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The Development Of The Punt Hull
The following sets out where the ideas for the 1946 General Staff Specifications probably came from - and how the Punt Chassis designed by Fighting Vehicle Design Establishment (FVDE) was used on the Alvis FV600 range, which ending up underneath the FV620 Alvis Stalwart.
It's a work in progress. So please do come back in the future for another look.
Part of the vast expense of the Second World War, and the shortage of vehicles - was down to the cost of broken vehicles that had to be abandoned.
Not only were different manufacturers using different components (filter housings, lift pumps, etc), but manufacturers were also using different components on different batches of their own vehicles, and across their range of different vehicles. This included of manufacturers using their own or different screw threads to other manufacturers. This resulted in being unable to source parts for broken down vehicles and even bolts from other broken vehicles due to differences in design.
Interesting to note that
UNC and UNF are symbols of Unified National threads, of the Unified Screw Thread Series.
The Unified Thread Series was agreed by Canada, Great Britain and United States in 1949 to obtain changeability. Recently, modifications have been made to the original 1949 specifications for ease of use.
The United Thread Series is classified into Coarse threads, Fine threads and Extra fine threads, much like Metric screw threads are.
UNC: Is the symbol for Unified Coarse pitch threads.
UNF: Is the symbol for Unified fine pitch threads.
UNEF: Is the symbol for United extra fine pitch threads.
UNS: is the symbol for Unified special threads.
Also - https://www.fastenerdata.co.uk/threads
It was not until 1947 with the re-founding of the International Standards Organisation (ISO) that further development took place eventually leading to the promotion of the ISO standard metric thread in 1960.
As a side note - Nicholas Straussler, and armoured cars
Alvis were involved with providing engines for armoured cars with Nicholas Straussler of Romania, mostly for the RAF - and even trialled their own scout car before the Second World War.
Further, the name Dingo was used by Alvis for their trial armoured scout car, which was adopted for the Daimler car that won the contract.
Nicholas Straussler states in some of his early patents, such as the 1921 patent GB192805A, that he is of Romanian Nationality. Born in 1891, Staussler died in 1966. His patents show that he was in the UK by 1910, with a UK address for a January 2011 patent. The patents later in his life show he lived in Switzerland towards the end. Straussler had some 67 UK Patents, and 87 in other countries, although some of those are repeats of British ones. His first patent of 1911, was for improvements to the Rotary engine, at the age of 21.
Nicholas Straussler's first armoured car, the AC1, was produced as a chassis by Manfred Weiss of Budapest, trading as Weiss Manfred RT.
The tubular chassis was of a rear-engine layout with four-wheel drive and four-wheel steering. No make is given for the engine although we are told that it was a four-cylinder unit rated at 100bhp with overhead valves.
It drove forward into a six-speed each way gearbox and had a tubular backbone chassis with swing arms to each wheel and transverse leaf springs. The interesting thing is that the company stopped building commercial vehicles in 1929 and did not start again until 1935. Yet the AC1 chassis appeared in 1932/1933.
Anyone who knows the mechanics of the Daimler Dingo will have bells ringing at the familiar details given above. This vehicle AC1 was tested in Britain in 1933.
The AC2 was made in Hungary in 1935, and driven by road to the UK where it was given improvements - including a turret and an Alvis engine. It was given to the RAF, who liked it.
AC2 of 1935 en route from Port Said to Baghdad, escorted by a Rolls-Royce armoured car of the Royal Air Force
Amongst Straussler’s interesting joint ventures was that with the Alvis company following the incorporation of Alvis-Straussler Ltd on 13 July 1936. This combination of Alvis engineering and Straussler ingenuity produced the AC3, which used a chassis imported from Manfred Weiss, powered by a 120bhp Alvis 4.3-litre engine. With a fuel capacity of 45 gallons (205 l), the AC3 had a theoretical, but impressive, range in the region of 375 miles (600km).
The RAF ordered 12 AC3s in 1937 which were duly shipped out to the Middle East for use as civil defence vehicles and given the designation of ‘Car, Armoured, Alvis-Straussler, Type A’. Most, if not all, were based in Aden.
The AC3, known to the RAF as ‘armoured car, Alvis-Straussler Type A’, had a rear steering position with second steering wheel and duplicate controls. It ran on 10.50 x 20 tyres and had a transfer box added to the gearbox which gave a low ratio when required and incorporated forward/reverse gear and disconnected steering to the front axle for driving in reverse.
An Alvis-Straussler AC3, one of 12 for the Royal Air Force seen here during a trial run in Britain before going to the Middle East
Two other vehicle designs appeared shortly before the war. Although technically of Straussler parentage this was not acknowledged with either design but they are included out of interest.
One was the Alvis ‘Dingo’ Scout Car, a two-man machine powered by a four cylinder engine. It was entered for a War Office competition and came second to a BSA design and was never heard of again.
