Technical Reinventing the wheel

If you go to the Backyard Metalcasters forum you can find out what to use to "re moisten" the petrobond. I read one post that said a little 2 stroke oil will take out the crispiness.

 

Oh my God!
Lead will make you dead.
It's great we didn't know.
Gosh, remember playing with liquid mercury from broken thermometers?

 

Correct. That's what i used to keep the Petrobond workable.
We even had aluminum flasks and a pyrometer.

 

Made a lot of shiny silver pennies as a kid.

 

Thanks for the information, that is what I needed to know.

 

'51;
I see you got some answers. The stuff we used in school, got used fairly heavily, for probably a year. I don't remember having to oil it, although the teacher may have. It was sorta dry when I used it, would lightly clump if a small handfull were squeezed tightly, but it wouldn't clog the screen(s) when rubbed through it, although it would stain your hands a bit. Which came off easily when washed w/soap or the waterless handcleaner. We had a fair amount of sand, the cope n drags were maybe 16-18" long, 10-12' wide n 4-6" high. Had to use a lot of sand, & we'd get 2-6 rammed up prior to a pour. Always 2 guys to a pour because of the pot & holder design(s), although sometimes there were others around, they were made very well aware to stay the hell out of our way, due to the potential problems w/a ~1/2 gal of 1400* aluminum. Great way to kill an afternoon. I miss it.
Marcus...

 

My High school shop Instructor caught a fellow class-mate casting up some brass knucks..warmed his ass with the paddle...and yes.I went to schooll when
spanking was allowed

 

Thank you for the reply. After my experience with the somewhat smaller cope and drag I can see where the one that you were working with must have weighed a ton! You are correct that handling a pot full of molten aluminum is something that must be done carefully. That is why when I poured the air cleaner parts I did several "dry" runs with everything cold first. It was interesting how many problems I missed when just thinking about it and looking it over.

 

Sand castles

The goal of making patterns is to be able to make sand molds. Several years ago I bought an entire casting set up from an estate sale. I did have a difficult time getting information about the gear from the previous user. Since I had never been near any kind of foundry work some of the stuff was (and is) a total mystery.

The first thing that I found was that the boxes (casting flasks) were all the wrong size; either too big or too small (said Goldilocks).

This forced me back to the wood shop.

The box that I made looked to be the correct size and I made it as accurately as I could. This is pretty unusual for me. I used the wrong size boxes as examples of how things should fit and it seemed to work out OK.



At least they worked with only a few minor problems. One is that after getting them full of packed sand they are enormously heavy. I had to recruit the grown up sons to move them.

Another problem is that being made of wood they ignite pretty well when molten aluminum is spilled on them, who knew?



My exercise program for the next week or so consisted of pounding sand.

To begin I placed the pattern in the center of the top board in the drag. Note that the picture shows the top pattern, I don't have any pictures of the bottom pattern work. Since the procedure is mostly the same for both I won't differentiate between the pictures. Also note that at this point the top is on the bottom. I got confused by this several times during the project.



I liberally coated the pattern and the top board with talcum powder. I'm not sure if this was needed but it was the only part of the project that smelled nice.

I got several barrels of Petrobond casting sand from the estate sale. I don't have any experience with green sand but the Pertobond worked out well. I was careful to sift the sand before I used it although I'm not sure that was needed. Sometime later I found that Petrobond is kinda expensive and that I had gotten a really good deal on it.

The drag was filled layer by layer with packed sand. The first layer needed to be carefully placed and rammed evenly to keep the pattern from moving around as the sand was added. I suppose that I could have screwed the pattern to the top board to hold it still but where is the fun in that? I was also careful to get the sand packed into and around the support rib inside the drag.



After getting it all rammed the excess sand is scraped off. The sand needs to be even enough that when the bottom board it screwed down it seats evenly.





Now the drag needs to be turned over. Rolling the drag I believe is the term.


Turning the drag over let me see that I had made an undercut in the pattern. This allowed the sand to encase part of the pattern and would make it impossible to remove the pattern without breaking up the sand. I used my fingernail to remove the offending sand. Naturally this resulted in additional casting flash that would need to be removed but that's tomorrow's worry, right?

Then the cope was installed and the sand packing process was repeated.



After the top board was installed the mold was opened.



On my first attempt I tried to use wooden dowels to make the gate and vents. This was difficult and didn't work very well. On later attempts I cut all of that stuff into the mold after it was rammed up.

