Magneto
12-01-2003, 07:49 PM
#41
Guest
Posts: n/a
Re: Magneto
Hi Lon,
Some of magnetos still sold today, although, Mallory is how calling
theirs a generator:
http://www.speedwaymotors.com/xq/asp...st_display.htm
I think the reason they still use points is the magnetic pickup loses
it's dwell somewhere around six grand, where points will exceed ten
grand.
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/
Lon Stowell wrote:
>
> Approximately 12/1/03 13:44, CRWLR uttered for posterity:
>
> > I think that if a magneto ignition was suitable for use on an automobile,
> > then we would still be using them today instead of having devised a means of
> > getting rid of them 70-some-odd years ago.
>
> Judson magnetos were still popular as a more reliable and
> higher performance replacement for the stock ignition in
> British sports cars a mere 35-40 years ago. Whether this
> is evidence of merit for the magneto or a comment on
> British electrics may be a matter of personal opinion.
>
> They were still popular as working better than the first
> coupla generations of transistor ignition systems. Then
> somebody from the radar engineer folks married a pulse
> transformer to a magnetron type supply with solid state
> controls and pretty much kept all of the benefits of
> the magneto [better high rpm performance due to dI/dT]
> and the transistor [better low rpm performance] by using
> multiple pulses at low rpm, tailing off the number of
> such as rpm rose. Some of these used the standard points, some
> used optical pickups, some used the emerging hall effect
> sensors.
>
> As soon as good high energy ignition systems from the
> manufacturers hit the streets, magnetos pretty much
> disappeared, only to be remembered by aging pilots and
> old farts.
>
> --
> Still a Raiders fan, but no longer sure why.
Some of magnetos still sold today, although, Mallory is how calling
theirs a generator:
http://www.speedwaymotors.com/xq/asp...st_display.htm
I think the reason they still use points is the magnetic pickup loses
it's dwell somewhere around six grand, where points will exceed ten
grand.
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/
Lon Stowell wrote:
>
> Approximately 12/1/03 13:44, CRWLR uttered for posterity:
>
> > I think that if a magneto ignition was suitable for use on an automobile,
> > then we would still be using them today instead of having devised a means of
> > getting rid of them 70-some-odd years ago.
>
> Judson magnetos were still popular as a more reliable and
> higher performance replacement for the stock ignition in
> British sports cars a mere 35-40 years ago. Whether this
> is evidence of merit for the magneto or a comment on
> British electrics may be a matter of personal opinion.
>
> They were still popular as working better than the first
> coupla generations of transistor ignition systems. Then
> somebody from the radar engineer folks married a pulse
> transformer to a magnetron type supply with solid state
> controls and pretty much kept all of the benefits of
> the magneto [better high rpm performance due to dI/dT]
> and the transistor [better low rpm performance] by using
> multiple pulses at low rpm, tailing off the number of
> such as rpm rose. Some of these used the standard points, some
> used optical pickups, some used the emerging hall effect
> sensors.
>
> As soon as good high energy ignition systems from the
> manufacturers hit the streets, magnetos pretty much
> disappeared, only to be remembered by aging pilots and
> old farts.
>
> --
> Still a Raiders fan, but no longer sure why.
12-01-2003, 07:49 PM
#42
Guest
Posts: n/a
Re: Magneto
Hi Lon,
Some of magnetos still sold today, although, Mallory is how calling
theirs a generator:
http://www.speedwaymotors.com/xq/asp...st_display.htm
I think the reason they still use points is the magnetic pickup loses
it's dwell somewhere around six grand, where points will exceed ten
grand.
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/
Lon Stowell wrote:
>
> Approximately 12/1/03 13:44, CRWLR uttered for posterity:
>
> > I think that if a magneto ignition was suitable for use on an automobile,
> > then we would still be using them today instead of having devised a means of
> > getting rid of them 70-some-odd years ago.
>
> Judson magnetos were still popular as a more reliable and
> higher performance replacement for the stock ignition in
> British sports cars a mere 35-40 years ago. Whether this
> is evidence of merit for the magneto or a comment on
> British electrics may be a matter of personal opinion.
>
> They were still popular as working better than the first
> coupla generations of transistor ignition systems. Then
> somebody from the radar engineer folks married a pulse
> transformer to a magnetron type supply with solid state
> controls and pretty much kept all of the benefits of
> the magneto [better high rpm performance due to dI/dT]
> and the transistor [better low rpm performance] by using
> multiple pulses at low rpm, tailing off the number of
> such as rpm rose. Some of these used the standard points, some
> used optical pickups, some used the emerging hall effect
> sensors.
>
> As soon as good high energy ignition systems from the
> manufacturers hit the streets, magnetos pretty much
> disappeared, only to be remembered by aging pilots and
> old farts.
>
> --
> Still a Raiders fan, but no longer sure why.
Some of magnetos still sold today, although, Mallory is how calling
theirs a generator:
http://www.speedwaymotors.com/xq/asp...st_display.htm
I think the reason they still use points is the magnetic pickup loses
it's dwell somewhere around six grand, where points will exceed ten
grand.
