Gunners and Drivers!!!
The main star of this film is a vehicle that was conceived as a true "stopgap", but which was so effective that it generated a whole line of first cousins, while the real protagonist was not ready... and as you know, War doesn't wait!! Now, let's get to know the simple but effective artillery tractor Full-track Prime Mover M33.
 |
| Always the same headache... modified from US Army photo M33 prime mover towing a 240 mm howitzer M1 "Black Dragon" into a firing position in Italy, 31 January, 1944. |
History
The displacement of artillery pieces around the Theater of Operations has always been a problem for armies, due to their large volume and weight. And when the parts to be moved are of large caliber, everything gets complicated. During the WWI, the use of animal traction was common, being used by most countries involved in the conflict.
 |
| Horses moving a 18-pdr. battery from Royal Field Artillery Western Front, 1914. font:National Army Museum |
The big problem with using animal traction on battlefields was logistics and the fragility of the animals. With the advent of increasingly larger and more powerful weapons (and therefore heavier...), the use of horses and other animals simply became unfeasible.
 |
| The big British 60 pounder gun needed 12 horses and troops to move it to Bazentin le Petit during the Battle of the Somme France - August 1916 |
With the advent of more robust, powerful and reliable motor vehicles, experiments began with tractors and trucks replacing animal traction at the end of WWI.
 |
| American Holt 5-ton Artillery Tractor Model 1917 pulling a train for an 8inch howitzer - 1918 - font: National WWI Museum - Kansas City - MO |
At the beginning of the Second World War, the use of horses as a means of traction increasingly fell into the background, until it almost completely disappeared.
 |
| German horses struggle through the Rasputitsa mud Operation Barbarossa - Kursk area - March, 1942. font: Bundesarchiv/101I-289-1091-26 |
The use of mechanical means to carry out this work is much more appropriate, due to their reliability and mechanical simplicity now developed. In the case of the American army, this was no exception, with the mechanization of artillery taking place in the period between the world wars. The first option was militarized agricultural tractors, as well as the use of heavy trucks with full traction. But for the sake of simplifying logistics, the use of vehicles with tracks derived from existing armored vehicles was the option chosen.
With the production of the new M4 Sherman medium tank unfolding in full swing and its introduction into American armored forces in mid-1942, the American Army decided to take advantage of the advantages and qualities of the now outdated M3 Lee medium tank chassis, being a tractor artillery would fit into this type of material reuse.
M33 prime mover
The first effort to produce an artillery prime mover based on the M3 medium tank was the T16 heavy cargo tractor, which was built around the M3A5 chassis. Although relatively promising, the lack of storage space and the poor crew protection were factors that doomed the prototype, and its series production was denied.
 |
| T16 heavy cargo tractor prototype - front view The crew was very exposed to the weather, without any cover except for a stretched tarpaulin. |
 |
| T16 heavy cargo tractor prototype - rear view Notice the Gar Wood 18.000 Kg winch in the rear. |
Meanwhile, Baldwin converted about 805 surplus mediums M3s, M3A3s and M3A5s in the T2 Tank Recovery Vehicle (M31).
With the rejection of the T16 heavy cargo tractor, the military eyes turned to the stockpiled M3s, but with the advent of the M32 TRV (based in M4 medium Sherman chassis) which were even more efficient than the T2 (M31), the American Army, instead of using "pure" M3s for conversion into an artillery tractor, decided use the T2 (M31) TRVs that were being replaced by the M32 TRV for the new artillery prime mover, until a heavy tractor fully designed for the task was ready.
 |
| A M32 TRV in action, lifting a M5 Stuart light tank |
As the T2 (M31) TRV already had an excellent winch, the designers chose to use this equipment on the converted tractor, as it would make it easier to tow and position the American army's heavy guns.
