Development of the Alvis Stalwart

If you've just landed on this page from an external source, please do visit the pervious page - The Development of the Punt hull 

I got tired of the incorrect Wiki pages, and magazine articles, so have put this together based on written and photographic evidence. 

This is a work in progress, so do come back. 

It should be remembered that the Stalwart was designed as a lorry capable of carrying 5 ton over rough ground, at which it excelled. It was never conceived as an amphibious vehicle that could also do 'off road'. The amphibious came during the development, when Fighting Vehicle Research and Development Establishment (FVRDE) asked if PV1 could ford.

To clarify, Fording refers to crossing shallow streams and fords, or when landing on a beach from a landing craft.

The following is based on documents, letters, reports, and John L. Rue's book. These include from Alvis, MOD records and trials reports, media articles, and more.

If you wish to see large images, right click on the image and select "Open image in new tab"

Alvis then asked, what else can we do with the punt hull?

The Stalwart was a private project started by Alvis in the late 1950s, to develop a 5 ton off road cargo vehicle. It is easy to see from an image of the Salamander chassis as to how they might have come up with the idea.

15 prototypes were made between 1959 and 1963, including the first none-amphibious model, PV1.

Martin Wickham is a former Alvis employee, who started his apprenticeship with Alvis in 1963. Martin tells me:-

"Apprentices were expected to attend PT sessions twice weekly, particularly in their first year, and thereafter were encouraged to do so.  These were usually led by senior staff who still felt the need to keep fit enough to play rugby, and included the Chief Engineer, Mike Dunn.  On several occasions, we piled on a Stalwart or into a Saracen and drove to the local swimming baths for a wet pt session.

Originally built for testing aero engines, the land at the side of Baginton was a council rubbish tip until at least 1968.  Thereafter it was developed primarily for the CVR(T) family, so I suspect that Stalwart trials there were minimal.  

The Stalwart's final production tests involved road running, but little off-road work.  In the yard at Holyhead Road 2 rows of railway sleepers were arranged to exercise the suspension  (and relive transmission wind up), and there was also a flotation tank to check for leaks and thrust." 

The Alvis factory on Holyhead Road, Coventry

The Baginton test track

The document below is Alvis' proposed specifications for the Stalwart. The final speed of 41.5 m.p.h. is due to a change in gearing for offroad traction, and the downrated B81 compared to the Salamander engine.

This extract is from the U.S. Army trials report of 1963

The Stalwart, built in England, is a cross-country, amphibious, 6x6, load carrier designed to carry a five long ton payload (11,000 lbs) over adverse cross-country terrain and across inland waterways.

Construction is of a frameless all welded waterproof hull mounted on six independently sprung wheels. Hydraulic servo assisted steering and braking are provided. Tractive power is supplied by an eight cylinder in line liquid cooled gasoline engine rated at 220 gross BHP @ 4000 rpm. Driving torque to the six wheels is through a twin dry-plate clutch, five-speed synchromesh gear box, transfer case, six bevel boxes and hub planetary reduction gears.

For swimming operations, power is achieved by two propulsion units (hydro jets) driven by a single mechanical drive coupled to a power take-off at the transmission. in water is manually operated by tiller arms which direct the flow of water from the two hydro jet units.

In Alvis' own Instruction manual for PV4 and PV5, of 1962 they state;

THE STALWART LOAD CARRIER

Introduction

1. The Stalwart is a cross-country amphibious load carrier and is capable of carrying a five ton payload over extreme terrain conditions and across inland waters. The vehicle possesses a performance comparable with most tracked vehicles but has in addition the advantages of the ease of maintenance, speed, quietness of movement, minimum crew fatigue and the virtual absence of damage to roads and communication lines.

2. The Stalwart is a frameless vehicle with an all welded water—proof hull mounted on six independently sprung wheels and powered by a Rolls Royce B.81, Mk.80B engine and two DOWTY water propulsion units. The engine is installed in the rear of the hull and the two propulsion units positioned at approximately the centre line and on each side of the rear wheel stations. The two propulsion units are driven by a single mechanical drive coupled to a power—take—off fitted on a transfer box.

3. The tractive power is transmitted from the engine through a twin dryplate clutch to a five speed gearbox used in conjunction with a 'forward' and 'reverse' selector box. The drive is then transmitted to a transfer box bolted to the rear of the gearbox, through transmission shafts to six bevel boxes and hub reduction gears to the six wheels.