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/
Lon Stowell wrote:
>
> Approximately 12/1/03 13:44, CRWLR uttered for posterity:
>
> > I think that if a magneto ignition was suitable for use on an automobile,
> > then we would still be using them today instead of having devised a means of
> > getting rid of them 70-some-odd years ago.
>
> Judson magnetos were still popular as a more reliable and
> higher performance replacement for the stock ignition in
> British sports cars a mere 35-40 years ago. Whether this
> is evidence of merit for the magneto or a comment on
> British electrics may be a matter of personal opinion.
>
> They were still popular as working better than the first
> coupla generations of transistor ignition systems. Then
> somebody from the radar engineer folks married a pulse
> transformer to a magnetron type supply with solid state
> controls and pretty much kept all of the benefits of
> the magneto [better high rpm performance due to dI/dT]
> and the transistor [better low rpm performance] by using
> multiple pulses at low rpm, tailing off the number of
> such as rpm rose. Some of these used the standard points, some
> used optical pickups, some used the emerging hall effect
> sensors.
>
> As soon as good high energy ignition systems from the
> manufacturers hit the streets, magnetos pretty much
> disappeared, only to be remembered by aging pilots and
> old farts.
>
> --
> Still a Raiders fan, but no longer sure why.
12-01-2003, 07:49 PM
#43
Guest
Posts: n/a
Re: Magneto
Hi Lon,
Some of magnetos still sold today, although, Mallory is how calling
theirs a generator:
http://www.speedwaymotors.com/xq/asp...st_display.htm
I think the reason they still use points is the magnetic pickup loses
it's dwell somewhere around six grand, where points will exceed ten
grand.
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/
Lon Stowell wrote:
>
> Approximately 12/1/03 13:44, CRWLR uttered for posterity:
>
> > I think that if a magneto ignition was suitable for use on an automobile,
> > then we would still be using them today instead of having devised a means of
> > getting rid of them 70-some-odd years ago.
>
> Judson magnetos were still popular as a more reliable and
> higher performance replacement for the stock ignition in
> British sports cars a mere 35-40 years ago. Whether this
> is evidence of merit for the magneto or a comment on
> British electrics may be a matter of personal opinion.
>
> They were still popular as working better than the first
> coupla generations of transistor ignition systems. Then
> somebody from the radar engineer folks married a pulse
> transformer to a magnetron type supply with solid state
> controls and pretty much kept all of the benefits of
> the magneto [better high rpm performance due to dI/dT]
> and the transistor [better low rpm performance] by using
> multiple pulses at low rpm, tailing off the number of
> such as rpm rose. Some of these used the standard points, some
> used optical pickups, some used the emerging hall effect
> sensors.
>
> As soon as good high energy ignition systems from the
> manufacturers hit the streets, magnetos pretty much
> disappeared, only to be remembered by aging pilots and
> old farts.
>
> --
> Still a Raiders fan, but no longer sure why.
Some of magnetos still sold today, although, Mallory is how calling
theirs a generator:
http://www.speedwaymotors.com/xq/asp...st_display.htm
I think the reason they still use points is the magnetic pickup loses
it's dwell somewhere around six grand, where points will exceed ten
grand.
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/
Lon Stowell wrote:
>
> Approximately 12/1/03 13:44, CRWLR uttered for posterity:
>
> > I think that if a magneto ignition was suitable for use on an automobile,
> > then we would still be using them today instead of having devised a means of
> > getting rid of them 70-some-odd years ago.
>
> Judson magnetos were still popular as a more reliable and
> higher performance replacement for the stock ignition in
> British sports cars a mere 35-40 years ago. Whether this
> is evidence of merit for the magneto or a comment on
> British electrics may be a matter of personal opinion.
>
> They were still popular as working better than the first
> coupla generations of transistor ignition systems. Then
> somebody from the radar engineer folks married a pulse
> transformer to a magnetron type supply with solid state
> controls and pretty much kept all of the benefits of
> the magneto [better high rpm performance due to dI/dT]
> and the transistor [better low rpm performance] by using
> multiple pulses at low rpm, tailing off the number of
> such as rpm rose. Some of these used the standard points, some
> used optical pickups, some used the emerging hall effect
> sensors.
>
> As soon as good high energy ignition systems from the
> manufacturers hit the streets, magnetos pretty much
> disappeared, only to be remembered by aging pilots and
> old farts.
>
> --
> Still a Raiders fan, but no longer sure why.
12-01-2003, 09:26 PM
#44
Guest
Posts: n/a
Re: Magneto
On 01 Dec 2003 12:44 PM, CRWLR posted the following:
> I think that if a magneto ignition was suitable for use on an
> automobile, then we would still be using them today instead of having
> devised a means of getting rid of them 70-some-odd years ago.
If automobiles had certification requirements similar to those found in
the aviation world, we would still be using mags in our cars.
Electronic ignition is only now just beginning to be used in piston
aircraft, and has a long way to go before it can be considered common.
----------------------------------------------------
Del Rawlins- del@_kills_spammers_rawlinsbrothers.org
Remove _kills_spammers_ to reply via email.
Unofficial Bearhawk FAQ website:
http://www.rawlinsbrothers.org/bhfaq/
> I think that if a magneto ignition was suitable for use on an
> automobile, then we would still be using them today instead of having
> devised a means of getting rid of them 70-some-odd years ago.