It was then decided that 109 of the radial engine T2 (M31s), mostly from the last 3 months of Baldwin's production, were knocked down and converted to prime movers by the Ford Motor Co. factory in Chester, Pennsylvania, at Chester Tank Depot, Army Ordnance Department. The production line for this vehicle was active from December 1943 to February 1944.
 |
| Mediums M3 Lees under construction at Ford Motor Company, in Chester, Pennsylvania. Chester Tank Depot - Army Ordnance Department. font: Philadelphia Inquirer |
The vehicle was officially designated as Full-track Prime Mover M33.
 |
| Full-track Prime Mover M33 Note the remaining characteristics of the T2 (M31) TRV still present on the tractor. |
Interestingly, the M33 prime mover was very similar to the "Heavy Tractor Cargo, T16", which was considered unsuitable as a prime mover for artillery. However, delays in the production of the much desired (and expected) heavy artillery prime mover specifically designed for the task, the M6 High Speed Tractor, must have caused a relaxation of evaluation criteria and the M33 was produced as an "interim" heavy tractor vehicle.
 |
| Tractor, High Speed 38 ton M6 font: US Army Technical Manual TM 9-788 |
The M31 TRV had the turret with the crane boom and all crane-related accessories removed, but the internal winch being retained. A commander's hatch ring as used on Sherman turrets was adapted to fit on the roof of the hull, above the 75mm gun sponson. This was rotatable, and appears to have served as an expedient mount for a .50 Browning machine gun. The armament arrangement resembles the same ergonomics used by the M7 Priest, with its "pulpit".
The photos available suggest that the hatches were not installed on the hatch ring. In the boxes on the rear deck, an air compressor was installed to supply compressed air to the brakes of the artillery pieces. Canvas covers were provided for the turret openings and machine gun ring.
 |
| A newly built M33 prime mover, displaying its canvas covers installed over its superstructure. Notice the .50 Browning MG also wrapped in canvas, installed on the hull ring. left view |
 |
| The same vehicle above, in other angle of view. The spare wheels have not yet been installed in the front of the hull. |
The M33 prime mover was used mainly by the heavy field artillery battalions deployed to Italy in the spring of 1944, including the 575th Heavy Field Artillery Battalion with 8-inch (203mm) M1 heavy howitzers and the 697th and 698th Heavy Field Artillery Battalions with M1 240 mm heavy howitzers "Black Dragon".
 |
8-inch (203mm) M1 heavy howitzer These howitzers used the same carriage as the 240mm M1 Black Dragon, hence the confusion in identifying the types Fort Sill, Oklahoma, USA. |
 |
| An 8-inch US Army field gun in action during the bombardment of Brest. 24 August 1944 |
 |
| 240mm heavy howitzer "Black Dragon" M1 Lewistown, Montana - Veterans Memorial Park |
 |
| Army soldiers of Battery B, 697th Field Artillery Battalion -5th Army, prepare to fire the 240mm heavy howitzer "Black Dragon" M1 into German-held territory near Mignano, Italy. Notice the gunners trying to protect your ears from the huge bang... January. 30, 1944. |
 |
| US M33 Prime Mover from the 5th Army 697th Field Artillery Battalion towing an 240 mm howitzer M1 (Black Dragon) near Cori, Italy - May 1944 font: LIFE Magazine Archives |
The conversion of the M31 to M33 was a success, thanks to its robustness, reliability and strength. As it was a derivative of the Medium M3, it was well known to the soldiers, who really liked the tractor, using it to the limit.
 |
| M33 prime mover towing a 240 mm howitzer M1 "Black Dragon" into a firing position in Italy, 31 January, 1944. font: US Army Photo |
Even though it is almost a "stopgap" vehicle, its usefulness has been largely proven and other recipes have been developed, with different vehicles. Due to shortages of the M31 for conversion, 24 M32B1 TRVs were converted into the M34 prime movers by removing its crane and specialist equipment, in a way very similar to the conversion of the M31 into M33, except that the M34 kept the turrets but there is little evidence this type was ever deployed into combat.
 |
M34 prime mover Notice the clear origin of the M34 from the M32, without the crane and its accessories. font: Catalogue of Standard Ordnance Items - 1944. |
Similar efforts were subsequently undertaken with surplus M10 Gun Motor Carriage and 209 were converted into the M35 Prime Movers from January to June 1944, by removing the turret and making a number of small changes on the hull. These first appeared in France in 1944 and were used by a number of heavy field artillery battalions including the 551st Field Artillery.
