Linear Electric Motor - Page 1
Forum section: electronics / beginners

author: electromateria
author_rank: Regular Contributor
timestamp: May 24, 2022, 08:20:36 pm
content: I'm curious about this motor design, it's really cool. Can it actually generate a respectable amount of torque? Can the length and stroke of the shaft be increased? Has anyone made a well refined version of this? What are the main downsides of using this style of design as opposed to a conventional motor with a reciprocating mechanism?

author: Benta
author_rank: Super Contributor
timestamp: May 24, 2022, 08:31:34 pm
content: That's not a "linear motor". It's a solenoid. And it doesn't produce "torque", but force.Typical application in millions and millions: automotive door locks, magnetic valves... you name it.The cr*p you see on YT. Jeez....

author: BrokenYugo
author_rank: Super Contributor
timestamp: May 24, 2022, 09:00:34 pm
content: Torque is a rotational force.As Benta points out, the technical term is "solenoid", for both the coil and the actuator.https://en.wikipedia.org/wiki/Solenoid_(engineering)

author: james_s
author_rank: Super Contributor
timestamp: May 24, 2022, 10:06:03 pm
content: Quote from: Benta on May 24, 2022, 08:31:34 pmThe automotive door lock actuators I've opened up all had a small DC motor like the sort used in toys, with gears to translate the rotation to linear motion. Solenoids certainly have plenty of other applications although they typically just pull in against a spring, that one looks like it has magnets so it technically could be called a motor I suppose.

author: Benta
author_rank: Super Contributor
timestamp: May 24, 2022, 10:15:25 pm
content: Could well be true for US cars. The sound revals it: a "bzzt-clack" is the motor type.EU cars almost all have the solenoid-type which just makes a "zack" when opening/closing.Doesn't change my opinion on the ridiculous "linear motor" video.

author: BeBuLamar
author_rank: Super Contributor
timestamp: May 24, 2022, 11:06:34 pm
content: Yup that thing is a solenoid and not a motor. Of course there are linear motor but not like that.

author: electromateria
author_rank: Regular Contributor
timestamp: May 24, 2022, 11:17:19 pm
content: I'm familiar with linear actuators, those are generally slow and used for opening / closing things. Those "motors" in the video (to me it seems like an accurate descriptor) seem like they could work well for fast moving reciprocation tasks if they produce enough force. I like the simplicity and how compact it is.If I were to use a regular motor + reciprocation mechanism it would take up much more space, but it would definitely put out a functional amount of torque -> force..There's lots of videos about "solenoid engines" but in the couple videos that show what kind of force / torque it can generate it looks pathetic. Can solenoids put out significant force if used as fast moving recipricators? I assume no, but I'm unsure.

author: james_s
author_rank: Super Contributor
timestamp: May 25, 2022, 12:10:58 am
content: Quote from: Benta on May 24, 2022, 10:15:25 pmThe cars I've worked on are Volvo and Saab, from early 80s to late 90s, so about as European as cars get, but it's possible things have changed. I would describe the noise as just a click really, the motor is fast enough that I assumed it was a solenoid until the first time I had to take one apart to figure out why it wasn't working.

author: james_s
author_rank: Super Contributor
timestamp: May 25, 2022, 12:15:28 am
content: Quote from: BeBuLamar on May 24, 2022, 11:06:34 pmThe dictionary definition of an electric motor: "a machine that converts electrical energy into mechanical energy by means of the forces exerted on a current-carrying coil placed in a magnetic field"I would say that a solenoid such as this with a permanent magnet plunger fits the definition of a motor, albeit not in the conventional sense. Likewise the head actuator in some optical drives is a linear motor consisting of a coil sliding over a magnetic stator, that is also called a motor though it contains no rotating parts.

author: electromateria
author_rank: Regular Contributor
timestamp: May 25, 2022, 06:45:24 am
content: "This raises an important question—what’s the difference between an actuator and a motor? Theanswer is subtle and relates to the device’s function, not its structure. A motor is a device that con-verts energy into motion. An actuator is a specific type of motor whose motion is intended to controlanother mechanism.For example, one common application of a linear actuator is to control the position of a mechanicalswitch. In this case, the actuator is called a relay. Other actuators open and close valves. In contrast,if a device’s purpose is simply to effect motion, such as spinning the wheels of a remote-controlledcar or rotating the propellers of a quadcopter, it’s a motor, not an actuator.Another difference between linear actuators and linear motors involves the nature of the inputpower. Every linear actuator I’ve encountered requires DC power, but as later sections will show,linear synchronous motors and linear induction motors rely on AC power."Source: Motors for Makers A Guide to Steppers, Servos, and Other Electrical Machines

author: SmallCog
author_rank: Frequent Contributor
timestamp: May 25, 2022, 10:22:47 am
content: If you want to see linear motors in action watch a YouTube video about the Disney people moversThere are of course plenty of videos on solenoids too.