If automobiles had certification requirements similar to those found in
the aviation world, we would still be using mags in our cars.
Electronic ignition is only now just beginning to be used in piston
aircraft, and has a long way to go before it can be considered common.
----------------------------------------------------
Del Rawlins- del@_kills_spammers_rawlinsbrothers.org
Remove _kills_spammers_ to reply via email.
Unofficial Bearhawk FAQ website:
http://www.rawlinsbrothers.org/bhfaq/
12-01-2003, 09:26 PM
#45
Guest
Posts: n/a
Re: Magneto
On 01 Dec 2003 12:44 PM, CRWLR posted the following:
> I think that if a magneto ignition was suitable for use on an
> automobile, then we would still be using them today instead of having
> devised a means of getting rid of them 70-some-odd years ago.
If automobiles had certification requirements similar to those found in
the aviation world, we would still be using mags in our cars.
Electronic ignition is only now just beginning to be used in piston
aircraft, and has a long way to go before it can be considered common.
----------------------------------------------------
Del Rawlins- del@_kills_spammers_rawlinsbrothers.org
Remove _kills_spammers_ to reply via email.
Unofficial Bearhawk FAQ website:
http://www.rawlinsbrothers.org/bhfaq/
> I think that if a magneto ignition was suitable for use on an
> automobile, then we would still be using them today instead of having
> devised a means of getting rid of them 70-some-odd years ago.
If automobiles had certification requirements similar to those found in
the aviation world, we would still be using mags in our cars.
Electronic ignition is only now just beginning to be used in piston
aircraft, and has a long way to go before it can be considered common.
----------------------------------------------------
Del Rawlins- del@_kills_spammers_rawlinsbrothers.org
Remove _kills_spammers_ to reply via email.
Unofficial Bearhawk FAQ website:
http://www.rawlinsbrothers.org/bhfaq/
12-01-2003, 09:26 PM
#46
Guest
Posts: n/a
Re: Magneto
On 01 Dec 2003 12:44 PM, CRWLR posted the following:
> I think that if a magneto ignition was suitable for use on an
> automobile, then we would still be using them today instead of having
> devised a means of getting rid of them 70-some-odd years ago.
If automobiles had certification requirements similar to those found in
the aviation world, we would still be using mags in our cars.
Electronic ignition is only now just beginning to be used in piston
aircraft, and has a long way to go before it can be considered common.
----------------------------------------------------
Del Rawlins- del@_kills_spammers_rawlinsbrothers.org
Remove _kills_spammers_ to reply via email.
Unofficial Bearhawk FAQ website:
http://www.rawlinsbrothers.org/bhfaq/
> I think that if a magneto ignition was suitable for use on an
> automobile, then we would still be using them today instead of having
> devised a means of getting rid of them 70-some-odd years ago.
If automobiles had certification requirements similar to those found in
the aviation world, we would still be using mags in our cars.
Electronic ignition is only now just beginning to be used in piston
aircraft, and has a long way to go before it can be considered common.
----------------------------------------------------
Del Rawlins- del@_kills_spammers_rawlinsbrothers.org
Remove _kills_spammers_ to reply via email.
Unofficial Bearhawk FAQ website:
http://www.rawlinsbrothers.org/bhfaq/
12-01-2003, 10:03 PM
#47
Guest
Posts: n/a
Re: Magneto
On 01 Dec 2003 01:02 PM, CRWLR posted the following:
> My lawn mower has a magneto and has no battery or alternator. The
> magneto replaces the ignition system, not the charging system. It also
> is a magnetic device not a points-based device as another poster
> suggested -- perhaps the powerful magnet is the basis for the name,
> magneto. The large magnet whirling around the pick up is what creates
> the electrical pulse needed for the ignition, not opening and closing
> points.
That's the point. If your lawnmower had an automotive type ignition
system, it would need a battery and alternator or generator to run. The
magneto doesn't replace the battery or alternator for engine starting or
running accessories, but it does eliminate the need for a charging
system with regard to the ignition. An airplane can suffer a total
electrical system failure (as I did one day) and the engine keeps firing
just fine.
The magneto does use points and the timing of the points is critical to
the operation of the mag. All the magnet does is generate electrical
current, and the pulse is generated by the opening of the points which
interrupts current in the primary windings of the coil. This causes the
magnetic field which was induced in the primary windings to collapse,
which in turn induces a high voltage current in the secondary windings.
It is the current induced in the secondary windings of the coil which
are sent to the plugs via the distributor. A magneto is really just a
self-contained system which includes the generator, points, coil, and
distributor all in one handy package. I can post a schematic if you'd
like, since I took a test on aircraft ignition systems a few weeks ago
and still have textbooks and stuff laying around (I'm about 6 months
away from having my A&P mechanic's certificate).
> I have never seen a magneto system that uses any sort of advance. but
> this could be acheived relatively easily. All that is needed is to
> mount the pick up on a plate that rotates around the crank shaft. Then,
> all that would be required is a means of moving this plate a few
> degrees when it was desired. Like I said, I have not seen this sort of
> thing, but it shouldn't be impossible to acheive.
