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#500867 - 08/08/13 4:14 pm Re: Magneto [Re: Magnetoman]  
Joined: Mar 2012
Posts: 56
Ken Tee, R.I.P. Offline
In Remembrance
Ken Tee, R.I.P.  Offline
In Remembrance

Joined: Mar 2012
Posts: 56
Outside Eastleigh, Hants, UK
I wasn't addressing any points about the Brightspark EasyCap condenser in my earlier post. Instead I was addressing your three statements:
Originally Posted By: Magnetoman
I = C x dV/dt

Originally Posted By: Magnetoman
the current in the primary coil collapses nearly instantaneously, giving rise to a voltage spike of several hundred volts in a few microseconds across the capacitor

Originally Posted By: Magnetoman
Plugging in values, that current is several hundred amps.

At least one of them must obviously be wrong, because {anything between 100 and 220 nanofarads} x {several hundred volts} /{a few microseconds} did not equal {several hundred amps}. And despite what you've said just now, it still doesn't.

If, on reflection, you agree with me that the first statement is correct, and that the figures in the second statement are in the right ballpark, then your third statement should refer to several amps, not several hundred amps, shouldn't it?

Ken
Brightspark Magnetos

BSA Gold Star eBay items

BSA Gold Star forum This board is dedicated to BSA Gold Star motorcycles.

#500869 - 08/08/13 4:31 pm Re: Magneto [Re: Petvet]  
Joined: Oct 2002
Posts: 544
joe a. Offline
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joe a.  Offline
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Joined: Oct 2002
Posts: 544
minnesota
i have an older power dyne on my stock absaf BSA 500 and it starts first kick normally and puts out enough to operate the pilot and the horn but i also have a led tail light i made up that consumes hardly any power. if you put the lights on the horn is a little anemic.....it does have a capacitor in the system but no battery which i like.
joe@ vcycle
www.joesvcycle.wordpress.com

#500877 - 08/08/13 4:51 pm Re: Magneto [Re: Ken Tee, R.I.P.]  
Joined: Nov 2011
Posts: 3,965
Magnetoman Online content
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Magnetoman  Online Content

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Joined: Nov 2011
Posts: 3,965
U.S.
Originally Posted By: Ken Tee
I wasn't addressing any points about the Brightspark EasyCap condenser in my earlier post.
Ken, you have stated quite strongly that every time I refer to my Bosch ZEV restoration thread where I recommend Brightspark's capacitors not be used you will object. The issue in this thread is entirely about my recommendation. Everything else is a diversion that takes time to deal with, but that doesn't address the issue.

My recommendation is based entirely on technical issues with your capacitors. As I have asked more than once, if you believe I am incorrect in my understanding of the technical aspects of your capacitors, or if there is additional relevant technical information about them that you feel I may not be aware of, why are you not providing it?

Although I easily could have overlooked something, following are extracts from your recent posts.

Originally Posted By: Ken Tee
As I understand it, what happened was that Mr Green decided to retire. ... Because his capacitors were a non-standard value, the manufacturer would only supply large orders, far more than six months' stock,
Originally Posted By: Magnetoman
Your understanding is incorrect... it was a completely standard, off-the-shelf component


Originally Posted By: Ken Tee
PS. The nominal capacitance value of the Ind. Ign. Supplies condenser was 130 nF, which definitely wasn't one of the capacitor manufacturer's standard values.
Originally Posted By: Magnetoman
Again, you are wrong. ... the Nichicon capacitors they supplied... is 150 nF, which definitely is one of their standard values.


Originally Posted By: Ken Tee
Our capacitor manufacturer does not give a current rating for our capacitors, just like Panasonic did not give a current rating for the obsolete capacitor that you recommend, ... (at least not in the March 2006 datasheet that I have seen).
Originally Posted By: Magnetoman
You are incorrect... Panasonic's data sheets rate this capacitor at 6000 V/us
I have explained more than once why dV/dt is such an important specification for capacitors used for pulsed current applications.

Originally Posted By: Ken Tee
Is it really porous? Do you have a value for its porosity? Do you have any evidence that its porosity affects its performance?
Although I have written that these oxides are porous this response, in the form of a question, avoids providing information to the contrary.

Originally Posted By: Ken Tee
As has been explained to you before, ... we conducted extensive testing of our EasyCaps in magnetos in our workshop under extreme conditions,...
Originally Posted By: Magnetoman
That's not quite accurate. ...what your web page showed ... is you had left one of your capacitors in a cup of hot water for one day and it survived. I pointed out at the time that such a test was hardly an "extreme condition."


