Home-Made Bottom Pour - Tall Skinny Wall Mount

[turbo1889]

I am figuring on making myself up a bottom pore casting pot that's worth a darn. Going to be heated by a propane burner and I want lots of head pressure on the pore spout for full fill out for big (7/8oz up to 1-5/8oz.) shotgun slug molds. And I also want to send all the fumes and exhaust up and out the roof chimney style. This is what is on the drawing board so far:

http://castboolits.gunloads.com/picture.php?albumid=134&pictureid=768

24" length of 3" diameter steel water pipe with cap welded on the bottom end suspended inside a 5" sheet-metal stove pipe. Burner mounted below. Stove pipe both keeps the burners flame tight up against the side of the pipe for maximum heat transfer efficiency and serves to vent the exhaust and fumes off the top of the pipe up and away. Clean, fluxed lead ingots added to the pot with metal tongs through flip open sheet metal access flap above. Pour spout made either by drilling block of steel and welding it to side of pipe or using smaller pipe T-joint and extension and welding that to a plate steel bracket and then the assembly to the side of the pipe. Figure on turning down a length of threaded rod to just a few thous. over the inside diameter of the pore spout hole and than spinning it in with lapping compound for a super tight fit -- then just need to attach a down pressure weight or spring to the plunger and a lever to lift it to pour. I plan on making some strong brackets and mounting the whole thing to the wall of the shop above the work bench.

What do you guys think of the design?

What diameter would be about right for the pour spout hole?

[mike in co]

constant head pressure is better achieved by a large dia over just tall. a thin tall pot will have the pour pressure changing very quickly as you pour large slugs. a large dia means less height change as the pours are made. the density of the slugs will vary more with the tall than with a short fat. for volume consider two pots. refill and heat one while using the other.

mike in co

[montana_charlie]

I can see where something resembling 'head pressure' plays a role when running a compressible material through (say) a powder measure.
I really can't understand the infatuation with 'head pressure' when the subject is casting bullets.

When a liquid is poured into a fixed volume, it will fill all of that space.
You cannot 'pack it tighter'...and attempting to do so will not 'make it heavier'.

True, the liquid must displace any other substance in the space, but that is just air in this case. Even water is dense enough (without added 'head pressure') to quickly displace air, if the venting is adequate.

I think you guys could safely stop hoarding head pressure...leaving more available for those who need it to spin turbines, grind corn, or whatever.

CM

[MtGun44]

Head pressure will fill out the mold better, overcomes the surface tension of the
liquid alloy which tends to round off the corners. More tin and more heat both
lower surface tension, but head pressure definitely works. Sometimes I have
cast with the pot spout sealed against the sprue plate, and it definitely will improve
fill out. That said, I don't think it is a big deal if you add some tin and keep the metal
hot and the mold clean and vented properly.

Bill

[NSP64]

looks like a mess waiting to happen. The spout will cool down and clog.

[HeavyMetal]

I see a couple small porblems with your basic idea.

First mounting this on the wall, lots of heat is gonna come off this thing unless you have an Asbestos wall I wouldn't.

Instead I'd make this a stand alone device that I could move to the center of the room, patio, driveway when I needed to use it.


Second, unless your locked in to a specific burner size I'd do 24 inch by 5 inch on the main body. Much less chance of weight varience. However: how you gonna flux this thing?

Instead of just capping the end square with the body I think I'd make the bottom at an angle pointed at the inside entrance to the spout. This should creat maximum pressure at the spout per weight of alloy in the pot.

Third I think I'd make the spout shorter and maybe on a slight down angle. I think that 90 degree and long spout your drawing shows is gonna create both cooling and clogs.

Forth I'd make sure there was a "heat Channel" of some type to keep that spout hot. You got the right idea on a plunger but I'd extend the handle away from the spout and make a foot or hand control to open and close rather than try to do something up close with my hand, glove or no glove!

[1Shirt]

For what ever it is worth, I would forget the whole idea and wait until I had saved enough to buy a commercial pot. Until then I would use a cast iron whatever on the kitched stove and a ladle.:
1Shirt!:coffee:

[captaint]

I don't know, Turbo. Looks like the potential problems might outweigh the advantages. Even you're going with clean ingots, you'll still want to flux that mix. Guess I just don't see why a typical pot wouldn't work fine. Good to see you're giving it some thought, tho. Good luck. Mike

[mike in co]

I can see where something resembling 'head pressure' plays a role when running a compressible material through (say) a powder measure.
I really can't understand the infatuation with 'head pressure' when the subject is casting bullets.

