Magneto
#61
Guest
Posts: n/a
Re: Magneto
On small bikes, the magneto also powers up the lights and horn. The
headlight dims radically at idle and you can pop bulbs at high speeds if
the engine is 'tweaked' to give more than stock rpm.
Anyone running a magneto system carries extra bulbs, the power with rpm
changes cook them fast, same for spark plugs ant the plug wire caps.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
CRWLR wrote:
>
> 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.
>
> 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. 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.
> 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.
>
> An automobile has space constraints that would prohibit the application of a
> magneto, 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.
>
> "Del Rawlins" <del@_kills_spammers_rawlinsbrothers.org> wrote in message
> news:20031129225538908-0900@news.newsguy.com...
> > On 29 Nov 2003 07:17 PM, c posted the following:
> > >
> > >
> > > "Kevin" <Kevin@el.net> wrote in message
> > > news:3Mdyb.254542$mZ5.1886878@attbi_s54...
> > >> Is a magneto ignition system more reliable than the alternators used
> > >> on cars? Can you use mags on a jeep ?
> > >>
> > >
> > > A magneto doesn't replace an alternator, it replaces the distributor.
> > > Even with a magneto ignition, you'll still need your charging system.
> > > Magnetos use points. they are not as reliable as an electronic
> > > ignition.
> >
> > From the standpoint of ignition, the magneto does replace the alternator
> > and battery, since the mag generates its own power. You will
> > undoubtedly still want the alternator and battery to get the thing
> > started and to run electrical accessories. As for reliability, the
> > magneto doesn't have to be more reliable than the electronic ignition,
> > it only has to be more reliable than the battery and its charging system.
> > Other than lack of self-generating ability, the electronic ignition is
> > better in every way.
> >
> > > Also, most of them don't have a mechanical advance, and none
> > > I know of has a vacuum advance. This means your timing will not be
> > > optimized for light load conditions with the vacuum advance. You can
> > > use a magneto on anything they make magnetos for.
> >
> > This is true.
> >
> > ----------------------------------------------------
> > Del Rawlins- del@_kills_spammers_rawlinsbrothers.org
> > Remove _kills_spammers_ to reply via email.
> > Unofficial Bearhawk FAQ website:
> > http://www.rawlinsbrothers.org/bhfaq/
headlight dims radically at idle and you can pop bulbs at high speeds if
the engine is 'tweaked' to give more than stock rpm.
Anyone running a magneto system carries extra bulbs, the power with rpm
changes cook them fast, same for spark plugs ant the plug wire caps.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
CRWLR wrote:
>
> 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.
>
> 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. 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.
> 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.
>
> An automobile has space constraints that would prohibit the application of a
> magneto, 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.
>
> "Del Rawlins" <del@_kills_spammers_rawlinsbrothers.org> wrote in message
> news:20031129225538908-0900@news.newsguy.com...
> > On 29 Nov 2003 07:17 PM, c posted the following:
> > >
> > >
> > > "Kevin" <Kevin@el.net> wrote in message
> > > news:3Mdyb.254542$mZ5.1886878@attbi_s54...
> > >> Is a magneto ignition system more reliable than the alternators used
> > >> on cars? Can you use mags on a jeep ?
> > >>
> > >
> > > A magneto doesn't replace an alternator, it replaces the distributor.
> > > Even with a magneto ignition, you'll still need your charging system.
> > > Magnetos use points. they are not as reliable as an electronic
> > > ignition.
> >
> > From the standpoint of ignition, the magneto does replace the alternator
> > and battery, since the mag generates its own power. You will
> > undoubtedly still want the alternator and battery to get the thing
> > started and to run electrical accessories. As for reliability, the
> > magneto doesn't have to be more reliable than the electronic ignition,
> > it only has to be more reliable than the battery and its charging system.
> > Other than lack of self-generating ability, the electronic ignition is
> > better in every way.
> >
> > > Also, most of them don't have a mechanical advance, and none
> > > I know of has a vacuum advance. This means your timing will not be
> > > optimized for light load conditions with the vacuum advance. You can
> > > use a magneto on anything they make magnetos for.
> >
> > This is true.
> >
> > ----------------------------------------------------
> > Del Rawlins- del@_kills_spammers_rawlinsbrothers.org
> > Remove _kills_spammers_ to reply via email.
> > Unofficial Bearhawk FAQ website:
> > http://www.rawlinsbrothers.org/bhfaq/
#62
Guest
Posts: n/a
Re: Magneto
I have an old BSA magneto driven scooter. It is neat.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Paul Calman wrote:
>
> I can still buy a BSA motorcycle timing cover made to run carry a mag for
> racing, but modern electronics have made that more of a nostalgia piece.
