CASE STUDIES
What Is a Shaft-Mounted Gear Motor? Uses and Advantages
What is a shaft-mounted gear motor?
A shaft-mounted gear motor is a gear motor whose output shaft mounts directly onto the shaft of the machine it drives, with no coupling in between. The gearbox has a hollow output shaft, a bore that slides straight over the driven shaft, so the drive passes from one to the other directly.
The unit itself still has to be fixed to something. It is mounted onto the machine, or onto another support structure next to it, and in most installations it is the machine itself. What the arrangement removes is the coupling between the drive and the machine, not the need to support the gear motor.
How it mounts
Two things are involved in fitting a shaft-mounted unit:
- The hollow shaft takes the drive. The gearbox's output bore fits over the machine's shaft and is locked to it, commonly with a key or a shrink disc, so the two turn together.
- The support holds the gear motor and stops it rotating. Under load the gearbox tries to turn around the shaft, so it is anchored, commonly with a torque arm or bracket fixed to the machine or a nearby structure.
Because the output shaft sits on the driven shaft, there is no coupling to buy, align and maintain between the gear motor and the machine.
The hollow shaft, explained
The hollow shaft is the feature that makes this mounting possible. An ordinary gearbox has a solid output shaft that a coupling connects to. A shaft-mounted gearbox has a hollow bore instead. The driven machine's shaft passes into that bore and is clamped, so the gearbox drives it directly. This is why these units are also called hollow-shaft gearboxes.
The advantages
Driving the machine shaft directly brings several practical benefits:
- Direct transmission of power. The output shaft turns the driven shaft with nothing in between.
- Fewer parts. No separate coupling to buy, align and maintain.
- Saves space. The drive sits on the machine rather than on its own baseplate beside it.
- Quicker to fit and remove. The unit slides on and off the shaft, which simplifies installation and later maintenance.
| Point | Shaft-mounted gear motor | Foot-mounted gear motor with coupling |
|---|---|---|
| Drive connection | Output shaft directly on the driven shaft | Through a coupling |
| Coupling | Not needed | Needed, and must stay aligned |
| Support | Fixed to the machine or a nearby structure | On a baseplate or foundation |
| Floor space | Sits on the machine | Takes space beside the machine |
| Fitting | Slides on and off the shaft | Mount, align and couple |
Where shaft-mounted gear motors are used
Shaft-mounted units are common on conveyors, mixers, agitators and similar machinery, where the drive can sit directly on the driven shaft. They suit installations where floor space is tight, where a coupled drive would be awkward to align, or where quick removal for maintenance is valuable. The gear type inside is chosen for the speed and the load. The shaft-mounted arrangement is about how the drive reaches the machine.
To see the geared motors AVM supplies, visit the shaft mounted geared motors category.
Frequently asked questions
What is a shaft-mounted gear motor?
A gear motor whose output shaft mounts directly onto the machine's driven shaft, with no coupling between them. The unit is still fixed to the machine or a support structure.
Does a shaft-mounted gear motor need a coupling?
No. That is the point of the arrangement. The output shaft drives the machine shaft directly, so the coupling and its alignment are removed.
What holds the gear motor in place?
It is mounted to the machine or a nearby structure, commonly through a torque arm or bracket that stops the gearbox turning around the shaft under load.
What is a hollow-shaft gearbox?
The same idea. Instead of a solid output shaft, the gearbox has a hollow bore that fits over the driven shaft, so it can drive the machine directly.
Why choose a shaft-mounted gear motor?
It transmits power directly, removes the coupling, saves floor space and is quick to fit and remove, which suits conveyors, mixers and tight installations.