It isn't done simply because mags are mostly used in aircraft these days,
which run for hours on end in the same narrow range of RPM and power
output (the same could be said for your mower). The timing can be fixed
at the optimal setting for these conditions, so there isn't much to be
gained by a variable advance mechanism and it would be just one more
thing to fail.
> I think the largest
> problem to solve in the magneto system is the length of time it takes
> to build enough charge to give a powerful spark. I am not positive,
> but I think part of the reason that airplanes have two magnetos is
> that they are on half cycle duty cycle. That is, they fire alternately
> so that they get a rest between firings. Admittedly, that is a SWAG,
> but I thought I would throw it out anyway.
That is incorrect. Both mags fire each cylinder simultaneously (two
plugs per cylinder).
> Airplanes could use two
> just so that there is a back up system in case the primary ignitin
> system fails. A plane, after all, has considerable safety problems
> when the motor quits running, all that happens to a car is that it
> rolls to the side of the road.
The most often quoted reason for two mags is reliability as you mention,
but that is followed with "oh by the way" the engine won't run right or
make anywhere near full power on just one mag. This is because aircraft
engines typically have huge pistons and the flame front won't propogate
correctly without both spark plugs firing. In most cases the loss of a
mag should allow you to limp home but if you are heavy or at a high
density altitude that is by no means certain. It may mean that you just
have more time to choose the crash site.
> An automobile has space constraints that would prohibit the
> application of a magneto,
You should try working on an airplane sometime. 8^P
> and one would still need the alternator to
> power the other electrical systems on board. It makes more sense from
> a design perspective to use the charging system to set up the
> electrical pulse needed to get the spark, then use a timing system to
> provide the spark at the correct instant.
I am in total agreement. The only reason that mags are any good at all
on an aircraft is because we use two of them. Work is underway to
switch to more modern equipment, but the aviation world is extremely
resistant to change for a number of reasons. About the only place
modern ignition is seen in any significant numbers (significant being a
relative term) is in the experimental/homebuilt world. And a lot of
those guys retain one of their mags just for redundancy.
We now return you to your regularly scheduled Jeep newsgroup. 8^)
----------------------------------------------------
Del Rawlins- del@_kills_spammers_rawlinsbrothers.org
Remove _kills_spammers_ to reply via email.
Unofficial Bearhawk FAQ website:
http://www.rawlinsbrothers.org/bhfaq/
> My lawn mower has a magneto and has no battery or alternator. The
> magneto replaces the ignition system, not the charging system. It also
> is a magnetic device not a points-based device as another poster
> suggested -- perhaps the powerful magnet is the basis for the name,
> magneto. The large magnet whirling around the pick up is what creates
> the electrical pulse needed for the ignition, not opening and closing
> points.
That's the point. If your lawnmower had an automotive type ignition
system, it would need a battery and alternator or generator to run. The
magneto doesn't replace the battery or alternator for engine starting or
running accessories, but it does eliminate the need for a charging
system with regard to the ignition. An airplane can suffer a total
electrical system failure (as I did one day) and the engine keeps firing
just fine.
The magneto does use points and the timing of the points is critical to
the operation of the mag. All the magnet does is generate electrical
current, and the pulse is generated by the opening of the points which
interrupts current in the primary windings of the coil. This causes the
magnetic field which was induced in the primary windings to collapse,
which in turn induces a high voltage current in the secondary windings.
It is the current induced in the secondary windings of the coil which
are sent to the plugs via the distributor. A magneto is really just a
self-contained system which includes the generator, points, coil, and
distributor all in one handy package. I can post a schematic if you'd
like, since I took a test on aircraft ignition systems a few weeks ago
and still have textbooks and stuff laying around (I'm about 6 months
away from having my A&P mechanic's certificate).
> I have never seen a magneto system that uses any sort of advance. but
> this could be acheived relatively easily. All that is needed is to
> mount the pick up on a plate that rotates around the crank shaft. Then,
> all that would be required is a means of moving this plate a few
> degrees when it was desired. Like I said, I have not seen this sort of
> thing, but it shouldn't be impossible to acheive.
It isn't done simply because mags are mostly used in aircraft these days,
which run for hours on end in the same narrow range of RPM and power
output (the same could be said for your mower). The timing can be fixed
at the optimal setting for these conditions, so there isn't much to be
gained by a variable advance mechanism and it would be just one more
thing to fail.
> I think the largest
> problem to solve in the magneto system is the length of time it takes
> to build enough charge to give a powerful spark. I am not positive,
> but I think part of the reason that airplanes have two magnetos is
> that they are on half cycle duty cycle. That is, they fire alternately
> so that they get a rest between firings. Admittedly, that is a SWAG,
> but I thought I would throw it out anyway.
That is incorrect. Both mags fire each cylinder simultaneously (two
plugs per cylinder).
> Airplanes could use two
> just so that there is a back up system in case the primary ignitin
> system fails. A plane, after all, has considerable safety problems
> when the motor quits running, all that happens to a car is that it
> rolls to the side of the road.
The most often quoted reason for two mags is reliability as you mention,
but that is followed with "oh by the way" the engine won't run right or
make anywhere near full power on just one mag. This is because aircraft
engines typically have huge pistons and the flame front won't propogate
correctly without both spark plugs firing. In most cases the loss of a
mag should allow you to limp home but if you are heavy or at a high
density altitude that is by no means certain. It may mean that you just
have more time to choose the crash site.