> I used to work for the guy who got all of the mags from the Harrah's
> Collection auction. The magnets would go bad unless stored in the correct
> position, and they all had points. Some had mechanical advances connected to
> a lever in the sterring wheel.
> We used to zap unsuspecting visitors often.
>
> --
> Paul Calman, Hathaway Pines, California
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Paul Calman wrote:
>
> I can still buy a BSA motorcycle timing cover made to run carry a mag for
> racing, but modern electronics have made that more of a nostalgia piece.
> I used to work for the guy who got all of the mags from the Harrah's
> Collection auction. The magnets would go bad unless stored in the correct
> position, and they all had points. Some had mechanical advances connected to
> a lever in the sterring wheel.
> We used to zap unsuspecting visitors often.
>
> --
> Paul Calman, Hathaway Pines, California
#63
Guest
Posts: n/a
Re: Magneto
I have an old BSA magneto driven scooter. It is neat.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Paul Calman wrote:
>
> I can still buy a BSA motorcycle timing cover made to run carry a mag for
> racing, but modern electronics have made that more of a nostalgia piece.
> I used to work for the guy who got all of the mags from the Harrah's
> Collection auction. The magnets would go bad unless stored in the correct
> position, and they all had points. Some had mechanical advances connected to
> a lever in the sterring wheel.
> We used to zap unsuspecting visitors often.
>
> --
> Paul Calman, Hathaway Pines, California
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Paul Calman wrote:
>
> I can still buy a BSA motorcycle timing cover made to run carry a mag for
> racing, but modern electronics have made that more of a nostalgia piece.
> I used to work for the guy who got all of the mags from the Harrah's
> Collection auction. The magnets would go bad unless stored in the correct
> position, and they all had points. Some had mechanical advances connected to
> a lever in the sterring wheel.
> We used to zap unsuspecting visitors often.
>
> --
> Paul Calman, Hathaway Pines, California
#64
Guest
Posts: n/a
Re: Magneto
I have an old BSA magneto driven scooter. It is neat.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Paul Calman wrote:
>
> I can still buy a BSA motorcycle timing cover made to run carry a mag for
> racing, but modern electronics have made that more of a nostalgia piece.
> I used to work for the guy who got all of the mags from the Harrah's
> Collection auction. The magnets would go bad unless stored in the correct
> position, and they all had points. Some had mechanical advances connected to
> a lever in the sterring wheel.
> We used to zap unsuspecting visitors often.
>
> --
> Paul Calman, Hathaway Pines, California
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Paul Calman wrote:
>
> I can still buy a BSA motorcycle timing cover made to run carry a mag for
> racing, but modern electronics have made that more of a nostalgia piece.
> I used to work for the guy who got all of the mags from the Harrah's
> Collection auction. The magnets would go bad unless stored in the correct
> position, and they all had points. Some had mechanical advances connected to
> a lever in the sterring wheel.
> We used to zap unsuspecting visitors often.
>
> --
> Paul Calman, Hathaway Pines, California
#65
Guest
Posts: n/a
Re: Magneto
Your Grandfather adjusted the vibrating points on the coil box that
fired each individual spark plug, from inside the cab as he drove:
http://www.modelt.ca/13T-fs.html
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/
CRWLR wrote:
>
> I can go along with that. The magneto is the charging system (battery and
> alternator) and ignition system, all rolled into one. It that respect, it
> replaces the battery and alternator.
>
> The magneto systems that I have played with were very rudementry, and they
> were simply an induction coil thingie that was set off by the large magnet
> flying by that was embedded into a huge chunk of metal. I can see where an
> aircraft might use a considerably more sophisticated system that actually
> employed points and other hardware.
>
> Do you have a manual control on the magneto that you can trim the timing for
> optimal performance? For instance, we once had a manual choke on our
> carburators that Grandpa had to play with to get the motor to even run. I
> seem to remember that Grandpa's first car might have had a magneto to adjust
> too. It would have been a similar sort of mechanical thingie as the choke,
> but maybe it was mounted in the center of the steering wheel.
>
> I would think that a similar sort of thing might be useful to trim the mags
> for different kinds of engine operation. I understand that the plane engine
> will run for hours on end at a fixed speed, but I was thinking that taxiing
> at 2500 rpm might demand a different mag setting than sustained flight at
> 80% of capacity. I assume that crusing speed is somewhere around 80%, and
> that 100% would be reserved for take off and maybe climbing steeply.
