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1941 Australian Ford 4 x 2 Tractor & 7 Ton Bow Front Semi Trailer - Scale Model World
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Home arrow Articles arrow Softskins arrow 1941 Australian Ford 4 x 2 Tractor & 7 Ton Bow Front Semi Trailer
1941 Australian Ford 4 x 2 Tractor & 7 Ton Bow Front Semi Trailer PDF Print E-mail
Apr 20, 2010 at 09:34 PM
Cliff Hutchings brings us another great build article, this time on the:

1941 Australian Ford

4 X 2 Tractor & 7 ton Bow Front Semi Trailer

This is Part 1 of a 2 Part Article

Thanks Cliff

Al

Copyright retained on text 2006@Cliff Hutchings 

Copyright retained on colour photos 2003/2006@Cliff HutchingsTractor Unit 01

The Start 

 

While browsing on line through one of my favorite photo archives at the Australian War Museum, Canberra ( http://www.awm.gov.au/ ) I discovered a photo showing an unusual semi trailer unit loaded with barrels in a convoy on the North/South Military Road (Now the Stuart Highway) in the Northern Territory, Australia C.1942. 

The photo was pretty dark but the tractor unit appeared to be a conventional Ford truck but with a GMC-CCKW open style military cab on it. This started a major hunt for information which lead to a surviving closed cab model located in South Australia and a friend, Bob Moseley, kindly took plenty of photos and crawled over and under it taking measurements for me. Bob also found a surviving semi trailer and once again sent me photos and measurements of it as well. So between AWM photos and the photos & measurements from Bob the work began.

History

The Australian Imperial Forces (A.I.F.) during WW2 adapted and used a lot of different types of vehicles both Modified Civilian Pattern (MCP), which were mainly 2 wheel drive, and Military 4 wheel drive. In 1941 they purchased from Ford Australia, 3 ton, 158inch WB, 4X2 trucks to be used for the purpose of tractor units with 7 ton semi trailers attached. 

The early production models were closed cab but the later orders were canvas topped models. All shared the front bodywork, from the front door pillar forward, and mechanical specifications of the civilian Ford truck except for an Eaton 2 speed rear axle that the Army specified for all types of MCP trucks. Now the trailer units were semi-permanently attached to the tractor units, the turn tables being totally different to the ‘fifth wheel’ on tractor units today. It took considerable effort to separate the trailer from the tractor.

Once Japan entered the war and advanced to the stage of being able to bomb Darwin in Northern Australia it was decided that military supplies for that Northern area would be sent by rail to Alice Springs in the Centre of Australia and then by truck through to either the Northern Territory railhead at Larrimah or all the way to Darwin. This road north from Alice Springs became the North/South Military Road (Now the Stuart Highway). In 1941 however the road was only a ploughed fire track through the scrub. Vehicles starting off as brand new at Alice Springs arrived at their destinations as wrecks missing mudguards, Doors and bonnets as these had cracked & fallen off with the vibration to be discarded by the track.

 

Ford engineers traveled up to Alice Springs at the request of the army and told to find ways of making the trucks last the distance. The modifications that they made were then incorporated into all future production of these trucks at the Ford Plant.

 

During the earlier research I discovered a book called “Convoys Up The Track” by Alan Smith, who did 56 return trips up the track. He stated that a lot of back loads on the return trips were made up of empty 44 gallon drums and that is what the original AWM photo was showing. This book is well worth reading.

Part One – The Tractor Unit 

The build

I was fortunate some time before doing the research for this model to have taken a lot of detailed photos of a MCP Ford 3 ton GS truck using a 50mm square piece of white plastic to sit on or beside the part I was taking photos of. This white square then gave me a reference point to scale off the photo and was essential to making the front bodywork to scale.

Chassis

Tractor Unit 02

A chassis was made from styrene strip the right scale width & depth for rails & cross-members. All measurements were either scaled off lube chart diagrams or copied from photos I had taken. The joint between the rail and cross-member was then drilled and a brass pin inserted to add strength. I did not use a ‘C’ section chassis rail due to the lack of strength in this type of chassis rail made from styrene.

Springs

The rear main & over load springs were made using a brass strip for the top leaf and styrene strip for the rest. The brass top leaf was given a slight curve and the styrene strips CA glued to it. Fine styrene strips were used to form the clips and a piece of brass rod added to act as the bolt that secured them. A piece of styrene rod was used to form the rolled ends of the main springs.

 

Front springs were made the same but the brass strengthening strip was put as the second spring leaf down rather then the top one as the main spring leaf was the second one from the top.

 

Spring mounts were made from tube cut in half with a small piece of sheet styrene added to the end. These were positioned on the chassis to give the correct scale wheelbase for a 158 inch wheelbase chassis (115mm).

Axles

Tractor Unit 03

 I was fortunate with the rear axle as the Australian Army used a two speed Eaton rear axle rather then the original axles in most of their MCP trucks, be they Dodge, Ford or whatever. Some of the vehicles I took detail photos of had these rear axles fitted and I had taken a few good photos of them. This meant it was relatively easy to make the rear axle with styrene rod for the axle tube and punched out styrene circles to make the diff head itself. This was then filed, scraped and sanded into shape and details glued on.

