Amongst the many ideas for cutting barbed wire in the First World War, there is one vehicle which stands out for its unusual appearance. Unlike some merely sketched out by a bored engineer at a meeting in Whitehall, Berlin, Paris, or Rome, this vehicle was actually built and tested.
1925 promotional image of the Pavesi Autocarro Tagliafil. The 1915 date is incorrect, however. Photo: Ceva and Curami
Ingg. Pavessi & Tolotti
The designer of this unusual machine was Ugo Pavesi (17/7/1886 – 13/7/1935), a well-respected engineer from Novara, a city just west of Milan in Italy’s industrial North. After finishing his engineering degree in 1909, he worked for a while for Giovanni Enrico’s engineering firm. He then partnered with Giulio Tolotti (also an engineer) to form their own company called La Motoaratrice (Brevetti Ingg. Pavesi & Tolotti) between 1910 and 1912 with an office in Rome but with the workshops in Milan. Ugo Pavesi was the main designer and Managing Director and Giulio Tolotti was the Technical Director.
The future prospects for the firm were to blossom with the outbreak of WW1 and the sudden need from the Army for all types of vehicles for a variety of purposes. La Motoaratrice was therefore in a perfect position of having a design for a tractor suited for hauling material over badly broken ground at just the right time. An initial Army order asked for 150 truck tractors followed within the first year for another 350 machines. In total, during the war, the firm received orders for 1000 of their tractors and 5000 trailers.
Details of the P.T. Pad Wheel compared to the original spade wheel. Photo: Chilton’s Automotive Industries, 1917
The wheels were very unusual and were a design from Pavesi-Tolotti known as the ‘P.T. Spade Wheel’. Each wheel was fitted with 12 large flat plates acting as the spades. They had first been shown off in 1911 at the World’s Fair in Turin and had been the spur to create the firm to capitalize on the interest in this design. In 1912, when production had begun at their factory, the intention had been to market the wheels primarily for agricultural purposes in South America. The individual plates actually could be
“operated from an eccentric on the axle through an intermediary of strong links, in such a way that the spades would enter the ground almost vertically, remain vertical for sometimes and then be drawn out in practically the same direction. In this way the spades gave a very powerful grip without any great loss of power due to scraping of the soil. By turning the eccentric through an angle of 90 deg., by means of suitable levers, the spades were kept within the outer diameter of the wheel, thus permitting of driving the machine over hard roads”
This spade wheel would find use in other designs, but the wheels for the Pavesi Autocarro Tagliafili would, in fact, not end up using these excellent wheels, but a follow-on design called the Pad wheel. Far simpler than the complex spade wheel, the pad wheels did not rely on the motion of an eccentric to turn a spade into the ground, but instead, were held to the wheel by means of tension springs securing traction on the ground through the friction of the plates in contact with the ground rather than spades penetrating it. Some of the tractors produced for the Italian Army used double wheels at first to increase the ground contact area, but these were replaced by 1916 by means of simply widening the pad wheels as used on the Pavesi Autocarro Tagliafili. The double wheels had a diameter of 95cm with 25cm wide pads. This type of wheel is sometimes referred to as a ‘track-laying-wheel.’
First prototype of the Pavesi Autocarro Tagliafili. Note the single turret and 4 wheels. Photo: Pignato
The original Army tractors without any armor weighed in at nearly 5 tonnes and were fitted with 4 cylinder petrol engines producing 50hp at 800rpm. Despite the small size of the engine, the tractors could haul up to five 20 tonne wagons hitched together up to a total weight of 100 tons at up to 3 miles per hour. This hauling ability made them an ideal basis for work on an armored vehicle.
