Killen-Strait armoured tractor - case report

Lads!!

    Today, we will discuss the remarkable Killen-Strait armoured tractor. This experimental armoured vehicle was developed in the United Kingdom in 1915, during World War I. The project was initiated by the Landship Committee under the supervision of Winston Churchill. 

    Mechanically, it combined the chassis of a commercial American tractor - featuring three sets of tracks - with the turreteless body of a Delaunay-Belleville armoured car. Despite its poor mobility in deep trenches and its failure in crucial barbed-wire crossing tests, the Killen-Strait tractor provided vital engineering data that directly drove the development of Little Willie, the direct ancestor of modern battle tanks.

Killen-Strait armoured tractor fitted with the body
of a Delaunay-Belleville armoured car - 1915.

History

    In February 1915, the Landship Committee was formed under instructions by First Lord of the Admiralty Winston Churchill to develop armoured fighting vehicles for use on the Western Front. 

Portrait of Winston Churchill in the official dress
of First Lord of the Admiralty- 16 September 1914

    Colonel R. E. B. Crompton, the appointed technical adviser of the committee, was tasked with producing "alternative designs for the wheeled and tracked machines." However, no reliable tracks were available in Britain at the time, and an officer was sent to the United States to locate suitable tracked vehicles.

Portrait of R. E. B. Crompton,
seated at a desk - 1948

    Between February and April, the Admiralty was contacted by the London agent of the American Killen Strait Manufacturing Company. The company, based in Appleton, Wisconsin, advised the Admiralty that a lightweight chain tractor, along with William Strait from the company, had arrived in the United Kingdom and hoped to give a demonstration. This information was forwarded to Crompton and a viewing was arranged. 

Promotional brochure from the Killen-Strait Manufactirung Company,
from Appleton, Wiscosin - USA, from 1914.

Promotional brochure from the Killen-Strait Manufactirung Company,
from Appleton, Wiscosin - USA, from 1915.

    On 27 April, William Strait and the tractor arrived at the Clément-Talbot works for testing. Crompton was impressed with the vehicle's design and engineering, and purchased the vehicle for £800.

    On 20 June, the Landship Committee held a demonstration at the recreation ground adjoining the works to show its progress. The Killen-Strait tractor was one of the few vehicles available, and the demonstration was attended by Churchill, Minister of Munitions David Lloyd George, Lord Grosvenor, Director of Munitions Supply Sir Frederick Black, Maj Gen Ivor Philipps, Major General George Kenneth Scott-Moncrieff, Colonel Henry Holden and Head of Trench Warfare at the Ministry of Munitions Louis Jackson. 

Mr. Lloyd George and Mr. Winston Churchill watching experiment
with Killen-Strait Tractor, fitted with torpedo wire-cutter.
Wormwood Scrubbs, 20th June 1915.
IWM (Q 14614)

Killen-Strait Tractor negotiating slightly rough ground
during experiments at Wormwood Scrubbs, June 1915
IWM (Q 14620)

    The vehicle was driven by Thomas Gerard Hetherington into tensioned barbed wire, across dummy shell holes and small piles of railway sleepers. 

Killen-Strait tractor probably being driven by Thomas Hetherington,
at Armoured Car Headquarters at the Clement Talbot Works,
Barlby Road, Wormwood Scrubbs. June, 1915.
Note torpedo wire-cutter.
IWM (Q 14616)

Killen-Strait tractor probably being driven by Thomas Hetherington,
at Armoured Car Headquarters at the Clement Talbot Works,
Barlby Road, Wormwood Scrubbs. Late June, 1915.
Note torpedo wire-cutter.
IWM (Q 14615)

Experiment with Killen-Strait Tractor at R. N. A. S. Armoured Car Division H. Q.,
Wormwood Scrubbs, June 1915.
 IWM (Q 14619)

Killen-Strait Tractor during the experiments
at Wormwood Scrubbs, June 1915.
IWM (Q 14618)

Killen-Strait tractor probably being driven by Thomas Hetherington,
 at Wormwood Scrubbs, June 1915.
IWM (Q 14617)

    The vehicle demonstrated good mobility but was not able to breakthrough the barbed wire. After a short while, Lt Kenneth Symes fitted a modified turretless armoured bodywork from a Delaunay-Belleville armoured car onto the vehicle, creating the first tracked armoured vehicle.

