Model 51 Generator information

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knucklewarren
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Model 51 Generator information

#1

Post by knucklewarren » Thu Mar 23, 2017 4:21 pm

I have a complete model 51 fan cooled generator and am trying to understand more about it. My internet searching is not turning up much information about this generator. Can anyone share a link or any other information about this generator so I can properly understand it? Additionally, I don't seem to find any information about replacement parts for it. Any suggestions are greatly appreciated.
My thought is to potentially use this in my servicar project.

Thank you in advance.
-Warren



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Re: Model 51 Generator information

#2

Post by RUBONE » Thu Mar 23, 2017 4:41 pm

Use the knowledge base and documentation sections of this forum.

http://www.hydra-glide.net/joomla/index ... -generator

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Re: Model 51 Generator information

#3

Post by Frankenstein » Tue Mar 28, 2017 1:24 am

These are an interesting option in the harley generator lineup. I became interested in these several years ago and have been experimenting with them since.
I presently convert them to 12 volt operation by the use of 65A field coils and have found them to produce the highest reliable power output of any of the harley gennys. More than a 65A
They are rated to deliver 15 amps at a nominal 6 volts in factory form. They can safely deliver that same 15Amps at 12 volts as well.
Because of the fan built into the unit, the armature can deliver a higher amperage and not overheat.
Here's what I've seen as the down side on these gennys.
The whole fan ass'y on the end of the armature is the source of most problems. The three shroud screws can loosen, let things move too much and then the Aluminum "spider" that they screw into can break. Also burrs can develop while they are loose and then the shroud can be difficult to remove and careless hands can cause breakage of the spider in removing the shroud when servicing.
The Fan itself can loosen on the armature shaft, loosen the hole in the center of the fan, making it difficult or impossible to keep the fan securely tightened on the shaft.
I've seen some armatures cut with a keyway, but never found a unit where a key was installed. Maybe an idea that looked good on paper, but didn't work out in the real world.
The ratcheting drive gear is a trouble free unit, at least in my experience, but if you don't have one, finding those parts can be difficult, at least, in my wanderings at the swap meets.
Just a warning,the gear grinding noise they can make when you shut down the engine can be a little unnerving when you first hear it :D
Final analysis, they are overall a rugged mechanical and electrical unit, except as noted, and I wouldn't hesitate to give it a try.
The expendable parts are the same as used in the 32E, ie, Bearings and seal.
I add small pieces of air cleaner foam under the two cooling slot shrouds to help keep grit out of the genny.
I used the extra power of the unit on my 65Pan to power up electric gloves when I rode to Daytona a couple of years ago. Along with the 100W quartz headlight. Couldn't have done it without warm hands.
DD

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Re: Model 51 Generator information

#4

Post by lrcormier » Mon Jan 27, 2020 7:10 pm

Frankenstein, I'm curious about the 51 conversion to 12v. Is all that needs to be done is change the field windings. Someone on the antique motorcycle forum said that I need to change/rewind the armature also? I have a model 51 generator although someone removed the cooling fan part and fitted the smooth end cap on it.

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Re: Model 51 Generator information

#5

Post by Frankenstein » Tue Jan 28, 2020 12:59 am

Ircormier,
The short answer is yes, all you need do is change the fields. They make an armature "12" volts by using more, thinner wire in the armature windings. More to come on that subject.
Here is the science:
The voltage a generator produces is related to the strength of the magnetic field the armature rotates through,
(created by the fields)
the speed at which the armature rotates,
and the number of turns (pieces of wire) in the winding that is passing through the magnetic field.
Other factors that come into play in building a generator is the size (gauge) of the winding is made with.
heavier(thicker) wire can carry more current with less loss due to heating the winding.
Skinny wire has more resistance to current flow and will glow like an electric heater if taken to an extreme. :D
Ok, now Harley generators in particular.
Harley 6 volt generators are designed to create 6 volts at a fast idle, say 8 or 900 rpm's HD picked a wire size and number of turns per winding to make that voltage with the magnetic flux (magnetism) that the fields are producing. You've all seen drawings of a bar magnet with dotted lines running from the north pole to the south, the lines represent flux. Enough on that.
Suffice to say, Harley designed the generator from the ground up so that the armature would have heavy enough wire not to overheat, but at the same time enough turns in the windings to handle 10 amps of output current at normal engine speeds. Fact is, they were conservative in their design to where it would easily do better than that and not hurt itself.
That's basically the 32E design and the 2 brush 52.
Along comes the police dept's and their radios, and they needed more power.
HD's solution was the 32E2R, a longer bodied, same diameter as the 32E. This was good for 15 amps, but was pushing the limit of thermal safety. The result was the Fan cooled generators, like the Model 51 and 58R. With cooling slots and the fan to draw in cooling air, they were go for 20 amps, reliably.
O.K, O.K, what about this 12 volts from a basically 6 volt generator?
As any one who's lost the ground on their 6 volt 3 brush system, where the battery is the only thing limiting voltage in the system, those 6 volt generators will make lots more than 6 volts as the rev's go up.
Fact of the matter is, that at about 1200 or so rev's, any of these 6 volt generators will be making 12 volts, and at normal operating speeds, the 32E wired as a 2 brush will easily supply enough current at 12 volts to run your basic electrical system.
The use of the 65A fields in the conversion to 12 volts gives you a more efficient winding to power the generator's magnetic field. It draws less current and produces at least the equal to the magnetic field the old 6 volt field windings. ( By the way, there is a limit to the amount of magnetism you can get out of a coil of wire wound as a magnet. I.E, past a certain point, more current through the field won't give you any more magnetism.
From my experimenting it would appear the 65A field is an improvement in field winding efficiency. Just a side note)
In summary, the heavier wire used in the 6 volt armatures is more robust that the thinner wire used in the 65A genny and is less prone to burnout than a 65A generator. The only thing you give up is that the cut in speed(when charging voltage is obtained) is somewhat, maybe 3-400 rpm higher than a "12" volt wound armature.
I do want to express one more opinion here. The 65A generator was a hot rodded, souped up rework of the reliable 6 volt generators HD had been making for years. They did this by using more thinner wire in the armature windings. They had a problem, namely electric starting, and they did what they had to do to solve it.
Now, in spite of all I've said, I want to emphasize that the Cycle Electric 12 volt generators with built in voltage regulators are a fine, reliable piece of equipment. Cycle Electric, in incorporating the regulator into the generator itself, is able to monitor and prevent overheating with the built in regulator. It's a good solution to the 65A's potential weakness.
Done.
DD