When a liquid is poured into a fixed volume, it will fill all of that space.
You cannot 'pack it tighter'...and attempting to do so will not 'make it heavier'.

True, the liquid must displace any other substance in the space, but that is just air in this case. Even water is dense enough (without added 'head pressure') to quickly displace air, if the venting is adequate.

I think you guys could safely stop hoarding head pressure...leaving more available for those who need it to spin turbines, grind corn, or whatever.

CM
yes you can pack it tighter!

cast some boolits with a full pot. set them aside., run the pot to almost empty, and cast some more.( keep temp the same)

now go weigh the two groups. the ave weight of the first will be more than the last poured.

like letting the the temp vary, it does affect the boolit weight.

if you dont weight sort your boolits you will never know. you will just wonder why when there seem to be flyers in your shooting.

mike in co

[briang]

yes you can pack it tighter!

cast some boolits with a full pot. set them aside., run the pot to almost empty, and cast some more.( keep temp the same)

now go weigh the two groups. the ave weight of the first will be more than the last poured.

like letting the the temp vary, it does affect the boolit weight.

if you dont weight sort your boolits you will never know. you will just wonder why when there seem to be flyers in your shooting.

mike in co

I really doubt that what you're seeing is the lead packing tighter. I think it's slightly rounded edges in the lighter boolits, so slight you can't even see it. .5 grain of lead isn't a whole lot, escpailly when spread out over a boolit.

[Triggerhappy]

One other issue to consider is the heat transfer to the pot from the burner. A pot like this will not have the surface area on the bottom to allow it to absorb enough heat to keep the top melted. Since it has tall walls I'd bet that you'll have issues getting / keeping it hot enough. The long side walls will release a lot of heat.

Just a thought.

TH

[uncle joe]

unless you keep adding ingots one at a time,(as you drain one add one), to keep the level high I see a huge splash when you add one to a low level. You may also want to calculate the pressure that will be on the spout with a full level also. Lead is much heavier than water and you may have a disaster waiting to happen when you open the spout for the first time. You will have to calculate the area of the spout opening and multiply it by the hight, or level of the liquid to get the area of lead over the spout opening, then use the weight per volume of lead for the pressure.
Even with my little 20 pound lee pot I can see a big difference in pressure of the pour between a full pot and a low level one. As for the heat if you insulate the pipe to help keep the heat inside it should work.
my 2c
uj

[kendall yates]

As far as wanting more "head pressure" I don't think you will like the outcome. My bottom pour is 12x12x12 and has a lot of pressure when it has about 300 pounds or more and causes the lead to have air bubbles because it is moving so fast air gets trapped as it goes into the mold. Just my 2 cents, no gurantee this happens to you.

[turbo1889]

Okay, thanks for the input so far -- I want to get most of the bugs worked out of this at the drawing board stage. Secondly, I guess I should have stated this up front, I have several commercial ladle cast pots along with a good old fashioned burner and cast iron pot set-up, and I also have/had commercial bottom pour pots. The commercial bottom pour pots work just fine for when you’re casting like 200gr.-ish bullets. However, when it comes to casting 500 grain plus slug molds the commercial bottom pore set-ups become both in-adequate and annoying. Bottom pour is suppose to be faster and easier than ladle casting not a futile exercise in trading both speed and proper fill-out for a little easier operation compared to a good “line-up, tip, pressure pore” type ladle set-up. That pitiful little stream of lead just doesn't fill the molds up near as fast as I would like and also creates quality control issues when the bottom half of the pour is already starting to solidify and the top half still isn't full -- this happens especially on my bigger 600 to 1000 grain slug molds. So I am trying to build a bottom pore pot that will suit my needs not just the average 200-300 grain bullet size casters needs. Now I know that flow rate is controlled by two factors -- the size of the hole in the bottom of the pot and the head pressure. Expanding the hole size substantially will leave me with a thick slow stream -- sounds like a mess spilling lead over the mold and have it running off the spruce plate and down the sides to me. Figured a normal size hole in the bottom of the pot with more head pressure would work better, sort of squirt the lead into the mold through the hole in the spruce plate. I was planning on making the bottom of the pour valve with a taper to match the approximate angle of spruce plate holes and then holding the mold tight to the bottom and opening her up. Basically I would be doing mild pressure injection casting rather than gravity pore casting. Almost guaranteed full fill out and none of that annoying "can whistle yankee doodle twice over while I wait for the mold to fill". Well that's sort of an exaggeration but you get the idea.

