Discussion:
Request for comments: Project Ball-mill
(too old to reply)
RoCkaZ
2003-08-11 20:09:50 UTC
Permalink
Hi there,
me and my friend are making our very first ball-mill. I've done a lot
of googling and reading, and decided to make a mill, that would look
something like this:
Loading Image...
Here's a little demo:
http://www2.omnitel.net/rokas/ball_mill_demo.avi (1.8MB)
You can see the two separate milling sections. The lower section is
supposed to be used for "safe" milling (separate chems or non reactive
compounds), and the higher section for milling oxidizer+fuel mixtures
like BP. Both can work at same time, without interference. Separate
motors with remotely controlled variable RPM will be used. These will
be placed inside the box, under the higher milling section. So much
for the mill itself. Any comments or ideas for such construction?

Now about the jar. So far, I have found (and bought) a 11cm diameter,
25 cm length PVC tube with end caps. However, after some Googling in
rec.pyrotechnics, i found out that milling would take about 8 hours.
Is it correct? Now I'm trying to find PVC tube of diameter of ~15 cm
(very hard to find ;( ). Would it make the milling process faster? I
mean I'm not sure what diammeter jar shall I use. 15cm somehow seems
to be a better option (faster & more space), however harder to find.

The media: in case of 11cm dia jar, I'd use 12mm dia/20mm length
cylinders; in case of 15cm jar - 15mm dia/25mm length cylinders. I
intentionaly haven't mentioned the metal yet, I'll talk about it
later. The question here that bothers me, is are such sizes of media
suitable for such jars? I've found lot's of info about making ball
mill's, however didn't find the way for calculating the the size of
media according to the size of jar. I've only found a formula to
calculate the RPM of a mill.

The metal of the media: since I couldn't find balls of any suitable
metal larger than 8mm, I'm making my own cylinders. Probably lead.
Gonna drill some holes in wood, poor molten lead and wait for it to
cool. Found it in some ones post here. Brilliant idea! Yesterday I
came up with another idea: take copper tube, fill it with molten lead,
and cut into cylinders after cooling down. However, today I found out
that I'm not the first with such idea. Someone has already mentioned
it here, and someone else said it ain't gonna work (the lead would
become loose inside, and milled powder would be trapped between Cu and
Pb). Maybe anyone has tried to do it? I know Cu is bad for milling
some chems, but I'd use it for BP only. Or how about using Al tube
instead of Cu?

So overall, I'll repeat the questions that I don't know or could not
find any answers to:

1. The construction of the mill (I know it is a very big topic, maybe
just some ideas or smth ;) );
2. Would increasing jar's diametter from 11 to 15 (or even more) cm be
a wise decision? Would the milling be faster? Would the powder be
finer/same/coarser?
3. What would be the optimal dimensions of milling cylinders for a 11
or 15 cm dia jar? Or even better, how to calculate them according to
the diammeter of jar?
4. Has anyone tried to use copper (or some other) tube filled with
lead?
5. And last question: what is antimony? ;) I believe it's some kind of
metal, right? Where it is used in everyday life? I want to harden my
lead, but dunno where to get that antimony stuff ;)

Any comments or suggestions are welcome and highly appreciated. Thank
you in advance. RoCkaZ
Lost Yankee
2003-08-12 07:40:28 UTC
Permalink
I use 6"ID sch. 80 PVC. Wheel weights (free for the hauling) are hard
lead (antimony). To flux the mealted lead use bees wax. WATCH FLAME
UP. This will keep you from making softer lead. Ball size for my mill
is 3/4" dia. I used a brass candle stick holder for the mold,
producing 4-5 per minute. The mill action will "round off" the
"balls". RPM for my mill is 90. Fill the canister with balls to over
1/2 full when horizontal. Many mills have "kicker" ribs glued to the
ID to help the balls action. Mill time for BP is around 3 hours.
Please stay away from anything but lead. Check AFN for more details.
And most of all, keep learning the easy way! Do a search on Lloyd
Sponenburgh.
Post by RoCkaZ
Hi there,
me and my friend are making our very first ball-mill. I've done a lot
of googling and reading, and decided to make a mill, that would look
http://www2.omnitel.net/rokas/ball_mill.jpg
http://www2.omnitel.net/rokas/ball_mill_demo.avi (1.8MB)
You can see the two separate milling sections. The lower section is
supposed to be used for "safe" milling (separate chems or non reactive
compounds), and the higher section for milling oxidizer+fuel mixtures
like BP. Both can work at same time, without interference. Separate
motors with remotely controlled variable RPM will be used. These will
be placed inside the box, under the higher milling section. So much
for the mill itself. Any comments or ideas for such construction?
Now about the jar. So far, I have found (and bought) a 11cm diameter,
25 cm length PVC tube with end caps. However, after some Googling in
rec.pyrotechnics, i found out that milling would take about 8 hours.
Is it correct? Now I'm trying to find PVC tube of diameter of ~15 cm
(very hard to find ;( ). Would it make the milling process faster? I
mean I'm not sure what diammeter jar shall I use. 15cm somehow seems
to be a better option (faster & more space), however harder to find.
The media: in case of 11cm dia jar, I'd use 12mm dia/20mm length
cylinders; in case of 15cm jar - 15mm dia/25mm length cylinders. I
intentionaly haven't mentioned the metal yet, I'll talk about it
later. The question here that bothers me, is are such sizes of media
suitable for such jars? I've found lot's of info about making ball
mill's, however didn't find the way for calculating the the size of
media according to the size of jar. I've only found a formula to
calculate the RPM of a mill.
The metal of the media: since I couldn't find balls of any suitable
metal larger than 8mm, I'm making my own cylinders. Probably lead.
Gonna drill some holes in wood, poor molten lead and wait for it to
cool. Found it in some ones post here. Brilliant idea! Yesterday I
came up with another idea: take copper tube, fill it with molten lead,
and cut into cylinders after cooling down. However, today I found out
that I'm not the first with such idea. Someone has already mentioned
it here, and someone else said it ain't gonna work (the lead would
become loose inside, and milled powder would be trapped between Cu and
Pb). Maybe anyone has tried to do it? I know Cu is bad for milling
some chems, but I'd use it for BP only. Or how about using Al tube
instead of Cu?
So overall, I'll repeat the questions that I don't know or could not
1. The construction of the mill (I know it is a very big topic, maybe
just some ideas or smth ;) );
2. Would increasing jar's diametter from 11 to 15 (or even more) cm be
a wise decision? Would the milling be faster? Would the powder be
finer/same/coarser?
3. What would be the optimal dimensions of milling cylinders for a 11
or 15 cm dia jar? Or even better, how to calculate them according to
the diammeter of jar?
4. Has anyone tried to use copper (or some other) tube filled with
lead?
5. And last question: what is antimony? ;) I believe it's some kind of
metal, right? Where it is used in everyday life? I want to harden my
lead, but dunno where to get that antimony stuff ;)
Any comments or suggestions are welcome and highly appreciated. Thank
you in advance. RoCkaZ
Joe 123
2003-08-14 21:49:46 UTC
Permalink
Are you sure about tire weights being hardened lead?

They seem preetty soft to me.

