Alternative Alternator Options

[TopCatGr58]

Hey folks,

After reading some of the posts in Geezer's High Output Alt. thread, I didn't want to hijack his thread again. But I was wanting to do some brainstorming regarding our options. Most of us are not with "deep pockets", and so I think that's partly why we aren't too excited about shelling out $300.00 for a high output alt, although it might be able to maintain the stock location and look.

What I'm wondering about is the "GARAGE" mech mod that folks could do without shelling out so much $$. I just reviewed the diagrams for the crank, rotor and seal, cause I couldn't recall whether the rotor had anything to do with the seal, but it looks like it doesn't. The seal is around the crank, and the protrusion sticks out into the ALT chamber, and rotor slips over the tapered end and is bolted on.

As has been discussed keeping the rotor might be beneficial to the flywheel affect. The ALT cover keeps the oil galley plug in place, so that's a consideration. If there aren't any electrics under the OEM cover, then a simple plate should work to fit over that area to hold the galley plug and provide the mounting for the relocated ALT.

There was a lot of discussion regarding heat and water exposure, and I was thinking, what about MARINE ALT? I've heard that some can be water resistant or proof??? And I wouldn't think we would need but about 60 amps or so, not 100+ !? And many have built in Reg/Rects.

SO...depending on the size of the ALT, just wondering if it might be able to be fit above the OEM location vs. back behind the jugs/below the carbs?

Also being able to get/find a pulley with a tapered fit for the crank if removing the rotor, or one that will just fit with the use of the rotor bolt and keeping the rotor??

Okay, ideas, storm away!?
T.C.

[natemoen]

Ok, if we are going into wild brainstorming mode then here we go.

Now I do not know size wise what kind of space there is under that cover but son I will have.to remove it and find out, but would there be a alternate small enough to mount under the cover? The hard part would be directly connecting the alt to the crank, and finding one that could spin up to at least 10000 rpms, as well as heat.

[XS1100 Newbie]

I would think that in this scenario that we would need to look at the newer alternators. They are very small' and some of these new engines are turning up towards 10000 RPM'S. Remember when 6000 on our hot rods was stretching it? Some of the alternators are only about 5 inches in diameter. I am pretty much convinced that trying to modify what is there is not going to get us to where we want to be, because of the limitations of room.

[crazy steve]

...and finding one that could spin up to at least 10000 rpms, as well as heat.

The rpm isn't a problem, well it is, but rather it's the reverse. Most belt-driven alternators are overdriven (big drive pulley, small driven pulley) and alternator rpm of 300% above engine speed are common. So the issue here if you direct-couple the rotor to the crank is you probably won't have enough rpm to get the alternator into full output until you're well up in engine rpm. Idle speed output would be worse than in a OEM application. So I see a belt drive with speed multiplication of some sort as a requirement.

As far as a marine-rated alternator, I dunno. I think the main difference here isn't so much water-or-weather proof as it is to prevent sparking (with the brushes shielded better) and igniting bilge fumes.

I think the easiest path would be to find a higher-amp unit off another motorcycle. Some vintage 'police models' must have had higher-capacity alternators (anybody know what a KZ1000P alternator put out?), as well as newer touring models. But no matter what you do, unless the new unit has the same frequency output at the same rpm, you'll be replacing the OEM tach...

[TopCatGr58]

I was wanting to shy away from the MC ones, because they tend to be $$, whereas the automotive ones seem to be a bit cheaper.

Okay, does anyone know the FREQUENCY "Kenneth" of the OEM ALT for it's tach signal?? I've seen some alts in the short search I did that mentioned the connector for the Tach!? I wonder if they are adjustable, or if something could be plugged inbetween the new ALT and the tach to be able to "TUNE" it to the XS11 tach??? I'm an electronics novice here, so not sure how feasible that would be, not sure if it would require some sort of circuit board with a chip that could filter out/down a certain frequency to that of the OEM tach?

So...we would need to match the frequency of the high output ALT to that of the XS11's OEM taking into consideration the increased RPM required to drive the HO Alt as well, which would mean a higher frequency anyways!?!?

I had thought about mounting a newer design onto the end of the crankshaft, but wasn't sure about how to do it, and being able to get it exactly parallel/inline with the shaft so that it wouldn't vibrate as well as just tear up the bearings!?!?

That's why I think the plate and remote mount with belt drive is the better easier solution!? I sent an email to Geezer, I'm doing a little non-MC machining job for him, but told him about this thread, and asked him about how the wiring of such an ALT would be done to our harness....again thinking the easier way is using one with a built in REG/RECT. But I think several of you guys are also quite Electrically gifted and could inform us on how this would be wired in?

I'm sure it would depend on what style and features the ALT would have.
Like bypassing all of the OEM ALT/REG/RECT wires, and have a large charging lead going to the battery, as well as a smaller (+) tap for the alt to sense the voltage state/level of the system as well as power the field coils, along with a ground, and perhaps the tach wire??? And what would need to be done to Bypass/remove the OEM Reg/Rect and wiring??

