Discussion:
Questions for Lloyd Sponenburgh
(too old to reply)
Michael Newton
2003-11-04 07:33:34 UTC
Permalink
Lloyd,

I was checking out the design of your powder die on Dan Williams fine
web site. It seems like a nice, simple design and I'm sure it works
very well. Of course I have some questions and I was hoping you would
be kind enough to comment on them.

The first question is about the pistons being cast with sand. Wouldn't
it be a bit safer if these were cast without the sand? I understand
you used the sand to decrease the cost of the castings, but I'm
wondering if the sand might cause a spark if the surface grains were
to somehow come loose and be crushed or come into contact with other
sand grains.

The second question is also about the pistons. I was looking around on
the web site www.onlinemetals.com. This company sells 6061-T6 aluminum
extruded round rod in diameters up to 8". The 3" diameter material
costs $39.46 per foot, but they will also sell it pre-cut to any
length (+- 1/8") that you desire. A 2" length would cost $8.56, and a
3" length would be $12.84. I'm not sure what the materials would cost
to cast the pistons as you did, but the cost of aluminum pistons
doesn't seem prohibitively expensive to me. I'm also not enthusiastic
about the idea of casting polyester resin, simply because I have had
no experience with it. The question then is would aluminum pistons be
a suitable replacement for the polyester/sand pistons?

The company also sells Acetal (Delrin) and Nylon round extrusions up
to 8" in diameter, but both of these materials are actually quite a
bit more expensive than the aluminum.

Any comments or suggestions will be greatly appreciated.

Regards,
Michael Newton
Lloyd E. Sponenburgh
2003-11-04 12:39:57 UTC
Permalink
Post by Michael Newton
Lloyd,
The first question is about the pistons being cast with sand. Wouldn't
it be a bit safer if these were cast without the sand? I understand
you used the sand to decrease the cost of the castings, but I'm
wondering if the sand might cause a spark if the surface grains were
to somehow come loose and be crushed or come into contact with other
sand grains.
I chose a cast piston in order to make it fit the sleeve closely without
machining. Mostly, the sand is to strengthen the polyester by forming an
inexpensive composite matrix. I've not crushed one of those pistons at up
to 16 tons applied pressure. The only drawback I've seen so far is that the
pistons are not machinable with any but carbide or diamond tools. Proper
casting eliminates the need to machine the cylinder. 'Tiger hair' (chopped
Fiberglas about 1" long) mixed with short choppings will work, but it's
unruly in handling, and takes a LOT of material to beef up the polyester.
Post by Michael Newton
The second question is also about the pistons. I was looking around on
the web site www.onlinemetals.com. This company sells 6061-T6 aluminum
extruded round rod in diameters up to 8". The 3" diameter material
costs $39.46 per foot, but they will also sell it pre-cut to any
length (+- 1/8") that you desire. A 2" length would cost $8.56, and a
3" length would be $12.84. I'm not sure what the materials would cost
to cast the pistons as you did, but the cost of aluminum pistons
doesn't seem prohibitively expensive to me.
I'm also not enthusiastic
about the idea of casting polyester resin, simply because I have had
no experience with it.
It's easy and simple to do. The only caveats are that the mold must not
leak, and one must not use much hardener in a casting with such a large
cross-section. Too much hardener will cause the casting to heat badly
enough to crack during its cure.
Post by Michael Newton
The question then is would aluminum pistons be
a suitable replacement for the polyester/sand pistons?
Aluminum will work fine. Most people do not have the tools to machine large
pieces of metal. That leaves them to make the sleeves fit the pistons,
rather than the other way around. They must fit closely to the mold sleeve.
Also, the pistons require that each have a smoothly polished end, or the
pressed powder will embed into the rough-cut surface. Casting the polyester
against a smooth surface eliminated the need to machine the piston ends. An
alternative would be to use release disks cut from, say, thin aluminum sheet
or stiff plastic such as Mylar (polyester!).
Post by Michael Newton
The company also sells Acetal (Delrin) and Nylon round extrusions up
to 8" in diameter, but both of these materials are actually quite a
bit more expensive than the aluminum.
Both acetal and nylon will deform badly at the pressures required to press
powder to 1.7g/cc. The piston will bulge, tending to jam in the mold and to
deflect your pressing force away from the powder and into the side walls of
the sleeve. Straight polyester resin will crack at those pressures. That's
another reason why I originally chose a composite.
Post by Michael Newton
Any comments or suggestions will be greatly appreciated.
Regards,
Michael Newton
Michael Newton
2003-11-04 23:11:12 UTC
Permalink
Lloyd,

Thank you very much for the information. I'm still not sure which
material I'll use, but there's no rush because I don't have a press
yet. <g> I do like the idea of aluminum pistons though.