 |
| M35 prime mover from 7th U.S. Army towing an 8-inch gun toward the front lines in Eastern France - 1944 |
At the end of December 1943, some of the first newly converted M33 prime movers were urgently sent to Italy, accompanying two batteries of M1 240 mm heavy howitzers "Black Dragon". They went into action near Mignano, Italy, in late January 1944, causing great devastation with their enormous firepower. In April 1945, four 8-inch (203mm) M1 heavy howitzers joined to the Dragoons. These weapons were so large and heavy that a pair of three-axle, six-wheeled transport wagons were developed: one for the cannon tube, and one for the carriage, each of these sets being towed by a tractor.
 |
| M33 prime mover towing a 240mm Heavy Howitzer M1 transport wagon near Mount Porchia, Italy. 27 January, 1944 font: NARA |
 |
| US M33 Prime Mover from the 5th Army 697th Field Artillery Battalion towing an 240 mm howitzer M1 (Black Dragon) near Cori, Italy - May 1944 font: LIFE Magazine Archives |
 |
| Clark's Express, a 240mm M1 heavy howitzer being towed by an M33 prime mover near Cory, Italy, in May, 1944 . The name of the gun must be in honor of Lieutenant General Mark W. Clark commander in chief of the 5th American Army. font: LIFE Magazine Archives |
 |
| Another angle of the same convoy pictured above. Cory, Italy - May, 1944 font: LIFE Magazine Archives |
 |
| An M33 prime mover towing the 240mm heavy howitzer M1 barrel to new emplacement of fire |
 |
| The 240mm Black Dragon was so large that it required a crane to be lifted into position. The howitzer carriage being removed from its wagon and being lowered to its firing location |
 |
| Now, the barrel of the 240mm heavy howitzer being positioned on its carriage. Notice the M33 parked in the right corner of the photo. |
 |
| Gunners from US Army 698th Field Artillery Battalion with his M1 240 mm Heavy Howitzer in Italy. January, 1945. |
By November 1944, however, all 8-inch guns and 240 mm howitzers had been withdrawn from Italy and sent to the Western Front. The 240 mm howitzer saw extensive service in Europe, reducing reinforced targets requiring super-heavy artillery. Fifteen 240 mm howitzer battalions served in the European Theater; the 265th, 266th, 267th, 269th, 270th, 272nd, 277th, 278th, 538th, 539th, 551st, 552nd, 553rd, 697th, and 698th. Five served in the Pacific; the 543rd, 544th, 545th, 778th, and 779th.
Specs:
| M33 Prime mover - Full-track prime mover | |
|---|---|
| Type | Artillery tractor |
| Place of origin | United States |
| Service history | |
| Used by | US Army |
| Wars | World War II |
| Production history | |
| Designed | 1943 |
| Manufacturer | Chester Tank Depot converted from M31 |
| Produced | December 1943 to February 1944 |
| No. built | 109 |
| Crew | 6 |
| Specifications | |
| Mass | 27.200 Kg |
| Length | 564 cm |
| Width | 272 cm |
| Height | 220 cm |
| Ground clearance | 44 cm |
| Armor | Rolled homogenous steel - riveted front: 5,1 to 3,8 cm sides and rear : 3,8 cm front floor: 2,5 cm top: 1,3 cm. |
Main armament | 1 x M2 Browning machine gun with 600 rounds |
| Engine | Continental R975 C1 radial engine 400 hp @ 2,400 rpm |
| Transmission | Syncromesh 5 fwdx 1rev. |
| Suspension | VVSS |
Operational range Fuel capacity | 240 Km 700 liters (gasoline) |
| Maximum speed Max trench Max grade Max vertical obstacle Max fording depht | 40 km/h (road) 25 Km/h (off-road) 230 cm 60% - 31° 61 cm 110 cm |
The kits:
Well, for this project, I had at my disposal the resin conversion kit from Des Kit M33 Artillery Tractor (#35138)...
 |
| Sorry about this print of the Des Kit website... I couldn't find a photo of the kit cover anywhere... and my kit came with the photo torn... Notice the Takom kit quoted above as host kit |
and the kit indicated by Des Kit itself as the ideal host, the excellent and detailed M31 US Tank Recovery Vehicle (#2088) from Takom.
 |
| Box art for M31 US Tank Recovery Vehicle kit (#2088) - Takom. An amazing and detailed kit... |
But upon opening the boxes, I found it almost a waste to use a kit as delicate and with so many details as Takom's M31 TRV to make a simple, uncluttered tractor. But I'm the Indiana Jones of modeling world: my warehouse of old models is infinite!!
 |
| Me keeping a few more boxes in my wharehouse of virgin kits... |
I remembered that I have an old (2008), dusty and renegade kit Academy M3 Grant (#13212) virgin in the box.
 |
| Box art of the hated (but excellent...) Academy M3 Grant (#13212) kit |
This kit was cursed by fellow modelers because of size (very high) suspension VVSS bogies, which disgraced the history ( and the sales...) of this model. But the kit is excellent, with a very well detailed interior, which would really come in handy for this project.