Delaunay-Belleville Armoured Car from RNAS,
brand new at Dunkirk

Killen-Strait caterpillar tractor fitted with a modified turretless
 body of a Delaunay-Belleville armoured car.
late, 1915

Killen-Strait armoured tractor fitted with the
markings of the Royal Naval Air Service
late 1915

    It was envisioned for this vehicle to join the RNAS Armoured Car Section, but this was not realized due to the unit's imminent disbandment. The vehicle was transferred to the RNAS Barrow Airship Station in September 1915, serving as a tow tractor there. The project itself was also abandoned, as the vehicle was unable to fulfil all-terrain warfare requirements and could not cross wide trenches. However, the trial would lead to the adoption of tracked propulsion for "Little Willie", the first prototype tank.

Little Willie tank at Cricklewood
United Kingdom

Design

    The vehicle consisted of three tracks. A front track was used for steering, while two tracks in the rear provided propulsion. The rear-facing side of the rear tracks tilted upwards, allowing the vehicle to climb obstacles when in reverse gear. It has been proposed that this innovative design inspired the rhomboid shape tracks of the later Mark I tank, though this claim is controversial.

Mark I series tank and crewman at
Thetford in "Solomon" camouflage - 1916.

    Unfortunately, as happened with the vast majority of experimental prototypes from that early phase of the First World War, it was eventually dismantled and sold as scrap, leaving only photographic records of its tests.

Specs:

Killen-Strait armoured tractor
Type	Experimental armoured tractor
Place of origin	United States Great Britain
Service history
In service	N/A
Production history
Designed	Killen-Strait RNAS Armoured Car Section
Manufacturer	see text
Produced	30 June, 1915
No. built	1
Specifications (approx.)
Mass	4.310 Kg
Length	4.72 m
Width	2.27 m
Height	2,17 m (with armoured body)
Crew Armour Fuel capacity	3 (?) 6 - 8 mm  2 x 57 liters
Main armament	(Projected)  Maxim or Lewis,   .303 inch machine guns
Engine	Doman petrol engine 50 cv.
Transmission	Two-speed forwards, one reverse
Suspension	Unsprung

 

The kit:

    Here is another project involving a 3D-printed kit. This time, it is a model printed by Vargas Scale Models: the Killen-Strait armoured tractor (R3D-35-163). The kit arrives with the sub-assemblies packed in zip-lock bags and wrapped in bubble wrap, all inside a sturdy cardboard box. My kit arrived with the "fork" of the front track assembly broken—though the pieces were still inside the bag, indicating the break occurred during shipping. The repair was straightforward, as the broken parts fit together perfectly.

 The Killen-Strait armoured tractor printed kit (R3D-35-163),
from Vargas Scale Models - box art cover.

The kit components, with their sub-assemblies
attached to their print structures.

    The first thing I did was remove the parts from their print supports and clean off the excess support material. The kit is well-printed, though some print lines are visible. Nothing arrived warped, and only the front track retention fork was broken. I immediately fixed the piece with super glue, fearing the tricks of the "carpet monster"...

The Vargas kit, after the initial cleaning...

The print is highly detailed. Take a look at the track assemblies.

Note the front fork, which has been repaired and glued in place.
I applied a tiny amount of putty to the fractured area to
 completely level the surface of the part.

The front track assembly is very delicate.
Front right view. Notice the putty, in the fracture region

The front track yoke features the tractor manufacturer's name.
front left view

Side view

    After fixing the fracture in the part, I returned to the sequence prescribed in the (spartan but clear) instruction manual. I sanded the base of the tractor's armored body and the supplied chassis (which was perfectly straight). After a dry fit, I began gluing, applying a tiny drop of cyanoacrylate to each corner to check the position and alignment—since superglues allow for no adjustments. Once I had verified and approved the chassis's positioning, I secured the joint between the parts with more superglue.

The tractor body and chassis, cleaned and ready to be glued together.

    Next, I used the same procedure—tack-gluing the two rear track sub-assemblies—and checked the positioning and alignment of the entire tractor as it rested on its own tracks. Perfect! I glued all the joints of the rear track system. The front assembly is movable, capable of rotating 360°.

The tractor, standing on its own little paws.
The visual appeal is striking!!! A true eye-catcher.
left view

Right view

Rear left view.
Notice the print lines 

    One thing that bothered me was the tractor's steering system; the hole in my kit was a bit too large, creating a looseness that annoyed me. I know the kit is a static model and, theoretically, that joint could even be fixed. I also know, from photos of the actual tractor, that the kit reasonably replicates the real thing. Still, that play bothers me. Since the front of the vehicle will be assembled in the closed position (there is an option to leave it open, but the detailing doesn't quite warrant that...), I’m going to install a reinforcement in this area to make the kit sturdier and easier to handle. This structural reinforcement will be hidden behind the front armor plates.

