Magneto Magnet strength ?

[cmfalco]

As I said the "earlier" model has removable magnets

Ah, when you wrote "earlier" I didn't realize you meant pre-historic...

[nevhunter]

They are the combined Mag and dyno case called Monobloc and about the 19 26 to 1931 years.

[admin]

So has anyone actually had any remagnetising done?
From references that I can find, the advice is to try Tony Cooper, or Paul Lydford at APL (Shaftesbury).
However, the link given by Will Curry earlier seems to point to someone who definitely still does this, and to 'modern' magnetos.
Here's the link again:
https://www.themagnetoguys.co.uk/remagnetising-magnetos

SG

[SEDoan]

For older magnetos with exposed magnets I've used a guy that is a member of the local antique farm tractor club and his recharger worked well. Farm tractor and antique engine clubs are a good place to ask for a remagnetizer but they may not have one that is powerful enough for AlNiCo magnets cast into aluminum.

Later I brought the same guy a Magdyno in which I'd replaced the capacitor and he didn't correctly locate the magnet in the casting (it would have helped if I'd brought along an empty magneto housing) and he didn't have the curved block that fits in the dyno saddle. The results were disappointing in that the bike was harder to start and more picky about mixture than before the capacitor had failed. I later learned that his remagnetizer has less than 1/2 the amp turns Lucas recommends.

Eventually I built my own magneto charger using plans from an electrical engineer and magneto rebuilder in New Zealand. It is different than the Lucas electromagnet type in that it uses smaller coils and builds up a larger charge in large capacitors. It can be built for about $200-300 using time expired capacitors and an old transformer for the electromagnet. It will reverse the magnetic field of a MO1 housing with the capacitors about 1/2 charged so the magnet is probably reaching saturation with a full charge. There is certainly more resistance to rotation from the magnet and the bike certainly starts and runs better.

I'm not an electrician, I don't have any test equipment other than a good multi-meter and I don't have a Lucas type charger so I can't say that this capacitor discharge type of remagnetizer is equivalent to the Lucas. However, I'm willing to share how I built it if anyone is interested.

[Mharrisbarton]

are the North and south shaped blocks made of a particular special material such as swedish iron? matt Barton.

[Roger Gwynn]

Shawn - I would love to hear how you built your charger.

[cmfalco]

Shawn - I would love to hear how you built your charger.

I'm not Shawn, but I'll tell you how I built mine. Rather than repeating the material here, I think you will find I've answered most of the questions you might have about appropriate electromagnets at:

https://www.britbike.com/forums/ubbthre ... Post460999

However, I didn't show details of my electromagnet, which are on the following:

A few points I didn't mention in the above Britbike thread are that all magnetic materials "saturate" at some point, beyond which they no longer help with the magnetic field. Because of this, you must use something like 'Armco® Pure Iron' or the electromagnet won't reach a field strength high enough to fully magnetize a magneto with an Alnico magnet.

Another point is the high current heats the wire enough that, if my electromagnet were to be in continuous use, it would need to be water cooled. However, a note on the above figure shows the mass of iron keeps the wire from heating more than a few ℉ in the less than 15 sec. it takes to magnetize a magneto. Since I've never magnetized two magnetos on the same day, there is plenty of time for the electromagnet to cool those few ℉ between sessions.

Expanding on something in my Britbike thread, this electromagnet has a very large inductance, and the energy stored in an inductor is ½LI[sup]2[/sup]. Because of this, opening a switch at full power would result in a huge dump of energy into an arc across the contacts of that switch. This should be kept in mind if using something other than a Variac to operate an electromagnet.

[SEDoan]

Dr. Falco, thank you for posting details of your magneto charger. I started to build one like yours even buying a very heavy transformer for the soft iron. After learning about the capacitor discharge type I decided to go with it because it seemed to be cheaper and easier to build. For anyone interested, a cheap source of soft iron are old damaged transformers. I bought a 200lbs transformer for about $100. The difficulty is that the iron core is laminated and easily delaminates when cut. This would mean I would have to wind the coils by hand.

Roger, I will write more on how I built the capacitor charger soon. Unfortunately I lost my first installment when the forum logged me out - spent too much time composing...

[SEDoan]

are the North and south shaped blocks made of a particular special material such as swedish iron? matt Barton.

Mine are mild steel which the Lucas document says is OK. I believe Falco's are soft iron.

[nevhunter]

Note IF you have a pacemaker don't go near any of this. Nev