Well, I did get a little time in the shop today. I decided to make the web of the flask pattern 1/4" and the top and bottom rails are 11/16 wide. One could argue that the rails are too heavy. And they might be except I need to be able to drill and tap them for 1/4-20 bolts so I can attach top and bottom boards to the flasks for flipping. The pattern I will be casting in these flasks requires use of screwed-on boards. This will be a cope, cheek, drag arrangement. The cope and cheek will be 3.5 inches tall by 24 long and 10 wide. The drag will only be 2 inches tall as it has only a runner in it. There will be lugs on the end pieces to carry lifting/flipping 3/8" threaded studs. On the long pieces I plan to have a few vertical ribs for stiffening though these will be pretty light in section---something like 3/8" wide and 3/16" high. I will also include a logo---just for fun and some letters and a date in Roman Numerals. The inside face is to the right in these photos. There is a small sand-retaining key. I may also route a few shallow longitudinal grooves. Denis
BTW, sand and threaded holes in aluminum is often not a happy combination. I anticipate needing to put steel thread inserts like the Recoil system or Helicoils into those holes if they start to gum up with sand. Maybe needed, maybe not. Denis
Melter, since you will lift with your hoist I would not worry about weight and I think you are at the minimum thickness of the web because of the difference in the flow of Aluminum as compared to your experience with CI. The depth of your flask for cast iron is probably close to the minimum. Since we leave our castings in the mold, charred bottom boards are the result of the lack of sand between the casting and any combustibles. It is one of the main historical causes of foundry fires. If I am deep in the drag even with aluminum, I experience some charring.
I have used wooden flasks of this dimension perhaps 30 times to cast my 18" prism. The cheek dimension is the critical one and is dictated to be 3.5" based on the pattern size and need for it to terminate at the upper and lower boundaries of the cheek. So, I think I will get by at those dimensions. I do char my bottom board as you predicted. This is much worse if I drill holes in it for ventilation as the coal gas vents from each hole causing a small coal gas flame at each hole and then playing up onto the board. No more vents in the bottom board for me from now on. Seems backwards in a way but I've had both vented and unvented bottom boards and that is what seems clearly to be true. I will see if I can pour the 1/4" thick webs. If not, I'll add on to the pattern and go thicker. Though I do lift full molds with a hoist, I do lift flask stacks by hand and flip full individual and paired (but not 3-high) molds by hand. So, I'll try for the lighter weight realizing it might not work out. I should be able to pour pretty hot as porosity in flasks should not be a concern. I will do plenty of sand venting. I glued on end tabs tonight after supper. Obviously borrowing heavily from the printed patterns several seem to be working on. Provided I can cast it, I think this general dimension set will be stiff enough based on how it feels as a wood pattern---pretty stiff. Denis
I asked Julian to jump in here. He has put a lot of work into his design and might have some further suggestions. I know he appreciates feedback to improve his design. Mark
I used 1/4 20 helicoils to assemble My original flasks, I cannot imagine threading directly into aluminum, unless there is ALOT of thread length , which I did not have V/r HT1
Back on the USS Prairie when I works in the foundry there, we had steel bottom boards with a bullseye of holes drilled in them, for steam escape simply 1/4 inch plate with 1.5 inch angle strips for legs , saved on plywood, no firses from a little dripping metal , foundries using molding machines use cast aluminum bottom boards!!! Maybe I'll make some of those next ;-) V/r Ht1
Yes, I have used simple 20ga steel sheet with a few pieces of light angle tacked the short way every foot or so. Lotsa holes. Worked fine. Plywood is cheap and light and kinder to the hands. I pour outdoors and bring poured cooling molds into the barn. Smoldering doesn’t bother anything other than eventually wrecking the bottom boards. Denis
A bit more progress. The boss on the short piece in the center is where the loioifting and turning stud will go. The short bosses a couple inches from the ends will accommodate pins or holes for location. Pins located on the rail near me work well for my hoist setup. I either press that side down and locate into the holes and then finish lowering or, if lifting, hold the near side down until the flask has lifted about 1-2inches and then let it level out releasing the pin-hole engagement. The two "ribs" 7 inches from the ends may be unnecessary but seemed right. They should add stiffness to the long segments. Denis
I felt the 45degree joint that was simply end-grain glued to end-grain was a possible failure point when I ram up these patterns. So, I let in bridging feather-like wood inlays. That will strengthen the joint considerably. I think I'm about ready for some sanding and paint. I plan to use the emulsion (latex) paint recommended by, I think Ironsides, in hopes it will soften contours a bit and then finish with lacquer. Side view End view. Draft cut into the pattern causes the inlay to taper to near zero. Denis
Spent some time this evening sanding and filling spots on the patterns and mounting a raised lug for the hoist/flip lugs on the short side. I did trim the ears on the end tabs as they added nothing and potentially would be just in the way. Paint tomorrow. A 3/8" stud will go right in the center of the lug on the actual flask. Denis
OK, I am committed (or ought to be committed!) as I just bought 40+ pounds of 356 from Master Yoda. Should be enough to make quite a few flask pieces. I started 2.5" instead of 3.5" high drag pattern set this morning. It will be of the same general design. The second set seems easier as all the decisions have been made concerning angles, dimensions, stiffeners, and bosses. I should get my alloy from Spokane by Friday. Let the fun begin! BTW, Art (Master Yoda) was great to deal with. Denis
I'm looking into added some length to OFM model. I'm going to see if I can do it sorta like Jillians (or exactly like).
A bit more progress. Closing in on the drag pattern pcs. I want to cast 4-up. Now to the honey-doo list. Denis
I drew up a slight mod of Old Foundryman's Flask. It gives an internal size of about 12.25" per side with a depth of 3.25". I added a nice dovetail to hold the two halves together. I couldn't do Pins because it has to be printed vertically. I still have to Print a test yet.
Got the first test print off the printer. Found a minor issue with the ear length that makes it not work with OFM's offside piece. Fixed it so the next print should be a keeper. Either way here's a few pictures of the first print
I finally got the patterns done for the cope, cheek (same as cope), and drag. I hope to cast them in a couple days. This will be my maiden voyage into aluminum territory. I think I'll pour about 1260F or so. Probably will not go as planned, but have to start somewhere. I calculate it taking 21 pounds net to pour all four pieces so my A25 will be pretty full. I got my 356 ingots from Art (Master Yoda) yesterday---super quick shipping and nice clean looking ingots. Denis
Great looking patterns. I may have missed it in a earlier post but, what will your alignment hardware look like?
Thank you. They should be just good enough. Far from perfect. I will use very short 3/8” pins with domed ends placed in the cope and drag on the side pieces located where the rectangular bosses are set. Besides the dome, the pins will have only 1/8” straight sides showing. Since the patterns I will be casting in these flasks are flush with the surfaces of the cheek, no long straight pull is required. With a similar arrangement in wood flasks that these AL ones will replace, I just tilt the cope or drag as I lower it onto the cheek. The pins engage the holes and then I lower the cope or drag fully into place. One hole is round and the other slightly elongated to allow a little slop for easy and non-binding engagement. Denis
