Casting a Star Wars Kettlebell?

[Dave Stephens 399]

Fellow followers of the fire: 

 

I exercise with kettlebells, the weights that look like cannon balls with handles. A long time ago a company called ONNIT offered a very small number of Star Wars themed kettlebells. They sold out almost immediately, and there is no indication that they will ever offer them again.

 

Call it a mania brought on by COVID lockdown, I want the Boba Fet kettlebell sufficiently to have started wondering if I could cast one myself?

 

I know nothing about casting iron. Can someone with bladesmith-level tools/forges/etc. reasonably expect to pull of a 50lb cast of iron, or am I engaging in delusions of galaxies far, far away?

 

I've thought about doing it in bronze, but 50 lbs of silicon bronze would be ridiculously expensive. 

 

Any thoughts would be appreciated!

 

Dave

[billyO 150]

this oughtta be fun to watch.....

[James Higson 82]

Also watching with interest. 

 

Do you have the large sand casting gear needed and a vertical crucible furnace?

[Charles dP 423]

It would take a bit of maths (and I’ve only had one cup of coffee) but you could potentially cast a shell out of aluminium or bronze and then cast lead into a central cavity to get up to weight?

[Dave Stephens 399]

8 hours ago, Charles dP said:

It would take a bit of maths (and I’ve only had one cup of coffee) but you could potentially cast a shell out of aluminium or bronze and then cast lead into a central cavity to get up to weight?

Hmm. Interesting idea. Thanks, Charles.

 

James: Nope. I don't have either of those things. I'd need to build the furnace, but it doesn't look any more complicated than a forge build (or am I missing something?)

[Brian Myers 102]

Yeah, I would cast it in aluminum. Use Petro or green sand so you can cast it with a central cavity. Then you can fill that with lead till you hit your weight. Melt that lead and pour it in.

[Dave Stephens 399]

I actually looked up how much 50lbs of silicon bronze would cost. It's less than I thought.  Bronze would look really cool, especially with a patina on it. The wear marks would make it even better.

 

Have just looked up weights. Bronze seems to be heavier than cast iron per cubic inch (.307 for bronze vs. .260 for cast iron), so the size would probably have to be reduced a bit, or a bit of a hollow left in the base.

 

I think I could build a custom flask large enough to fit in my burn out kiln and use satin cast. Definitely can't use vacuum casting, so it would just be a gravity pour. . . . 

 

Why am I even thinking about doing this?  . . . it will be expensive, frustrating, and massively time consuming. 

 

Oh wait, so is everything else I do in bladesmithing . . . right. Okay then. 

 

[Alan Longmire 2,409]

10 hours ago, Dave Stephens said:

so is everything else I do in bladesmithing

 

Indeed!  Carry on, I think that will be awesome in bronze.  

[Brian Dougherty 951]

Yep, you can do this  

I'll hold your beer while you do!

[Jerrod Miller 391]

Can this be done at home?  Yeah, sure.  Would I recommend anybody do it?  No, not hardly.  Do I think YOU can do it?  Absolutely.  

 

As you are well aware, this is going to be one of those things that is going to take a lot of planning up front.  And just like with bladesmithing, I would recommend starting small and working up to it.  Got any bronze-work that you need/want to make for your boat?  For that matter, a couple baby-Yoda 10 pound weights may come in handy, too.  You'll want to practice your pattern and mold making skills, and smaller is definitely way easier than larger.  Pattern shrink and solidification shrink are going to be a little bit of an issue to get right at 50 pounds.  How close do you want to be?  Believe it or not, the cast iron is probably going to be easier, with the only real challenge being to get it hot enough.  The shrink is going to be easier to compensate for and mold and pour defects are going to be easier to avoid.  

 

I wonder how much metal you could melt with your induction forge (with a custom coil to use with a crucible)?  If you know the duty cycle for it I could figure that out for you.  At any rate, I'll see what I can come up with for pattern design for best results for you.  You are going to want to have a friend at hand to help with the pour.  You will need to melt at least 60 pounds, plus the weight of the crucible and handling equipment.  And lifting that quickly and pouring smoothly is not something that you want to try to do alone.  

