MEP-804A Diode Ring Destroyed

[Evvy Fesler]

You can get bolts from places like McMaster Carr, I used to get locally at Warwick Industrial Fasteners.
But to tell you the truth, Tractor Supply is also a good place. They carry a full range of grade 5 and grade 8 coarse thread.
If you need Metric or fine thread you may need to search on-line or if you have a good old school family hardware store near by, .... not the big box, grade 3 ( at best ) melted down scrap metal bolts from China!

Thanks, I forgot about McMaster Carr!

 

[Guyfang]

You can get bolts from places like McMaster Carr, I used to get locally at Warwick Industrial Fasteners.
But to tell you the truth, Tractor Supply is also a good place. They carry a full range of grade 5 and grade 8 coarse thread.
If you need Metric or fine thread you may need to search on-line or if you have a good old school family hardware store near by, .... not the big box, grade 3 ( at best ) melted down scrap metal bolts from China!

Haven't looked at the bolts to see what grade they are. Turbine was grade 9!

 

[Evvy Fesler]

Haven't looked at the bolts to see what grade they are. Turbine was grade 9!

No worries. I can either look them up in the parts TM or read their stamps. Probably will do both as you pointed out several messages ago to never trust what another person may have already substituted.

Evvy-

 

[Guyfang]

We could work together.

 

[Evvy Fesler]

Continuing…

I found a generator head at auction in Nevada. From the pictures it looked like it was in good condition. I won and had it shipped to North Carolina. It arrived yesterday where we had the trucking company use a pallet jack to put it on the bed of our pickup truck; they had a lift-gate.

Today we moved the stator and rotor from the pickup to a section of Baker staging. The old head is still in the generator waiting to be removed.

I learned that VeriTread and UShip, trucking quote services encouraged by Ritchie Brothers, are quite expensive. Even the lowest quote is inflated by a couple hundred dollars, presumably broker fees. It’s far cheaper to get your own quotes from big name truckers. The lowest quote via the two websites sponsored by Ritchie Brothers was $460. I got it shipped for $155 via YRC.

Note: I’ve read several posts here where folk were hoping to find the elusive two wires that would allow them to convert this stator to single phase. Now that I’ve had a good look at a disassembled head I can tell you that’s not possible. It simply isn’t designed for single phase. It would have to be rewound and even then the laminations may not support it.

Questions:

How does one insert the rotor into the stator? There’s a jig in the TM, but I don’t have one.

The generator head is affixed to the engine bell housing with a series of bolts that go around the rim in series. I can reach the majority of them with an extension on my socket set. How does one reach the bottom three or four?

Pictures:

 

[Guyfang]

Continuing…

I found a generator head at auction in Nevada. From the pictures it looked like it was in good condition. I won and had it shipped to North Carolina. It arrived yesterday where we had the trucking company use a pallet jack to put it on the bed of our pickup truck; they had a lift-gate.

Today we moved the stator and rotor from the pickup to a section of Baker staging. The old head is still in the generator waiting to be removed.

I learned that VeriTread and UShip, trucking quote services encouraged by Ritchie Brothers, are quite expensive. Even the lowest quote is inflated by a couple hundred dollars, presumably broker fees. It’s far cheaper to get your own quotes from big name truckers. The lowest quote via the two websites sponsored by Ritchie Brothers was $460. I got it shipped for $155 via YRC.

Note: I’ve read several posts here where folk were hoping to find the elusive two wires that would allow them to convert this stator to single phase. Now that I’ve had a good look at a disassembled head I can tell you that’s not possible. It simply isn’t designed for single phase. It would have to be rewound and even then the laminations may not support it. I have been saying this since I joined the forum. People just will not want to believe. You will see this silly question over, and over, and over again. I hate to call it silly, because if its someone new, its not silly. But there are people who will simply not let this issue die. It can not be done.

Questions:

How does one insert the rotor into the stater? There’s a jig in the TM, but I don’t have one. I always bolted the rotor to the engine, and carefully inserted the Stator onto the rotor. Even the Army, doesn't have a jig. Or at least I never saw one. The words, "Take your time!" are to be kept in mind when doing this job. The jig is simple enough to be made, but I would say not worth the time and money to do just one job.

I once saw a few guys who took the Stator, removed the bearing cup, tipped the stater up on its end, slowly let the rotor down into the stater with a ratchet strap, and then when the rotor was in, tipped it back over. Replaced the bearing cup, and then sled the stater/rotor into the set, mated up the flex plate and then the bolts holding the bell housings. It worked for them. I would not do it that way, but who am I to tell someone there way worked, but is wrong? Or better said, "not my way".

The generator head is affixed to the engine bell housing with a series of bolts that go around the rim in series. I can reach the majority of them with an extension on my socket set. How does one reach the bottom three or four? Its not easy. You will learn to use new words that are not to be repeated in church. After doing it a few times, its not all that hard. That's why I simply removed the belt screen, took the mounting bolts out of the flex plate and slide the whole main gen out of the set. Then you have a bit more room to move. Remember when I mentioned removing the box? I always found it much easier to do it that way. Its a bit more work, but I was mostly working alone with a load sound system providing good vibes. If I have not explained this well enough for you to understand what I am saying, bump me and I will try and explain it differently.

