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Discussion Starter · #242 ·
Hey Duncan, any idea what motor volts/amps were at when it blew? Just wondering how much was too much for that motor. With your high voltage pack, what was your peak motor volts? I saw 1200 peak amps.
Hi
I can't read the instruments when I'm on the track
But I'm pretty sure I was well over peak motor current and into 100% controller territory

I would estimate about 700 amps 4500 rpm and about 300v when it blew

BUT it wasn't the com/brushes that went - I was sure that those would go first

I think that something went through the motor and damaged that specific wire which then failed and produced a big arc

I have been abusing it for the last five years!
 

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I'm sure those windings get pretty hot at that level of power. That one armature winding may have came loose and threw out enough to tag something and arc. Doesn't really matter now anyway. Sorry you lost your motor. I've been keeping an eye on your car since I have the same motor that I still hope to use someday. I figured it could take some serious amps, but I never thought it would handle 300 volts.
 

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Duncan, You have done us a great service. It's not everyday that we get the sort of data that you have given us. We now have a better idea of the limitations of a motor like yours. I am sorry it came at such a cost. I hope you can find a suitable / cost effective replacement soon.

Obviously we are pushing these motors past their designed purpose and sometimes past their physical limitations. It is very dificult to know where to draw the line. They don't give audible warnings like ICE motors do.....until it's too late.

Please keep us posted on your progress.
 

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Discussion Starter · #245 ·
Hi Guys

Just back from Dunedin
The guy had a LOT of motors so I have picked up one that is exactly the same model as my old one and a dinky little 9 inch motor to have a look at

He has another three or four more Hitachi's like mine but a bit later and about 20mm longer
$200 each for the big ones and $100 for the 9 inch

I will need to clean then up and take pictures!
 

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Coat those windings! Or get the arm. and stator dipped and baked at a motor shop.http://what-when-how.com/electric-motors/dip-and-bake-systems-electric-motors/

Megaohming the parts before and during the clean-up and re-coating process(es) would also be a good idea, since you're using it at such a high voltage.

This sounds like good advice. I will keep this in mind if I ever choose to increase my voltage.

Duncan, Its great to hear you have some options up your sleeve. I can't wait to hear that you have it back up an running.
 

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Discussion Starter · #248 ·
OK
I have completed the trolleys I promised to the high school and cleared the wood work out of my shed

Back to business!

Only allowed to up load 10 files at a time

Here we have the new armature - com area - looks good to me

The brush holder - looks like a bit of rust

Brushes - only 4 of the eight brushes present - and one of those was well stuck
Looks as if they were cocked over in the holders when running

The armature from the side - small amount of water damage
 

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Discussion Starter · #250 ·
Part two

Another picture of the armature

Pictures of the inside of the stator - field coils

Now back to my old motor - copper plastered onto the field coils - and I think it has burnt into the insulation

I used to get nothing at all on my meters 20 MegOhm scale - now field coil to the metal gives me 0.5 MegOhm

So that's dead as well!

Plan is to select the best of the brush holders and springs

QUESTION - I'm hoping that Major will help me here
Sand blast them?
If I do is there anything I should do to preserve them afterwards?

QUESTION
Dip or laqueur the armature? - I'm inclined to leave it the way that Hitachi left it

I'm being a lot more careful with the armature on this one ensuring that nothing bumps into the armature laminations - with the weight of the armature I may have banged the old one against the field coils - I'm using a hoist and doing it all in the vertical frame


I also have a collection of brushes I was given - I intend to do some measuring and sorting - see exactly what I have

Taking a bit longer than I planned
 

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Discussion Starter · #251 ·
Hi Galderdi
The two pictures with molten copper sprayed onto the coils are my "old" motor

The rest are my "new" motor

Bit of rust inside the "new" motor but I think that's ok - except for the rust on the brush holders - that will need to be fixed
 

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QUESTION
Dip or laqueur the armature? - I'm inclined to leave it the way that Hitachi left it
Yes, but Hitachi probably dipped it many decades ago. The varnish may have dried out, cracked, or been worn away by now. As well as a insulator, the varnish glues the windings in place to keep them from shifting around and chafing the insulation. That's probably what doomed your old motor.

Check what the motor shops suggest for a high voltage, current, and RPM severe duty usage. Also, check the condition of the fiberglass (usually) tension bands around the exposed windings. The glue holding them on may have dried out and weakened.
 

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Discussion Starter · #253 ·
Hi Guys

Brush holders and brushes

The rusty brush holders are from the "new motor"
The black looking brush holders are from my old motor
I'm thinking of using the "old" brush holders and giving them a very quick and gentle clean

Thoughts?? - or should I sand blast them down to clean metal?

