nicam wrote:

Interesting vehicle - I wonder how they got the drive ratio front to back correct?
It looks as though the rear sprocket diameters are a lot smaller than the front tyre diameter so will need to run much faster.
Presumably it must have a suitable ratio diff on the front end of the track unit as the front and rear prop shaft speeds will be the same.
Also, it sounds like the ultimate understeer vehicle from his description

nicam wrote:

Interesting vehicle - I wonder how they got the drive ratio front to back correct?
It looks as though the rear sprocket diameters are a lot smaller than the front tyre diameter so will need to run much faster.
Presumably it must have a suitable ratio diff on the front end of the track unit as the front and rear prop shaft speeds will be the same.
Also, it sounds like the ultimate understeer vehicle from his description

The question on diff ratios got me thinking and with lock down there is plenty of time for this!!!
So here we go with some complete speculation

According to this video, it used a Jag diff and another webpage I found said it had inboard discs at the rear which I suspect means it used a Jag rear axle unit.



There were a wide range of diff ratios available for the Jag rear axle.

I can't find any info on the diameter of a standard CVR T drive sprocket. But if it had standard 7.50 x 16 front tyres, they have a rolling circumference of 99.9" according to google.

If I've got the maths right, and they put a standard 4.7:1 LR diff in the front, then for every turn on the prop, the vehicle would move by 21.1"

If they used the lowest ratio jag diff at 2.88:1 for the rear, then I think the sprocket would need to have a circumference of 60.8" to generate the same 21.1" of travel. That gives a diameter for the sprocket of 19.4". Hard to tell from the photos what size the sprocket is but I don't think it is as big as 19.4"

If they used a standard series box in the early versions then they would most likely run in rear drive only on good ground, so a slight difference in prop speeds wouldn't be an issue until they engaged 4wd. With the later Range Rover box, I guess the centre diff would cope with a small variation in prop speed and it would only become an issue when they locked the centre diff.

As money was often not an issue on these projects, they could have had a custom rear diff made with a suitable ratio to match the CVR T sprocket size to the 7.50 x 16 front tyre size, running any of the standard LR diff ratios up front.

Does anyone know more about the transmission set up? With a Jag rear end, they could even have incorporated a limited slip diff as I believe some Jags had these.

Pacha wrote:

They will be independent of each other and (poss) separate to the steering.

This will allow one of the tracks (the inside one) to be braked to slew the thing similar to a tank.

Supacat wrote:

Would like to have seen more on the engineering and how it was all put together...

For those interested in this type of thing I got a Corona virus care package from the Tank Museum shop recently:


Click image to enlarge

all this for just over £40, which I thought was excellent value and helps support them when there's no money coming in the front door.

Definitely worth taking a look and seeing what floats your boat:

https://tankmuseumshop.org/