T.C.

[crazy steve]

I'll throw one more idea out there... a permanent-magnet type alternator. This would be relatively easy to adapt, has even fewer parts than the XS alternator and has the advantage of being able to start the bike (by either bump-starting or kick) even with a dead-flat battery. Harley uses this type, there may be others. I know you can get 32 amp units for the Harleys; here's the whole works for $140...
http://cgi.ebay.com/ebaymotors/ALTER...item43a4e2c1ed
The HD units are fairly large in diameter (better than 6") so they won't fit under the stock cover, but are pretty shallow (less than 3") so they won't stick out as far. As far as being 'weather-proof', some of these run inside the motor in oil.

[crazy steve]

..Okay, does anyone know the FREQUENCY "Kenneth" of the OEM ALT for it's tach signal?? I've seen some alts in the short search I did that mentioned the connector for the Tach!? I wonder if they are adjustable, or if something could be plugged inbetween the new ALT and the tach to be able to "TUNE" it to the XS11 tach??? I'm an electronics novice here, so not sure how feasible that would be, not sure if it would require some sort of circuit board with a chip that could filter out/down a certain frequency to that of the OEM tach?

T.C.

Keeping the OEM tach would likely be the hardest part of this. The XS alternator frequency varies by rpm, and is also determined by the number of poles on the rotor/stator, and the 'type' of stator wiring (in this case, a 3 phase 'star' or wye connection). If your replacement matched in the number of poles on both the rotor and stator and is a 3-phase stator and is direct-coupled to the crank, the tach should work as-is. But any differences (rotor rpm vs engine rpm, more/fewer poles) and your calibration is gone.

As far as 'adjusting' anything, I doubt it, but there is some pretty trick electronics out there these days (usually with 'trick' prices too!) so it may be possible.

[cywelchjr]

Keeping the OEM tach would likely be the hardest part of this. The XS alternator frequency varies by rpm, and is also determined by the number of poles on the rotor/stator, and the 'type' of stator wiring (in this case, a 3 phase 'star' or wye connection). If your replacement matched in the number of poles on both the rotor and stator and is a 3-phase stator and is direct-coupled to the crank, the tach should work as-is. But any differences (rotor rpm vs engine rpm, more/fewer poles) and your calibration is gone.

As far as 'adjusting' anything, I doubt it, but there is some pretty trick electronics out there these days (usually with 'trick' prices too!) so it may be possible.

Frequency multiplication or division isn't really all that hard to do. The hard part is determining what the ratio has to be. IIRC that stuff can be pretty cheap to put together too.

[Doo-Daa]

Most automotive alternators are "3 phase" WYE Connected devices. That is why there are 3 diodes in them. the "wye" connection allows for a 'common' at the center, that in the auto world connects to ground (common). And since there is only 1 pair of slip rings, there is probally only 1 rotating pole. The hard part will be the alignment, unless it is remote mounted.

If a drive pully could be placed onto the existing shaft, it should weigh about as much as the currently installed rotor, to maintain the flywheel effect. TC should be able to machine that as it would follow along the same design as his SOFAs. Notch a cover to bring out the fanbelt, and mount the alt external to the case. Finding a spot to fit the alt, is the technical/tactical issue. Then fab a belt safety cover. A std GM old style upper adjusting bracket might work, (for development), then change over to turnbuckle with lock nuts to ensure tension stays as a final product.

As a final input thought, the newer asian style alts are a lot smaller, but cost more also. All alts since the late 60s are internal regulators. Alts are already 'weather resistant', not submersion proof, but they don't usually fail after being submerged. Ask any 4X4 enthusiast. Mine used to get soaked all the time.

Or you might be able to leave the current alt in, pulley fit in between engine case and alt. Bring belt out the same way, then pick off all demand and supply with external alt, and leave tach where it's at.

Just some random thoughts. Doo- Daa

[cywelchjr]

That could be an interesting idea with keeping the original just for the tach. Another thing might be to use a short serpentine belt rather than a v-belt because that would be less prone to slip and they last FAR longer. Might be harder to fabricate though, although it might be possible to find an off the shelf pulley that only needs the center modified.

[Doo-Daa]

I don't think you'll find a serp belt that short, but if you're worried about slip, then cut the pully thickness in half by just going with a size 30 chain (about the size of a bicycle(sp?) chain. that way with a master link in hand your distance between pulleys is completely adjustable. And any tractor supply house, Gebos, Tractor Supply, or Grainger is full of different sizes. Plus it tack welds perfectly to everything involved.

Doo-Daa

[DiverRay]

AND some of the GM alternators have a fitting for a tach already! I know it was an "option" on my '90 Suburban 6.2 diesel.

[TopCatGr58]

More brainstorming fun!?

Hey Ray,

Yeah, I've found many in the aftermarket searches that have the TACH terminals. But the bit questions are...what is the frequency/ratio of the signal that our OEM ALT sends to the tach? It's off of 1 of the 3 legs of the ALT. I am just assuming that it would send out 1 pulse for every rotation of the crank, since it's tied directly to the crank.

