Topic: An attempt to improve the CB500/550 alternator output...

[HondaMan]

...OK, now that I have your attention: 

The low output of the CB500/550 alternator comes largely from the poor construction of the rotor. You only need to look at its bigger brother SOHC4 rotors to understand it: the early 750 (290 watts output, MAYBE) had poor welds in the 'holes' of the rotor, while the F1 and later versions (330-350 watts output) were very clean, machine-welded (instead of hand-welded) rotors, with half as many welds and occasional grinding marks showing where they were balanced. The later ones make more power, probably spurred on by the requirements of the CB750A bikes, which had more output power because of both improved rotors and higher-current (i.e., stronger magnetic field) of the "A" field coil. The "A" has a solid-state regulator, but this is not the source of the increased output: it is merely the throttle thru which the battery voltage is maintained.

When looking at the 500/550 version, one can barely even SEE the field coil, and this means that many fewer magnetic lines make it out of the coil to be 'chopped' by the holes-and-steel of the rotor to make the alternating field. The welds always look gloppy and amateurish, and from my experience in other Honda areas of the time, I know to have been built by the lowest bidder, and with somewhat less QC in the process. Honda was deeply in debt in other development areas (like the early GL1000 prototypes, which started in 1974) as they also were converting to CNC machines to replace their early NC versions, so low cost parts were the order of the day. (That cool Honda movie someone posted here has reminded me of these things...)

My plan, if I can secure the 2 most-required portions of this, is to (1) test an "opened" (and somewhat lighter) rotor, which will be hand-cut by yours truly to attain what I want, against a standard rotor on the CB550 that is the topic in my next book (underway). The 2nd 'item' I need to find is a (high-speed) spin-balancer service to repair what I will do to the balance in the process, which appears to be personna non grata in the Denver area. The final goal is to improve the alternator output substantially without having to resort to solid-state regulators, for which these alternators were not designed. Those devices can raise the battery voltage in some cases, but at the cost of higher the field wiring temperatures - this disturbs my conservative engineering nature, especially on aged equipment.

So, my requests for forum help for this project is:
1.) Does anyone have a rotor they would be willing to part with? It probably won't be returning home in the end, but will end up on my 'project' bike.
2.) Does anyone know a good spin-balancer in their area who can undertake to spin-balance this part to 11,000 RPM?

[grcamna2]

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[Gurp]

I've got a 73 500 motor I'm not going to use. I can pull the rotor off it when I get some free time.

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[PeWe]

An alternative like for the CB750.
Maybe something like this can be done on a CB5x0... ?

http://forums.sohc4.net/index.php/topic,117735.0.html

[rotortiller]

Here you go Hondaman, maybe do a package deal with your fuse box? Lol

[MauiK3]

Spin balancing
How about any of the people making small boat  or drone propellers? They must do some balancing, perhaps not that fast though.
I'll do some looking around just for fun.

[MauiK3]

https://www.balanstar.com

These folks make high speed balancers, perhaps a call to them might lead to a contact that has the equipment.

[MauiK3]

Would a shop that does high performance engine balancing such as crankshafts be able to help?

[HondaMan]

Would a shop that does high performance engine balancing such as crankshafts be able to help?

That's what I thought, too, but so far they have sounded 'balky' about it. They (local guy) do crankshafts, but he sounded like "Uh, well..." when I last brought this up to him. If I have the actual rotor in hand, maybe it might remove the stumble? Dunno...

[HondaMan]

Here you go Hondaman, maybe do a package deal with your fuse box? Lol

Now, THERE's some hillbilly engineering! I used to see stuff like that when I was a kid in Missouri, back in the 1960s. One was a car with an ONAN generator in the [lidless] trunk, running a small room air conditioner that was mounted into the RR passenger window. I think it was on an Oldsmobile? It had some exotic-looking welded bracketry holding it all together.

[Scootch]

Mark you might check with Mel. He does a lot of machining and rebuilding of Harley motors. He is in Colorado springs. He is also big into guns, military museum and history etc. He balances rotating parts...

https://dragonmans.com/

[HondaMan]

An alternative like for the CB750.
Maybe something like this can be done on a CB5x0... ?

http://forums.sohc4.net/index.php/topic,117735.0.html

He made (makes?) some real nice alternator parts for that setup. It's just a little pricey for the 500/550 (IMHO).

What I'm hoping for with this experiment is a much less expensive approach for the Mid-Fours. The alternator was capable of doing at least 25% better than they do, and the OEM spec for them turned out to be pretty optimistic compared to real life. It is supposed to make 150 watts: most of them make about 85-95 watts instead (at 5000+ RPM) and about half that much at 3000-ish engine speeds where the bikes are often ridden. With the uber-quiet OEM mufflers it wasn't tough to keep the revs higher in order to help, but as soon as aftermarket pipes get used and the added noise tends to cause lower RPM use, the battery problems appear. Over time, the low-charge situation damages the lead in the battery, leading to short life. My own, and my brother's, CB500 (K1 and K2 versions) both went through a battery every year because during the 4-5 months of winter the low specific gravity damaged the lead, especially at the terminal connections. This always caused low-voltage in the next season. In other bikes (circa 1977 and later) with better alternators, the very same batteries were lasting 5 years or more.

