Improved Design for Welded Steel Flasks

I another thread some time ago I rported on making steel flasks from angle iron and flat bar. The arrangement was to use angle iron about 1X1X1/8 to make the walls of the flasks.

Here is a diagram with the green pieces representing angle iron

The concept was nice but no matter how you tack it up and stich it together, there is anherent tendency for warping to occur. Through some fiddling around with heat bending and peening I was able to nurse the sides into a pretty straight condition. But it took quite a bit of work---enough that I was not eager to weld up new flasks for different pattern.

But, it occured to me that a better arrangement migh involve square tubing and flat bar assembled so that all shrinking forces due to welding were balanced along the center axis of the flask wall.

Here is a diagram of the a section through balanced design flask

And here are pics of one of the weldments. This weldment is 34 inches in length and is 4 inchs high.
The bar is 1/8" thick and the 1" tubing is 16 ga.

This design works a whole lot better as it remains flat during welding and required no post weld straightening. Plus tacking it together is very fast.

I'll post some pics of the assembled finished flasks tomorrow. Pins need to be added as do studs used in closing the flasks. This is a Cope, Cheek, and Drag style flask.

Denis

 

Denis, how does the three-part flask work with your handling system? Does each section get hardware for that?

 

I use studs on the ends of the flask to bind the flask pieces together and to porvide a lug for lifting equipment. For smaller flasks I just use tabs on the ends to bolt together the sections and then I hand turn them. For this flask set which will weigh 300 pounds full of sand, I use a bracket witha boss for turning them. I'll post pics later. I use low-profile pins between the flask sections for registration.

Denis

 

I made some progress on the flasks today though dealing with a dandy case (on prednisone now) of poison ivy has slowed me down some. I think the prednisone is helping as it should and I hope to be back to full action in a few days.

As anticipated, the hollow 3/4 '16 ga square tubes do not have enough thickness to allow me to simply drill and tap them for 1/4-20 screws that I use to attach top and bottom boards to the flasks. So, a means of backing up the walls was needed. I decided to try making 1/4" by not quite 5/8 slugs of steel about 1.25" long placing the inside the tubes against the upper wall and welding them in place. That provided a "hard spot' that I could drill and tap that would have good holding power.

I fiddled around some with the following method which ended up being relatively easy to do and is very secure.

Here are the twelve flask components for cope, cheek, and drag. You can see that the long sides each have three tapped holes with two areas of welding flanking each hole and the short ends have a single drilled and tapped hole. That is because the method used was to first drill and tap each slug at its mid-point so that 24 slugs were made. Then 17/64th holes were drilled into the tubes at the desired locations. Esch of those holes was flanked 7/64th holes space .400 on either d\side of the main hole. I removed most of the burrs inside the tube by using a 1/8 x 5/8 steel bar (the "introducer") about 20 inches long and sharpened to a chisel end. Just jamming it down the tube after drilling removed the burr well enough.

Next I used that same bar with a short pin on end sticking up to slide a slug into position under the 1764 hole. Once in position I use a 1/2" long 1/4-20SHCS to draw the slug firmly up against the tube Then I tigged the slug to the tube via the flanking holes. Worked slick. The spacing on the flanking holes and their size allowed pretty easy tigging. I would also draw your attention to the fact that the flask components are lined up nice and straight with each other---no warping.

This is one of the flask ends with a 5/16" drilled and tapped hole for the bolt that sereves as a lifting lug and aids in strapping the cope to cheek to drag.

Chisel end of introducer
Here is the introducer with a slug near its pin end.

This is a closeup of the pin end

Introducer with slug on the pin and ready to slide into the square tube. Don't make the pin too long or you won't be able to disengage from the slug. Also, this is one time when cleaning the scale from the slug is important to get good tig results.


I hope this makes some sense. I would have made a video by my chief videographer (wife) was not home and running a camera while tigging is well beyond my capabilities. ;-)

Denis

 

More work than countersunk Nutserts - but they won't come loose.

 

That’s the thing. Nutserts are cool for one-time assembly and are quick to install. But these slugs are going to be subject to hard use and many cycles in a sandy environment over the years. So, taking the time to slice up 1/4” plate, drill and tap it, and prep the tubes took at least 4 times as much work, they should last a long time. And if one strips out, I’ll just use a countersink cutter to deeply dish it out and tig it shut and the redrill and tap.

Denis

 

Sorry about the poison ivy. One of mother natures cruel pranks. Nice result on the burrs and placement too.

Pete

 

If I had a nickel for every 1/2" Tinnerman insert I ever punched for and placed...I might have a cool 50$
I was thinking if there would be a way to do this all from the outside by adding thicker sections into the square tubing with the flat bar stock.
Starting right to left:
1. cut out tube and cut off bar stock
2. weld and grind bar flush to tube
3. measure spacing and drill and tap

Thanks for taking us along Denis.

