Not to be a grouch, but if you have anti-gravity, why do you need a crane?
That's easy.
Because of the regulations according to Imperial occupational safety guidelines from about the end of the Indomitus Crusade around 111.M42.
It escapes me if it was Version 23334223223.4454675 or Version 23334223223.4453675.
You may inquire at your local Adeptus Mechanicus Authority (AMA) for a copy.
They may carve it into your living brain, before they remodel it into an occupational health and safety representative servo-skull serving on some scrap yard on Mars.
Coincidentially they need one there.
You can see that by the missing safety railing on that barge.
Sloppiness has increased in the Empire of Man since the Emperor is occupied with holding back demons, mexican drug cartells, alien refugees or something even more horrible.
Rumor has it, he even had to hire a couple of plumbers from Cormorragh to cobble together his golden toilet.
There goes the neighbourhood.
…
Beside, that is a levitational lifter.
Anti-Gravity does not exist.
Everybody knows that is pure fantasy!