>
> Doesn't the magneto add a ---- load of weight to the crankshaft? I always
> thought that my lawnmower took so long to shut down was because the flywheel
> (where the magneto's magnets are located) was so damn heavy. Of course, the
> single jug will take a long time to stop the motor too, where a multi-jug
> motor will have more opportunities to arrest the speeding flywheel with
> additional compression strokes ...
fired each individual spark plug, from inside the cab as he drove:
http://www.modelt.ca/13T-fs.html
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/
CRWLR wrote:
>
> I can go along with that. The magneto is the charging system (battery and
> alternator) and ignition system, all rolled into one. It that respect, it
> replaces the battery and alternator.
>
> The magneto systems that I have played with were very rudementry, and they
> were simply an induction coil thingie that was set off by the large magnet
> flying by that was embedded into a huge chunk of metal. I can see where an
> aircraft might use a considerably more sophisticated system that actually
> employed points and other hardware.
>
> Do you have a manual control on the magneto that you can trim the timing for
> optimal performance? For instance, we once had a manual choke on our
> carburators that Grandpa had to play with to get the motor to even run. I
> seem to remember that Grandpa's first car might have had a magneto to adjust
> too. It would have been a similar sort of mechanical thingie as the choke,
> but maybe it was mounted in the center of the steering wheel.
>
> I would think that a similar sort of thing might be useful to trim the mags
> for different kinds of engine operation. I understand that the plane engine
> will run for hours on end at a fixed speed, but I was thinking that taxiing
> at 2500 rpm might demand a different mag setting than sustained flight at
> 80% of capacity. I assume that crusing speed is somewhere around 80%, and
> that 100% would be reserved for take off and maybe climbing steeply.
>
> Doesn't the magneto add a ---- load of weight to the crankshaft? I always
> thought that my lawnmower took so long to shut down was because the flywheel
> (where the magneto's magnets are located) was so damn heavy. Of course, the
> single jug will take a long time to stop the motor too, where a multi-jug
> motor will have more opportunities to arrest the speeding flywheel with
> additional compression strokes ...
#66
Guest
Posts: n/a
Re: Magneto
Your Grandfather adjusted the vibrating points on the coil box that
fired each individual spark plug, from inside the cab as he drove:
http://www.modelt.ca/13T-fs.html
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/
CRWLR wrote:
>
> I can go along with that. The magneto is the charging system (battery and
> alternator) and ignition system, all rolled into one. It that respect, it
> replaces the battery and alternator.
>
> The magneto systems that I have played with were very rudementry, and they
> were simply an induction coil thingie that was set off by the large magnet
> flying by that was embedded into a huge chunk of metal. I can see where an
> aircraft might use a considerably more sophisticated system that actually
> employed points and other hardware.
>
> Do you have a manual control on the magneto that you can trim the timing for
> optimal performance? For instance, we once had a manual choke on our
> carburators that Grandpa had to play with to get the motor to even run. I
> seem to remember that Grandpa's first car might have had a magneto to adjust
> too. It would have been a similar sort of mechanical thingie as the choke,
> but maybe it was mounted in the center of the steering wheel.
>
> I would think that a similar sort of thing might be useful to trim the mags
> for different kinds of engine operation. I understand that the plane engine
> will run for hours on end at a fixed speed, but I was thinking that taxiing
> at 2500 rpm might demand a different mag setting than sustained flight at
> 80% of capacity. I assume that crusing speed is somewhere around 80%, and
> that 100% would be reserved for take off and maybe climbing steeply.
>
> Doesn't the magneto add a ---- load of weight to the crankshaft? I always
> thought that my lawnmower took so long to shut down was because the flywheel
> (where the magneto's magnets are located) was so damn heavy. Of course, the
> single jug will take a long time to stop the motor too, where a multi-jug
> motor will have more opportunities to arrest the speeding flywheel with
> additional compression strokes ...
fired each individual spark plug, from inside the cab as he drove:
http://www.modelt.ca/13T-fs.html
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/
CRWLR wrote:
>
> I can go along with that. The magneto is the charging system (battery and
> alternator) and ignition system, all rolled into one. It that respect, it
> replaces the battery and alternator.
>
> The magneto systems that I have played with were very rudementry, and they
> were simply an induction coil thingie that was set off by the large magnet
> flying by that was embedded into a huge chunk of metal. I can see where an
> aircraft might use a considerably more sophisticated system that actually
> employed points and other hardware.
>
> Do you have a manual control on the magneto that you can trim the timing for
> optimal performance? For instance, we once had a manual choke on our
> carburators that Grandpa had to play with to get the motor to even run. I
> seem to remember that Grandpa's first car might have had a magneto to adjust
> too. It would have been a similar sort of mechanical thingie as the choke,
> but maybe it was mounted in the center of the steering wheel.
>
> I would think that a similar sort of thing might be useful to trim the mags
> for different kinds of engine operation. I understand that the plane engine
> will run for hours on end at a fixed speed, but I was thinking that taxiing
> at 2500 rpm might demand a different mag setting than sustained flight at
> 80% of capacity. I assume that crusing speed is somewhere around 80%, and
> that 100% would be reserved for take off and maybe climbing steeply.
