Ignitions

[passenger0_0]

I've run a Joe Hunt (rare earth magnet) on my racing outfit for a few seasons and was very pleased with it. My 'rebuilt' Lucas racing magneto stripped its splines and reset the timing at full engine speed which buggered the engine (twisted crank, seized pistons, all the usual). Never again will use the original brass/steel combination. I made up a batch of 20 one piece stainless shafts which were very successful that I advertised in MPH at cost price. Not much interest so that project died. I only use the Lucus mag on my original road bike now.
Regarding Joe Hunt mags I have found there were (are?) three simple issues:
1). The capacitor was of too small a capacity for the high output so I used an external capacitor.
2). The points cam was a few degrees out and needed hand finishing.
3). It needed a propper oil seal fitted.
I believe Joe Hunt has changed hands since I got my mag and these issues have been dealt with. My advice is that if you don't mind the additional bulk, Joe Hunt is a good alternative at a very competitive price.

 

[greg brillus]

Hi there, and thanks for the info so far. I think short of going to electronic/coil ignition and carrying a battery on board to power it (total loss system) then in the true sense of a magneto for racing you either go with a modern BT-H in either single or duel plug set ups or go with a Hunt type, I do know of a racer here in Australia who is running an original scintilla mag, the same as was used on the " Picador" this on a 1200 cc twin on methanol...a chopped engine in a road racing outfit, I even remember the engine number off it.....anyway I'm pretty sure that the SR 1 and Hunt type mags are made along the same basic design as the Scintilla. Having worked on many makes and types of magneto's, I can confirm that a Scintilla is by far the best made mag you will get, but saddly they are rare and this makes it not a practical choice if not for the lack of parts and so on. I like very much the idea of using the Hunt type....one quick question for you all, but not many may know the true answer....Did the armatures fitted to the KV-F TT mags have windings made of plated "Silver" wire..?? This will have you scratching your heads Only difference I've seen with the TT is the one piece stainless drive shaft/ end housing, end cap using the manual advance set up (similar to the Constellation mags) and platinum points assembly and also the pickups held by screws and not clips as on the lesser version, it may also be possible that they had a slightly bigger magnet in the housing....on the test rig, the TT gives a very accurate spark timing, and the platinum points make a big difference here, clearly giving a much cleaner break with no after burning seen at the points. The split in timing from one cylinder to the other is also very accurate, when checked on the rig, you can see the sparks firing with number one set at zero and number two dead on at 205 degrees later, this the angle between the two cylinders of a 50 degree twin....impressive to watch running......Greg.

 

[bmetcalf]

Gene Aucott tried to put together a group order of Scintillas back in the '80's, but I believe didn't get enough interest.

 

[Magnetoman]

Rather than individually reply to various posts, below I've cut/pasted things that caught my eye. Also, sorry in advance for formatting problems. This is my third attempt to fix them in 'Edit Post', but the editor keeps randomly removing spaces between some words.

I think all a Joe Hunt mag would need is a modified cam to change the timing for say a Triumphs 180 deg to a Vincents 205 deg...

The magnet for a V-twin is different as well as the cam. The magnet(s) is in two pieces cast asymmetrically in the aluminium matrix to give the proper timing.

He had quite a few unhappy phone calls with both Ken Belland Perry Gearhart. Neither would warranty their work for a racer. After four or five failures, it was too costly to race these items, mostly in time and races missed. This is one of those issues where success depends as much on the people supporting you as it does on the rider.

Sorry to speak ill of someone no longer with us, but my experience having Ken Bell restore magnetos for my Gold Star and Black Shadow~15 years ago is responsible for me deciding I had no choice but to repair them myself. I am not surprised at all that his magnetos failed on the racetrack, since they failed me in only ~50 miles of use on the street. Anyway, you can see what I learned as a result at:

http://www.britbike.com/forums/ubbth...733#Post446733

As far as I can tell, this is the most extensive description of the repair of a magneto you will find.

