Recharge the magnet on a Presto 1D head,solve your problems.

[electronrancher]

Wow, I was doubtful but after reading up - yes, it seems that a whack or two in a weak magnetic field can help magnetize ferrous materials. Amazing!

Personally, I think Bryan did it right: Place it with a field so high that the weaker magnetic material is saturated. Done and done, no whacking needed.

So - does anyone happen to know what material the presto magnet is made of? I'm still interested, just for science's sake.

[Presto Repairs]

Bryan was able to do his on the cheap by using magnets he had available, it is true, you can charge magnets using neo's aswell, but it also wouldnt have hurt to give the magnet a little tap too...

Saturating yes for sure, but able to hold charge for several years ???????

You can use neos to reverse the poles on alnico magnets and it is also known that they have the potential to drain your magnet if not done correctly

heres another you tube video demonstrating...

https://youtu.be/Srq0ITGJKwk

Old ferrite humbucker pickups can also be re charged by passing them through a magnetic field, but it is also common for them to not hold the charge for very long only having to repeat the process periodically...

I use a charger because I charge magnets for others, if you are only intent on charging your own magnet you will get away with using neos...

[45rpmdude]

Neyodimimiummm Colbolt Steel.. cause i cracked mine in half with a hammer.. but my hammer was steel... not brass..

[studiorp]

And about the time of recharge ? Minutes or hours ?

[recordboy]

Great thread!
I read it last year about this time & now found it again as I think I am in need to do something like this.

cheers

[opcode66]

I've started doing mono cutterhead repairs. There is a lot that can be done to improve performance on mono heads. Neodymiums are one tweak, but certainly not the extent what can be done to boost response.

Please have a look at my thread:

http://lathetrolls.com/viewtopic.php?f=6&t=6380

Or my new site:

http://cutterhead.repair

I can change out to neodymiums or recharge existing horseshoe magnets. Recoil and more!

[grooveguy]

I'm intrigued by what Fela has done, replacing the horseshoe magnet in his Presto head with the stack of neodymiums. One question for those of you with background in the physics of magnetics: Does stacking magnets, as Fela has done, increase the flux in the armature gap, or would the flux be the same with just one magnet and soft iron to take up the extra space? I'm try to picture an analogy here and have two scenarios.

1) If you put batteries in series, you don't get any more current from the stack than any one cell can deliver. Is current in this case like magnetic flux?
2) With a tug-of-war team, you have a group of guys, each pulling on the rope with their feet on the ground... in parallel, as it were. But if you had each grab the ankles of the guy in front of him, you'd essentially have just one guy pulling and the rest simply transferring the 'current' or 'flux' to the rope.

I consider magnetics a 'dark art,' with not much taught in school, and a lot of misconceptions and BS, as evidenced by the plethora of perpetual-motion machines you see on YouTube, using magnets as an endless supply of energy. I'd like to understand this better.

[opcode66]

.

[opcode66]

Fyi, putting batteries in series increases the total voltage. Current is governed by the load value (and also the potential difference). The same battery can supply different current values depending on what resistance is attached.

Best not to think of magnetism strictly from the perspective of electricity.

[grooveguy]

So, perhaps we can consider the gap between the pole pieces (where the coil or iron armature sits) as 'resistance.' In that case, more power can be applied to the 'resistive' gap, either by increasing the voltage, or the current, or both. And perhaps magnets 'in series' do generate more 'voltage,' and even if their 'current' capacity does not increase, the flux in the gap becomes greater.

I think you are very right in stating that we must not think of magnetism in electrical analogies. Sadly, I'm an analog kind of guy. Thanks, opcode66!

[Fela Borbone]

Search  "magnetism and magnetic materials" J.M.D. Coey . Theres a free pdf download...

[Fela Borbone]

Read from pag 466 of this book... as is an steady field no complicated maths are required....
 But in the cutterhead an steady and changing fields are sharing the gap... this  creates need for "magnetic headroom" to avoid saturation distorton...how much of each? Trade off!!!

[studiorp]

Hmm, so this point I have a question : is there a standard meausure of air gap in a cutting head ?

[Fela Borbone]

Around 0.2 .mm or so. Small gaps have no big different density flux zones and smaller reluctance. But it has to allow amature deflection

[studiorp]

Is there a relationship among distortion that came created inside the head and the air gap ?

[Fela Borbone]

Well... everything is related somehow... bigger gap reduces sensitivity and theres a limit for crancking up current in the coil before it saturates the system and distorts.(in moving iron, I mean, for moving coil limit  is coil overheating)