SpringRC SM-S4303R Continuous Rotation Servo

SKU: POLOLU-1248 Brand: Pololu

The SM-S4303R is a standard-sized servo that has been built by SpringRC specifically for continuous rotation, making it an easy way to get your robot moving. It features two ball bearings on the output shaft for reduced friction, and it offers easy access to the rest-point adjustment potentiometer. This is the most popular continuous rotation servo Pololu carry. Key specs at 6 V: 54 RPM (no-load), 71 oz-in (5.1 kg-cm), 41 g

$30.43 AUD, inc GST

$27.66 AUD, exc GST

In stock, ships same business day if ordered before 2PM
Delivered by Mon, 29th of Apr

Quantity Discounts:

10+ $27.25 (exc GST)

Surplus units available: In October 2021, Pololu made a one-time purchase of surplus new SM-S4303R continuous rotation servos that Pololu are able to offer at specially discounted pricing. They are functionally identical this stock SM-S4303R servo except for the direction of rotation, which is reversed, and Pololu are selling them as pairs under a different product number (item #3448) to differentiate them. Please consider them as discounted alternatives to the Pololu's stock item #1248 servos while supplies last.

The SM-S4303R is a standard-sized servo that has been built by SpringRC specifically for continuous rotation. At 6 V, it has a maximum rotation speed of 54 RPM (no-load) and can produce up to 71 oz-in (5.1 kg-cm) of torque. It features two ball bearings on the output shaft for reduced friction, and it offers easy access to the rest-point adjustment potentiometer. The servo can be controlled using a direct connection to a single microcontroller I/O line without any additional electronics, which makes it a great actuator for beginner robotics projects.

The SM-S4303R continuous rotation servo converts standard RC servo position pulses into continuous rotation speed. The default rest point is 1.5 ms, but this can be adjusted by using a small screwdriver to turn the middle-point positioner. Pulse widths above the rest point result in counterclockwise rotation, with speed increasing as the pulse width increases; pulse widths below the rest point result in clockwise rotation, with speed increasing as the pulse width decreases.

The servo has an 11" (270 mm) lead that is terminated with a JR-style connector and includes additional servo horns and mounting hardware. The following picture shows an example of the hardware that might be included (actual hardware could vary):

This robotics servo is compatible with Pololu's servo controllers and has a Futaba-compatible output shaft, which means it works with Pololu's servo wheels for standard servos (25T, 5.8 mm spline). This servo is also compatible with Pololu's Mounting Bracket for Standard-Size Servos:

If you are looking for a similar servo that is capable of limited-range position control as opposed to continuous rotation speed control, consider the FEETECH FS5106B servo or Power HD standard servo 6001HB, which have comparable size, weight, speed, and torque.

Note: The spline on this servo is slightly bigger than on Pololu's other continuous rotation servos, so some servo horns and wheels might have a tight fit. If you find it difficult to push a compatible servo horn or wheel on by hand, please try the installation method shown in the video below. Similarly, the servo’s mounting tabs are a tight fit with Pololu's mounting bracket, so you might consider filing them or the mounting bracket down a little if you want to use them together.

Note that, as with most hobby servos, stalling or back-driving this servo can damage it.

Note: This servo is SpringRC part number SM-S4303R-CCW.

Continuous rotation servo comparison

Continuous rotation servo size comparison. From left to right: SpringRC SM-S4303R, Power HD AR-3606HB, FEETECH FS5106R, Parallax Feedback 360°, Parallax (Futaba S148), and FEETECH FS90R.

	Max speed (RPM)	Stall torque (oz·in)	Max speed (RPM)	Stall torque (oz·in)	Weight (g)	Size (mm)	Direction vs pulse (1ms ? 2ms)	Digital?	Feedback?	Price
	6 V		4.8 V		Weight (g)	Size (mm)	Direction vs pulse (1ms ? 2ms)	Digital?	Feedback?	Price

SpringRC SM-S4303R	54	71	43	46	41	41.3 × 20.7 × 40.2	CW?CCW			$15.95
SURPLUS SpringRC SM-S4303R 2-Pack	54	71	43	46	41	41.3 × 20.7 × 40.2	CCW?CW			$19.95 for a pair of servos
PowerHD AR-3606HB	71	93	62	83	40	40.5 × 20.0 × 38.0	CW?CCW			$16.95
FEETECH FS5106R	95	83	78	70	39	40.8 × 20.1 × 38.0	CW?CCW			$15.95
Parallax Feedback 360°	140	35	–	–	41	40.0 × 20.0 × 37.2	CW?CCW			$27.99
FEETECH FT90R	135	21	108	18	9	22.9 × 12.1 × 26.5	CW?CCW			$8.95
FEETECH FS90R	130	21	100	18	9	22.5 × 12.1 × 23.4	CW?CCW			$5.95

People often buy this product together with:

0.100" (2.54 mm) Breakaway Male Header: 1×40-Pin, Straight, Double-Sided

4-AA Battery Holder

Micro Maestro 6-Channel USB Servo Controller (Assembled)

Dimensions

Size:	41.3 × 20.7 × 40.2 mm
Weight:	41 g

General specifications

Digital?:	N
Speed @ 6V:	54 rpm
Stall torque @ 6V:	71 oz·in
Speed @ 4.8V:	43 rpm
Stall torque @ 4.8V:	46 oz·in
Hardware included?:	Y
Lead length:	11 in

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