I have some antimony sulfide and trioxide and was wondering if I melted the
Pb then put one of those salts in to give 5% antimony metal would that work.
I assume the antimony would give up its anion to the Pb and crust out or I
could bubble H2 through the melt to reduce the salt and make water or H2S???
Or do I just add some antimony metal to the melted Pb??

Joe
Post by Lost Yankee
I use 6"ID sch. 80 PVC. Wheel weights (free for the hauling) are hard
lead (antimony). To flux the mealted lead use bees wax. WATCH FLAME
UP. This will keep you from making softer lead. Ball size for my mill
is 3/4" dia. I used a brass candle stick holder for the mold,
producing 4-5 per minute. The mill action will "round off" the
"balls". RPM for my mill is 90. Fill the canister with balls to over
1/2 full when horizontal. Many mills have "kicker" ribs glued to the
ID to help the balls action. Mill time for BP is around 3 hours.
Please stay away from anything but lead. Check AFN for more details.
And most of all, keep learning the easy way! Do a search on Lloyd
Sponenburgh.
Post by RoCkaZ
Hi there,
me and my friend are making our very first ball-mill. I've done a lot
of googling and reading, and decided to make a mill, that would look
http://www2.omnitel.net/rokas/ball_mill.jpg
http://www2.omnitel.net/rokas/ball_mill_demo.avi (1.8MB)
You can see the two separate milling sections. The lower section is
supposed to be used for "safe" milling (separate chems or non reactive
compounds), and the higher section for milling oxidizer+fuel mixtures
like BP. Both can work at same time, without interference. Separate
motors with remotely controlled variable RPM will be used. These will
be placed inside the box, under the higher milling section. So much
for the mill itself. Any comments or ideas for such construction?
Now about the jar. So far, I have found (and bought) a 11cm diameter,
25 cm length PVC tube with end caps. However, after some Googling in
rec.pyrotechnics, i found out that milling would take about 8 hours.
Is it correct? Now I'm trying to find PVC tube of diameter of ~15 cm
(very hard to find ;( ). Would it make the milling process faster? I
mean I'm not sure what diammeter jar shall I use. 15cm somehow seems
to be a better option (faster & more space), however harder to find.
The media: in case of 11cm dia jar, I'd use 12mm dia/20mm length
cylinders; in case of 15cm jar - 15mm dia/25mm length cylinders. I
intentionaly haven't mentioned the metal yet, I'll talk about it
later. The question here that bothers me, is are such sizes of media
suitable for such jars? I've found lot's of info about making ball
mill's, however didn't find the way for calculating the the size of
media according to the size of jar. I've only found a formula to
calculate the RPM of a mill.
The metal of the media: since I couldn't find balls of any suitable
metal larger than 8mm, I'm making my own cylinders. Probably lead.
Gonna drill some holes in wood, poor molten lead and wait for it to
cool. Found it in some ones post here. Brilliant idea! Yesterday I
came up with another idea: take copper tube, fill it with molten lead,
and cut into cylinders after cooling down. However, today I found out
that I'm not the first with such idea. Someone has already mentioned
it here, and someone else said it ain't gonna work (the lead would
become loose inside, and milled powder would be trapped between Cu and
Pb). Maybe anyone has tried to do it? I know Cu is bad for milling
some chems, but I'd use it for BP only. Or how about using Al tube
instead of Cu?
So overall, I'll repeat the questions that I don't know or could not
1. The construction of the mill (I know it is a very big topic, maybe
just some ideas or smth ;) );
2. Would increasing jar's diametter from 11 to 15 (or even more) cm be
a wise decision? Would the milling be faster? Would the powder be
finer/same/coarser?
3. What would be the optimal dimensions of milling cylinders for a 11
or 15 cm dia jar? Or even better, how to calculate them according to
the diammeter of jar?
4. Has anyone tried to use copper (or some other) tube filled with
lead?
5. And last question: what is antimony? ;) I believe it's some kind of
metal, right? Where it is used in everyday life? I want to harden my
lead, but dunno where to get that antimony stuff ;)
Any comments or suggestions are welcome and highly appreciated. Thank
you in advance. RoCkaZ
Old Dog
2003-08-15 15:26:57 UTC
Permalink
Post by Joe 123
Are you sure about tire weights being hardened lead?
They seem preetty soft to me.
I have some antimony sulfide and trioxide and was wondering if I melted the
Pb then put one of those salts in to give 5% antimony metal would that work.
I assume the antimony would give up its anion to the Pb and crust out or I
could bubble H2 through the melt to reduce the salt and make water or H2S???
Or do I just add some antimony metal to the melted Pb??
Joe
If you can substitute rust for iron metal... Why would you waste good (and
expensive!) antimony sulfide when you can just buy antimony?

-Rich
Joe 123
2003-08-15 18:06:38 UTC
Permalink
Just didnt want to buy any as I have alot of the oxide. And I dont have any
use for the oxide. But assuming I do get some Sb will it dissolve easily?
I have experience with Cu in Pb. Working in a circuit board making place
one of my duties was to remove excess Cu from the solder. It required good
temperature control and long hours to crystalize out. I dont want to
attempt this project and it take days on the burner to get the Sb into
solution. Not to mention the mixing aspect of it. I simply want to make my
hardend Pb balls harder. Everything turns grey and it seems to affect my
formulas (BP kinda slow).

Thanks Joe
Post by Old Dog
Post by Joe 123
Are you sure about tire weights being hardened lead?
They seem preetty soft to me.
I have some antimony sulfide and trioxide and was wondering if I melted the
Pb then put one of those salts in to give 5% antimony metal would that work.
I assume the antimony would give up its anion to the Pb and crust out or I
could bubble H2 through the melt to reduce the salt and make water or H2S???
Or do I just add some antimony metal to the melted Pb??
Joe
If you can substitute rust for iron metal... Why would you waste good (and
expensive!) antimony sulfide when you can just buy antimony?
-Rich
Anders V
2003-08-29 15:40:23 UTC
Permalink
Post by Joe 123
Just didnt want to buy any as I have alot of the oxide. And I dont have any
use for the oxide. But assuming I do get some Sb will it dissolve easily?
No, I'm fairly sure you'll have to use some flux. It's in the archive
somewhere. I remember something about it being a messy, smelly story...
But why not try to get it already alloyed in the form of .45 reloads
from some gunshop? You don't need a license to buy those even here in
Sweden. I assume that's the case in Italy as well.

