MEP-804A Diode Ring Destroyed

[Evvy Fesler]

Where are you working? Inside or out? If inside, and the building is sturdy enough, then you have a quick and dirty way. Ring in the roof and a come along/chain fall.

Evvy, you're too quick... I was typing the same thing only cheap harbor freight chain fall instead of come-along....

I like the chain fall idea!

 

[Evvy Fesler]

Where are you working? Inside or out? If inside, and the building is sturdy enough, then you have a quick and dirty way. Ring in the roof and a come along/chain fall.

It’s under a car port that’s made like a pole barn with structural IJoists/rafters, not trusses. I’m positive one can handle it let alone use a stretcher across several.

 

[Guyfang]

There you go!

 

[FLCarguy]

This was a very expensive learning exercise. I think I'll use both lock washers AND thread lock compound.

I know they make thread lock up to 600 degrees, I am not sure it would get that hot in that area unless the bearing failed. I will be posting my tragic findings at the end

 

[FLCarguy]

Phase II

I still haven't decided about replace vs rewind, but no matter what, I've got to get the generator out of the cabinet. My generator set is mounted on a military trailer. I've got a couple of options. Tow it to one of you who live in NC, or take it out myself with Bob's help. I'm wondering if an engine hoist will reach in there with the trailer A-Frame in the way. I'll have to buy the hoist ao I can't just try it and see.

What do y'all think? Does anyone have experience with removing and reinstalling the generator? Would you please share your expertise with me?

Evvy-

I have a two ton hoist and mine is mounted the same way, on a trailer, my engine hoist will go right in there over the generator housing, I tried it today, but hopefully I don't need to pull it all the way. Did you test the windings to see if they are damaged? Or are they obviously cut?

 

[FLCarguy]

Sooooooooo,......... Looky, Looky, Looky what I found with the help of Kurt Klopp and the TM tests. It appears at first glance that my windings are ok, but nicked the paint for sure. I will have to repair the wires that come out to the diode assembly as two of them got ripped.

 

[FLCarguy]

Sooooooooo,......... Looky, Looky, Looky what I found with the help of Kurt Klopp and the TM tests. It appears at first glance that my windings are ok, but nicked the paint for sure. I will have to repair the wires that come out to the diode assembly as two of them got ripped.

And just for some history before everything went to hell, I would run this once a month and put my whole house load on it every other month. It did get hit by lighting (not running) but obviously that was not the only thing that happened. Mine also looks like loose bolts causes a chain reaction of disaster. I do wonder however that when mine was in OverSpeed if that made this sketchy setup fail quicker. It was not in it for long but it did rev pretty high until the fault.

 

[Evvy Fesler]

I have a two ton hoist and mine is mounted the same way, on a trailer, my engine hoist will go right in there over the generator housing, I tried it today, but hopefully I don't need to pull it all the way. Did you test the windings to see if they are damaged? Or are they obviously cut?

The excitor rotor is toast, but its stator and the main gen rotor and stator are okay. Rewinding the exciter stator appears to be affordable.

Now to get it out! Thanka for the info re hoist. They’re cheap enough to buy and use, but expensive to buy and not use!

 

[Evvy Fesler]

The excitor rotor is toast, but its stator and the main gen rotor and stator are okay. Rewinding the exciter stator appears to be affordable.

Now to get it out! Thanka for the info re hoist. They’re cheap enough to buy and use, but expensive to buy and not use!

LOL ignore the above! I’m in the wrong thread but it looks like we’re working the same problem!

BTW, the red paint indicates that it has been rewound or repaired. The original, according to Marathon Electric, should be green. Does this matter? Nope… as long as the windings ohm out properly you are good to go. Be sure to buy a rectifier assembly that’s legit. Marathon has a replacement part that I’m going to try. Pricy at $300, but I don’t want to do this work twice.

 

[Evvy Fesler]

Sooooooooo,......... Looky, Looky, Looky what I found with the help of Kurt Klopp and the TM tests. It appears at first glance that my windings are ok, but nicked the paint for sure. I will have to repair the wires that come out to the diode assembly as two of them got ripped.

Peter’s theory is that the rivets gave out. Your pic very much supports his theory. Makes me more confident that I’ll want to buy the Marathon part. Whoever made that one… it’s a loser.

 

[Evvy Fesler]

I know they make thread lock up to 600 degrees, I am not sure it would get that hot in that area unless the bearing failed. I will be posting my tragic findings at the end

It won’t get hot enough. Even heated up it still provides resistance to the nut being removed. The downside is that it can be hard to get thwm out, but I’d rather deal with a secure mechanical connection than a messed up electrical connection.

 

[Evvy Fesler]

Good morning mechanically inclined! Is is okay to use an impact wrench to remove the bolts around the engine bell (transmission) housing? Should I use a torque wrench to reinstall? Is one type of torque wrench better than abother?