Tractor Unit 04

The front axle was made by cutting a piece of flat styrene to shape and then adding a top and bottom piece to form an ‘I’ beam axle. I did find this a bit weak later in the build and had to repair it several times.

 

Brake drums were modified from some Tamiya GMC ones that were in the spares box. Pieces were glued to the back to widen them and these were then fixed to the ends of the axles. Axle centers for the drums (outer ends) were cut from some resin wheels that had not formed correctly in the mold but were kept for just this purpose. Thin wire was used to represent brake lines on the front.

Steering

The steering arm between the wheels was made from brass wire with the ends off a similar piece from the spares box added. A steering box was made from a block of styrene and the steering wheel shaft was a piece of heavy brass rod. This was slid up into the cab through the firewall once the cab was assembled. A steering wheel from the spares box was used to complete it. A spare steering arm from an Italeri kit was used from the steering box to the axle hub.

Wheels 

Tractor Unit 05

 The tread was removed by sanding the tread from a set of Tamiya GMC wheels and then the wheel centre was removed as the GMC/Chevrolet wheels had 6 slots and the Ford wheels 5 slots. New centers were made by gluing layers of styrene washes made by using a punch set and sheet styrene. These were shaped and drilled out by hand. Thin strip was then glued to the tyre to form a ‘Civilian’ type tread pattern. Once one wheel was made it was posted to a friend who made a set of copies in resin. Grandt Line nuts were added to the resin wheels once it was known whether they would be front or rear wheels.

V8 Motor

Tractor Unit 06

 I was going to use the motor out of a Tamiya Quad Gun Tractor kit I had in my stash but decided that as the rest of the truck apart from the load was to be scratch-built I may as well build the motor as well, you know a nice detailed motor and leave the bonnet up or have the bonnet being able to be removed so it could be seen. (As you can see I am a sucker for punishment)

 

I started out by cutting sheet styrene roughly to shape and glued the pieces together to form the block. While this dried I made the heads from sheet styrene and added Grandt Line nuts and brass rod to act as spark plugs. Circles were also punched out and layered to form the bell housing and gearbox. Once the glue dried files, sandpaper and scalpel blades were used to shape the parts. The heads were added and inlet manifold, front pulleys and other engine parts made & fitted. Exhaust manifolds, carburetor and air cleaner were from the spares box. Once complete the motor was fitted to the chassis.

Miscellaneous parts

Tractor Unit 07

The fuel tank was made from styrene tube and strip. The tool box and platform behind the cab were made from sheet styrene and suitably scribed to look like boards. Grandt Line bolts and rivets were used to detail it.

Tractor Unit 08

The drive shaft was styrene rod with end joints from a kit item in the spares box. Rod was used to form the exhaust pipe/s and bent using heat and a piece of tube formed the muffler. Brass rod was used to represent the linkage between the cab and two speed rear axle

Tractor Unit 09

I was in a quandary about the semi-permanent turntable for the trailer connection as none of the photos I had showed one clearly and the South Australian Truck was missing this part. I improvised and made it to ‘look right’ from styrene and brass wire, separating it between truck & trailer so the model was easier to store and carry as two pieces. In the event that I was wrong and new information was found about this connection it would be easy to change. (This did occur at a later date). Running boards are sheet styrene with half round moldings placed as slip resistant tread. Front bumper and taillight unit are also shaped styrene pieces.

 

Bodywork

 

The Bonnet

As I considered that this was going to be the hardest piece to make due to the compound curves I started this piece first. Measurements were scaled off some photos for both the length and width at the back and the front. I found a spare Tamiya LRDG Chev bonnet in the spares box and cut this up to form the top and the curved edge. A piece was added into the centre and side panels and a nose section glued on. The louver vent panels in the side were scribed in before fitting to the top. Filler was then used around the nose and when this was dry it was sanded to shape. Half round stock was used to form the decorative strips on the sides and in the centre.

 Tractor Unit 10

Tractor Unit 11

This sounds easy now but at the time it took 4 or 5 goes to get this right and my wife got tired of being shown the ‘new’ bonnet so often.

 

The Grill

This part also took numerous tries to get the angles right and was replaced by a new one even after the cab was built and fixed to the chassis. The bulk of the surround was made using pieces of styrene and holes were drilled to accept brass rod as the bars in the grill. Filler was used to get the correct shape of the front. A radiator was also made at this time using layers of sheet cut to size. PE mesh was then added to both sides to form the radiator core. 

Tractor Unit 12

 

Firewall/cowl & Cab

I had some time ago modified an Italeri GMC cowl and windscreen frame by widening it and adding a part firewall to use on the Tamiya LRDG Chev kit. This was then cast in resin and some added to the spares box for future use.  One of these was modified by replacing the cowl side panels and adding a full firewall. The top of the cowl where the bonnet fitted was reshaped by using Apoxie Sculpt 2 part filler. I left this slightly high and then dipped the bonnet in water and gently pressed the bonnet into the wet filler. The water stopped the bonnet sticking to the filler and the marks left gave me a good indicator of where I had to finish the filler to once it dried.