 

Nice idea. I think it would work great. I did get pretty good at the holes and weld method and found it was quicker with MIG than TIG.

Denis

 

The flask set is complete! I did make just about every careless mistake available along the way. So, that added an hour or more in redo's. BUT, it is done. The flasks fit together very nicely. The are not warped or twisted and that is only because I set the pieces up as carefully as I could and tried to be as strategic as possible in placing successive tack welds to counter the inevitable distortion effects caused by shrinking welds. I must have measured diagonals at least 75 times to check for squareness. Diagonal clamps also came into play along with a big Crescent wrench and a hammer ot two.

I am really happy with the final fit up and figure these flasks will last indefinitely. They will rust inside after a few uses, but I have found that applying a phosphoric acid containing metal prep converts the rust to a very stable coating that strongly resists additional rusting and likely aids in sand retention as it is a rough surface.

In my prior posts I did not have a photo of the slug and drilled holes---I should have. Here is a slug on top and one is in place held firmly against the inside of the tube by a 1/4-20 SHCS. The cap screw head being small allows plenty of room for welding the slug to the tube via the holes.



You can see the end studs and strap used to clamp the pieces together.


The pieces register on each other with two short 5/16" pins both located along the same edge of the flask piece. I am lifting the sections using a hoist via the end pins so I can lower the cope onto the cheek, for instance, until it is within a 1/2" and then tilt the cope to engage the pins and then finish lowering. There are no protruding pattern parts that rise above the surface of the flask, so long pins are not needed.

I outlined the pins and their respective holes with yellow paint stick. The other smaller holes are for attacking bottom and top boards as needed and are where the slugs are located.


Denis

 

BTW, the cheek section is heaviest at 17 pounds and the other two are 15.5 and 14 easch I will need to weigh the wood ones they replace. I think it will be comparable.

Denis

 

Thanks for the additional pictures Denis, those look amazing.

 

Will be super interesting to see how they stack up, gravitationally...lol You are gaining all the rigidity!

 

You are very right about the rigidity. The wood ones are pretty good that way, but the steel ones are several times stiffer and will maintain their flatness and squareness better. The failing wood ones were starting to bulge and twist some as they are battered by heat and moisture, not to mention some combustion with each use. There were a couple of sizable knots in the wood ones which were contributing to distortion.

I did weigh a wood middle section and it was almost 14 pounds and the steel replacement was 17 pounds. That is not a significant difference once the center section is loaded with just a little less than 100 pounds of sand. I won't be able to pound up a mold today, but expect to and anticipate doing so tomorrow!

Denis

 

Not at all. Almost negligible. I have a large casting coming in the future and these flasks may be the ticket! if you don't mind me borrowing all your hard brainwork.

Would you try to go any thinner with the sheet metal or tubing to shave any weight are happy where they are?

Those center pivot pins will be really nice for flipping/handling the boxes when fully loaded.

 

By all means copy and improve them. I suspect 16 ga could be used for the webs. But flask weight is ok as is and slightly heavier material may be easier to weld and keep straight. Using sheared webs rather flat bar will be my next iteration—-to get exactly the heights needed rather than “close enough.” The tubes are 16 ga.

Post up your build when it comes time.

Denis

 

I poured a mold made in the flasks today. They worked just as hoped. Yay!

Denis

 

Which can not always be expected

 

I made another set of flasks of the same dimensions over the last few days. I welded componenets in a different and, as it turns out, better order. And I paid more attention to the fitting of the picture frame components.

I cut my square tube sets with a horizontal band saw again, but I cut them over length by a 16th or so on purpose. Then I took them to the mill and trimmed them very accurately to length and square. Theat made them fit up tightly and reduced the tendency of tack welds and finsih welds to deflect the frames. I aslo used a simple plywood fixture to hold the components securely in a good square configuration as I tsked them up and made final welds. The fixture was a square plug of 3/4" plywood (the square tubes are also 3/4) that just fit inside an assembled frame. I did cut badk the corners of the plug to allow easy and smoke-free welding. I only tacked and finish welded on the top and bottom surfaces of the butt joint as the inside corner welds particularly tend to spring the frame. Welding them up in this fashion resulted in very square frames that required little or no cold-setting. Once all six frames were welded, I had sheared 16ga webs as needed to hit my final sizes or I used off-the-shelf 1/8" bar to provide flask height. The webs were placed on the centeerline of the frame tuing to minimize weld-related deflection.

The resulting flasks were less than a 16th off on corner-to-corner diagonal measurements----vert very square and only one required cold setting to take out twist. It was twisted about 3/16.

The rest is just a mattter of placing registration pins and studs for stras to clamp flasks together.

This order of assembly was significantly easier than the previously used method of welding up panels indiviually and then assembling those components into flasks.

Pics of completed flasks later.

Denis