> An automobile has space constraints that would prohibit the
> application of a magneto,
You should try working on an airplane sometime. 8^P
> and one would still need the alternator to
> power the other electrical systems on board. It makes more sense from
> a design perspective to use the charging system to set up the
> electrical pulse needed to get the spark, then use a timing system to
> provide the spark at the correct instant.
I am in total agreement. The only reason that mags are any good at all
on an aircraft is because we use two of them. Work is underway to
switch to more modern equipment, but the aviation world is extremely
resistant to change for a number of reasons. About the only place
modern ignition is seen in any significant numbers (significant being a
relative term) is in the experimental/homebuilt world. And a lot of
those guys retain one of their mags just for redundancy.
We now return you to your regularly scheduled Jeep newsgroup. 8^)
----------------------------------------------------
Del Rawlins- del@_kills_spammers_rawlinsbrothers.org
Remove _kills_spammers_ to reply via email.
Unofficial Bearhawk FAQ website:
http://www.rawlinsbrothers.org/bhfaq/
12-01-2003, 10:03 PM
#48
Guest
Posts: n/a
Re: Magneto
On 01 Dec 2003 01:02 PM, CRWLR posted the following:
> My lawn mower has a magneto and has no battery or alternator. The
> magneto replaces the ignition system, not the charging system. It also
> is a magnetic device not a points-based device as another poster
> suggested -- perhaps the powerful magnet is the basis for the name,
> magneto. The large magnet whirling around the pick up is what creates
> the electrical pulse needed for the ignition, not opening and closing
> points.
That's the point. If your lawnmower had an automotive type ignition
system, it would need a battery and alternator or generator to run. The
magneto doesn't replace the battery or alternator for engine starting or
running accessories, but it does eliminate the need for a charging
system with regard to the ignition. An airplane can suffer a total
electrical system failure (as I did one day) and the engine keeps firing
just fine.
The magneto does use points and the timing of the points is critical to
the operation of the mag. All the magnet does is generate electrical
current, and the pulse is generated by the opening of the points which
interrupts current in the primary windings of the coil. This causes the
magnetic field which was induced in the primary windings to collapse,
which in turn induces a high voltage current in the secondary windings.
It is the current induced in the secondary windings of the coil which
are sent to the plugs via the distributor. A magneto is really just a
self-contained system which includes the generator, points, coil, and
distributor all in one handy package. I can post a schematic if you'd
like, since I took a test on aircraft ignition systems a few weeks ago
and still have textbooks and stuff laying around (I'm about 6 months
away from having my A&P mechanic's certificate).
> I have never seen a magneto system that uses any sort of advance. but
> this could be acheived relatively easily. All that is needed is to
> mount the pick up on a plate that rotates around the crank shaft. Then,
> all that would be required is a means of moving this plate a few
> degrees when it was desired. Like I said, I have not seen this sort of
> thing, but it shouldn't be impossible to acheive.
It isn't done simply because mags are mostly used in aircraft these days,
which run for hours on end in the same narrow range of RPM and power
output (the same could be said for your mower). The timing can be fixed
at the optimal setting for these conditions, so there isn't much to be
gained by a variable advance mechanism and it would be just one more
thing to fail.
> I think the largest
> problem to solve in the magneto system is the length of time it takes
> to build enough charge to give a powerful spark. I am not positive,
> but I think part of the reason that airplanes have two magnetos is
> that they are on half cycle duty cycle. That is, they fire alternately
> so that they get a rest between firings. Admittedly, that is a SWAG,
> but I thought I would throw it out anyway.
That is incorrect. Both mags fire each cylinder simultaneously (two
plugs per cylinder).
> Airplanes could use two
> just so that there is a back up system in case the primary ignitin
> system fails. A plane, after all, has considerable safety problems
> when the motor quits running, all that happens to a car is that it
> rolls to the side of the road.
The most often quoted reason for two mags is reliability as you mention,
but that is followed with "oh by the way" the engine won't run right or
make anywhere near full power on just one mag. This is because aircraft
engines typically have huge pistons and the flame front won't propogate
correctly without both spark plugs firing. In most cases the loss of a
mag should allow you to limp home but if you are heavy or at a high
density altitude that is by no means certain. It may mean that you just
have more time to choose the crash site.
> An automobile has space constraints that would prohibit the
> application of a magneto,
You should try working on an airplane sometime. 8^P
> and one would still need the alternator to
> power the other electrical systems on board. It makes more sense from
> a design perspective to use the charging system to set up the
> electrical pulse needed to get the spark, then use a timing system to
> provide the spark at the correct instant.
I am in total agreement. The only reason that mags are any good at all
on an aircraft is because we use two of them. Work is underway to
switch to more modern equipment, but the aviation world is extremely
resistant to change for a number of reasons. About the only place
modern ignition is seen in any significant numbers (significant being a
relative term) is in the experimental/homebuilt world. And a lot of
those guys retain one of their mags just for redundancy.
We now return you to your regularly scheduled Jeep newsgroup. 8^)
----------------------------------------------------
Del Rawlins- del@_kills_spammers_rawlinsbrothers.org
Remove _kills_spammers_ to reply via email.
