What Is a Beam Trolley? The Surround-Beam Design Explained
A beam trolley is the carriage that rides along a crane’s bridge beam and carries the hook point. Push it along the beam and the lift point moves with it — that’s how a load gets positioned along the span. On most cranes the trolley is a set of wheeled side plates clamped around the beam’s bottom flange; eme gantries use a different architecture, the surround-beam trolley, which wraps the beam entirely and rides on top of it.
The common design: bottom-flange trolleys
The trolley most people picture clamps onto an I-beam’s bottom flange: four wheels ride the flange’s top surface, the load bar hangs below, and the fit is adjusted to the flange width. It’s a proven design for running on building steel — and its failure modes are well understood: the wheels grip only the flange edges, so flange wear, incorrect width adjustment, or a cocked entry can let a wheel walk off.
The eme design: surround-beam
An eme trolley wraps around the box beam and rides on its top surface, with the load shackle hanging below the beam. Because the trolley surrounds the beam, it cannot come off in service — there is no flange edge to walk off; the beam itself is captive inside the trolley. End stops at the beam tips bound its travel. The wheels run on the wide, flat top of the proprietary box extrusion rather than gripping a flange lip, which is part of why the design pairs with a beam engineered for it.
That pairing is the point: eme trolleys are made specifically for eme beam profiles and are available only as part of the gantry line. They are not standalone accessories for other manufacturers’ beams, and a complete eme crane configuration includes the beam and its matched trolley — the trolley is part of the crane, not a separate purchase.
The three trolley families
The line uses three trolley families, named by their approximate weights, and sharing a family across capacities is deliberate — fleets running neighbouring classes stock one trolley class of spares:
| Family | Serves | Rated with |
|---|---|---|
| 15 lb trolley | 1100, 2200, and 4400 Series | 1,100–4,400 lb cranes |
| 35 lb trolley | 6600/8800 and 11000 Series | 6,600–11,000 lb cranes |
| 70 lb trolley | 22000 Series (dedicated) | 22,000 lb flagship |
The trolley in the load path
Everything hangs through the trolley: the hoist hooks into the trolley’s shackle, the trolley transfers the load into the beam, and the beam carries it to the legs. That’s why the trolley is inspected as structure — wheel wear, smooth travel, shackle and pin condition — and why every eme crane is load-tested to 125% of rated capacity as an assembled system, trolley included, before shipment. The full anatomy is in gantry crane parts.
The hoist itself is separate equipment, sized to the crane’s rated capacity and governed by its own standard (ASME B30.16).
Frequently asked questions
Can I use an eme trolley on another beam?
No. eme trolleys are profile-specific — the surround-beam geometry is machined to eme’s proprietary box extrusions and is sold only as part of an eme gantry configuration. A trolley matched to its beam is a load-path pairing, not a universal accessory.
Does a gantry crane come with a trolley?
A complete eme crane configuration includes the beam and its matched trolley. The hoist hangs from the trolley’s shackle and is purchased separately, sized to the crane’s rated capacity.
What’s the advantage of a surround-beam trolley?
It’s captive: because the trolley wraps the beam and rides on top, there’s no bottom flange for a wheel to walk off — the trolley cannot leave the beam in service. Positioning works the same as any push trolley; the security is structural, not procedural.
eme has been engineering lightweight and portable lifting equipment since 2003.