Tractor Unit 13

A new dashboard was made with an instrument panel and glovebox cut carefully from thin sheet and brass wire as switches. This was fitted into place with spacer blocks and filler added between it and the windscreen.

Tractor Unit 14

Assembly

The radiator was fitted to the front of the chassis and Styrene rod formed the twin top radiator hoses to the motor which had been detailed with thin copper wire threaded into a small diameter rubber tube to act as ignition wiring from the distributor to the spark plugs in the heads. The grill was then fixed to both the radiator and the chassis. The bonnet was held by hand onto the firewall/cowl and then this was carefully placed onto the chassis by lining up the bonnet with the grill. The chassis was marked at the position the front door pillar would have been and then the measurements were checked against those scaled from photos. These were found to be OK so the cowl was glued in place. 

Tractor Unit 15

 

The floor pan was cut to size by scaling off photos of an original vehicle and the cab back panel was made by using tube sliced into quarters for the round sides and flat sheet in between. Half round styrene strip was added to form the body mold softening it with glue to form the correct shape. A seat back was made from sheet styrene and fixed onto the inside of the cab back. A seat base was made with thick sheet and this and the gearlever & 2 speed rear axle change lever were added to the floor.

 

It was at this stage that the more I compared the model with photos the more convinced I became that the shape of the grill was wrong. The top part was right but the bottom looked to have too much angle. Another grill was made with a flatter bottom angle and exchanged for the original one. This corrected the difference between the photos and the model.

 

All the pieces were glued into place but before the door panels were fitted, the cab and front were given a quick coat of Aussie green that was left over from painting another model. This was done to act as a primer and to show any defects so they could be tidied up. The doorway panels were made from thick sheet. 

Tractor Unit 16

Once again all these parts were scaled from photos. The open ended box fitted to the rear of the cab acted as a storage holder for the canvas top when it was lowered. This was made from styrene sheet and glued to the back of the cab. 

Tractor Unit 17

 

As the motors were painted a light Ford green and left this way until the trucks needed a rebuild the engine was painted at this stage along with the darker Army green on the firewall. This will be masked off at final painting stage. 

Tractor Unit 18

 

All the inner mudguard panels were formed from pieces of styrene and filler used to form the awkward shapes. These were painted on the interior before fitting. The curved mudguards were made by putting some styrene sheet fastened around a pipe and placed them in hot water. Brass strip was bent to act as the spring mounted headlight stands and a spare set of Tamiya GMC headlights were used. 

Tractor Unit 19

As parts like the front bumper and the behind cab toolbox had already been made any adjustments were carried out as they were fitted.

Tractor Unit 20

Copper wire was used as a fuel line between the fuel tank and the engine with fuel filters and brake reservoir added to the firewall.

 

Thin brass rod was bent to form the frame for the canvas roof top and studies of the original army photos with the top in both the up and down positions showed how the mounting brackets were made. These mounts were made out of small styrene pieces.

Tractor Unit 21

Slots were formed by drilling holes and finishing with a shape knife. Before the roof frame was fitted the cab interior was painted and any detailing done. (Paint color and type will be explained in the painting section.)

 

The frame was fixed to the cab and a piece of material was cut roughly to shape to act as the canvas roof. This was ‘spot’ tacked to the top of the windscreen with CA glue, gently stretching it as it was put on. Then it was pulled gently back over the frame and the process repeated at the top of the cab back. A new sharp blade in the scalpel was used to gently trim the sides of the material to shape. Thin CA glue was then soaked into the cloth. (Do not do this in an enclosed space as the fumes are bad for your health). Final trimming was now done to the edges and a brush used to paint the canvas inside the cab though the window & door opening.

Tractor Unit 22

 

While this dried I cut a windscreen frame out of a piece of very thin brass sheet. The frame was marked out and then a hole drilled in each corner of the inside of the frame. Then using a steel ruler as a straight edge I carefully cut between the holes using a sharp blade. This is best done on a hard surface and not your cutting mat. Once the main part was removed a needle file was used to tidy up the corners being very careful not to damage the thin center pillar of the frame. The outside is then trimmed using sharp scissors.

Tractor Unit 23

 

The frame is now laid onto a piece of clear styrene (I use 5thou sheet) and carefully, in a ventilated space, CA glued together. I use a fan blowing across the part to clear the fumes from the curing CA away before they fog the clear styrene. Once dry the excess clear is trimmed from the outside of the frame. CA glue is then used to attach it to the cab. Windscreen wiper arms and blades are made by cutting a small piece of styrene to length and then gluing a thin piece of rod to it. Once dry it is fixed to the windscreen in the correct place.

Tractor Unit 24

 

Now that is the tractor unit finished apart from painting. Part 2 will contain the building of the trailer and the painting and finishing of the whole semi unit.

Tractor Unit 25

Reference

 

Australian War Memorial Museum ( http://www.awm.gov.au/ ) for photos of the original vehicles

 

Alan Smith “Convoys Up The Track”.

Thanks

Bob Moseley of Adelaide, South Australia for the time taken to measure and photograph the surviving truck and trailer.

Last Updated ( Jul 31, 2010 at 12:26 PM )
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