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Topic: Help with Cory Electric Grinder that died... (22 msgs / 529 lines)
1) From: Brett Mason
Poor thing, up and died...  I am not sure I understand how to diagnose
this, or where to look for help fixing it.  But I love my CORY and
wish it to resuscitate...  Please read, then supply any ideas?
How do I "rewind" an electrtic motor?  I have taken the motor out of
the casing, and found there is a spark that arcs from the brushes to
the spindle, and then it won't turn.  If I "realign" the spindle and
try again, the motor will spin until that spark arcs...  I don't know
anything about electricity.  I have a digital multimeter so I can see
if electricity goes through, or if there's resistance, or how many
volts are there, etc...  I am not sure how to proceed, although I can
certainly unsolder the electrical wires, replace them, and/or replace
any components along the way.  I just am not sure what to do next.
Cheers,
Bretthttp://homeroast.freeservers.com

2) From: Aaron
Brett, rewinding a motor is not something the average layman can do.  I 
have done it and have been sent to the school to learn how to do it 
properly and have done from 1/4 horse to 400 horsepower motors BUT, it's 
a trade you never stop learning.  I have stopped practicing it several 
years ago when I left the navy / and rewind area so I know what i am 
doing but would be kind of err rusty at it.
Here's a few terms, weave, lap, delta, wye...
have to burn it, pull it, insulate it, build the winding press it in, 
bake it, spin it, reassemble, balance, bla bla..  For a small motor you 
can probably get around the burn part as the windings can come out, but 
it's a pretty precise science actually.
The brushes will arc,that's what they do, it's part of their nature, now 
ideally the 'neutral' will have been set so that they don't arc as much 
but that will change under load.
If you are arcing from brush to spindle something is wrong / missing in 
there, an insulator of some type, and the brush should never do that.  
Realign the spindle??  you mean it wiggles??, if thats the case, you 
have a worn / failed bearing / bushing / holder / retainer etc etc, Id 
really have to see it to tell for sure.
another problem with motors when they have arced out like that, the 
electricity flows through all parts of it then, stationary moving you 
name it, generally hardest hit are bearings as it can weld them, pit the 
races / actual balls themselves .. which is a short order death sentence 
essentially.  Be very careful, because technically the spindle is or 
should be at ground potential (unless it's a UL rated double insulated 
tool) ... umm touching metal in it if it arcs might give you a bit of a 
shock, and given ohms law and eli the ice man, that shock could be a 
teeny bit more than 115.
For small frame motors like that, I hate to say it but a new motor is 
probably the most econimical way,  see if it has nameplate data on it..  
ie something like
general electric general purpose motor   120 volt, 1.4 amp, 1800 rpm, 
type N insulation any crap like that, and do a google search for motors, 
play with wording and see if you can possibly find a supply house that 
has them.
Ill be going to the doctor a bit later in the morning, but will be home 
in the afternoon, give me a call if you want and we can see if we can 
figger something out on this.
Aaron

3) From: RK
may be dirty commutator and the brushes may be worn
try cleaning the commutator with some sand paper and clean the brushes. also 
check the spring pressure on the brushes to make sure they stay in contact 
with the commutator.
click here for a drawing to illustratehttp://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/comtat.htmlJust a thought.

4) From: Aaron
Brett while your unit is A/C not DC... RK's advice is sound.   Check for 
tightness on the brushes, and the assembly that holds them, and that 
they are not worn down to a nub.
They may not have a spring per se but a piece of metal bent in a way to 
put pressure on them, Ive also seen some with a wierd screw down 
contraption on them too... but tightness is a factor if they are 
flopping around that could cause excessive arcing with the potential of 
an arc over to nearby metal.
IF you need new brushes, same size about works for a quick fix,  so if 
you have an old drill or something that went ti.. err thumbs up, steal 
em out of that.
aaron

5) From: Brett Mason
Hmmm - OK the chicken in me is lifting its spindly beak ...  What kind
of business should I look for in the Yellow Pages to find someone who
can fix this in my area?
Thanks,
Brett
On 12/28/06, Aaron  wrote:
<Snip>
-- 
Cheers,
Bretthttp://homeroast.freeservers.com

6) From: Aaron
 electrical or small appliance repair might work.  Id go with small 
appliance repair...
but you can do it yourself I bet, you already got the thing tore down, 
it's not that hard to go from there, I mean whats the worst you can do 
to it, it's already broke... see what I mean :)
Aaron

7) From: Brett Mason
I got her open, and don't see anything particularly wrong.  There's
about 50 years experience in there, no obvious burnt wire, everything
is cruddy...  I can't tell what the specs are on the motor, but it's
old...  What would you do next?
Thinking of looking for a new grinder...   :-(
On 12/28/06, Aaron  wrote:
<Snip>
-- 
Cheers,
Bretthttp://homeroast.freeservers.com