Regards,
Michael Newton
Dan Cutter
2003-11-04 17:12:17 UTC
Permalink
Post by Michael Newton
Lloyd,
I was checking out the design of your powder die on Dan Williams fine
web site. It seems like a nice, simple design and I'm sure it works
very well. Of course I have some questions and I was hoping you would
be kind enough to comment on them.
The first question is about the pistons being cast with sand. Wouldn't
it be a bit safer if these were cast without the sand? I understand
you used the sand to decrease the cost of the castings, but I'm
wondering if the sand might cause a spark if the surface grains were
to somehow come loose and be crushed or come into contact with other
sand grains.
The second question is also about the pistons. I was looking around on
the web site www.onlinemetals.com. This company sells 6061-T6 aluminum
extruded round rod in diameters up to 8". The 3" diameter material
costs $39.46 per foot, but they will also sell it pre-cut to any
length (+- 1/8") that you desire. A 2" length would cost $8.56, and a
3" length would be $12.84. I'm not sure what the materials would cost
to cast the pistons as you did, but the cost of aluminum pistons
doesn't seem prohibitively expensive to me. I'm also not enthusiastic
about the idea of casting polyester resin, simply because I have had
no experience with it. The question then is would aluminum pistons be
a suitable replacement for the polyester/sand pistons?
The company also sells Acetal (Delrin) and Nylon round extrusions up
to 8" in diameter, but both of these materials are actually quite a
bit more expensive than the aluminum.
Any comments or suggestions will be greatly appreciated.
Regards,
Michael Newton
I'm not Lloyd by any stretch, but I did make the die from Dan
Williams site. Instead of sand for the piston and base, I bought a 32
oz can of fiberglass resin and a square of fiberglass cloth from Home
Depot. Shred the cloth into one inch fibers. I used about two cups
of compressed fiberglass fibers mixed with about 24 oz. of the resin.
Pour it into the molds and two hours later you have a piston and base
that can be cut and sanded to perfection, tough as nails, and
non-sparking. Dan C.
Michael Newton
2003-11-04 23:15:42 UTC
Permalink
Post by Dan Cutter
I'm not Lloyd by any stretch, but I did make the die from Dan
Williams site. Instead of sand for the piston and base, I bought a 32
oz can of fiberglass resin and a square of fiberglass cloth from Home
Depot. Shred the cloth into one inch fibers. I used about two cups
of compressed fiberglass fibers mixed with about 24 oz. of the resin.
Pour it into the molds and two hours later you have a piston and base
that can be cut and sanded to perfection, tough as nails, and
non-sparking. Dan C.
Dan,

Thanks for the information. How did you shred the cloth into one inch fibers?

Regards,
Michael Newton
Dan Cutter
2003-11-05 05:26:04 UTC
Permalink
Post by Michael Newton
Post by Dan Cutter
I'm not Lloyd by any stretch, but I did make the die from Dan
Williams site. Instead of sand for the piston and base, I bought a 32
oz can of fiberglass resin and a square of fiberglass cloth from Home
Depot. Shred the cloth into one inch fibers. I used about two cups
of compressed fiberglass fibers mixed with about 24 oz. of the resin.
Pour it into the molds and two hours later you have a piston and base
that can be cut and sanded to perfection, tough as nails, and
non-sparking. Dan C.
Dan,
Thanks for the information. How did you shred the cloth into one inch fibers?
Regards,
Michael Newton
Trauma shears (heavy duty scissors.) Then pull the cloth apart
with your fingers. Mix with the resin/hardener till you have an even
matrix. It goes off fairly quickly, so get it into the molds right
away. If it isn't perfect you can cut it down later. Dan C.
Brian Redmond
2003-11-04 17:15:13 UTC
Permalink
Michael,

Don't know if you saw my post, but I have a powder die exactly like the
one on Dan's site (and my site). I don't need it anymore since I've
upgraded. As far as the sand sparking, I have pressed all my powder so
far with it and have not had any problems. I used ABS pipe instead of
PVC simply because I had some lying around. I was also hesitant to try
casting fiberglass, but it really was quite simple. If you still want
to try making your own (though I do like the idea of the aluminum
rammers - onlinemetals.com is a great resource), check out my site at
http://www.beachredmonds.com/pyro/bpdie.html
If you'd like mine, I'm happy to send it to you for just the cost of
postage.

