172:1 Metal Gearmotor 25Dx56L mm HP

100% of 100
SKU: POLOLU-1577 Brand: Pololu
This cylindrical, 2.2" x 0.98" x 0.98" gearmotor uses a brushed DC motor with extra-strong magnets and a 171.79:1 metal gearbox to deliver a lot of power in a relatively small package. These units have a 0.315"-long, 4 mm-diameter D-shaped output shaft. Pololu also carry a lower-power version of this gearmotor. Key specs at 6 V: 57 RPM and 450 mA free-run, 260 oz-in (18.7 kg-cm) and 6 A stall. (Note: stall torque and current specifications are theoretical values; stalling the motor is likely to damage the gearbox.)
$47.95 AUD, inc GST
$43.59 AUD, exc GST

Available with a lead time
Expect dispatch between Jul 30 and Aug 05

Quantity Discounts:

  • 10-25 $42.28 (exc GST)
  • 25+ $41.41 (exc GST)
- +

0 from local stock, 1 supplier stock; your order will dispatch between Dec 1 to Dec 10. And yes, stock levels and lead times are accurate!

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These cylindrical brushed DC gearmotors are available in a wide range of gear ratios and with five different motors (two power levels of 6 V motors and three power levels of 12 V motors). The gearmotors all have the same 25 mm diameter case and 4 mm diameter gearbox output shaft, so it is generally easy to swap one version for another if your design requirements change (though the length of the gearbox tends to increase with the gear ratio). Each version is also optionally available with an integrated 48 CPR quadrature encoder. See the 25D metal gearmotor datasheet (2MB pdf) for more information, including detailed performance graphs for each gearmotor version. You can also use Pololu's dynamically sortable 25D gearmotor comparison table to search for the version that offers the best combination of speed, torque, and current draw for your particular application. A more basic comparison table is available below.

Gear Ratio No-Load Speed
Stall Torque
Max Power

Without Encoder

With Encoder
(kg · cm) (oz · in)
12 V High-Power
5.0 A 250 mA

300 mA
1:1 (no gearbox) 10,000 0.4 5.5 10 item #4840
4.4:1 2200 1.7 24 9.4 item #3201 item #4841
9.7:1 1000 3.9 54 10 item #3202 item #4842
20.4:1 500 7.4 100 9.4 item #3203 item #4843
34:1 300 11 150 8.9 item #3204 item #4844
47:1 220 15 210 8.4 item #3205 item #4845
75:1 130 22 310 item #3206 item #4846
99:1 100 29 400 item #3207 item #4847
12 V Medium-Power
1.8 A 80 mA

100 mA
1:1 (no gearbox) 8200 0.17 2.4 3.5 item #4860
4.4:1 1800 0.71 10 3.2 item #3225 item #4861
9.7:1 800 1.7 24 3.4 item #3226 item #4862
20.4:1 380 3.2 44 3.1 item #3227 item #4863
34:1 230 4.7 65 2.8 item #3228 item #4864
47:1 170 6.4 89 2.8 item #3229 item #4865
75:1 100 8.5 120 2.3 item #3230 item #4866
99:1 79 11 150 2.3 item #3231 item #4867
172:1 46 18 250 2.1 item #3232 item #4868
227:1 35 24 330 item #3233 item #4869
12 V Low-Power
0.9 A 50 mA

60 mA
1:1 (no gearbox) 5600 0.14 1.9 1.8 item #4880
4.4:1 1200 0.53 7.4 1.7 item #3249 item #4881
9.7:1 580 1.3 18 1.8 item #3250 item #4882
20.4:1 280 2.4 33 1.7 item #3251 item #4883
34:1 170 3.7 51 1.6 item #3252 item #4884
47:1 120 4.8 67 1.4 item #3253 item #4885
75:1 75 7.1 99 1.4 item #3254 item #4886
99:1 57 8.7 120 1.2 item #3255 item #4887
172:1 33 13 180 1.1 item #3256 item #4888
227:1 25 16 220 1.0 item #3257 item #4889
378:1 15 23 320 item #3258 item #4890
6 V High-Power
6.0 A 420 mA