Brushes
The brushes from the "new motor" looked horrible - were worn down and there only were three setts

The brushes with the blue insulation came from my old motor
I have been told that the blue means that they were soldered together here in NZ
Dimensions - Blue insulator
Width -24.9 mm Thickness 16.99 mm - Length - from 25 mm to 26 mm

I have been given the brushes with the grey insulation
These look in much better condition

Dimensions - Grey insulator
Width -24.9 mm Thickness 16.99 mm - Length - from 27 mm to 29 mm

There is a code on some of them E46X - it may be E48X
And one of each pair has a channel in it

Current plan

Drill and tap the "Barrel" so that I can advance the brushes by 8 degrees - as before

Clean the outside and gently clean the inside

Fit my old brush holders and the brushes with the grey insulation

Run it in on 12v for an hour or so

Fit it into the Device!

I also have a new GPS Speedo and an idea for moving the instruments so that I will be able to see them in the sunshine - NOT a problem I had back in the UK
 

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Duncan! You're running the motor at 8-10 times the stock voltage. The motor is going to need all the help it can get to survive. At least apply the good part of a rattle can(spray paint can) of a good insulating varnish(paint) designed for motor windings from an industrial supplier. It's cheap insurance for the kind of thrashing you're going to put this motor through.

Since the paint is solvent based, the heavy coatings needed will take some time to dry-several days or more. Also, it can be baked. I've used it a lot. If the armature is rotated slowly mechanically or by hand incrementally every 10 to 20 minutes, initially, I've gotten good coverage and never had an imbalance problem. And, it makes the windings look good, easier to clean, shed dirt, and impress your fellow motor heads!!
 

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Discussion Starter · #256 ·
Hi Electro wrks

My limited experience with glues, paints and lacquers all says that the absolute KEY is the surface treatment before applying the "glue"

As in the difference between a coat that can peel off and something that becomes part of the unit

My problem is that I really don't want to do anything aggressive to the armature assembly and I am definitely NOT going to strip it down to parts so that it could be re-done the way that Hitachi did it - decades ago -

So I am loath to do anything aggressive to the existing coating - and at the same time I'm not at all sure than any extra "glue" will stick well enough to do any good without that aggressive cleaning

The examples you show are of large units - and I bet they will be very careful and know exactly how to approach the cleaning and re-gluing
 

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Good points about the cleaning before painting. I remember one hydro dam generator was cleaned with a walnut shell blast medium before painting. I have successfully used Stoddard (close to mineral spirits, paint thinner) solvent to clean the windings on dozens of motors from small universal motors in power tools to motors larger than yours. I've never seen these mild solvents harm the insulation coatings on motor windings. If you not sure, test the solvent on a sample area. Make sure the solvent is completely dried out before painting.

One large wound-rotor induction motor from a large printing press was so heavily caked with paper dust and grease, it needed to be scrubbed with soap and a water blast. After it was cleaned, it was rinsed with a lot of distilled water and baked dry. After it was dried, and before painting, it megaohmed out as good.

Did you have a chance to talk to a motor shop about their recommendations?
 

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Discussion Starter · #258 ·
Hi electro works

I have been thinking about the failure I had and looking at the parts

I think that it may have been my own fault

When I look at the old armature the first few laminations have some gaps - looks a bit like the pages of a book

The armature is quite heavy - 50kg? - and I took the barrel off the old armature a number of times in the horizontal mode

I worry that I managed to damage the armature - and its wires against the field coils - or more accurately their cores

I'm going to take a great deal more care with the "new" one - doing everything in a vertical mode and using a hoist to take the weight of the barrel so I can ensure it does not bash on the rotor

With what I know about glues and preparation I'm not at all sure that I can actually improve on the original Hitachi work PLUS if I do do anything it will increase the amount of handling of a very heavy and possibly delicate armature

I think I will rebuild this one using the bits that I have to get my car back on the road - I will also try and get my hands on another one (third) that could be possibly torn down and re-glued and baked over a longer time period
 

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As far as the paint adhering to the surfaces, the cloth sleeves(if used) around the wires, the insulating paper, and the wood wedges(if used) that lock the windings in the slots all soak up the paint somewhat to increase the insulation around the wires. And, as you say, "glue" the parts together to keep them from shifting around and chafing.

I've also damaged windings . Sometimes, not always, you can carefully pry back the wires(if they're not burned-up) in the damaged area, insert pieces of the insulating paper to re-insulate the wires, and repaint. Motor shops will give or sell you the small amounts of paper as well as the insulating sleeve material, if needed. They also would be a good source for the insulating paint.

You're right. It is a chore to do this. And, it sounds like you can't wait to get back on the road!
 

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Hi Dunc,

Sorry for the delay. Lucky you found the same motor for replacement since you were pleased with its performance. From what I see in the photos, it looks good to go except for the brushes. BTW, break in for longer than an hour. Like maybe a week.

For extra insulation and "gluing", use Glyptal 1202. Factory likely used a polyester resin. Retreating an entire armature nothing beats vacuum impregnation.

You might be right about damage to the original armature but the arc flash event could have spread those laminations as well.

Good luck,


major
 
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