Brian
Post by Michael Newton
Lloyd,
I was checking out the design of your powder die on Dan Williams fine
web site. It seems like a nice, simple design and I'm sure it works
very well. Of course I have some questions and I was hoping you would
be kind enough to comment on them.
The first question is about the pistons being cast with sand. Wouldn't
it be a bit safer if these were cast without the sand? I understand
you used the sand to decrease the cost of the castings, but I'm
wondering if the sand might cause a spark if the surface grains were
to somehow come loose and be crushed or come into contact with other
sand grains.
The second question is also about the pistons. I was looking around on
the web site www.onlinemetals.com. This company sells 6061-T6 aluminum
extruded round rod in diameters up to 8". The 3" diameter material
costs $39.46 per foot, but they will also sell it pre-cut to any
length (+- 1/8") that you desire. A 2" length would cost $8.56, and a
3" length would be $12.84. I'm not sure what the materials would cost
to cast the pistons as you did, but the cost of aluminum pistons
doesn't seem prohibitively expensive to me. I'm also not enthusiastic
about the idea of casting polyester resin, simply because I have had
no experience with it. The question then is would aluminum pistons be
a suitable replacement for the polyester/sand pistons?
The company also sells Acetal (Delrin) and Nylon round extrusions up
to 8" in diameter, but both of these materials are actually quite a
bit more expensive than the aluminum.
Any comments or suggestions will be greatly appreciated.
Regards,
Michael Newton
Tony Peot
2003-11-04 22:31:02 UTC
Permalink
I have used the Aluminum 3" round stock and it works great. The base can
be any length to accommodate the press. It was quite a bit cheaper than
the prices I have seen here. Making the piston a bit longer aids in
getting the puck out of the PVC without taking the press apart. Any one
interested in using 3" Aluminum can send me an email for a price on desired
lengths.
Post by Brian Redmond
Michael,
Don't know if you saw my post, but I have a powder die exactly like the
one on Dan's site (and my site). I don't need it anymore since I've
upgraded. As far as the sand sparking, I have pressed all my powder so
far with it and have not had any problems. I used ABS pipe instead of
PVC simply because I had some lying around. I was also hesitant to try
casting fiberglass, but it really was quite simple. If you still want
to try making your own (though I do like the idea of the aluminum
rammers - onlinemetals.com is a great resource), check out my site at
http://www.beachredmonds.com/pyro/bpdie.html
If you'd like mine, I'm happy to send it to you for just the cost of
postage.
Brian
Post by Michael Newton
Lloyd,
I was checking out the design of your powder die on Dan Williams fine
web site. It seems like a nice, simple design and I'm sure it works
very well. Of course I have some questions and I was hoping you would
be kind enough to comment on them.
The first question is about the pistons being cast with sand. Wouldn't
it be a bit safer if these were cast without the sand? I understand
you used the sand to decrease the cost of the castings, but I'm
wondering if the sand might cause a spark if the surface grains were
to somehow come loose and be crushed or come into contact with other
sand grains.
The second question is also about the pistons. I was looking around on
the web site www.onlinemetals.com. This company sells 6061-T6 aluminum
extruded round rod in diameters up to 8". The 3" diameter material
costs $39.46 per foot, but they will also sell it pre-cut to any
length (+- 1/8") that you desire. A 2" length would cost $8.56, and a
3" length would be $12.84. I'm not sure what the materials would cost
to cast the pistons as you did, but the cost of aluminum pistons
doesn't seem prohibitively expensive to me. I'm also not enthusiastic
about the idea of casting polyester resin, simply because I have had
no experience with it. The question then is would aluminum pistons be
a suitable replacement for the polyester/sand pistons?
The company also sells Acetal (Delrin) and Nylon round extrusions up
to 8" in diameter, but both of these materials are actually quite a
bit more expensive than the aluminum.
Any comments or suggestions will be greatly appreciated.
Regards,
Michael Newton
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Michael Newton
2003-11-05 07:59:52 UTC
Permalink
Post by Tony Peot
I have used the Aluminum 3" round stock and it works great. The base can
be any length to accommodate the press. It was quite a bit cheaper than
the prices I have seen here. Making the piston a bit longer aids in
getting the puck out of the PVC without taking the press apart. Any one
interested in using 3" Aluminum can send me an email for a price on desired
lengths.
Tony,

What did you use for the sleeves? And, did the aluminum pistons
require any machining to fit the sleeves?

Regards,
Michael Newton
Michael Newton
2003-11-04 23:25:56 UTC
Permalink
Brian Redmond <***@beachredmonds.com> wrote in message news:<***@beachredmonds.com>...
[snip]
If you still want to try making your own (though I do like the idea of the aluminum
rammers - onlinemetals.com is a great resource), check out my site at
http://www.beachredmonds.com/pyro/bpdie.html
Brian,

Where do think I found the link to onlinemetals.com? <g> I love
aluminum. It's a very cool material to work with.
If you'd like mine, I'm happy to send it to you for just the cost of
postage.
I saw your offer in the newsgroup, but I knew it would go fast. Thanks
anyway!

