| Author | Message | ||
     Fullpower |
and for my next topic. i believe the XB series uses a shunt type voltage regulator.meaning any electrical power not being consumed by the fuel pump, injectors, and lights is simply shunted (conducted) to ground. thus the rotor is always fully loaded. any one looking for some "good dyno numbers" could with a minimum of sleight of hand loosen the stator lead connector next to the front pulley sprocket, thus removing the parasitic load and freewheeling the alternator rotor. my guess is one would get a quick RWHP or two. it would make an interesting experiment to someone already engaged in a dyno test. | ||
| Fullpower |
now where is Reepi with the 3 phase transformer to step the stators ouput up to 1500 volts, driving a very small 3 phase traction motor expertly wound around the front axle tube and splined to the front wheel, just enough to give a slight forward "pull" while cornering? now wouldnt that be tits? | ||
| Reepicheep |
Dangit. I told you to stop baiting me over here with these threads. I have *work* to do. (I asked that question, and Aaron answered, he disconnected the stator and did some dyno runs, and could not get it to show up either with or without. There is no doubt something to be gained, but not much) There are a couple dual wheel drive dirt bikes, but I think they go for hydraulic or gear systems, not 'lectrics. Where's Tesla when we need him. | ||
| Wyckedflesh |
FP in the case of the stator, look how difficult it is to just pull the stator case from around the coils. Your still fighting the magnets. Its not like in an Alternator where the magnets are much smaller and have less parasitic effect. Now if you could remove the stator itself, and bolt on an automotive alternator to run off an underdrive pulley system, that might free up some horsepower. | ||
| Reepicheep |
Unless you are actually generating power, I don't think you get much net parasitic loss from the magnets. If you somehow do, I *think* you just created a perpetual motion machine. | ||
| Wyckedflesh |
Reep I would think if you didn't get the parasitic loss from the magnets that would be the perpetual motion machine. I mean I have taken car alternators apart and don't feel a quarter of the pull as I slide the windings out from the shell, yet you have to put some muscle into pulling the stator off the windings (once you get it loose of the crankshaft mind you) and if its lined up nicely it sure sucks the stator case back on damn quick... | ||
| Reepicheep |
Right, but if you rotate it, I think you will find that it is harder to turn for some number of degrees, then whips forward some number of degrees. You are effectively storing energy, then releasing it, like a spring. It may feel harder to turn, and choppier, but I don't think it would ultimately make a difference to the motor. Another power tangent (it's late, I have been working since 6 this morning, and I am getting punchy)... you probably know this, but its a fun point to make. Take a generator, unloaded, and spin it up with another motor. It turns easy. Now short out the generator leads. ****WHAM**** We did this in a machines and power class I took. Scared the *crap* out of me. Sounded like somebody rammed a baseball bat into the generator. I was amazed at the amount of mechanical force created. Ultimately, it is no suprise. If you have a generator producing 760 watts, something is pushing about a horsepower of power into the crank of that generator. It works the other way as well, if you have a big old flywheel freewheeling on an unloaded generator, and you suddenly demand a few thousand watts of power, the energy from that flywheel gets delivered in a jiffy. Cincinnati Gas and Electric had the opposite problem (where is Court when you need him, darnit!). They have a generator, dropping megawatts into the grid, which puts a heck of a load on a monster shaft driven by huge turbines driven by steam from the boiler. What would happen if the "wire" (which is actually closer to a bundle of railroad tracks) delivering that power got "cut" somehow? The load on the generator would go away, and the generator itself would nearly instantaneously accelerate to speeds that would take out a good part of the power plant. So you can never "disconnect" the generator, even in an emergency. Instead, you have to (as I recall) reroute the power to some big heating elements that boil off thousands of gallons of water, and slow the generator in a controlled fashion. Always gave me, as a wide eyed co-op, the heebie jeebies walking by Unit #6 at the Beckjord power station. | ||
| Wyckedflesh |
I remember the notchyness of what you speak with regards to my old VW generator. I had forgotten that aspect until you mentioned it again. | ||
| Firemanjim |
I was told by a Buell mech I know that there are aftermarket regulators you can get that work on demand instead. | ||
| Reepicheep |