Text by Sheldon Michael Rogers
See https://someinterestingfacts.net/straussler-armored-car-ac1-ac2-and-ac3/
The Alvis Dingo, which lost to the BSA Scout car. Straussler's numerous patents show his influence on a nuber of Alvis military vehicles.
This image, from the Imperial War Museum, shows the rear of the Alvis Dingo scout car, with drive and suspension by Nicholas Straussler.
In 1938, the British War Office issued a specification for a scouting vehicle. Three British motor manufacturers, Alvis, BSA Cycles and Morris, were invited to supply prototypes.
Alvis had been in partnership with Nicholas Straussler and provided armoured cars to the Royal Air Force, Morris had participated in trials and production of armoured cars and BSA Cycles – whose parent Birmingham Small Arms (BSA) was involved in armaments – had a small front wheel drive vehicle in production.
Testing began in August 1938. All were of similar size and layout – rear engine and all four-wheel-drive. The Morris design was eliminated first – suffering from poor speed even after modification by its builders. The Alvis prototype – known as "Dingo" – could manage 50 mph (80 km/h) over a cross-country course but had a high centre of gravity.
The BSA prototype was completed in September and handed over for testing. By December, it had covered 10,000 mi (16,000 km) on - and off - road, with few mechanical problems. Policy from the War Office changed to a requirement for an armoured roof. The BSA vehicle needed a more powerful engine and strengthened suspension. It was chosen over the Alvis and the first order (172 vehicles) for the "Car, Scout, Mark I" was placed in May 1939. The actual production was passed to Daimler, which was a vehicle manufacturer within the BSA group of companies.
The potential of the design was recognised, and it served as the basis for the development of a larger armoured car – a "light tank (Wheeled)", which would later become the Daimler Armoured Car.
The first pilot vehicle was built by the end of 1939, later to be named 'Daimler Scout Car' but already known by the name of the Alvis design - the Dingo.
The Daimler Armoured car on the left, with the Daimler (Dingo) Scout car on the right.
Both models having the H drive replicated later in the Daimler Ferret, and Alvis Saladin.
The driveline layout of the Daimler armoured car. The rear mounted engine, coupled via a pre-selector gearbox to a transfer box. The driveshafts take the drive to the front and rear wheels, and bevel boxes take the drive through right angles to the wheels. This layout would become the basis of the FV600 series
This video of the Daimler Armoured Car shows how the H drive train works
The Daimler Armoured Car
Back to the Punt hull
During World War Two (WW2), lack of commonality between brands of vehicles, and even between models of the same manufacturer caused supplies and spares issues. It was decided after WW2 that there must be as much commonality across models and brands as possible.
In 1946, the General Staff issued a Specification for new armoured cars, using components common with other vehicles. Also that a range of vehicles should be created using common chassis. It was decided that the Rolls Royce B Series engine would power the various sized vehicles from all vehicle manufacturers to ensure commonality across the field. Hence the early military Land Rovers having Rolls Royce engines.
Having taken note of the successful Daimler Dingo drivetrain (See Straussler below), the Fighting Vehicle Design Establishment (FVDE) came up with a Punt chassis, with an H drive line from a central differential giving a permeant 4 wheel drive Medium Mobility Wheeled vehicle, and 6 wheel drive High Mobility Wheeled vehicle.
According to Mike Dunn (Son of Willie Dunn - see Mike's article on the Stalwart development page), FVDE in association with Alvis' Willie Dunn, started designing the 6x6 Punt hull in 1947. Willie Dunn was the chief Engineer of Alvis, and designed the Saladin, Saracen, Salamander and Stalwart. Mike Dunn became Chief Engineer and designed the Stalwart Mk 2.
In 1952 FVDE merged with the Fighting Vehicle Proving Establishment (FVPE) and became Fighting Vehicle Development and Research Establishment (FVRDE)
A quick history lesson on Government military design and testing departments.
The Department of Tank Design (DTD) was formed in 1940. It studied and revised ideas for armoured vehicles through World War Two. In 1946, DTD merged with Wheeled Vehicle Experimental Establishment (WVEE) to form the Fighting Vehicle Design Department (FVDD). In 1948 FVDD was renamed to Fighting Vehicle Design Establishment (FVDE). In 1952 FVDE merged with Fighting Vehicles Proving Establishment, to form Fighting Vehicle Research and Development Establishment (FVRDE). In 1970 FVRDE and the Military Experimental Engineering Establishment (MEXE) merged to become Military Vehicles and Engineering Establishment (MVEE).
Because the design and development of the FV600 series is between 1948 and 1968, the term FVRDE will apply to mean any relevant predecessors for simplicity.
The specification for the FV600 hull given to Alvis by FVRDE in 1947 stated:
An all-steel hull, welded at all joints and sealed against the ingress of water.
