Introduction: Military Model: Scammell Pioneer R100
A conversion by Neil Craig from Military Modelling Magazine.
The British Scammell Pioneer R100 was a Heavy Artillery Tractor used in the Second World War. The basic vehicle was used to tow heavy artillery such as the 7.2 inch howitzer. It had an 8-ton winch and an overhead runway with a 10-cwt hoist. The Scammell was powered by a Gardner 6LW six-cylinder diesel engine with a 6X4 drive, six-speed transmission and front transverse leaf springs suspension. Development of the basic vehicle included the Scammell Semi-trailer Tank Transporter and the Scammell Pioneer SV/2S Heavy Breakdown tractor. 768 units were produced from 1937.
Weight 8509 kg
Engine capacity 8369 cm3
Dimensions 6274x2591x2972 mm
Wheelbase 3708 mm
Brakes Mechanical-assisted Rear axles, wheelbase 1295 mm
Step 1: Research
The model is a conversion based upon the Airfix Scammell Tank Transporter. The conversion was inspired by information from Stuart Harrison on the Airfix Tribute Forum and Sean Brannin and details on the Pioneer Recovery Vehicle on both the Airfix Tribute and Braille Scale Forums. Correspondence with Stu and Les Freathy yielded many plans and pictures with the closest plans based upon the Scammell company plans in 1/76. One of the articles sent to me had a great article on the R100 and 7.2 Inch Howitzer. It also gave a description of how to do this conversion. I decided not to include the engine but instead concentrated on a detailed crew and rear compartment.
Step 2: Cab Floor
The Airfix cab is 1.5mm short but rather than scratch-build the entire cab and body, I decided to use the Airfix parts as the overall look of the vehicle is spot on. The frame and floors were assembled as one sub-assembly and the body built up separately. The build sequence is described below by sub-assembly - although some of the sequences changed throughout to facilitate the build. Firstly I cut the chassis to the right length with the join just under the cab floor and I modified the floor area. I shortened the cab floor by cutting across, it right behind the seats and I then cut off the moulded in seats covering the resulting holes with .010” sheet. A5mm high cab back was added behind the floor, leaving a cut-out on the right side of the driver’s seat as the access to the crew compartment. The moulded seat backs were cut off and added to the backboard. The seat’s tubular frames were constructed with .010” sheet some strip and .016” brass wire with cushions made from .020” sheet.
I next tackled the gear shift guide, it features prominently in cab photos and sits between the drivers and crew seats. It was made using - .010”x.020” strip and fitted between the seats. I inserted a length of .020” rod for the gear stick with a blob of white glue for the knob.
Step 3: Chasis
The plan showed that the chassis frame would have to be shortened to ensure that I could use the locating holes for the rear springs. It also showed that the frame would have to be lengthened behind the rear wheels. The frame was shortened by removing 11 mm from the middle of the frame and then these pieces were shortened to 8.5 mm and added to the rear. I added the rear tow bar assembly a little lower than the frame and moved the locating crosspiece for the three winch cable pulleys to the rear.
All the joints were reinforced with .020”x.040” strip on the inside of the frame and it was left to dry overnight. The rear springs were glued to the frame in the locator holes and the transmission/driveshaft part was glued to the rear axle. The radiator was glued in place and next the bonnet, cab front, cab sides and roof were assembled, but not glued to the floor. Once complete it was set in place on the frame against the back of the radiator as a template and the cab floor was slid into it and glued in place. With the cab floor in place, the engine bottom/drive assembly was now cemented in position.
The outer rear wheel suspension was added to the rear axle on each side and left to pivot. Additional frame supports were added using .040” rod and .020”x .030” strip. The older style horizontal spindle winch assembly was constructed using tube, rod and strip and glued in place on the top of the frame. The rear winch cable pulleys were glued in place and fairlead rollers were constructed from rod and strip and added to the pulley frame. Winch cable guide pulleys were added to the left side of the frame and a two sets (two horizontal and two vertical) guide rollers were installed on the front left side of the frame.
