Author Topic: fitting one of those new condenser thingy's  (Read 692 times)

Offline Swarfcut

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Re: fitting one of those new condenser thingy's
« Reply #15 on: 05.09. 2020 07:55 »
Trev, That is an interesting thought, if we consider a failure to be a simple open circuit, this is acceptable for capacitors in parallel. Failure due to an internal short certainly is not, and I can see the reason for the so called snip or condensectomy.

 So I would reckon if you were prepared to risk your newly purchased Easycap, simply fitting it as is would be worth a quick try.

 I found this, and while not strictly within the motorcycle sphere, explains what happens in condenser failure in some cases and offers a possible reason for the unreliable nature of some of our so called Classic Cars when they were new.

http://nonlintec.com/sprite/cap_failure/

 bergs can look away now.

 Swarfy

Online groily

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Re: fitting one of those new condenser thingy's
« Reply #16 on: 05.09. 2020 08:12 »
If a condenser has failed open circuit, then stuffing a second one on, whether an EasyCap or even a remote jobbie using brushes etc to make the contacts (highly inefficient!), can work. But most don't fail open circuit, which is the problem, and having a good 'un and a bad 'un in tandem doesn't solve things.

See for some boring detail, and also some pix
http://www.brightsparkmagnetos.com/faqs/FAQs%20about%20magneto%20condensers%20in%20particular/index.htm

As to what is the correct capacitance to do the job, there are reams of stuff out there in tekkie papers etc (much of it way above my pay grade). but as a practical demonstration of different capacitances, these videos may amuse
http://www.brightsparkmagnetos.com/gallery/CB_arcing.htm
Bill

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Re: fitting one of those new condenser thingy's
« Reply #17 on: 05.09. 2020 09:16 »
In my experience (employment rather than old cars and bikes) capacitors "fail" due to ageing, and over time become less and less efficient, but even when totally useless for their intended task they still show continuity.
Due to their physical construction, failing either open circuit or short circuit must be most unusual, hence the requirement to remove them from the circuitry in old mags.

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Re: fitting one of those new condenser thingy's
« Reply #18 on: 05.09. 2020 14:11 »
could this brush piccy have been my problem---- discus --- I had a bit more time to study things today and compared 2 brushes. the one on the bottom of photo is from the maggy that up to a few days ago was ok then started miss firing pulling away from junctions and at about 1500 to 2000 revs . once it had got through its spluttering it was ok for a while then sort of gave up after I found the points gap was only 6 thou and opened it up to 12 . after that it was no go. the piccy of the armature tries to show the condensers and are these the modern things they put in? I can just make out FA 271M and swb printed on them. cheers

Online groily

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Re: fitting one of those new condenser thingy's
« Reply #19 on: 05.09. 2020 14:57 »
Don't think the manky brush will have been the prob berger. They often look like that after a few years and as long as the thing contacts the mag armature, they work. You could easily prove the point with a meter if you felt like it.
If you have a cb with the hole for an auxiliary brush on the rear face, you could always fit one there for future double-sure fail-safe running.
And bear in mind that on mags with steel drive gear components the armature is also earthed, if imperfectly, by that route too. (Not if an ATD with fibre gear is on there though  . . .) A lot are also earthed through the bearings due to deformed, broken or knackered insulator cups - but they shouldn't be!

The condenser in the picture is one, or a pair of (can't see too well with ageing eyeballs) Evox Rifa PME271. A common fitment. The coil was probably rewound by APL Magnetos down near Shaftesbury and will almost certainly be very good. The condenser may have failed though, as sh1t happens.
Bill

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Re: fitting one of those new condenser thingy's
« Reply #20 on: 05.09. 2020 18:20 »
on the money again groily *yeah* I tried both carbons and the plugs spark was what I would call good in the atmosphere.  there are 2 of those flat faced thingy's in there-- condenser's . how are these maggy's tested on a bench to make sure the spark will be good under pressure? or do you use special equipment to make sure things are as they should be? I might have to have it tested before I trust it on an engine which could lead to many £££££'s

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Re: fitting one of those new condenser thingy's
« Reply #21 on: 05.09. 2020 18:56 »
Basically by using an exaggeratedly big spark gap Berger. Lucas said 5.5mm, three point gap and a lot of other stuff. Coil testers and all that  . . .
But if you grind the earth electrode off a spare plug and use that, it's better than nothing and offers a gap of getting on for 4mm. You'll get a good 'thwack' as the mag sparks with it. (IIRC - and it's evening here and the BBQ is lit and it's all downhill from now on! - every 0.8mm of gap equals an atmosphere, or something like. So 5.5 mm = 7:1 cr roughly, which was an adequate test back n the day).

