I'm going to try out a new refractory recipe some time soon which is 1 part sand or grog, 1 part bentonite claty (kitty litter), and 1 part sawdust. Let me know how your refractory mix works out.
Here is "Abdul" smoking away. I built a small pellet fire in the bottom and no blast and let it burn away slowly to help it cure a bit . I took the lid off and set it upside down on the burner as it has holes in it so the burn continues. It has been going now about 1 1/2 hours. With the lid off and no blast there is a slight roaring sound. I thought it was a high flying jet but it never changed so I looked inside and we have an almost perfect swirl burn going. Outside shell measured between 70 and 86 F . All I had was this C thermometer but i was educated (yes even in the 50s at Altona Public School )to understand both. (28=82, - 11.5 =11.5 , 21 = 70, 0 =32, 100 = 212. After that I just fill in the holes with a good estimate. I dont know how great it will be but it cant get away so I am figuring I am ok even if it does crack.
So after getting good colour on all the clay I braved up and put in a 1/4 fill of charcoal. I gave it time to get going then hooked up the shop vac again. That is when I learned this lesson. Rule No 3 DO NOT HOOK A SHOP VAC UP TO A FOUNDRY FURNACE WHEN THE HOSE IS IN THE **** POSITION!!!!!. First I thought ? "Man that's a lot of smoke! Why would that be?" Then the hose started to melt. I knew right then what was wrong and pulled the hose out quickly plugging it in the blow position. The burnt hose waved in the wind but never burnt through. I stopped and fixed it . A couple of small holes in the bottom of the vac but otherwise still good. Dont laugh ! Your turn will come. Anyway. These things are dangerous. Aside from the fumes they give off sparks and are a lot harder to use than my propane burner and I am sure not much cheaper. Where it did shine though is I was able to throw old pistons right in the coals and when i emptied it later pick out the melted chunks. I am going to take it the rest of the way to a cupola style operation with a dross hole and drain hole and a trap door set up. You do not want this thing anywhere near your buildings. Don
My books arrived, started on the small foundry books, right now I'm half way through volume 2. Saving the piston book for last. So far, they are pretty good, I've learned stuff that wasn't in any of my other casting books.
i tried the charcoal burner again today. I put a variac on the shop vac and turned it down to where the fire was happy. I did get a melt but when i poured it my crucible was so long and deep some of it solidified on the pour. I thought maybe i need more fire. That was not good. had to put it out. After a long hard think I decided that this is a dangerous device and of questionale success. My home brew propane burner set up works perfectly and this Refractory pot deal seems dangerous and if it wasnt well insulated I doubt it would melt anything. So I took it all apart . I destroyed it and put it in the back of the truck for the next s**** run. Don
I worked on the bottom plate for a bit today.(core locating tabs)Nothing magor but bit by bit the mold will get improved.