And I still think you should get 15mm brass rod instead. I got
mine for about $8 per meter from a Swedish mail order company.
Don't think they ship all over the EU though. I could look into
it if you're interested.
Post by Joe 123
I have experience with Cu in Pb. Working in a circuit board making place
one of my duties was to remove excess Cu from the solder. It required good
temperature control and long hours to crystalize out. I dont want to
attempt this project and it take days on the burner to get the Sb into
solution. Not to mention the mixing aspect of it. I simply want to make my
hardend Pb balls harder. Everything turns grey and it seems to affect my
formulas (BP kinda slow).
Thanks Joe
Post by Old Dog
Post by Joe 123
Are you sure about tire weights being hardened lead?
They seem preetty soft to me.
I have some antimony sulfide and trioxide and was wondering if I melted
the
Post by Old Dog
Post by Joe 123
Pb then put one of those salts in to give 5% antimony metal would that
work.
Post by Old Dog
Post by Joe 123
I assume the antimony would give up its anion to the Pb and crust out or
I
Post by Old Dog
Post by Joe 123
could bubble H2 through the melt to reduce the salt and make water or
H2S???
Post by Old Dog
Post by Joe 123
Or do I just add some antimony metal to the melted Pb??
Joe
If you can substitute rust for iron metal... Why would you waste good (and
expensive!) antimony sulfide when you can just buy antimony?
-Rich
Anders V
2003-09-04 00:11:07 UTC
Permalink
What do you mean by flux? I know what flux is for soldering purposes, same
stuff?
Not same stuff, but same principle. I'm not sure of the composition. I
have a vague memory of some evil fluoride based compound, but I could be
wrong. Could someone else please fill me in here?
I did buy musket balls from gun store 0.49 cal but only slightly harder than
lead fishing weights. Do you think reloads would be harder? The gun guys
dont know anything about composition of reloads or musket balls and they
wont let you open container to scratch.
The reloads I bought (cal. .45) where VERY hard. No mantle, just basic
pistol ammunition flat tipped slugs. I suspect around 5..10
% antimony. However, they were not factory made, the gun shop owner buys
them from some oldtimer who has been alloying the stuff for decades.

The gun shop owner actually phoned the guy on my request, but he
only revealed the presence of antimony, not the percentage. Trade
secret, I suppose....
Post by Anders V
Post by Joe 123
Just didnt want to buy any as I have alot of the oxide. And I dont have
any
Post by Anders V
Post by Joe 123
use for the oxide. But assuming I do get some Sb will it dissolve
easily?
Post by Anders V
No, I'm fairly sure you'll have to use some flux. It's in the archive
somewhere. I remember something about it being a messy, smelly story...
But why not try to get it already alloyed in the form of .45 reloads
from some gunshop? You don't need a license to buy those even here in
Sweden. I assume that's the case in Italy as well.
And I still think you should get 15mm brass rod instead. I got
mine for about $8 per meter from a Swedish mail order company.
Don't think they ship all over the EU though. I could look into
it if you're interested.
Post by Joe 123
I have experience with Cu in Pb. Working in a circuit board making
place
Post by Anders V
Post by Joe 123
one of my duties was to remove excess Cu from the solder. It required
good
Post by Anders V
Post by Joe 123
temperature control and long hours to crystalize out. I dont want to
attempt this project and it take days on the burner to get the Sb into
solution. Not to mention the mixing aspect of it. I simply want to
make my
Post by Anders V
Post by Joe 123
hardend Pb balls harder. Everything turns grey and it seems to affect
my
Post by Anders V
Post by Joe 123
formulas (BP kinda slow).
Thanks Joe
Post by Old Dog
Post by Joe 123
Are you sure about tire weights being hardened lead?
They seem preetty soft to me.
I have some antimony sulfide and trioxide and was wondering if I melted
the
Post by Old Dog
Post by Joe 123
Pb then put one of those salts in to give 5% antimony metal would that
work.
Post by Old Dog
Post by Joe 123
I assume the antimony would give up its anion to the Pb and crust out
or
Post by Anders V
Post by Joe 123
I
Post by Old Dog
Post by Joe 123
could bubble H2 through the melt to reduce the salt and make water or
H2S???
Post by Old Dog
Post by Joe 123
Or do I just add some antimony metal to the melted Pb??
Joe
If you can substitute rust for iron metal... Why would you waste good
(and
Post by Anders V
Post by Joe 123
Post by Old Dog
expensive!) antimony sulfide when you can just buy antimony?
-Rich
Old Dog
2003-08-15 15:26:54 UTC
Permalink
Thank you Lost Yankee. Could you explain in more detail the following
To flux the mealted lead use bees wax. WATCH FLAME UP.
It's eithet my poor English or lack of knoledge, but I don't
understand it ;) And yes, I've read lots of Lloyd's posts, too bad I
cannot get his book...
I think he just meant that you should keep your skin well away from the pot or
well-covered, because at high temperatures the wax *could* ignite and spatter.

-Rich
Anders V
2003-08-14 23:17:22 UTC
Permalink
Post by RoCkaZ
Hi there,
me and my friend are making our very first ball-mill. I've done a lot
of googling and reading, and decided to make a mill, that would look
http://www2.omnitel.net/rokas/ball_mill.jpg
It's hard to tell from the picture, but it looks as though you
intend to mount the motors inside a hermetically sealed space.
This would result in heat buildup which could destroy the motor(s)
unless you build in some kind of ventilation system utilizing
active cooling (i.e. fans).
Post by RoCkaZ
http://www2.omnitel.net/rokas/ball_mill_demo.avi (1.8MB)
You can see the two separate milling sections. The lower section is
supposed to be used for "safe" milling (separate chems or non reactive
compounds), and the higher section for milling oxidizer+fuel mixtures
like BP. Both can work at same time, without interference. Separate
motors with remotely controlled variable RPM will be used. These will
be placed inside the box, under the higher milling section. So much
for the mill itself. Any comments or ideas for such construction?
Why two motors? You can use one, fitted with a 2-belt pulley. Then
you could drive both compartments with a single engine. To me, this
seems much cheaper since motors are, well, non-cheap.
Post by RoCkaZ
Now about the jar. So far, I have found (and bought) a 11cm diameter,
25 cm length PVC tube with end caps. However, after some Googling in
rec.pyrotechnics, i found out that milling would take about 8 hours.
Is it correct? Now I'm trying to find PVC tube of diameter of ~15 cm
(very hard to find ;( ). Would it make the milling process faster? I
mean I'm not sure what diammeter jar shall I use. 15cm somehow seems
to be a better option (faster & more space), however harder to find.
My jar is 150mm ID, 200mm height, screw-on lid with rubber O-ring
sealing. Works like charm, makes milled BP in around 4 hours.
Post by RoCkaZ
The media: in case of 11cm dia jar, I'd use 12mm dia/20mm length
cylinders; in case of 15cm jar - 15mm dia/25mm length cylinders. I
intentionaly haven't mentioned the metal yet, I'll talk about it
later. The question here that bothers me, is are such sizes of media
suitable for such jars? I've found lot's of info about making ball
mill's, however didn't find the way for calculating the the size of
media according to the size of jar. I've only found a formula to
calculate the RPM of a mill.
I'm not sure, but 15mm media works well for me.
Post by RoCkaZ
The metal of the media: since I couldn't find balls of any suitable
metal larger than 8mm, I'm making my own cylinders. Probably lead.
Gonna drill some holes in wood, poor molten lead and wait for it to
cool. Found it in some ones post here. Brilliant idea! Yesterday I
came up with another idea: take copper tube, fill it with molten lead,
and cut into cylinders after cooling down. However, today I found out
that I'm not the first with such idea. Someone has already mentioned
it here, and someone else said it ain't gonna work (the lead would
become loose inside, and milled powder would be trapped between Cu and
Pb). Maybe anyone has tried to do it? I know Cu is bad for milling
some chems, but I'd use it for BP only. Or how about using Al tube
instead of Cu?
Don't bother. I bought a 5m length of 15mm diameter brass rod and
cut it into approx. 330 small cylinders, 15mm long. For BP, they make a
fantastic job and you don't have to worry about lead contamination
in your milled product.
Post by RoCkaZ
So overall, I'll repeat the questions that I don't know or could not
1. The construction of the mill (I know it is a very big topic, maybe
just some ideas or smth ;) );
2. Would increasing jar's diametter from 11 to 15 (or even more) cm be
a wise decision? Would the milling be faster? Would the powder be
finer/same/coarser?
3. What would be the optimal dimensions of milling cylinders for a 11
or 15 cm dia jar? Or even better, how to calculate them according to
the diammeter of jar?
4. Has anyone tried to use copper (or some other) tube filled with
lead?
5. And last question: what is antimony? ;) I believe it's some kind of
metal, right? Where it is used in everyday life? I want to harden my
lead, but dunno where to get that antimony stuff ;)
Back when I was using lead media, I cast them from cal .45 hard
shot. It cost me about $25 for 8kg's of antimony/tin alloyed lead.
Post by RoCkaZ
Any comments or suggestions are welcome and highly appreciated. Thank
you in advance. RoCkaZ
RoCkaZ
2003-08-15 08:23:07 UTC
Permalink
Anders V <***@linuxmailNOSPAM.org> wrote in message news:<6MU_a.19945$***@newsb.telia.net>...