8) From: Eddie Dove
Brett,
If you can find a shop that works on electrical motors, there is bound to be
a veteran that will know everything about that motor just by looking at it.
They can either fix it or find you a suitable replacement.  Down here, I
would ask my neighbor ... he is about 60 years old and has owned his own
accounting office since forever ... so he know all the folks and businesses
around here ...
Eddie
On 12/28/06, Brett Mason  wrote:
<Snip>
-- 
My Home Coffee Roasting Blog and Profiles for the Gene Cafehttp://southcoastcoffeeroaster.blogspot.com/

9) From: Brett Mason
The first shop sent me to the second shop.  The second shop said they
can rewind it for $300 which is their minimum charge...
On 12/28/06, Eddie Dove  wrote:
<Snip>
-- 
Cheers,
Bretthttp://homeroast.freeservers.com

10) From: Barry Luterman
Maybe time for a Rocky and clean it with Minute Rice it's easier on the 
motor.

11) From: Brett Mason
There ya go!  Well, I have a Rocky, dedicated to espresso, and a
couple Zasses at home.  The ROcky is dialed in for drip at the
moment...
OMG I can't believe it, but I am actually considering minute rice...
Thanks,
Brett
PS - if anyone sees another Cory electric mill out there, let me know?
 I miss it already...
On 12/28/06, Barry Luterman  wrote:
<Snip>
-- 
Cheers,
Bretthttp://homeroast.freeservers.com

12) From: miKe mcKoffee
<Snip>
That's ok Brett, just remember it's a grinder quick cleaner and not to be
cooked as a food!:-)
Kona Konnaisseur miKe mcKoffee
URL to Rosto mods, FrankenFormer, some recipes etc:http://mdmint.home.comcast.net/coffee/Rosto_mod.htmUltimately the quest for Koffee Nirvana is a solitary path. To know I must
first not know. And in knowing know I know not. Each Personal enlightenment
found exploring the many divergent foot steps of Those who have gone before.

13) From: Barry Luterman
Rice is eaten extensively here in Hawaii. Everyone has a rice cooker out on 
their  kitchen counters. I had trouble finding Minute rice to clean the 
grinder. Every time I asked for it  the clerks would ask what do you want to 
eat that stuff for.

14) From: Eddie Dove
Wow ... does that every present a quandary ... I can just see the priceless
expression on your face!
"I don't want to eat it.  I need it to clean a coffee grinder ..."
"Uh huh ... we keep the 'coffee grinder cleaner' in aisle ..."
On 12/28/06, Barry Luterman  wrote:
<Snip>
-- 
My Home Coffee Roasting Blog and Profiles for the Gene Cafehttp://southcoastcoffeeroaster.blogspot.com/

15) From: miKe mcKoffee
This is a multi-part message in MIME format.
Or just as likely "Why would you clean a coffee grinder? We haven't needed
to clean the grinder in aisle 7 for 10 years that's used to grind those
fresh whole beans we stock. (that have been in the bins for 5 years) ..."
 
miKe  
From: homeroast-admin
[mailto:homeroast-admin] On Behalf Of Eddie Dove
Sent: Thursday, December 28, 2006 3:12 PM
To: homeroast
Subject: Re: +Help with Cory Electric Grinder that died...
Wow ... does that every present a quandary ... I can just see the priceless
expression on your face!
"I don't want to eat it.  I need it to clean a coffee grinder ..."
"Uh huh ... we keep the 'coffee grinder cleaner' in aisle ..." 
On 12/28/06, Barry Luterman  wrote: 
Rice is eaten extensively here in Hawaii. Everyone has a rice cooker out on
their  kitchen counters. I had trouble finding Minute rice to clean the
grinder. Every time I asked for it  the clerks would ask what do you want to
eat that stuff for.

16) From: raymanowen
Brett, you have a series wound universal motor. What you do next is what you
should have did first. I suppose you could never see the commutator and
brushes while it's running, so you couldn't have noticed the increased
arcing as the motor ran.
There are tricks that can be done to get the motor to run while you procure
new brushes. I wouldn't suggest any because the new brushes were Needed Six
(6) Months Ago! They've been arcing for quite a while before es
abgeschraubt. It's been eroding the commutator all that time.
All you need is a set of brushes. Make sure they come with the brush spring,
braided copper wire "Shunt," and proper terminal.
If everything else fails, try a sewing/ vacuum cleaner store to see if they
have brushes that fit. Also, tool stores or a Sears (any) appliance repair
center might have usable parts.
Actually, electric drill motors are about the size and power of your
grinder's motor.
Maybe Lowes, Homer's Despot or even a hardware store could match the motor
you have to brushes they have.
Brushes that are a little long or a little fat can be modded with file,
sandpaper, or hacksaw, as long as the shunt and spring are not obscenely
different. You can always splice your old terminal onto a new shunt
Help this hopes.
Cheers -RayO, aka Opa!
-- 
"When the theme hits the bass, I dance the Jig!" - -Virgil Fox at the Mighty
Wichita (ex- NYC Paramount) WurliTzer- 1976