I used a Plastruct plastic tube to increase the mounting
base area for the steering track's rotation axis. I also made some
 washers for the final installation using the same material.

The Plastruct plastic tube glued in place.
The track axle fits much more snugly with this modification.

Testing...testing...the tube in dry-run

    And since it’s a structural reinforcement, I didn’t rely solely on the contact area between the tube and the base. I used an I-shaped piece of Plastruct to create a horizontal brace, thereby increasing the bonding area and strength.

The horizontal reinforcement glued in place.
Notice the tube glued in position, also.

And the armored front plates are glued in place.
Everything blends in, and the kit becomes more robust.
front left view

Front right view

Top view. The entire system will only be finalized later,
with the bonding of the washer and the directional arrow.

    With that, I considered the kit assembly complete. Now, on to the markings. Original period photos show the tractor both with and without markings. The chosen color was a a slightly bluish gray - the same shade used on my "Little Willie" - which I felt was quite appropriate for the era. I selected the version featuring the large R.N.A.S. (Royal Naval Air Service) lettering on the sides.  As usual, I created a drawing to serve as a guide.

The guide of markings & colors

I colorized an original photo to visualize the project...

    I printed the Royal Naval Air Service letters onto a sheet of clear film using my laser printer, after designing the artwork in vector graphics software. The white circle is from my spare box of decals. I started painting by covering the entire kit with Vallejo matte black primer.I forgot to mention: the interior parts haven't been glued in yet. The interior will be painted and detailed now, at this stage. It is quite simple, featuring a firewall, an instrument panel, a steering system, a driver's seat, pedals and control levers, as well as two rectangular fuel tanks. All of this can - and should - be assembled through the large opening where the turret would be positioned.

The kit and the interior details painted in black primer

    I painted the interior of the tractor in aluminum - as was standard for the interiors of British vehicles of that era - and, after masking, painted the exterior in bluish gray. The fuel tanks were painted dark green.

The kit in bluish gray with tonal variations and
the interior details in aluminum and green

Left top view

The aluminum firewall and the primitive and simple
 instrument panel, painted freehand.

Firewall glued in position

My decals, laser-printed on a sheet of clear decal paper.

    Once the paint was completely dry, I applied two coats of gloss varnish to smooth the model's surface and ensure the best possible fit for the decals. Due to the model's rivet-covered surface, I used the excellent decal setting solutions from Tamiya and Ammo. First, I applied Ammo's Decal Set to improve the film's adhesion to the uneven surface; then, once the decal was positioned, I applied a generous coat of Tamiya Mark Fit Super Strong. 

Adapting the decal to a nightmarish surface.
The Ammo stuff before the decal and the Tamiya one after.

    I used a cotton swab soaked in Tamiya Mark Fit and carefully conformed the decals over the rivets details, eliminating air bubbles as much as possible... I repeated the process 2 or 3 times.

The RNAS decals, in position...
The white circles went more smoothly. Since I didn't have
a thicker circle, I used two thin ones and will fill in the gap with white paint.

The decals were applied, dried, and sealed with a gloss varnish,
and then the entire kit was given a uniform matte finish.
Not a trace of silvering!!
Perfect!! Thanks, Ammo and Tamiya!!!

Left view

Right view

Front right view

Front left view

Rear right top view

Rear left top view

    Following the final drying of the layers—gloss varnish, a sealer coat, and a final varnish to ensure a uniform finish—I applied weathering to the vehicle. I kept this relatively subtle, as I wanted to depict it just after it had been in field use. I present to you the British Killen-Strait armoured tractor, bearing R.N.A.S. (Royal Naval Air Service). markings and based at the Barrow Airship Station in September 1915.

Killen-Strait armoured tractor - R.N.A.S. (Royal Naval Air Service).
 Barrow Airship Station, England -  September 1915.

Killen-Strait armoured tractor
left side view

Killen-Strait armoured tractor
rear left side view

Killen-Strait armoured tractor
rear right side view

Killen-Strait armoured tractor
right side view

Killen-Strait armoured tractor
front right side view

Killen-Strait armoured tractor
with Kojak, for size comparison

Killen-Strait armoured tractor
with M1917 American light tank

Killen-Strait armoured tractor - R.N.A.S. (Royal Naval Air Service).
 Barrow Airship Station, England -  September 1915.

    The Vargas Models 3D printed kit is very interesting and easy to build, resulting in a truly unique final appearance. I thoroughly enjoyed building this pioneering vehicle. It is highly rewarding to have access to scale models of such historical relics.

See you all soon for the next

modeling adventure!!!

Who said military life can't be fun?!!