"BUT WHAT ABOUT THE COMPLETELY WRONG SIZE OF THE BOGIES??" - scream madly the most devout, orthodox and fanatical purists...
 |
| WRROOOONNNGGG WAAAY!!! |
And I simply and candidly respond: "I have scrap bogies from old Tamiya M3 Lees projects". But the horde, enraged and volatile, roars even louder: "HERESY!!! Tamiya's M3 Lee bogies have the wrong wheels...BURN THE BLASPHEME!!!"
 |
| Burn the weirdo! - Highlander movie |
...and I reply: "...but I have perfect Academy M12 SPG's bogie wheels in my spare parts box!!" And with last argument, I silence the most bubbly rivet counters!!!
But aside from the colorful aspect of the problem presented, I'm going to use the Academy's M3 Grant as a host for the Des Kit conversion kit, to make the M33 prime mover... and I'll use the M31 TRV for a new project (but that's another story...).
So, enough chit-chat and let's have some fun (it's so nice to do something out of the ordinary for a change...).
Let's start by the most controversial: the replacement of the "tall" Academy bogies with the correct Tamiya bogies:
 |
| Notice the details in the bogies: Structures (dark green) from Tamiya, return rollers (cream) from Academy Grant and road wheels (olive green) from old Academy M12 SPG kit... That's what I call a mix!!! |
Notice above that I already exchanged the Tamiya wheels (which have six holes) for the correct Academy ones (with 5 holes). Piece of cake!!! That's the kind of thing Kojak loves!!!
 |
| The Tamiya bogies in the Academy lower hull... Like a glove!!! Right side |
 |
| Left side |
And now, an interesting discovery: many Des Kit parts are resin copies of the Academy parts. This made me much more at ease in my choice to use the Academy kit, instead of the Takom kit, as a host kit... and as there are many plastic parts identical to those in this kit, I will use the best detailed ones... Nothing like If you have a double option...
 |
| Resin and plastic, side by side |
 |
| I choose use the floor from Academy, in plastic...much better as well as other transmission parts. I will use the cardan tunnel cover in resin... The model will be a true Frankenstein... |
 |
| Driver's bench and levers are resin copies of the Academy kit. Of course I'll use the plastic ones: much easier to clean and glue!!! |
 |
| Right view of the tank floor |
 |
| Front details and real armour in place... The colors of the different piarts are extremely aesthetic!!! |
 |
| The Academy kit is a beauty for this conversion!!! |
 |
| The floor fits like a glove!!! The resin one was a little warped, but it was a copy of this plastic one, perfect... |
 |
| Really, I'm very happy with my choice!! |
When I went to build the hull winch, I had a terrible surprise: many of the levers were broken and some small parts were simply not present in the Des Kit kit. Fortunately, the most important and visible ones were ok... As I am very far away from the supplier, it is easier and faster to build from scratch than to request (and receive...) replacements. I want to see this girl ready soon!!!
 |
| Notice parts in plastic (white) in scratch... The winch is very detailed... The steel wire rope was made with thick waxed thread (no hair). I liked... front view |
 |
| Winch of the hull. Rear view |
 |
| The winch in position, in dry-fit... Perfect!! Notice the firewall (again, I used the plastic one, much better) glued in position. |
 |
| The kit is very interesting!!! |
And again, I chose to use the Academy parts instead of the Des Kit resin roof, as I would have to modify the model's assembly "engineering" a lot. The roof was designed for the Takom hull, which is a very similar size to the Academy, but with a completely different construction sequence. Here, I will opt for the Academy, forgetting the steps of the "Takom line". The only thing I'm going to do differently is open the hole in the roof of the sponson of the 75mm cannon from the Academy kit. Easy as slapping a drunk!!!