Unofficial Bearhawk FAQ website:
http://www.rawlinsbrothers.org/bhfaq/
> My lawn mower has a magneto and has no battery or alternator. The
> magneto replaces the ignition system, not the charging system. It also
> is a magnetic device not a points-based device as another poster
> suggested -- perhaps the powerful magnet is the basis for the name,
> magneto. The large magnet whirling around the pick up is what creates
> the electrical pulse needed for the ignition, not opening and closing
> points.
That's the point. If your lawnmower had an automotive type ignition
system, it would need a battery and alternator or generator to run. The
magneto doesn't replace the battery or alternator for engine starting or
running accessories, but it does eliminate the need for a charging
system with regard to the ignition. An airplane can suffer a total
electrical system failure (as I did one day) and the engine keeps firing
just fine.
The magneto does use points and the timing of the points is critical to
the operation of the mag. All the magnet does is generate electrical
current, and the pulse is generated by the opening of the points which
interrupts current in the primary windings of the coil. This causes the
magnetic field which was induced in the primary windings to collapse,
which in turn induces a high voltage current in the secondary windings.
It is the current induced in the secondary windings of the coil which
are sent to the plugs via the distributor. A magneto is really just a
self-contained system which includes the generator, points, coil, and
distributor all in one handy package. I can post a schematic if you'd
like, since I took a test on aircraft ignition systems a few weeks ago
and still have textbooks and stuff laying around (I'm about 6 months
away from having my A&P mechanic's certificate).
> I have never seen a magneto system that uses any sort of advance. but
> this could be acheived relatively easily. All that is needed is to
> mount the pick up on a plate that rotates around the crank shaft. Then,
> all that would be required is a means of moving this plate a few
> degrees when it was desired. Like I said, I have not seen this sort of
> thing, but it shouldn't be impossible to acheive.
It isn't done simply because mags are mostly used in aircraft these days,
which run for hours on end in the same narrow range of RPM and power
output (the same could be said for your mower). The timing can be fixed
at the optimal setting for these conditions, so there isn't much to be
gained by a variable advance mechanism and it would be just one more
thing to fail.
> I think the largest
> problem to solve in the magneto system is the length of time it takes
> to build enough charge to give a powerful spark. I am not positive,
> but I think part of the reason that airplanes have two magnetos is
> that they are on half cycle duty cycle. That is, they fire alternately
> so that they get a rest between firings. Admittedly, that is a SWAG,
> but I thought I would throw it out anyway.
That is incorrect. Both mags fire each cylinder simultaneously (two
plugs per cylinder).
> Airplanes could use two
> just so that there is a back up system in case the primary ignitin
> system fails. A plane, after all, has considerable safety problems
> when the motor quits running, all that happens to a car is that it
> rolls to the side of the road.
The most often quoted reason for two mags is reliability as you mention,
but that is followed with "oh by the way" the engine won't run right or
make anywhere near full power on just one mag. This is because aircraft
engines typically have huge pistons and the flame front won't propogate
correctly without both spark plugs firing. In most cases the loss of a
mag should allow you to limp home but if you are heavy or at a high
density altitude that is by no means certain. It may mean that you just
have more time to choose the crash site.
> An automobile has space constraints that would prohibit the
> application of a magneto,
You should try working on an airplane sometime. 8^P
> and one would still need the alternator to
> power the other electrical systems on board. It makes more sense from
> a design perspective to use the charging system to set up the
> electrical pulse needed to get the spark, then use a timing system to
> provide the spark at the correct instant.
I am in total agreement. The only reason that mags are any good at all
on an aircraft is because we use two of them. Work is underway to
switch to more modern equipment, but the aviation world is extremely
resistant to change for a number of reasons. About the only place
modern ignition is seen in any significant numbers (significant being a
relative term) is in the experimental/homebuilt world. And a lot of
those guys retain one of their mags just for redundancy.
We now return you to your regularly scheduled Jeep newsgroup. 8^)
----------------------------------------------------
Del Rawlins- del@_kills_spammers_rawlinsbrothers.org
Remove _kills_spammers_ to reply via email.
Unofficial Bearhawk FAQ website:
http://www.rawlinsbrothers.org/bhfaq/
12-01-2003, 10:03 PM
#49
Guest
Posts: n/a
Re: Magneto
On 01 Dec 2003 01:02 PM, CRWLR posted the following:
> My lawn mower has a magneto and has no battery or alternator. The
> magneto replaces the ignition system, not the charging system. It also
> is a magnetic device not a points-based device as another poster
> suggested -- perhaps the powerful magnet is the basis for the name,
> magneto. The large magnet whirling around the pick up is what creates
> the electrical pulse needed for the ignition, not opening and closing
> points.
That's the point. If your lawnmower had an automotive type ignition
system, it would need a battery and alternator or generator to run. The
magneto doesn't replace the battery or alternator for engine starting or
running accessories, but it does eliminate the need for a charging
system with regard to the ignition. An airplane can suffer a total
electrical system failure (as I did one day) and the engine keeps firing
just fine.
The magneto does use points and the timing of the points is critical to
the operation of the mag. All the magnet does is generate electrical
current, and the pulse is generated by the opening of the points which
interrupts current in the primary windings of the coil. This causes the
magnetic field which was induced in the primary windings to collapse,
which in turn induces a high voltage current in the secondary windings.
