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evanfrucht
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Joined: July 24, 2016
Posts: 2180
Location: Laurel Canyon, CA
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 Posted: Sat Jul 25, 2020 1:42 pm Post subject: Is this generator armature bad, can someone confirm? W/ PICTURE |
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Picture speaks for itself
I'm kinda bummed I hoped to rebuild this 67 only generator.
Everywhere it says there should be no continuity from commutator to shaft. And if there is any reading, it's junk... IS THAT CORRECT?
How does this even happen, where does it normally short on the shaft. Is it possible to somehow fix it ? There is no physical damage that I can detect anywhere. How did Bosch isolate it from the shaft when they make it ?
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1967 Bug ( the daily rod )
1964 Fury Wagon ( the pavement shredder ) |
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evanfrucht
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Joined: July 24, 2016
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Location: Laurel Canyon, CA
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| Posted: Sat Jul 25, 2020 1:46 pm Post subject: Re: Is this generator armature bad, can someone confirm? W/ PICTURE |
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That is 2.4 MILI-OHMS or 0.0024 OHMS (little m before the ohms symbol.) I have an new multimeter that sets the measuring range automatically. Is that reading so low that it's fine/normal? I'm lost here.
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Big Al
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Joined: June 14, 2014
Posts: 184
Location: Tucson, AZ
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| Posted: Sat Jul 25, 2020 1:57 pm Post subject: Re: Is this generator armature bad, can someone confirm? W/ PICTURE |
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Your reading continuity between the shaft and windings. That just one test and that one is good.
The proper way to test that armature is with a growler, something most don't have.
https://en.wikipedia.org/wiki/Growler_%28electrical_device%29
You need to find a shop with a growler or check in the generator.
Al |
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evanfrucht
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Joined: July 24, 2016
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Location: Laurel Canyon, CA
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| Posted: Sat Jul 25, 2020 2:08 pm Post subject: Re: Is this generator armature bad, can someone confirm? W/ PICTURE |
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Ok, so that one test is good? I was unsure if .002 amps counted as "no continuity."
All the other cave man multimeter tests check out.
Thats part of why I was confused. I know these tests are not exactly the proper way to test ( growler )
Unfortunately I don't have a growler
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Dale M.
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Joined: April 12, 2006
Posts: 20377
Location: Just a tiny bit west of Yosemite Valley
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| Posted: Sat Jul 25, 2020 2:08 pm Post subject: Re: Is this generator armature bad, can someone confirm? W/ PICTURE |
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| evanfrucht wrote: |
| That is 2.4 MILI-OHMS or 0.0024 OHMS (little m before the ohms symbol.) I have an new multimeter that sets the measuring range automatically. Is that reading so low that it's fine/normal? I'm lost here. |
Umm it meg ohms, meaning "million" ....2.54 million ohms...
Dale
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Big Al
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Joined: June 14, 2014
Posts: 184
Location: Tucson, AZ
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| Posted: Sat Jul 25, 2020 2:20 pm Post subject: Re: Is this generator armature bad, can someone confirm? W/ PICTURE |
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Let me try to answer your question. You are seeing a very tiny current path between the windings and the shaft. 2.54 million Ohms is for practical purposes nothing. You usually make that test with 120 volts and a 15 Watt light bulb. If you have an old AC cord you can make a tester. Just be careful when you use it, I do it all the time and am still alive:)
Separate the wires and hook a light bulb between one wire and the commutator. The other to the shaft. Any wattage regular light bulb will work. You can even use a table lamp, just hook one wire from the suicide cord, that what I call mine, to the shaft. The other to one side of the lamp's plug, clip lead from the other side to the commutator. If you connect it right the light bulb will light up if you short the wires together.
Keep one hand in your pocket so we don't hear about it:)
Not exact but you can get the idea.
https://www.youtube.com/watch?v=zrbxpUfa27U
You would place the armature between his two test posts.
The reason you use 120 Volts and not a much safer 12 Volts is you're testing the quality of the insulation between the windings and the metal of the armature. The higher voltage puts more stress on the insulation.
Al |
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evanfrucht
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Joined: July 24, 2016
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Location: Laurel Canyon, CA
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| Posted: Sat Jul 25, 2020 2:21 pm Post subject: Re: Is this generator armature bad, can someone confirm? W/ PICTURE |
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| Dale M. wrote: |
| evanfrucht wrote: |
| That is 2.4 MILI-OHMS or 0.0024 OHMS (little m before the ohms symbol.) I have an new multimeter that sets the measuring range automatically. Is that reading so low that it's fine/normal? I'm lost here. |
Umm it meg ohms, meaning "million" ....2.54 million ohms...
Dale |
That just my incorrect vocabulary...