 |
| Academy parts in cream color. Notice the hole for the .50 Browning in the roof of the 75mm gun's sponson. Using putty to seal the injection pin marks, which may be visible... |
The Des Kit resin welded side door (in gray) is a copy of the Takom plastic piece. Notice the slight dimensional difference between Academy and Des Kit doors. I will use the resin part, removing the plastic details (hinges and latches) on the sides of the Academy kit hull.
 |
| Academy details which will be deleted with a scalpel (red arrows) and the door welded from Des Kit in resin (green), an exact copy of the plastic door from Takom's M31 (which will be preserved for the other project). |
 |
| The Academy's upper hull, completely built down to its most important structural parts. The door on the left side (welded) is the late type of the M3, that is, without the pistol port. |
The welded resin door supplied by Des Kit, on the right side, has the pistol port, but does not have the internal details. I glued the original Academy door in place and after, I will abrade the entire external surface (with a Dremel abrasive rotary tool), so that I will preserve the internal details of the Academy door. Over the "mess" caused by the external wear of the Academy door, the right door from Des Kit was glued on, in resin. This way, I will have the best of both worlds...Notice the plastic "graft" (dark green, below) in the opening of the 75mm cannon: this piece is cut from the same sector of a Tamiya Lee hull, scrap, to better adapt the door with the dummy gun of these models...
 |
| The right door from Academy glued in place (red) Notice the Tamiya graft in the base of gun aperture... |
 |
| Internal view of the left door welded, with no pistol port Absence of details... |
 |
| The right side: details of pistol port and plates "welded" in the sides (red). The Tamiya graft in the base of gun aperture (blue arrow) |
In the sequence of photos below, the red arrows point to parts of the ki that were not present, that were missing. Many were made with plastic and some are reused parts from my scrap box, based on the (bad) photos of the kit being assembled in the Des Kit instruction manual (which is terrible...simply ridiculous!!). This stage was very challenger, but I think I (and Kojak...) managed to overcome the problems effectively.
 |
| Installation of cabinets (in resin) on the sides of the tank sponsons and parts that were made or reused from others in the red arrows. Shame on you, Des Kit!!! |
 |
| The most complicated part was reproducing the winch's small transmission box, with its small cardan shaft (in gray), but scrap truck parts solved the problem satisfactorily... See above and below... |
 |
| Kojak had a lot of fun at this stage!!! |
 |
| The drawer cabinets from Des Kit are very well made... |
But after this true reconstruction of the interior of the M33, we will paint the entire internal area, so we can "close" the upper hull and continue the project...
 |
| Painting the upper hull internally and externally with primer (light gray, from Vallejo). Notice the right welded door (with pistol port) in resin, in place... |
 |
| Upper hull, left side. Notice the late style of side door (no pistol port) |
 |
| The interior, in light gray primer Vallejo. front left view |
 |
| Front right view... The internal details, after being painted, look "original" from the factory!!! |
 |
| And now, let's age the fruit!!! Weathering with oils, pigments and washes... front left view |
 |
| Internal weathering... front right view |
 |
| Weathering the winch. Notice the braking band, made of reinforced canvas, painted in khaki. The scratch details looked very natural... |
Other details made with scratch and spare parts, such as the front tow hook and its support (red arrow). The Takom kit has these parts, but they will be preserved for the other project...and the Des Kit does not supply them, as theoretically, these parts would be available from the M31 Takom kit recommended as host... With patience, everything will be resolved!!
 |
| Closing the hull with glue. Repair the front tow hook structure, in scratch and spare part (red arrow). |
 |
| Closing the upper hull. The sponson door is in resin (dark gray), from Des Kit conversion kit. |
 |
| The upper hull closed. Rear view |
 |
| Sand shields in position. Academy parts! Perfect!! left side view |
 |
| Hull closed. Right side view |
Continuing the construction, let's now make a dummy cannon, to be installed in the front armored door of the kit. I will use a styrene tubing from Plastruct, 3.2mm in diameter and 35mm long. It will be installed at a slightly upward angle, as shown in the photos of the original vehicles.
 |
| The material for the dummy gun |
And now, a spoiler: you will see in the photo below, in background, the object of my new project, which is the construction of Takom's M31. I am building the M31 in parallel to the M33, as many of the M31 parts serve as dimensional models for the missing parts for the M33. The example below is typical: the tool and air compressor boxes on top of the rear deck. I use the Takom parts as guides for the ones I'm going to make from scratch, using 0.5mm thick plasticard.