author: Benta
author_rank: Super Contributor
timestamp: May 25, 2022, 10:42:09 am
content: If you want to see large-scale linear motors, check out maglev trains.https://en.wikipedia.org/wiki/Maglev

author: Terry Bites
author_rank: Super Contributor
timestamp: May 25, 2022, 12:32:41 pm
content: Our Eric (the original inventor) shows you the way

author: eugene
author_rank: Frequent Contributor
timestamp: May 25, 2022, 02:12:43 pm
content: It's true that solenoids have been around for as long as copper wire, but I think you guys are making too much of the word "motor." When you apply power to a solenoid it generates a force on a plunger causing the plunger to move in a linear direct. Typically, it stops when it hits something, but that's because it has finite travel. That's exactly the same behavior seen in a rotary motor, except for the travel limits and the obvious fact that the rotary motor rotates. You can add a position encoder to either, provide a feedback loop, and have a positioning device.A solenoid is admittedly extremely simple, but that's kinda the point of the videos. It's closely related to a voice coil, and everyone in the speaker industry refers to the magnet and voice coil as the "motor."Yes, the videos seem silly and hyperbolic if you're already familiar with solenoids, but they're suitably interesting and useful to someone without that experience. It's a step up from giving directions on how to make an electromagnet with an iron nail and some wire. Just right if that's where you are in your education.

author: TimFox
author_rank: Super Contributor
timestamp: May 25, 2022, 04:08:03 pm
content: Before I retired, we referred to "actuators" as devices that moved between mechanically-defined limits, or stops. They could be a solenoid, or a rotary motor through a lead screw, to force the system from one stop to the other.We used some expensive linear motors that were the electrical equivalent of three-phase servo motors, with a track of magnets between the bearing rails, as described in this manufacturer's site (although they call them "actuators"):https://www.kollmorgen.com/en-us/blogs/_blog-in-motion/articles/how-does-direct-drive-linear-actuator-work/(In this context, "servo motor" generally indicated rotating permanent magnets inside stator coils, but for linear motors the coils were on the moving platform.)

author: Benta
author_rank: Super Contributor
timestamp: May 25, 2022, 04:28:34 pm
content: Quote from: eugene on May 25, 2022, 02:12:43 pmEveryone is free to make up his/her own terms and words. By that token the videos show a "nuclear reactor" to me.The problem with that approach is, thatanytechnical/engineering communication is then dead. This forum would be dead. Everyone would be talking at cross-purposes.Not the best idea IMHO.

author: Terry Bites
author_rank: Super Contributor
timestamp: May 25, 2022, 05:18:22 pm
content: I've just made up a word.

author: Terry Bites
author_rank: Super Contributor
timestamp: May 25, 2022, 05:29:11 pm
content: Quote from: Benta on May 25, 2022, 04:28:34 pmYep. That's why searching suppliers websidtes is a pig. What did they call it....?

author: eugene
author_rank: Frequent Contributor
timestamp: May 25, 2022, 05:32:07 pm
content: Good grief.Quote from: Benta on May 25, 2022, 04:28:34 pmI completely agree with the basic premise. My friends, coworkers, and relations are tired of hearing me rant about needless abuses to the English language. (Don't get me started on the verbs "damp" and "dampen.")But, I still think that rejecting the video out of hand simply because one feels that the word "motor" has been misused is an overreaction. I'll argue that it's not an abuse of the word; the language is not weakened by it's use. Our ability to communicate precisely is not compromised. More specifically, I'll argue that a solenoid is a motor, and not just by some weakened definition, but by the most correct and precise definition.QuoteEveryone is free to explore dictionaries, online or printed, for the accepted definitions of both "motor" and "nuclear reactor."Okay, I'll do the leg work. Fromhttps://www.merriam-webster.com/dictionary/motorCode:Definition of motor(Entry 1 of 3)1 : one that imparts motion specifically : prime mover2 : any of various power units that develop energy or impart motion: such asa : a small compact engineb : internal combustion engine especially : a gasoline enginec : a rotating machine that transforms electrical energy into mechanical energy3 : motor vehicle especially : automobileAre you really of the opinion that entries 1 and 2 do not describe a solenoid?And for comparison, fromhttps://www.merriam-webster.com/dictionary/nuclear%20reactorCode:Definition of nuclear reactorphysics: a large device that produces nuclear energy

author: electromateria
author_rank: Regular Contributor
timestamp: May 25, 2022, 05:47:40 pm
content: The question remains - can a linear electric motor be designed to create a high amount of force while moving quickly?I'll be more specific: A 12" shaft with 5 full reciprocations per second with a load of 25lbs. Possible, or no?