Rear view of the first prototype showing the absence of a rear firing machine-gun and that the single turret is open-topped and open-backed. The path of the vehicle can be seen having ploughed successfully through the wire obstacle. Photo: Pignato
The design and construction of the prototype are known to have started by at least early 1916 using the body of a Pavesi-Tolotti Tipo A tractor. The Pavesi-Tolotti tractor powered its special rear wheels from a front mounted engine. The wheels at the front of the tractor were smooth rimmed. However, on the Pavesi Autocarro Tagliafili, the larger wheels with the special pads were on the front with the smooth wheels at the rear. The arrangement of the machine therefore appears to simply be a reversal of the standard tractor. The prototype has just the four wheels and with the engine at the back, explaining the low rear half of the machine. The front wheels were covered with some plating, removing the view of the spokes, although it is not clear if this was armor or something else like timber simply to stop them clogging-up with mud or to prevent the ends of cut wire from snagging in them. Over the ‘front’ of the machine was a large boxy cab with a flat face and sloping front plate above it, in which a single rectangular viewing hatch was located on the right hand side for the driver. A small circular port was provided in the side of the cabin on both sides.
Another test against wire was successful having cut a wide path through it. The path is now caused by those horizontal beams on an X frame.
On either side of the front were two tall wire cutting serrated vertical bars which stuck out from each side. As the vehicle would drive forwards into a wire entanglement, these serrated vertical sections would separate the wire against the cutting surfaces. Rather than simply relying on the forward motion of the vehicle to cut the wire, there was a driven horizontal shaft coming out of the side of the cab which connected to the middle of each vertical bar. Rotation of that shaft driven from the engine caused the two sets of vertical teeth in the cutting column to move up and down opposite to each other producing a cutting motion.
Under the front of the cab and protruding out to each side to the same extent as the serrated vertical cutting columns was a small horizontal bar fixed securely to the cabin. The exact purpose of this bar is unclear, but it may just have been to remove smaller obstacles the vehicle would pass over.
The only weapon mounted on the prototype was a single Fiat model 1914 6.5mm water-cooled machine-gun mounted behind a gun shield within an open-topped and open-backed cylindrical turret. The cylinder for it covered the full height of the vehicle. Construction of the machine, having started by at least early 1916, was not quick. The testing for the Commission set up by the Army to evaluate the design was delayed from 10th July 1916 to the 9th of 9th November that same year.
Tests on the prototype with it driving through wire obstacles were delayed by mechanical problems with the machine, postponing further testing from the 9th November to the 13th. This second round of tests was much more successful, but the Army was concerned that the vehicle was unsuitable for crossing anything but flat ground, was too slow, and had inadequate protection.
Recommendations for improvement were to boost the speed and protection, reduce entangling of the front wheels from broken wire and improve traction.
Modified prototype with an additional set of wheels and modified wire cutter. Photo: Pignato
The Pavesi Autocarro Tagliafili – Illustrated by Bernard “Escodrion” Baker
As the existing machine was based on the existing Tipo A tractor, very little could be done to improve the power of the vehicle, but modifications were carried out at Belluno, in the Italian Veneto region, from May 1917. A second set of wheels was added to the front which would improve traction cross country, as well as improve performance on soft ground. To prevent snagging and entangling by wire, a new cover was designed to go over both wheels with an additional serrated section between them to catch any wire before it could get wrapped around the axle of the wheel or in the pad mechanism. Likewise, at the rear, the pair of smooth rimmed wheels which were previously open spoken were also covered over.
Modified prototype during road trials prior to completion. Photo: Pignato
The inadequate protection complaint was resolved by moving the small turret further forward to the very top front corner of the machine and adding a second one on the other side, giving the vehicle its’ unique side by side turret appearance. Both turrets were now completely enclosed. To achieve this, large curved portions had to be cut out of the front sloping armor plate. The armor itself was steel, only 3.5 to 4mm thick, riveted to a steel frame. The new sides of the cabin also gained two long horizontal vision slits in each side in addition to the previously existing small porthole. These slits would provide additional vision for the occupants, although they were only chest hight with respect to the driver, suggesting that they were cut into the sides to facilitate looking down at the terrain and obstacles being crossed. A final addition to the vision was the inclusion of a further rectangular hatch in the rear of the cab directly behind the driver.
