The PB21B-3R is the larger of the two TRUEMAX spider concrete placing booms. It stands on the same free-standing inclined-outrigger base as the compact 17 m model, but reaches 21 m — covering a noticeably bigger bay from each set-up, so a wide floor is poured in fewer positions and with fewer crane moves. The longer boom is turned by a gear-slewing drive rather than the worm gear of the smaller spider, suited to the extra mass and reach. As with every spider boom, it is not fixed to the structure: it is set down on its legs, pours its area, then is lifted by crane to the next.
That makes the PB21B-3R the spider to choose when reach matters more than minimum weight — large slabs, podiums and rafts where a 17 m boom would need more relocations to cover the same floor. It is fully hydraulic with a three-arm R-fold boom and 360° slewing, fed by a separate concrete pump rather than pumping itself, and run by radio or cable remote. At 9,150 kg with a heaviest single lift of 5,850 kg it needs a more capable crane to relocate than the compact model, a fair trade for the wider coverage. It runs on a 380V/50Hz supply with a 7.5 kW motor, built and tested at TRUEMAX in Haining to ISO 9001:2015 and CE standards, within a line exported to over 120 countries.
1. 21 m reach for bigger bays — The larger spider covers more floor from each set-up than the 17 m model, cutting the number of positions and crane moves needed to pour a wide slab.
2. Gear-slewing drive — A gear-slewing turret rotates the longer, heavier boom through a full 360° — matched to the extra reach and mass of this size.
3. Inclined-outrigger spider base — The splayed-leg base gives a stable, fixed working stance on the slab without anchoring into the structure, then lifts free for relocation.
4. Three-arm R-fold hydraulic boom — Three fully-hydraulic R-fold arms open to the 21 m radius and fold compactly for crane handling and transport.
5. Relocated by site crane — The boom is craned between positions; at a 5,850 kg maximum lifting unit it suits projects with an adequately sized tower or mobile crane.
6. Radio and cable remote control — Wireless radio and cable remotes let one operator place concrete across the wide bay from the best vantage point.
7. Full 360° coverage — Complete rotation places concrete all around the set-up position, maximising the area each stance covers.
8. Quality components — Hydraulic and electrical parts from well-known international brands for stable, reliable operation, on a 380V/50Hz, 7.5 kW drive.