It is the current induced in the secondary windings of the coil which
are sent to the plugs via the distributor. A magneto is really just a
self-contained system which includes the generator, points, coil, and
distributor all in one handy package. I can post a schematic if you'd
like, since I took a test on aircraft ignition systems a few weeks ago
and still have textbooks and stuff laying around (I'm about 6 months
away from having my A&P mechanic's certificate).
> I have never seen a magneto system that uses any sort of advance. but
> this could be acheived relatively easily. All that is needed is to
> mount the pick up on a plate that rotates around the crank shaft. Then,
> all that would be required is a means of moving this plate a few
> degrees when it was desired. Like I said, I have not seen this sort of
> thing, but it shouldn't be impossible to acheive.
It isn't done simply because mags are mostly used in aircraft these days,
which run for hours on end in the same narrow range of RPM and power
output (the same could be said for your mower). The timing can be fixed
at the optimal setting for these conditions, so there isn't much to be
gained by a variable advance mechanism and it would be just one more
thing to fail.
> I think the largest
> problem to solve in the magneto system is the length of time it takes
> to build enough charge to give a powerful spark. I am not positive,
> but I think part of the reason that airplanes have two magnetos is
> that they are on half cycle duty cycle. That is, they fire alternately
> so that they get a rest between firings. Admittedly, that is a SWAG,
> but I thought I would throw it out anyway.
That is incorrect. Both mags fire each cylinder simultaneously (two
plugs per cylinder).
> Airplanes could use two
> just so that there is a back up system in case the primary ignitin
> system fails. A plane, after all, has considerable safety problems
> when the motor quits running, all that happens to a car is that it
> rolls to the side of the road.
The most often quoted reason for two mags is reliability as you mention,
but that is followed with "oh by the way" the engine won't run right or
make anywhere near full power on just one mag. This is because aircraft
engines typically have huge pistons and the flame front won't propogate
correctly without both spark plugs firing. In most cases the loss of a
mag should allow you to limp home but if you are heavy or at a high
density altitude that is by no means certain. It may mean that you just
have more time to choose the crash site.
> An automobile has space constraints that would prohibit the
> application of a magneto,
You should try working on an airplane sometime. 8^P
> and one would still need the alternator to
> power the other electrical systems on board. It makes more sense from
> a design perspective to use the charging system to set up the
> electrical pulse needed to get the spark, then use a timing system to
> provide the spark at the correct instant.
I am in total agreement. The only reason that mags are any good at all
on an aircraft is because we use two of them. Work is underway to
switch to more modern equipment, but the aviation world is extremely
resistant to change for a number of reasons. About the only place
modern ignition is seen in any significant numbers (significant being a
relative term) is in the experimental/homebuilt world. And a lot of
those guys retain one of their mags just for redundancy.
We now return you to your regularly scheduled Jeep newsgroup. 8^)
----------------------------------------------------
Del Rawlins- del@_kills_spammers_rawlinsbrothers.org
Remove _kills_spammers_ to reply via email.
Unofficial Bearhawk FAQ website:
http://www.rawlinsbrothers.org/bhfaq/
> My lawn mower has a magneto and has no battery or alternator. The
> magneto replaces the ignition system, not the charging system. It also
> is a magnetic device not a points-based device as another poster
> suggested -- perhaps the powerful magnet is the basis for the name,
> magneto. The large magnet whirling around the pick up is what creates
> the electrical pulse needed for the ignition, not opening and closing
> points.
That's the point. If your lawnmower had an automotive type ignition
system, it would need a battery and alternator or generator to run. The
magneto doesn't replace the battery or alternator for engine starting or
running accessories, but it does eliminate the need for a charging
system with regard to the ignition. An airplane can suffer a total
electrical system failure (as I did one day) and the engine keeps firing
just fine.
The magneto does use points and the timing of the points is critical to
the operation of the mag. All the magnet does is generate electrical
current, and the pulse is generated by the opening of the points which
interrupts current in the primary windings of the coil. This causes the
magnetic field which was induced in the primary windings to collapse,
which in turn induces a high voltage current in the secondary windings.
It is the current induced in the secondary windings of the coil which
are sent to the plugs via the distributor. A magneto is really just a
self-contained system which includes the generator, points, coil, and
distributor all in one handy package. I can post a schematic if you'd
like, since I took a test on aircraft ignition systems a few weeks ago
and still have textbooks and stuff laying around (I'm about 6 months
away from having my A&P mechanic's certificate).
> I have never seen a magneto system that uses any sort of advance. but
> this could be acheived relatively easily. All that is needed is to
> mount the pick up on a plate that rotates around the crank shaft. Then,
> all that would be required is a means of moving this plate a few
> degrees when it was desired. Like I said, I have not seen this sort of
> thing, but it shouldn't be impossible to acheive.
It isn't done simply because mags are mostly used in aircraft these days,
which run for hours on end in the same narrow range of RPM and power
output (the same could be said for your mower). The timing can be fixed
at the optimal setting for these conditions, so there isn't much to be
gained by a variable advance mechanism and it would be just one more
thing to fail.
