Newbie from NZ

[AndyUK]

Hi Richard

Have you considered long stroke linear actuators?

I suggest these because they're usually rated in terms of the force they can apply (which should be an easier calculation) and are often provided with 12/24V compatible systems which might be useful given the mobile environment. They should be cheaper than a ballscrew, because unlike a CNC you're not looking for a high degree of accuracy in this use case (1mm is probably close enough!).

The one disadvantage I can see is they might not be the quickest of options ;)

BW,
Andy