Originally Posted By: Ken Tee
To say it is 'ozone-rich' in there is an exaggeration. You only need to look at the other components in there that are susceptible to ozone (steel, zinc, nylon and rubber) to see that.
Originally Posted By: Magnetoman
First, saying it is ozone rich is not an exaggeration. Second, metals are very much less susceptible to ozone than are organics. Third, the plastic insulators are of macroscopic thickness (at least a mm), whereas the oxide insulators separating the plates in one of your capacitors are sub-micron, so any degradation by ozone would manifest itself very much sooner indeed.


Originally Posted By: Ken Tee
Have you got a single shred of evidence...to suggest that our capacitors are susceptible to ozone, to weigh against the ever-increasing pile of evidence that in practice they are not?
Originally Posted By: Magnetoman
.. as yet you haven't provided any evidence at all, let alone an "ever-increasing pile" of it.
Also, it is always the responsibility of the seller of any item to warrant its suitability for the purpose they are selling it, never the responsibility of the buyer to prove it is not suitable. It is technical concern about the suitability of your capacitors for the purpose you are selling them that causes me not to recommend them.

Originally Posted By: Ken Tee
Whether the thing lasts for five years or fifty-five years is not a concern for the market we're aiming at.
Originally Posted By: Magnetoman
Although what you wrote above implies... customers can expect your capacitors to last for five years or longer, you have yet to provide any technical information whatever to support this. What tests have you conducted that show Brightspark's capacitors will last five years or longer subjected to the operating conditions of a magneto?

As can be seen, many of the things you wrote are incorrect, and none provide the answers that are required in order for me to change my recommendation. Since the topic of our exchange is my recommendation not to use your capacitors, if you want to continue this thread please from here forward address issues of the technical specifications of your capacitors that are directly relevant for their possible use in magnetos.

Last edited by Magnetoman; 08/08/13 4:59 pm. Reason: added quote about 5 year lifetime
#500889 - 08/08/13 5:32 pm Re: Magneto [Re: Petvet]  
Joined: Mar 2005
Posts: 9,962
John Healy Online content
John Healy  Online Content


Joined: Mar 2005
Posts: 9,962
Boston, Massachusetts
While I don't like to walk away from a good discussion, I think it is time that someone used the old English saying used by publican's to remind their customers that the time has come.

I respect that both parties have kept this discussion civil, and we appreciate that a whole lot. But the technical discussion is above the "pay grade" of most of the people reading this forum.

So with due respect to both parties may I offer the words heard through out Britain when you don't have to go home, but you cannot stay here:

"Time gentlemen!"


#500892 - 08/08/13 5:47 pm Re: Magneto [Re: Magnetoman]  
Joined: Feb 2012
Posts: 148
L.A.kevin Online content
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L.A.kevin  Online Content
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Joined: Feb 2012
Posts: 148
Los Angeles, CA
Hey MM,

I have a question regarding the modification to a magneto like Ken has been marketing that I don't believe you've touched on (if you have, and I missed it, please excuse me). So, is there an advantage to the external (at least to the armature) mounting a capacitor device like the kind that has been marketed here?

It would seem if one were to take an "anything goes" approach and rebuild a magneto for reliability, not having the capacitive device located inside a moving part would be a benefit. You could probably use the space for more windings. The capacitive device could be located external to the magneto, or maybe in the points cover.

As long as you were at it, couldn't you also update the insulator paper to one made of mylar kapton? Then there's modern low viscosity thermoset resin varnish, etc.

I have to say, I've been really enjoying these cross examinations, er... freindly discussions on this subject. I appreciate the time you have been taking and the detail of your responses and all the technical points you have been sharing. I'm an aerospace engineer and my specialty is electromechanical components. My company specializes in legacy aircraft support, and I do a lot of sustaining engineering and re-engineering. However, I'm a bit unfamiliar with motorcycle magneto circuits and like learning more. Would love to see a schematic of a K2F, for example.

Thanks again,

Kevin in Los Angeles

#500894 - 08/08/13 5:53 pm Re: Magneto [Re: Petvet]  
Joined: Aug 2001
Posts: 1,850
dave - NV Online content
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dave - NV  Online Content
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Joined: Aug 2001
Posts: 1,850
Elko, Nevada USA
Matt ... I apologize for the slow reply regards your suggestion of using the B31/33 crank mounted alternators on Goldies.
This has been done for several years and two of my friend's GS are modified with this set up.

Phil Pearson makes cranks with the unique axle required. The issue seems to be the shortage of the (ugly?) bulging primary cases needed. I've read ABSAF in Holland has repopped these cases.
Personally I'm not interested in doing this, regardless of how practical it may be.

Last edited by dave - NV; 08/08/13 5:56 pm.

dave - NV
#500895 - 08/08/13 5:58 pm Re: Magneto [Re: John Healy]  
Joined: Nov 2011
Posts: 3,965
Magnetoman Online content
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Magnetoman  Online Content

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Joined: Nov 2011
Posts: 3,965
U.S.
Originally Posted By: John Healy
you don't have to go home, but you cannot stay here:

"Time gentlemen!"
I completely agree. It's time for us to sleep it off. Or, to paraphrase an old Rumanian expression, when John tells you you're drunk, you should sit down.