[Dave Stephens 399]

Thanks Jerrod. 

 

Starting with a smaller kettlebell is a good idea. I've done some casting in the past, but only guard components for swords/knives.

 

Cast iron is easier? Interesting. Still, I think I'm sold on the idea of a bronze kettlebell. It would just be too cool. 

 

The weight doesn't need to be exact +/- 10% is fine. I was going to build the model out of wax then use the Archimedes method of water displacement to determine it's volume, then put the bronze in the water and compare displacement, keep adjusting the volume of the wax model until they were equal. Reasonable approach?

 

Thanks again for the pro advice. 

 

Looking at picking up this setup for the melt rather than building my own. Any thoughts?

 

https://www.amazon.com/Masters-CAPACITY-Crucible-Smelting-KILOGRAM/dp/B08FF3HCLZ/ref=sr_1_16?dchild=1&keywords=large+crucible&qid=1600096096&sr=8-16

 

 

[Jerrod Miller 391]

I am not familiar with that melting set-up, but there are definitely a couple things I can see from the pictures that are worth considering.  In no particular order:

• I have no idea what those tongs are for; certainly not for pulling a full crucible out.  Maybe adding metal to the crucible while it is in the furnace?  You'll need a set of lifting tongs and a set-up for pouring.  
• The insulation seems to be un-coated.  For longevity you will want to coat it, even with a very thin layer of something.  
• There is not a lot of room between the crucible and and the wall.  Hard to reach in and grab the crucible to pull it out.  
• That crucible will not hold 50 pounds of brass/bronze.  

None of these things are necessarily deal breakers.  Just something to think about before purchasing.  

 

Another place I think worth looking at is Foundry101.  While they are in my neck of the woods, I have never been there, or even spoken with them.  But they appear to have nice things (except there website, which isn't as nice as it could be, but has certainly improved in the last few years).  If nothing else it is good to see what else is out there.  I especially like how their furnace comes apart.  

 

I very rough calculation shows you can do about 2.5-3 pounds of steel per kW from an induction supply.  So your 3kW unit could probably do a few pounds with the right coil installed.  And you can make the coils yourself.  

 

If you aren't going to melt/pour all the metal in one go that will certainly change the process.  Still, quite doable.  

[Alan Longmire 2,409]

3 hours ago, Dave Stephens said:

 

Looking at picking up this setup for the melt rather than building my own. Any thoughts?

 

I think you'd be cheaper and better served by building a Jeff Pringle-type Nuclear Marshmallow furnace.  That's just two thicknesses of kaowool wrapped into a cylinder and held with wire. Lid of the same, but with a hole in. Crucible sitting on a firebrick plinth inside, run a blown burner in the bottom at a tangent for a swirl flame.  Can be scaled up. Fire until contents are fully liquid, pull the burner, lift off the lightweight wool furnace body, fit the pouring shank, pour.  These last for several firings.  It's what Jeff uses for wootz runs.  They hold up to impacts and sausage grease quite well.  'Cause you know somebody's gonna grill something over the flame. Invest in a shade 5 face shield and aluminum pants.  

[Dave Stephens 399]

Thanks Jarrod and Alan.

 

Alan: Is there any video/post of Jeff's setup?

 

Jerrod: What do you mean about not melting/pouring in one go? Is there a way to do multiple pours and actually have the bronze fuse together as a solid mass? Seems like if you poured half, then waited until you had another crucible melted, you'd end up with a kettlebell that would break in half at the first bump?

 

Dave

 

[Dave Stephens 399]

Oh, and Jarrod: Thanks for the Foundry101 tip. I've emailed them.

 

[James Higson 82]

11 hours ago, Alan Longmire said:

 They hold up to impacts and sausage grease quite well.  'Cause you know somebody's gonna grill something over the flame. 

 

Well, that's not something I'd immediately consider in the design process while choosing a lining material but now I think about it, surviving sausage grease seems essential  

[Alan Longmire 2,409]

9 hours ago, Dave Stephens said:

Alan: Is there any video/post of Jeff's setup?

 

No video that I know of, but it's appeared at almost every Fire and Brimstone, and also at the 2013 Oakland axe-n-seax.

