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There are quite a few good drive options available for robots 30lbs and under. The primary vendors in this article are The Robot Marketplace, (robotmarketplace.com) FingerTech Robotics, (fingertechrobotics.com) Equals Zero Designs, (e0designs.com) and BotBitz. (botbitz.com)
In the case of some of the gearmotors presented below they are representative of several options or competing products that are essentially the same parts, be it different ratios from the same manufacturer or several variants on the same gearbox from multiple sources.
Name: 30:1 Micro Gearmotor (0-PL1093)
Specs:
Dimensions- 0.94 x 0.47 x 0.93” (24 x 12 x 10mm)
Nominal Voltage- 6V
RPM- 1000rpm
Stall Torque- 0.5in-lbs
Stall Current- 1.6A
Shaft- 3mm
Weight- 0.34oz
Cost- $15.95
Comments- This gearmotor is one of many variations of the same design. Two of the major sources for variations of this gearmotor are robotmarketplace.com and botbitz.com. These gearboxes are frequently used in the 150g and 1lb classes and are a decent option. In the 1lb class you will likely need 4 if you are not planning on a weapon focused machine. It is also advisable to protect or cover the exposed gears to prevent jamming or unnecessary damage during operation. The short shaft limits wheel options and makes external shaft support difficult. If you want an extremely light, compact gearmotor for a 150g – 1lb bot, this is worth considering.
Name: FingerTech Robotics Silver Spark (11:1 – 50:1)
Specs:
Dimensions- 0.63in (16mm) diameter, 1.58 – 1.63” long
Nominal Voltage- 6V
RPM- 850rpm for 11:1, 189rpm for 50:1
Stall Torque- 0.35in-lbs for 11:1, 1.6in-lbs for 50:1
Stall Current- 1.3A
Shaft- 3mm diameter, 1.5” long
Weight- 0.99 – 1.02oz
Cost- $22.94
Comments- The FingerTech Robotics Silver Spark gearmotor is a very well made and durable drive motor option for the 1lb class and has been used in weapon focused 3lb robots with a decent amount of success. With a wide range of ratios (11.1, 22.2, 33.3, 50, 83.3, 100, 200, 300, and 600:1) available it is easy to find an option that fits your needs. These motors are also capable of handling much higher voltages than their competitors and have been run as high as 22.2v (though >10V does decrease motor lifespan) in a combat application. The long shaft gives you plenty of options for both wheels and supplemental shaft support, though the latter isn’t often needed in the 1lb class. These gearmotors also have relatively large pitch gears and because of that they’re far less prone to stripping under load. This can often make the difference in a match and is one of the reasons they’re very commonly found in 1lb bots.
Name: Kitbots 1000rpm Gearmotor
Specs:
Dimensions- .98 – 1.03” diameter, 2.14” long
Nominal Voltage- 12v
RPM- 930rpm
Shaft- 4mm diameter
Weight- 3oz
Cost- $12.00 - $24.00
Comments- There’s very little in the way of dedicated gearmotors for the 3lb class right now, and the Kitbots 1000rpm gearmotor is at the top of the pile. This somewhat generic looking gearmotor is effectively the off the shelf drive option for the 3lb class. There are other gearmotors out there, but they’re often either difficult to attain, out of production or unrealistically expensive. Kitbots offers a “battle hardening” service that improves the durability of these gearmotors for $12 and it’s worth either having them do it or following along the instructions they have posted and doing it yourself. This motor is prone to voltage spikes so it is recommended that with some compatible ESC options you pair it with a 0.01uf capacitor to protect the motor controller.
Name: Gimson GR02
Specs:
Dimensions- 1.6” square, (40mm) 3.8” long
Nominal Voltage- 18V
RPM- 810rpm for 24:1, 542rpm for 36:1
Stall Torque- 106.8in-lbs for 24:1, 160.2in-lbs for 36:1
Stall Current- 61.6A
Shaft-12mm with flat
Weight- 1lb
Cost- £29.80
Comments- The GR02 is a gearmotor from the UK and is meant to function as a replacement for modified drill gearboxes in the popular 30lb class. With the size and weight of this gearmotor it is also suitable for the 12lb class. The shaft on the GR02 could be troublesome for some builders, however they offer a wheel hub solution that pairs with the 12mm shaft so that minimizes the issue. They’re also shipping the gearboxes with an external bearing kit which can be used to help handle the shock loads that often come with an overhung wheel drive setup.
