MEP-804A Diode Ring Destroyed

[Mullaney]

I heated and cooled and sprayed with penetrating oil. I did it again and let it sit overnight. This afternoon, I put the LAP over the breaker bar and there... it moved. Just a little, but it moved. I did it again, and again and again. Maybe a quarter turn at a time. It was moving! After about 50 times it occurred to me that maybe there's a nut under there somewhere. I looked under and up. Nope. I tried some more. That's when I noticed three nasty bolts in the skid rail. Now... where in the directions did it say... remove these bolts? You know bolts 1, 2 and 3 and their cousins on the other side 4, 5 and 6? Potty mouth... so I've come to the conclusion that not only do men have trouble asking for directions apparently @Guyfang has trouble giving directions. And really, why does this generator set need forklift shields? Can't y'all run your fork into the hole and straight through? And what do y'all do with said bolts 1 - 6? Is it enough that you torque them to high heaven? Noooo, you gotta put six coats of paint on them. Sheesh! Metric wrenches came in handy on these American standard bolts.

I was just so mad at myself for not picking up on that detail in the TM. Once I got the the forklift shield off, there they were: two shiny nuts. There was good news too. There was a clear shot to them where I could use my impact wrench. Had I finally caught a break? Nope. They wouldn't budge, At this point I began to worry that if I ever got them off I would never be able to torque the replacements because my torque wrench doesn't have a sumo wrestler setting. Grrr....

This is where I sinned. I'm sorry @Guyfang, I know you told me never to use this tool. But I broke down just this once.

View attachment 883559

Yes, yes, I admit it. I used a vise grip to keep the nut from spinning. Eeek...

View attachment 883560


I'm so durned proud of myself!

.
I believe there is a special exception granted for the use of Vice Grips on bolts or nuts that will be trashed after removal.

 

[Guyfang]

Just like at home. No matter what, I am at fault.

 

[Evvy Fesler]

Just like at home. No matter what, I am at fault.

Surely then, you must know that you are loved!

 

[Guyfang]

The Great B.B. King, used to sing a little ditty called, "No one loves me but my Mother, and she could be jiven too".

 

[Ray70]

Hi Evvy, were those bolts 3/8" or 7/16"? They look relatively small in the picture so I'm surprised your impact wasn't up to the challenge.
It looks like you have lock nuts on there, but still shouldn't have been that big of a deal for a decent impact.
However, from experience I know there are several items that all contribute to "weakening" the available torque from your wrench.
Were you using an extension and / or a universal joint? Both of these will greatly reduce the force an impact will effectively deliver.
Also, applying the impact force to the bolt rather than the nut tends to reduce the effectiveness also because the bolt's shank will twist slightly and absorb some of the force
and lastly I see a 12pt. chrome socket in the background, this is also somewhat of a bad idea if you used it on your impact. The chrome sockets often can't handle the power of a good impact wrench ( and may split open ) and 12pt's tend to slip ( vibrate back and forth ) more on the hex and you will loose a little bit of power through this slight movement. So... all combined, this could be the reason your impact couldn't cut the mustard!
I'm not looking to be critical, but rather I sense you have an obvious desire to learn at every possible opportunity, so I wanted to pass on some of my past experiences.

 

[Guyfang]

I think this is the tech data for the bolts.

