Calculations for weight-lifting motor....

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Discussion Overview

The discussion revolves around selecting an appropriate 12 V electric motor with a gearbox for lifting a 20 kg weight using a spindle. Participants explore various motor options, considerations for environmental exposure, and the feasibility of designing custom gear systems.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant calculates the required torque for lifting a 20 kg weight and expresses difficulty in finding a suitable motor with a gearbox.
  • Another suggests using a cordless drill as a potential solution, noting its availability and suitability for the task.
  • Some participants emphasize the importance of identifying the usage profile for the application before selecting a motor.
  • Concerns are raised about the environmental exposure of the motor, with suggestions for protective measures.
  • One participant mentions the possibility of using a generously overrated motor and designing a custom gear train and housing, though they acknowledge the increased cost this would entail.
  • Another participant warns against stalling an electric motor, indicating it may not be advisable for the intended application.
  • There is mention of 24 V DC gear motors being available that could meet the torque requirements, though it is unclear if this is a preferred option.

Areas of Agreement / Disagreement

Participants express differing opinions on the best approach to selecting a motor, with some advocating for off-the-shelf solutions like cordless drills, while others suggest custom designs. There is no consensus on the optimal motor choice or design strategy.

Contextual Notes

Participants note various factors that could affect motor selection, including required output speed, duty cycle, and environmental durability. The discussion reflects uncertainty regarding the availability of motors that meet all specified criteria.

Who May Find This Useful

Individuals involved in robotics, engineering projects requiring motor selection, or those interested in practical applications of electric motors in challenging environments may find this discussion relevant.

ramzerimar
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The project I'm building involves a 12 V electric motor connected to a spindle lifting a 20kg weight. The radius of the spindle is 2cm, so the torque applied by the weight is 0,02m*20kg*9,8m/s^2, which gives me 3,92N*m. So, my 12 V motor needs to deliver 3,92N*m just to keep the weight steady. This is 40kgf*cm of torque.

I'm having trouble to select a motor appropriate for this task. First of all, the project that I'm designing will be placed on the chassis of a car, so it needs to be very trustworthy and robust (it will be exposed to all kinds of environmental effects). Also, to lower costs, I don't want to design any gearbox to increase torque, so I think it would be better if the motor in question already included the gearbox. I searched for all kinds of 12 V gear motors, but haven't found anything within those limitations.

Could you give me any hints on how to proceed? Would designing a gearbox will be my only way out? Also, all DC motors that I've found are used primarily in robotics, automation... I'm not sure if this kind of motor is
recommended for this application.
 
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Do you have a cordless screwdriver/drill ... They are around the power you are looking for ...you can easily test it by winding a cord around a drill and seeing if it will lift the weight ...such electric drills are often thrown away when the battery dies ...

You are correct not to try to add a gearbox onto a motor , best to buy a motor with a gearbox , this will not be waterproof ... better to by a cheap cordless drill , these are a little better with regard to the elements , and will probably be cheaper than buying a motor.
 
A few key strokes will find you multiple sources for 12 V motors with gearboxes .

Before that though you need to properly identify the usage profile for your application .
 
oz93666 said:
Do you have a cordless screwdriver/drill ... They are around the power you are looking for ...you can easily test it by winding a cord around a drill and seeing if it will lift the weight ...such electric drills are often thrown away when the battery dies ...

You are correct not to try to add a gearbox onto a motor , best to buy a motor with a gearbox , this will not be waterproof ... better to by a cheap cordless drill , these are a little better with regard to the elements , and will probably be cheaper than buying a motor.

I will certainly give a look at that. Thanks!

Nidum said:
A few key strokes will find you multiple sources for 12 V motors with gearboxes .

Before that though you need to properly identify the usage profile for your application .

Indeed, I've found some 12 V motors with gearbox, but most of them don't have the torque that I need. Most of these are small DC motors for robotics and automation.

The project I'm building will be exposed to environmental effects (sun, rain) so I need to think about some way to protect the motor from these effects.
 
Last edited:
Nidum said:
Personally I would use a generously overrated motor and design my own gear train and housing .

I've thought about designing my own gear train, but that would increase the cost too much.
 
ramzerimar said:
The project I'm building involves a 12 V electric motor connected to a spindle lifting a 20kg weight. The radius of the spindle is 2cm, so the torque applied by the weight is 0,02m*20kg*9,8m/s^2, which gives me 3,92N*m. So, my 12 V motor needs to deliver 3,92N*m just to keep the weight steady. This is 40kgf*cm of torque.

I'm having trouble to select a motor appropriate for this task.
How fast do you want to lift it? That's pretty important too.
 
russ_watters said:
How fast do you want to lift it? That's pretty important too.
Probably something like 2cm/s. The speed is not a critical issue in the project
 
ramzerimar said:
So, my 12 V motor needs to deliver 3,92N*m just to keep the weight steady

It's not usually a good idea to "stall" an electric motor if that's what you are planning.
 
  • #10
24VDC gear motors are available in the market with your requested torque
 

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