Well it wont be tomorrow. I still dont have a crank and I am retired . I have no schedule. I just work on what interests me at the moment. I did however spend some time grinding in the reworked mold this afternoon. Probably about 1/2 done reworking it. I did some other casting this week too. Some hubcaps for my other FED and a couple of batches of aluninum muffins.(but general use muffins. Not piston alloy) Don
I worked most of the morning on the mold. Ist pic. I whipped up some core sand and baked one. Must have had the mix wong or it is too dense as it bubbled on the pour. I finished it anyway because I wanted to see how the mold is working. The other pics show improvement. New piston from rewoked mold is on the bottom. I have recovered a lot of the bad corner section of the skirt. The whole thing is slightly larger. Seam is much neater. Funny finish is grinding marks. The two jagged deals are shadows by the way not cracks. I can see where I can improve it more so i will putter away tll i am happy then try again. I also need to solve my core sand deal. I think it does not breathe well enough sometimes. I probably have it too wet when I bake it so but is too dense. Also different sand (co****r and cleaner) might work better. Don
I worked on the mold a bit tday and baked another sand core before bed. i remixed the core sand so it was just barley sticky and packed it not as tight either. The bare minmum of everything. i will try another pour in the morning. Don
Using the core which was almost crumbly but breathed well I poured this one today. I machined the skirt at the just above the actual bore size. Everything is good except this small spot in the mold. I will go in with the dremel and fix it before the next pour. It might clean when I finalsize it but if it does I will be awful fortunate. Anyway I shall rework that section. If I have one constant problem casting it is that I for some reason try to make everything too close in the cast section. I must over come this but I dont feel like making a whole new mold when I am so close. Don
You are so right. Today after lunch I decided I wanted to try lost foam casting. My converted Turret lathe does not work well for boring holes. I decided that if I had a bridge between the front and back tool bit T slots which is about 9 inches with a cast boss in the centre I could use an end mill in the chuck to bore a hole in this casting into which I can put a boring bar or tool then run the whole deal off my carriage. I went to Lowes and bought a 1/2 sheet of Dow stryo insulate hi density blue foam. I borrow my wife's glue gun and glued the base and boss together in the styro. I went down to my wood room and smoothed the stryo out where I had cut it on my belt sander nicely rounding the edges. I buried the styro pattern in some sand I had in my bucket. Not good sand but just sand thinking it probably wont work anyway but I gotta try. I made two spures from narrow junks of styro and put one at each end of the pattern just touching it. I packed the sand but not crazy as I had read the aluminum just displaces the styro. Seem to good to be true. I fired up my burner. It burns normal till it reaches temp and then goes into afterburner with a gerwhoomp!. Just the way it works . Accidental success. In a few minutes I had the pot completely full and melted. I used the boss part left exposed to pour into as I had read you should always feed the fat part of the mold. I did see smoke coming out the sprue holes but figured it would be a mess. After goofing around in the shop while it cooled I shook it out. It Is perfect! Actually looks commercially made. A bit of clean up and cut of the spures and the pour point and it is ready for drilling and machining where it sits on the cross-slide. I cant believe how well it worked. I could have used a bit more aluminum but my pot was as ful as it could be. Otherwise it is perfect. Maybe I need to make some stryo pistons. I will rework the mold as promised but I may try making some stryo ones too. I dont know if you can use spray foam or not but if so I can make a wooden pattern and fill it with spray then pop it out and bury it and pour. Makes one think of the endless possiblilties that lie ahead. The finish is sure a lot nicer with the lost foam method. BTW I did not use any piston alloy for this. This was a Chev TBI intake I sawed up and melted. I keep piston material and general material seperate. Don
The spray foam sticks like glue, you will need a release agent for your female mold...........dunno if that will contaminate the pour? Wish I could see the new pistons on my home monitor. It is ****ping out and images are all in blue and black scale!
Does anyone make a pourable foam? The pics i took of the lathe part were taken when it was getting dark. Camera had no flash. Don Here are some action shots of the melt. This outfit really works. I am surprised how well. I made a Gingery type deal and chucked it as it didnt hold a candle to this outfit. Less than 20 minutes for a full pot. Usually 10 to 15. Don
Pretty sure Smooth-On makes a pourable foam. Sculpture Supply Canada should have it. Not inexpensive though.
OK I already had found Sculpture Canada's website. The only think limiting me now is the amount I can melt. If I make something any bigger than this I think i wll just set it up and get a local foundry to pour it. I have doubled my melt capacity and could get a bit more with a 1 deeper pot perhaps but that is about it. I already have more than enough for one big piston. Almost enough for two. Thought about a hot wire. I have a wired up dimmer and some violin steel strings and somewhere in my Ham radio stuff there is a 12 volt transfomer. To think this all started with a couple of bearing adapters. This is more fun than "borrowin'" watermelons. Don
Don't even think about burning out porable foams. The burning g***es will kill you! The white polystirene is the best foam to use. The blue or pink insulation foam is the next best thing. All of your porable foams are polyurathanes and they are toxic when burned. If you make your core out of steel, with a little draw to it, it wil not stick to the piston as it cools. Jeffrey
If you make your core out of steel, with a little draw to it, it wil not stick to the piston as it cools NOt so. I made it with a 15 degree taper in all directions . Had to mill it out. It isnt that it sticks . it is that the aluinum shrinks and is so compressed you cant get it out. You could pull it while hot and the aluminum is not quite set which is what I think is happening in the egge video but that stresses the skirt I believe and if the piston was to fail later that would be the place. Baked sand worked much better and was very easy to do.