> I think the largest
> problem to solve in the magneto system is the length of time it takes
> to build enough charge to give a powerful spark. I am not positive,
> but I think part of the reason that airplanes have two magnetos is
> that they are on half cycle duty cycle. That is, they fire alternately
> so that they get a rest between firings. Admittedly, that is a SWAG,
> but I thought I would throw it out anyway.
That is incorrect. Both mags fire each cylinder simultaneously (two
plugs per cylinder).
> Airplanes could use two
> just so that there is a back up system in case the primary ignitin
> system fails. A plane, after all, has considerable safety problems
> when the motor quits running, all that happens to a car is that it
> rolls to the side of the road.
The most often quoted reason for two mags is reliability as you mention,
but that is followed with "oh by the way" the engine won't run right or
make anywhere near full power on just one mag. This is because aircraft
engines typically have huge pistons and the flame front won't propogate
correctly without both spark plugs firing. In most cases the loss of a
mag should allow you to limp home but if you are heavy or at a high
density altitude that is by no means certain. It may mean that you just
have more time to choose the crash site.
> An automobile has space constraints that would prohibit the
> application of a magneto,
You should try working on an airplane sometime. 8^P
> and one would still need the alternator to
> power the other electrical systems on board. It makes more sense from
> a design perspective to use the charging system to set up the
> electrical pulse needed to get the spark, then use a timing system to
> provide the spark at the correct instant.
I am in total agreement. The only reason that mags are any good at all
on an aircraft is because we use two of them. Work is underway to
switch to more modern equipment, but the aviation world is extremely
resistant to change for a number of reasons. About the only place
modern ignition is seen in any significant numbers (significant being a
relative term) is in the experimental/homebuilt world. And a lot of
those guys retain one of their mags just for redundancy.
We now return you to your regularly scheduled Jeep newsgroup. 8^)
----------------------------------------------------
Del Rawlins- del@_kills_spammers_rawlinsbrothers.org
Remove _kills_spammers_ to reply via email.
Unofficial Bearhawk FAQ website:
http://www.rawlinsbrothers.org/bhfaq/
12-01-2003, 10:10 PM
#50
Guest
Posts: n/a
Re: Magneto
On 01 Dec 2003 02:19 PM, Lon Stowell posted the following:
> Approximately 12/1/03 13:44, CRWLR uttered for posterity:
>
>> I think that if a magneto ignition was suitable for use on an
>> automobile, then we would still be using them today instead of having
>> devised a means of getting rid of them 70-some-odd years ago.
>
> Judson magnetos were still popular as a more reliable and
> higher performance replacement for the stock ignition in
> British sports cars a mere 35-40 years ago. Whether this
> is evidence of merit for the magneto or a comment on
> British electrics may be a matter of personal opinion.
As the owner of a 1959 MGA, I am inclined to believe the latter. When I
finally get around to restoring my car, the Lucas distributor will be
fitted with one of the available drop-in electronic ignition modules.
That way, it will look stock and run better.
> As soon as good high energy ignition systems from the
> manufacturers hit the streets, magnetos pretty much
> disappeared, only to be remembered by aging pilots and
> old farts.
Some of us are young farts, although a look in the mirror is starting to
show less hair than is supposed to be there. I think my '73 chev was
one of the last pickups that GM made that still used points. I
converted it to HEI about 3 years ago and it now runs better than it has
in at least 15 years, and it actually passed its first ever emmissions
inspection this past summer (that shocked the hell out of me). The gas
mileage still sucks though.
----------------------------------------------------
Del Rawlins- del@_kills_spammers_rawlinsbrothers.org
Remove _kills_spammers_ to reply via email.
Unofficial Bearhawk FAQ website:
http://www.rawlinsbrothers.org/bhfaq/
> Approximately 12/1/03 13:44, CRWLR uttered for posterity:
>
>> I think that if a magneto ignition was suitable for use on an
>> automobile, then we would still be using them today instead of having
>> devised a means of getting rid of them 70-some-odd years ago.
>
> Judson magnetos were still popular as a more reliable and
> higher performance replacement for the stock ignition in
> British sports cars a mere 35-40 years ago. Whether this
> is evidence of merit for the magneto or a comment on
> British electrics may be a matter of personal opinion.
As the owner of a 1959 MGA, I am inclined to believe the latter. When I
finally get around to restoring my car, the Lucas distributor will be
fitted with one of the available drop-in electronic ignition modules.
That way, it will look stock and run better.
> As soon as good high energy ignition systems from the
> manufacturers hit the streets, magnetos pretty much
> disappeared, only to be remembered by aging pilots and
> old farts.
Some of us are young farts, although a look in the mirror is starting to
show less hair than is supposed to be there. I think my '73 chev was
one of the last pickups that GM made that still used points. I
converted it to HEI about 3 years ago and it now runs better than it has
in at least 15 years, and it actually passed its first ever emmissions
inspection this past summer (that shocked the hell out of me). The gas
mileage still sucks though.
----------------------------------------------------
Del Rawlins- del@_kills_spammers_rawlinsbrothers.org
Remove _kills_spammers_ to reply via email.
Unofficial Bearhawk FAQ website:
http://www.rawlinsbrothers.org/bhfaq/