#500896 - 08/08/13 6:01 pm Re: Magneto [Re: L.A.kevin]  
Joined: Nov 2011
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Magnetoman Online content
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Magnetoman  Online Content

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U.S.
Originally Posted By: L.A.kevin
It would seem if one were to take an "anything goes" approach and rebuild a magneto for reliability, not having the capacitive device located inside a moving part would be a benefit. You could probably use the space for more windings.
One last drink before exiting the pub...

Not addressing capacitors at all, I'll just note that not having something in the endcap doesn't free up more space for windings because the limitation on them is the ID of the housing, not the length of the armature. The empty space would remain empty.

#501110 - 08/10/13 9:56 am Re: Magneto [Re: L.A.kevin]  
Joined: Mar 2012
Posts: 56
Ken Tee, R.I.P. Offline
In Remembrance
Ken Tee, R.I.P.  Offline
In Remembrance

Joined: Mar 2012
Posts: 56
Outside Eastleigh, Hants, UK
Originally Posted By: L.A.kevin
... I'm a bit unfamiliar with motorcycle magneto circuits and like learning more. Would love to see a schematic of a K2F, for example...

Here are a couple of schematics, Kevin, one with the condenser in the original position buried in the armature:



and the other with the condenser fitted into the contact-breaker assembly:



All the best,

Ken
Brightspark Magnetos

#501146 - 08/10/13 4:06 pm Re: Magneto [Re: Petvet]  
Joined: Aug 2001
Posts: 6,860
triton thrasher Online content
BritBike Forum member
triton thrasher  Online Content
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Joined: Aug 2001
Posts: 6,860
scotland
Easycap Schmeasycap!



Amateur Loctite enthusiast.
#501250 - 08/11/13 7:15 am Re: Magneto [Re: triton thrasher]  
Joined: Mar 2012
Posts: 56
Ken Tee, R.I.P. Offline
In Remembrance
Ken Tee, R.I.P.  Offline
In Remembrance

Joined: Mar 2012
Posts: 56
Outside Eastleigh, Hants, UK
True enough, TT, an externally connected condenser can work, as many machines on the road today are proving. But as far as I can make out, it's reliant on three things.
  • The old condenser either needs to have been disconnected, or it needs to have failed so that it's more-or-less open circuit and doesn't affect things things too much.
  • The cut-out brush needs to be in good condition.
  • The earth brush needs to be in good condition, or else there needs to be some other good return path for the condenser current from the magneto body earth back to the armature earth (such as a shorting bearing insulator, or a nicely conductive drive train from the engine to the armature shaft).
Typically the cut-out and earth brushes present a resistance of the order of 10 ohms each, which is significant when the condenser current pulses that they are supposed to be passing are several amps (and would be more so, of course, if they were several hundred amps!)

Ken
Brightspark Magnetos

#501251 - 08/11/13 7:36 am Re: Magneto [Re: Petvet]  
Joined: Aug 2001
Posts: 6,860
triton thrasher Online content
BritBike Forum member
triton thrasher  Online Content
BritBike Forum member

Joined: Aug 2001
Posts: 6,860
scotland
I wasn't being entirely serious, but that was my bike yesterday.

Last time I looked at the points, they looked a bit blasted and there was a stain on the spring, where it passes near the points. There wasn't much obvious sparking at the points when kicking it over, though.

I jammed that old condenser on for fun and it might be starting and running slightly better. Not sure though- could be the damp weather.


Amateur Loctite enthusiast.
#501255 - 08/11/13 8:03 am Re: Magneto [Re: triton thrasher]  
Joined: Mar 2012
Posts: 56
Ken Tee, R.I.P. Offline
In Remembrance
Ken Tee, R.I.P.  Offline
In Remembrance

Joined: Mar 2012
Posts: 56
Outside Eastleigh, Hants, UK
With a condenser arrangement that's half doing its job, it seems that arcing at the points may only show up at higher revs.

There's a couple of video clips on this page showing arcing at the points, over the speed range with internal and external condensers.

#510661 - 10/16/13 6:31 pm Re: Magneto [Re: Ken Tee, R.I.P.]  
Joined: Aug 2006
Posts: 92
Petvet Offline
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Petvet  Offline
BritBike Forum member

Joined: Aug 2006
Posts: 92
Ocean City, New Jersey, USA
As a follow-up to my original post I sent the magneto to Doug Wood for a rebuild. It apparently had seen better years. This week I finally got around to installing it and then timing the bugger. I forgot what a pain it was to get the contacts just opening, tap the mag gear in place, tighten up, and then see if everything stayed at 39 before TDC.

End result - started first kick and now idles perfectly at 1100.

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