At home, a good thing to do is to borrow a hair drier, or use a heat gun, and get the armature / mag hot to the touch - like hot enough to touch still (50°C ish), but not boiling to death - and test for the spark. If you've got a slow-speed drill, turn the mag and see if it makes good sparks when it's hot. Cold, you'd expect to see sparks from about 130rpm and hot from say 160-170 ish (advanced).

With that coil, I don't think you have a problem. I really don't. It is 99% sure to be good.

But I think you need to cut the condenser(s) out and try another. I think if you do you'll get to happy. I really do.

If you can prise out the low tension wire - the double-strand wire - on the side of the armature opposite the boss on the slipring where the HT connects to it, that's the live one - then you should be able to snip it, ensure the two strands are still well-connected, and insulate the exposed end wi' a bit o' heatshrink and instal your easycap on the points in place of the insulator between block and backplate.

I'm pretty confident in this case  . . . but as I often say, Famous Last Words - and don't kill me if it all goes pear-shaped and your beer goes down the wrong way!
Bill

Offline Bsareg

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Re: fitting one of those new condenser thingy's
« Reply #22 on: 05.09. 2020 18:58 »
Being a curious bu**er I cut open a Lucas mag condenser  to see its construction. It was giving a reading of 25, 000 ohms when it should look like an open circuit. It was a folded up sandwich of foil and paper. The problem was moisture must have got in because a lot of the foil had turned green and making a circuit. Easy cap screwed  on, end of problem.
C11,B40,B44 Victor,A10,RGS,M21,Rocket3,REBSA

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Re: fitting one of those new condenser thingy's
« Reply #23 on: 05.09. 2020 21:41 »
groily /  bill have a good bbq and get some  *beer*, what you have just done is given me the confidence to go further with this maggy and do the tests you mention. thanks for all your input but don't be surprised if I don't go away too quickly *whistle*

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Re: fitting one of those new condenser thingy's
« Reply #24 on: 06.09. 2020 13:10 »
well chaps I think the journey stops here. I set the points firstly to 12 ish thou and did some tests, then 15 thou ish and repeated.--- I have spun the armature between finger and thumb and got nice big sparks to jump 5mm at least with the thwack groily mentioned. this same spark is continuous with speed and stops sparking after 5ish mm gap. I have done this with HT leads on there own and plugs in caps and got the same result *good3*. does any body think the miss firing it developed could have been the oil coating on the magnets effecting there efficiency ? I know nothing about this except my other mag ran with oil dripping from the points cover-----. thank you all for the input and information on this subject *thanks* …. ps I will not be putting it back on because it takes me half a day to do on my bike ;)

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Re: fitting one of those new condenser thingy's
« Reply #25 on: 06.09. 2020 16:33 »
Just before you call a halt berger, heat the thing up if you haven't. Heat is the enemy in all of this. You certainly seem to have a half decent or better spark cold - but what happens hot is the remaining Big Question.

Oil: A lot of oil on the slipring, or worse still on the points, could well upset the applecart, sure  . . .  but a bit of slime doesn't kill a magnet, as your other mag proved, so I'd be surprised if that was the cause if the slipring/brushes and points were clean. It's quite amazing how contaminated some mags get, with oil getting in down the plug cables, oil seals falling to bits, you name it. And yet they still work electrically despite everything.

Bill

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Re: fitting one of those new condenser thingy's
« Reply #26 on: 06.09. 2020 18:58 »
I will do that tomorrow bill, my brother said it could! be the magnetic density not as good as the other mag that had oil all over it. heat tomorrow and try again, fingers crossed

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Re: fitting one of those new condenser thingy's
« Reply #27 on: 07.09. 2020 14:03 »
I got the maggy hot , as hot as I have felt it on the bike and it cracks off good sparks between finger and thumb with a wide gap of at least 5mm. it also does the same at revs so the gremlin seems to have gone. i am going to add oil to the magnets to simulate how it was and test again, are you excited? i am *roll*

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Re: fitting one of those new condenser thingy's
« Reply #28 on: 07.09. 2020 14:17 »
As excited as a field coil.

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Re: fitting one of those new condenser thingy's
« Reply #29 on: 07.09. 2020 19:14 »
exciter volts have produced the excitement. well the oil film has any way. I set up the maggy with a good dose of oil on the magnets like it was when it was acting the pillock.  the result was only half of the spark jump turning with finger and thumb or running faster. also missing some sparks, and this was how it was running on the bike. maybe the oil film reduced the magnetic density acting as a barrier on this mag and the competition mag might have better magnets and overcome this when it was full of oil. I cleaned it all up and the sparks are jumping big gaps!!.  They told me they are feeling better. so a new oil seal will be fitted and maggy can have a rest in the bedroom until I need to shout her to do some work *work*