So...another assumption is then that the frequency would be 1 pulse per rotation, so 1000 pulses would be 1000 rpm, and on up as it speeds up!?

The second question would then be how many pulses would the aftermarket tach terminal provide. It's been said that the auto alts are spinning at a 3 to 1 ratio to the crank rotation.....so 1 rpm crank might be 3 rotations of the alt, and therefore 3 pulses....again, under the assumption of 1 pulse per rotation.

Here's the possible fun part!? So...many cars are driven at between 1000 and 3000 rpm occasionally higher for short bursts, but usually cruise at ~1500 rpm, that would be somewhere between 3000, to 4500 to 6000 ALT rpm for most of the normal operating engine rpm range. I wonder if AUTO ALT triggered tachs are calibrated at 1/3 ratio, so that 3 pulses would equal 1 rpm?? IF so, then it would work out for us...again big assumptions coming here, hoping some real auto mechs can confirm the tach signal ratios???

Yes, our bikes can run from as low as just off idle of 1000 rpm, up to 8000, but usually are run in the 3k to 5k range. SO...with a same sized pulley from the crank/rotor to the alt, would mean a 1 pulse = 1 rpm, and IF our tachs use the same ratio, then it would work. ALSO, even though the AUTOMOTIVE ALT may not put out its FULL AMP power at idle speed/~1000 rpm, it would probably still put out equivalent to our OEM of 20-25amps, and then at cruising speeds of 3-5k rpm, should then easily put out its full AMP power of around 60 amps...the size/power that I have been looking at...I don't think we need/want 100+ amp $$ ALT!? I think twice our stock output would be more than adequate!?

So....now can any mechs/electrical techs shed some light on the tach signal specs for both the autos as well as our OEM!?

T.C.

[crazy steve]

Yeah, I've found many in the aftermarket searches that have the TACH terminals. But the bit questions are...what is the frequency/ratio of the signal that our OEM ALT sends to the tach? It's off of 1 of the 3 legs of the ALT. I am just assuming that it would send out 1 pulse for every rotation of the crank, since it's tied directly to the crank.

So...another assumption is then that the frequency would be 1 pulse per rotation, so 1000 pulses would be 1000 rpm, and on up as it speeds up!?

T.C, I don't know how many pulses you get per rpm, but I'll guarantee it's far more than one. What frequency you get out of an alternator depends on several factors, with rpm being only one.

Without getting into a long explanation about polyphase generators, you can get a rough idea by looking at the number of 'poles' you have. In this case, you have 12 poles on the 'rotor' and roughly 30-some on the stator. Because this is a star/wye wound stator, 1/3 of the poles goes to one output wire. So in one revolution, the 12 rotor poles go past 10 stator poles; so 12 x 10 = 120 'pulses' per revolution. So at 1000 rpm, that gives you 2000 CPS aka Hz (120 x 1000/60 = 2000). That's your frequency. Now, this is an major over-simplification, as this doesn't take into account how the stator is physically wound and how the poles are interleaved, so the actual number could vary by a lot. Even if you assume only 3 poles for the stator and assume it's wound in such a way that it 'sees' only 3 of the 12 rotor poles per 'pulse', that still gives you 200 Hz output per 1000 rpm. This is a design characteristic of this type ('inductive' alternator) generator; it's original use was to produce very high frequencies to power electric smelting furnaces. In this case, this gives you a very 'smooth' output once the AC has been rectified into DC.

How would this compare to another alternator? If your 'pole count' on both the rotor and stator are the same (assuming the stators are both wound exactly the same), you should get the same frequency output for a given rpm. But change any number, and frequency will change too.

How would you determine actual frequency? Well, the more high-end clamp-on ammeters will read frequency, but I don't know that they read that high. You rarely run into CPS up to 400 Hz in 'standard' electrical; you'd probably have to hook this to a O-scope to get an accurate value. Throw in some sort of speed-multiplying alternator drive so that engine rpm no longer matches alternator rpm, and that skews it even more.

[TopCatGr58]

I have an old ANALOG Dwell/Volt/Tachometer !

But I think it can only read DC type pulses from the ignition spark plug coil, I don't know if it can recognize the AC type pulses from the tach signal wire.

Geezer told me that our tachs have a rectifier in them, so I'm guessing that converts the AC into DC pulses for it to work/read them.

So...Can I get/use a simple DIODE to connect to the tach signal wire and convert it to DC pulses for my analog tach gauge to be able to read it??

The gauge I have is an old Actron 617 Dwell/Tach/Voltmeter, has different scales for 4, 6, 8 cylinders, but only goes up to 4,000 rpm on the 8 cyl, which is reading 4 pulses per rpm, takes 2 rpm to complete a full intake/comp/fire/exh combustion cycle. This equals ~66 pulses/sec for 1000 rpm.

Well, if your calculations are right above, then this tachometer will not be able to see/count the pulses from the ALT because it will be way too high of a count...ie. 1000 per second, vs. 10's!

T.C.