17) From: raymanowen
"...they can rewind it for $300-"
I will do it cheaper. $299.99 FOB, tax included.
Never mind if it looks like the motor out of a $9.99 Tool King electric
drill.
Is it a blade mill or burr grinder?
Cheers -RayO, aka Opa!
On 12/28/06, raymanowen  wrote:
<Snip>
(Dismantle the motor, keep shim washers in proper order, and chuck the
armature shaft at the commutator end in a drill press.)
Keep cutting tools away from the windings, only touch the commutator.
At low RPM, lightly drag a flat file against the commutator to clean up a
pitted surface.
Stop the drill and dress between the commutator segments using the teeth at
the end of a broken hacksaw blade. Use the raw end that will cut in as you
drag it lightly across the segment slot. This will remove the slight burrs
you created with the filing.
Finally, polish the commutator's surface with steel wool or Crocus cloth,
whichever you have, maybe use the drill press again but don't be too
aggressive.
I didn't find any, but All you need is a set of brushes. Make sure they come
with the carbon brush, spring, braided copper wire "Shunt," and proper
terminal.
Cheers -RayO, aka Opa!
-- 
"When the theme hits the bass, I dance the Jig!" - -Virgil Fox at the Mighty
Wichita (ex- NYC Paramount) WurliTzer- 1976

18) From: Brett Mason
Hi Ray,
It's a flat burr mill with hardened steel burrs.  I doubt they have
worn down that much in 50 years!  Frankly they have probably seen
almost NO uncooked rice, which means they should be in great shape.  I
can only imagine the damage they would have incurred if rice had been
poured through the mill...
I am hitting up hardware stores today to find replacement brushes as
you have advised.  I had a hope you would join in the discussion.  All
the replies were helpful, but starting with the briushes and what to
ask for were paticularly helpful pointers...
Thanks,
Brett
On 12/28/06, raymanowen  wrote:
<Snip>
-- 
Cheers,
Bretthttp://homeroast.freeservers.com

19) From: raymanowen
Excuse me, Brett-
My Word processor is Kaput. After you use the flat file lightly to resurface
the  commutator segments if they're visibly pitted, drag the hacksaw teeth
<Snip>
remove the copper burrs this way before you polish it up.
Actually, there were lathes for resurfacing the commutator segments of
electric motors. Undercutting the commutator was a very precise operation
too, a century ago.
Cheers -RayO, aka Opa!
-- 
"When the theme hits the bass, I dance the Jig!" - -Virgil Fox at the Mighty
Wichita (ex- NYC Paramount) WurliTzer- 1976

20) From: RK
This is a multi-part message in MIME format.
snip: RayO, aka Opa!
<Snip>
electric motors. Undercutting the commutator was a very precise =
operation too, a century ago.
Very true, I used a lathe for truing a commutator and a slitting saw in =
a milling machine to cut the space between the segments.
Most welding shops carry a polishing stone for commutators for gas or =
diesel powered generators used to power arc welders. 
They would be to large for small motors but one could cut a piece off to =
fit. I have also use eraser on a pencil to remove carbon deposits on =
commutators.
RK

21) From: Michael Dhabolt
The community I live in has a population of about 10,000 and is definately
behind the times.......not quite a century though.  A local Auto Electric
store still has and uses a 6" Atlas lathe with all the extra goodies
specifically for turning etc. commutators. It is used frequently to rebuild
fairly expensive starters and such (like 24 Volt starters for trucks).  I
enjoyed a cup of my homeroast with the owner of the shop while he was doing
one of these motors about two weeks ago.  Check around for a similar shop in
your community - it will not have one of the 'Chain Store' logos attached.
Mike (just plain)

22) From: Aaron
Brett, check alternator / motor rewind shops too.  .... they might be 
able to do it for under 300.
but on that, as mike said, it's a pretty common 'small scale' motor, and 
theres a good bet your drill has one, a blender has one, a bread machine 
has one, etc etc...so if you have to swap motors it should not be that 
big of a deal.
worse case, the things broke and don't work right... send it to me and 
ill see what I can do (no promises, no guarantees) but I might be able 
to give it some more life, new motor, replace brushes, whatever I can do 
to it...
your call.
aaron


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