The 'Big J4'


A 'Big J4' skip loader. Courtesy of Brian Shaw.

 The 'Big J4' series covered a gross vehicle weight range of 16 to 32 tons, for rigid, drawbar, and articulated use.

They were well suited for use as skip loaders, lutons, horse boxes, drop-siders, and tippers, and included heavy duty suspension with long semi-elliptic springs, big and powerful brakes, and a load sensing device on tractor models to ensure controlled progressive braking by matching braking effort to road and load conditions. This minimised the risk of jack-knifing.

The standard petrol tank had a capacity of 46 gallons, but a larger 63 gallon tank, or two dual 46 gallon tanks were available for long distance use.

The cab featured wide doors with a grab handle and a step at a convenient height for easy access. Routine maintenance was made easy because the engine cover was quickly removable, and oil and water levels could be checked within the cab. Grease points were easily accessible and kept to a minimum.


The 'Big J4' chassis. Courtesy of Brian Shaw.

The ‘Big J4’ Specification:

16 ton G.V.W. four-wheeler, load carrier, and tipper.

Engine
V6 diesel, 170 B.H.P. at 2,600 R.P.M., maximum torque 370 lbs. ft. at 1,700 R.P.M., or AV 505 (right hand only) 170 B.H.P. at 2,400 R.P.M., or AV,471 (right hand only) 150 B.H.P. at 2,400 R.P.M.

Clutch
Single plate, cushioned drive.

Gearbox
5 speed constant mesh gearbox. Ratios: 1st 6.5 to 1; 2nd 4.49 to 1; 3rd 2.769 to 1; 4th 1.49 to 1; top 1 to 1.

Propeller shaft
1600 series universal joint with rubber mounted centre bearing.

Rear axle
Single speed spiral bevel differential assembly. Fully floating hubs. Ratio: 6.5 or 5.57. Alternative rear axle with 2-speed differential, with electric shift. Ratio: 5.57/7.6 to 1.

Front axle
6½ tons capacity. Stub Axle 2.625" diameter. Axle beam section 4⅜" x 3⅛".

Steering
Re-circulatory ball type steering gear. 21" diameter steering wheel. Power steering an optional extra.

Suspension
Semi-elliptic springs. Front: 54" long; 4" wide; 10 leaves; single rate. Rear: 58" long; 3½" wide; 16 leaves; 2 stage; underslung. Telescopic shock absorbers available on front axle only.

Frame
High tensile alloy steel side member. Section 10"x 3"x 0.28". Pressed steel cross members. Cross members and spring brackets attached to frame side members by high tensile bolts. Frame width 34" international standard.

Brakes
Cam brakes (leading and trailing shoe) with dual circuit full air operation. Front: 15½" diameter x 6" wide. Area=362 sq. ins. Rear: 15½" Diameter x 7" wide. Area=422 sq. ins. Single-pull air assisted hand brake, mechanically linked with rear brake cam shaft. Rear brake actuators of the triple diaphragm type.

Electrical
24 volt insulated return system of wiring. 35 amp alternator fitted as standard.

Fuel tank
Circular tank of 46 gallons capacity.

Cab
All steel welded construction with a forward entrance, and one piece screen of generous area giving good visibility. A shock absorber type driver and passenger seat, available as optional extra. A sleeper cab was also available on export models.

16 ton G.V.W. load carrier for hauling a four-wheel trailer (32 tons gross train weight). Specification as above, except for the following:

Engine
V6 diesel, 200 B.H.P. at 2,600 R.P.M., maximum torque 444 lbs. ft. at 1,700 R.P.M., or 6LX (right hand nnly), 150 B.H.P. at 1,700 R.P.M.

Clutch
16" diameter single plate, cushioned drive.

Gearbox
6-speed overdrive, constant mesh with 1.25 to 1 underdrive splitter box with air operated finger tip control as an optional extra. 6-speed Ratios: 1st 7.17 to 1; 2nd 4.45 to 1; 3rd 2.54 to 1; 4th 1.53 to 1; 5th 1 to 1; 6th 0.75 to 1. Ratios with splitter box: 8.95 to l; 7.17 to l; 5.6 to l; 4.45 to l; 3.17 to l; 2.54 to 1; 1.9 to 1; 1.53 to l;  1.25 to 1; 1 to 1; 0.75 to 1.

Propeller shaft
1700 series universal joint with rubber mounted centre bearing.

Rear axle
Spiral bevel with planetary hub reduction. Fully floating hubs. Ratios: 7.69 to 1 (V6); 5.26 to 1 (6 LX with splitter)6.35 to 1 (V6 with splitter and 6LX).


A 'Big J4' lorry. Courtesy of Brian Shaw.


A 'Big J4' tanker. Courtesy of Brian Shaw.

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