Poor starting on new Amal and BTH Magneto

[Magnetoman]

This is an old telltale method to see firsthand if the condenser is indeed at fault ,..., switch off the lights in your garage , must be in the dark . ... This sparking is eating up the points all the while during operation . Preferably replaced with freshly produced , NOT a nos item ...
Be aware that sparking contacts produce OZONE gas which is corrosive ,...

A couple of comments on this. Lucas condensers have an exponential dependence of leakage on temperature, so the initial sign of a stock Lucas condenser going bad is for the magneto to work fine when cold, but to develop a miss as it warms up. So, my first comment is that even if your condenser passes this sparking test first thing in the morning, it doesn't eliminate it from being at fault for your magneto's problem. "Luckily," the darkness of the garage is not a requirement. If your engine starts missing as it warms up, the sparks across the points from a bad condenser will be quite apparent even in daylight.

The real problem with the sparking created by a bad condenser isn't so much that they are eating up the points (which they are), but that they are both sucking energy out of the system that is needed at the spark plug gap to ignite the mixture, as well as altering the timing by radomly delaying the spark. As for ozone, yes indeed, it is a very powerful oxidizer. The design of Lucas and BTH rotating armature magnetos places their condensers outside the points compartment where they are not exposed to ozone where they would be subjected to the elevated ozone levels that are present even in a compartment that is vented (which would be even worse if not vented). The fact that ozone is a serious issue is evidenced by even 'wader' magnetos being vented, despite wanting them to be water tight.

 

[Big Sid]

Nicely commented on . However nothing I pointed out is not factual or overstated . Certainly the entire contact breaker mechanism is exposed to the Ozone created so having a vent is wise , and easily done .
I do appreciate the comments from Magnetoman a truly fine and experianced source for such knowledge . Sid .

 

[Big Sid]

A further dredged up memory may be of passing interest . The Shellac material that the armatures were potted with is derived from insect husks would you believe . It does very well at insulating the tight windings but it is not unknown to soften with age and lose its grip on those coils , sometimes leading to problems , ie shorting out between overlapping turns . Something else to worry you .
No one was ever promised a Rose Garden . Sid .

 

[Magnetoman]

However nothing I pointed out is not factual or overstated . Certainly the entire contact breaker mechanism is exposed to the Ozone created so having a vent is wise , and easily done ...

I didn't mean to imply anything you wrote was incorrect. I was just adding to the information you provided.

Ozone is a very real problem, and the vent doesn't actually solve it, it only reduces it sufficiently that the breaker mechanism will survive normal replacement intervals. The ozone that is constantly generated by even the normal small sparking at the points with a good condenser can only leave the housing (if vented) via diffusion, which is a slow process. Hence the ozone levels inside even a vented housing are considerably higher than in normal air. I actually have a spectrometer perfectly suited for measuring the ozone concentration inside the points housing via its strong absorption at a particular wavelength in the UV, and doing so has been on my motorcycle projects to-do list for a while. But, realistically, doing so isn't likely to slip past other projects to make it to the top of my list.

 

[clevtrev]

A further dredged up memory may be of passing interest . The Shellac material that the armatures were potted with is derived from insect husks would you believe . It does very well at insulating the tight windings but it is not unknown to soften with age and lose its grip on those coils , sometimes leading to problems , ie shorting out between overlapping turns . Something else to worry you .
No one was ever promised a Rose Garden . Sid .

Not derived from insect husks at all. The Lac bug eats tree sap and the resulting exctreta, is deposted on the tree, where it dries into flakes, from where it is harvested. So one really needs to know what happens. ;-)
My old 78`s have not gone soft yet, but then, they have not been exposed to oil and petrol.

 

[Big Sid]

So you know more about bug poop than me Trev , took a lot of getting down on your knees to acquire that gem . I yeald Whatever
Winds your clock as they say . Sid .

 

[mercurycrest]

So you know more about bug poop than me Trev , took a lot of getting down on your knees to acquire that gem . I yeald Whatever
Winds your clock as they say . Sid .

Sid.
Did you just say "I don't know Sh**?"

 

[redbloke1956]

A couple of comments on this. Lucas condensers have an exponential dependence of leakage on temperature, so the initial sign of a stock Lucas condenser going bad is for the magneto to work fine when cold, but to develop a miss as it warms up. So, my first comment is that even if your condenser passes this sparking test first thing in the morning, it doesn't eliminate it from being at fault for your magneto's problem. "Luckily," the darkness of the garage is not a requirement. If your engine starts missing as it warms up, the sparks across the points from a bad condenser will be quite apparent even in daylight.