The fuel tank was modified to sit a little further forward with a new filler neck and cap added and when the tank was in place a bracket was added. The chain carrier was also modified to the correct shape and detail added. The door was scratch built using .010”x.020” strip. (An additional bracket from the front of the carrier to the cab front will be added just prior to painting.) The steering arm linkage was scratch-built using strip and both .015” and .020” Rod.
Detail was added to the front towing bar assembly and the headlights were modified and added to the frame. The front mudguards were cleaned up and glued into position. Further detail was added to the cab floor; winch levers and handbrake, brake and clutch pedals.
Step 4: Cab Front
The radiator had bolts, made using .015” and .020”, rod added on the top and three on each side. The bonnet sides were detailed with an indentation along the upper edge. The razor saw was used to cut about 1.0 mm deep just under the lip of the bonnet top on each side. Then a 50 degree cut was made 2.5 mm long angling upward to the previous cut. Once removed it was filed and sanded smooth. The raised rectangular embossed area was made using .010x”.010 strip and .040 rod cut off at roughly 1.0 mm and cut in half to represent the two lifting grips on the top of each side of the bonnet. I added rivets on the face of the cab based upon the drawings. I then sanded off all the raised detail and rivets on the roof and cab sides leaving just the forward part of the cab. Using the cab floor as a template, I glued the sides and roof to the cab front and left it to dry. I then added the air filter on the cab front right side and 2 small square details on the top portion. Next I assembled the front axle to the chassis locking it in place with the radiator. Gaps in the cab front were filled using Squadron putty and left to dry completely prior to sanding.
Step 5: Wheels
I started on the wheels by adding .010” sheet to the middle to give a bit more width and then using .010”x.020” strip, re-treaded the tyres into the correct pattern for the Pioneer. The first one was a challenge but the rest came much easier and the results look good. The hubs were rounded off and added to each wheel followed by additional bolts using .015” rod.
Step 6: The Body Interior
The crew compartment and storage area were the next areas to be tackled. There are 3 levels shown on the plans including a box under the front crew bench to accommodate the winch. The first step was to add 3 horizontal support beams to the chassis using .020” sheet cut into 3mm strip. The different levels were constructed using .010” sheet and 9 seat cushions and backs were made from .020” sheet for the crew compartment. The front wall of the crew compartment was built up using strip and a slot was made for the floor to slide into. The ammunition rack was added with two rounds made from tube and putty.
Step 7: Cab Interior
Cab details were added including the instrument panel, gas pedal and other detail. The doors were outlined in strip and handles added. At this point the glazing was also cut to size. The steering wheel will be added after the back portion is added.
Step 8: Body
This was probably the most challenging part of the conversion. Measurements were taken and the pattern of the rear part of the body was drawn on some .010”a sheet and carefully cut out. I used hot water to soften the material and bent it around a piece of tubing to form the sides. With a rough shape I started gluing the front edge to the back of the cab using ACC - for speed of drying. I then used glued the tailgate in place and once set I added the kit rear curtain to the upper part of the rear opening. Once dry, I took the rear roof of the tractor - which had been cut away earlier to make the arch supports for the interior. I sawed off three 1.5mm cross sections modifying the ends slightly to fit and glued them in place. I then glued longitudinal stiffeners down each side and in two rows in the roof. The rear four crew seat backrests were added on the longitudinal stiffeners on each side.
When checking for fit between the chassis and rear body I soon realised that the body interior sub-assembly would need to be glued in place. Although it would hide some detail like the winch, I decided this could be painted later. The joining seams were next to be added using 010”x.020” strip. This assembly was then sprayed with primer to show up any imperfections. The crew compartment floor was cut to fit the geometry below the crew doors. This greatly improved the look with the body in place. The small locker under the crew doors was made from strip and glued in place on each side. The rear mudguards were made using .010” and .005” sheet and will be added just prior to painting.
I constructed the wheel chocks from .010” sheet. The plans indicate that the top of the benches in the rear of the body extends outwards and are flush with the bottom of the sides. I cut away 6mm of bench and built a box over it to accommodate the chocks. An old lead toothpaste tube provided the material to make the brackets and all was glued in place on the underside rear of the wheel wells.