http://www2.omnitel.net/rokas/ball_mill.jpg
Post by Anders V
It's hard to tell from the picture, but it looks as though you
intend to mount the motors inside a hermetically sealed space.
This would result in heat buildup which could destroy the motor(s)
unless you build in some kind of ventilation system utilizing
active cooling (i.e. fans).
Yes, the motors will be inside the "box". Probably sealed. I've been
thinking of installing a simple cooler. And if you say it's neccesary,
then I will ;)
Post by Anders V
Why two motors? You can use one, fitted with a 2-belt pulley. Then
you could drive both compartments with a single engine. To me, this
seems much cheaper since motors are, well, non-cheap.
Two motors, because (IMHO) the RPM would significally vary if one or
both sections will be used (because of greater load). To prevent this,
a much more powerfull motor should be used, wich is more expensive. I
can get two used suitable motors at a low price. And another advantage
is the possibility to control the RPM of each of the motors
individualy.
Post by Anders V
My jar is 150mm ID, 200mm height, screw-on lid with rubber O-ring
sealing. Works like charm, makes milled BP in around 4 hours.
OK, you've persuaded me. FINALY I've found 160mm PVC jar. Damn, that
was hard to get. Still, I have left o 11cm dia/30cm length PVC tube
with all end caps & stuff. It's a pitty to waste it, so probably one
section will be smaller with a 110mm dia tube, and another bigger with
160mm tube. Any ideas, where smaller tube can have advantages over
larger one? =]
Post by Anders V
I'm not sure, but 15mm media works well for me.
Well, it means it should work well for me too. What about length?
15-20-25mm?
Post by Anders V
Don't bother. I bought a 5m length of 15mm diameter brass rod and
cut it into approx. 330 small cylinders, 15mm long. For BP, they make a
fantastic job and you don't have to worry about lead contamination
in your milled product.
I couldn't find brass rods. I think I'm gonna stick with lead
cylinders for now...
Post by Anders V
Back when I was using lead media, I cast them from cal .45 hard
shot. It cost me about $25 for 8kg's of antimony/tin alloyed lead.
Thank you Anders.
RoCkaZ
2003-08-16 13:46:28 UTC
Permalink
Post by RoCkaZ
Post by Anders V
Why two motors? You can use one, fitted with a 2-belt pulley. Then
you could drive both compartments with a single engine. To me, this
seems much cheaper since motors are, well, non-cheap.
Two motors, because (IMHO) the RPM would significally vary if one or
both sections will be used (because of greater load). To prevent this,
a much more powerfull motor should be used, wich is more expensive. I
can get two used suitable motors at a low price.
If they're not powerful enough, how can they be "suitable"?
They're powerfull enough to turn one cylinder, but not powerfull
enough to turn two of them without loosing RPM.
Post by RoCkaZ
And another advantage
is the possibility to control the RPM of each of the motors
individualy.
And why would you want to do this?
To make the mill more universal. I like making things universal. If
I'm gonna use cylinders of differnt dia, then the RPM would also vary,
and that way I can adjust it. Besides, making variable RPM costs just
a couple of $ more, so why the hell not? ;)
-Rich
Old Dog
2003-08-16 16:45:01 UTC
Permalink
Post by RoCkaZ
Post by RoCkaZ
Post by Anders V
Why two motors? You can use one, fitted with a 2-belt pulley. Then
you could drive both compartments with a single engine. To me, this
seems much cheaper since motors are, well, non-cheap.
Two motors, because (IMHO) the RPM would significally vary if one or
both sections will be used (because of greater load). To prevent this,
a much more powerfull motor should be used, wich is more expensive. I
can get two used suitable motors at a low price.
If they're not powerful enough, how can they be "suitable"?
They're powerfull enough to turn one cylinder, but not powerfull
enough to turn two of them without loosing RPM.
Post by RoCkaZ
And another advantage
is the possibility to control the RPM of each of the motors
individualy.
And why would you want to do this?
To make the mill more universal. I like making things universal. If
I'm gonna use cylinders of differnt dia, then the RPM would also vary,
and that way I can adjust it. Besides, making variable RPM costs just
a couple of $ more, so why the hell not? ;)
No particular reason - I just can't seem to understand why you don't want to
spend the money to get a proper mill motor that won't burn out under load, but
want to add unnecessary speed controls to make the speed infinitely variable for
some reason. It might make sense if you were using an infinite number of
different diameter mill jars - but you're not, because there aren't. So what's
the point?

-Rich
RoCkaZ
2003-08-17 19:11:34 UTC
Permalink
Post by Old Dog
No particular reason - I just can't seem to understand why you don't want to
spend the money to get a proper mill motor that won't burn out under load, but
want to add unnecessary speed controls to make the speed infinitely variable for
some reason. It might make sense if you were using an infinite number of
different diameter mill jars - but you're not, because there aren't. So what's
the point?
-Rich
I have two jars (one 11cm dia, other 16cm), and I think I'm gonna be
using both of them. However getting o good powerfull motor is a BIG
PROBLEM so far. I've only found two (used) motors, that (hopefully)
have enough power for 1 jar (just found, haven't bought them yet). I
live in such place, where things are hard to get. I am still looking
for a good and powerfull motor. So the motor part of the mill still
remains undecided yet. This is just a sketch, and until I'm gonna
start building the mill, I believe something will change. And variable
RPM is just $5 more. Or maybe I won't install it at all. Now I'm
waiting for my next salary, so I can finally start putting things
together.
Anders V
2003-08-29 15:33:11 UTC
Permalink
Post by RoCkaZ
Post by Old Dog
No particular reason - I just can't seem to understand why you don't want to
spend the money to get a proper mill motor that won't burn out under load, but
want to add unnecessary speed controls to make the speed infinitely variable for
some reason. It might make sense if you were using an infinite number of
different diameter mill jars - but you're not, because there aren't. So what's
the point?
-Rich
I have two jars (one 11cm dia, other 16cm), and I think I'm gonna be
using both of them. However getting o good powerfull motor is a BIG
PROBLEM so far. I've only found two (used) motors, that (hopefully)
have enough power for 1 jar (just found, haven't bought them yet). I
live in such place, where things are hard to get. I am still looking
for a good and powerfull motor. So the motor part of the mill still
remains undecided yet. This is just a sketch, and until I'm gonna
start building the mill, I believe something will change. And variable
RPM is just $5 more. Or maybe I won't install it at all. Now I'm
waiting for my next salary, so I can finally start putting things
together.
You'll NEED to "overkill" when choosing the motor. It's going to
have to run continiously (sp?) for very long periods.

