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Technical Selection Guide<\/p>\n
The planetary gearbox mounting configuration<\/strong> determines how the unit transfers its reaction torque to the machine frame \u2014 and choosing the wrong one adds brackets, misalignment risk, and maintenance complexity that could have been avoided entirely at the specification stage.<\/p>\n<\/div>\n <\/p>\n Most OEM machine designers and procurement engineers focus on the torque rating and gear ratio when selecting a planetary gearbox \u2014 and reach the mounting configuration decision last, almost as an afterthought. This is the wrong order of operations. The mounting configuration determines the mechanical interface between the gearbox and the machine structure; changing it mid-project requires structural redesign of the mounting points and sometimes the motor position. Selecting it correctly at the concept stage eliminates a category of engineering problems entirely.<\/p>\n There are five primary planetary gearbox output shaft options<\/strong> encountered across industrial and mobile equipment applications: foot mount with solid output shaft, flange mount with solid output shaft, hollow shaft (shrink disc), splined hollow shaft, and torque arm. Each solves a different physical installation problem, and each has failure modes associated with incorrect application. This guide maps all five to the applications where they perform correctly.<\/p>\n<\/div>\n <\/p>\n <\/p>\n The foot mounted planetary gearbox<\/strong> is the simplest configuration: the gearbox housing has integral mounting feet that bolt directly to the machine base plate or floor mounting frame. The reaction torque is transferred through the feet into the structure. The output shaft connects to the driven machine via a coupling (jaw, gear, disc, or rigid type).<\/p>\n Where it fails:<\/strong> When the coupling alignment is not maintained at installation. A 0.1 mm parallel misalignment between the gearbox output shaft and the driven shaft creates a radial force on the output shaft bearing that is not within the gearbox’s design load. Over 2,000\u20134,000 hours this causes premature output shaft bearing failure \u2014 typically misdiagnosed as a gearbox quality problem. Laser-align all foot-mounted installations. Retorque mounting bolts at 200-hour run-in.<\/p>\n<\/div>\n <\/p>\n The flange mounted planetary gearbox<\/strong> bolts its housing flange directly to the mounting face of the motor or driven machine \u2014 no separate base plate or foot mounting structure required. This is the most space-efficient configuration and is standard for agricultural hydraulic motor drives (sprayer wheel drives, slurry spreader drives) and for compact industrial installations where the gearbox is co-located with the drive motor.<\/p>\n Critical point:<\/strong> The flange pilot diameter must be machined to the correct tolerance \u2014 typically H7 for the housing and h6 for the motor flange pilot. An undersized pilot bore causes housing offset that creates misalignment at the input shaft; an oversized pilot bore allows the gearbox to shift position under shock loading. Request the pilot bore tolerance specification from the supplier and verify it matches the motor flange before installation.<\/p>\n<\/div>\n <\/p>\n Most Widely Used<\/span><\/p>\n<\/div>\n The hollow shaft planetary gearbox<\/strong> eliminates the coupling entirely by mounting the gearbox output bore directly onto the driven shaft. The driven shaft passes through the hollow output bore and is clamped by a shrink disc (or taper bushing) that creates a friction-based torque connection. The reaction torque is taken through a torque arm attached to the gearbox housing.<\/p>\n This is by far the most widely used configuration for industrial conveyor drives, agitator drives, and drum drives because it eliminates: shaft alignment errors, coupling wear and replacement, and the axial space required by a coupling. Installation time is reduced by approximately 60% compared to a coupled foot-mount unit of equivalent torque.<\/p>\n Critical installation step:<\/strong> The shrink disc must be tightened to the manufacturer’s torque specification using a calibrated torque wrench \u2014 not an impact driver. Under-torqued shrink discs slip at peak torque events and cause fretting corrosion on the driven shaft bore. Over-torqued shrink discs distort the hollow output shaft bore and cause bearing misload. Both failure modes are preventable with a torque wrench and a 15-minute installation procedure.<\/p>\n<\/div>\n <\/p>\n Used where the driven shaft reverses direction under load at high frequency (winch drives, slewing drives, traversing drives). The spline transmits torque in both directions equally without the fretting that occurs at smooth-bore shrink disc interfaces under repeated reversal. The spline requires lubrication with MoS\u2082 grease at every assembly or removal event.<\/p>\n Typical applications:<\/strong> Hydraulic motor winch drives \u00b7 Excavator track drives \u00b7 Slewing machinery where reversal >50 cycles\/hour<\/p>\n<\/div>\n<\/div>\n Used in combination with hollow shaft or flange mount where no rigid mounting structure is available near the driven shaft. The gearbox “floats” on the driven shaft, with a single torque arm connecting the housing to a fixed structural point. The torque arm must be mounted at exactly 90\u00b0 to the housing centreline for correct load distribution; incorrect torque arm angle transfers bending load into the housing mounting bore.<\/p>\n Typical applications:<\/strong> Conveyor tail drums \u00b7 Belt scrapers \u00b7 Portable drive units on mobile machinery<\/p>\n<\/div>\n<\/div>\n<\/div>\n <\/p>\n If you are unsure which mounting configuration is correct for your application, work through these three questions in order:<\/p>\n Our inline planetary gearbox series<\/a> is available in all five mounting configurations across 16 frame sizes from 1,000 to 500,000 Nm. The NB300R right angle planetary gearbox<\/a> is available in foot mount and flange mount configurations with solid output shaft, covering right-angle applications requiring a 90\u00b0 change in shaft direction alongside the standard torque reduction.<\/p>\n<\/div>\n <\/p>\nThe Five Mounting Configurations \u2014 When Each One Is Correct<\/h2>\n
Quick Selection Guide \u2014 3 Questions to the Right Configuration<\/h2>\n