Name: BotBitz GM36 19:1 Gearmotor
Specs:
Dimensions- 1.42” diameter, (36mm) 3.7” long
Nominal Voltage- 12V
RPM- 900
Stall Torque- 29.7in-lbs
Stall Current-52A
Shaft- 8mm with flat
Weight- 0.93lbs
Cost- $40AUD
Comments- The GM36 is the Australian solution to the same problem the GR02 was addressing in the UK. Cordless drill gearboxes are nice and off brand models can be quite cheap, but year to year the design, motors, and ratios can all change making it difficult to get a reliable, known motor. These gearmotors are also meant for the 30lb weight class, though are certainly compact and light enough for use in a 12lb robot. The 8mm shaft may be somewhat awkward to deal with and with that small of a shaft it would be wise to either protect the wheel from shock or add an outer support bushing/bearing to distribute the load.
Name: PDXNN Gearmotor/Banebots P60 Gearbox
Specs:
Dimensions- 1.5” square, 4.16” long
Nominal Voltage- 12V
RPM- 1500rpm for 16:1, 900rpm for 26:1
Stall Torque- 91in-lbs for 16:1, 145in-lbs for 26:1
Stall Current- 148A
Shaft- ½” diameter with keyway, 1.5” long
Weight- 15.9 - 16.05oz
Cost- $79.99 - $84.99
Comments- Robot Marketplace sells an assembled version of the Banebots P60 gearbox called the PDXNN, with NN being the ratio. Of the options, 16:1 and 26: 1 are the most practical. Banebots offers quite a few more ratios through their website as well. These gearmotors are a staple of the 12lb class. They’re not particularly expensive, easy to use, and reasonably durable. Three versions of the gearbox exist with each designed for a different common sized brushed DC motor. If you take care to protect the shaft and wheels these gearmotors are a solid option for the 12lb class and if four or more are used, at least an option for the 30lb class, though in that situation extra effort must be put into shaft protection and the addition of a shaft support is recommended.
Name: Robot Power Magnum 775
Specs:
Dimensions- 1.75” square, 4.92” long
Nominal Voltage- 14.4V
RPM- 720rpm
Stall Torque- 156.25in-lbs
Stall Current- 140A
Shaft- ½” diameter with keyway, 3” long
Weight- 28oz
Cost- $89.99
Comments- The Magnum 775 is the next step up from the P60. This gearbox is designed to work with an RS775 motor which is the largest option for the P60 gearbox. With a larger planetary gearbox and shaft supported by a dual bearing arrangement this gearbox is a solid option for the 30lb class. In a high shock environment a motor support plate like the one shown in the product picture is recommended, however it may not be needed for all applications. This is the largest currently available gearmotor solution that could reasonably be wedged into a 12lb robot.
Name: Equals Zero Designs DeWut?!
Specs:
Dimensions- 2.5” square, 6.1” long
Nominal Voltage- 18V
RPM- 450, 1450, 2000rpm selectable
Stall Torque- 162.4in-lbs estimated, middle gearing
Stall Current- 155A
Shaft- ½” diameter with keyway, 3” long
Weight- 2.9lbs with 3” shaft
Cost- $190.00 Assembled
Comments- The DeWut?! from Equals Zero Designs is an attempt to create a replacement for the no longer available Team Delta Power Drive Kit. Due to the size and weight the DeWut?! is primarily an option for the 30lb class. The three selectable gear ratios (51.2:1, 17.1:1, and 12.8:1) mean you have a solid range of speed options for most practical wheel sizes. These gearmotors are well designed, durable, and easy to use. Two DeWut?!s will provide plenty of power for a 30lb robot, though if you want even more there have been competitive 30lb robots made using four DeWut?!s.