The NE and NR series gearheads are older legacy gearheads, originally designed in the early 90s. These were spur gearheads with low accuracy, typically used with stepper motors, though low accuracy applications with servos were also possible.
The NE were an inline spur gearhead. The new PV series gearheads are an inline planetary gearhead. The PV series is planetary with straight-cut gears, with higher torque and better accuracy and longer life.
The NR were a right-angle spur gearhead. The new RX series gearheads are a right-angle planetary gearhead. The RX series is planetary with Stealth helical gears with higher torque and better accuracy and longer life.
Both the PV series and RX series offer similar dimension on the output face (shaft diameter and length, pilot diameter and depth, bolt circle and through-hole) as a bolt on replacement.
The PV and RX series are available with better pricing and faster delivery.
The NE and NR series gearhead output direction depended upon the ratio of the gearhead, where the PV and RX series directions are all the same regardless of the ratio: Shaft Rotation
Related FAQ: Gearhead Rotation Direction
The NE and NR gearheads mounting kits were a pinion only if a true Nema dimension motor (MM23-000, MM34-000, MM34-016 or MM42-000). All other mounting kits for other dimension motors included an adapter flange. The pinion was tightened onto the motor shaft at a specific distance, to engage the first gear cluster within the gearhead.
The PV series Planetary Value line uses the MV mounting kits. The MV and MU mounting kits are similar in design.
The RX series Stealth Gen II use the MU mounting kits. The RX uses universal mounting kits that are only an adapter flange and bushing. This allows the gearhead to be entirely built and the mounting kits use standard adapter flanges that are modified for the motor dimensions.
To find the appropriate mounting kit, use the motor manufacturer and model number with the web-base mounting kit search tool: Gearhead Mounting Kit Search Tool
Or if you have the MM mounting kit number, here's a crossover list:
The NR series were typically purchased with single output shaft. The NR also had dual output shaft and encoder shaft options. These are standard options on the MultiDrive series gearhead but that is a metric dimension gearhead and starts in a 90mm size. This is quite different; we recommend a redesign to incorporate a newer gearhead.
Note the 3:1 for the NR series right-angle gearheads isn't a standard option on the RX series. The RX series has ratios starting at 5:1 going up to 100:1. The RB series MultiDrive gearhead is offered in a 3:1 ratio but is a metric dimension gearhead:
For full specifications, see PV and RX series gearhead product pages.