	THREAD CLASS	2A
	THREAD DIRECTION	RIGHT-HAND
	THREAD LENGTH	1.500 INCHES MINIMUM AND 1.727 INCHES MAXIMUM
	FASTENER LENGTH	4.656 INCHES MINIMUM AND 4.750 INCHES MAXIMUM
	HEAD STYLE	HEXAGON
	HEAD HEIGHT	0.378 INCHES MINIMUM AND 0.403 INCHES MAXIMUM
	WIDTH BETWEEN FLATS	0.922 INCHES MINIMUM AND 0.938 INCHES MAXIMUM
	NOMINAL THREAD DIAMETER	0.625 INCHES
	THREAD QUANTITY PER INCH	11
	MINIMUM TENSILE STRENGTH	150000 POUNDS PER SQUARE INCH
	HARDNESS RATING	32.0 ROCKWELL C MINIMUM OVERALL AND 38.0 ROCKWELL C MAXIMUM OVERALL
	SURFACE FINISH	63.0 MICROINCHES THREADS
	MATERIAL	STEEL OVERALL
	MATERIAL DOCUMENT AND CLASSIFICATION	SAE J429 GRADE 8 ASSN STD SINGLE MATERIAL RESPONSE OVERALL OR ASTM A354 GRADE BD ASSN STD SINGLE MATERIAL RESPONSE OVERALL
	PROPRIETARY CHARACTERISTICS	PACS
	SURFACE TREATMENT	ZINC OVERALL AND CHROMATE OVERALL
	SURFACE TREATMENT DOCUMENT AND CLASSIFICATION	ASTM B633 TY 2 SC 3 ASSN STD SINGLE TREATMENT RESPONSE OVERALL
	THREAD SERIES DESIGNATOR	UNC

 

[Evvy Fesler]

Hi Evvy, were those bolts 3/8" or 7/16"? They look relatively small in the picture so I'm surprised your impact wasn't up to the challenge.
It looks like you have lock nuts on there, but still shouldn't have been that big of a deal for a decent impact.
However, from experience I know there are several items that all contribute to "weakening" the available torque from your wrench.
Were you using an extension and / or a universal joint? Both of these will greatly reduce the force an impact will effectively deliver.
Also, applying the impact force to the bolt rather than the nut tends to reduce the effectiveness also because the bolt's shank will twist slightly and absorb some of the force
and lastly I see a 12pt. chrome socket in the background, this is also somewhat of a bad idea if you used it on your impact. The chrome sockets often can't handle the power of a good impact wrench ( and may split open ) and 12pt's tend to slip ( vibrate back and forth ) more on the hex and you will loose a little bit of power through this slight movement. So... all combined, this could be the reason your impact couldn't cut the mustard!
I'm not looking to be critical, but rather I sense you have an obvious desire to learn at every possible opportunity, so I wanted to pass on some of my past experiences.

Hi Ray, both the head and the nut were 15/16. The nuts were lock nuts. I think the issue was a combination of things. I did use a 3" x 1/2 extension to give a little more clearance than was there. Up top, on the bolt head, I used the vise grip to that too, allowed for a little shock absorption. My impact sockets are black. I use them most of the time unless I want to use a 3/8" drive and then I'll turn to my chrome set. I won't use chrome with the impact wrench. Readers,. Ray is cautioning me that chrome can shatter from the hammering of the impact wrench and that can be bad for eyesight and gray matter. At very least it hurts!

Ray, you can warn me of safety issues anytime. Thank you for looking out for me. I really appreciate safety and wisdom!

 

[Evvy Fesler]

I think this is the tech data for the bolts.

	THREAD CLASS	2A
	THREAD DIRECTION	RIGHT-HAND
	THREAD LENGTH	1.500 INCHES MINIMUM AND 1.727 INCHES MAXIMUM
	FASTENER LENGTH	4.656 INCHES MINIMUM AND 4.750 INCHES MAXIMUM
	HEAD STYLE	HEXAGON
	HEAD HEIGHT	0.378 INCHES MINIMUM AND 0.403 INCHES MAXIMUM
	WIDTH BETWEEN FLATS	0.922 INCHES MINIMUM AND 0.938 INCHES MAXIMUM
	NOMINAL THREAD DIAMETER	0.625 INCHES
	THREAD QUANTITY PER INCH	11
	MINIMUM TENSILE STRENGTH	150000 POUNDS PER SQUARE INCH
	HARDNESS RATING	32.0 ROCKWELL C MINIMUM OVERALL AND 38.0 ROCKWELL C MAXIMUM OVERALL
	SURFACE FINISH	63.0 MICROINCHES THREADS
	MATERIAL	STEEL OVERALL
	MATERIAL DOCUMENT AND CLASSIFICATION	SAE J429 GRADE 8 ASSN STD SINGLE MATERIAL RESPONSE OVERALL OR ASTM A354 GRADE BD ASSN STD SINGLE MATERIAL RESPONSE OVERALL
	PROPRIETARY CHARACTERISTICS	PACS
	SURFACE TREATMENT	ZINC OVERALL AND CHROMATE OVERALL
	SURFACE TREATMENT DOCUMENT AND CLASSIFICATION	ASTM B633 TY 2 SC 3 ASSN STD SINGLE TREATMENT RESPONSE OVERALL
	THREAD SERIES DESIGNATOR	UNC