Electrically, it would be straightforward, but you would need more wires into/out of the regulator. When I first saw the shunt design (which is pretty unusual from my electronics background), I thought it was designed by a madman. The more I think about it, the more sense it makes though. It is a nice, simple, and elegant solution, even if it does "waste" some power. | ||
| Benm2 |
I thought that automotive alternators could adjust to load conditions by controlling the strength of the armature field. Isn't that why automotive alternators have brushes? The Buell system is all permanent magnet, right? Wouldn't that mean its generating electricity all the time? I mean, every time the rotor passes a coil, the magnet generates current in the coil. Even if that current goes nowhere, its still generated. Even if the produced current goes "nowhere" by disconnecting the stator, the AC current is still being generated, so there would still be some load. If the magnetic field in the stator could be controlled then the generated field could also. Is that right? Related topic, though. If you wanted to reduce the current generating capability of the stock alternator, how could it be done? Would removal of a few of the stock coils reduce its power consumption / generating capability? Does the stock stator use cheap or fancy magnets? Could a lighter stator be made using "rare earth" permanent magnets? I've read that Honda & Yamaha (at least) make "kit" alternators with reduced output for racing. This is certainly not done without good reason, but Buell doesn't make one. Supply & demand, I'm sure, but that doesn't mean there's no potential benefits. From what I've seen in the aftermarket, plenty of larger capacity units are available though. Since there are at least a few track-only buells here, maybe this will sustain interest. Can the resident EE's suggest a method to make a lower-drag system? | ||
| Reepicheep |
You are right about how the alternator works, though I forget the physics of it. For either, just because it is spinning does not mean it is producing power, and producing power is where the drag comes from. It will produce voltage, but power is voltage times current. You can produce the 60+ volts out of the alternator, but until you actually flow some current (i.e. connect those wires to something) the alternator crank has no significant load. The more power you flow, the more load the alternator sees. It would be simple (and I have heard they exist and can be bought) to build a highly efficient voltage regulator that would only draw as much power as the bike needed, and would reduce drag. It won't be enough power to spot on a dyno (based on experiments Aaron did), but it would be there, probably under 1 horsepower. The most efficient, smallest, and lightest types of regulators are typically switching regulators, like used in your laptop or desktop PC. Design is straightforward, but non-trivial in nature. The bigger benefit might be that you are not just constantly dumping 60 to 150 watts of waste heat either out your stator, our out your voltage regulator, and into the engine. The horsepower gains would be background noise, but getting a hundred watt heater out of your primary might be a good thing. | ||
| Davefl |
Crane makes or made such a regulator. I have one on my M2. It has a built in charger as well. | ||
| Rick_a |
Makes me wonder how hot the stators get on open primary bikes that don't have a bath of fluid to help cool 'em. | ||
| Benm2 |
Wouldn't there still be the capacitance of each coil? As the magnets passed the coil in alternating n-s-n-s sequence, wouldn't each pass "push" the current inside the coil in alternating directions? Does an AC transformer with flowing current on one side consume power even if the other side is "open"? | ||
| Fullpower |
benm: the laminated stack AC transformer is one of the most efficient power conversion devices extant. with an open secondary, that is no load, parasitic losses run well under 1/2 of a percent of rated transformer power. | ||
| Benm2 |
So, the purpose of the smaller "kit" alternators would be to (1) reduce overall weight and (2) assuming the same shunting setup, reduce parasitic drag by dropping overall output current. However, for a Buell, some possible alternate regulator could accomplish nearly the same thing with regards to the second benefit. Its the first benefit where the aftermarket is lacking. Again, could a lower output alternator with be built from the stocker, and how might that be done? | ||
| Reepicheep |
Good question! I think the regulator would be the way to go for a "lower power alternator". Go from a shunt to a properly regulated reasonably efficient unit. That being said, to do it right, you would probably want a switching regulator, which is not going to be simple or cheap. Not rocket science, but not something somebody is going to throw together in a basement over night. In theory, you could "jumper" some of the stator windings. Or better yet, just rewind an old blown stator with fewer turns... though the winding pattern can get a bit hairy. |