My motor was a brand new industrial strength AC motor,
specs:
1300rpm
0.75kW max output
and even it gets hot after a 10-hour milling session, with only
8kg of brass media and 1kg of BP compund in the jar. Also
noteworthy is that I've intentionally placed the motor on
top of the ball mill, with free airflow.

I got it for (hmmm, calculating) the equivalent of
approx. US $80.

IMHO, you'll pay dear when you buy cheap when it comes to
motors. Remember that it'll have to run for very long
time periods, and the lesson could cost you the price
for those two used motor plus the expense of a new,
powerful one.

BTW, yes, my jar is composed of both a 150mm PVC pipe and
a 150-->100 converter with a screw-on lid. Those where NOT
cheap =(.

Good luck with your mill.

/A
Lloyd E. Sponenburgh
2003-09-01 12:01:04 UTC
Permalink
Um, just an aside, here...

Almost all commercial-duty motors get hot. Most are rated for a 40-degree
Celsius rise above ambient. That's 104 degrees Fahrenheit ABOVE the
surrounding air temperature. So, for an 'average' indoor application, about
180F.

LLoyd
Post by Anders V
My motor was a brand new industrial strength AC motor,
1300rpm
0.75kW max output
and even it gets hot after a 10-hour milling session, with only
8kg of brass media and 1kg of BP compund in the jar. Also
noteworthy is that I've intentionally placed the motor on
top of the ball mill, with free airflow.
David Brown
2003-08-16 17:15:13 UTC
Permalink
I am curious as to what type motors you have AC, DC, Brushless, Inductive
and what method of speed control you plan on using? I had similar ideas when
I was making my first mill and after getting feedback from the group I ended
up trashing my original design and just made a simple mill large enough to
handle two 6-inch jars on the same roller. After wasting a lot of time
trying to over complicate the construction I ended up using the design you
can see on Dan Williams tool page. This design takes hours to build not
days. Your construction skills and access to tools may be better than mine
but this method will get you up and running quickly.

http://www.wecreate4u.net/dwilliams/top.html
Post by RoCkaZ
Post by RoCkaZ
Post by Anders V
Why two motors? You can use one, fitted with a 2-belt pulley. Then
you could drive both compartments with a single engine. To me, this
seems much cheaper since motors are, well, non-cheap.
Two motors, because (IMHO) the RPM would significally vary if one or
both sections will be used (because of greater load). To prevent this,
a much more powerfull motor should be used, wich is more expensive. I
can get two used suitable motors at a low price.
If they're not powerful enough, how can they be "suitable"?
They're powerfull enough to turn one cylinder, but not powerfull
enough to turn two of them without loosing RPM.
Post by RoCkaZ
And another advantage
is the possibility to control the RPM of each of the motors
individualy.
And why would you want to do this?
To make the mill more universal. I like making things universal. If
I'm gonna use cylinders of differnt dia, then the RPM would also vary,
and that way I can adjust it. Besides, making variable RPM costs just
a couple of $ more, so why the hell not? ;)
-Rich
Joe 123
2003-09-02 17:52:34 UTC
Permalink
When picking out a motor make sure it is a common one. It really sucks when
your used motor goes kaput and it was some weird design and you cant find
another one. Get one that is common and since your getting used ones get
two or three.

Im sure I could do some research on this question im about to ask but hoping
for a quick no brainer type answer::

What is the difference of two 1 amp motors when one is 2-3x the size of the
other. Same RPMs, both rated continuous, same voltage. only visual
difference is the size. ???

Joe
That sounds pretty over-engineered for just a lousy ball mill.
I made mine using a 50 Watt induction motor from a fan, which is
technically
totally wrong (except that it is a 100% duty cycle rated motor), yet it
works fine.
Instead of purchasing an expensive multi-hundred Watt universal motor
why
not try a smaller cheap motor from a junked appliance. You can piece
together a pair (or more) of primitive mills in hours if you really need
the
capacity. Geared down as much as a ball mill is I doubt you'll actually
need hundreds and hundreds of Watts anyway, even for 10 kg loads.
Alan, keep in mind that 1-HP represents an electrical power of
746-Watts plus electrical losses and other inefficiencies that exist
in the motor. Consequently, a 50-Watt motor is outputting less than
0.07-HP (about 1/15-HP).
While this may be marginally adequate to turn a very small rock
polisher, it is clearly inadequate to run a ball mill of any useful
size.
Since you can generally purchase small, used fractional horsepower
motors in 1/4 - 1/3 HP ratings quite easily and cheaply (circa $5-$10
in most parts of the US) and since the performance of the machine is
largely defined by the capacity of the motor powering it, cheaping out
on the motor does not seem to be a reasonable way to reduce overall
cost.
Take a look at the motor that Dan Williams is using for his ball mill.
It appears to be an old washing machine motor that you can probably
locate for free at most dumps. Still, it probably is capable of
supplying 1/3-HP.
Harry C.
Lloyd E. Sponenburgh
2003-09-03 11:33:41 UTC
Permalink
Yeppers! I have an old F.E. Reed 12" lathe with a 2HP "Repulsion Motor".
I have a pool pump with a 2HP GE motor... that motor is about 7" o.d., and
weighs about 30lb. The older motor (sold by Sears, no less) is about 14"
o.d., and tilts the scale at over 175lb!!!

LLoyd
Older motors of the same capacity are generally larger and more robust
than
newer designs. The older motors will generally handle a larger load.
Even
though they might both say 1/4 HP for example, the new one may overheat or
strain driving the same load that the older motor handles easily.
PyroLeo
2003-09-03 19:07:27 UTC
Permalink
It's a shame isn't it. It makes me wonder if something has changed along the
way in how motor horsepower is rated? Is it possible that older motors were
traditionally under-rated?

Years ago I worked in refrigeration. If we needed to replace a motor on an old
belt-driven compressor, we always had to size up to a higher horsepower motor
for the new replacement.

Leo
----------------
Post by Lloyd E. Sponenburgh
Yeppers! I have an old F.E. Reed 12" lathe with a 2HP "Repulsion Motor".
I have a pool pump with a 2HP GE motor... that motor is about 7" o.d., and
weighs about 30lb. The older motor (sold by Sears, no less) is about 14"
o.d., and tilts the scale at over 175lb!!!
LLoyd
Older motors of the same capacity are generally larger and more robust
than
newer designs. The older motors will generally handle a larger load.
Even
though they might both say 1/4 HP for example, the new one may overheat
or
strain driving the same load that the older motor handles easily.
Harry Conover
2003-09-04 01:11:42 UTC
Permalink
Post by Lloyd E. Sponenburgh
Yeppers! I have an old F.E. Reed 12" lathe with a 2HP "Repulsion Motor".
I have a pool pump with a 2HP GE motor... that motor is about 7" o.d., and
weighs about 30lb. The older motor (sold by Sears, no less) is about 14"
o.d., and tilts the scale at over 175lb!!!
LLoyd
Lloyd, welcome to the club! Those old timers knew how to build motors
and equipment that actually are good for a lifetime.

