Gagger Matrix

I have been casting a 48" camelback pattern that has "islands" of sand hanging down in the drag as the drag is dropped onto the cope. (The cope has the same islands but remains supine until the mold is reassembled and those islands are therefore supported.) About 30 to 40% of the time the islands drop out as I invert the drag for assembly. This is the very last step in a 90 min molding session and follows an hour of work getting the flasks cleaned out, mulling sand, setting up the molds and applying graphite and talc. So, to say the least, it is distressing to see an otherwise "perfect' mold destroyed moments from completion. I think it might be possible for me to use more meticulous techniques and avoid at least half of these failures, but I am already being about as careful as I can be given my limitations of concentration and coordination.

So, after trying to avoid adding yet another step to the process, I knuckled under and made a gagger "matrix" that supports the sand in the central 4 islands. This was the simplest design I could think of that would allow easy positioning of the 4 gaggers and also allow them to, as a group, work together to support the sand. See pics below:



The rods are 1/4 steel round bar and the pads are 1/8" steel bar. My guess is that the two crossbars add a lot to the suspension strength of the matrix as they continue out to near the edges of the flask where the sand is very solidly supported. It just might be that they are not needed, and the central spine bar would be enough in itself. When fully rammed up, the crossbars are buried about 1/2" below the surface of the flask.

This arrangement makes a very strong support system that is not too much in the way of ramming the sand. With them in place the cope sand will not drop out even with pretty solid thumping on the sides of the inverted flask.

I use a similar setup on another pattern that has islands much like the islands in this pattern. Those gagger pads are actually screwed onto the ends of 2X4 stubs whose length matches sand depth. The 2x4 stubs are then secured to plywood crossmembers that span the flask. I think I like the matrix better as there is not a step requiring driving the screws though the 2X4 stubs are out of the way of ramming completely. I suspect much smaller and simpler gaggers would suffice in both cases. But I decided to overkill rather than have to revisit the gagger construction later.

FWIW,

Denis

 

Nice work Denis.

 

That's a good solution: Cheap, simple, easy to use and reliably fixes the issue. I'm a big fan of their use so far.

 

I'd be interested to see how you are using gaggers. There is not a lot written about their use or design. So, seeing how others use them I find interesting.

Denis

 

I'm just using what Henry HT1 called a "crossbar" (which to me, is a type of telephone exchange I once worked on):

 

The image is not visible on my computer. I see a symbol indicating an attempt to post an image.

Denis

 

It seems to be ok at this end, it's a link to the image used in post four of this thread: https://forums.thehomefoundry.org/index.php?threads/added-runners-to-my-green-sand-patterns.2643/

I'll trim the slash symbol on the end of the link and see if that helps:

 

One related use I'd heard of was to use a steel latticework welded to the flask to reinforce the sand and allow a much thinner flask to be used for large area castings. In the example I heard it was for square aluminium hatches for ship's decks so a fairly flat casting with a large surface area. The assembled mould used a fraction of the green sand it otherwise would need to handle the metal pressure and handling during ramming and assembly.

 

Yes, I have seen vids of 3rd-world foundries commonly using a coarsely "woven" grid in making things like manhole covers. Very thin copes were used making economical use of green sand and resulting in flasks that could be lifted by two men rather than lifting equipment.

Denis

 

Which makes me think even more that my "solution" is gross overkill. Most likely simple soldiers would work. I'll confess to running short on patience with dropout, though, and deciding, at least this time, to go with the "nuclear" option. But next time I might try soldiers. One variation on them might be to make the soldiers more than rough---actually put transverse shallow grooves (table saw kerfs) in them and/or make them have a top and bottom foot hoping such modifications would improve their holding power. Since the sand held on its own 2/3 of the time, it probably needs only a little help to make that 100%.

Denis

 

Denis you could use concrete reinforcing steel with it's rolled in texture too:

 

True enough as the texture would be a plus. But it is quite dense and by itself would add potentially significant weight to the already stressed sand. For that reason, I think I would favor wooden soldiers.

Denis

 

I have used the bars off concrete reinforcing mesh; they are only about 4mm in diameter and quite light.