4. The hydraulic servo-assisted steering is centrally controlled and operates by positive mechanical linkage on the two front and centre road wheels. Steering in water is manually operated from a tiller arm which controls the two propulsion units. Limited water steering can, however, be obtained by operation of the steering wheels only.

5. Hydraulic servo-assisted disc brakes are fitted to all wheels and are operated with a foot pedal. Two additional transmission brake assemblies are fitted to the two front bevel boxes and are operated by a mechanical ratchet type handbrake incorporating a quick release mechanism.

6. The vehicle is equipped with a 24 volt negative earth return electrical system the main equipment being water—proofed and suppressed to prevent radio interference. Navigation lights, conforming to International Maritime Law are incorporated in the lighting system. The Further descriptive information, routine servicing and adjustments relative to the various systems will be found on the subsequent pages of this handbook.

The Journal of Terramechanics is primarily devoted to scientific articles concerned with research, design, and equipment utilization in the field of terramechanics.

The Journal of Terramechanics is the leading international journal serving the multidisciplinary global off-road vehicle and soil working machinery industries, and related user community, governmental agencies and universities.

There were 15 Pre production prototypes. They were known as Private Venture, as Alvis started this venture without any MOD request for such a vehicle. They were marked and known as PV1 to PV15. Whilst every PV was slightly different to the next one, by PV13 they were to FV620 production standard and specifications.

These models are known as PV or Pre production models.

The first production model was known as FV620. The first true production vehicle carried the chassis number STAL 16. The FV620 became the Mark 1 when the FV622 Mark 2 build was started in 1965. There is no FV621.

All 7 PV that entered service with the British Army were standardised during refit to look like any other Mark 1. PV8 below is a good example of this, with the side boards, front indicators and splash board being changed to match the FV620.

PV1 as a theory proving vehicle was successful, and dropped so that PV2 could be developed.

It is said that after trials with the Army, PV1 was used by Alvis as a test bed for front and rear steering, rather than the traditional front 4 wheels steering on the FV600 series. The trials were unsuccessful, and the trials dropped. Still looking for evidence of that.

At the French air show, with a Saracen and the Agosy transport plane in 1960. Note the lack of splash board on this Off road truck. It is hard to see any evidence of a propulsion system in this photo.

The first change was to add the splash board.

Rear pillars are added, and double skin sideboards

Dowty propulsion system.

To save going into too much detail here, there is a separate page dedicated to the Dowty marine propulsion system.

The original design was that the rear radiator exit shaft was open, with no grate over it. The rear load area bulkhead had a strengthening ladder rack across it. It was designed that whilst the vehicle was being loaded through the tail board - the bulkhead could be lowered to cover the air exit, with the rack supporting the bulkhead for people to walk on.

The vehicle was now considered to have a high mobility and amphibious capability, and was considered ideal as a maintenance vehicle, supplying units in the field.

After numerous trials, the British Army took the Stalwart into service in 1963, and continued trials and development of it.

1964

PV3 was apparently fitted with Saro-Gill propulsion system during construction, but I cannot find any Saro-Gill marine propulsion manufacturer. A MEXE report of 5th and 6th June 1963 shows that it was being trialled with Dowty units and the Mariner Buoyancy tanks.

Mariner's buoyancy kit

The kit included a scoop, to close off the air intake during rough waters

This is PV5, seen at a sale of Swedish military equipment in 1983.

See https://www.facebook.com/arsenalen.sverigesforsvarsfordonsmuseum/posts/pfbid0NwkvpsTLvm92etNc3N4sfoj4MkNVA1ZbbsNdiGeG8nKw4VsxTj7wQoCsBBEyxx9Pl

The bottom step is of the long handle type, compared to the short rectangular foot step in PV4. There is sightglass behind the upper step.

From the rear view, you can see the FOCO crane and the early Dowty propulsion outlet. The above photo was taken by Stefan Karlsson, whilst stood on PV4.

PV4 and PV5 were fitted with the early Dowty propulsion units

This image of PV4 appeared in the Commercial Motor Magazine of 7th September 1962. The article was on the Alvis Stalwart, which was being displayed at the 1962 Earls Court Commercial Motor Show of that year, to see what commercial interest there was in the stalwart. It clearly shows the octagonal hatches and early propulsion system of PV4 and PV5. 

Whilst it is easy to Standardise any Stalwart Project Vehicle after production, to resemble the look of the later Standard Mark 1s - the vehicle at the 1962 Earls Court Commercial Motor Show had;

• Very distinct front windows on the side of the cab. They appear to have some sort of frame - for opening perhaps. From photos, it's possible to presume that it's not PV4, 5, 6, 8,

• Round hatches, so we know from photos that it's not PV4 or PV5, which had the octagonal hatches.