With the mold open and the cope supported on concrete blocks I was able to cut the gate and vents. I used tubing of various sizes to make the holes. I found that after the tube was removed the sand needed to be carefully packed back in around the hole.



After removing the top board I cleaned up the top of the mold and used a spoon to cut in the pouring funnel. I also made funnels above the vents in case they got too full.



Then the pattern was removed from the drag and the sand cleaned up.


Since the cope and the drag are symmetrical they can be assembled backwards. Fortunately the boxes were accurate enough that this didn't create a problem in this instance. The fact that the inside of the bottom pattern is totally flat helped a lot too.

I did put match marks on the sides but who actually looks at those? I also had some confusion over which side was up and when since in the ramming process the parts get turned over.

The biggest lesson in making the mold was how labor intensive it is. There is considerable pounding and lifting involved.

After all of that it is time to close the mold and pour the part.



The actual casting will be covered in a later chapter.

I didn't attempt to cast all of the parts at once and so I was able to use what I learned screwing up the first part when I made the other patterns and molds.

As it turned out the latch bracket was small enough that I was able to use one of the flasks that came with the foundry stuff.

There aren't a lot of pictures to this point since it really isn't very interesting. That and I was tired from all that pounding. I started taking a lot more pictures during the actual casting since I was using the photos in order to figure out where I was going wrong. More on that later.

I learned a lot while doing this step. One is that I now know why most people avoid this sort of thing. I am also sure that there are better/easier ways to do this. Those of you that know the better/easier ways please don't hurt yourself laughing at the amateur.

Getting close to actually making a part, hooray!

 

Wow
Thanks for taking the time to document this and post pics

Bobby

 

You are welcome. I have enjoyed looking at other peoples projects and so figured I should contribute. I'm no casting expert but I'm hoping that the thread is at least an interesting read.

 

You're still doing well. It's actually better to post the "ooops...", as that is what you can learn the most from.
The schools' cope/drag/bottom plate were all loose. The c/d had smallish tabs on the ends, to assist in grabbing them. For yours, just add some small keystone type tabs that intersect each other, & offset them so the c/d cannot be assembled any other way. Will tell you which end is up, & they will stay together easier. We held them together w/our fingers n hands, while flipping them (carefully). Found out real quick-like if the sand got pounded correctly. . Ya, they were heavy, but I was in good shape - then. Same stupid oof that carried 2 '56 Olds heads on each shoulder to class from 4 1/2 (long city) blocks away. Shoulders hurt for a bit, but I don't remember doing that again. Did lift & carried the engine block w/o a hoist once also. Didn't get hurt, but didn't do that again, either... . For the pouring gates, we used some thin walled tubing, ~ 1 - 2" dia, & for the vents, just used some welding rod to poke gas holes. Next time, cut a larger "bathtub" around the gates opening. Also, if you cut the gates on the side edge (ends) of the pattern, make a well there too. It'll help w/the shrinkage & the larger inlet allows you to pour faster. We poured fairly fast to try n slow down the freezing, & once both the inlet n outlet gates were "full", I learned to slow the pour, but keep pouring into the inlet when it filled up. You can see it shrink while it's still molten, & adding the extra seemed to help, & then when it was *really* full, it'd get a little "muffin-top" at the pour point, so just quit pouring then. You could always heat the mold up somewhat to slow down the Al cooling, but ours were just hot from being in the casting area, & also near the melting pot, as we didn't like to carry the carbide pot any further than we had to, even though we used long tongs & handles. IIRC, we used a small handful of borax (when we ran out of real flux) to flux the Al after it had cooled to the correct desired pouring temp. Sounds like you got a killer deal of the century on your stuff. Just make sure to have & use, the proper protection equipment. Getting hurt w/molten metal(s) will happen so fast you won't realize it - but at least it'll be permanent. & not in a good way. Thanks for the memory jog. I like this thread.
Marcus...

 

I'm hoping that someone else will learn from my mistakes. 'Course I never listened to other people.
I'm planning on putting a couple of pegs on the cope and drag so that they can only be assembled one way, you know idiot proof. When I made them I figured incorrectly that a couple of sharpie lines were all that was needed, nope!
I did learn the value of heating the mold and pouring quickly, more on that in a future episode.
The sand molds are that wonderful combination of heavy and fragile and so handling them becomes a bit interesting.
I'm glad that you are enjoying the adventure.
Norm

 

ahh....so making casting molds is where that saying came from.
Always thought it was a euphemism for something else.

