I need a powerful solenoid, as much as I can get. I need a 3-4" stroke.

Here is what I've got (or will have soon):
* coil 4" long
* 1672 turns of 22 gauge wire (~15 ohms) in 11 layers
* 15v power supply, so 1A of coil current, or 1672 ampere-turns
* Armature is a 3" (.5" dia) neodymium magnet, exact strength unknown, but "strong".

I don't really know how to state my requirements other than to say the armature will be used to propel a .6oz weight half way across a room. For those of you with any experience in stuff like this, do you think this will do it?

Left something out: Coil is 1" diameter.

 

* Armature is a 3" (.5" dia) neodymium magnet, exact strength unknown, but "strong".

Why a permanent magnet for the 'armature'? This isn't the normal way a solenoid is made.

 

3" to 4" stroke in a solenoid is "off the scale" of normal, practical solenoid design.

Maybe members here can help you figure out a better idea?
What are you trying to move?

 

Just a gut feeling. Iron armature, @ about 5 A & 5 ms pulse. Maybe C discharge ?

 

Why a permanent magnet for the 'armature'? This isn't the normal way a solenoid is made.

Yes I know, but wouldn't you think that a strong magnet for an armature would produce more force than a ferrous armature? If you place one magnet close to another you get more pulling force than if you placed the one magnet close to a ferrous object. "Normal" solenoids probably aren't made this way because it's more expensive compared to just making a bigger coil.

The plan is to charge a 22,000uF cap to 9v then discharge it into the coil. If I have to I can go as high as 25v. I've already stated the objective - shooting a 1/2 oz weight 10-20 feet.

I appreciate your comments/suggestions. Hasn't anyone done something like this before?

 

... try rotating the trajectory so that it is vertical, or nearly so. Then try to measure the max height that is achieved. The height and weight can be plugged into the equation for potential energy, which is a measure of the system performance, a figure of merit. ... Use SI units for the most straight-forward ... correct result:
energy= m*g* h = kg * (9.8m/sec^2 ) * m = newton-meters .... units of energy

 

... try rotating the trajectory so that it is vertical, or nearly so. Then try to measure the max height that is achieved. The height and weight can be plugged into the equation for potential energy, which is a measure of the system performance, a figure of merit. ... Use SI units for the most straight-forward ... correct result:
energy= m*g* h = kg * (9.8m/sec^2 ) * m = newton-meters .... units of energy

Well, if I'm going to rotate the trajectory to 90 degrees and take measurements, I'll stop at 45 degrees and see if it goes 10 feet. No math required!

 

... The basic idea is to get a measure of the energy that is produced, and then measure the input energy that is required to cause that specific number ... simply V*I ... volts*amps. A ratio of these quantities would indicate the efficiency of the system ... possibly useful when building different designs or configurations. This may not seem important until the proportions are scaled up.

 

... cancel that ... thinking about something else ... be back later maybe.

 

25 V would be better. If pulse is too long solenoid will try to pull armature back in. 45 deg. about right
for best distance. " done this before ? ", Yes, Completed Project File - Solenoid.

 

It would seem that your design objective is to make a coil that converts the maximum amount of electrical energy into propelling the weight object to some specific distance. The coil receives energy from the capacitor, and can be estimated as:
\(E_C = 1/2 C V_C^2\) ... where \(V_C\) is the capacitor operating voltage.
What is not quite so clear is how much of the coil energy, received from the capacitor, is converted into projectile motion. Coil design efficiency could depend on the number of wire turns, the number of wire layers, the wire gage used, the center armature material, or other factors.
To develop the best coil design, you could take the vertical height of the projectile produced by a given design and compare it to that achieved by variations. The choice of using a vertical trajectory just makes a readily available numerical index for comparison purposes.

 

Yes I know, but wouldn't you think that a strong magnet for an armature would produce more force than a ferrous armature? If you place one magnet close to another you get more pulling force than if you placed the one magnet close to a ferrous object. "Normal" solenoids probably aren't made this way because it's more expensive compared to just making a bigger coil.

The plan is to charge a 22,000uF cap to 9v then discharge it into the coil. If I have to I can go as high as 25v. I've already stated the objective - shooting a 1/2 oz weight 10-20 feet.

I appreciate your comments/suggestions. Hasn't anyone done something like this before?

The PM should have a pole on each end, N on one and S on the other. How do you plan on switching poles on the electromagnet fast enough to keep it moving through the solenoid coil? Don't forget the solenoid is also an inductor. Permanent magnets don't work in solenoids because of the N and S poles, not because they are more expensive.

 

The PM should have a pole on each end, N on one and S on the other. How do you plan on switching poles on the electromagnet fast enough to keep it moving through the solenoid coil? Don't forget the solenoid is also an inductor. Permanent magnets don't work in solenoids because of the N and S poles, not because they are more expensive.

Wait a minute.... my PM has a pole on each end. So does my coil when energized. Say I position the PM so that north is up and my coil so that south is up, and at rest the PM is aligned so that its north is slightly above the coil's north. When energized the PM will be repelled from the coil in the upward direction and at the same time it will be attracted to the coil's upper end (its south). These forces will get stronger as the PM gets closer to the center of the coil where the N-S and S-N poles align. As it passes center it will decelerate rapidly and probably oscillate for a bit. No matter, the projectile will have been launched. It will have accelerated my projectile for almost 3" and I wouldn't have to switch poles on the coil. Can you elaborate on why you think I need to reverse coil polarity?

 

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