The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Lucas, Ignition, Charging, Electrical => Topic started by: Steveba10 on 27.09. 2020 11:11
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Hi, I have a question regarding the surface my contact breaker earth carbon brush appears to run on
Please see the photo below to see the interior of my cam ring holder/points housing and the carbon brush protruding from the back face of the contact breaker.
The surface is rough, I assume from casting with no indication of the carbon brush having run on it.
I’ve searched for illustrations to see if there should be a flat smooth disc insert attached there to no avail.
With the surface as it is the carbon brush would soon wear away.
So my question is have I something missing in the housing or do I have to machine the surface smooth before use?
I’m restoring a ‘57 plunger that was put in a leaky shed back in 1977 and left there until six weeks ago, a complete basket case.
The owner in his wisdom took everything apart, and I mean everything, even down to the K2F mag.
I’ve collected the bits of the mag together and cleaned them up.
It’s all a bit corroded, but complete, I’ll just need need new bearings before making the modifications I propose.
I have little confidence that my mag’s magnets have retained sufficient flux having spent to long disassembled with no keeper.
The capacitor is also likely to be poor so even if I could get the mag to work it is unlikely to be 100%.
So I’m looking to convert to electronic ignition without the expense and by using components I have lying around.
I propose to use the points to activate an electronic ignition unit called ‘SparkRight.’ I have two of these I used on cars back in the 80’s.
Both are still good, and one can be hidden in the plunger’s toolbox. All I’ll need to purchase is a double ended coil and ht leads.
I have a DVR2 regulator to convert to 12v to power the unit.
I’ll use the contact from the mag cut-out to the SparkRight unit as the trigger. But I do need a good earth contact on the other side of the points.
Hence my question regarding the housing surface.
I’ll also have to disconnect the low tension lead in the armature to disable the parallel path through the lt coil.
I think this is easily achievable unless I’ve missed something?
Any thoughts?
Thanks for reading.
Steve.
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The end housings are also found with a machined surface.
Nothing missing.
I suspect that those with a machined surface were originally to go with the brass points assembly with earthing brush like yours and those with the as cast finish to go with the later steel points assemblies which do not have an earthing brush.
Over the years the parts get mixed up. The earthing brush spring only provides light contact and the brass points are often found less the earthing brush.
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Thank you Julian,
Good to know nothing missing.
I’ve faced mine off on the lathe so should be good now.
Thanks again,
Steve.
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They work just as well without the brush.
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Seems like a lot of trouble to avoid using the mag, or even trying to get it working. Magnet strength can be easily tested. It involves a compass and compass points layout on the floor. I'll try to find the instructions and post later. Getting re-magnetized requires making friends with a local individual or business who/that owns a magnetizer. The condenser is easily addressed with a Brightspark EasyCap. Bearings and contact points still need sorting in your electronic approach, not to mention needing a totally reliable dynamo and belt drive in order to get home. (I assume you're intending a belt drive to go with the DVR and 12V operation.) Did I mention, belts break.
While this might not matter to you, I always appreciate the vintage aura inside my head when my bike is running well on its magneto.
Richard L.
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Hi Richard,
Thank you for your reply.
I’ll be interested in the flux density measurement you describe if you can find it.
I didn’t realise there was an option to re-magnetise a magneto.
I’ve made my own de-magnetiser for cleaning up audio signal equipment pre-digital era and have never given a thought to doing it the other way round until now, so thank you.
Capacitors, points and bearing present no problem, belt conversion is also easily achievable.
I think I’m swayed by starting problems experienced years ago, no start then flooding and bump starting being the order of the day.
Poor maintenance usually being the cause. The event of transistorised ignition improved starting (cars) and hall sensors taking the place of points eliminated the maintenance needed there.
I take your point of running a bike as original with its mag.
After all Magnétos are used in light aircraft for safety reasons in favour of the Kettering system albeit doubled up.
Thanks again and I’ll look out for your magnetic strength testing.
Steve.
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After all Magnétos are used in light aircraft for safety reasons in favour of the Kettering system albeit doubled up.
They better not use Lucas motorcycle magnetos in aircraft!
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Hi All,
Some years ago A friend was "going on" and said to me that he believed Lucas mags were as good as BTH or Bosch
I replied he had better go and look at Duxford air Museum (he lived local to it) and find an aero engine fitted with a Lucas *smile* *smile*
John (who has a BTH on his SR not a B.T.H *ex*)
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I searched for re-magnetising a magneto and came across this interesting DIY 2-part article.
http://www.gasenginemagazine.com/equipment/make-your-own-magnet-charger.aspx
Steve.
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I’ll be interested in the flux density measurement you describe if you can find it.
I don't know the flux density, nor own a guassmeter to check it. Not sure you could identify a gap into which the meter's probe could be inserted. My own experience spawns from having worked in the loudspeaker manufacturing industry. You can find the magnet strength testing information in the following thread. https://www.a7a10.net/forum/index.php?topic=5292.0. There are also some pictures of various magntizers I was able to choose from at the friendly local magnet ditributor. Go to KenF's first post for the specifics of the test. You'll also want to check out Groily's post with the link to Lucas' decription of the various magnoto magnet systems and how to remagnetize.
Richard L.
Edit: In retrospect, I suppose the "gap" would just be the axial centerline of the mag where the armature lives.
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Steve,
I just re-read most of the magnetizing thread and you CAN get some info about flux density from KenF's (RIP, a great loss) 27 Feb 2012 post.
Richard L.
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I thought this post had gone all ' Star Wars' until Richards post!
*doubt* ::hh:: *bash* *beer*