2022
Build Feature :Amphibious Truck
by Sam Keirs
The idea for this model was inspired by an article in Model Boats magazine (July 2011 issue) for an amphibious British Army vehicle - the ALVIS STALWART. That article detailed the build of a complex scale model with six-wheel drive, with jet drive propulsion on the water. That made it too fancy and too expensive for Sam, who started building his version during the Christmas holidays and wanted to make rapid progress using basic tools and techniques.
Sam based his model loosely on the ALVIS STALWART, and made a good start by buying a second hand 1/10 scale model car with a worn out engine. That provided the steering mechanism, two differential units and some drive shafts.
Resources
Information:
Overview: https://en.wikipedia.org/wiki/Alvis_Stalwart
Photos of variants: https://commons.wikimedia.org/w/index.php?search=alvis+stalwart&title=Special%3AMediaSearch&fulltext=Search
Kits:
https://accurate-armour.com/aa-products/135th-complete-kits/k160
Books:
Truck, Cargo, HMLC, 5 Ton, 6x6 Alvis / Stalwart Mk2 (FV622)
Published by Military Library Research Service Ltd, Buxton, Derbyshire, 2006
The ALVIS STALWART (FV623) was an amphibious truck used by the British Army, and by other nations. It went through a series of versions, and a typical late example is shown here as a Mark 2, 6x6 High Mobility Load Carrier with an integral crane.
The radio control system is a HiTec 8 channel set with an engine sound unit. The left stick controls the props and rudder. The right stick controls the land drive for the wheels, and operates the steering. The land drive can be switched ON or OFF as required. The rear and front side lights are used to indicate whether the land drive is ON or OFF, which is useful when the vehicle is in the water and it is not immediately obvious if the land drive is operating. Side lights ON indicates that the land drive is OFF.
The chassis is a basic ‘ladder’ style made from wood.
Below the chassis Sam made a box out of 1/8inch (3mm) ply for the steering, the batteries, and the four wheel drive system.
Above the chassis was the driver’s cab and all the radio control gear.
The upper body was made from 1/16inch (1.5mm) ply.
The prop layout proved a bit of a challenge,and initially the prop was positioned centrally between the rear wheels. However; with the prop in that position the vehicle refused to go astern. A second attempt used two props, one behind each rear wheel. Each prop was enclosed in a KORT nozzle, and rudders were mounted behind each prop.That worked much better.
The land drive uses an 11 volt supply to power an MFA919d motor with a 50:1 gear reduction feeding into the transfer gear to power the front and rear differentials. Motor speed is controlled by an MTronics speed controller. The steering servo is a HiTec sail servo (model HS565NB) as the steering requires a bit more torque.
The on-the-water drive uses a 14 volt supply to drive two 50mm props through a 2.5:1 gear reduction. The rudders are operated using a standard servo.
The model is great fun to drive/sail, and can drive down a ramp into the water, sail around, then climb back out again. That’s just as well, because this model tips the scale at 2 stone 14 pounds (or just over 19Kg).
A scale model of this size is not really complete without a driver, and there’s a seat for a navigator too.