Great work and treatise, Norm! Lots to be learned by the community here.
I tried casting a shifter handle out of aluminum when I was a kid, using water-soaked wood.
Didn't work at all.

 

Very cool thread !

 

I'm thinking (dangerous I know) that the context has something to do with the definition.

Thank you Sir.

 

Very cool thread indeed! Looking forward to the next installment!

 

Aluminum cupcakes

Since I wasn't going to get far pouring without having a supply of aluminum I scouted out the junk pile and found a broken wheel from my truck. It was broken due to the railroad track incident (don't ask). I figured that if I melted it down I wouldn't have to explain how it got broken.

I also thought that it would be good experience in using the melting and pouring equipment before the actual project.

This is where I discovered that my melting pot was not big enough to contain the amount of aluminum required for the air cleaner.

So off to the weld shop. I hadn't stick welded for at least a couple of years and so had to learn all over again. It really isn't like riding a bicycle, it's a lot hotter.

A friend donated a 12” piece of schedule 80 4” steel pipe to the project, thanks Tom.

Note that if you don't get good penetration on a melting pot bottom seal weld it can result in an aluminum puddle in the bottom of the kiln, just saying.

The new pot holds about 12 pounds of aluminum, three times what the old one did. This is enough to cast any of the air cleaner pieces with some left over.


Now all I needed to do was get the wheel into bite sized pieces that would fit into the pot.

My plasma cutter was pretty good on the wheel hoop but the disc was too thick being nearly 2” near the lug stud holes.

I ended up using my wood cutting miter saw with a carbide tipped blade. It cut really well; I have actually had wood that was harder to cut. The down side is that it is incredibly noisy (wear ear protection!) and throws hot chips everywhere (wear eye protection!) Fishing hot chips out of my shirt was kinda fun.


At this point my wife donated an old cupcake pan so that I could cast ingots shaped like aluminum cup cakes.

The kiln that I am using is an old pottery kiln that was given to us some time ago. I made a new control system for it and doubled the control range in anticipation of someday using it to melt aluminum. The controls appear to be reasonably accurate in that the aluminum begins to be soft at an indicated 1,350F and was fully molten by 1,500F. The kiln is about a 12” X 12” X 12” inside so the new pot just fits.


Be advised that 1,500F is very hot! I opened the kiln once with out gloves or face shield and now need to regrow my back of the hand hair. The hot blast to the face was also educational. My son discovered that after the kiln had been turned off for a day it was just the right temperature for hand warming.






After several “dry runs” (cold runs?) I was ready to make cupcakes!

The first thing that I noted was that molten aluminum is very runny. The next thing I noted was smoldering plywood stinks. Naturally the wind direction ensured the smoke blew into the garage and stank it up. This was so much fun that I repeated the burning process several times during the project.


The cup cakes don't require anything to help them come out of the pan. As long as there isn't too much spillage on top they will fall out of the pan after they cool a bit. Be advised that just because they are cool enough to come out of the pan they are still plenty hot.

I was able to make a dozen cupcakes in the first batch and found that they weigh pretty close to half a pound each. Knowing the weight meant that I was able to make a somewhat informed decision about how much aluminum was in the pot.


After the first batch I enlarged and modified the pot pouring spout. I found that the long spout was not needed to control the pour. It also reduced the speed that the molten aluminum could come out of the pot resulting in the spout clogging.

One broken truck wheel makes about three dozen cupcakes.

 

This is a great post. So much very useful information and how the at home guy made his own stuff.

Not lucky enough to have this class in school in the 70’s, machine shop and automotive mostly and this is cool.

I’m thinking that I would do this outside, away from my house so as to not burn the joint down, I’m just saying.

Great write up and pictures, sharing is what it’s all about.