500 mA
1:1 (no gearbox) 10,000 0.3 4 7 item #4800
4.4:1 2200 1.2 17 6.7 item #1570 item #4801
9.7:1 1000 2.3 32 5.9 item #1571 item #4802
20.4:1 480 4.8 67 5.9 item #1572 item #4803
34:1 290 6.8 94 5.1 item #1573 item #4804
47:1 210 9.1 130 4.9 item #1574 item #4805
75:1 130 14 190 4.5 item #1575 item #4806
99:1 99 15 210 3.9 item #1576 item #4807
172:1 57 27 380 item #1577 item #4808
6 V Low-Power
2.0 A 100 mA

120 mA
1:1 (no gearbox) 6200 0.15 2.1 2.1 item #4820
4.4:1 1300 0.63 8.7 2.1 item #1581 item #4821
9.7:1 630 1.3 18 1.9 item #1582 item #4822
20.4:1 290 2.5 35 1.9 item #1583 item #4823
34:1 180 3.9 54 1.7 item #1584 item #4824
47:1 130 4.8 67 1.5 item #1585 item #4825
75:1 80 7.5 100 1.5 item #1586 item #4826
99:1 61 9.1 130 1.4 item #1587 item #4827
172:1 35 14 190 1.2 item #1588 item #4828
227:1 27 17 240 1.1 item #1589 item #4829
378:1 16 25 350 item #1590 item #4830
499:1 12 31 430 item #1591 item #4831

Note: The listed stall torques and currents are theoretical extrapolations; units will typically stall well before these points as the motors heat up. Stalling or overloading gearmotors can greatly decrease their lifetimes and even result in immediate damage. The recommended upper limit for continuously applied loads is 4 kg·cm (55 oz·in), and the recommended upper limit for intermittently permissible torque is 8 kg·cm (110 oz·in). Stalls can also result in rapid (potentially on the order of seconds) thermal damage to the motor windings and brushes; a general recommendation for brushed DC motor operation is 25% or less of the stall current.

In general, these kinds of motors can run at voltages above and below their nominal voltages (they can begin rotating at voltages as low as 1 V); lower voltages might not be practical, and higher voltages could start negatively affecting the life of the motor.

Details for item #1577

Exact gear ratio: 22×20×22×22×22×22×2412×12×10×10×10×10×10171.79:122×20×22×22×22×22×2412×12×10×10×10×10×10˜171.79:122×20×22×22×22×22×2412×12×10×10×10×10×10˜171.79:1


The diagram below shows the dimensions of the 25D mm line of gearmotors (units are mm over [inches]). This diagram is also available as a downloadable PDF (171k pdf).

Dimensions of the Pololu 25D mm metal gearmotors without encoders. Units are mm over [inches].

Warning: Do not screw too far into the mounting holes as the screws can hit the gears. Pololu recommend screwing no further than 6 mm (0.24") into the screw hole.

Gearmotor accessories

The face plate has two mounting holes threaded for M3 screws. You can use Pololu's custom-designed 25D mm metal gearmotor bracket (shown in the picture below) to mount the gearmotor to your project via these mounting holes and the screws that come with the bracket.

Pololu 25D mm metal gearmotor bracket pair.

Pololu 25D mm gearmotor with bracket.

The 4 mm diameter gearbox output shaft works with Pololu multi-hub wheels as shown in the left picture below. That shaft also works with the Pololu universal aluminum mounting hub for 4mm shafts, which can be used to mount Pololu's larger Pololu wheels (60mm-, 70mm-, 80mm-, and 90mm-diameter) or custom wheels and mechanisms to the gearmotor’s output shaft as shown in the right picture below.

Pololu 80×10mm multi-hub wheel on a Pololu 25D mm metal gearmotor with encoder.

Pololu 60×8mm wheel with 4mm hub adapter on Pololu 25D mm metal gearmotor with encoder.

Alternatively, you could use Pololu's 4mm scooter wheel adapter to mount many common scooter, skateboard, and inline skate wheels to the gearmotor’s output shaft as shown in the left picture below. For a general-purpose hex adapter, consider Pololu's 12mm hex wheel adapter, which lets you use this motor with many common hobby RC wheels as shown in the right picture below.

A 25D mm gearmotor with encoder connected to a scooter wheel by the 4mm scooter wheel adapter.

12mm hex wheel adapter for 4mm shaft on a 25D mm metal gearmotor with encoder.