The ladder which provided access to the rear was constructed using .015” rod and was added just prior to painting as it is fairly delicate. Next I built the gantry beam from strip. I set it in place after filing out a notch in the rear curtain to accommodate it. I then glued tri-angular clamps in place either side of the beam on two of the arch supports. The beam was then removed to make the hoist which was built up using strip and rod. Small scale chain was used to make the working component of the hoist. A hook was made from .015” brass wire. The whole gantry assembly was then set aside to dry and added later with the same chain used to make the safety chains for the tailgate.
Rolled tissue strapped with the lead foil was used to make the side curtains for the crew window openings. The same tissue paper was used to cover the plastic rear curtains to give them some texture to simulate canvas. As a final touch, new side lights on the cab front were make with rod and strip (the kit ones were broken off during handling) and the side mirrors were also made from .010” rod and .010” strip.
Step 9: Painting
I primed the completed model with flat black. This serves to pre-shade recessed areas and ensure coverage of all the bare plastic. I decided my model would depict a combination of tractor and gun used by the 54th Heavy Artillery Regiment of the British 1st Army newly landed in Algeria for Operation Torch in 1942. A string of e-mails with Mike Starmer revealed that 1st Army vehicles going to North Africa would be in the SCC2/SCC14 combination in the patterns laid down in MTP 46/4A, hence Khaki Brown with Black (or Very Dark Brown SCC1) on the top surfaces of the tractor with the gun in overall SCC2. Using the SCC2 colour chip in one of Mike Starmer’s excellent books, I mixed a close match to the chip using Humbrol H29, H98 and a touch of H18 Brass paints tinted with some Windsor & Newton Oils. This was airbrushed onto both the R100 and the 7.2” Howitzer (a Hinchcliffe model.) This was left to dry for a day while I made masking tape masks to cover the SCC2. After these were applied, I sprayed the SCC14 Black. The gun was left in base colour SCC2.
The decals I have chosen to use were based upon an internet photo of the magnificently restored “Boadicea”. They were custom made by Peter Marshall of Aleran Decals in Detroit. The markings show it to be a vehicle of an artillery unit attached to the British 1st Army which was basically raised to go to Algeria and Tunisia in 1942 for Operation Torch. As information is sketchy on individual unit serial numbers, I am using “artistic license in assuming unit “254” was the 54th Heavy Artillery Regiment equipped with 7.2” Howitzers.
When this was dry, an overall coat of Gloss Varnish was applied for decal adhesion and pin washes. After drying for 48 hours, pin washes were applied using thinned oil colours mixed with a little of the original SCC2 mix. Decals were then applied and after, Testors Glosscote was applied by brush around the edges to help seal them and the whole was sprayed with flat varnish and left to dry to facilitate dry brushing and detail painting.
After these stages were complete the vehicle was assembled and set on the base.
Step 10: The Base
As the model is depicting a tractor/gun combination of the British 1st Army, I thought it appropriate to portray it in a typical North African setting of a desert track. A search on the web produced photos of desert settings and greenery as photographed in Tunisia and Algeria. The base was made up in my usual manner of a stained wooden plaque surmounted with florists Oasis block surrounded with .020” sheet plastic painted flat black. Once in place, dry and masked, a model wheel was run from one end to the other a few times to simulate wheel tracks. A coat of white glue/water was painted on and gravel was sprinkled on. Small stones were added randomly here and there. After drying for a day or so, it was painted in various hues of desert tones using thinned oil colours (Burnt Sienna, Yellow Ochre, Raw Umber and White). Successive coats were lighter to highlight the roughness. When dry, small clumps of Woodland Scenics Light Green Extra Coarse Turf were added here and there in accordance with the photos of North Africa.
Step 11: Thanks and Acknowledgements
The model took considerable research and I am grateful for all the information from Stu Harrison, Sean Brannin, Les Freathy and Mike Starmer. Finally, my thanks to Tom Cole for editing my original article.