>
> Doesn't the magneto add a ---- load of weight to the crankshaft? I always
> thought that my lawnmower took so long to shut down was because the flywheel
> (where the magneto's magnets are located) was so damn heavy. Of course, the
> single jug will take a long time to stop the motor too, where a multi-jug
> motor will have more opportunities to arrest the speeding flywheel with
> additional compression strokes ...
#67
Guest
Posts: n/a
Re: Magneto
Your Grandfather adjusted the vibrating points on the coil box that
fired each individual spark plug, from inside the cab as he drove:
http://www.modelt.ca/13T-fs.html
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/
CRWLR wrote:
>
> I can go along with that. The magneto is the charging system (battery and
> alternator) and ignition system, all rolled into one. It that respect, it
> replaces the battery and alternator.
>
> The magneto systems that I have played with were very rudementry, and they
> were simply an induction coil thingie that was set off by the large magnet
> flying by that was embedded into a huge chunk of metal. I can see where an
> aircraft might use a considerably more sophisticated system that actually
> employed points and other hardware.
>
> Do you have a manual control on the magneto that you can trim the timing for
> optimal performance? For instance, we once had a manual choke on our
> carburators that Grandpa had to play with to get the motor to even run. I
> seem to remember that Grandpa's first car might have had a magneto to adjust
> too. It would have been a similar sort of mechanical thingie as the choke,
> but maybe it was mounted in the center of the steering wheel.
>
> I would think that a similar sort of thing might be useful to trim the mags
> for different kinds of engine operation. I understand that the plane engine
> will run for hours on end at a fixed speed, but I was thinking that taxiing
> at 2500 rpm might demand a different mag setting than sustained flight at
> 80% of capacity. I assume that crusing speed is somewhere around 80%, and
> that 100% would be reserved for take off and maybe climbing steeply.
>
> Doesn't the magneto add a ---- load of weight to the crankshaft? I always
> thought that my lawnmower took so long to shut down was because the flywheel
> (where the magneto's magnets are located) was so damn heavy. Of course, the
> single jug will take a long time to stop the motor too, where a multi-jug
> motor will have more opportunities to arrest the speeding flywheel with
> additional compression strokes ...
fired each individual spark plug, from inside the cab as he drove:
http://www.modelt.ca/13T-fs.html
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/
CRWLR wrote:
>
> I can go along with that. The magneto is the charging system (battery and
> alternator) and ignition system, all rolled into one. It that respect, it
> replaces the battery and alternator.
>
> The magneto systems that I have played with were very rudementry, and they
> were simply an induction coil thingie that was set off by the large magnet
> flying by that was embedded into a huge chunk of metal. I can see where an
> aircraft might use a considerably more sophisticated system that actually
> employed points and other hardware.
>
> Do you have a manual control on the magneto that you can trim the timing for
> optimal performance? For instance, we once had a manual choke on our
> carburators that Grandpa had to play with to get the motor to even run. I
> seem to remember that Grandpa's first car might have had a magneto to adjust
> too. It would have been a similar sort of mechanical thingie as the choke,
> but maybe it was mounted in the center of the steering wheel.
>
> I would think that a similar sort of thing might be useful to trim the mags
> for different kinds of engine operation. I understand that the plane engine
> will run for hours on end at a fixed speed, but I was thinking that taxiing
> at 2500 rpm might demand a different mag setting than sustained flight at
> 80% of capacity. I assume that crusing speed is somewhere around 80%, and
> that 100% would be reserved for take off and maybe climbing steeply.
>
> Doesn't the magneto add a ---- load of weight to the crankshaft? I always
> thought that my lawnmower took so long to shut down was because the flywheel
> (where the magneto's magnets are located) was so damn heavy. Of course, the
> single jug will take a long time to stop the motor too, where a multi-jug
> motor will have more opportunities to arrest the speeding flywheel with
> additional compression strokes ...
#68
Guest
Posts: n/a
Re: Magneto
On 02 Dec 2003 01:58 PM, CRWLR posted the following:
> Do you have a manual control on the magneto that you can trim the
> timing for optimal performance? For instance, we once had a manual
> choke on our carburators that Grandpa had to play with to get the
> motor to even run. I seem to remember that Grandpa's first car might
> have had a magneto to adjust too. It would have been a similar sort of
> mechanical thingie as the choke, but maybe it was mounted in the
> center of the steering wheel.
I've had plenty of experience with manual choke but I've never seen any
kind of adjustable timing on a mag, although I have heard here and
elsewhere that such things exist.
