Melterskelter-Thanks for the reply and advise, I did consider casting it as a solid, but personally do not have the facility or tooling to bore it with precision and I have successfully made a few cores, believe it or not that was the easy part. DavidF- Thanks for the compliment, took a while to put it together, old Harley bike parts not easy to find in the U.K. Martin
My first castings were in SS sand. Wax that pattern. 3 -4 nice coats then a kiss of parting powder (talc works). You should be golden. I did more like 10-15% SS on my first part (OVER KILL!!) and things pulled fine after gassing. Mold was rock hard... Darn near impossible to get the casting out of it after.
Hi crazybillybob. Thanks for the reply, I used 5 % by weight which seemed enough as my mould was rock hard as well. Yes going to wax the life out of the pattern before I attempt anything else. Will ram up both types of mould and see which is best. Will keep everyone posted. Martin.
BTW, I have used both gas and propanyl carbonate as a kicker for the sodium silicate. I have pretty well concluded that the propanyl carbonate ensures a more uniform and complete setting of the sodium silicate than does gassing, at least in my hands. This is not noticeable on simple core or molds like a simple cylinder or box. But on more detailed and deepish cores/molds I have found it hard to consistently get the gas down into the depths without over gassing. Mixing in 10% by weight of prop carb/sodium silicate I get complete and uniform setting of the sand. My routine is to mix my sand and, for iron pours, coal and then mix in a separate container my sodium silicate weakened with sugar for iron pours and prop carb. Then I add the sodium silicate and propanyl carbonate mix to the sand and use my drill and a paint stirrer to thoroughly mix in the liquids. I fill and pack the core box or flask and set it aside for about 3 hours (probably could get away with less) at 68 to 70 degrees. By then it has set up firmly. I get excellent rendition of crisp letters and numbers this way. With gas, I was having trouble occasionally losing the centrall portion of an "O", Zero, "R" or similar details. FWIW, Denis
Hi Melterskelter-I don’t think I will ever achieve your experience, I’m too long in the tooth already haha. I’m going to modify the pattern. Going to give it more draft and different font with less places for the sand to stick and some different paint. Determined not to let it beat me. Martin
Martin, there is no secret to this process. It is actually very simple. For non-iron use there are four ingredients: 1) Sodium Silicate RU (I see reports of using other forms of sodium silicate but that has the potential cause variation) 2) 100 mesh sand (certainly more and less fine sand can be used). Dilute the RU by 15% by weight with water and use 5% by weight RU in sand 3)Tap Water (I suppose incredibly mineral-rich well water could alter results some, so just to be removing a potential variable, deionized water could be used) 4)Propylene carbonate marketed by Clay Planet as Chem bond-210. I add 1 part Chem bond to 10 parts by weight (ratio not super critical) of sodium silicate. The prop carb allows stripping in about 2 to 3 hours at 68 F. For iron, I add sugar to weaken the bond which otherwise becomes too great with iron pours and I add coal to improve iron finish. There are variations on the above that also work. However, for me, that system works absolutely reliably first time every time. Yesterday, as an example, I made 3 cores of 3.5 pounds each. They drew perfectly—-not because of some great skill etc. It simply works simply. Here are a couple pics of one of the cores. The core is pretty hard—-not easily dented with a fingernail. Denis
Hi Denis. They are some pretty nice cores, the detail in them is incredible. Seems there is a lot more to this casting lark than I first thought. It’s nice to know people with your experience are willing to share it with newbies like me. There is certainly a massive amount of information in the archives of this site. A credit to all the contributing members. Thanks Martin
Martin, In late 2017 I was the rankest of newbies. This forum and the now defunct AA coddled me and schooled me to help me figure it out. Without this forum and the knowledge shared, I am sure I would have given up long ago. Still working on figuring it out... Denis
Denis, I have googled "Propanyl" carbonate and can't find it spelt that way. Is the spelling correct, as I want to buy some? Cheers Charlie
Why not use a steel pin for the core? It looks like you want that large diameter in the center to save weight. Why bother on a Harley? Just make a polished steel pin, give it a good coat of lamp black and pour. You should be able to drive the pin out after it cools. I have done this a number of times on different castings. Regards, Ray
Hi Raymond, thanks for the reply. Making the core was not the problem, out of all this the core was the only thing that went without a hitch. I am at present ( between other things ) remaking the pattern and using a different paint as the sodium silicate/sand mix was bonding to the pattern. Other experienced casters thought it may have been the paint not quite hard enough before I rammed it all up. Will report back when I try again. Martin
Martin, I too live in the UK (Cornwall) and am having a hard time finding propylene carbonate. Did you ever find any? Very nice looking bike by the way! I am an Austin Seven owner myself, I had to give up bikes because I was getting a bit silly. Northampton to Hemel Hempsted, 55 miles, 55 minutes, Honda 250 K4, late December. I loved it!
Melterskelter, Just want to say thanks for the Chem-bond 210, just what I was looking for.. Ordering some today..
As you no doubt would expect, the reaction Chem-bond catalyzes is significantly affected by sand temperature. If the sand temp is 85 or higher, I think it starts to go off noticeably in 10 or 15 mins. So not a lot of working time. And if my sand is much less than 70F, I heat some sand and mix it with cold sand to get 75 to 80 deg sand Depending on how hard you need the core to be, stripping in 1-2 hours will probably work. On big cores that need to be strong I like 3-4 hours though less time might well be ok. Denis
I'll be picking this up and continuing with my idea of making lost wax shell molds in this thread. Ceramic Shell with a twist.. | The Home Foundry .. I believe the Chem-bond 210 will make it possible to build a hardened lost wax shell mold in a day.. Keep in mind I'm only aiming for low temp aluminum castings of about a pound.. It'll be like a fiberglass layup, but with sio2 and fiber blanket, over twice dipped dry wall mud.. 10-15min would be plenty time for layup..
Melterskelter , Finally got my chem bond 210.. Do you still gas when using cb210, or does it gel better without co2.. Also does the SIO2 harden to a solid mass when left as a liquid.. That's what interests me most. Will try to make my first mold today.. Two coats using 30 minute mud, I hope to finish a mold in one day.. . wml
If you add the catalyst Chem Bond, the silicate will harden in two or three hours at 72°F and it will be fully hard within 12 to 24 hours. As far as just allowing it to gel if left out in the air it is true that it will eventually gel I think most of that is because of evaporation of the water in the silicate. If you look up Brunhilda‘s bra thread, I think you will see where I used SS a couple of years ago as a plain time liquid on ceramic wool to rigidize that wool and that worked pretty well. I think in that case I cooked the painted-on material to get it to solidify. I generally do not use CO2 when using the Chem Bond but there’s no reason one cannot. Warming the catalyzed SS accelerates the curing reaction rate. Denis