Thanks @Mullaney. I was going to look this one up and post a parts wanted. I'm hoping a member has a box of them and is willing to sell a couple.

 

[87cr250r]

How many do you need? The spec calls out SAE J429 which is engineering speak for a grade 8 bolt from the hardware store. Shipping is going to cost more than the bolts. The nylock nut with the two notches on the side is not a hardware store item if you're trying to keep the unit original but is easily substituted otherwise.

 

[Evvy Fesler]

How many do you need? The spec calls out SAE J429 which is engineering speak for a grade 8 bolt from the hardware store. Shipping is going to cost more than the bolts. The nylock but with the two notches on the side is not a hardware store item if you're trying to keep the unit original but is easily substituted otherwise.

Agreed on shipping. I haven't been able to find them around here. I just need two with the nuts. Grrr....

 

[mciikurzroot]

This post already has a confirmed diagnosis and root cause. I’m posting it to contribute to our knowledge base. Newly acquired genset had low voltage trouble light and lack of 120v on convenience outlet. Kurt Klopp refused to let me buy a voltage regulator until we did a little troubleshooting. Ultimately it lead to pulling the bell cap off to inspect and test the diodes. It was pretty obvious at that point. The diode ring was destroyed and unfortunately it gouged the stator windings on the way. I was also surprised to discover that this generator had the bolt on diodes and not the pressed-in ones that the TM says it’s supposed to have. It made me wonder if someone put in the wring part or if the generator was a different part than the original. Kurt suggested it may be a change in how they made them.

I’ve got pics to show. Click here!

Your advice is welcome. Some things you might comment on are:
- Rewind or not
- Where to find a rebuilt generator p/n 88-21005
- Sell the set and it’s trailer
- any other insights?

Evvy-

Some late to the party answers and suggested causes of this 15kw set... I see about 3-5 of these every year, the cause steems or seems to be from the Ground BOND strap not being bonded to the GROUND but rather to L1 wherein this short causes a very high inrush or "forcing" of the FIELD and then the resulting FIELD rotor and STATOR dramatic failure and collateral damage.. It's easy when you look at this as i outline it how a person can confuse mis-locating the bonding strap to the WRONG terminal... Marathon to my best knowledge is and has been the only manufacture of the 15 kw gen heads. The 15 kw gen head is a bear to remove the main rotor and then rewiring to make it from a 10 lead to a 12 lead set . but we have done it now my guess 12 times or so to the point we bought a 15kw just for the generator head so we could have one already converted to 12 lead and make a faster turn time for our customers...then when we take in the new 10 lead gen we convert it as a routine process and not a rush effort..
the RED material Peter is talking about is formally called Glastic and come is all shapes and sizes as well thickness with a very high dielectric strength... somewhere i have the rewind data for these pieces of the field rotor main rotor as well the stator.. someone pointed out yes its a pain in the ass to remove the end bell and then the rotor, without destroying more windings on the main stator , of all the entore MEP line up the 15kw is the most awkard or difficult of any of them.. sorry to be so late in responding.. my day job is demanding as well home life.. best mac/mc MC II

 

[mciikurzroot]

Evvy,

These Diesel engines are optimized to put out the highest torque at app 1,800 rpm
At 300rpm you probably going to get 30% of the rated Torque which would reduce your maximum power output to 15KW x 0.3 => 4.5KW

Your better off with a 5KW Genset then

Peter

This response is toward 400hz possible compatibility, and not intended for Peter, he well knows the diff..
Dont even think you "SLOW" it down and make this all work, you gave the logic away when you discovered the 24 poles/winding vs for a 60hz set

 

[87cr250r]

There is a case when wired in delta where the ground connection is made to a line terminal. But that can't apply to 10 lead units.

