Car Audio Classifieds! banner
1 - 20 of 45 Posts

·
Premium Member
Joined
·
9,731 Posts
Discussion Starter · #1 ·
I thought I would write up a simple and clear tutorial as to how a subwoofer motor is build. This write up contains no softparts, simple the motor assembly. For softparts I will have a tutorial up in time.

A motor consists of a yoke (bottom plate), magnet/s, top plate, shorting rings can also be included if anyone gets curious and wants to try and build their own.

First off we have a jig to center the magnets. This jig is made with two 1/2" pieces the bottom plate has the OD of the pole piece while the top one has the OD of the slug/s.



Taking a magnet you place it in the jig, due to how magnets are cut sometimes the the ODs are not all the same although the slug will still be round. In this case we can simply shim the magnet so it is centered in the jig.





Now that a magnet is ready to be placed on the t-yoke we can take a t-yoke. Most steel for subwoofers have a coating on them so they do not oxidize. This coating needs to be scuffed so the glue can stick to a solid surface. Some motors will have paint, others use a nickel plating in this case we have nickel plating.



The steel and magnet will bond to one another via a loctite adhesive. I prefer to use Loctite 392 with Loctite 7387 as the primer. Of the two surfaces being connected it does not matter which gets the glue and which gets the primer. For this example I will show the magnet having the primer applied to it.


 
  • Like
Reactions: Pimpalero2003

·
Premium Member
Joined
·
9,731 Posts
Discussion Starter · #2 ·
From this point the yoke can be placed into the magnet allowing the plates to connect, and be placed in a press.




Repeat the steps to add more slugs on top of one another.




Now for the tricky part which has the least option of error. Shimming the top plate. I prefer to use a coil of the same size planned to be used on the motor. Place the coil in the top plate with top of the former down like pictured.



Check to make sure the coil can be pushed down nicely, while also not too loose. In most cases a single shim can be used for this.



Have the top plate scuffed as well and place a bead of glue in the center of it.



With primer on the magnets I prefer to use popscile sticks to hold the top plate above the magnets as I apply the outside shims.




Once shims are applied, remove popscicle sticks, and press coil down as you will notice the top plate center itself. Turn the motor upside down and press it for the last time.





As you can see the magnets still have some primer on them, a little acetone cleans them right up.



You now have a perfectly centered gap



Ready for magnetizer, then from there basket and softparts can be applied.

 

·
Registered
Joined
·
2,057 Posts
you want to build me a super motor
 

·
Ω rise is way too high..
Joined
·
3,784 Posts
I would love to see more of this on the site. Details of things we talk about and use every day, how motors are made and stuff. Thanks man! Enjoyed!
 

·
Registered
Joined
·
6,816 Posts
Bumpin does it all
 

·
Elite Member
Joined
·
4,981 Posts
Any ideas on how I could put a top plate back on that came off? Glue just didnt work good enough or something, I have the top plate off the motor and would like to glue it back on.
 

·
Registered
Joined
·
2,298 Posts
Do you hold the press sown until he glue is dry? Also when you flip the motor after the top plate is put on do you remove the shims and coil first? What makes it not shift when you flip it? Also how do you determine magnets that will be strong enough to make a good motor? How do you no what the OD of the magnets needs to be.
 

·
Premium Member
Joined
·
9,731 Posts
Discussion Starter · #20 ·
Any ideas on how I could put a top plate back on that came off? Glue just didnt work good enough or something, I have the top plate off the motor and would like to glue it back on.
I take off top plates and recenter them/retap them all the time. Not a terrible process but something you must be careful of. You will need three long bolts, a coil and shims. With the top plate shimmed in place slowly and evenly lower the top plate but dont forget to apply new glue and have the two surfaces cleaned up before all of this takes place.

This is awesome
I was wondering how the magnitizer worked?
I would suggest reading about Lenz's law but in a nutshell a magnet is charged, thus producing energy along electric field lines thus creating poles in a magnet.
Do you hold the press sown until he glue is dry? Also when you flip the motor after the top plate is put on do you remove the shims and coil first? What makes it not shift when you flip it? Also how do you determine magnets that will be strong enough to make a good motor? How do you no what the OD of the magnets needs to be.
The glue drys in under a minute, many times in a few seconds. So yes I keep pressure on it while it is drying.

I leave the shims and coil in while the top plate is pressed on as well.

The easiest way to determine magnet size accuratly is by using a FEA modeling program (finite elemental analysis) which will use the properties of the steel and magnets used to determine when the steel is fully saturated and at what point an excess of stray flux occurs.

The OD of the magnets have some importance when looking at flux current but very little. Most people dont realize the gap is where the "magic" happens. This is the steel has saturated the magnetizm. A much larger importance should be put on the gap size, both on the OD of the pole and ID of the top plate.
 
  • Like
Reactions: bigdhenderson
1 - 20 of 45 Posts
Top