My 'rebuilt' Lucas racing magneto stripped its splines and reset the timing at full engine speed which buggered the engine (twisted crank, seized pistons, all the usual). Never again will use the original brass/steel combination

Somewhere I have an article from the late '40s or early '50swhere in an interview with a Lucas technical person he said, without actually condemning their rotating armature magnetos, that the reason they developed theSR1 because of the mechanical problems with the armature at the ever increasing rpms on the race track.

1). The capacitor was of too small a capacity for the high output so I used an external capacitor.

The capacitance needed is determined by the inductance of the coil, not the output.

Did the armatures fitted to the KV-F TT mags have windings made of plated "Silver" wire..??

Can you say more about this? I've never heard that anything other than copper was used, and don't understand why it would be, since copper has the lowest resistivity.

the platinum points make a big difference here, clearly giving a much cleaner break with no after burning seen at the points.

As far as I can determine, platinum points were introduced in the early days (i.e. pre-WWI) because it was thought it had lower surface resistance than tungsten, which oxidises more readily. However, in practice this is not an issue a tall, so I suspect Pt was kept in use basically out of superstition. Certainly, my measurements have not shown any advantage at all for Pt, and it does come at the disadvantage of eroding quite quickly in the presence of oil or gas vapour (not that any of our bikes leak oil, or that Lucas seals aren't up to the task…). I address this in more detail, including a technical reference, in the link given above.
​

 

[van drenth]

Herewith one picture regarding the Pazon dual plug smart fire ignition and all is fitted under de cowl and detachable for olifilter change. Fitted now two years ago and working perfect.
Van Drenth JC

 

[Big Sid]

Sid here . My newly enstalled tapered armature end is as described earlier , onepiece . And all old Lucas Magneto condensers are to be considered worthless . Even NOS examples still in the box . Make sure your rebuilder replaces it with a modern item , and even then it must be the correct type for best function and long life . Our electrical wizard is Doug Wood . Sid .

 

[Magnetoman]

Make sure your rebuilder replaces it with a modern item

I would encourage anyone interested in magnetos to read the detailed thread whose link I posted above. Nothing in it is a repeat of second hand "knowledge," much of which is wrong, but instead comes directly from my own research and measurements. As I show in that thread the instrumentation I've assembled over the past 15 years since my bad experience with a professional restorer has given me facilities well beyond those I believe any restorer has. Much misinformation about magnetos is circulated as "common knowledge," but I've laid everything out in that thread, so people judge for themselves whether what I've written about them is correct. Amongst other things in that thread, I provide the part number of a modern replacement capacitor that survived the equivalent of 150k miles of my stress tests.

 

[Big Sid]

Sid here . Still on magnetos . I always drill carefully a small hole in my contact breaker cap , also on the D Dist. Cap to let out the ozone gas that builds up where ever contacts on occasion flash a tiny spark in a closed compartment .

 

[Big Sid]

More . If your condenser is failing , this can be seen by increased flashing at the contacts while running , you can boost its performance by running an outside second condenser , a auto type , if you have a kill button type end cover . Ck that the inner carbon button is nicely bearing on the center domed nut . Attach the additional condenser s wire to that caps outer terminal and ground its can to a nearby case through spindle nut . The flashing over at the contacts should lessen , running improve . Done it . Sid .

 

[Magnetoman]

More . If your condenser is failing , this can be seen by increased flashing at the contacts while running , you can boost its performance by running an outside second condenser , a auto type , if you have a kill button type end cover ... Done it . Sid .

This is a "fix" that is sometimes mentioned, and I know you said you've done it, but it doesn't work for quite fundamental electrical reasons. A failing condenser is analogous to a leaky dam, and attaching a good capacitor in parallel to a bad one is analogous to trying to fix the leak by building a solid dam at the top of the hill overlooking the creek -- it doesn't matter how good that additional dam is, it can't stop the water leaking through the original dam.

It's not just that I can cite the fundamental reason this "fix" won't work. I've done a full set of experiments placing a good capacitor in parallel with Lucas condensers in various stages of failure, and the measurements confirm that it does not work. I've done this with an impedance bridge, to collect quantitative data, as well as with one of my magneto testers, where I can watch the increased sparking across the points.