I want to build a solenoid.. (partly for several intended applications and also because I just want to learn how they work!) I know essentially how they operate, but not enough of the details to go to the hardware store & radio shack, get parts and build a working model..

Can anyone explain in detail, how a solenoid works, and how I might build one from commonly available components? thanks!

what are you going to do with it?

It's nothing special. coil of wire with an open center. when you apply power, referably DC for experimental ones, it builds up a field and pulls in anything magnetic. (AC will make experimental solinoids buzz like hell.)

if it's just a demo thing. wind it on some plastic tubing or pipe and use a smooth section of bolt for a core. If you make it big enough it will suck in cannon balls or about any other iron object that will fit.

choice of wire depends on how many turns you want to use and how much juice you want to feed it. any wire will work. "magnet" wire just lets you get more turns in a smaller space because of the thin insulation on it. More turns of wire means a stronger magnet that needs less power. a few hundred turns #26-30 magnet wire will make a solinoid that should be fairly strong and run off a "D" cell or 2. Add more turns and you add more resistantce so you'll likely need a little more current.

if you are actually building it for an application then consider buying a ready made one. the machine work to make a reliable one is significant.

I agree... try some off-the-shelf ones. I've got 6 different ones sitting on the desk next to me. They came from McMaster-Carr Industrial supply, 404-346-7000. They're kinda stingy with their catalogs, so you might try MSC Ind. Supp., 800-645-7270. You won't be able to get MSC to stop sending you catalogs.

Ogre- I've been toying with the idea of using a solenoid to do the job of the miserable hydraulic clutch on my car. Do they make solenoids that come in or out of the housing partway or slowly depending on how much juice you apply? Do they make them strong enough to move the clutch on our cars?

That's one of my intended applications right there!! Hit a switch on the shift knob, and a big solenoid engages the clutch.. then you shift normally, and release the button which disengages the clutch.

One other question, by reversing the current will the rod be pushed out of the core? With your comment about the AC making the solenoid buzz, I assume that means alternating the polarity makes the rod bounce in and out of the core rapidly.. is this correct?

Darklord- I just spoke with an engineer at MSC regarding solenoids. I explained to him what I wanted. Here's the scoop.
1. Solenoid when powered up is all the way in or all the way out, that's not too bad, as the application would still work.
2. He knows of no solenoids that have the power to shove a clutch like on the FIero in. So looks like that idea is shot down. Unless someone knows differently.

So it would require hydraulics.. not the perfect solution, but it could work.. it'd be expensive though. How much force is required to engage the Fiero clutch?

Another intended application is robotics, I'm planning to build a simple robotic arm this summer, just as something to do.. and as practice for college.. (I'm in the electro-mechanical engineering program at Humber College in Toronto, it's a robotics course..)

Hmm. I think I have my terms backwards here.

I guess when you push down on the clutch pedal, it's actually disengaging the clutch, right?

oh well, I hope people knew what I meant anyway.

Hey Richard,
Would an electric linear actuator work?? They use them in the car stereo world to lift and lower amp racks and speaker enclosures of all types. They have to be pretty strong because I've seen them lift some pretty heavy stuff. The only hitch might be that linear actuators are too slow acting to be used on a clutch.
As for solenoids, even if you could find one big enough to engage and disengage the clutch, there would be one major problem. Solenoids are built to be in either the open or closed position and nowhere in between. This would be fine for disengaging the clutch but wouldn't be very pleasent when engaging the clutch.

How does a linear actuator work?

I assumed it was basically the same as a solenoid, but operated in steps so it was more precise, and could be held in any position, move with variable speeds, etc.

I think someone mentioned this, that you might have to do it with hydraulics.

On my tbird turbo, it has all these cool electronic things in it, auto suspen etc... it also has anti lock brakes for an 87. The brakes have a electric motor for power assist for the brakes and also a vacuum. This is an idea that you can use the same motor to pressurize the fluid to move it in and out with a switch and get someone to build a small circuit to control the rate that the motor creates pressure.

what is the website address for MSC? And what other products do they sell?

DARKLORD,
From what I know, linear actuators work like this: they look just like a hydralic cylinder but instead of using oil to push the shaft in and out they use a "screw type" mechanism. The bottom of the actuator has a long flexible cable on the end and a small electric motor on the end of the cable. The electric motor turns the cable which turns the screw mechanism inside the actuator. So they don't operate like a solenoid at all.
Linear actuators were quite rare years ago and car stereo competitors use to adapt them from many sources. Now there are company's that specialize in them and can make them in any size and strength.

Hmm.. well that won't do at all!

too slow..

in the late 80's Audi used an electric clutch in their rally Sport Quatro's. John Buffam (? sp) was the driver.

A linear motor/actuator works the same way a stepper motor does, and is driven with close to the same circuitry. (You have to add a limiter of some sort or you can shoot it right off the tracks and/or break things.)

they are also used for tall lift elevators where traditional cables and hydraulics are impracticle.

With the power line and stepper motors can generate I expect is whould be posible to use either to run a clutch. A big stepper driving a gear segment on the clutch shaft could probably handle it and would be very simple mechanically.

you'd want to set it up so that you drive the motor enough steps to put the clutch out, then let it roll back on it's own. This would preserve the self adjusting nature of hydraulics.

You might have to use a friction brake to regulate release speed. The stepper can be used for braking but it would be tricky to calibrate. If you don't control release speed some how the clutch will slam. Part of this depends on how much rotational resistance the stepper motor has to begin with.

you also want to make the gear teeth pretty big and loose so it doesn't jam on every tiny spec of dirt.

There are a number of other ways this could be done. This one just comes to mind as fairly simple mechanically.

I'd definalty not do this with a solinoid, especially a home made one. Solinoids are either on or off. not allot of ways to control pulling or release rates that would take Fiero engine comparment heat.

AC can make both the core and the coil windings vibrate. The core is mainly annoying. the windings on the other hand will wear off the insulation in short order unless the whole coil has been laquered into a single brick to keep the wires from rubbing as they vibrate.

I read a few years ago about a Porsche system that when you put pressure on the shift handle, it would release the clutch. Like putting the car into first gear and pushing the handle a little farther. The clutch is released just like letting off the clutch pedal, except the shifter handle does it. I never saw how it was done, but it was pretty cool.

This was actually used in some production VW beetles. I forget what years. I saw it once or twice. I didn't like it. Very touchy to use. dificult to keep adjusted right as well.

As if my hydraulic system for my clutch isn't about the most tempermental piece of equipment I've worked on. My next idea is hooking a strong spring to the throwout lever to "aid" the slave in pushing the clutch.

Part of the fun of driving a manual transmission is the control one has when engaging and disengaging the clutch. It is not just simply an ON or OFF operation. It is dependent on any number of variables which can change by the second or by the year - engine horsepower, engine RPM, engine operating temperature, transmission gearing, tire size, tire pressure, road grade, net vehicle weight, etc.

Learning to master the use of a clutch and manual transmission is a large part of the joy of driving. I, for one, would not want some electronic device taking the place of a regular clutch and how it "feels" to my left foot.

Ogre- As much as I work on VW's and I forgot all about the stick shift automatic Beetle. Funny thing about them was everyone that I painted had a cracked windshield. People would get in one to test drive, put the car in first and drive away. They would wind up the engine and stab the clutch to shift gears. The problem was there was no clutch pedal! They slammed the brakes on and hit the windshield with their head. Kind of funny, unless it happens to you.