I meant to say milliohms
1 milliohm = .001 ohms... if my research is correct
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evanfrucht
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Joined: July 24, 2016
Posts: 2180
Location: Laurel Canyon, CA
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| Posted: Sat Jul 25, 2020 2:22 pm Post subject: Re: Is this generator armature bad, can someone confirm? W/ PICTURE |
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| Big Al wrote: |
Let me try to answer your question. You are seeing a very tiny current path between the windings and the shaft. 2.54 million Ohms is for practical purposes nothing. You usually make that test with 120 volts and a 15 Watt light bulb. If you have an old AC cord you can make a tester. Just be careful when you use it, I do it all the time and am still alive:)
Separate the wires and hook a light bulb between one wire and the commutator. The other to the shaft. Any wattage regular light bulb will work. You can even use a table lamp, just hook one wire from the suicide cord, that what I call mine, to the shaft. The other to one side of the lamp's plug, clip lead from the other side to the commutator. If you connect it right the light bulb will light up if you short the wires together.
Keep one hand in your pocket so we don't hear about it:)
Not exact but you can get the idea.
https://www.youtube.com/watch?v=zrbxpUfa27U
You would place the armature between his two test posts.
The reason you use 120 Volts and not a much safer 12 Volts is you're testing the quality of the insulation between the windings and the metal of the armature. The higher voltage puts more stress on the insulation.
Al |
That just basically answered all my questions and cleared it up for me. Thank you!!!
I simply have disassembled it and soda blasted all parts. I plan to replace brushes and bearings. I stuck it in my drill press and cleaned up the commutator surface with a fine flat file followed by some 400 grit sandapaper. Its still well above 32.9 mm in diamter which as far as I know is the wear limit spec. Mine after cleaning up is about 35mm
Basically I dont have much invested so I plan to test as well as I can with what I have, and then test if its working with an electric drill once assembled.
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1964 Fury Wagon ( the pavement shredder ) |
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Big Al
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Joined: June 14, 2014
Posts: 184
Location: Tucson, AZ
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| Posted: Sat Jul 25, 2020 2:31 pm Post subject: Re: Is this generator armature bad, can someone confirm? W/ PICTURE |
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| Big Al wrote: |
Your reading continuity between the shaft and windings. That just one test and that one is good.
The proper way to test that armature is with a growler, something most don't have.
https://en.wikipedia.org/wiki/Growler_%28electrical_device%29
You need to find a shop with a growler or check in the generator.
Al |
If you looked at the picture on Wikipedia of a growler, the big light bulb is for the continuity tests we're talking about.
Al |
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Dale M.
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Joined: April 12, 2006
Posts: 20377
Location: Just a tiny bit west of Yosemite Valley
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| Posted: Sat Jul 25, 2020 2:36 pm Post subject: Re: Is this generator armature bad, can someone confirm? W/ PICTURE |
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| evanfrucht wrote: |
| Dale M. wrote: |
| evanfrucht wrote: |
| That is 2.4 MILI-OHMS or 0.0024 OHMS (little m before the ohms symbol.) I have an new multimeter that sets the measuring range automatically. Is that reading so low that it's fine/normal? I'm lost here. |
Umm it meg ohms, meaning "million" ....2.54 million ohms...
Dale |
That just my incorrect vocabulary...
I meant to say milliohms
1 milliohm = .001 ohms... if my research is correct |
You are at the wrong end of spectrum Milli is not million, ... You are measuring millions of ohms....
One meg = 1,000,000.000 Ohms...
Your meter is telling you 2,540,000.000 ohms...
Note decimal point(s)....Milli would be to right of decimal point
Dale
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“Fear The Government That Wants To Take Your Guns" - Thomas Jefferson.
"Kellison Sand Piper Roadster" For Street & Show.
"Joe Pody Sandrover" Buggy with 2180 for Autocross (Sold)
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EVfun
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Joined: April 01, 2012
Posts: 5473
Location: Seattle
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| Posted: Sat Jul 25, 2020 2:54 pm Post subject: Re: Is this generator armature bad, can someone confirm? W/ PICTURE |
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That meter wasn't displaying mΩ, it was displaying MΩ.
Not millionths of an ohm but millions of ohms.
Not many digital multimeters can measure milliohms. Almost all of them can measure megohms. That armature is fine.
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Last edited by EVfun on Sat Jul 25, 2020 3:17 pm; edited 1 time in total |
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evanfrucht
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Joined: July 24, 2016
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Location: Laurel Canyon, CA
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| Posted: Sat Jul 25, 2020 3:02 pm Post subject: Re: Is this generator armature bad, can someone confirm? W/ PICTURE |
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Ok now I get that. I didn't realize the capitalization meant anything
I'm even more confused now as to whether the armature passed that test?
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Krochus
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Joined: January 01, 2017
Posts: 892
Location: NW Arkansas
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| Posted: Sat Jul 25, 2020 3:08 pm Post subject: Re: Is this generator armature bad, can someone confirm? W/ PICTURE |
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2 megaohms from the 9 volts of a meter is actually pretty low in the grand scheme of things for resistance to ground. Hand held ohmmeters really aren’t well suited to checking insulation condition.