These are the same type of motors used in the Wild Thumper all-terrain chassis, so the gearbox’s output shaft also works directly with the hex adapters included with the 120mm-diameter Wild Thumper wheels as shown in the image below:

Dagu Wild Thumper wheel 120×60mm (metallic red) and Pololu 25D mm metal gearmotor with encoder.

Pololu have a number of motor drivers and motor controllers that work with these 25D mm metal gearmotors. For the LP and MP versions, Pololu recommend Pololu's TB9051FTG-based drivers, for which Pololu have a basic single carrier, a dual-channel shield for Arduino, and a dual-channel expansion board for Raspberry Pi. For the HP versions, Pololu recommend Pololu's VNH5019-based motor drivers (available as single and dual carriers), though these can also be a good choice for the lower-power motors.

TB9051FTG Single Motor Driver Carrier.

Pololu dual VNH5019 motor driver shield for Arduino.

If you are looking for higher-level control interfaces, such as USB, RC, analog voltages, I²C, or TTL serial, consider Pololu's Simple Motor Controllers, Jrk motor controllers, or RoboClaw motor controllers; these controllers are available in various power levels, and the appropriate one depends on the particular version of 25D mm motor you have (we generally recommend a motor controller that can handle continuous currents above the stall current of your motor).

High-Power Simple Motor Controller G2 18v15.

Jrk G2 21v3 USB Motor Controller with Feedback.

RoboClaw 2×7A Motor Controller (V5B) in its included case.

Pololu have an assortment of Hall effect-based current sensors to choose from for those who need to monitor motor current:

ACS711EX current sensor carrier -15.5A to +15.5A.

ACS714 current sensor carrier -5A to +5A.

Selecting the right gearmotor

Pololu offer a wide selection of metal gearmotors that offer different combinations of speed and torque. Pololu's metal gearmotor comparison table can help you find the motor that best meets your project’s requirements.

People often buy this product together with:

Pololu Universal Aluminum Mounting Hub for 4mm Shaft, #4-40 Holes (2-Pack)Pololu Universal Aluminum Mounting Hub for 4mm Shaft, #4-40 Holes (2-Pack)
99:1 Metal Gearmotor 25Dx54L mm HP 6V99:1 Metal Gearmotor 25Dx54L mm HP 6V
Pololu 25D mm Metal Gearmotor Bracket PairPololu 25D mm Metal Gearmotor Bracket Pair


Size: 25D x 56L mm1
Weight: 94 g
Shaft diameter: 4 mm2

General specifications

Gear ratio: 171.79:1
No-load speed @ 6V: 57 rpm3
No-load current @ 6V: 0.42 A4
Stall current @ 6V: 6.0 A5
Stall torque @ 6V: 27 kg·cm5
Motor type: 6V, 6.0A stall (HP 6V)

Performance at maximum efficiency

Max efficiency @ 6V: 30 %
Speed at max efficiency: 46 rpm
Torque at max efficiency: 5.2 kg·cm
Current at max efficiency: 1.4 A
Output power at max efficiency: 2.5 W

General specifications

Encoders?: N


Length measurement is from gearbox face plate to back of motor (it does not include the output shaft or motor terminals). See dimension diagram for details.
D shaft.
Typical; ±20%.
Typical, ±50%; no-load current depends on internal friction, which is affected by many factors, including ambient temperature and duration of motor operation.
Stalling is likely to damage the gearmotor. Stall parameters come from a theoretical extrapolation of performance at loads far from stall. As the motor heats up, as happens as it approaches an actual stall, the stall torque and current decrease.

File downloads

Product Comments

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  • Pickup - Free! Only available to customers who live in the Newcastle region (must order online and only pickup after we email to notify you the order is ready). Orders placed after 2PM may not be ready until the following business day.

Non-metro addresses in WA, NT, SA & TAS can take 2+ days in addition to the above information.

Some batteries (such as LiPo) can't be shipped by Air. During checkout, Express Post and International Methods will not be an option if you have that type of battery in your shopping cart.

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If you order lots of gear, the postage amount will increase based on the weight of your order.

Our physical address (here's a PDF which includes other key business details):

Unit 18, 132 Garden Grove Parade
NSW, 2289

Take a look at our customer service page if you have other questions such as "do we do purchase orders" (yes!) or "are prices GST inclusive" (yes they are!). We're here to help - get in touch with us to talk shop.

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