I have about four matchplate patterns I'm regularly using so I'm wasting time carving runners and then having to inevitably repair the broken sand. There were shrinkage and feed issues so it did take runner design changes and casting moulds upside down to get good results. With things debugged, I bit the bullet and added runners to my patterns and today did a set of castings with the modifications. Not having to hand carve runners is saving up to half an hour per mould and the finish on the castings does seem to be better as loose sand is minimized. I did have a pulley cover casting fail due to a large chunk of sand breaking off and falling 1/4" or 6mm as it normally hangs above the bottom half of the mould: I have to be extra careful flipping the flasks during ramming and subsequent pattern removal as the matchplate sticks out past the flasks and can be easily bumped when flipping the flasks which breaks off or damages the block of free hanging sand. With only two feeders on the left and middle, there was shrinkage on the flat area on the right until I added a third feeder on the far right: Lid mould now has the casting "right side up" which eliminates shrink in the center of the casting. I had used extra head height from a soup can runner so this orientation eliminated that and still gave a good casting. This is the pulley cover casting which had a big chunk of sand break free and had the aluminium fill the gap. There should be three 6mm flat surfaces.
you say feeder, do you mean Ingate/gate, feeder is a riser, or as the British say bob, though Bob arguably only means a closed riser (deep in the weed there I suspect that is a regional thing) I know if you saw my pattern thread(Sorry Guys I know i have not done enough there,) I put the gating system on almost every matchplate and even include it on follow boards, its a no brainer, saves time and adds consistency, I desperately try to never hang large chunks of sand (green sand cores) it often forces the dreaded double roll, but will definitely get you more satisfactory castings, if you are doing the double roll it is also helpful to make a custom sprue so you can ram it up with the cope, I probably need to show that technique all in all, BZ Well done V/r HT1
Thanks Henry, yes I always have trouble with the terms, I swear it's the same at the hardware store where the counter staff know five different names for the one item and use them in rotation. The ingates have made life easier but I'll have to see if I'm getting shrink on the casting close to the ingate, I'd been advised to "pinch" or narrow them where they flow into the casting to reduce this. I'm planning on adding a small amount of steel to the flask to reinforce the sand, maybe a single 3/8" rod than can be easily rammed around for this particular pattern and removable from the flask when not using it. It's cheating a bit but I'll be able to ram up the hanging core and only have to flip that flask to remove the matchplate. In hindsight that hanging piece has broken off three times out of five attempts but I was always able to catch it in time, this time the assembled mould sat around for six days while it rained. The new batch of green sand is ramming up great and the casting finish has never been better, I put a radius on the sharp corner where the runner hits the casting with my thumb
Tonight I added a steel bar reinforcing the green sand, it might be cheating but it'll save a lot of time in the long run even if it's a bit harder to ram. It's rotated horizontally to install in the flask and held by two 5mm screws through steel tabs that resist any twisting forces, it's quite stiff and takes a fair bit of force to deflect it. Note the quality stick welding...at least there's plenty of weld elsewhere.
that's not cheating, its a crossbar, sometimes called a chuck ( again probably a british thing like bob ) its actually recommended that it be made out of a twisted bar ( Rebar anyone?) just remember you need 3/4 to 1 inch of sand separating your support from the casting , looks pretty good to me though I'm having trouble judging size if that was a set of 20X20 Inch flasks, it would add some cross pieces to that support, but i think you are in 12X12 so your probably fine Good Luck V/r HT1 P.S in the future you can use wood for that and pepper it with foundry nails driven half way in so it looks like a morning star, sand will definitely stay stuck to that P.P.S https://babel.hathitrust.org/cgi/pt?id=uc1.b2862738&seq=154 extremely good read,
Good to know it's normal practice, the flask is about 16" x12" exposed area inside the steel frame with 10mm or 3/8" bar. Sand separation is about 1.5" from bar to the pattern. I'll keep it as simple as I can and still get it to ram up ok. I found a PDF copy of your book reference to download, the first seven pages are blank for some reason but it looks to be all there: https://ia803404.us.archive.org/11/items/us-navy-trade-manuals/Molder_3_2 b.pdf
Molder 3 & 2 along with the Molder 1 &C are the more modern versions on the Navy foundry Manual, they where revised about every 6 years, the final one was NAVEDTRA 12207 Patternmaker/Molder in 1993, it is the very worst of them all , what's sad is most of the Pictures date all the way back to the Foundry manual, alot of the More modern info is pretty much useless to the hobbiest, need instructions on operating an induction furnace???, how about details on advancement ?? though the Molder 1&c has a great section on basic heat treating if your interested V/r HT1
Here is the one I have bookmarked; it's set up to be web friendly. https://maritime.org/doc/foundry/index.php
I just poured a successful casting with the steel crossbar, it rammed up without any extra difficulty. I didn't handle it roughly but I was able to roll it over with confidence and it cast fine. There's a little bit of roughness and the odd bit of loose sand: my plastic air nozzle broke off at the air hose fitting when I went to use it, so I could only brush any loose sand out. The cast finish is not smooth but it's a nice texture, sort of like a fine particle board or those wheat biscuits .
