Solo skimming while pouring---a skimmer that mounts to my trolley

I work solo at my foundry. I could get green volunteers I am sure many times, but the actual help they can provide vs the risk of them injuring themselves or me is significant and the distraction of conversation is a problem as is the problem of Covid isolation. So, I chose to work alone. The only problem working alone presents that I have yet to solve is the lack of someone to hold back those last bits of slag that often seem to appear between final skimming and starting to pour. It surely would be nice to have someone there for the minute or so of pour time.

I think I have a possible solution. Monday I spent dreaming up and fabrication a skimmer that will attach to my trolley. It won't be as good as a capable assistant but it comes at low cost with respect to injury risk, conversation, and Covid transmission.

What I put together is a rammable refractory paddle that, at the very last minute I will attach to the hoop that holds my crucible in my pouring trolley (wheeled shank if you will). The assembly consisting of a paddle of BluRam suspended from a couple adjustable articulated support arms will be popped into a tapered socket lug welded to the hoop that carries the crucible. The vertical 1/2 diameter support arm has a taper cut on its lower end which inserts into a corresponding taper cut into a lug welded to the hoop. The taper is about 2 degrees on each side for a 4 degree included angle. This taper was chosen as it is self-locking with a single tap from a hammer on the top end and also easily popped loose with a tap on the lower end of the rod which protrudes 1/4" below the socket lug.

I intend to adjust the height, rotation, verticality, and centering of the paddle prior to firing up the furnace. All sliding and articulating adjustments will be cinched up with locking levers so that all I have to do as a very last step prior to pouring is use a tong to drop the paddle and rod assembly into the lug and give it a single rap to lock it in place.

I made the paddle so it will protrude about 3 inches down into the molten metal and sit pretty close to the crucible sides and thus cause metal from deep in the pool to flow out the spout rather than just letting the very top and most contaminated layer of metal flow preferentially. Well, that's the theory anyway.

Here is the general setup without the paddle yet installed.

The horizontal arm with hoop removed from trolley temporarily`




The paddle was made from BluRam with an embedded piece of split 5/16" steel bar. How well this interface of steel and BluRam holds up remains to be seen. I did make sure that the split extended out of the refractory to give a little more chance for differential expansion coefficients of steel and refractory.

I intend to heat the paddle up with a weed burner to glowing red just before opening the furnace and pulling the crucible. I will leave the burner trained on the paddle as I skim the crucible and then at the last moment drop the assembly into the socket. And then I will cross my fingers.....

I'll add some photos of the paddle tomorrow. Right now it is in the kiln at around 1600 degrees. With a little luck I will pour tomorrow.

Denis

 

That's getting close to those fancy "Teapot" "bottom pour" crucibles, probably cost a king's ransom.

 

I am certainly trying to emulate the functionality of the teapot-style crucibles. I assume they are outrageously expensive and likely a practically custom item. Using them in my foundry is not likely to happen.

Denis

 

Here are a couple pics ofpaddle.
I poked plenty of vent holes in it.

Detail of the split in the 5/16” rod

I drew in the location of the bent rod segments more or less


Denis

 

Neat idea Denis. It makes me wonder though why "pro shop" videos I've seen opt for the skilled dross-man instead of an appliance.
I have visions of the possibility of over-topping with a too-full crucible. I'm very interested to see the demonstration!

Pete

 

Well sure,Pete, if I had a professional shop with several guy standing around you can be sure I would hand one of the skimmer as I was pouring. However, being by myself, I hope that this will be better than nothing. That remains to be seen.

I lit my furnace 20 mins ago...

Denis

 

Of course. As a production guy I'm always considering lowering operating costs, ie labor.

Pete

 

The aftermath.
Seemed to do its job. Nothing blew up or broke. I was able to unseat the taper after the pour with one blow...did not stick. I’m cleaning up the crime scene now. More details later.

BTW, no overtopping——this time.

Denis

 

Some comments on the initial run with this device:
It did do what it was designed to do quite well.

I will make the fixing screws more robust as there is a significant flotation force exerted by the dense iron vs the much less dense refractory. The 6-32 set screw in particular needs to be larger. The wall of the node that it is inserted in is too light to take a 1/4-20 set screw, so I will be welding on a lug to accommodate a 1/4-20 set screw. I may do away with the bent 1/4-20 screws and use SHCS’S in their place as I should be able to snug them down more firmly more easily than the bent screws. As it was everything held together but it felt like it did so without a lot of margin.

