Tatra lorry rear suspension

UK PROFESSIONAL DRIVERS FORUMS THE UK PROFESSIONAL DRIVERS FORUM (INTERACTIVE)
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I just come up with a thought I was wondering in the past, and trucknet can be the best place to ask.

Most of you propable never saw the Tatra tipper, but they were (and still are) very popular in many countries, not only in Eastern Europe.

The point is: the rear suspension.

See the position of the rear wheels:

Can’t find any picture with a rear view

(except of that one, quite impressive, but it do not shows what I need:
)

So, coming back to the first one: see the wheels, they are not vertical, but in some angle.

If you are following the lorry and it’s empty, you can actually see, that the inner wheels are not touching the ground at all, and the lorry goes only on the edges of the outer wheels.

What’s the point of this kind of suspension? I guess driving on the tyre edges do not help with saving tyres… It can be also dodgy drivingwise… But as we can see from the off-road picture, the suspension has amazing range…

So is it done to enhance it’s off road skills? Or there is another reason?

And if it’s a good solution (Tatra was making these lorries for years and they were very appreciated) is there any other make using that?

(note: if the lorry is heavy loaded, it looks as every other ordinary lorry with all four wheels from rear axles driving fully on the ground).

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Tatra the King of the Tipper trucks on the continent (70-80’s) en.wikipedia.org/wiki/Tatra_(company

Unbelievable strong and fantastic road hold off-road, as long as they where loaded.

Tatra was the first (and only?) truck with INDEPENDENT suspension, they use swing axles for the driven axles.
This type of suspension was considered better than the more typical live axle for two reasons:

1.It reduced unsprung weight since the differential is mounted to the chassis
2.It eliminates sympathetic camber changes on opposite wheels
However, there are a number of shortcomings to this arrangement:

1.A great amount of single-wheel camber change is experienced, since the wheel is always perpendicular to the driveshaft
2.“Jacking” on suspension unloading (or rebound) causes positive camber changes on both sides, which (In extreme cases) can overturn the car.
3.Reduction in cornering forces due to change in camber can lead to over-steer – a dynamically unstable condition where a vehicle can lose control and spin – and in extreme cases lift-off over-steer.

Skoda Estelle, Volkswagen any many other ones used it on their cars and vans.
Quote: en.wikipedia.org/wiki/Swing_axle

I can remember them well they where that time always wearing “Barum” tyres which was a unknown brand that time but a fantastic tyre for the quarries and off-road.
The trucks and tyres where designed for the that time extreme poor Eastern Europe roads, so they withheld themselves very good in Holland and Germany, if they only had been rust proofed. :unamused: :unamused: :unamused: :unamused:

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Sorry double posted :blush:

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Ever seen truck trials on sky channels, often see tetras in that and they really do go anywhere!

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this shows what your are talking about with the suspension movement Orys :slight_smile: (I think :blush: )

This is pretty impressive tbh

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Those are impressive!

Can`t imagine our ASDA Scanias doing that… :laughing: :laughing:

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The concept of swinging half-axles is not that uncommon, you can find it on many passenger cars, particularly those rear-engined rear wheel drive - already mentioned older skodas, vw beetle, porsche… ledwinka and porsche knew each other.
In trucks, apart from Tatra, there was also Austrian Pinzgauer using the same concept of central tube chassis and swinging half axles on their light off road vehicles; sometime in 1930s there was a short-lived brand spangler or sprengler, founded by a hungarian guy in the US, they made few vehicle that looked like built on Tatra chassis…
The main advantage is high mobility - left-side wheels are independent from right-side one so the vehicle can cope with a terrain that brings “normal” vehicle to a halt.
There are disadvantages too, for example you cannot mount a body directly onto tube chassis so you need a subframe = reduced payload - but in off-road applications overloading is not a issue. Uneven tyre wear is another, but again, off the road where punctures are part of every day life you don’t really care about uneven wear.
Older Tatras really ride on outer edges of outer wheels when empty, tyre rotation is one way to cope with it when the truck is used on the road.
The camber is significantly reduced on newer Tatras, year ~2000 onwards, where they have coil spring inside air bag above the chassis tube; heavy-duty version has additional leaf spring, but not so stiff as in the past so it does not push the wheel away from the truck so much.
On cars the camber is not that obvious, because wheels of a lorry need more travel to cater for payload and rough terrain.