Hello, I'm new here and I hope I can get some advice. I haven't done much casting but I am trying to cast trim rings for the windows on a sailboat I am building. As you can see from the photo it didn't fill in all the way around. Should I place the sprue in the middle and gate it out to the sides? The part is about5" x 11" and about 1/4" thick. I am pouring silicon bronze and it was 1950° F. Thanks in advance Todd
Yes, having a second feeder so the casting looks like a figure '8' will halve the distance needed for the bronze to travel, that alone would probably fix it. Without modification, something that thin you'd need to dump it down a much larger feeder hole, preferably with a pouring cup big enough to make for an easy target to hit. Having the bronze hot enough to boil would help too as well as a few small gas vent holes.
It froze before it filled. Sprue in the middle and much fatter than 1/2 an inch from the looks of it. Taller feeder and bigger cup will help give it head pressure to push the bronze around. Pretty much what mark said. Welcome aboard. Let's see a photo of this sailboat! We live for photos around here.
OMG did we forget everything we learnt From John Cambell about gating system design 1) please do not Dump your metal 2.) Please do Not boil your metal 3.) Please do Not increase the size of your sprue as a first effort, 1/2 inch is the Largest Sprue a Hobbiest should need to use. in 99% of your work(Measured at the smallest location normally against the Casting) 4.) A larger Pouring basin is a good idea, it will allow you to pour the Metal faster ( the correct foundry term is Harder, as the speed the Metal fills the Mold is controlled by the Choke , normally at the Bottom of the sprue 5.) increase your pouring temp to 2150 https://atlasmetal.com/silicon-bronze-everdur.php a. if you insist on pouring directly into the casting increasing the height of the cope, or adding a pouring basin atop the mold will increase the Head Pressure and Help it feed better b. you need a single Vent directly opposite of the Sprue . remember if vents fill with metal they may not be working correctly if they are not the VERY last thing to fill 6. ) the Figure 8 idea is not terrible, though it might distort the casting (contraction of the crossbarr might pull in the opposite sides ) a. I would try tilting the Mold 15 Degrees so the side opposite to the Sprue is down hill. I would try 4, 5, and 6a all together . if you can angle the sprue correctly it helps with 6a, you do not want to pour down an angling sprue if it can be avoided V/r HT1 P.S. sorry I know I stepped on toes, but terminology is important don't stir metal, dumping metal means it went into the trash, and the only time Boil can be used is with Brass, to describe the Zinc Flare ( technically the zinc in the Brass is Boiling, not the entire heat )
You are right... I should have said 1/4". Pictures being what they are, it can be very hard to get the full picture without something added for scale. His window frame could be just 4" across or 24". Hard to tell. I would be careful with heading to the max pouring temp. Again, we dont know how thick this thing is. I do my best pours when I get sil bronze a little hotter than what's needed to move the metal where it needs to go and no more. It's good to get the ol toes stubbed, keeps us learning.
I would defer to HT1's assessment as he has more experience that I do . When I say boiling, I'm assuming the the original poster is using a small, fast cooling crucible and needs all the heat he can get for better flow. I automatically think of pouring bronze in terms of the moulds I use, i.e. resin sand which is more forgiving than green sand casting. Also you'd find that LG2 leaded gunmetal / C836 bronze / SAE40 is a good alloy to be casting marine hardware from as it has good corrosion resistance to seawater: http://www.conexbronze.com/catalogue/product/convert.php?id=Bronze UNS C83600 C 836 SAE 40 casting Alloy
Thanks for the advice. I tried two more times and it got closer but still didn't fill all the way around. I did the figure eight idea. I hadn't seen the later posts yet but I'll try HT1's advice. On the last try I think it might have made it but I hesitated after I started pouring and it went dry for a heartbeat. As far as the boat here are a couple of pictures. It is hard to get a good shot as my shop isn't very big It is an 18 foot day sailer. The one with the house sides shows the patterns for the window trim in place.
Holy cow, it reminds me of my 16ft day sailer! Except yours is built with some fine craftsmanship and the old turd I own was built by shitty AMF back in the 70's..... (back in the crappy harley days) You can nail these port holes. Just don't run them quite so thin. I would think almost 1/2" wouldn't be asking too much and will probably make it easier seeing you are sand casting these. If they HAD to be 1/4" it would be faster NOT to cast them. Get a small sheet of 1/4" from farmers copper in San Antonio and tig weld them up. The curved piece at the top can be formed in a harbor freight bender. Bending bronze on the "hard" and can be done cold. Your bend isn't that tight. Going out on a limb here......(again) Why aren't these actually about 1/2" thick with a cutout on the back to hold the plexiglass? You'll need a small amount of draft I'm sure.
Jason, thanks for the compliment. The casting is on hold right now because I found a crack in the little crucible I was using. As far as why I was making them only 1/4" thick it actually historic. This boat is a modern version of a different 18 footer I built in the 1970's. That boat was a traditional wooden boat that really needed to stay in the water all the time. Over the years, a marriage and a couple of kids later that boat ended up sitting in my yard. Finally I gave it away but the fellow who I gave it to never came and picked up the mast and boom. Those sat under our house for many years until I dreamed this project up. This new boat is inspired because I wanted to use the beautiful spruce mast and boom. It will look similar above the water line to the old one but will be more modern construction that doesn't need so much maintenance and can stay on a trailer. So going back to the windows, I didn't keep the old window frames but I did find the patterns I used when I built the original. I had a friend who was a bronze sculptor and I think he cast them for me. They capture the glass with a rabbet cut into the house sides rather than in the frames themselves. Here is a couple of pictures of the old boat on launch day. It was a little piano. Todd
traditionally for Marine work, a Yellow Brass would be most appropriate, leaded Gun metal is for fittings that will be under pressure (valves). Back when I was in the Navy Foundry because of storage issues, we used Manganses Bronze for all "brass" castings, and Gun Metal for darn Near everything else. but we had all the alloying metals so we could make any alloy we needed V/r HT1
Almost everything bronze we make is cast from LG2 gunmetal / red brass, I guess it simplifies stocking/purchasing. I've seen it used for seawater heat exchanger parts, maritime survey markers, a lathe spindle bush, prop shaft face seal mounts, sea cocks.
limiting your alloys in a production environment is cost saving, you need a crucible for every alloy, degassers, lord you have to keep the unmarked scrap separate ( huge storage issue), and has to be tracked all through clean up V/r HT1
You own a foundry...... Then WE expect to get something outta YOU! Welcome aboard. Let's see some photos! We live for them around here.
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