> I would think that a similar sort of thing might be useful to trim the
> mags for different kinds of engine operation. I understand that the
> plane engine will run for hours on end at a fixed speed
It all comes down to a basic operating difference between cars and
aircraft. A car (or Jeep) basically runs at fairly low power settings (
like 30 or 40%) most of the time, but needs to put out high power
occasionally, so there is a need for the adjustability. An aircraft
engine will run at 100% power for several minutes during takeoff and
climbout, and then throttle back to something like 75% power for cruise.
It just doesn't need the adjustment. There are gains to be had by a
variable advance but they aren't worth adding moving parts to the mags.
In an electronic ignition it is as easy to include this feature as not,
and that is one of the selling points for those systems, in addition to
the more intense spark.
> but I was
> thinking that taxiing at 2500 rpm might demand a different mag setting
> than sustained flight at 80% of capacity. I assume that crusing speed
> is somewhere around 80%, and that 100% would be reserved for take off
> and maybe climbing steeply.
Taxi? Hell that is up near redline or at least cruise power for most
aircraft engines. Generally we taxi at idle, or the lowest RPM that
will move the airplane since any more than needed forces the pilot to
ride the brakes, which is bad for them (they are not meant for sustained
use). A traditional air-cooled aircraft engine has a huge displacement
for its power output, with huge cylinder bores and a massive
reciprocating assembly turning at a relatively low RPM. This is mainly
imposed by RPM limits on propeller efficiency. Basically when the prop
tips reach the speed of sound the efficiency drops way off, so the
engine design is predicated on keeping the prop at its most efficient
speed of operation.
> Doesn't the magneto add a ---- load of weight to the crankshaft? I
> always thought that my lawnmower took so long to shut down was because
> the flywheel (where the magneto's magnets are located) was so damn
> heavy. Of course, the single jug will take a long time to stop the
> motor too, where a multi-jug motor will have more opportunities to
> arrest the speeding flywheel with additional compression strokes ...
Aircraft magnetos are totally self-contained units housed in their own
cast aluminum cases, which in turn attach to the engine's accessory
drive section and are turned (indirectly) by the crankshaft. They are
held in place by the same sort of clamps that hold the distributor on
your Jeep. They are timed when the engine is not running though, unlike
an automotive system. A mag is no heavier than a typical alternator.
An aircraft doesn't need a flywheel (except in some cases as a place to
put a starter ring gear) since it has that big prop bolted to the
crankshaft.
----------------------------------------------------
Del Rawlins- del@_kills_spammers_rawlinsbrothers.org
Remove _kills_spammers_ to reply via email.
Unofficial Bearhawk FAQ website:
http://www.rawlinsbrothers.org/bhfaq/
> Do you have a manual control on the magneto that you can trim the
> timing for optimal performance? For instance, we once had a manual
> choke on our carburators that Grandpa had to play with to get the
> motor to even run. I seem to remember that Grandpa's first car might
> have had a magneto to adjust too. It would have been a similar sort of
> mechanical thingie as the choke, but maybe it was mounted in the
> center of the steering wheel.
I've had plenty of experience with manual choke but I've never seen any
kind of adjustable timing on a mag, although I have heard here and
elsewhere that such things exist.
> I would think that a similar sort of thing might be useful to trim the
> mags for different kinds of engine operation. I understand that the
> plane engine will run for hours on end at a fixed speed
It all comes down to a basic operating difference between cars and
aircraft. A car (or Jeep) basically runs at fairly low power settings (
like 30 or 40%) most of the time, but needs to put out high power
occasionally, so there is a need for the adjustability. An aircraft
engine will run at 100% power for several minutes during takeoff and
climbout, and then throttle back to something like 75% power for cruise.
It just doesn't need the adjustment. There are gains to be had by a
variable advance but they aren't worth adding moving parts to the mags.
In an electronic ignition it is as easy to include this feature as not,
and that is one of the selling points for those systems, in addition to
the more intense spark.
> but I was
> thinking that taxiing at 2500 rpm might demand a different mag setting
> than sustained flight at 80% of capacity. I assume that crusing speed
> is somewhere around 80%, and that 100% would be reserved for take off
> and maybe climbing steeply.
Taxi? Hell that is up near redline or at least cruise power for most
aircraft engines. Generally we taxi at idle, or the lowest RPM that
will move the airplane since any more than needed forces the pilot to
ride the brakes, which is bad for them (they are not meant for sustained
use). A traditional air-cooled aircraft engine has a huge displacement
for its power output, with huge cylinder bores and a massive
reciprocating assembly turning at a relatively low RPM. This is mainly
imposed by RPM limits on propeller efficiency. Basically when the prop
tips reach the speed of sound the efficiency drops way off, so the
engine design is predicated on keeping the prop at its most efficient
speed of operation.
