mag. renovation

[John Appleton]

Why would race mags run faster ? Don't all mags on a 4 stroke engine run at half engine speed ? /quote]

No, it is common to have mags run at engine speed and using the wasted spark principle via a second plug on large capacity engines of the type fitted to wartime tanks and aircraft. These engines mostly had twin mag installations, both of which had to be tested before takeoff or in the daily check in the case of tanks. This was necessary as even these high quality instruments were prone to suffering from the same problems as Mr. Lucas's efforts.
The reason for running at engine speed was to keep mag revs high enough to maintain a reasonable spark, and to assist starting at the low cranking speeds of these large capacity engines. Even this was not sufficient to gurantee ease of starting and trembler booster coils were installed on british tanks with Merlin derived power units and american tanks fitted with the Wright Whirlwind engine.The Bosch mags on german vehicles had a clockwork impulse starter, incorporated in the mag drive, which served the dual function of increasing the mag speed at the firing point and retarding the spark at the same time.
Sorry to go on at such length, but at least you now know why our bikes wont start, missfire at all the wrong times and why the series D consigned mags to the museums. No , I dont like mags!

 

[Tnecniv Edipar]

Yeah , good point. High tension output is going to be an issue at the lower engine speeds on those big motors. The Russians had obviously sussed the problems with petrol engines in Tanks and used Diesels instead !!

 

[Tnecniv Edipar]

Most aircraft mag's are rotating magnet, rather than bike mag's rotating coils.

Neil

Both types have been used on motorcycles.

 

[Tnecniv Edipar]

No , I dont like mags!

Mags should be more reliable now with epoxy embedded windings and modern capacitors.
IMHO Mags have a fascination that I find more appealing than the Kettering system.

 

[Tom Gaynor]

More magnetos

2MTT is rotating magnet. There may be others, but I've never seen one. I suspect that "TT" mags are ordinary mags that have been lab tested to eliminate the weak ones. I was once told that ALL Lucas mags underwent a 12 hour test before being released, but have no idea whether or not this is true. The Scintilla sounds like the system my Norwegian buddy ran on his (180 kph...) Rudge. He used a Bosch low-tension generator which looked just like a BT-H mag, with a coil under the tank. My Manx has a modern equivalent, a PVL generator where the mag sits, and a mini-coil up under the tank. The advantage is that it has a few degrees od retard to make starting easier.

Most aircraft mag's are rotating magnet, rather than bike mag's rotating coils. Also most (other than microlights) aircraft ignition system tend towards dual mag systems, to allow for backup in the event of failure.

From memory the scintilla system was an LT generator with either a built in, or external HT coil, which allowed for primary voltages to be as high as 400 Vdc.

Neil

 

[bmetcalf]

Lucas SR-1's with rotating magnet were fitted to '55 Matchless G80s and other bikes. There was also an SR-2 for twins. Both Platform type.