• Square cornered flat sideboards, so not PV3, or PV8 to PV15

• Early type Dowty propulsion system. We know these were easily changed to the later Dowty units.

• High level front indicators. But we know from PV8 that retrofitting protected units on the waistline was done.

The two following images show that it had a Ladder type rear load bulkhead, and an open air outlet.

The Americans trialled PV8 with 11,000 pounds - around 4980 Kgs  

The American report on the Stalwart can be viewed here

https://drive.google.com/file/d/10emFXXq9s7C_FdSS19f5kPOp6i5ich9-/view?usp=sharing

PV10, 23EK50 had ribbed side and tailboards. It was deployed to the REME Fording Trials Branch (FTB) at Instow. It also appeared in a film (below) of water trails in Germany.

PV11 had an internal hydraulic winch mounted at some point. 

It is not know if PV11 was kept by Alvis for development trials, or fitted with a winch after Sweden started mounting winches on the front of their Amfibiebil 101 Bs

Of the 6 PV that the British Army bought, PV 7, 8, 10, 11, 12, 13 all went through a refit to look the same as any Mark 1, with the revised water deflector board and side boards as neccesary - around 1970.

126 true Mark 1 production models were made between 1963 and 1965. They had the chassis number STAL16 to STAL141.

The following photos are Swedish Mark 1. The cab layout is the same, except the Swedish fitted 3 radiators in the cab, and around 1974, a winch mounted on the front and a FOCO crane in the back.

MOD records show that 956 Mark 2 were made between 1965 and 1971. Sadly, Alvis appear to have lost their records from around 1969 onwards. So it cannot be verified if more than 956 were made, unless Sweden bought any in 1971. 

The Mark 2 chassis number was STAL 11/1 to STAL 11/956

STAL 11/ is read as in STAL 2/

Changes for the Mark 2 included;

• The visibility was improved by increasing the depth of the corner windows.

• Cab layout was redesigned for ergonomic reasons.

• Braking efficiency increased by the addition of another servo pack and master cylinder.

• Driver maintenance was reduced by improving lubrication, including using a reservoir of oil to automatically maintain levels in certain critical transmission components.

• A 5 tonne self recovery hydraulic winch was included as standard equipment.

The following PDF is a basic Alvis handout of the F.V.622 Mark 2 Stalwart. The type of thing handed out at shows, without the expense of a glossy brochure . This is of course during British Leyland ownership.

In 1966, Fighting Vehicle Research and Development Establishment took various vehicles to Thailand, to see how they would perform in Paddy Fields and various soil types. They took the first three Mark 2 Stalwarts, STAL 11/001 07ER56, STAL 11/002 07ER57, and STAL 11/003 07ER58. 07ER57 is the one with the over sized Michelin tyres.

The film can be watched on the Imperial War Museum website, by clicking here

The difference between the FV623 and the FV624 was that the FV624 crane's hydraulic pipes had check valves in them. Normally, a crane under load will creep down with the weight. The check valves allowed the suspended item to remain where it was suspended, whilst people worked on the item, or prepared to join two items together.

The extract of MERLIN below shows us that 91ET74 was an FV623 limber. The last entry for Stalwarts is chassis number STAL 11/956. It came into service on 1st July 1971 

The "Deflector Board Assembly, Water" is commonly called the Splash board.

When PV2 was first produced, a splash board hadn't been considered. Remember that Stalwart was designed as an off road cargo truck, which the army then asked Alvis if it could ford. To Ford, or Fording in this context meant to be able to drive from the landingcraft to the shore without excessive preparation. 

Below are two images of PV2 in 1960, with no splash board.

The Deflector board used on the Pre production and Mark 1 models was a bit of a Heath Robinson affair, in that the driver had to stand on the ground to assemble the board.

As part of the trials in preparation for the Mark 2, 02SP43 (Chassis STAL 33 or 35) was used as the test bed for developing a new splash board. FVRDE carried out a number of trials at ASMT Leconfield.

In 1970, authorisation was given for all Mark 1 Stalwarts (which included 7 updated PVs) of the British Army to have their Deflector boards changed to the later type of board.

Below are two images of PV8 - 24EK71 as it came out of the factory in 1963, with the original Deflector board.

In 1982 it was decided that amphibious requirements were no longer neccesary, this primarily due to more modern bridge building equipment. 

Corrugated sides

Strengthened corrugated sides

The following sideboards appear at around the time that the FV623 limber was introduced, in 1969.