Bridge Crane End Truck Wheel Specification
The bridge crane end truck translates motor drive force into crane travel and supports the full weight of the bridge, trolley, and lifted load on the runway rails. UTEC Industrial manufactures precision-machined alloy steel crane wheels, sheaves, and industrial components from AISI 4140, 4340, and 8620 billets in the Pacific Northwest, with in-house induction hardening, CNC machining, and chemistry testing on every heat. End truck wheel specification integrates load calculation, tread profile selection, bore and axle configuration, and flange clearance into a complete assembly that must fit the end truck geometry without modification. UTEC Industrial machines end truck wheels to customer drawings with all critical dimensions controlled and documented.
What wheel configurations are used in overhead bridge crane end trucks?
Two-wheel end trucks: two wheels per end truck (four total per crane), common for smaller cranes up to approximately 20–30 tons capacity. Each wheel carries half the end truck reaction load. Four-wheel end trucks: four wheels per end truck (eight total per crane), used for larger cranes where a two-wheel configuration would require excessively large wheel diameters. The maximum wheel load is the end truck reaction divided by four (two wheels per rail side), substantially reducing required wheel diameter and contact pressure. Equalizing trucks (rocker trucks): a four-wheel sub-assembly where the four wheels are mounted in two pairs, with each pair on a rocker beam that equalizes load between the two wheels in the pair — ensures all four wheels carry equal load even on imperfect runway rail.
How does wheel count per end truck affect the load calculation?
Maximum wheel load decreases with increasing wheels per end truck. For a 4-wheel end truck: maximum wheel load per wheel = (runway rail reaction) / 2 (two wheels per rail side), then compared to CMAA formula. The reduction in maximum wheel load from 2-wheel to 4-wheel end truck can allow a smaller wheel diameter or a lower service class constant, reducing cost. However, 4-wheel end trucks require longer end truck frames, which increases the bridge span and dead load — these interact in the load calculation. The crane manufacturer's end truck design establishes the wheel count; replacement wheels must match the original count and geometry exactly.
What is the standard bore and axle configuration for bridge crane end trucks?
The most common configuration for overhead bridge crane end trucks is: dead shaft (fixed axle bolted to end truck frame) with the wheel rotating on bearings pressed into the wheel bore. The wheel bore houses a pair of tapered roller bearings or spherical roller bearings whose outer rings are pressed into the bore. The dead shaft passes through the bearing inner rings. For drive wheels, a live shaft (rotating with the wheel) configuration is used, with the motor driving the shaft through a coupling or gear reducer. Replacement wheels must match the original configuration — dead shaft (bearing bore) or live shaft (keyed interference bore). UTEC Industrial confirms bore configuration before machining any bridge crane end truck wheel.
What tolerances and features define a complete end truck wheel drawing?
A complete end truck wheel drawing specifies: wheel diameter, tread profile and face width, flange height and angle (double-flange standard), bore diameter and tolerance class (IT6 for dead shaft bearing bore; IT7 for light interference on live shaft), bore length, keyway dimensions if drive wheel, hub face geometry, hub-to-hub (overall) width, tread-to-bore runout tolerance (≤ 0.005 inches TIR), tread surface finish (Ra 125 standard), alloy grade (AISI 4140 or 4340), tread hardness range (BHN), effective case depth (minimum), and post-quench temper requirement. UTEC Industrial uses this complete specification as the basis for all end truck wheel production.
- Crane Wheel Selection Guide for Overhead and Bridge Cranes — complete bridge crane specification including end truck wheel selection
- Live Shaft vs. Dead Shaft Crane Wheel Configurations — end truck shaft configuration types
- Crane Wheel Load Capacity and CMAA Service Classifications — load calculation basis for end truck wheel sizing
References
- CMAA Specification No. 70: Specifications for Top Running Bridge and Gantry Type Multiple Girder Electric Overhead Traveling Cranes. Crane Manufacturers Association of America.
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