# K9 Problems



## jackbauer (Jan 12, 2008)

I recently acquired a kostov 9" hv series motor that had suffered a failure. The photos tell most of the tale. From what I can see it looks like a flashover occured between the armature bars and the series field windings on the drive end. I believe it may have been wired incorrectly by the previous owner. 

It spins up fine in both series and parallel field on a 12v battery. My question is how to go about repairing the insulation damage to both the drive end armature windings and the drive ends of the series field winds? Please don't everyone just tell me to get it rewound or buy a new one. Just not financially viable right now. My initial thoughts for the field is to strip it all out of the housing , remove the damaged insulation , rewrap and soak in varnish. 

Any sugestions welcome.


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## piotrsko (Dec 9, 2007)

Not EVEN claiming to be in Major's class, but doing a vacuum and pressure soak of varnish bath may fill all the voids, but I'm not sure it would prevent further flash over. It would definitely be a joy to disassemble thereafter.


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## Guest (Oct 14, 2011)

Almost looks like something went through the motor causing abrasion then causing the flashover. Clean it up and rewrap and revarnish sounds good. A bit of work but good to know and learn. Hows that com? Think you can reuse that? Looks a bit melted at that one spot. If the com is good then learning about and rewrapping is a good thing. Does it look like something went through the motor to you? 



Pete 


http://greenev.zapto.org/kostov/Kostov_Zapi/The_Albums/The_Albums.html


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## major (Apr 4, 2008)

jackbauer said:


> I recently acquired a kostov 9" hv series motor that had suffered a failure. The photos tell most of the tale. From what I can see it looks like a flashover occured between the armature bars and the series field windings on the drive end. I believe it may have been wired incorrectly by the previous owner.
> 
> It spins up fine in both series and parallel field on a 12v battery. My question is how to go about repairing the insulation damage to both the drive end armature windings and the drive ends of the series field winds? Please don't everyone just tell me to get it rewound or buy a new one. Just not financially viable right now. My initial thoughts for the field is to strip it all out of the housing , remove the damaged insulation , rewrap and soak in varnish.
> 
> Any sugestions welcome.


Hi jack,

K9 sounds like a dog of a motor to me 

Looks like overspeed to me. Armature end turns (knuckles) have ballooned out and rubbed the field coil end turns. I am surprised the comm didn't explode. Chances are it has distorted, possibly beyond repair. If it is significantly out of round or has a cracked core, I'd consider it useless.

I know you're a pretty resourceful and handy-with-tools type of guy but it is a big job. First you have to get those armature coil knuckles bent back into proper shape, below the diameter of the core. They cannot touch one another. Then insulate varnish after applying a securing band of glass tape. Bake and balance. Comm turn and undercut.

On the damaged field coils; remove, unwind, insulate and rewind. You must insulate turn to turn. I don't see how to insure that with them wound tightly. A narrow strip of Nomex inserted between all the turns might work. Once (and if) field coils are repaired, dip varnish and bake. Reassemble and check for grounds, hi pot and low voltage spin test.

Piece of cake 

major


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## PZigouras (Jun 5, 2010)

major said:


> Hi jack,
> 
> K9 sounds like a dog of a motor to me
> 
> ...


 
Major -

I have a friend with the same Kostov 9" motor that caught fire due to a failed fan. The armature windings are not [visually] distorted. Can they be cleaned and re-varnished without disassembling the armature?

My guess is no, but I wanted to get your opinion before telling him not to bother with it. The comm itself looks fine.


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## Batterypoweredtoad (Feb 5, 2008)

Do the HV 9's have internal AND external fans?


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## major (Apr 4, 2008)

PZigouras said:


> Major -
> 
> I have a friend with the same Kostov 9" motor that caught fire due to a failed fan. The armature windings are not [visually] distorted. Can they be cleaned and re-varnished without disassembling the armature?


Unlikely. Probably needs stripping and rewind.


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## PZigouras (Jun 5, 2010)

Batterypoweredtoad said:


> Do the HV 9's have internal AND external fans?


They come both ways, but I think Kostov stopped making the ones that required an external blower a while ago.


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## jackbauer (Jan 12, 2008)

Thanks guys. Looks like bad news so  I'll contact kostov to see if they might supply a new armature and field coil set.


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