Thanks,
Cliff Ramsdell

 

Nice start on the safety equip.
Didn't see leggings. For those who don't know, pants go on the *outside* of the boots, leggings go on top of those. Since I don't post pics yet, leggings should be made out of leather if you can't find the good stuff, which, IIRC, was a metal tapered tube that snapped around the leg(spring-loaded, so you didn't have to tie them on) & went from the boot top to just above the knee. They only went on one way, as they snapped around the back of the leg, the knee portion was higher in front than in back, & they also had a flap that covered ~ 1/2 of the front n top of the boot while also draping over the side to ~ the ground level. These are very important, to the point that I'd make my own, or not pour. You ain't gonna get the boot/shoe off fast enough to stop damage from 1400* molten metal if it spills/pours/splashes into the boot/shoe/flipflop/etc. If you think welding spatter hurts... Oh, & pour over sand. IIRC, the school had a metal grate that was placed over sand, 'cause the floors were concrete. Everything was very stable. Spills didn't happen very often, but when I saw them, the molten Al just quickly froze over the steel grates n sand, didn't spatter like wicked frying eggs, & was easy to clean up since the Al didn't stick to any of it. When pouring :
Safety (yours) First!

Instead of a hole in the side of the pot, you could also cut a V in the flat top cover you have. Or make a lip w/a point (like a pouring "spout" on a pyrex pot or any measuring cup. Doesn't need to be long or big, just distort the round edge to a slight point w/sorta-flat sides going from the point to the round edge, to encourage controlled flow. Just use a torch to heat some of the edge & use a needle-nose pliers to bend/form the pour spout.). The fully open top of the crucible will make scraping the dross/gunk off that's floating on top of the melt. I don't remember what we used as a de-gunker to purify the Al, but, iirc, when we were out of the commercial stuff, we used a small handful of borax stirred into the melt. When I did lead bullet castings, I found a pinky-tip-sized squeeze of patch lube worked well. They all seem to smoke. Nothing that you want to breath in. Ventilation is your friend here. .

Cupcake tins work well, as you found out. We made ingot "pans" from angle iron welded together maybe ~ 6" long. Looked like VVVVV, w/the ends capped. Don't remember the weight, but they were uniform size. They stacked well for future melts. Small engine cases cut up work well, too. For some reason, pop cans didn't work well at all, at least for me.

HTH.
Marcus...

 

When I built my shop it was intentionally placed over 100 feet from the residence so that I am only likely to burn down one at a time. I am pouring over sand just outside of the shop door. I used an old sheet of plywood so that I would have a level and steady place to put the molds. The plywood had been used as a concrete form and had a bunch of release agent soaked in it. As a result it smoked a lot and naturally the wind blew the smoke through the open door into the shop.
I now have an exhaust fan for the shop.

I have the leggings but for some reason they didn't make it into the picture.

After hearing various horror stories about spilling molten metal I am willing to do what ever is necessary to prevent burning off something that won't grow back!

 

I’m not saying your place but it’s nice that it’s remote from the residence. It was just a safety statement overall.

Cliff Ramsdell

 

The leggings are called spats , the cover your shin and top of the boot, they come in leather , suede, and a tin foil looking thing

I’ve seen flux and salt used as a deox for smelting aluminum

Looking great !!! Love it

 

Norm
I envy your abilities. Did you think to make more than one of the air cleaners?
I'd sure like to have one. I'd also like to find the one you originally started with from
the Ebay, just to modify it myself.
Great work
Thanks for showing
Jim

 

I have the spats and an apron. I start putting them on from the bottom up to get the "shingle" effect. The last thing I need is to funnel a load of molten aluminum into my shoe.

I haven't healed up from the last one yet! I'm hoping that by showing how not to do it others will be encouraged to give it a try and do it right.

 

Good on you , that is the correct way to "dress-up". Put an inch or 2 of sand over the plywood. It'll help stabilize it, + the Al won't burn thru the sand n send up smoke signals.

2nd time you've mentioned "gotta heal up from last time". This sounds either serious, or a really good story. "Patiently waiting... ".

Oh, yes, did you fix the 1st air cleaner you did, w/the mill, or make another one? I'd bet that using the 1st one as a pattern to ram up, if unaltered (fixed), will result in exactly the size you wanted in the 1st place.

Marcus...

 

Nice write up! Get to learn something and have some good chuckles along the way!

Sent from my SM-G900V using The H.A.M.B. mobile app

 

I actually had to cast several before getting a usable one. Its a good thing that aluminum can be re melted or I would have run out of wheels.
As for healing up; I'm just sore from all of the pounding.

 

Fun thread! I took "metals" class in high school around 2000-01 and we learned how to weld (oxy/act, mig, stick) and pour aluminum molds. I think I still have the rooster that I cast from an old wind vane.

 

I never had the option of taking any type of casting class in high school and so now I am learning how as part of my retirement entertainment.