Topic: Reg/rectifier question

[dave500]

if you just spin a car alternator without a battery hooked up it wont produce any electricity.

[dave500]

i dont think i know of a permanant magnet automotive alternator.

[Spanner 1]

Fantastic!... then the ign. must be getting it's voltage from the battery, wow...   OR the alt. needs voltage from the battery to make it produce 'electricity'... where did I hear that before, recently ?

[dave500]

hang on spanner,,you said completely different system of charging, you spin a car alternator=volts  please explain.

[Spanner 1]

All I know is that a car type alt. can produce charge power when the barttery is dead and 'jumped' by an external battery briefly....... there is some difference that I am not concerned with ( in this topic)..... try to get back to the subject would be good = 'the bike runs off the alt. when the battery is fully charged'.... Choose right or wrong 

[dave500]

ok spanner im only rattling your chain,,can you push start a fully automatic transmission car?

[TwoTired]

how come i can remove the battery from circuit in my car and it still runs?

A car's alternator is driven at a speed where it can provide full or nearly full power at engine idle with a pulley ratio system. It doesn't spin at crank speeds like the SOHC4.  And, it isn't required to stay in one piece when spinning at 9000 to 11000 RPM like the SOHC4 alt does.
Car alternators do have an excited field similar to the SOHC4.  They also have slip rings.  The two devices clearly have different design goals, which perhaps are too subtle to be understood by the untrained.

It's an apples and pears comparison, really. 

A hot rodders trick was to change the pulley ratios on high revving small block Chevies to keep the alternators intact at 8000 RPM (and higher) crank speed red lines.
Usually, the cam would run so rough at idle that the idle speed was also bumped up, which was also necessary because the battery would drain with a lot of low RPM around town driving.  Does that sound familiar?

Cheers,

[dave500]

thanks tt,i still want to see who has also push started a fully automatic car like i have,a lot off topic but i just gots to know.

[dawdish]

Let me throw a new bit of info in...a GM alternator (just the regular old delco) doesnt nead a field exciter. Just jump the two spade terminals together, and as soon as it gets off idle, it starts charging normally. I have this system on my GT6, works great.

 Like I said, for a car guy like me, rather new to sohc Hondas. The sohc charging system takes some getting used to. The sohc alternator does not make its own current. If my CB400F battery is too low to start the bike, it wont kick start, I have to jump it.

[Spanner 1]

Sorry RT.... again you refuse to get away from a cars charging system..... it is not what happens on your SOHC bike where the battery CONTROLS the alternator's output.. Learn something new, dude.

[TwoTired]

Both the SOHC the 'Maintenance Free Field Control' and 'Automotive Brushed Field Control' systems can be found on motorcycles revving at or above SOHC redlines. SOHC system is less efficent, that is all due to the airgaps/flux differences.

True enough.  The CB650 is one of these, and the excited rotor is prone to failure/self destruction, in part due to the centrifugal forces incurred during the high revolutions.  Some Hondas that employ this scheme are not directly connected to the crankshaft, and have clutches that disengage/uncouple the wound rotor shaft during high RPM operation.
The "less efficient" proclaimation is precisely why the CB350, 400, 500, 550,and 750 SOHC4, don't have adequate charge power at idle speed to run the entire bike, and supports Spanner's argument.

The 79 750K (and other higher rpm) use brushes on crankshaft alternator (non-geared) at an rpm range higher than the SOHC so the rpm issue seems to be a non issue for Honda in this case.

These types have a notoriously higher failure rate than the CB350, 400, 500, 550, and 750 SOHC4, associated with the rotor AND the brushes.
My Cb700Sc as rotor windings and brushes.  However, the alternator rotor is not directly attached to the crankshaft.  And, in 72000 miles the brushes have been replaced twice.

Details do matter.   I'm surprised you would use "seems" as any sort of scientific proof of argument.

But, I seem to remember the original owner of the CB700SC stating the charging system frequently failed on him, causing repeated battery and alternator replacement.  So far, I've only had to replace the battery.

[bollingball]

thanks tt,i still want to see who has also push started a fully automatic car like i have,a lot off topic but i just gots to know.