The rear of the machine was modified too, with an additional Fiat model 1914 6.5mm water-cooled machine-gun added to the back panel flanked by two horizontal vision slits.
A final modification was to the wire cutters. Photographic records show that on the early machine, both sets of these moving teeth were triangular, but on this improved modified version that one set of teeth were rectangular to assist in grabbing and cutting with wire.
Rebuilt prototype showing the new double wheeled arrangement and double turret arrangement during road trials 1917. Photo: Pignato
Modified prototype during off-road testing 1917. The rectangular section in the middle of the armour is an extension to the body, moving the cab forwards to cover the new pair of wheels. Photo: Pignato
Replacing the single Fiat model 1914 6.5mm machine-gun in a single turret was a response to the advice of the Army commission. Both turrets mounted a pair of Fiat machine-guns, giving the vehicle a total of five machine-guns. With both turrets fully traversable, the vehicle could bring at least 2 weapons to bear at any point around it, with up to 4 weapons firing across almost the whole frontal arc (save for where one turret gets in the way of the other).
The machine was essentially an armored tractor driven backwards by the engine at the back. This meant that it was actually steered by the rear wheels and without any changes to the steering mechanism, the driver seated in the front right would have his steering controls reversed when driving forwards. A left turn on the wheel would actually turn the vehicle to the right, which might be very confusing under fire. It is not clear how the controls were arranged as the driver would normally also have to be facing backwards, but the viewport on the front indicates that the position for the driver, rather sensibly, was moved to be forward facing. Perhaps the confusion was not so bad, as the speed, at just 10km/h unladen for the tractor with no load, and just 6km/h with the armored body fitted, was slow anyway.
The engine was too weak for the task of assaulting the enemy with just 50hp at 800 rpm from the 4 cylinder petrol engine, leaving this large machine in enemy sights for too long and would have rendered it extremely vulnerable. Combined with the very thin armor, the military value of the machine was very low and thus, the Army rejected it.
The Army had rejected the first prototype of the Pavesi Autocarro Tagliafili for being too slow and too poorly protected. The armament and armor had both been improved as had the off-road ability with extra wheels, but the inherent lack of engine power of the tractor it was based on remained and the need for the vehicle simply disappeared. Not because of the end of the War, but because other vehicles were now becoming available to the Italian Army for the same purpose. The Fiat 2000 heavy tank was being developed and was much better protected and armed as well as being more manoeuvrable. Small tanks, such as the Renault FT, were also beginning to show a lot of promise, carrying more armor in a much smaller tracked package, rendering the whole concept of the Pavesi Autocarro Tagliafili was obsolete. The one prototype vehicle was broken up for scrap. The First World War had been good for business for La Motoaratrice, but this was not one of their commercial successes.
Postwar, Giulio Tolotti left the firm and it was renamed and reformed from La Motoaratrice to La Motomeccanica (Brevetti Ing. Pavesi). Ugo Pavesi would also left the firm he had helped found in 1925, handing it over to Ezio Mazzagio. The firm changed names again in 1932 to Motomeccanica, but the firm continued to survive. Ugo Pavesi, however, did not, dying suddenly on 13th July 1935.
|Propulsion||4 cylinder petrol producing 50hp at 800 rpm|
|Speed (road)||6 km/h|
|Armor||3.5mm to 4mm thick steel|
|Total production||1 Prototype in two stages|
|For information about abbreviations check the Lexical Index|
Resources and Links
Gli Autoveicoli da Combattimento Dell’Esercito Italiano, Nicola Pignato
Machines of Pavesi, Claudio Pergher
La meccanizzazione dell’Esercito Italiano, Ceva and Curami
La Motomeccanica, Angelo Alpe
Chilton’s Automotive Industries Vol.37, July 1917
Motor Age Vol.32, November 1917
Oil field Engineering, Vol.18, December 1916
The Gas Engine, Vol.18, January 1916