A model of an Armstrong-Saurer twin axle bogie as was fitted to the Dominant 6-wheeled truck, produced in the UK between 1927 and 1931. This bogie is very unusual in design and construction in that it features three differentials in-line, mounted transversely between the fore and aft pairs of wheels.
The central differential drives secondary differentials either side, each of which split the drive to the front and rear wheels either side. The axle sections encasing the side differentials also house bevel gear drives to each wheel that side, and allows articulation to compensate for road irregularities. This arrangement achieves full differential action between the four wheels and the axle input drive.
As the unit involves triple co-axial journals, he decided to use large axle parts to achieve the required complexity of movement, and base the model on the 6” diameter ashtray tyres that he pioneered the use of on his Grader, published in the July 1960 issue of Meccano Magazine. This established a model scale of 1:7.
The assembly is fitted with semi-elliptic springs for attachment to a vehicle chassis, which may be the next phase of model development.
Some progress has been made on the 1:7 scale Armstrong-Saurer truck chassis. The steering box is modified to include a power assist motor for proportional remote radio control (R/C). This also required a double pole double throw sensing switch to be designed with a primary sliding pole supplying power via moving contacts, the other secondary sliding pole carries connections to the steering motor and senses steering drop arm movement. The primary pole is operated by a small flight servo by the R/C transmitter such that the steering motion feedback to the secondary pole provides proportional steering movement.
A new 3-speed and reverse gearbox with ‘H’ gate shifter and new clutch design is included.
A high torque Como Drills motor with 6:1 gearbox provides traction power, which unfortunately, creates radio frequency interference (RFI) of the steering servo. Various solutions to the RFI problem have been tried such as adding interference suppressing capacitors and moving the receiver away from the electronic speed controller (ESC) without effect, so the next step is to try a high torque, low speed R/C truck motor geared to the clutch…
The chassis and body are complete.