author: james_s
author_rank: Super Contributor
timestamp: May 25, 2022, 06:05:00 pm
content: Quote from: Benta on May 25, 2022, 04:28:34 pmI'm not making up words. "Motor" is a word that has always had a broad range of meanings, it can be an internal combustion engine, it can be an electric motor of the conventional rotary type, it can be virtually anything that converts potential energy into mechanical energy, whether by rotation or linear motion. I would argue that a solenoid is a specific type of motor, that all solenoids are motors, but not all motors are solenoids. A solenoid is a device that converts electrical current into mechanical motion, it is therefor by definition a motor.

author: eugene
author_rank: Frequent Contributor
timestamp: May 25, 2022, 06:06:41 pm
content: Quote from: electromateria on May 25, 2022, 05:47:40 pmMost of the technologies that I know of that produce linear motion can be scaled up almost without limit. So, the answer is yes, it's possible.I don't know if a solenoid is the right choice, but it or something similar could almost certainly be made that meets your requirements.

author: CaptDon
author_rank: Super Contributor
timestamp: May 26, 2022, 04:53:14 pm
content: Railroaders have often used the term 'Motor' as the term for a diesel electric locomotive. A dispatcher may say to the hostler "I need two motors elephant style facing east for a 16:00 departure". We have surmised this use of the term motor to have originated in the trolley days of the 'electrified' motor car trolley and motor kind of rolled over into the pure electric (GG1) or diesel electric (SD40) days. Modern U.S. english does have a lot of ambiguity to it. Also, all other languages seem somewhat awkward or backwards to english, but those other languages seem correct to each other and literal word substitution works well during translation from one to the other. English is the standout as the weird one off.

author: TimFox
author_rank: Super Contributor
timestamp: May 26, 2022, 06:09:48 pm
content: In older days, the term "motor" was used for an electric unit (e.g., Pennsylvania RR GG1) to distinguish it from a "locomotive", which contained its prime mover (Diesel or steam), as in the literal meaning of the word.In applied physics, a Diesel or a reciprocating steam cylinder unit is called an "engine", as in "heat engine".A 4-6-2 "Pacific" steam locomotive has two engines, operating in phase quadrature, on opposite sides of the boiler.

author: eugene
author_rank: Frequent Contributor
timestamp: May 26, 2022, 06:28:42 pm
content: This talk of trains is interesting. Please don't stop on my account. But...I see "motor" as a very general term that means different things in different contexts. In the most general sense, a motor is anything that causes motion.I sat involuntarily listening to someone rant that they couldn't use the word "partner" anymore. I finally explained that the word has not changed. It's just that it has a new (and legitimate) context that might be more popular than whatever context they happen to be familiar with. We can still talk about lab partners and business partners, or any other kind of partner we want. If the meaning isn't apparent from the context, then we need to add qualifiers. No big whoop.

author: TimFox
author_rank: Super Contributor
timestamp: May 26, 2022, 06:40:21 pm
content: I agree that a "motor" produces motion.There are specific types and applications of motors that have specific names, such as "actuators" for motors that operate between two positions.

author: CaptDon
author_rank: Super Contributor
timestamp: May 26, 2022, 07:36:20 pm
content: Another really cool 'motor' I have seen was used to make the flippers move on one particular type of pinball machine, sadly I forgot which one although from around the late 70's. It was an electromagnet about 1.5" in diameter with a shaft going through it. The shaft has a spiral groove which caused the shaft to have a rotary motion against a fixed pin protruding into the groove. The end of the shaft above the playfield had the flipper on it and the end of the shaft sticking below the 'motor' had a somewhat thick round disk on it that would be attracted to the electromagnet causing the flipper to move. In the schematic the device was actually called out as a flipper motor. At the end of the day, they really didn't work very well and didn't have a lot of power. A conventional solenoid flipper retrofit kit was soon released and those whacko rotary solenoid flipper motors went directly to the trash bin. I suppose an unmodified pinball machine would actually be a rare collectable these days??

author: TimFox
author_rank: Super Contributor
timestamp: May 26, 2022, 07:42:46 pm
content: In commercially-available solenoid activators, there are both linear and rotary types for different applications.A useful general description of solenoids:https://www.kendrion.com/fileadmin/user_upload/Downloads/Datasheets_Operating_instructions/Electromagnets_Actuators/Electromagnets-Actuators-Technical-explanations-EN.pdf