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  1. #1
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    Default Permanent magnet motors

    The Permanent magnet starter motors you see in cars nowadays are much smaller and efficient than the old field coil types .

    How do they manage to make the magnets perform as they do ?

    Mike

  2. #2
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    Mike I think that has more to do with the epicyclic gearbox reduction than the magnets,
    the motor spins faster with less amps than the older motors and gains the torque via the g/box.

  3. #3
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    I believe the modern rare earth magnets that can resist demagnetisation at the sort of huge currents used in starter motors, were simply not available in the past. Or they were too expensive for starter motors. Nowdays 3/4 of all rare earth magnets come from China. Chris

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    Default motors

    Quote Originally Posted by shedhappens View Post
    Mike I think that has more to do with the epicyclic gearbox reduction than the magnets,
    the motor spins faster with less amps than the older motors and gains the torque via the g/box.


    Hi ,

    Yes I read about the gearbox inside the starter motors .

    But I think there are also stronger magnets available these days , compared to , say the 1970's and earlier . Apparently, the perm. magnet starters have only been around since the late 1980's . The boffins may have discovered a more efficient magnet e.g., stronger for its size . Mike

  5. #5
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    I had a bit of bo peek in goog's and found this on GM's first of these starters Popular Science - Google Books

    But a bit of a search on amp draw is inconclusive, GM in that article says there is no difference whereas other reports say amp draw is lower, if the amp draw is the same then why are solenoids and battery cables smaller with these starter's ?

    I might check the amperage on two fords here, a 92 and a 86, both 6 cyl and I think the 86 has the older style starter.

    It has me intrigued now

  6. #6
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    I'd say the wire size would be related to how long they expect the starter to be on for.

    I think current start motors have twice as many poles(?) as well. Old starters only had two brushes right?(its been awhile)
    The new smaller starter I have seen inside (both of them lol) have four brushes.

    Stuart

  7. #7
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    Default Info

    OK good replies

    Stuart: you will find that the older field coil starters are 4 pole , the ubiquitous LUCAS starters are definately 4 pole .

    shedhappens: Ford here in Aust. did change over to the perm. mag. starters around 1987 . The later production Falcon XF's from 1987 do have them fitted .

    cba: I would like to know if the magnets in perm. mag. starters are the rare earth magnets, if they are then you would think they would be recycled because of the economic value of those magnets . The Chinese must be laughing all the way to the bank - we have the iron ore but they have the magnets .

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    We have rare earth minerals in Australia too, and some other countries. But China is organised to supply everyone, of course.
    I think the explanation that these materials are making possible the smaller starters is probably correct.
    Planetary gears have been known since earlly car days (Ford Model T geabox for example), so unlikely that is the whole reason for dumping excited field coils.
    Motorbikes had planetary geared starters since at least the '60s.
    Apart from size and weight savings, a lot less copper is needed to make a PM starter, saving cost.
    It used to be that PM magnets weren't strong enough to make a car engine starter, so instead electro-magnets were used to get the needed magneto-motive force. That changed once the newer magnet materials became available.
    Rare earth magnets are cheaper than previous PMs like Alnico too, in terms of strength per dollar.
    As no current is needed to energise field coils, more copper can be saved in the cabling too. And batteries are smaller, as the current demands of field coils is absent.

    Jordan

  9. #9
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    Quote Originally Posted by morrisman View Post
    cba: I would like to know if the magnets in perm. mag. starters are the rare earth magnets, if they are then you would think they would be recycled because of the economic value of those magnets . The Chinese must be laughing all the way to the bank - we have the iron ore but they have the magnets .
    I am pretty sure that only rare earth magnets can be used for starters, but cannot tell you which alloys exactly.

    "Rare earths" can be found in many countries. It just happens that its mining is a very polluting affair. The Chinese seem not (yet) to mind pollution the way we do. So for now they choose to poison their country in return for our money. It is surely just a matter of time until the Chinese people realize what is happening to them. What they stuff in the bank now, may soon be badly needed for cleanup and decontaminatiion.


    Here a clip on rare earth mining. Maybeafter all, the inefficient old starter motors were the lesser evil.....
    Rare Earth Minerals Turn Villages to Ruins - YouTube

  10. #10
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    shed said in #5
    "I might check the amperage on two fords here, a 92 and a 86, both 6 cyl and I think the 86 has the older style starter."

    Ok fella's, I did a bit of test with my Jaycar clamp meter.
    Both cars are duel fuel and the engines are in good nick, I just put a fully charged a brand new battery in the 86, the gas switches were in the middle pozzie so the engine's wouldn't start and I got my son to crank the cars over 3 times each for about 5 seconds to get reasonable figure's.
    The 86 falcon had about 250 amps when first engaged and then settled down to about 200 amp,
    the 92 falcon, I should mention has an engine out of 2000 au tickford in it now, the current when the starter is first engaged was 270 amp and then settled down to about 130 amps.

    for permanent magnet starters

    john

  11. #11
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    Quote Originally Posted by shedhappens View Post
    shed said in #5
    "I might check the amperage on two fords here, a 92 and a 86, both 6 cyl and I think the 86 has the older style starter."

    Ok fella's, I did a bit of test with my Jaycar clamp meter.
    Both cars are duel fuel and the engines are in good nick, I just put a fully charged a brand new battery in the 86, the gas switches were in the middle pozzie so the engine's wouldn't start and I got my son to crank the cars over 3 times each for about 5 seconds to get reasonable figure's.
    The 86 falcon had about 250 amps when first engaged and then settled down to about 200 amp,
    the 92 falcon, I should mention has an engine out of 2000 au tickford in it now, the current when the starter is first engaged was 270 amp and then settled down to about 130 amps.

    for permanent magnet starters

    john
    That is quite a big reduction in AMPS .... my 87 XF has the perm mag starter so you just missed out

  12. #12
    BobL is offline Member: Blue and white apron brigade
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    It's not just rare earth element (REE) mining the chinese are into, their REE R&D is massive. An example of this is that they have more PhD students and researchers studying REE technology than the rest of the of the world put together. The Chinese have selected a range critical energy related technologies to become the lowest cost providers for, as well as REE magnets, the others include PVs, and double and triple glazing panels.

  13. #13
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    Default Permag efficiency.

    Certainly some efficiency to be gained with the permag motors. When first available, I fitted a pair as replacement fan drives in a cab top aircon on construction machinery, and reduced power requirements somewhat, and I think they ran cooler. Did find out they can be a bit fragile. Rolled a new one off the cab top and bounced it off the steel tracks. Discovered that when the magnet cracks it becomes two magnets, one pulling in each direction, and the motor goes nowhere. Some things you learn the hard way. Oh well! Combustor.
    Old iron in the Outback, Kimberley WA.

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