The main power unit to be the Rolls-Royce B80 straight-eight water-cooled petrol engine, driving through a five-speed semi-automatic transmission and a forward-and-reverse single range transfer box. (As used in the Straussler, and Daimler Dingo Scout Car).
Suspension to be all-independent by wishbone, sprung either by torsion bar or coil springs. (as used in the Daimler Armoured Car)
The vehicle should be capable of being steered from either the front or rear end, and be by recirculating ball. The steering wheel for the front of the vehicle should be approximately parallel to the glacis plate, and vertical at the rear.
Require armour for immunity to near misses from medium artillery, including air bursts or from a 20lb mine.
The overall dimensions should not exceed: 16ft 2in (4.93m) overall length. 8ft 5in (2.57m) overall width. 6ft 8in (2.03m) maximum track, 10ft (3.05m) wheelbase, 1ft 4in (0.41m) minimum ground clearance. approach angle of 60 degrees front and 50 degrees rear, a maximum road speed of 50mph (80km/h), a maximum safe road speed of 35mph (56km/h) and a maximum speed in reverse of 20mph (32km/h).
The vehicle should have standard War Department pattern wheels, with non-skid chains to be fitted as required.
Brakes were specified as drums all round.
Armour thickness would be 8mm on the front visor, 10mm on the scuttle, 8mm on the glacis plate, 10mm on the skid plate and 12mm on the side plate.
The FV600 chassis design remained the property of FVRDE.
The FV600 Drive train and suspension
The drive train of the FV600 consists of an engine, Auto gearbox (clutch and manual gearbox on Stalwart), transfer box, which houses a None slip differential. The none slip differential (Detroit Locker) allows the vehicle to go around corners, with the outer set of wheels going faster than the inner set. But when the diff detects a slipping wheel, it will lock both sides together.
From the Transfer box, the drive then goes to a central bevel box on either side of the hull. This central bevel box allows drive to pass directly through to the middle wheel station, whilst also transfering drive through 90 degrees, to pass the drive forward to the Front bevel box, and also rearward to the Rear bevel box.
There are reports of the FV600 suffering from transmission windup. There are a number of causes for this. One is of untrained drivers looking after the vehicles, without carrying out Driver maintenance duties. The priority is of Wheel rotation. Any vehicle with multi axle drives will have the rear wheels trying to overtake the front wheels. One driver task was to carry out wheel rotation, so that the largest circumference wheels are at the front, and the smallest are at the rear. Ideally, there should be a maximum of 2 inches between the front and rear axle. Most units had five stalwarts, and wheels were measured and sorted between the 5 vehicles. This task was to be carried out every 750 miles.
Image shows front and rear wheels off the ground at the same time, to release any transmission windup.
The other cause of driveline damage would be because of being used for Garrison duties, that is to say being used to fetch stores from other garrisons whilst in camp. An order was given in BAOR that Stalwarts were not to be used for Garrison duties. Having said that, I've personally driven empty from Osnabruck to Munster, and come back with a full load of Jerry Can pack fuel - without issue.
The best way to remove windup, is to get the front and rear wheels off the ground at the same time. Bouncing one side off kerbs does not releave the transmission stress.
Failure to maintain the wheel sizes, and running empty, can result in the Bevel boxes being damaged.
From the relevant Bevel box, the drive is transfered to the outside of the hull. In the adjacent image, the drive to the shaft on the left is coming from the central bevel box.
The drive coming from the bevel box, then goes through two Constant Velocity (CV) Tracta joints. The CV nearests to the Bevel box simply allows the drive to move up and down, as the second CV moves up and down with the wheel. The Stalwart uses dual, parallel wishsbone links. These keep the second CV joint at a continuous position relative to the Bevel box.
The second CV joint allows the drive to move up and down. But on the front four wheelstations, it also allows side to side movement, for steering.
When the CV joints are not directly in line with each other, then wear and damage can happen to the faces of the Inner and Outer CV joint components.
The reason that the Stalwart suffers from CV Tracta joint damage more than the other FV600 models, is because of running Stalwarts when empty. Stalwart is designed to run with 5 tons of cargo in the back. Without that 5 tons, then the hull raises up, increasing the CV joint angles.
For enthusiasts and museums, it is better to adjust the ride height, so that all 6 pairs of CV joints are inline. As shown on the right.
The following images shows damage to intermediate drive shaft, that sits between the two CV joints, and the Inner and Outer pieces of a CV Tracta Joint. This is the result of running empty, without adjusting the ride height.
On the left is the Inner, on the right the Outer
Saladin Front wheel station
Saladin Centre wheel station
Saladin Rear wheel station
A Saracen Punt hull, produced by Alvis to explain how the FVRDE / Alvis Punt hull worked. This was located at the Army School of Mechanical Transport, at Leconfield - near Hull. Current location or fate is unknown.
