Also, I was thinking, Wouldn’t 4 motors with 7 oz-inches of torque add up to around 30 oz inches?
Hmmmm,
With that price ill only be able to afford 1 of these…
Can you not buy gearboxes separately?
Yea, thats what I suggested earlier, I was going to use 4 7.5 oz inch motors.
Also,
Final question,
How would I determine what power supply to get? (In terms of capacity). I am mainly looking for a rechargeable battery pack that ypu just plug into the chassis, and it then charges.
VEX parts are really only compatible with other VEX parts. We suggest considering other omni wheels or considering a VEX gear motor. Note that if you choose the VEX gear motor, you will still need a variety of other VEX parts (shaft, shaft collars etc) to mount the wheel.
If the wheel has rubber outer wheels, they should provide sufficient traction. However, if they are plastic, they won’t do much good.
The microcontroller can be run off a 12V battery, but the chip itself (and all the pins) run at 5V. You won’t need a regulator (though that is a good cheap one to get for future projects).
Can you provide a summary of the parts you are considering (provide links as well as quantities)?
Wiring is usually an afterthought but is very important. You need a wiring harness for the battery, and likely wires to connect everything together:
robotshop.com/en/wh-01-wiring-harness-battery-connector.html
robotshop.com/en/elenco-22-gauge-black-25-ft.html
robotshop.com/en/elenco-22-gauge-red-25-ft.html
robotshop.com/en/elenco-22-gauge-white-25-ft.html
If you are getting into robotics, pin headers and a soldering iron are also critical:
robotshop.com/en/sfe-straight-pin-headers.html
robotshop.com/en/solder-tool-kit.html
What would a “fair amount of time” be? You should choose a battery whose voltage is as close to the motor’s nominal voltage as possible. Then the higher the “amp hour” rating, the longer it will last (but the heavier the battery will be).
That should be ok. Yes there are other things to consider, especially the maximum discharge current. For example, if each motor consumes 500mA, and you have four of them, that’s a total of 2A which the battery needs to provide. An NiMh battery can discharge at 1 times its capacity, which in that case is 2.8A, so you should be find. However if each battery required 1A each (total of 4A), then that battery could not provide enough current.
Can you draw what you are planning to make? What would the 5th motor at the back do?
Those shields are best suited for charging 3.7V LiPo batteries. Most motors work best at 6V or 12V. Note that LiPo batteries do not necessarily have a higher capacity than other batteries.
What weight do they need to support, and how large do you need them (diameter)? Also, what is your budget per wheel?
If you use omniwheels with a 4WD chassis, there is nothing to prevent the robot from moving side to side. You would need Mecanum wheels. You would need this hub to mount them to the A4WD1 chassis. Note that you can purchase the A4WD1 without the wheels or motors.
The 48mm Omniwheel for LEGO NXT, Servo is almost the same price, and you can use one of two motors: the 1425CR or a DC gear motor.
Omniwheels don’t work very well outdoors at all - we’d suggest 2WD or 4WD (not rack and pinion as in a normal car).
Correct. Changing the speed and direction of rotation of the motors can make you turn gradually or on the spot.
Differential drive is a good choice and can be used indoors and outdoors. You can use casters on the rear. The speeds depends on the DC gear motors you choose. It can turn very quickly.
That’s just a DC motor; it rotates quickly but has very little torque. You need a DC gear motor. Consider the following tool to give you an idea of the torque and ROM of the motor you’ll need:
RobotShop Drive Motor Sizing Tool
The stall for that motor is 20oz-in, which is the torque you get when the shaft cannot rotate any more because there is too much resistance - if you reach stall, the motor will fry. The normal “continuous” torque you can get from a motor is around 1/5 to 1/4 the stall torque, which in this case would be 6-7.5oz-in. You would need a 4:1 gear box in addition to that motor.
The torque is multiplied by 4, so if the maximum continuous torque was ~7oz-in, it would be 28 oz-in after the gear-down. The speed would decrease by a factor of four to 1937.5 (which is still pretty fast). Note that the final speed of the robot also relates to the diameter of the wheel.