AKA Cambridge carrier

[Richard Farrant]

Hi Jon
That does indeed look like an adapted pre-select box as used in a Saracen. The engine is a B80
Regards
Richard

[charlie fitton]

Now I'm jealous

[Michael R.]

Originally Posted by Richard Farrant

Hi Jon
That does indeed look like an adapted pre-select box as used in a Saracen. The engine is a B80
Regards
Richard

Does the image Jon posted of the driver hand and foot controls show a third foot pedal to the left . . . a gear change pedal (GCP)?

Nigel Watson wrote in:
'Universal Carriers Volume II' at page 235:

"Power is supplied by a B80 Mk.2F engine and is transmitted through the transmission unit propeller shaft, Cletrac steering unit and coupling shafts to the final drive assemblies.

Either of two types of transmission unit may be fitted, namely the Wilson pre-selective gearbox and the Hobbs transmission unit. Both units simplify gear changing and eliminate the need for a clutch; therefore no clutch pedal is fitted.

Vehicles fitted with a Wilson gearbox are however fitted with a gear change pedal. Therefore vehicles fitted with a Hobbs transmission unit can be readily identified by the absence of the gear change pedal, there being only two foot control pedals fitted, the accelerator and the brake."

[Richard Farrant]

Originally Posted by Michael R.

Does the image Jon posted of the driver hand and foot controls show a third foot pedal to the left . . . a gear change pedal (GCP)?

Nigel Watson wrote in:
'Universal Carriers Volume II' at page 235:

"Power is supplied by a B80 Mk.2F engine and is transmitted through the transmission unit propeller shaft, Cletrac steering unit and coupling shafts to the final drive assemblies.

Either of two types of transmission unit may be fitted, namely the Wilson pre-selective gearbox and the Hobbs transmission unit. Both units simplify gear changing and eliminate the need for a clutch; therefore no clutch pedal is fitted.

Vehicles fitted with a Wilson gearbox are however fitted with a gear change pedal. Therefore vehicles fitted with a Hobbs transmission unit can be readily identified by the absence of the gear change pedal, there being only two foot control pedals fitted, the accelerator and the brake."

The gearbox in Jon's photos is quite clearly a Wilson pre-selector, similar to a Saracen, only visible difference is the end plate and output drive flange ( A Saracen box is bolted up to the transfer box and no flange needed). This will mean swapping over some parts I guess.

The gear selector is the same layout to the Saracen (etc). The Cletrac steering is similar to the Oxford Carrier, with two sets of tillers.

[Jon Bradshaw]

To answer your question- Does the image Jon posted of the driver hand and foot controls show a third foot pedal to the left . . . a gear change pedal (GCP)?
--Yes there is a third pedal down at the left beside the final drive and it is attached into the side of the center gearbox. I do not know what it does, it may have been a carry over from other design and do nothing or it may be a gear change lever. I will need to take a closer look when the weather is warm again.
You also mention cletrac steering with dual tillers, do you have some insight into what final drive assembly this is? A "normal" final drive (like a T16) doesn't have a transmission style shifter built into it with 5 gears and a reverse lever.....
This makes me wonder if the transmission is almost superfluous and the final drive can act as the transmission? Or it is geared in such a way as to allow massively low and high gearing (might be why the 5th gear is locked out with a bolt) 5th and 5th would be really fast. 1st and 1st would climb almost any hill with a load under tow. The reverse lever would act like a ferret and give you the same 5+5 in reverse....

[Richard Farrant]

Originally Posted by Jon Bradshaw

--Yes there is a third pedal down at the left beside the final drive and it is attached into the side of the center gearbox. I do not know what it does, it may have been a carry over from other design and do nothing or it may be a gear change lever. I will need to take a closer look when the weather is warm again.
You also mention cletrac steering with dual tillers, do you have some insight into what final drive assembly this is? A "normal" final drive (like a T16) doesn't have a transmission style shifter built into it with 5 gears and a reverse lever.....
This makes me wonder if the transmission is almost superfluous and the final drive can act as the transmission? Or it is geared in such a way as to allow massively low and high gearing (might be why the 5th gear is locked out with a bolt) 5th and 5th would be really fast. 1st and 1st would climb almost any hill with a load under tow. The reverse lever would act like a ferret and give you the same 5+5 in reverse....

Hi Jon,
The left pedal will be connected to the pre-selector gearbox by rods and operate a lever on the top side of the box, this works the busbar in order to engage a pre-selected gear. No different to a Ferret which you may be familiar with. The driver operated gear selector gate appears to only be mounted on the front steering/ forward and reverse casing and I can see the outside lever, this will in turn, by rods, operate the small lever on the side of the pre-select gearbox.

regards, Richard

[David Herbert]

This FV402 has a steering system that functions exactly the same as that in a T16. There is a Cletrac controlled differential with contracting band brakes running in oil in the central unit to provide the main steering function which when an outer steering lever is applied. this reduces the speed of one track and at the same time speeds up the other track by the same amount. A full application of one of these brakes will make one track go at about half the speed of the other with less difference / bigger radius of turn if you partially apply the brake.

Just inside the lower hull sides and mounted onto the final drive units are drum brakes with rod linkages to the stopping brake pedal and to the two central steering levers. Thus these brakes can be used either as the service brake (for slowing down / stopping) as a parking brake by pulling and latching the two centre steering levers, or for pivot turns in very confined situations by pulling just one centre steering lever.

Also inside the steering gearbox is the forward / reverse gearbox. This can only be changed with the vehicle stationary and the Wilson box in neutral. There is a neutral position in the F/R box but it is very unwise to try to engage F or R from N with the engine running - even with the Wilson box in neutral. There is too much drag in the Wildon box so the prop shaft etc will turn at about engine speed and the resultant grinding of gears in the F/R box is very destructive. Instead, stop, engage N in the Wilson box (or GC pedal to the floor which is what N position is) and smartly but not violently go straight from F to R or the other way. Do not pause in N or the propshaft will spin up.

The Wilson box contains 5 possible gears that can be engaged at any speed or load by pre selecting what you want next and then fully pressing and releasing the GC pedal. Do not use this as a clutch, but release it smartly in one movement. There is a fluid flywheel between the engine and Wilson box to cushion the drive and allow stopping in gear and progressive engement of the drive when starting off. When changing up or down match the engine revs to the next gear as you would with a manual box.

Unlike a T16 you are not supposed to use the Cletrac (outer steering levers) both together to stop the vehicle and there may well be an interlock to prevent you. This is a hangover from WW2 British tank designs as the Merrit Brown box in Cromwells etc would be damaged if you engaged both steering brakes.

This four lever system continued through the FV420 series into the pre production FV432s but then someone realised it was silly and production FV430 series got an ordinary Cletrac system with a more robust Cletrac controlled differential and no separate stopping brakes. This lasted untill modern civilian legislation required the FV430 series to be upgraded with a steering box that offered two separate braking systems.

David

[Michael R.]

I imagine your research quiry at The Tank Museum, Bovington, and to some extent other information sources as necessary, such as IWM, CWM and LAC may indicated your carrier is one of the Pilot models.

Are there a total of three (3) FV402 pilot models, or more? The Tank Museum, Bovington appears to hold FVPE 3818.

Two other known AOP No.4 FV402 series are:
FVPE 3816, Pilot model 1, UK Registration JXW 32
FVPE 3903, Pilot model 2, UK Registration KYW 36




IWM: Imperial War Museum, London
CWM: Canadian War Museum, Ottawa
LAC: Library and Archives Canada, Ottawa