My Atlas 12" lathe (which I purchase on eBay to fabricate fireworks
tools) arrived today. Hate to say it, but that damn machine is so well
bult that it will outlive me, as will its motor.

With respect to ball mills, often the older the motor is, the better.

Harry C.
Joe 123
2003-09-11 14:15:24 UTC
Permalink
Hey Harry,

I just got a 50ton press w/ 12"x18" platens, a couple weeks ago (free) and
havent figured out what to use it for. Its amazing what a little patients
and determination will yield. darn thing weighs almost 1000Lbs and required
me to rent an engine lift and I had to drop it in my yard, permenantly,
untill I get a fork lift. anyway I want to make rockets but dont have any
tooling. I want to make crossets and comets but dont have the tooling. I
want to make stars but dont have the tooling. If you want to make me some
tooling I will trade you a charcoal maker or something else:).

Joe
Post by Harry Conover
Post by Lloyd E. Sponenburgh
Yeppers! I have an old F.E. Reed 12" lathe with a 2HP "Repulsion Motor".
I have a pool pump with a 2HP GE motor... that motor is about 7" o.d., and
weighs about 30lb. The older motor (sold by Sears, no less) is about 14"
o.d., and tilts the scale at over 175lb!!!
LLoyd
Lloyd, welcome to the club! Those old timers knew how to build motors
and equipment that actually are good for a lifetime.
My Atlas 12" lathe (which I purchase on eBay to fabricate fireworks
tools) arrived today. Hate to say it, but that damn machine is so well
bult that it will outlive me, as will its motor.
With respect to ball mills, often the older the motor is, the better.
Harry C.
Old Dog
2003-09-12 02:02:18 UTC
Permalink
If you need tooling, why don't you just buy it? http://www.wolterpyrotools.com/


-Rich
Post by Joe 123
Hey Harry,
I just got a 50ton press w/ 12"x18" platens, a couple weeks ago (free) and
havent figured out what to use it for. Its amazing what a little patients
and determination will yield. darn thing weighs almost 1000Lbs and required
me to rent an engine lift and I had to drop it in my yard, permenantly,
untill I get a fork lift. anyway I want to make rockets but dont have any
tooling. I want to make crossets and comets but dont have the tooling. I
want to make stars but dont have the tooling. If you want to make me some
tooling I will trade you a charcoal maker or something else:).
Joe
Post by Harry Conover
Post by Lloyd E. Sponenburgh
Yeppers! I have an old F.E. Reed 12" lathe with a 2HP "Repulsion
Motor".
Post by Harry Conover
Post by Lloyd E. Sponenburgh
I have a pool pump with a 2HP GE motor... that motor is about 7" o.d.,
and
Post by Harry Conover
Post by Lloyd E. Sponenburgh
weighs about 30lb. The older motor (sold by Sears, no less) is about
14"
Post by Harry Conover
Post by Lloyd E. Sponenburgh
o.d., and tilts the scale at over 175lb!!!
LLoyd
Lloyd, welcome to the club! Those old timers knew how to build motors
and equipment that actually are good for a lifetime.
My Atlas 12" lathe (which I purchase on eBay to fabricate fireworks
tools) arrived today. Hate to say it, but that damn machine is so well
bult that it will outlive me, as will its motor.
With respect to ball mills, often the older the motor is, the better.
Harry C.
Joe 123
2003-09-13 19:05:11 UTC
Permalink
money

just thought, since Harry got a lathe he might hook me up with some
spindles. Well just trying to make friends.


I will save my pennys and get some later.

Joe
Post by Old Dog
If you need tooling, why don't you just buy it?
http://www.wolterpyrotools.com/
Post by Old Dog
-Rich
Post by Joe 123
Hey Harry,
I just got a 50ton press w/ 12"x18" platens, a couple weeks ago (free) and
havent figured out what to use it for. Its amazing what a little patients
and determination will yield. darn thing weighs almost 1000Lbs and required
me to rent an engine lift and I had to drop it in my yard, permenantly,
untill I get a fork lift. anyway I want to make rockets but dont have any
tooling. I want to make crossets and comets but dont have the tooling. I
want to make stars but dont have the tooling. If you want to make me some
tooling I will trade you a charcoal maker or something else:).
Joe
Post by Harry Conover
Post by Lloyd E. Sponenburgh
Yeppers! I have an old F.E. Reed 12" lathe with a 2HP "Repulsion
Motor".
Post by Harry Conover
Post by Lloyd E. Sponenburgh
I have a pool pump with a 2HP GE motor... that motor is about 7" o.d.,
and
Post by Harry Conover
Post by Lloyd E. Sponenburgh
weighs about 30lb. The older motor (sold by Sears, no less) is about
14"
Post by Harry Conover
Post by Lloyd E. Sponenburgh
o.d., and tilts the scale at over 175lb!!!
LLoyd
Lloyd, welcome to the club! Those old timers knew how to build motors
and equipment that actually are good for a lifetime.
My Atlas 12" lathe (which I purchase on eBay to fabricate fireworks
tools) arrived today. Hate to say it, but that damn machine is so well
bult that it will outlive me, as will its motor.
With respect to ball mills, often the older the motor is, the better.
Harry C.
Harry Conover
2003-09-14 18:28:49 UTC
Permalink
Post by Joe 123
money
just thought, since Harry got a lathe he might hook me up with some
spindles. Well just trying to make friends.
I will save my pennys and get some later.
Joe
Joe, I'll be happy to help you out, but I'm still setting the lathe
up. Beyond that it will likely take me another 6-months to get all of
special lathe gagets that are needed to produce fireworks tooling
(taper attachment, collet set, a greater variety of cutting tools,
etc.), plus some time to hone my machining techniques and skills which
I haven't used in years. Still, it's a bit like riding a
bicycle...once you learn you never forget.

I'll likely start off with fountain tooling, since it's pretty
straight-forward
to produce the required tooling to ram the nozzles and cores. Rocket
tapers are a little more tricky, and require more extensive (and
expensive) lathe tooling.
This is why the sellers of fireworks tooling charge what they do.

By the way, I am doing this strictly as a hobby, and have no intention
of commercially marketing anything I produce. On the other hand, when
I am in a position to do so, I'll certainly consider an equitable
trade of anything I need for anything I can make.

