I’ve previously searched for DC motors and found no shortage of “1-inch” motors. However, those are rather large for my intended use as a tiny Raspberry Pi Zero machine, and besides, I’ve seen smaller motors than that in a 90’s era Minolta compact automatic film camera, 1 cm diameter to be exact. So, now I go searching for smaller DC motors. And indeed, “10 mm” is the key search term to include.
20191119/DuckDuckGo 10 mm dc micro motor
20191119/https://nfpshop.com/product/10mm-vibration-motor-15mm-type-model-nfp-110-003
There’s plenty of choices on Digi-Key around the 10 mm size range. Most of them are 5-6 V DC motors.
20191119/https://www.digikey.com/products/en/motors-solenoids-driver-boards-modules/motors-ac-dc/178?FV=-8%7C178%2C46%7C393585%2C46%7C393589%2C46%7C393591%2C46%7C393593%2C46%7C393606%2C46%7C393610%2C46%7C393611%2C46%7C393612%2C46%7C393628%2C46%7C393633%2C46%7C393644%2C46%7C393645%2C46%7C393646%2C46%7C393685%2C46%7C393714%2C46%7C393715%2C46%7C393738%2C46%7C393779%2C46%7C393808%2C46%7C393816%2C46%7C393821%2C46%7C393824%2C46%7C393826%2C46%7C393844%2C46%7C397585%2C46%7C397586%2C46%7C397589%2C46%7C397593%2C46%7C397594%2C46%7C397595%2C46%7C397597%2C46%7C397602%2C46%7C397603%2C46%7C397609%2C46%7C397623%2C46%7C397628%2C46%7C397637%2C46%7C397638%2C46%7C397640%2C46%7C397644%2C46%7C397650%2C46%7C397651%2C46%7C397662%2C46%7C397683%2C46%7C397706%2C46%7C397712%2C46%7C397721%2C46%7C397723%2C46%7C397729%2C46%7C397741%2C46%7C406679%2C46%7C406711%2C46%7C406724%2C46%7C406726%2C46%7C406741%2C46%7C406745%2C46%7C406755%2C46%7C406768%2C46%7C406769%2C46%7C406787&quantity=0&ColumnSort=46&page=2&pageSize=25
Here are a select few choices for example.
20191119/https://www.digikey.com/product-detail/en/dfrobot/FIT0482/1738-1262-ND/7087159
20191119/https://www.digikey.com/product-detail/en/pimoroni-ltd/COM0806/1778-1127-ND/6873670
How do you know how much torque you can get out of a DC motor? Compute the power from the voltage and current draw ratings, then convert to torque using the following example, also using the RPM rating.
T = (POWER in Watts) * 9.549 / (SPEED in RPM)
T = (750 W) * 9.549 / (2000 rpm)
= 3.6 (Nm)
You get the resulting torque in Newton-meters, which you can convert to pound-inches if you’d prefer.
1 newton meters = 8.85075 inch pounds
20191119/DuckDuckGo dc motor compute strength
20191119/https://www.engineeringtoolbox.com/electrical-motors-hp-torque-rpm-d_1503.html
Some really tiny motors are marked up as “ERM vibration motors.” Essentially, these are motors designed solely to generate vibrations inside of pagers, cell phones, smartphones, and other such mass market mobile communications devices.
20191119/DuckDuckGo ERM vibration motor
20191119/https://www.precisionmicrodrives.com/content/ab-004-understanding-erm-vibration-motor-characteristics/
20191119/https://www.precisionmicrodrives.com/vibration-motors/eccentric-rotating-mass-vibration-motors-erms/
What if you want an even smaller motor than is possible with the smallest of DC motors? Consider if you can use a solenoid instead. These are often used on mechanical systems that need only two states of motion, and they can be built to be smaller than the smallest of DC motors. Some solenoids may also be three-state or four-stage.
Now, what about steering mechanisms for small car-style devices? Two main styles. For maximum maneuverability, there is “skid-steer” where you have one motor to control left-side wheels and one motor to control right-side wheels. For example, “skid-steer loader Bobcat” machines. For maximum straight-line speed/torque on a finite power budget, there is one large main motor for driving the forward wheels and a second smaller motor for controlling tilt-style wheel steering. For example, conventional on-road motor vehicle cars.
20191119/https://en.wikipedia.org/wiki/Skid-steer_loader
20191119/https://en.wikipedia.org/wiki/Differential_steering
Finally, the simplest case of vehicle steering worth mentioning, lest the moderner forget, requires only a single motor whatsoever: on-track “railroad-style” navigation. The vehicle only has a single motor for forward and reverse, and all steering guidance is performed by the tracks themselves.