Speed Reducers



The AmpFlow speed reducer is a heavy-duty, low-cost, gearhead that works with any of the three-inch diameter AmpFlow motors.

This speed reducer uses a unique three-stage chain-and-sprocket mechanism that reduces cost while still maintaining high torque capacity.

This unit provides speed reduction and torque multiplication, and it's an easy way to "bolt-in" the AmpFlow motors.



We stock ten different gearmotors or we can design custom gearmotors:

Type High-Performance Mid-Range Economy
Model A28-400-G A28-150-G F30-400-G F30-150-G E30-400-G E30-150-G
Peak Horsepower 4.3 3.0 3.0 2.3 2.1 1.0
Motor Diameter (inches) 3.0 3.0 3.1 3.1 3.1 3.1
Reduction Ratio 8.3:1 8.3:1 8.3:1 8.3:1 8.3:1 8.3:1
Stall Torque (in-lbs) 1930 1020 1300 710 770  360
Nominal Voltage 24* 24* 24* 24* 24* 24*
No-Load RPM 580 720 540 830 680 670
Pounds 10.4 7.3 11.8 8.2 9.4 7.1
Price $639 $534 $479 $429 $299 $269
Pictures A28-400-G A28-150-G F30-400-G F30-150-G E30-400-G E30-150-G
Drawings A28-400-G A28-150-G F30-400-G F30-150-G E30-400-G E30-150-G
Performance Charts A28-400-G A28-150-G F30-400-G F30-150-G E30-400-G E30-150-G

* The above specifications are for 24V. The motors can also be used at 12V or 18V. The RPM is proportional to the voltage so running at 12V will result in half the no-load RPM that is shown above for 24V. The lower voltage also reduces the maximum achievable torque by 50%. The motors have also been tested and used at higher voltages resulting in higher RPM, torque, and power. Shorter duty-cycles are recommended for higher voltages to allow the motors time to cool.


NEW! Fan Cooled Motors

Type Fan Cooled  24V Fan Cooled 48V  
Model A28-400-F24-G A28-150-F24 A28-400-F48 A28-150-F48    
Peak Horsepower 4.3 3.0 11.5* 4.6    
Motor Diameter (inches) 3.0 3.0 3.0 3.0    
Reduction Ratio 8.3:1 8.3:1 8.3:1 8.3:1    
Stall Torque (in-lbs) 1930 1020 3740** 1290    
Nominal Voltage 24V 24V 48V 48V    
No-Load RPM 580 720 750 880    
Pounds 10.6 7.5 10.6 7.5    
Price $689 $584 $689 $584    
Pictures A28-400-F24-G A28-150-F24 A28-400-F48 A28-150-F48    
Drawings A28-400-F24-G A28-150-F24 A28-400-F48 A28-150-F48    
Performance Charts A28-400-G A28-150-G A28-400-F48 A28-150-F48    

The fan-motors have ventilation holes in the front and rear aluminum plates to allow for flow-through cooling. The holes in the front plate are positioned so they are not blocked when mounting the motor to a flat surface. These motors also feature low-profile motor leads for better fit into smaller spaces.

* Theoretical peak power is 11.5 HP. Power at the recommended short-term current limit of 200A is 9.1 HP.
** The current required to reach 3740 in-lbs is far outside the safe operating limits of this motor. This figure is theoretical and should be used for comparative purposes only.
*** Available for pre-order now. Estimated shipping date is 1/15/16. Credit cards will not be charged until motor is shipped.

Recommended 48V motor speed controllers from IFI will be available soon. Please contact us by email to be notified when the controllers become available:


These speed reducers are made with a three-piece aluminum case that has been precision CNC machined. A total of six sprockets, three roller chains, and five bearings comprise the mechanism. The long output shaft makes it easy to mount pulleys, sprockets, gears, or wheels in the required position. Care was taken to make this unit as compact as possible. The overall dimensions are 6 inches x 3 inches x 2 inches. But the motor is recessed slightly into the reducer, so the net length added to the motor is only 1.8 inches.

The speed reducer uses a unique arrangement of roller chains. This results in torque and efficiency comparable to gear-type reducers at just 1/2 or even 1/3 of the cost of high-torque, geared speed reducers. There is slightly more noise, but these units are ideal when silent operation is not required.



The output shaft is 3/4-inch diameter and 2.2 inches long. It has a 1/4-inch keyway and a 5/16-24 tapped hole. The shaft and the large final sprocket are made from a single piece of steel to maximize strength. If something other than the 1/4-inch key is required, step key stock is available.

A single stage of roller chain reduction is generally considered to be about 98% efficient. Add in some friction from the five bearings and we are at about 90% efficiency.




                Torque Test

This picture shows the speed reducer undergoing a torque capacity test. The motor is locked and unable to turn. Weight is loaded onto the end of the 40-inch bar until the speed reducer fails. The failure point is 3500 inch-pounds. This gives an almost 2-to-1 margin of safety when used with the A28-400.

The failure point is the chain on the last stage of speed reduction. The gearbox suffered no other damage. The $10 chain was replaced and it's as good as new.


                Backlash Test


The gearhead is tested for backlash by locking the motor in place. A load of 200 ounce-inches is applied in both clockwise and counter clockwise directions. The total deflection is +/- 1.2 degrees. This figure may increase somewhat with higher loads and chain wear, but replacement chains are available.






Four long 1/4-20 bolts go all the way through the width of the reducer. The four mounting bolts are supplied with the unit. They are sufficient in length to mount the gear motor to a 3/8-inch thick panel. If the panel is thicker, longer bolts will be needed. Do not operate the speed reducer with bolts that are missing or too short - they are required for structural integrity.



Wheel/Gearmotor Combo



Our Wheel/Gearmotor combination can be configured with your choice of six different wheel sizes and ten different motors. Visit the WheelMotors page for details.

Here are our recommendations regarding the selection of a proper reduction ratio.


Replacement Parts


Output Shaft with Sprocket - $48      Quantity

#25 Chain - $10      Quantity

#35 Chain - $12      Quantity

Ball Bearings (set of three) - $24      Quantity

Bronze Bearings (set of three) - $10      Quantity





The gearmotors are warranted to be free from manufacturing defects, and fully operational when you receive them. AmpFlow gives no other warranty, either expressed or implied. Warranties are not transferable. In no event shall AmpFlow's liability exceed the buyer's purchase price, nor shall AmpFlow be liable for any indirect or consequential damages.

The speed reducers are not available un-mounted. Please contact us if you are interested in mounting these speed reducers on other motors. Shipments must be to a street address; we can not ship to a PO Box. Please allow 7-10 days for orders shipped by UPS ground, 3-4 days for orders shipped by 2nd day air, and up to 14 days for international orders.

  We accept Visa, MasterCard, and PayPal.

Replacement brushes are available here

Contact us for custom gearmotors and volume pricing.


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