[HondaMan]

I've got a 73 500 motor I'm not going to use. I can pull the rotor off it when I get some free time.

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Most excellent! I'm not in a huge hurry: I just got the 500 engine I'm using for my book, and it's still sitting in the garage unharmed.
PM me know how much $$ you need to get it here when you're ready?

[HondaMan]

Mark you might check with Mel. He does a lot of machining and rebuilding of Harley motors. He is in Colorado springs. He is also big into guns, military museum and history etc. He balances rotating parts...

https://dragonmans.com/

Thanks! I'll give him a shout.
It sounds like I might just have to drive down to visit him....

[Gurp]

I've got a 73 500 motor I'm not going to use. I can pull the rotor off it when I get some free time.

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Most excellent! I'm not in a huge hurry: I just got the 500 engine I'm using for my book, and it's still sitting in the garage unharmed.
PM me know how much $$ you need to get it here when you're ready?

Will do Mark!

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[Deltarider]

OK, this madness has gone far enough. If you experience 'insufficient' charging due to how you (ab)use your CB500/550, maybe it's time to replace your bike by the vehicle shown here.

[rotortiller]

ow, THERE's some hillbilly engineering!

When my brother took the picture in a parking lot I carefully explained that this is what happens when you take your Honda in for servicing to any HD dealership.   Might also be humility engineering to some, hell it worked out, just like on the farm!   

[MauiK3]

When you finish the book and I buy a copy I may just have to go looking for a 500/550!

[kerryb]

I'm  looking forward to your new book, I know a gentleman (81 yrs old) whose hobby was balancing machines and hot rods.  I'll ask him about the balancing possibilities.
i've been gathering up 550's as they cross my path, up to 4 now.

[calj737]

2.) Does anyone know a good spin-balancer in their area who can undertake to spin-balance this part to 11,000 RPM?

In my experience with automotive machine shops, I don’t think I’ve ever seen one that spin balances anything at 10k RPMs. If it’s balanced at 3500, then it will hold beyond 7k. Things don’t go out of balance as a singular component. You’d have to have the crankshaft matched to that rpm (each individually) plus any bearings to ensure that at 11k RPMs things were consistent. And who runs a 500/550 motor on the street at 11k?…

Seems a silly spec with no inherent value. On my lathes, if things are balanced at 700 RPMs, they remain balanced to 3300. Never seen runout change especially when both ends of a shaft run in bearings,

[HondaMan]

2.) Does anyone know a good spin-balancer in their area who can undertake to spin-balance this part to 11,000 RPM?

In my experience with automotive machine shops, I don’t think I’ve ever seen one that spin balances anything at 10k RPMs. If it’s balanced at 3500, then it will hold beyond 7k. Things don’t go out of balance as a singular component. You’d have to have the crankshaft matched to that rpm (each individually) plus any bearings to ensure that at 11k RPMs things were consistent. And who runs a 500/550 motor on the street at 11k?…

Seems a silly spec with no inherent value. On my lathes, if things are balanced at 700 RPMs, they remain balanced to 3300. Never seen runout change especially when both ends of a shaft run in bearings,

What I'm mostly concerned about is the imbalance I will introduce as I cut away the excessive weld beading between the 2 halves of this rotor. I'll take up your "RPM spec needed" advice when I find the right guy to do it: I have not done this sort of balancing myself, so I'll be a newbie at it.

The output from these alternators peaks at 5500 RPM and doesn't get much more above that, but the engine sure does! My brother and I routinely ran our CB500s to 10K RPM when play-racing each other on Missouri backroads with no ill effects, although the power had fallen off well before then. Ah, those Missouri summers, where cars were few and the roads were as smooth as...coarse bastard files...

[rotortiller]

You can balance perfect all you want but when it seats a bit differently on the crank then on the balance mandrel things will change. To know best (applied dynamics aside) the rotor needs to be true'd for the balance device and then DTI'd on the crank. Static rotor balancing will be fine for these bikes in the right hands if reducing rotor mass  (it's not rocket science either) and no need for high speed dual plane balance say like a turbine or supercharger might require. Because every rotor and crank has tiny production variances we cannot make things perfect for mass production. If a rotor can be positioned at various radial locations on the crank, which it can, we have introduced a dynamic variable with the finished product, however small that might be. These engines as good as they are, are still low rpm clunkers, so expect some vibration from various dynamic interactions. There are so many harmonic dances going on that a perfectly applied and balanced rotor could actually increase vibrations over that of a slightly imperfect one located at a corrective position, when splitting hairs. You might (situation dependent) be able to measure this change with a dynamic balance device with the engine running and you might not, so basically most understand that a static rotor balance method is good enough for SOHC government work in these cases.