The real problem with the sparking created by a bad condenser isn't so much that they are eating up the points (which they are), but that they are both sucking energy out of the system that is needed at the spark plug gap to ignite the mixture, as well as altering the timing by radomly delaying the spark. As for ozone, yes indeed, it is a very powerful oxidizer. The design of Lucas and BTH rotating armature magnetos places their condensers outside the points compartment where they are not exposed to ozone where they would be subjected to the elevated ozone levels that are present even in a compartment that is vented (which would be even worse if not vented). The fact that ozone is a serious issue is evidenced by even 'wader' magnetos being vented, despite wanting them to be water tight.

Hi Magnetoman,
I follow your comments with great interest, while I was aware of the production of ozone from electrical discharge, and strangely never made the connection to it being a "very powerful oxidiser", I am wondering if therefore ventilation of d.c. generators should also be carried out for the same reason i.e. arcing at the brushes/commutator?

Regards
Kevin

 

[redbloke1956]

Hello Phil, good to hear you are still persevering with the Comet.

Any interesting comment from Phil Primmer about ten years ago was "not" to fit a spare spark plug in the second hole. Phil's thoughts were that the electrode, due to not igniting the mixture and producing a burn away from the plug, would result in the plug electrode absorbing heat and becoming a "hot spot" over the time of a ride. Now, having no experience of such I can not comment any further and can only ask other people to express their thoughts on the matter. Does your Comet have the boss present in the crankcase for a valve lifter mechanism? also, clearance between the outside and the Burman gearbox is very limited. You may need to remove the mountings for the Burman and shove it as far rearwards as possible to give you enough space to offer the E218 to the boss. However I must say, with mine assembled with silicone grease in the seals, there are no obvious leaks from their yet!.

Ignition timing, yes BT-H have recommended 6 degrees less advance for the twin-spark variant, so that has been taken into account.

Are you going to make the Portsmouth meet next weekend? weather dependant, I am hoping to make it on the Comet. Piccie!

Hi Minivin, Ya gotta admit that the Comet looks better than a twin with only half the problems Nice looking Comet mate, are they the Speet? TLS on the front and how good are they (if you have something to compare with)

Regards
Kevin

 

[Magnetoman]

I am wondering if therefore ventilation of d.c. generators should also be carried out for the same reason i.e. arcing at the brushes/commutator?

That's an excellent question. I don't know the equivalent in Australia (maybe the same?), but in the U.S. in the 1950s boys grew up with Lionel electric train sets. I can still smell the odor of what I now know is ozone from those trains. So, since a motor is just a generator operated backwards, doesn't this mean our dynamos are generating ozone as well? The answer is essentially no, but to understand the reason requires a short physics lecture.

Ozone is created when the chemical bond in an oxygen molecule (02) is broken, creating two individual oxygen atoms that are each now free to chemically bond to intact 02 molecules to form ozone (O3). The minimum energy that must be supplied to break the chemical bond in O2 to get this started is 5.2 electron Volts.(eV). While your 6V dynamo nominally is capable of this when at maximum output, the efficiency of doing so is small so near the threshhold voltage, so very little ozone is generated. A Lionel train operated at ~20 V when at full speed, and what boy operated his train at anything other than full speed? (note: Volt and eV are not the same units, but they are related in that an electron accelerated between two electrodes held at a 20 V potential difference will gain 20 eV of energy).

In contrast, the potential across the points in a magneto is several hundred volts when they open, which is far enough higher than the threashold to make for greatly increased ozone production. Further, the ionization cross section (i.e. the probability an energetic electron will knock another electron free from a molecule thus creating an ion) for most molecules has a broad peak centered around ~100 Volts. So, molecules in the vicinity of the spark gap in a magneto are being ionized with great efficiency as well, and ionized species are typically much more chemically reactive than unionized atoms and molecules.

Having given the long answer to your question, the short answer is that because the voltages inside a dynamo are much lower than inside the points housing of a magneto, ozone production is at a very much lower rate. The much lower production of ozone, coupled with the fact he commutator housing is far from hermetically sealed, means it isn't an issue for a dynamo.