Regards,
Michael Newton
FirmAbs6pk
2003-11-05 00:45:21 UTC
Permalink
I dont think sparking from sand would be much of a problem especially
when the powder you are pressing is going to be moist and is normally
hard to ignite in this state I would think the main thing to be
worried about is applying too much pressure and rupturing your casting
cylinder which *might* send chunks of it flying... but being it a
hydraulic press I'd doubt any particles would get far. from my
experience pressing the powder is pretty safe (in comparison to ball
milling it and corning it) although I'm yet to have an accident in any
of those cases, just appears there is more risk in the latter two.

~Firm
Post by Michael Newton
The first question is about the pistons being cast with sand. Wouldn't
it be a bit safer if these were cast without the sand? I understand
you used the sand to decrease the cost of the castings, but I'm
wondering if the sand might cause a spark if the surface grains were
to somehow come loose and be crushed or come into contact with other
sand grains.
Michael Newton
2003-11-05 09:04:17 UTC
Permalink
Post by FirmAbs6pk
I dont think sparking from sand would be much of a problem especially
when the powder you are pressing is going to be moist and is normally
hard to ignite in this state
Firm,

I don't have any experience with this myself but in Ian Von Maltitz's
book he warns about being complacent with wet black powder. Apparently
it can burn very fast when wet. Naturally there'll be several
variables that come into play; the quality of the powder, the amount
of water, the presence of alcohol, etc, but it's probably not a bad
idea to treat wet powder with the same caution you would dry.
Post by FirmAbs6pk
from my experience pressing the powder is pretty safe (in comparison to ball
milling it and corning it) although I'm yet to have an accident in any
of those cases, just appears there is more risk in the latter two.
Everything I've read so far says that corning is generally considered
to be the most dangerous step. I don't understand this. It's my
understanding that corning consists of crushing the pressed cakes or
pucks into small grains. Unless you're an idiot you will not be
smacking the stuff around on an anvil with a steel hammer. If you're
using a sensible method why should this be more dangerous than any of
the other steps involved? I would think that ball milling would be the
most dangerous step, especially when all of the components are milled
together dry. I wonder if this ‘general consensus' isn't because of
the methods or machines used for corning by commercial manufacturers.
Have you ever heard of anyone having an accident while corning? Want
about milling?

Regards,
Michael Newton
Lost Yankee
2003-11-07 07:59:53 UTC
Permalink
Post by Michael Newton
Post by FirmAbs6pk
I dont think sparking from sand would be much of a problem especially
when the powder you are pressing is going to be moist and is normally
hard to ignite in this state
Firm,
I don't have any experience with this myself but in Ian Von Maltitz's
book he warns about being complacent with wet black powder. Apparently
it can burn very fast when wet. Naturally there'll be several
variables that come into play; the quality of the powder, the amount
of water, the presence of alcohol, etc, but it's probably not a bad
idea to treat wet powder with the same caution you would dry.
Post by FirmAbs6pk
from my experience pressing the powder is pretty safe (in comparison to ball
milling it and corning it) although I'm yet to have an accident in any
of those cases, just appears there is more risk in the latter two.
Everything I've read so far says that corning is generally considered
to be the most dangerous step. I don't understand this. It's my
understanding that corning consists of crushing the pressed cakes or
pucks into small grains. Unless you're an idiot you will not be
smacking the stuff around on an anvil with a steel hammer. If you're
using a sensible method why should this be more dangerous than any of
the other steps involved? I would think that ball milling would be the
most dangerous step, especially when all of the components are milled
together dry. I wonder if this ?general consensus' isn't because of
the methods or machines used for corning by commercial manufacturers.
Have you ever heard of anyone having an accident while corning? Want
about milling?
Regards,
Michael Newton
<The volume of your die is dependant on your needs and available
materials. I use the same die for hollow comets and powder pucks.
Because I shoot 2" (1 3/4" actual) I make 1 1/34" pucks! In this size,
lessor materials will hold up even to 12 tons. Using 1 1/2" thin PVC
with three slits longer then the finished pucks, inside a 2" sch. 80
PVC with one slit, a 2" end cap, two large hose clamps and a 1 1/2"
poly rod, I can press to 1.7g / cc or more. Granted this is a smaller
scale than most pyros will want, but for my set-up (including a 3/16"
steel blast shield) it works fine after 60 pressings. Cost of die =
$7.00 plus labor. Some day I may need 3" dies but not in the near
future!
Lost Yankee

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