While I was at it building a custom bottom pore pot I figured I mize well make it to my other preferences as well. Propane gas fired - not electric, Semi-permanently mounted for safety right where I need it with the pour spout about 8 to 12 inches above the work bench of an enclosed and somewhat weather-proof shop. The easiest way to do that would be to use some sort of angle iron brackets to mount it to the wall behind the bench with the proper clearance from the wall of course. The idea of setting up an indoor casting pot presents ventilation issues -- have to vent the propane exhaust anyway. Why not just send both the propane exhaust and the fumes off the top of the pot up and out with a stove pipe chimney. Fresh air gets sucked in from below to feed the fire so any fumes from the actual lead in the mold will get sent up and away as well. On a cold, rainy, windy day an indoor casting operation sounds mighty nice. If I do it right and set it up just like you would install a furnace with the proper clearances and everything it should be almost completely safe and not a fire hazard like most casting pot set-ups are. No chance of the pot being knocked over and swilling molten lead every-where either.

I will be making some changes to the design taking into account feed back so far and will post the update for further critique.

[HeavyMetal]

Looking forward to the update and good luck!

[runfiverun]

have you considered a funell shape with a bit of a tube at the bottom ?
just something to keep the flame against a bit more? it might help keep the head pressure a bit more consistent too.
you will wanna have spotlessley clean alloy in this thing too.

[briang]

What about running a small tube type burner up along the pot to help keep it warm?

[mikenbarb]

That propane burner will quickly suck all your O2 out of the room so keep the windows and doors pinned open because it will throw off carbon monoxide also. Plus look into a flashback arrestor if you build it because if the molten lead drips on the burner orifice it may cause a flashback. Its remote but it could happen. You will also need some way of cleaning out the bottom to get the crud buildup out after a while.

[leadman]

How would a design similar to a gas water heater with the flame going up thru the center work?
Just a thought.

[turbo1889]

Okay, here is the re-design so far, version #3:

http://castboolits.gunloads.com/picture.php?albumid=134&pictureid=771

1. - Potential spout cooling and clogging ~ Issue addressed by putting spout on cap on end of elbow.

2. - Possibility of excessive head pressure at 24" ~ Issue addressed by reducing head pressure to 12"+, still plenty more than factory pots.

3. - Un-even head pressure as lead level drops ~ Issue addressed by horizontal pipe extension to hold main volume of lead and maintain consistent head pressure within a couple inches or so.

4. - Fluxing ~ Horizontal pipe extension allows a push pull stir rod.

5. - Splash factor when adding lead ~ No longer an issue with horizontal pipe extension.

6. - Clean out ~ All joints welded except bottom cap with spout unscrewable with big wrench for clean out.

Other issues mentioned:

~ Ventilation for fresh air - shop is weather proof, definitely not sealed or air proof; plenty of fresh air.

~ Heat transfer to the lead inside the pipe. That is part of the whole idea of enclosing the steel pipe containing the lead (increased to 4" size by the way) inside a sheet metal stove pipe. I'm going to use double wall insulated stove pipe so that it keeps most of the heat around the pipe. Just like a hot-water heater where the flue runs through the center of the tank only this is the reverse -- lead inside the center of the flue. Basically it is a pipe inside a pipe heat exchanger set-up.

Now as far as what I intend to use for a heat source. I am planning on using one of those big flame thrower weed burner torches which means their is going to be like a two plus foot long flame inside flowing around the center pipe containing the lead and up, heat transfer should take place not only on the bottom of the elbow but also for the full length of the pipe. Those things put out a huge amount of BTU, and can empty a 20-lb propane tank FAST when you turn them all the way up so I'm not worried about not having enough heat. Darn things sound like a muffled jet engine. I have one of them to power my smelting pot (size of 5-gal bucket only half as tall) and it heats it up just fine.

[mikenbarb]

Two words, Pro-Melt.;-) Your biggest problem is your going to have a real uneven heat source. I have worked with LPG for years and I would go another route and look into a nice bottom pour. If your stuck on the pipe thing look into the ceramic heat elements from McMaster or Grainger. They can be bent around the pipe for a more consistent heat plus it will be alot safer. The BTU loss due to the large surface area and the venting will be alot and you will need a large burner to keep up with the btu demand and the recovery time. I will see what it says on my LP burner charts for a 4" exhausted heater but I think it will be over a 80,000 BTU setup.