[calj737]

You can balance perfect all you want but when it seats a bit differently on the crank then on the balance mandrel things will change. To know best (applied dynamics aside) the rotor needs to be true'd for the balance device and then DTI'd on the crank. Static rotor balancing will be fine for these bikes in the right hands if reducing rotor mass  (it's not rocket science either) and no need for high speed dual plane balance say like a turbine or supercharger might require. Because every rotor and crank has tiny production variances we cannot make things perfect for mass production. If a rotor can be positioned at various radial locations on the crank, which it can, we have introduced a dynamic variable with the finished product, however small that might be. These engines as good as they are, are still low rpm clunkers, so expect some vibration from various dynamic interactions. There are so many harmonic dances going on that a perfectly applied and balanced rotor could actually increase vibrations over that of a slightly imperfect one located at a corrective position, when splitting hairs. You might (situation dependent) be able to measure this change with a dynamic balance device with the engine running and you might not, so basically most understand that a static rotor balance method is good enough for SOHC government work in these cases.

Couldn’t agree more.

[Tracksnblades1]

Never seen runout change especially when both ends of a shaft run in bearings,

I wouldn’t apply that logic to “drive shafts”. Especially the single longer ones…

[Deltarider]

Wow! This thread is becoming more interesting by the hour! Makes me wish my alternator needed improvement.
A happy New Year to all of you and keep it coming!

[HondaMan]

You can balance perfect all you want but when it seats a bit differently on the crank then on the balance mandrel things will change. To know best (applied dynamics aside) the rotor needs to be true'd for the balance device and then DTI'd on the crank. Static rotor balancing will be fine for these bikes in the right hands if reducing rotor mass  (it's not rocket science either) and no need for high speed dual plane balance say like a turbine or supercharger might require. Because every rotor and crank has tiny production variances we cannot make things perfect for mass production. If a rotor can be positioned at various radial locations on the crank, which it can, we have introduced a dynamic variable with the finished product, however small that might be. These engines as good as they are, are still low rpm clunkers, so expect some vibration from various dynamic interactions. There are so many harmonic dances going on that a perfectly applied and balanced rotor could actually increase vibrations over that of a slightly imperfect one located at a corrective position, when splitting hairs. You might (situation dependent) be able to measure this change with a dynamic balance device with the engine running and you might not, so basically most understand that a static rotor balance method is good enough for SOHC government work in these cases.

Couldn’t agree more.

Thanks for the insight, guys! While I have another 500 engine here [for the book], I plan on selling it after I'm done, so it's not a 'donor' that could borrow the [end of the?] crankshaft, or the like, for the purposes of this little project. In the end, if I could get the typical rotor to actually produce the 150+ watts these were rated, that would be enough for the bikes - they need about 95-105 watts with regular incandescent bulbs aboard and the lights always on (thanks a lot, ex-President Carter...). The trouble is that they often make 80-90 watts, in my experience, and the things that cause the 750 alternator output to drop are not the same on the 500/550 version: they start out low when new if their rotors are especially bad, and never get better. That is the #1 reason this particular bike gets parked: the owner gets tired of struggling with low battery charge and/or constant battery tending issues. On those bikes that have the better alternators I've seen their mileage roll the odometer over, like the 750, from touring America's many interstates and commuting daily to work. Even here, I think Crazy PJ has rolled his over before?

I only discovered this issue (many years ago) when a damaged 550 crankshaft had to be replaced and the donor engine for it happened to have a better rotor (and all but 1 of the same crank journal sizes!). The alternator rotor was on it and I left it there, assuming it would work: after running the bike at idle for a while the voltage was up over 13.6 volts, which I'd only ever seen on one other 550 before. The 'new' rotor was from the last of the 550F series bikes, and had a very 'automated' look to the welds, like they were done by machine and not a newbie welder. The 750 bikes after the F1 have similar-looking rotors.

[calj737]

Never seen runout change especially when both ends of a shaft run in bearings,

I wouldn’t apply that logic to “drive shafts”. Especially the single longer ones…

Are you referring to an automotive style drive shaft? Then true, the U joints at either end aren’t the support I’m referring to. I’m referring to a shaft running in a bearing block type of support. And considerably shorter in length (<36”).

[bryanj]

This is very interesting Mark, i hope you come to a satisfactory result both output and cost.
Have a great new year mate

[M 750K6]

Have you ruled out the regulators being the cause?

[HondaMan]

Have you ruled out the regulators being the cause?

Yes. This is a physical problem, not an electrical-circuit one. It's always been this way, with the CB500 first. I was a little disappointed when Honda brought out the 550 version with the new engine size to call attention to the transmission updates, but left the alternator out of the upgrades.

It's also the reason we sometimes see a 550 that doesn't have much electrical trouble with low voltage: those got a better rotor, I'd bet on it. Every now and then I've seen the 'good' ones on cranks during a rebuild, but they are not in the majority. Mostly these show up on the 1976 - 1978 bikes, but I have seen a couple on the earlier ones (but never on a CB500 or even a 550K1/2).

[MauiK3]

This will be very interesting