyres on the front. These have been water ballasted to achieve two results:-

To present negative buoyancy ( the unit retains good ground contact even when submerged fully)
To increase the weight of the tractor by 4 tonnes, thereby compacting the shingle to increase its 'shear strength' to obtain maximum traction.

Engine & Transmission.

The tractor has been stripped of all ancillary components, down to the bare engine and transmission casings and has had the following modifications:-

Sealed clutch housing with greased seals
Oil splashed clutch assembly with Cera-Metallic plate to avoid seizure
Grease nipples fitted to all axle Universal Joints
Engine crankcase, clutch housing and gearbox cases are fed with exhaust gas under low pressure to equalise water pressure whilst components are submerged, and to push small amounts of oil past seals when on dry land, thereby lubricating seal 'lands'
The chassis and running gear was then given 8 additional coats of paint over the original substantial factory finish, and then heavily coated with Waxoil
The starter motor was sealed to prevent water ingress

The engine air intake is routed into the top of the cab interior via twin ball float valve boxes which will shut off the air supply to the engine should the tractor be accidentally submerged.

A Cam action 3" bronze gate valve is fitted to the exhaust pipe, controlled manually by cable from the cab, to seal the engine if the tractor should need to be left submerged for any length of time. The engine and fuel tank breathers are fed into the air intake and are isolated when the valves are closed.

The unit has successfully endured a 4 hour submersion test and restarted.

Blade

The Blade or Frame on the back of the Tractor unit, is multi purpose, having three functions :-

1. It acts as a levelling blade, allowing the beach to be levelled and graded so that a suitable ramp can be constructed, making safe and easy access for launching and recovery. The blade can also be used to level an area at the top of the beach, which is required to turn the Lifeboat through 180^o, ready for re-launching..

2. The structure of the Blade comprises hollow steel sections that are welded together. This creates a tank that is filled with water. When the tank is connected to the engines on the Lifeboat, it allows the engines to be warmed up before entry to the sea.

3. The Blade provides protection for the Tractor and driver.

Cab

Contains all the controls and radio for communication with Arctic24 Lifeboat. The height of the Cab floor is 50", so that the unit can function in deep water.

Trailer

The trailer unit is where the Lifeboat is launched from. The trailer is of a " Tuning Fork " design, so that the lifeboat can sit in the trailer and to allow rapid launch and recovery. It is hydraulically height adjustable, allowing the Lifeboat to be lifted from the water by approximately 36", when being launched and recovered. This height adjustment also allows a rapid turn around of the Lifeboat, after a "Net" recovery, where the lifeboat enters the trailer forwards.