 |
| Building rear tool boxes in plasticard (green arrow), with the example of the Takom piece. The M31 you see in the background... Notice the dummy gun in position. |
 |
| The Takom and Academy kits are dimensionally very similar... Therefore, the Takom boxes are perfect as "masters" for the Academy hull. |
 |
| Using Takom boxes as a model, scratch work becomes much easier. |
 |
| Tool boxes in place and other details... |
 |
| The gunner girl is getting very cute... |
 |
| Rear left view |
 |
| Installation of the rear tow hook and its reinforced base. This piece was scratch made with plasticard, based on the Takom piece. The dark green hook is a spare part. |
 |
| A few more details added: some are reused pieces from my scrap box, others made from scratch: Sherman cupola ring Italeri (yellow) Boxes with track link grousers Dragon (red) Rear rack (green) scratch Notice the radio antenna, made with acupuncture needle The tracks in vinyl (blue) are the Academy ones, very good... |
 |
| The tractor really looks massive... |
 |
| A .50 Browning machine gun will be installed in the cupola ring, on top of the 75mm sponson. Notice the tracks, in position... |
 |
| The rear rack, made with plasticard and Tamiya return rollers (the ones left over from the bogies, remember??) |
 |
| Making some steel wire ropes (blue) and testing some Value Gear rollbags and crates (green), to give the vehicle a more realistic look... The track links racks (red) are spare parts from Dragon |
 |
| The machine gun mount (red) is Tamiya Steel wire ropes (blue) in scratch and Value Gear stuff The spare road wheels are Academy |
 |
| The Value Gear material fits perfectly... The girl is practically ready!! |
 |
| The gunner sergeant is very pleased!! |
Sorry, but I lost some photos of this stage... My machine got a bit "stuttered", but they were generic images, of the model's primer... I managed to save this one|:
 |
| The M33 with olive drab primer, from Vallejo. Notice some accessories being primed in light grey... |
And now, the most important part: the colors and markings of our girl. I placed our hypothetical warrior in Italy, in the Mignano region, at the end of January 1944 (Battle of Monte Cassino). She is under the command of Lt.General Mark W. Clark, of the 5th American Army, serving with the 697th Heavy Field Artillery Battalion, towing the huge M1 240mm Black Dragon howitzers. This tractor belonged to Battery B and has the suggestive name of BABOON.
 |
| Panzerserra Color & markings guide |
 |
| Accessories and applied details. Lots of origins here, from my scrap box. |
 |
| Value Gear, Italeri and Academy stuff... |
 |
| The .50 Browning is Academy spare part |
And after some more details, I can declare the M33 tractor project ready. Meet BABOON, the Full-track Prime Mover M33, belonging to Battery B of the 697th Heavy Field Artillery Battalion, 5th American Army, during the Battles of the Conquest of Monte Cassino, near Mignano, Italy, in late January 1944.
 |
| Full-track Prime Mover M33 -BABOON - Battery B 697th Heavy Field Artillery Battalion - 5th American Army Battle of Monte Cassino, near Mignano, Italy - late January 1944. |
 |
| Full-track Prime Mover M33 left side view |
 |
| Full-track Prime Mover M33 rear left side view |
 |
| Full-track Prime Mover M33 rear top view |
 |
| Full-track Prime Mover M33 rear right top view |
 |
| Full-track Prime Mover M33 right view |
 |
| Full-track Prime Mover M33 right top view |
 |
| Full-track Prime Mover M33 front right view |
 |
| Full-track Prime Mover M33 front right view |
 |
| Full-track Prime Mover M33 front view |
 |
| Full-track Prime Mover M33 with Kojak |
 |
| Full-track Prime Mover M33 top view |
 |
| Full-track Prime Mover M33 -BABOON - Battery B 697th Heavy Field Artillery Battalion - 5th American Army Battle of Monte Cassino, near Mignano, Italy - late January 1944. |
You must be wondering: But what about the 240mm Howitzer??
 |
| Des Kit (#35139) box kit |
Calm down, guys... it's on the way... Soon, we'll have news...
Stay with us, Folks!!!