> Doesn't the magneto add a ---- load of weight to the crankshaft? I
> always thought that my lawnmower took so long to shut down was because
> the flywheel (where the magneto's magnets are located) was so damn
> heavy. Of course, the single jug will take a long time to stop the
> motor too, where a multi-jug motor will have more opportunities to
> arrest the speeding flywheel with additional compression strokes ...
Aircraft magnetos are totally self-contained units housed in their own
cast aluminum cases, which in turn attach to the engine's accessory
drive section and are turned (indirectly) by the crankshaft. They are
held in place by the same sort of clamps that hold the distributor on
your Jeep. They are timed when the engine is not running though, unlike
an automotive system. A mag is no heavier than a typical alternator.
An aircraft doesn't need a flywheel (except in some cases as a place to
put a starter ring gear) since it has that big prop bolted to the
crankshaft.
----------------------------------------------------
Del Rawlins- del@_kills_spammers_rawlinsbrothers.org
Remove _kills_spammers_ to reply via email.
Unofficial Bearhawk FAQ website:
http://www.rawlinsbrothers.org/bhfaq/
#69
Guest
Posts: n/a
Re: Magneto
On 02 Dec 2003 01:58 PM, CRWLR posted the following:
> Do you have a manual control on the magneto that you can trim the
> timing for optimal performance? For instance, we once had a manual
> choke on our carburators that Grandpa had to play with to get the
> motor to even run. I seem to remember that Grandpa's first car might
> have had a magneto to adjust too. It would have been a similar sort of
> mechanical thingie as the choke, but maybe it was mounted in the
> center of the steering wheel.
I've had plenty of experience with manual choke but I've never seen any
kind of adjustable timing on a mag, although I have heard here and
elsewhere that such things exist.
> I would think that a similar sort of thing might be useful to trim the
> mags for different kinds of engine operation. I understand that the
> plane engine will run for hours on end at a fixed speed
It all comes down to a basic operating difference between cars and
aircraft. A car (or Jeep) basically runs at fairly low power settings (
like 30 or 40%) most of the time, but needs to put out high power
occasionally, so there is a need for the adjustability. An aircraft
engine will run at 100% power for several minutes during takeoff and
climbout, and then throttle back to something like 75% power for cruise.
It just doesn't need the adjustment. There are gains to be had by a
variable advance but they aren't worth adding moving parts to the mags.
In an electronic ignition it is as easy to include this feature as not,
and that is one of the selling points for those systems, in addition to
the more intense spark.
> but I was
> thinking that taxiing at 2500 rpm might demand a different mag setting
> than sustained flight at 80% of capacity. I assume that crusing speed
> is somewhere around 80%, and that 100% would be reserved for take off
> and maybe climbing steeply.
Taxi? Hell that is up near redline or at least cruise power for most
aircraft engines. Generally we taxi at idle, or the lowest RPM that
will move the airplane since any more than needed forces the pilot to
ride the brakes, which is bad for them (they are not meant for sustained
use). A traditional air-cooled aircraft engine has a huge displacement
for its power output, with huge cylinder bores and a massive
reciprocating assembly turning at a relatively low RPM. This is mainly
imposed by RPM limits on propeller efficiency. Basically when the prop
tips reach the speed of sound the efficiency drops way off, so the
engine design is predicated on keeping the prop at its most efficient
speed of operation.
> Doesn't the magneto add a ---- load of weight to the crankshaft? I
> always thought that my lawnmower took so long to shut down was because
> the flywheel (where the magneto's magnets are located) was so damn
> heavy. Of course, the single jug will take a long time to stop the
> motor too, where a multi-jug motor will have more opportunities to
> arrest the speeding flywheel with additional compression strokes ...
Aircraft magnetos are totally self-contained units housed in their own
cast aluminum cases, which in turn attach to the engine's accessory
drive section and are turned (indirectly) by the crankshaft. They are
held in place by the same sort of clamps that hold the distributor on
your Jeep. They are timed when the engine is not running though, unlike
an automotive system. A mag is no heavier than a typical alternator.
An aircraft doesn't need a flywheel (except in some cases as a place to
put a starter ring gear) since it has that big prop bolted to the
crankshaft.
----------------------------------------------------
Del Rawlins- del@_kills_spammers_rawlinsbrothers.org
Remove _kills_spammers_ to reply via email.
Unofficial Bearhawk FAQ website:
http://www.rawlinsbrothers.org/bhfaq/
> Do you have a manual control on the magneto that you can trim the
> timing for optimal performance? For instance, we once had a manual
> choke on our carburators that Grandpa had to play with to get the
> motor to even run. I seem to remember that Grandpa's first car might
> have had a magneto to adjust too. It would have been a similar sort of
> mechanical thingie as the choke, but maybe it was mounted in the
> center of the steering wheel.