Heh, heh, thanks Don, for all the hard work, heh, heh, heh, then when I do this, it will go so much smoother, heh, heh; seriously I am very impressed with your talents and just being an all around nice guy!! I would like to shake your hand someday!! Mike.
Well I have been down your way a few times before so brace yourself , Someday?Thanks for the encouragement but really i am having a lot of fun. All the stuff i thought about i now am trying. Don
And you know, when its fun the time flies, no matter how hard or challenging it is!!! Happy Thanksgiving, do you celebrate that in Canada?
from what i see in the egge video is they have a three piece core, the center wedge is pulled down and the sides fall together, also i think it would make a big difference if it was polished.
Thanksgiving? Son we invented Turkeys. Ours is much earlier than yours. Usually first half of October somewhere. But Happy Thanksgiving to you all. In the egge video he is using what looks to be like a jack or hydraulic device to pull it. He is pumping something under the pour bench. I did polish mine to a mirror like finsh with the flap wheel. I had two bolt 7/16 welded to the core to pull it . One the threads gave out and on the other the weld broke. Vern was here for that and can verify it. The dang thing just would not come out .Anyway the sand core thing works. I only need 6 pistons and will probably never do any more after i have done this set. I am convinced my last race car is already in my shop. Some of you will know what i mean by that. Nothing is for ever. At best I might get in 3 more years. Don
Having played around last week with lost foam casting I decided to try making a foam piston and then use it to cast a real pistons from it. I took one of my better pistons and put it into some green sand. It took two tries to get the inside core to fall out. I was able to make a sand mold from the piston. I then used spray foam to fill the mold. I left it for a couple of hours till it was thoroughly hard. I removed it. it wasnt too bad. i washed the dirt off with warm water. I took the foam and fixed a couple of iffy spots and set it aside for afew more hours. I cleaned some up tonite. I will finish tomorow and then coat the foam piston in RTV silicon to make a flexible removeable mold from it. If I am lucky i can produce some identical foam pistons from it. The detail with lost foam amazes me. It was also much easier to pour . In fact I thought I had failed because it went too easy but when I removed the first part I made it was perfect and looked better than anything I had ever cast. Not though that I have abandoned the permanent mold either. I spent over an hour with it and small file today working the iffy places. I will probably spend another 4 hours or so on it. Don
Yes, lost foam really is impressive. When I was in engineering school, we cast mugs using the lost foam method. Our cores were compressed polystyrene balls (like those old school foam coolers and most foam cups are made from). When packed in good green sand and cast, they nearly perfectly replicated the texture of the pressed foam surface. It was quite remarkable the detail that was captured. When coated in ceramic slurry first, the little foam pebble texture was perfectly replicated, down to every last little detail. I was very impressed with the process. The best part IMO is that you can carve and affix the gates and runners right to the pattern, so you've got a solid positive representation of what the cast will look like before it's poured, so you can be sure of what you're getting. I think you'll find the method very useful in the future for one-off stuff. Just carve your positive and go (accounting for shrinkage, of course). Way cool.
I've been thinking about making an intake for my 390 cadillac with the lost foam method, it would be a whole lot easier than making the three baked sand cores needed for a dual plane intake. What kind of glue do you use to attach the gates and sprue?
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