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27 votes
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Understanding required torque for a motor lifting a weight

You have the right concept, but slipped a decimal point. 5 cm = 0.05 m. The gravitational force on your 450 g mass is 4.4 N as you say, so the torque just to keep up with gravity is (4.4 N)(0.05 m) =...
  • 11.3k
22 votes

Effective ways to drive a single shaft with multiple motors?

While a mechanical differential does what you ask, you don't really need it. You can connect two identical electric motors together on the same shaft. There is no "slipping out of sync" because ...
  • 11.3k
22 votes

Effective ways to drive a single shaft with multiple motors?

A differential is a mechanical device designed to do exactly what you propose. It will allow the two motors to spin at slightly different rates while still combining the power. The most common use ...
21 votes
Accepted

What is this small rotating part from a cell phone?

These types of motor configurations are used in the cellphone's vibrate/buzzer function. Here is a Youtube video demonstrating the vibrate function and two other references: How it works:Cell phone ...
16 votes
Accepted

How can I calculate the power and torque required for the motor on a wheeled robot/vehicle?

I laid everything out so you should only need to read it from top to bottom and look backwards for variables, never forward. I also tried to lay it out so hopefully you know where everything is coming ...
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13 votes
Accepted

Why does public transport uses compressed air to open doors instead of electromotors?

Do you mean, for example, a bus entry door? It may be as simple as the "service factor" for motors ("electromagnetic devices") as compared to pneumatics. Inexpensive motors with sintered bronze ...
  • 355
13 votes
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Avoid snapping an electric cable from too much rotation

The device you are looking for is called a slip ring such as the one shown below. These devices use internal components which maintain contact as they spin (old ones used brushes) allowing them to ...
12 votes
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Calculating torque needed to climb a graded hill

I think you're overcomplicating things. To push 85 kg up a 15% slope against gravity of 9.8 m/s2 requires a force of $$ \sin (\arctan (0.15) ) = 0.1483 \approx 0.15 $$ $$F = 85 kg \cdot 9.8 \frac{m}...
  • 6,814
10 votes
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How to fix this gear

Oddly enough, this problem can be fixed using a set of car keys and your wallet. Here are the steps to follow: 1) put the keys in the ignition of your car, start it, and drive to the motorcycle ...
10 votes

Does a motor suffer damage when resistance to the intended motion is met?

The answer depends on the specific type of motor you intend to use, but in general: when a motor is loaded down, it draws more current, which means its windings get hotter at the same time that the ...
8 votes

What is Starting Torque?

There are two different aspects to start-up torque. One is associated with the motor and the other with the system which you are trying to drive. The start-up torque of a mechanical system is the ...
7 votes

Why does public transport uses compressed air to open doors instead of electromotors?

They are smoother and if something gets caught in between them then the maximum force it can exert is capped depending on the pressure and the piston area. This means that a trapped limb is less ...
7 votes
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Rotating two shafts together - coupling rod?

The usual solution is to use gears, possibly with a toothed belt or chain to connect them. A single connecting rod like you show is not sufficient — there's an ambiguity when the rod is at the ...
  • 6,814
7 votes
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Meaning of O-slash in data sheet about gear diameter?

In the lower right corner of the document/drawing, you can see four (or five) lines of text upward: UNIT: mm Another piece of useful information in the data panel is the scale, shown there as 3:1. ...
  • 6,562
7 votes

Does a motor suffer damage when resistance to the intended motion is met?

It depends on the specific type of motor, as @nielsnelson mentions, but it also depends on what you use to drive the motor. In general, a motor that's designed to run continuously isn't going to take ...
  • 2,283
7 votes
Accepted

Building an ultralight electric hoist, what gearbox reduction / motor combination for torque / power requirements?

Relatively low lifting requirements (100 kg) Relatively fast lifting speed (80 fpm -> .4 m/s) The first part of your power calculation was wrong. There's no need to go into pulley diameters at ...
  • 406
7 votes

How do I start looking for a cheap encoder?

In the past whenever I needed a rotary encoder, I took apart a computer mouse. I do not know if they will meet your requirements, but there's nothing cheaper.
6 votes

What is Starting Torque?

Is the torque required to make something that is not turning start turning. You can think of starting torque as an instantaneous value (the torque just before the motor starts moving). You can also ...
  • 356
6 votes

What is Starting Torque?

"Starting torque" and "locked-rotor torque" are the same thing. So if you run across the later term, you can treat it as a synonym for "starting torque." The NEMA MG-1 definition of locked-rotor ...
  • 360
6 votes

What is the use of gears in a device with a fixed gear ratio?

Electric motors typically only operate well at high speeds, and compared to something like an internal combustion engine, relatively low torque. Fixed gear ratios are used to cope with this inherent ...
  • 81
6 votes

What is this small rotating part from a cell phone?

That is a micro vibrating motor to produce the "buzz" effect from your phone. I used much much larger vibrating motors, air driven, on the bottom of my Class 7 dump truck. Mounted under the bed, they ...
6 votes

What is the use of gears in a device with a fixed gear ratio?

A given mass of copper and iron can only produce so much torque : increasing torque further would require more current which means (a) the increased magnetic flux saturates the iron and (b) the I^2R ...
  • 1,600
6 votes
Accepted

How does load force impact load inertia?

Let's first compute the model. The control design is a separate effort. The torque applied to the drum is $n T_M $, where n is the gear ratio and $T_M$ is the output produced by the motor. $T_M= K_T ...
  • 1,901
6 votes

Why isn't it possible to build a car moved by wind power?

The fundamental problem in this case is that the turbine in not powered by 'wind' as such but by the relative motion of the car through the air. This is not 'free' energy, because the turbine must ...
  • 15.1k
6 votes
Accepted

How does a windshield wiper work?

For having dismantled a wiper motor once, The basic principle is exactly as shown on the video, but the wiper is then linked to the to the rotation point of the rocking bar and not to the bar itself. ...
  • 325
6 votes
Accepted

Why do the lights dim when I turn on a mitre saw?

The wires in your home have resistance. Current going through those wires causes a voltage drop. The startup (inrush) current of electric motors can be several times their normal operating current. It'...
  • 365
6 votes

Working out Motor torque

The biggest unknown you need to determine or guess is the coefficient of rolling friction. For reference, a coefficient for rolling friction of 0.3 is already very high and is for something like for ...
  • 4,320
6 votes

Ways to brake an axle

In the wire & cable business, the device you describe is called a dancer, for the way its components move about while regulating the tension in a rope or wire being unspooled from a large coil. ...
5 votes
Accepted

What would happen if we tried to run a motor in space when it is not attached to anything to provide support to it?

Initially Assume an ideal motor with no mechanical losses and Operation in a perfect vacuum. Call the two portions rotor and stator - with all attached parts such as controller and power pack ...

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