The full Alvis Stalwart drive line, including marine propulsion system
Two versions to this story, and still researching it, but;
1) In 1947 Alvis helped FVDE to design the 6 wheel Punt hull, and Alvis were asked to produce an armoured car to a set specification on that punt hull. The Malayan Emergency started in 1948, and FVDE amended the 6x6 project to include an Armoured Personnel Carrier - for use in the Malayan Emergency. As an interim, Bedford RL and Humber 1 ton trucks were given sheet metal plating bodies, known as Pigs. Alvis were asked to design an Armoured Personnel Carrier on the same FVDE 6x6 hull principle. Alvis and/or FVDE then asked Crossley Motor Company to produce Armoured Car prototypes on Alvis' design. Alvis then rushed the Saracen Armoured Personnel Carrier through design and development, coming into service in 1952.
2) Crossley Motor Company at Stockport had previously made various trucks and armoured cars for the British Military. They were given the 6 wheel Punt hull design by FVDE in 1947, and asked to produce an armoured car to a set specification. 6 Saladin prototypes were produced. Alvis where then asked to produce the Saracen as a matter of urgency due to the Malayan crisis. Once sufficient Saracens had been provided, Alvis was given the contract for the Saladin, rather than Crossley.
Fact - Crossley Motors Limited agreed to be taken over by AEC in 1948.
Photo of the Trails of the Alvis Saladin. This version without a locking central differential.
According to David Fletcher of The Tank Museum, all the Saladin with civilian registrations were built by Crossley Motors Company.
Photo of the Trials of the Alvis Saladin. This version with a locking central differential.
GX is a London registration. Apparently, RGX was a London registration only used by Government - and included FVRDE.
It should be remembered that each model of the FV600 had it's own chassis designed and manufactured. The common part being the wheel stations, suspension and transmission. The chassis hull were not interchangeable between vehicles.
These images below show how the Saladin and Saracen have wide bodies, but narrows for the driver's compartment on the Saladin, and for the engine on the Saracen.
Saladin hull
Saracen hull
With the Saracen and Saladin under it's belt - Alvis then looked at what else this Punt chassis could be used for. The first designed was an Airfield Crash fire tender, built in conjunction with Pyrene, becoming known as the Salamander.
The Salamander's Punt hull chassis shares the same common components of the Alvis six-wheel-drive FV 601 Saladin armoured car and FV 603 Saracen armoured personnel carrier. The chassis itself is specific to the Salamander.
This is the bare chassis of the Alvis Salamander
Two images of the Alvis Salamander hull and cab, being put through various trails, thought to be around 1956 or 1957.
Then Alvis wondered if they could also make an off road truck, that would carry 5 tonnes.
The first cargo carrying Stalwart Project Vehicle (PV1) was completed and ready for trials in December 1959. It was known in the factory as The Beast. PV1 was purely to prove as cheaply as possible that the theory of the Punt hull carrying 5 tons off road was a realistic idea. It was nothing more than a Salamander, with a cheap drop side body.
There was never any consideration by Alvis for Stalwart to be amphibious, until FVDRE asked if PV1 could ford - as in beach landings and crossing shallow rivers.
The first Stalwart. PV1
The story of the Alvis Stalwart development continues on the next page.
Below are links to videos and records of the development of the Saladin and Saracen, because of how that resulted in the Stalwart.
A lot of the above is recorded in The Times. Simply search The Time's archive for Alvis Board meetings. https://www.thetimes.co.uk/archive/
See also
https://www.thinkdefence.co.uk/british-army-medium-weight-capability/fifties-sixties/
Future Historical Resources
Pathé news video 1954, of a Saladin and Saracen. Saracen with broken front suspension being towed
New Army Transport
British Movietone film of 1954 showing more of the Saracen. Same event as Pathé's The Army On Wheels
https://youtu.be/pY0Y50Ablok?t=15
Stop At Nothing Tanks
1956 Pathé film of a Saracen snorkelling
There are many films and documents held by Imperial War Museum, which have not yet been digitised, or marked for digitising. They include;
Fighting Vehicles - Chapter One
Film from 1955 about the development of the Saladin by FVRDE
https://film.iwmcollections.org.uk/record/25893
Exhibition of British Military Vehicles
Film from 1956, including the Saladin and Saracen
Rough Track Trials at FVRDE Bagshot.
Film from 1959, might include Camion trials
British Armour On Wheels
Film from 1962, More about Saracen and Saladin, but shows Alvis factory production - and possibly Camion.
Nizam Climate Trials in Queensland, Australia 1966-67
Includes Stalwart
Mudlark
Film from 1968 of trials on flooded Paddy fields in Thailand for FV622 Stalwart, and FV437 Pathfinder
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