I've had plenty of experience with manual choke but I've never seen any
kind of adjustable timing on a mag, although I have heard here and
elsewhere that such things exist.
> I would think that a similar sort of thing might be useful to trim the
> mags for different kinds of engine operation. I understand that the
> plane engine will run for hours on end at a fixed speed
It all comes down to a basic operating difference between cars and
aircraft. A car (or Jeep) basically runs at fairly low power settings (
like 30 or 40%) most of the time, but needs to put out high power
occasionally, so there is a need for the adjustability. An aircraft
engine will run at 100% power for several minutes during takeoff and
climbout, and then throttle back to something like 75% power for cruise.
It just doesn't need the adjustment. There are gains to be had by a
variable advance but they aren't worth adding moving parts to the mags.
In an electronic ignition it is as easy to include this feature as not,
and that is one of the selling points for those systems, in addition to
the more intense spark.
> but I was
> thinking that taxiing at 2500 rpm might demand a different mag setting
> than sustained flight at 80% of capacity. I assume that crusing speed
> is somewhere around 80%, and that 100% would be reserved for take off
> and maybe climbing steeply.
Taxi? Hell that is up near redline or at least cruise power for most
aircraft engines. Generally we taxi at idle, or the lowest RPM that
will move the airplane since any more than needed forces the pilot to
ride the brakes, which is bad for them (they are not meant for sustained
use). A traditional air-cooled aircraft engine has a huge displacement
for its power output, with huge cylinder bores and a massive
reciprocating assembly turning at a relatively low RPM. This is mainly
imposed by RPM limits on propeller efficiency. Basically when the prop
tips reach the speed of sound the efficiency drops way off, so the
engine design is predicated on keeping the prop at its most efficient
speed of operation.
> Doesn't the magneto add a ---- load of weight to the crankshaft? I
> always thought that my lawnmower took so long to shut down was because
> the flywheel (where the magneto's magnets are located) was so damn
> heavy. Of course, the single jug will take a long time to stop the
> motor too, where a multi-jug motor will have more opportunities to
> arrest the speeding flywheel with additional compression strokes ...
Aircraft magnetos are totally self-contained units housed in their own
cast aluminum cases, which in turn attach to the engine's accessory
drive section and are turned (indirectly) by the crankshaft. They are
held in place by the same sort of clamps that hold the distributor on
your Jeep. They are timed when the engine is not running though, unlike
an automotive system. A mag is no heavier than a typical alternator.
An aircraft doesn't need a flywheel (except in some cases as a place to
put a starter ring gear) since it has that big prop bolted to the
crankshaft.
----------------------------------------------------
Del Rawlins- del@_kills_spammers_rawlinsbrothers.org
Remove _kills_spammers_ to reply via email.
Unofficial Bearhawk FAQ website:
http://www.rawlinsbrothers.org/bhfaq/
#70
Guest
Posts: n/a
Re: Magneto
On 02 Dec 2003 01:58 PM, CRWLR posted the following:
> Do you have a manual control on the magneto that you can trim the
> timing for optimal performance? For instance, we once had a manual
> choke on our carburators that Grandpa had to play with to get the
> motor to even run. I seem to remember that Grandpa's first car might
> have had a magneto to adjust too. It would have been a similar sort of
> mechanical thingie as the choke, but maybe it was mounted in the
> center of the steering wheel.
I've had plenty of experience with manual choke but I've never seen any
kind of adjustable timing on a mag, although I have heard here and
elsewhere that such things exist.
> I would think that a similar sort of thing might be useful to trim the
> mags for different kinds of engine operation. I understand that the
> plane engine will run for hours on end at a fixed speed
It all comes down to a basic operating difference between cars and
aircraft. A car (or Jeep) basically runs at fairly low power settings (
like 30 or 40%) most of the time, but needs to put out high power
occasionally, so there is a need for the adjustability. An aircraft
engine will run at 100% power for several minutes during takeoff and
climbout, and then throttle back to something like 75% power for cruise.
It just doesn't need the adjustment. There are gains to be had by a
variable advance but they aren't worth adding moving parts to the mags.
In an electronic ignition it is as easy to include this feature as not,
and that is one of the selling points for those systems, in addition to
the more intense spark.
> but I was
> thinking that taxiing at 2500 rpm might demand a different mag setting
> than sustained flight at 80% of capacity. I assume that crusing speed
> is somewhere around 80%, and that 100% would be reserved for take off
> and maybe climbing steeply.