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Re: Model 51 Generator information

#6

Post by lrcormier » Tue Jan 28, 2020 4:34 am

Wow, that was way more information then I expected, I was an electronics tech in the NAVY but that was a lesson in electrical engineering. The guy rebuilding my 52 panhead engine said he can convert my generator to 12v but said it's expensive, haven't actually talked cost yet but it's likely the cost involves a kit that changes the armature and fields, so when I came across your post that got me curious. I found a place to buy NOS 65a fields for 125 dollars. But then there is also the cost of a good voltage regulator. Someone in another forum replied to my query about converting my model 51 to 12v by only changing the field windings and his reply was that it is more involved than that and would also involve rewinding the armature. I've looked at the cycle electric generators, I'm confused as to which dgv-5000 I would need and it looks like the cost would be about 400. I've got time to ponder which way to go and appreciate your reply and input.

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Re: Model 51 Generator information

#7

Post by RooDog » Tue Jan 28, 2020 4:52 am

The cycle electric site can be a little intimidating, but if you eliminate the products you absolutely do not need then there are only about three that will suit your needs, actually more like two if you are not using an electric starter. A call to CE should clear up any questions about what you need. I am using one on my '68 FL with E Start and a FXE battery....
....RooDog....

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Re: Model 51 Generator information

#8

Post by Frankenstein » Tue Jan 28, 2020 4:18 pm

Sorry I got a little long winded, but you may have noticed by now that I've got a "thing" for generators.
It just irks me to see people being mislead into thinking they must use a "12volt" armature to convert their 6 volt genny. There's just no good reason to do so.
Ircormier, you have a PM
DD

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Re: Model 51 Generator information

#9

Post by RooDog » Tue Jan 28, 2020 4:37 pm

DD...
This is all good info you are offering, but...
Unless one has the parts readily available, read cheap, what's the point in converting a 6V genny to 12V. Considering parts AND LABOR, the cost approaches what an actual new 12V genny would cost. Yes I know a CE genny has a high list price, but a little creative horse trading can bring that down to a reasonable level. Or maybe one could score the Japanese Hitachi 65-B genny. It features ball bearings on both ends of the armature, and solid state regulation. There are just so many ways to get to the 12V goal, And it's good to know it can be done by swapping OEM parts, but this is not for everyone. And there are so many owners now these days that don't seem to know which end of a hammer the Phillips bit fits.
Best Wishes....
....RooDog....

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Re: Model 51 Generator information

#10

Post by Frankenstein » Tue Jan 28, 2020 4:48 pm

RooDog,
Right you are, As my Old boss used to say, " Leroy, get away from that wheelbarrow, you know you don't know Nuttin' 'bout machinery!" He was a W Virginia boy though, and it just isn't the same in print as it was with his 'twang. :D

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Re: Model 51 Generator information

#11

Post by cant-drive-55 » Sun Apr 05, 2020 10:44 pm

Frankenstein, I bought a 51 gen. It's very dirty. The 2 screws holding the Gen together are stuck. Tried penetrating oil and other things. Any secrets? I may have to drill these out. Need to clean it up and test the armature.

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Re: Model 51 Generator information

#12

Post by Frankenstein » Mon Apr 06, 2020 1:56 am

It's steel into aluminum at the far end of the genny. Use all your favorite tricks, Impact screwdriver custom fitted bit, heat at the aluminum housing where the through bolts screw in, etc. The bolts are longer than 32E and don't grow on trees.
Last ditch, soak in original Coca-Cola for a couple of days. No imitations, original Coke. Very effective penetrant.
Good luck!
DD

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Re: Model 51 Generator information

#13

Post by RooDog » Mon Apr 06, 2020 1:15 pm

RE: Coca-Cola
Read the label, be sure it lists Phosphoric Acid, that the active ingredient, for us in this app....
....RooDog....

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Re: Model 51 Generator information

#14

Post by Buddhahoodvatoloco » Mon Apr 06, 2020 2:03 pm

PEPSI
PEPSI
:lol: :lol:

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Re: Model 51 Generator information

#15

Post by cant-drive-55 » Mon Apr 06, 2020 3:32 pm

Got the screws out. Lots of oil and careful use of a impact wrench. Tough time separating gen sections.

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