For example our pass criteria at work for dc armatures is 100megaohms at 500v on a dc megaohmmeter
Wash it with dawn soap and water. Then bake it at 220 degrees vertically com end up for 6 hours. It’ll probably read infinity afterwards
Now if you really want to test it check resistance bar to bar then work out the imbalance percentage
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evanfrucht
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Joined: July 24, 2016
Posts: 2180
Location: Laurel Canyon, CA
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| Posted: Sat Jul 25, 2020 3:14 pm Post subject: Re: Is this generator armature bad, can someone confirm? W/ PICTURE |
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| Big Al wrote: |
Let me try to answer your question. You are seeing a very tiny current path between the windings and the shaft. 2.54 million Ohms is for practical purposes nothing. You usually make that test with 120 volts and a 15 Watt light bulb. If you have an old AC cord you can make a tester. Just be careful when you use it, I do it all the time and am still alive:)
Separate the wires and hook a light bulb between one wire and the commutator. The other to the shaft. Any wattage regular light bulb will work. You can even use a table lamp, just hook one wire from the suicide cord, that what I call mine, to the shaft. The other to one side of the lamp's plug, clip lead from the other side to the commutator. If you connect it right the light bulb will light up if you short the wires together.
Keep one hand in your pocket so we don't hear about it:)
Not exact but you can get the idea.
https://www.youtube.com/watch?v=zrbxpUfa27U
You would place the armature between his two test posts.
The reason you use 120 Volts and not a much safer 12 Volts is you're testing the quality of the insulation between the windings and the metal of the armature. The higher voltage puts more stress on the insulation.
Al |
I'm going to forget that fancy multimeter for now and use (make) the correct tool for the job... will get back with results. Thanks
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earthquake
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| Posted: Sat Jul 25, 2020 3:20 pm Post subject: Re: Is this generator armature bad, can someone confirm? W/ PICTURE |
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Find a electric motor repair shop near you, they should be able to test it for you.
I have never seen a EM repair shop that does not have a growler.
eQ
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EVfun
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| Posted: Sat Jul 25, 2020 3:24 pm Post subject: Re: Is this generator armature bad, can someone confirm? W/ PICTURE |
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That is only 6 microamps of current at 15 volts. That is fine in a brushed DC motor or generator. I see no cause for concern yet. Next, don't scratch up those commutator segments but check from one to the next around the commutator. Your looking for an open winding. That would also fail the commutator.
To out 6 microamps into perspective a dim tiny LED is drawing around 2000 microamps. You car battery is self-discharging at around 1000 microamps if it's in nearly new condition.
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| Wildthings wrote: |
| As a general rule, cheap parts are the most expensive parts you can buy. |
Last edited by EVfun on Sat Jul 25, 2020 3:31 pm; edited 1 time in total |
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evanfrucht
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Joined: July 24, 2016
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Location: Laurel Canyon, CA
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| Posted: Sat Jul 25, 2020 3:26 pm Post subject: Re: Is this generator armature bad, can someone confirm? W/ PICTURE |
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| earthquake wrote: |
Find a electric motor repair shop near you, they should be able to test it for you.
I have never seen a EM repair shop that does not have a growler.
eQ |
The problem is I dont really have any budget for this so I'm trying to avoid paying a shop. I also dont really want to go driving around searching for someone who will test it for free.
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Big Al
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evanfrucht
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| Posted: Sat Jul 25, 2020 3:45 pm Post subject: Re: Is this generator armature bad, can someone confirm? W/ PICTURE |
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| EVfun wrote: |
That is only 6 microamps of current at 15 volts. That is fine in a brushed DC motor or generator. I see no cause for concern yet. Next, don't scratch up those commutator segments but check from one to the next around the commutator. Your looking for an open winding. That would also fail the commutator.
To out 6 microamps into perspective a dim tiny LED is drawing around 2000 microamps. You car battery is self-discharging at around 1000 microamps if it's in nearly new condition. |
I did 2 other tests. One where you check each of the commutator bars that are 180 degress opposite each other. And one where you check the ones next each other.
180 test showed 0.2 ohms all around
The other test showed mostly 0.0 ohms bug some 0.1 ohm
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evanfrucht
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| Posted: Sat Jul 25, 2020 3:51 pm Post subject: Re: Is this generator armature bad, can someone confirm? W/ PICTURE |
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Its not a charging issue im having or ever had. This generator probabaly never got to point of actually failing. I think it was just on an engine that seized....
Heres the quick story
I'm in the middle of building a 2180 to pop into my 1967 bug.This generator came with the frozen engine that I bought for the case and other parts for my build. ( very strange coincidence because its a 1971 engine )
I thought it would be neat to rebuild it and use it on the engine since my car is a mostly original 1967 bug.
I have no idea if it worked when that engine was pulled becuase i bought the engine as a core BUT I would guess it was in fine working order since I found the engine to have failed from a seized/spun rod bearing. It doesnt look like there was much brush wear to the commutator, when I compare mine to the specs and pictures of other ones people have deemed usable.
On a side note i actually have another 67 only generator that was on the original engine for my car ( i have the original matching numbers engine stored away ) while i was still driving around the original rngine that generaror stopped charging so I just bought a rebuilt bosch at the time for quick fix
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