Taxi? Hell that is up near redline or at least cruise power for most
aircraft engines. Generally we taxi at idle, or the lowest RPM that
will move the airplane since any more than needed forces the pilot to
ride the brakes, which is bad for them (they are not meant for sustained
use). A traditional air-cooled aircraft engine has a huge displacement
for its power output, with huge cylinder bores and a massive
reciprocating assembly turning at a relatively low RPM. This is mainly
imposed by RPM limits on propeller efficiency. Basically when the prop
tips reach the speed of sound the efficiency drops way off, so the
engine design is predicated on keeping the prop at its most efficient
speed of operation.
> Doesn't the magneto add a ---- load of weight to the crankshaft? I
> always thought that my lawnmower took so long to shut down was because
> the flywheel (where the magneto's magnets are located) was so damn
> heavy. Of course, the single jug will take a long time to stop the
> motor too, where a multi-jug motor will have more opportunities to
> arrest the speeding flywheel with additional compression strokes ...
Aircraft magnetos are totally self-contained units housed in their own
cast aluminum cases, which in turn attach to the engine's accessory
drive section and are turned (indirectly) by the crankshaft. They are
held in place by the same sort of clamps that hold the distributor on
your Jeep. They are timed when the engine is not running though, unlike
an automotive system. A mag is no heavier than a typical alternator.
An aircraft doesn't need a flywheel (except in some cases as a place to
put a starter ring gear) since it has that big prop bolted to the
crankshaft.
----------------------------------------------------
Del Rawlins- del@_kills_spammers_rawlinsbrothers.org
Remove _kills_spammers_ to reply via email.
Unofficial Bearhawk FAQ website:
http://www.rawlinsbrothers.org/bhfaq/
> Do you have a manual control on the magneto that you can trim the
> timing for optimal performance? For instance, we once had a manual
> choke on our carburators that Grandpa had to play with to get the
> motor to even run. I seem to remember that Grandpa's first car might
> have had a magneto to adjust too. It would have been a similar sort of
> mechanical thingie as the choke, but maybe it was mounted in the
> center of the steering wheel.
I've had plenty of experience with manual choke but I've never seen any
kind of adjustable timing on a mag, although I have heard here and
elsewhere that such things exist.
> I would think that a similar sort of thing might be useful to trim the
> mags for different kinds of engine operation. I understand that the
> plane engine will run for hours on end at a fixed speed
It all comes down to a basic operating difference between cars and
aircraft. A car (or Jeep) basically runs at fairly low power settings (
like 30 or 40%) most of the time, but needs to put out high power
occasionally, so there is a need for the adjustability. An aircraft
engine will run at 100% power for several minutes during takeoff and
climbout, and then throttle back to something like 75% power for cruise.
It just doesn't need the adjustment. There are gains to be had by a
variable advance but they aren't worth adding moving parts to the mags.
In an electronic ignition it is as easy to include this feature as not,
and that is one of the selling points for those systems, in addition to
the more intense spark.
> but I was
> thinking that taxiing at 2500 rpm might demand a different mag setting
> than sustained flight at 80% of capacity. I assume that crusing speed
> is somewhere around 80%, and that 100% would be reserved for take off
> and maybe climbing steeply.
Taxi? Hell that is up near redline or at least cruise power for most
aircraft engines. Generally we taxi at idle, or the lowest RPM that
will move the airplane since any more than needed forces the pilot to
ride the brakes, which is bad for them (they are not meant for sustained
use). A traditional air-cooled aircraft engine has a huge displacement
for its power output, with huge cylinder bores and a massive
reciprocating assembly turning at a relatively low RPM. This is mainly
imposed by RPM limits on propeller efficiency. Basically when the prop
tips reach the speed of sound the efficiency drops way off, so the
engine design is predicated on keeping the prop at its most efficient
speed of operation.
> Doesn't the magneto add a ---- load of weight to the crankshaft? I
> always thought that my lawnmower took so long to shut down was because
> the flywheel (where the magneto's magnets are located) was so damn
> heavy. Of course, the single jug will take a long time to stop the
> motor too, where a multi-jug motor will have more opportunities to
> arrest the speeding flywheel with additional compression strokes ...
Aircraft magnetos are totally self-contained units housed in their own
cast aluminum cases, which in turn attach to the engine's accessory
drive section and are turned (indirectly) by the crankshaft. They are
held in place by the same sort of clamps that hold the distributor on
your Jeep. They are timed when the engine is not running though, unlike
an automotive system. A mag is no heavier than a typical alternator.
An aircraft doesn't need a flywheel (except in some cases as a place to
put a starter ring gear) since it has that big prop bolted to the
crankshaft.
----------------------------------------------------
Del Rawlins- del@_kills_spammers_rawlinsbrothers.org
Remove _kills_spammers_ to reply via email.
Unofficial Bearhawk FAQ website:
http://www.rawlinsbrothers.org/bhfaq/