Dave I have infact pushed started my automatic car. I had to get it to 35 mph but it did start

Ken

[TwoTired]

I'll reason scientifically that you were one of those guys that wished they had one or if they did, brought it to a shop for maintenence.

And you'd be wrong yet again.  (Consistency is not always a good thing).  Apart from tire changes, I do all my own work on my bikes, and have since 1965.  The 74 Cb550K I got in 75 as a wreck, and was a down to the bare frame rebuild. 

[TwoTired]

thanks tt,i still want to see who has also push started a fully automatic car like i have,a lot off topic but i just gots to know.

Dave I have infact pushed started my automatic car. I had to get it to 35 mph but it did start.

I have push started auto trans cars and trucks, too.  Though not all can be.  The Auto trans must have a fluid pump on both input shaft and output shaft to make internal pressure.  Not all auto trans cars have both pumps.  These vehicles usually can't be towed on their drive wheels, or risk bearing damage from no oil circulation.  That's the tell tale in the owner's manual.

Still needed some juice from a battery for spark and exciting the alternator to get the engine to life.

Cheers,

[crazypj]

Both the SOHC the 'Maintenance Free Field Control' and 'Automotive Brushed Field Control' systems can be found on motorcycles revving at or above SOHC redlines. SOHC system is less efficent, that is all due to the airgaps/flux differences.

True enough.  The CB650 is one of these, and the excited rotor is prone to failure/self destruction, in part due to the centrifugal forces incurred during the high revolutions.  Some Hondas that employ this scheme are not directly connected to the crankshaft, and have clutches that disengage/uncouple the wound rotor shaft during high RPM operation.
The "less efficient" proclaimation is precisely why the CB350, 400, 500, 550,and 750 SOHC4, don't have adequate charge power at idle speed to run the entire bike, and supports Spanner's argument.

The 79 750K (and other higher rpm) use brushes on crankshaft alternator (non-geared) at an rpm range higher than the SOHC so the rpm issue seems to be a non issue for Honda in this case.

These types have a notoriously higher failure rate than the CB350, 400, 500, 550, and 750 SOHC4, associated with the rotor AND the brushes.

YamahaXS650 uses the same system and they are also notorious for failing
 The moving windings don't centrifuge themselves apart but heating cooling cycles combined with vibration and centrifugal force breaks down the insulation
Unless there is some residual magnetism, generator won't produce any power no matter how fast you spin it

[scottly]

i dont think i know of a permanant magnet automotive alternator.

Hey, Dave, I converted a Mopar alternator to permanent magnet field for a wind charger, back when I lived without commercial power. I pressed the pole pieces and field coil off the rotor shaft, and replaced the field with 2 doughnut speaker magnets. I also rewound the stator with smaller wire and more turns, to enhance low RPM output. Hooked it up to a Briggs & Stratton to spin it up for a test, and it worked great! At least, until I spun it up to about 3K RPM, when the speaker magnets shattered from centrifugal force.... 

[dave500]

thanks tt,i still want to see who has also push started a fully automatic car like i have,a lot off topic but i just gots to know.

Dave I have infact pushed started my automatic car. I had to get it to 35 mph but it did start.

I have push started auto trans cars and trucks, too.  Though not all can be.  The Auto trans must have a fluid pump on both input shaft and output shaft to make internal pressure.  Not all auto trans cars have both pumps.  These vehicles usually can't be towed on their drive wheels, or risk bearing damage from no oil circulation.  That's the tell tale in the owner's manual.

Still needed some juice from a battery for spark and exciting the alternator to get the engine to life.

Cheers,

i started a 65 galaxie,would that be the cruisomatic behind the 390?we had to get it rolling pretty fast.

[TwoTired]

i started a 65 galaxie,would that be the cruisomatic behind the 390?we had to get it rolling pretty fast.

Probably a C6 behind that big block.  The rear pump makes enough pressure to operate the band servos and couple the torque converter between 30 and 40 MPH.  Push in neutral to that speed and then drop it in "D".

That's the same trans I have in my 72 Ford truck.    No complaints.  But, I've never needed to push start it.

Cheers,