 

Here it is in Baltimore in its disassembled state for pulling the crucible:

You can just see the end of the burner to the right of the crucible, and that wad of kaowool is the body of the furnace.

 

I know I have more, but here's some from elsewhere:

 

http://elementalforge.com/blog/wp-content/gallery/oasi2013/000300thursdaysmelt.jpg

 

http://elementalforge.com/blog/wp-content/gallery/oasi2013/000301thursdaysmelt.jpg

 

 

You get the idea.  Couldn't be simpler.  

[Jerrod Miller 391]

13 hours ago, Dave Stephens said:

Jerrod: What do you mean about not melting/pouring in one go? Is there a way to do multiple pours and actually have the bronze fuse together as a solid mass? Seems like if you poured half, then waited until you had another crucible melted, you'd end up with a kettlebell that would break in half at the first bump?

There are various techniques to accomplish making a part in multiple pours.  The one I would recommend the most for this project would be to first make a base/central slug.  Then when you have that, it gets placed into a mold like a core and cast the second pour around it.  This does require 2 patterns, and 2 molds, and a bit of time in between the castings.  I've got a few things I have to get done this morning, but then I will try to put a couple drawings together to better explain it.  It is a bit tricky and a single pour is definitely preferred, but that isn't always an option.  

[Jerrod Miller 391]

OK, here is a VERY rough and crude sketch of it.  The brass colored piece is the one you make first.  Get it all cleaned up and it would go into the mold cavity as represented by the blue outline.  The 3 smaller round protrusions will stick into the mold (sand, presumably) and hold up the larger cylinder to float in the middle of the cavity.  When the second pour is done, there will be 3 protrusions out of it that will need to be cleaned up, 2 out the back of the "head", one down the "neck".  The very bottom will also have a visible seam, but the 2 parts will definitely be solidly locked together.  Obviously, there are a variety of ways to shape the internal slug.  You mainly want to take up space, while still leaving as much room as possible for metal to get around it and fill in the details properly.  It can also be done with multiple pre-cast pieces.  I would even highly recommend if you go this route to pre-cast the handle, so it is definitely a solid loop that has the rest of the mass formed around it.  This just occurred to me while typing this.  It is the better plan.  I'll see if I can draw that up quickly, too.  

 

[Jerrod Miller 391]

Something more like this.  Size and sculpt it appropriately.  This would put the worst seams on the very bottom, so you wouldn't see it when sitting on the floor.  You may still get a visible seam around the top of the helmet where the handle comes out.  

 

[Brian Dougherty 951]

Interesting.  Can you pour around something like that cold, or does it need to be preheated?

[Alan Longmire 2,409]

Ooh, with that last one it could even be a three pour casting. Slug, handle, helmet. The shrinkage of the helmet would lock the handle pretty solidly, no?

[Jerrod Miller 391]

8 minutes ago, Brian Dougherty said:

Can you pour around something like that cold, or does it need to be preheated?

Pre-heating would be ideal, but becomes very difficult with sand casting.  A ceramic mold would be the better way, but MUCH more difficult to DIY.  

 

8 minutes ago, Alan Longmire said:

The shrinkage of the helmet would lock the handle pretty solidly, no?

A bit, but I would still recommend a mechanical shape to help lock it in.  

[Alan Longmire 2,409]

I was thinking the handle would have those 90 degree short bits shown...

[Jerrod Miller 391]

Yeah, now that I think about it, maybe it would be best to pour the handle solo first.  Then take that and put it in the mold to make the other spacer.  Then the third mold is the final product.  This way there are a couple really good opportunities to get experience with molding and pouring 20 pounds of brass at a time before the final run.  

 

I honestly tried to download a 3D model of Bobba Fett's helmet, but couldn't find anything that played well with Solidworks.  I now have several that show up in Solidworks, but nothing that allows for feature recognition, just surfaces.  I was really looking forward to designing the whole pattern layout so I could tell Dave actual dimensions for his pattern, so he could be at least close with the first wax version.  Or possibly he could send it out for a 3D printing.  So if anyone has a good solid model of this (or maybe Vader or a storm trooper) then let me know and I can get some practical sizes laid out.