 

[Guyfang]

I normally used an impact wrench to remove the fasteners. I only used a torque wrench to do Turbine gen sets. But would say you can use a torque wrench putting fasteners back on. In the military, we always had VERY good torque wrenchs. Snapon, for instance. After my stink as a contractor, that what I have. I spent a little money every year "Up-grading". Do not buy one at K-Mart. But you do not need a Snapon, unless you are doing lots of work requiring you to Torque things. For us, tight was tight. We did use a Loctite. Not "MAN MOUNTAIN DEAN" Loctite. You may need to get back in there one day. The same with the fan bolts in the main gen. Mostly they are a wrench job anyway. But I always used new bolts, and Loctite. Once again, on a Turbine, we used a torque wrench. First off, there was room to get one on. Second, that was one place you wanted to know was TIGHT. Several times over the years, I have found main gens where the bolts fell out of the fan coupler. Not funny.

 

[Guyfang]

I am getting old............................ Should have remembered I had this. Oh well, shoot me at day break.

 

[Evvy Fesler]

I normally used an impact wrench to remove the fasteners. I only used a torque wrench to do Turbine gen sets. But would say you can use a torque wrench putting fasteners back on. In the military, we always had VERY good torque wrenchs. Snapon, for instance. After my stink as a contractor, that what I have. I spent a little money every year "Up-grading". Do not buy one at K-Mart. But you do not need a Snapon, unless you are doing lots of work requiring you to Torque things. For us, tight was tight. We did use a Loctite. Not "MAN MOUNTAIN DEAN" Loctite. You may need to get back in there one day. The same with the fan bolts in the main gen. Mostly they are a wrench job anyway. But I always used new bolts, and Loctite. Once again, on a Turbine, we used a torque wrench. First off, there was room to get one on. Second, that was one place you wanted to know was TIGHT. Several times over the years, I have found main gens where the bolts fell out of the fan coupler. Not funny.

Good morning (our time) Guy!

I like to buy good tools and don’t mind spending good money on them. I’m able to look at my tool collection and remember back 40+ years when I bought them!

My dilemma these days is that I rarely need to buy a tool so the brands that are on the shelf aren’t familiar. I suppose I can choose by paying middle of the road prices, which at this stage of my life are probably good for my remaining years.

I’m intrigued by your comment that you replace bolts. This is another challenge, I think, because bolts on the market these days aren’t the best quality.

USA readers as well as Guy, where are you buying good quality bolts and other similar hardware?

 

[Guyfang]

My all time favorite was a cordless impact that I dug out of the trash, in Schweinfurt. With case and two batteries to go along with it. Made by Dewalt, (I believe Dewalt was bought by Bosch?) it is long out of production. But what a great tool.

The TM tells you to replace the lock washers anyway, and we found that often, the Bolts were over tightened also. It was just cheap insurance for us. It also give torque spec's in the MEP-804A book, so you should use a torque wrench.

Back in 1991-1992, for the MEP-004A, I sent a bunch of bolts to TACOM, Troop Support Command, (Long gone to be replaced by CECOM) and they sent them to the lab. Most if not all were at least slightly over tightened. Everyone just HAS TO make it, that little bit tighter. It just made sense to me to change both.

One reason we always, took the WHOLE package, (main gen hooked to engine) out of the gen housing is simply easier to work on it. And we found that we had less damage to the set that way. And we found it was easier to mate the two up, outside the set.

Most folks do not do that, but we learned if you want fast, it had to be done smart. We changed over 40 gen sets main seals, front and rear in two months. Its the same amount of work to pull it out for seals, or a main gen. I will admit, I had two Thugs, that could pull the pack out in about 3 hours, start to finish. And it was not a hack job. They only had the tools that they knew they needed, and unhook the stuff that the knew had to be unhooked. The only "extra" work was draining the coolant.

The MEP-804A TM tells you to separate the pack in the set. If its your first time, do it that way. And hope you never have to do it again. Its not hard, nor rocket science. We had a bit of experience, that most folks in the forum will never see. My Thugs to rip it out. One crew to do the repair. And my Thugs to put it back in. Poetry in motion.

I cant help you on where to buy fasteners. I live on the wrong side of the big water.

 

[Evvy Fesler]

Love, love your insight and willingness to share!

 

[FLCarguy]

I am getting old............................ Should have remembered I had this. Oh well, shoot me at day break.

That is a handy drawing! Thank you!

 

[FLCarguy]

I have found a 2mm slab of carbon fiber on Amazon for pretty cheap so I am going to order new diodes and try to fab the ring out of the carbon fiber. I have read some white papers about carbon fiber becoming conductive in high magnetic fields with high voltage but I have seen it used in electric motors before so I am willing to give a shot. I will post updates on how it goes.

 

[Ray70]

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!