Self-levelling system jacks work in pairs?

[Robert P]

Thinking of getting a self-levelling system fitted to moho but I read that the jacks operate in pairs "to avoid twisting the chassis". Now, if the moho is down, for example, on the nearside front wheel how can operating the jacks in pairs correct the slope? If you are down at one corner, the chassis is twisted and operating the appropriate jack alone would untwist it. So is operating jacks in pairs a problem or not in real-life operation?

 

[denisejoe]

I think they auto level as there would not be much point

 

[Pablotti]

There are 4 jacks, but 4 possible moving pairs. Only one pair will move at any time to prevent twist.

If on uneven ground without the rams, your suspension is preventing chassis twist. The rams are not sprung, which is why only one pair can operate at a time

 

[Two on Tour]

That's why it's called a self levelling system because the brain box in the system has a set point of what level is and it adjusts the pressure in each pair jack as it levels to maintain what it understands as level from that set point in systems brain box.

 

[Southdowners]

They level automatically. Ours all go down to the ground which I expect give the system the gradient which it needs to level out. They then raise the vehicle up the required amount on each jack (I think at the same time) and then do a bit of ‘fine tuning’ at the end to get it exactly level.

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[David and Sally]

A pair of jacks reach the ground and take a small amount of weight then stop. Another pair of jacks do the same. At this point all the jacks will be at different extends. Then, a pair of jacks level side to side as a pair, then a pair level front to back as a pair.

That's how our HPC system does it.

 

[Mrjenben]

I think it avoids twisting because it applies equal pressure to the jacks in pairs.

So if one wheel was down originally there will be less load on that corner because the chassis will transfer some of the load to the opposing wheel.

Applying the jacks in pairs mean that it will effectively raise the lower wheel first and take any twist out of the chassis until the load is even across the pair.

They never apply pressure to an individual jack at any point of the autolevelling.

If you’re on a diagonal slope then the pressures will be equal but by operating say the front pair and then the side of the tilt then one jack common to both will raise more, effectively raising that corner.

 

[Theonlysue]

Keeps the windscreen safe as well.

 

[Robert P]

Thank you everybody, that explains things and is very helpful. I notice nobody recommended following Mr Punch's advice!