Harry C.
Alan Ruether
2003-09-16 04:42:07 UTC
Permalink
With a little patience, a piece of brass stock and a drill press one can
make some very nice spindles. Now that I think of it I even made some nice
spindles before I had a drill press by chucking the stock into my drill and
holding the drill in a bench vise.
Post by Joe 123
money
just thought, since Harry got a lathe he might hook me up with some
spindles. Well just trying to make friends.
I will save my pennys and get some later.
Joe
Post by Old Dog
If you need tooling, why don't you just buy it?
http://www.wolterpyrotools.com/
Post by Old Dog
-Rich
Post by Joe 123
Hey Harry,
I just got a 50ton press w/ 12"x18" platens, a couple weeks ago
(free)
Post by Joe 123
and
Post by Old Dog
Post by Joe 123
havent figured out what to use it for. Its amazing what a little
patients
Post by Old Dog
Post by Joe 123
and determination will yield. darn thing weighs almost 1000Lbs and
required
Post by Old Dog
Post by Joe 123
me to rent an engine lift and I had to drop it in my yard,
permenantly,
Post by Joe 123
Post by Old Dog
Post by Joe 123
untill I get a fork lift. anyway I want to make rockets but dont have
any
Post by Old Dog
Post by Joe 123
tooling. I want to make crossets and comets but dont have the
tooling.
Post by Joe 123
I
Post by Old Dog
Post by Joe 123
want to make stars but dont have the tooling. If you want to make
me
Post by Joe 123
some
Post by Old Dog
Post by Joe 123
tooling I will trade you a charcoal maker or something else:).
Joe
Post by Harry Conover
Post by Lloyd E. Sponenburgh
Yeppers! I have an old F.E. Reed 12" lathe with a 2HP "Repulsion
Motor".
Post by Harry Conover
Post by Lloyd E. Sponenburgh
I have a pool pump with a 2HP GE motor... that motor is about 7"
o.d.,
Post by Old Dog
Post by Joe 123
and
Post by Harry Conover
Post by Lloyd E. Sponenburgh
weighs about 30lb. The older motor (sold by Sears, no less) is
about
Post by Old Dog
Post by Joe 123
14"
Post by Harry Conover
Post by Lloyd E. Sponenburgh
o.d., and tilts the scale at over 175lb!!!
LLoyd
Lloyd, welcome to the club! Those old timers knew how to build motors
and equipment that actually are good for a lifetime.
My Atlas 12" lathe (which I purchase on eBay to fabricate fireworks
tools) arrived today. Hate to say it, but that damn machine is so well
bult that it will outlive me, as will its motor.
With respect to ball mills, often the older the motor is, the better.
Harry C.
John Gilmer
2003-09-15 11:40:44 UTC
Permalink
While this may be marginally adequate to turn a very small rock
polisher, it is clearly inadequate to run a ball mill of any useful
size.
Really?

What size are we talking about?

Effectively, the motor output is converted to HEAT inside will mill. If
you are really pumping 1/3 hp (about 200 watts) into you mill then it would
become quite hot.

Devices like ball mills are difficult to start but just don't take much
power to run. A modest sized motor with a separate starting winding would
be a pretty good fit.

This type of motor is common in clothes dryers (has anyone considered
converting an electric dryer to a mill?) and dishwashers.

A motor without a starting winding than can start a heavy load will be WAY
oversized for the running load.

Earlier in the thread someone mentioned using a 1500 rpm motor. This is a
"high slip" motor which is good at starting but isn't particularly efficient
under load. (Slip is the difference between actual design speed and "sync"
speed. In the US, "sync" speed is 3600, 1800, 900 rpm, etc. A "low slip"
motor would run at 1750 rpm.)
Lloyd E. Sponenburgh
2003-09-15 18:56:06 UTC
Permalink
Post by John Gilmer
Effectively, the motor output is converted to HEAT inside will mill. If
you are really pumping 1/3 hp (about 200 watts) into you mill then it would
become quite hot.
Well, not quite. You will only pass that much energy from the motor into
the contents of the mill IF the mill absorbs 1/3 hp worth of work in the
process of grinding its contents or itself. Otherwise, the motor just
doesn't produce that much horsepower. (Ain't constant-voltage electric
motors SMART?!!?... constant-current motors are smart in other ways that are
fun, too!)

In fact, a 40lb mill jar (including media) absorbs something under 1/10 hp
under normal circumstances.

But your below is correct, because it takes a heap of torque to get an idle
mill spinning.
Post by John Gilmer
Devices like ball mills are difficult to start but just don't take much
power to run. A modest sized motor with a separate starting winding would
be a pretty good fit.
This type of motor is common in clothes dryers (has anyone considered
converting an electric dryer to a mill?) and dishwashers.
Which is why I recommended a 1/3hp 'dryer motor' in my milling book. It's a
'capacitor-start' (without the cap; just a start winding on a centrifugal
switch), induction-run motor. It isn't terribly efficient when lightly
loaded, but will behave itself just fine in terms of longevity and thermal
problems all the way from unloaded to about 80% of rated capacity.

LLoyd
Joel Corwith
2003-09-15 21:39:08 UTC
Permalink
How big a charge do you put in the dryer?

;)

Joel. phx
Post by Lloyd E. Sponenburgh
Which is why I recommended a 1/3hp 'dryer motor' in my milling book. It's a
'capacitor-start' (without the cap; just a start winding on a centrifugal
switch), induction-run motor. It isn't terribly efficient when lightly
loaded, but will behave itself just fine in terms of longevity and thermal
problems all the way from unloaded to about 80% of rated capacity.
LLoyd
John Gilmer
2003-09-15 22:14:41 UTC
Permalink
Post by Joel Corwith
How big a charge do you put in the dryer?
How dirty is your laundry?
John Gilmer
2003-09-15 21:43:57 UTC
Permalink
Post by Lloyd E. Sponenburgh
Post by John Gilmer
Effectively, the motor output is converted to HEAT inside will mill.
If
Post by Lloyd E. Sponenburgh
Post by John Gilmer
you are really pumping 1/3 hp (about 200 watts) into you mill then it
would
Post by John Gilmer
become quite hot.
Well, not quite. You will only pass that much energy from the motor into
the contents of the mill IF the mill absorbs 1/3 hp worth of work in the
process of grinding its contents or itself. Otherwise, the motor just
doesn't produce that much horsepower. (Ain't constant-voltage electric
motors SMART?!!?... constant-current motors are smart in other ways that are
fun, too!)
Yeah, yeah.

And you seem to know much about the subject. Which means you understand
that these "high slip" motors waste power and aren't a good fit for a ball
mill.
Post by Lloyd E. Sponenburgh
In fact, a 40lb mill jar (including media) absorbs something under 1/10 hp
under normal circumstances.
Yep! That would have been about my guess. Once running, it just doesn't
take much power to keep it rolling along. Folks on a budget might even
consider a drive belt with a torque limiting (a spring loaded tension
device on the tension side of the belt does this nicely.) Or, just use a
very small thermally protected motor and give the mill a shove when you turn
on the power.

But a "high slip" motor on a mill you want to run 24/7? No way!
Post by Lloyd E. Sponenburgh
But your below is correct, because it takes a heap of torque to get an idle
mill spinning.
Post by John Gilmer
Devices like ball mills are difficult to start but just don't take much
power to run. A modest sized motor with a separate starting winding
would
Post by John Gilmer
be a pretty good fit.
This type of motor is common in clothes dryers (has anyone considered
converting an electric dryer to a mill?) and dishwashers.
Which is why I recommended a 1/3hp 'dryer motor' in my milling book. It's a
'capacitor-start' (without the cap; just a start winding on a centrifugal
switch), induction-run motor.
Which means it isn't a capacitor start. The starting winding in these
motors are designed to have a lot of resistance. Since the main winding is
pure inductance at start the high resistance of the "start" winding produces
the necessary phase shift.