The paddle itself held up better than I had hoped. I did not get it preheated to robustly glowing—-just to barely glowing around the edges as I did not want to take more than a few minutes at the end of the heat or risk overheating my melt. So, I need to get the preheat sussed out better. Maybe I’ll put it on a small Coleman single burner I have 20 mins prior to pour. As it was, it seemed to do just fine as it suffered no evident ill effects. I was prepared for it to break due to the abrupt immersion in 2600 degree iron. Nope. It did not seem to faze it.

I really like the tapered socket attachment for the vertical arm. It is very quick and secure.

I have been thinking about using a simple 3/4 circumference ring that might hold the paddle and just be dropped onto the crucible upper rim. If such a ring had 3 or 4 fingers maybe 1.5” in length that would extend down the sides of the crucible to hold it in place it might be another quick way to attach a paddle support to the crucible. It will have to be heavy enough to prevent float though or it would need some other means of latching to the crucible.

With respect to paddle materials, one other thought rattling around is wouldn’t it be nice to be able to use a section of a retired crucible for the paddle? Just how to fix such a section to a support rod is not yet obvious to me. But, it seems like the crucible material would be ideal as it is so heat resistant. And the other question is what practical method would one use to section the retired crucible. It is likely to be difficult to cut.

Thinkin out loud here. And listening for ideas.

Denis

 

https://www.ebay.com/i/161008882387...MIrbfz6_3s6wIVyEXVCh3IIA22EAYYASABEgJO3_D_BwE

 

Filters.
Yes, I have some laying around somewhere. Intuitive but not very practical for typical sand casting. Easier to use in bound sand applications. But still require some significant molding adjustments and extra steps to use them. Think I will try to get the skimming down. Maybe there are secrets to their use.

Do you have experience with them, Jason?

Denis

 

Filters. Yes, I have a few sitting around somewhere. I have felt they were impractical for green sand casting at my foundry.

Do you have experience with them, Jason?

Denis

 

Haven't had a chance to try them.. My bronze is super clean so dont really see a need. Cast iron, sure.. just not bronze.

 

Here is the "New and Improved" version of the support pieces. Note that the round suspending piece is replace by a heavier rectangular-section piece and single bent bolt fixing bolts are now two 1/4-20 SHCS's. I can be sure nothing will move with that setup.

Will be giving it another trial by fire in a few days.



BTW, I got 5 good straight edges out of that pour. Four 8" prism-style and one 18" prism style.

Denis

 

I used the skimmer again today with its beefed-up connectors. It performed just as it should and did let the crucible act a lot like a "teapot" style bottom-pouring crucible. The connections seemed very solid and the refractory tolerated the dunking from a 70 degree status to direct iron immersion without a hiccup. I could see slag stuck to the back (non-spout) side of the skimmer indicating it did indeed hold back some slag. That's all I can ask. It was quick to attach and after the pour and popped right out of the socket with a single light hammer tap. I do not anticipate any more alterations unless something unforeseen shows up. I do intend to keep using it.

Maybe I can make a video next time. I was busy the whole melt since it was pretty short at 80 mins for 50 pounds. I had to drop in cores in the two molds, bolt them up, and hoist them down and transport them out to the furnace area as well as mind the fuel levels, skim, add metal to the pot, etc. etc. Seemed like I never stopped moving the whole time for more than a minute here and there. Spectacularly Beautiful Fall day at 70 degrees and deep blue sky and slight breeze.

Denis

 

The navy foundry book describes how to make a refractory lined tea pot, Why isn't that more common?

 

I have 2 of the bottom pour crucibles I got with the furnace. Not all that complicated, looks like they just put a rod down the side when they molded the crucible. So I can’t see why it would be terribly more expensive. Does seem to work well, the pour doesn’t take any dross with it.

 

If anyone knows of where to buy bottom-pouring Super Salamander crucibles, pLease let me know. If they know where they can be purchased for a price comparable to the standard A20 or A25 please please let me know.

Denis

 

Pretty neat! While we used hand ladles to pour we added a few things like that but what we found when we watched them pouring with it was that the stuff it was catching was near the end of the pour and most of it would never have made it to the casting because the casting was nearly full and the gating system would be full and most of it would float in the pour cup. Looks like it will work well for what you are trying to do.