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The Shop => Metal Stuff => Topic started by: vtsteam on February 04, 2021, 05:16:50 PM

Title: Ring Shank Design
Post by: vtsteam on February 04, 2021, 05:16:50 PM
Just moving here from Andrew's induction furnace thread in order not to go too far afield there on this particular subject.

I've brought up an issue I've had with a ring shank during  a few iron pours when emptying the last of a crucible's contents. Generally the pours went well, but a few times the crucible slipped forward in the shank and contacted the mold. That has started me wondering why, and of course how that could be avoided. I don't have the crucible and shank in front of me now as I write this, but as I remember it, the ring was made of round rod, and fit more than half way up the crucible, as is logical.

I'll look for the shank check the fit and try again (cold, without a melt) just to see the tilting action. I stopped using ring shanks after that happened and have since been quite comfortable pouring with my well-fitting lifting tongs for A6 size pours. But I still want to know the cause and  how to avoid that problem.
Title: Re: Ring Shank Design
Post by: vtsteam on February 04, 2021, 05:32:02 PM
yes, I have seen the hinged version, and various other methods of retaining the crucible, all looked time consuming and  dangerous to me. what I am suggesting is a fixed hook, welded to the outside of the shank ring, so that the crucible does not touch it when the shank is at an angle, but the hook naturally falls onto the top of the crucible as the  shank  gets to the stopping point. If I had a crucible I would make one! I could do with one anyway to reduce my alloy collection to usefull ingot size in the forge. Maybe I should order one?
Phil

Remember the ring initially lays on a flat surface and you bring the crucible over and set it down into the ring. Then you slide the ring up until it  fits the tapered crucible.

You cannot pivot the ring when in that position. If you pivot it before that, won't your catch end up some distance ahead of the crucible rim when the crucible is seated? If so it won't prevent the crucible from sliding forward a distance at the end of the pour, which is the big problem because the pour then jumps and misses the mark.

I really think the best solution is just to understand how to shape and size and position a ring to avoid the problem altogether. and I suspect it is also somewhat dependent on the actual crucible shape. They vary. I don't remember for sure which crucible had the problem (if it was one in particular), but I still have some of the old ones to check.
Title: Re: Ring Shank Design
Post by: hermetic on February 05, 2021, 01:29:57 PM
I will try to sketch something up this weekend! The bend at the end of the catch only needs to be small, not even the thickness of the crucible wall, and the shank does not have to lay flat, a slight angle would be all that is required to clear the hook, then a careful lift maintaining the slight angle till the shank meets the side of the taper on the crucible, and at this point the hook should just catch the top lip of the crucible to prevent slip. You must understand that this is a thought experiment, as I have neither shank nor crucible, but have seen the crucibles slip on many occasions on youtube, and thought that this could alleviate the problem.
Phil
Title: Re: Ring Shank Design
Post by: awemawson on February 05, 2021, 03:13:36 PM
The one I remember had a hook with an oval pivot hole that was impaled by a U shape welded to  the ring pointing outwards and horizontal. The hook could pivot up to the crucible lip and due to the oval hole lift a bit more a drop over the edge.

Rather fiddly I thought but  it worked

Have a crude sketch:
Title: Re: Ring Shank Design
Post by: vtsteam on February 05, 2021, 06:55:44 PM
I've got 2 feet of snow blocking the way up hill to my back shed where my ring shank is stored and not in the mood to shovel it yet. So I can't try it out yet on a cold crucible. But I did take a look at some of Ironman's videos, and found a segment where he was pouring an A6 crucible with a ring shank.

This frame from a video shows that his ring is made of flat bar, not round (like mine was) and he has a pretty steep pour going at this point. In the video he actually shakes the last bit out of the crucible.

It looks like the ring is located at about the half way point up the crucible, not two thirds. In this photo, the plinth is stuck to the crucible, which obviously mitigates against the crucible slipping forward. But the crucible would probably have been used for pours before when the plinth was separate.

I'm not drawing any conclusions here about position, but I do believe that a flat bar is better than round re. the slipping problem. If the ring edges are square I think it would naturally be harder for the crucible to slide -- more of a tooth, and less of a pivot than the inside edge of the round bar.

(http://www.sredmond.com/vtsteam/OilFurnace/A6ring1.png)
Title: Re: Ring Shank Design
Post by: vtsteam on February 05, 2021, 07:00:15 PM
Just for interest sake here is the shank lying on the concrete. Notice the nice round heat radiation and splash shield to protect the gloved hand, and allow him to hold closer to the crucible when pouring.

(http://www.sredmond.com/vtsteam/OilFurnace/A6Ring2.png)
Title: Re: Ring Shank Design
Post by: awemawson on February 06, 2021, 02:13:23 AM
If you cut a circle of cardboard and put it on the plinth under the crucible (before firing of course) the carbon from the burnt cardboard stops them sticking together.
Title: Re: Ring Shank Design
Post by: RussellT on February 06, 2021, 05:28:55 AM
I have also seen (somewhere on youtube) an arrangement where a hook slides along the handle so it overlaps the edge of the crucible.

I should be possible to make such an arrangement so that the hook could be moved by a brake lever type arrangement on the handle.  I think ease of use is crucial - as I think Andrew pointed out - because it's a busy moment.

Russell
Title: Re: Ring Shank Design
Post by: vtsteam on February 06, 2021, 09:40:37 AM
If you cut a circle of cardboard and put it on the plinth under the crucible (before firing of course) the carbon from the burnt cardboard stops them sticking together.
That's the theory. It doesn't always work out in practice in my experience with iron. I've even used a double layer of cardboard and had them stick. Likewise Ironman does the same thing, but they do stick eventually. I've seen him pour with two plinths stuck on the end of a  single crucible. People question him about it, and he answers that it doesn't bother him. He uses purchased Vesuviana plinths, btw, designed for the purpose.