I never saw a main gen come this way. It was always put together, with a steal bar bolted across the bell housing and flex plate, so it would not move an inch. This way is much more time consuming.

Pictures:

View attachment 882027
View attachment 882028View attachment 882029View attachment 882030View attachment 882031View attachment 882032

Open to see comments.

 

[peapvp]

“Its not easy. You will learn to use new words that are not to be repeated in church.”

Amen

 

[Evvy Fesler]

“Its not easy. You will learn to use new words that are not to be repeated in church.”

Amen

Ha! I live with a Seabee. He’s already taught me new, but unspeakable, words!

 

[Guyfang]

Peter and I can start you in on German words. The longer I learn this language, the more I find so very interesting words and phrases, that do not translate well into English. But are really fine things!

 

[87cr250r]

Easiest way to put a rotor in a generator is to stand the unit vertically on end and lower the rotor in.

 

[Guyfang]

No. But it is one way. The lifting rig is the easiest way. It still makes me wonder why it came that way. We always received them in one piece. Slide it in. Put the 6 or 8 bolts in the flex plate and tighten them hand tight. Put the 6-8 bolts in all the way around the bell housing , torque em down. Torque the flex plate bolts. Done.

 

[87cr250r]

Most of us have hoists that go up and down but few of our hoists travel. That is why vertical install is easiest.

 

[Guyfang]

The army spoiled me.

 

[Mullaney]

The army spoiled me.

.
Not a lot of folks are willing to say that the Army (Navy, Marines, or even the Air Force) spoiled them.

Exception to that is food in the Navy.
Coffee always on.
No lack of good food.

 

[Guyfang]

I am not talking about my time in the Army. I am talking about my time as a contractor. And, I have to admit, the Army has come a LONG ways since the 70's. You ever worked where light were a real treat? And you had to wear rubber boots 3/4 of the year due to mud? These are pictures of a High Speed, Low Drag, State of the Art, Premiere Air Defence Hawk Missile Site.

Fueling up the Generator tanks with 1200 gal. Diesel. 4 times a week.

The Power Generation Section.


The Motor Pool


My CW3 told me the sites in Nam were better looking. The only permanent building on site was the one hole Latrine.

 

[Evvy Fesler]

I ordered a diode ring from Marathon Electric. I felt that if I was going to go through all of this work, I may as well give myself the best chance of diode ring survival. With that said, we don't know why DOD sourced it elsewhere. It may well be that the OEM part was the lemon. But... it feels more solid in my hand than the alternate source assembly. I now have three assemblies: 1) self-destructed, 2) one attached to the replacement rotor, and 3) OEM replacement. OEM stands for Original Equipment Manufacturer. I noticed something that may have no bearing on the self-destruct mode, but the non-OEM assemblies are mounted on a composite ring, presumably fiberglass. The edge is rather rough suggesting that it was sawn rather than die cut. Also, the rivets, what we assumed were the failure mode (read above), appear to be better swaged on the OEM assembly (edges rolled over).






Swaged edge of rivets not as beefy as OEM part. We suspect that the rivet was the failure mode that caused the ring to break apart.


Swaged edge of rivets not as beefy as OEM part. We suspect that the rivet was the failure mode that caused the ring to break apart.


Nice clean edge suggests die cut


The rough edge suggests the ring was sawed instead of die cut. Of course, it could have gotten roughed up when it broke apart, but if we compare it to the replacement rotor's diode ring they look similar. It's not possible to say that the broken diode ring and the replacement rotor's diode ring were made by the same manufacturer.


This photo was taken of the replacement rotor. I can't yet remove the diode ring because I have to pull the bearing at the end of the shaft. The bearing is supporting the rotor in a wood cradle at the moment so pulling it now would be bad timing.

 

[peapvp]

Chinesium…….

 

[87cr250r]

I run Marathon generators in my fleet. I have 8 that were removed from service at 35000 hours and 14 others currently in service with hours ringing from 3,000-30,000. I have never had a rectifier failure of any type. I did have a stator failure.

With that said, Marathon generators are typically made in China. Perhaps they hand made the rectifier ring here in USA to meet the sourcing requirements for military.

Is it possible this unit was run overspeed? That sure looks like the kind of damage I would expect.

 

[Evvy Fesler]

Part Info:

Desc.: Rectifier Assembly 280 Stud D05 MAC/SER
Part No.: 777079-0A
Mfg: Marathon Electric a/k/a Regal Rexnord
Wausau, WI
Price: $316 USD plus $22.12 shipping

 

[Evvy Fesler]

I run Marathon generators in my fleet. I have 8 that were removed from service at 35000 hours and 14 others currently in service with hours ringing from 3,000-30,000. I have never had a rectifier failure of any type. I did have a stator failure.

Is it possible this unit was run overspeed? That sure looks like the kind of damage I would expect.

It's hard to tell since there isn't any history that came with the set. The one thing that we do know is that the failed assembly wasn't made by Marathon Electric. They confirmed that it didn't carry their markings. Another member, @FLCarguy, posted a similar failure suggesting that it may be common to the mystery diode ring. It's all supposition at this point in time, but the more members, like you and @FLCarguy, who report in, the better our understanding will become.