 

[Evvy Fesler]

Got'em all out! OMGosh... I don't know which is worse... the man engineer who designed this; the man mechanic who thought it a good idea to lock down the fan so the fins are over the bolt heads; or @Guyfang who sent me a stream of new potty words?

Anyway, it was in the mid-60's today and I needed something to do. Now I can pull the main generator out.

BTW - putting a 5/8 bolt and a jam nut in the bore hole in the rotor end made it easy to turn the rotor and engine.

 

[mciikurzroot]

View attachment 885216


Got'em all out! OMGosh... I don't know which is worse... the man engineer who designed this; the man mechanic who thought it a good idea to lock down the fan so the fins are over the bolt heads; or @Guyfang who sent me a stream of new potty words?

Anyway, it was in the mid-60's today and I needed something to do. Now I can pull the main generator out.

BTW - putting a 5/8 bolt and a jam nut in the bore hole in the rotor end made it easy to turn the rotor and engine.

View attachment 885219

You have verified my original or near original satements, this whole process is akin to being a female dog and is by far the most difficult of any of the MEP series sets bar none.. Not for the faint of heart and even then you're now only about 1/3 done as putting Humpty Dumpty back together again is worse .. the problem is the interference keeping the horizontal fit and separation between the rotating and stationary exciter not to nick any of the windings, thereby needing EPOXY repair/s ... But if you did/do and don't notice it, fear not ? on start up the burning varnish and soon copper splatter of the exciter wiring, will be a pretty obvious indicator, don't rush to shut it down ? the damage will already be complete..
Keep us informed.. mac/mc MCII

 

[Evvy Fesler]

You have verified my original or near original satements, this whole process is akin to being a female dog and is by far the most difficult of any of the MEP series sets bar none.. Not for the faint of heart and even then you're now only about 1/3 done as putting Humpty Dumpty back together again is worse .. the problem is the interference keeping the horizontal fit and separation between the rotating and stationary exciter not to nick any of the windings, thereby needing EPOXY repair/s ... But if you did/do and don't notice it, fear not ? on start up the burning varnish and soon copper splatter of the exciter wiring, will be a pretty obvious indicator, don't rush to shut it down ? the damage will already be complete..
Keep us informed.. mac/mc MCII

Hmmm... female dog, Mac? I assume you meant witch with a B and not I!

 

[mciikurzroot]

Hmmm... female dog, Mac? I assume you meant witch with a B and not I!

Bit** is understated, I'm sure some word can fit this application better, but i was trying to stay gender neutral. Although WOKEism is not a real problem among this group of readers I dont sense anyhow... I know you slightly from several exchanges and i did argue with myself to use that slang term in light of my respect for you.. my humor is thin tonight, i'd best stop before i compound this situation, but we should talk soon .. mac/mc

 

[mciikurzroot]

Bitch is understated, I'm sure some word can fit this application better, but i was trying to stay gender neutral. Although WOKEism is not a real problem among this group of readers I dont sense anyhow... I know you slightly from several exchanges and i did argue with myself to use that slang term in light of my respect for you.. my humor is thin tonight, i'd best stop before i compound this situation, but we should talk soon .. mac/mc

if you're free i can call now but will have to excuse myself in 10 minutes to remove the Pumpkin bread from the oven but can then resume talking its a 5 minute task .. bread that is ..

 

[Evvy Fesler]

if you're free i can call now but will have to excuse myself in 10 minutes to remove the Pumpkin bread from the oven but can then resume talking its a 5 minute task .. bread that is ..

Hey Mister Mac... sorry to have missed this. Anytime today or tonight works. I still love you even if you occasionally call me a witch with a B!

 

[Evvy Fesler]

Rust in the bell housing...

Greetings! What do you think is the cause of the rust in the bell housing?

Note: You are looking at the rear of the Isuzu C240 engine with the main generator having been removed. You can see the starter motor peeking through at 10:00.


High resolution photo here!