Autoveicolo da Montagna 3x3 (Mulo Meccanico)
At the end of the 1950s the Italian Ministry of Defense asked Moto Guzzi to develop a special vehicle for the Alpini. At that time, the only "means of transport" for the Italian Alpine troops was still the mule. General Ferruccio Garbari was indicated as project director and formulated numerous requirements that the vehicle would have to satisfy: it had to carry 500 kg of cargo in all types of terrain, especially in mountainous areas and on very narrow paths. The development was initially entrusted to Antonio Micucci and later elaborated by Soldavini and Giulio Cesare Carcano. Carcano had just built a new V-twin engine, for which Moto Guzzi management saw no practical outlet. There were two versions, a 500 cc, and a 650 cc unit designed for the Fiat Nuova 500, but the Turin house withdrew from the project. Carcano then saw another possibility to put his engine to use.
The "Mechanical Mule" was a very special machine, with three driving wheels and the possibility of varying the wheelbase and track. The 754 cc engine delivered just 20 hp, due to the low compression ratio, made inevitable by the tactical need to consume, when needed, poor quality petrol. However, the maximum torque of 47 Nm was already reached at 2400 rpm. There was a single 26mm Weber carburettor, and the ignition coil was waterproof.
The frame was made of pressed steel tubes and beams. The rear suspension consisted of two girder arms cushioned by rubber blocks. A single-sided telescopic fork with coil springs was applied to the front wheel. Steering was achieved by a steering wheel served by bevel gears. The driver sat on a motorcycle saddle, but all controls were actuated by automotive-type levers and pedals. There was a center differential with a locking device to prevent the wheel with the least grip from bogging down. Traction was distributed 20% to the front wheel and 80% to the rear. Rear wheel drive was accomplished by two universal joints reaching the wheels diagonally from the differential; the front one through another cardan that connected the engine to the wheel through the steering wheel. The rear drum brakes were operated hydraulically, the front one with a Bowden cable. Behind the rear wheels were tension rollers, to which a track could be attached. The front fender left enough room to fit a snow chain. Nonetheless, the Autoveicolo da Montagna disappointed expectations. As long as it was frontal gradients, it was really capable of dealing with very steep slopes, but laterally it was easy to tip over, especially because of the three wheels. On mountain routes, a too tight curve or the presence of boulders was enough to stop the Mechanical Mule, whereas the "real mule" would have continued undaunted. Also for this reason, the production of the three-wheeler ended in 1963.
From 1960 to 1963 the company built 420 mulos - 20 prototypes and 200 each of the 1st and 2nd series.
The heart of the "Moto Guzzi 3x3" is a V-twin engine of 754cc delivering 20 PS at 4,000 rpm, fueld by a Weber carburretor. This engine was developed by Carcano as an experiment, and was subsequently modified to to obtain a maximum speed of 50 km/h. The 6 speed gear box was equipped with a reverse gear which drives the front wheel, with forward transmission delivered to the two rear wheels via cardan shaft, and also to the front wheel giving 3-wheel drive.
A central differential distribute the transmisson between front and rear wheels and has a manual lock-out - also the rear differential has a lock-out.
Additionally, to allow navigation on the narrow pathways common in Italian mountains the rear wheel track may be varied from a maximum of 1300 mm to a minimum of 850 mm.
The Mulo has a maximum load rating of 500 kg.
Sources:
Moto Guzzi Database by Wim Meijer via the Internet Archive.
it.wikipedia.org/wiki/Motocarri_Moto_Guzzi