The centrifugal switch, unfortunately, produces a spark right at the motor.
This isn't a good idea with pyro! A starting relay, OTOH, can be placed
with the main on/off switch (away from harm's way!)
Post by Lloyd E. Sponenburgh
It isn't terribly efficient when lightly
loaded, but will behave itself just fine in terms of longevity and thermal
problems all the way from unloaded to about 80% of rated capacity.
A true capacitor start (and also, capacitor start, capacitor run - 2 caps)
are also good candidates. The cap start/run motor doesn't "waste" the
start winding once underway.
Post by Lloyd E. Sponenburgh
LLoyd
Alan Yates
2003-09-15 22:10:37 UTC
Permalink
Or, just use a very small thermally protected motor and give
the mill a shove when you turn on the power.
That's the method I use, but apparently that means I am heretic. :-)

Statistically I'd imagine if the thing is going to blow up it will happen
either just at start-up, or towards the end when the charge is very fine,
with a higher probability on the later. So I guess doing so is a bit of a
risk, but still fairly minor? I just make sure I am no where near my mill
for the majority of its runtime (ie only there for its first kick over).

Honestly, it *usually* self starts, maybe one in ten times I need to
approach and encourage it.
--
Alan Yates
http://www.vk2zay.net/
The Moon is Waning Gibbous (76% of Full)
Old Dog
2003-09-16 05:15:20 UTC
Permalink
Post by John Gilmer
Post by Lloyd E. Sponenburgh
Well, not quite. You will only pass that much energy from the motor into
the contents of the mill IF the mill absorbs 1/3 hp worth of work in the
process of grinding its contents or itself. Otherwise, the motor just
doesn't produce that much horsepower. (Ain't constant-voltage electric
motors SMART?!!?... constant-current motors are smart in other ways that
are
Post by Lloyd E. Sponenburgh
fun, too!)
Yeah, yeah.
And you seem to know much about the subject. Which means you understand
that these "high slip" motors waste power and aren't a good fit for a ball
mill.
You mean the author of the definitive work on pyrotechnic ball mills might know
something about the subject? The reason most of the hobby ball mills in use are
often referred to as "Sponenmills"? Yeah, that's a good guess.

-Rich
Lloyd E. Sponenburgh
2003-09-16 11:42:37 UTC
Permalink
"John Gilmer" <***@crosslink.net> wrote in message news:3f663583$0$***@dingus.crosslink.net...
LLoyd said
Post by John Gilmer
Post by Lloyd E. Sponenburgh
Which is why I recommended a 1/3hp 'dryer motor' in my milling book.
It's
Post by John Gilmer
a
Post by Lloyd E. Sponenburgh
'capacitor-start' (without the cap; just a start winding on a centrifugal
switch), induction-run motor.
Which means it isn't a capacitor start. The starting winding in these
motors are designed to have a lot of resistance. Since the main winding is
pure inductance at start the high resistance of the "start" winding produces
the necessary phase shift.
Again, John, not exactly. The motor IS a capacitor-start motor. They are
sold as such; they are wound exactly the same as such (although broken-out
so that it's implied you won't be using a cap). Only, the appliance
manufacturers decided, "why spend an extra $2.00 on a $300.00 dryer?" In an
application where the motor starts, say, once in every three or four hours
of run time -- why, heck, the contacts in the start switch will hold up just
fine, even with that ugly inductive kick and spark that occurs on break.
So... just violently over-current the start winding for a half-second of
every three hours of run, and FERGIT the phase implications!

But your cheap-o motor will last longer if you spring for the cap... On
some of these 'dryer motors', you'll have to do a bit of surgery to break
out leads for the capacitor.

LLoyd
John Gilmer
2003-09-16 13:19:32 UTC
Permalink
Post by Lloyd E. Sponenburgh
LLoyd said
Post by John Gilmer
Post by Lloyd E. Sponenburgh
Which is why I recommended a 1/3hp 'dryer motor' in my milling book.
It's
Post by John Gilmer
a
Post by Lloyd E. Sponenburgh
'capacitor-start' (without the cap; just a start winding on a
centrifugal
Post by John Gilmer
Post by Lloyd E. Sponenburgh
switch), induction-run motor.
Which means it isn't a capacitor start. The starting winding in these
motors are designed to have a lot of resistance. Since the main
winding
Post by Lloyd E. Sponenburgh
is
Post by John Gilmer
pure inductance at start the high resistance of the "start" winding
produces
Post by John Gilmer
the necessary phase shift.
Again, John, not exactly. The motor IS a capacitor-start motor.
No. Don't be silly.
Post by Lloyd E. Sponenburgh
They are
sold as such; they are wound exactly the same as such (although broken-out
so that it's implied you won't be using a cap).
Oh yeah? SO you are saying that if we just short out the capacitor in a
capacitor start motor it will "start?" (It, will "start," of course, as in
start to smoke!)
Post by Lloyd E. Sponenburgh
Only, the appliance
manufacturers decided, "why spend an extra $2.00 on a $300.00 dryer?" In an
application where the motor starts, say, once in every three or four hours
of run time -- why, heck, the contacts in the start switch will hold up just
fine, even with that ugly inductive kick and spark that occurs on break.
Gad! That type of motor is routinely used in dishwashers. These motors
start and stop every few minutes. Some units have TWO run windings
(forward and reverse) and one start winding.
Post by Lloyd E. Sponenburgh
So... just violently over-current the start winding for a half-second of
every three hours of run, and FERGIT the phase implications!
But your cheap-o motor will last longer if you spring for the cap... On
some of these 'dryer motors', you'll have to do a bit of surgery to break
out leads for the capacitor.
These motors are built to order for the appliance. There just aren't any
"extra" leads inside the motor.
Post by Lloyd E. Sponenburgh
LLoyd
Lloyd E. Sponenburgh
2003-09-16 16:55:21 UTC
Permalink
Post by John Gilmer
These motors are built to order for the appliance. There just aren't any
"extra" leads inside the motor.
True. I said "surgery", not "exposing of un-needed hidden wires". <G>

(some intended-to-be-capacitor-start motors will, indeed, start with the cap
shorted. And yes, they draw way too much current when treated that way.)

You are right that the dedicated-purpose motors have a higher resistance
start winding than, say, a compressor duty motor. But check out how GE
lists these motors. Even though you and I both know they'll never see a
puff (oops! dated myself with that one!) of start capacitor, they're listed
as 'capacitor-start' in GE's literature.

Not arguing, just bantering.

LLoyd
John Gilmer
2003-09-16 17:48:43 UTC
Permalink
Post by Lloyd E. Sponenburgh
You are right that the dedicated-purpose motors have a higher resistance
start winding than, say, a compressor duty motor. But check out how GE
lists these motors. Even though you and I both know they'll never see a
puff (oops! dated myself with that one!) of start capacitor, they're listed
as 'capacitor-start' in GE's literature.
Not arguing, just bantering.
I'm not sure that "puff" dates you all that much.

I first heard the term in 1977 (and it had to be explained to me.) I used
it as necessary up through the early 80s. Since then, pf's never entered
into conversations.


You have the advantage over me. I don't have any motor catalog at my
finger tips.

I guess we agree on motors!
Post by Lloyd E. Sponenburgh
LLoyd
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