Technical Reinventing the wheel

I love this thread. Entertaining as well as educational.

I make lots of things from cast aluminum, but I never do the pour. I make the patterns and send them out to a pro for pouring. But, I can't think how your initial pattern that was 102% of final target size didn't work? I've never had a part come back that wasn't smaller than the pattern. Shrinkage is about 1/4" per foot. I always use 102%. I am cheap and didn't buy a pattern maker's scale, I just made a Xerox at 102% of a regular scale and had that laminated.

 

I don't know how come it didn't work at 102% either. I have looked at it every way that I can think of and it still doesn't make sense. All I know for sure is that the actual casting came back at about 99.7% of the pattern. I am open to suggestions as to why.
Maybe I'm not good at math?
I made a drawing of the pattern with the finished dimensions. Then I multiplied those dimensions by 1.02 and those are the dimensions that I used to make the first pattern.
The latch bracket was small enough that the shrinkage didn't make any difference and as a result I didn't even measure the final casting. I don't know where that ended up shrinkage wise. The part fits good though.
I may steal your idea of copying a scale, I can see where that would make the process a lot easier.
Norm

 

This is a great thread, brings back a lot of my memories from the foundry days. 25+ yrs. in a cast iron foundry in way upstate N.Y. Learned every job but moulding, and have lots of scars to show for it (and that's with all the safety equipment). Looking forward to your pour, yes I did a Lot of that. We made small aluminum castings when I first started that were hand poured like you're doing. Gradually the Al work disappeared, but we still made small iron pours, usually with a wheeled ladle suspended on an overhead crane. Most of our work was for the paper making industry and we produced castings up 20 tons! Thanks, Carp.

 

You are welcome. I am enjoying hearing from the folks who have been there and done that.
Norm

 

Fun read @'51 Norm, I too was one of the lucky ones who had some foundry in high school shop. Only do a little lead casting from time to time now, but have wanted to step up to aluminum.
Just curious about your signature, I know what it means as my Dad often quoted the same thing. You didn't by chance pick that up serving in the "Canoe Club" did you? That's where he and I both heard and saw it used.

 

Aye, matey!

 

Outstanding! He was an airedale in the Korean conflict, I was a bubblehead toward the end of the party in SE Asia. Carry on!

 

Plank owner USS Virginia CGN-38
I managed to get a good conduct medal which we all know is an award for having four consecutive years of undetected crime.

 

I don't know about you, but the recent "thank you for your service" fad sure seems odd to someone called a "F****ng baby killer" when in uniform, but thanks for your service Norm!
You know there are only two types of warships at sea, submarines and submarine targets.....(-;

 

I'm glad that I am not the only one that noticed the change.
Sic Semper Tyrannis

 

Carry on Swabby.

 

Molten metal

I was finally ready to make the attempt.

Using what I had learned from making the cup cakes I put on all of the safety gear and did several “dry runs” to reduce the chance of spilling molten metal on something that would take a long time to heal.


After melting the aluminum I scraped off the floating junk and was ready to pour.

I had some difficulty with the pot on the first pour and that resulted in a couple of modifications before the second pour. The spout was removed and the pouring hole enlarged. Then I was able to fill the mold gate and funnel and things looked pretty good.


I had several interested tourists watching since it was the big day. No one wanted to wait around to see how it came out and so we all went to lunch. This turned out to be a good thing as it prevented the onlookers from seeing the first failure. Having extra people around made it so there are pictures of the process. I'm not coordinated enough to pour aluminum and take pictures at the same time.


While I was digging out the sand and getting it ready for the next attempt my wife noticed that I was using her garden trowel. I carefully explained that garden trowels look a lot alike and this was unlikely to be her trowel. Then she pointed out that it said “Becky” on the handle. To which I explained that I name all of my good tools.

I now have a trowel with no name on it.

After carefully examining the failed casting it looked like the mold collapsed near the gate. This prevented the molten aluminum from getting to the center of the casting.

So on the next attempt I put a couple of pieces of all thread across the cope near the gate to support the sand. I also made sure that the sand was well packed.


I cut up the first attempt so that I would have enough aluminum for the project. I really didn't want to find another rail road track to hit. That and the first casting was ugly enough that I didn't want it around.

On the second attempt I had fewer onlookers. Apparently they figured out that I wasn't going to set myself on fire so why bother?

The second attempt was an improvement but still not usable. Ditto for the third and the fourth.

After some additional forensic analysis of the failures I determined that the thin casting (1/4”) and large area (10” X 22”) was causing the metal to freeze before reaching the ends. The thin casting was the second major mistake.

I used several methods to overcome this. I modified the pattern with a rib down the center from end to end so that the hot metal would have an easier time reaching the ends. Then I increased the pouring temperature from 1,500F to near 1,600F and before trying to pour I used a MAPP gas torch to preheat the mold by shooting the flame down the hole for a couple of minutes.


The fifth try resulted in a usable casting. Notice I didn't say a good casting, it still had some flaws but I'm pretty sure that I can hide them.


I was really happy to finally get a casting since it was taking me about eight hours to make a mold, pour, etc.

This is where I decided that one air cleaner was enough.

Since I had a usable bottom plate I moved onto the top plate. That went a lot better since I knew at least some of the pitfalls and I was getting pretty good with pounding sand.

The only real issue that I had with the top casting was that the gate clogged at the end of the pour and so there wasn't enough molten metal available to prevent a shrinkage crater in the middle of the top. I was able to sand down the top to remove the low spot but it required a bunch of labor and sandpaper.


The latch bracket was a lot easier. Since it was smaller there wasn't so much sand pounding. The mold was also light enough that a normal person could move it.


At this point I began to wonder why all of my raw castings look like the star ship Enterprise.

Please note that I didn't make all of the possible mistakes; just a fair representation of them.

So with the casting done it was time to clean up the shop and get ready to make it all fit together.

 

Machine shop

Once I had a usable casting it was time to make sure that it fit the air filter element. It didn't.

On each of the failed castings I measured the length of the air filter locating rib and adjusted (ground the living snot out of) the pattern in an attempt to get the casting the right size. I believe that this is called the cut and try method. After four attempts the rib was still too long.

On the fifth try I was pretty disappointed to discover the casting rib was still longer than the inside of the air filter element.

Step one on the raw casting was to remove all of the gates, vents, etc. I used a hacksaw and brute force to remove them.


I used the bench disc sander to remove the casting flash and “tune up” the outer edge.

Then it was on to the milling machine.

I started with a fly cutter in order to get the bottom of the plate reasonably flat and straight. Note that there are no carburetor holes in the bottom plate. The plan was (and is) to make a “universal” bottom plate. That way it can be used no matter what odd combination of carburetors I come up with.


The fly cutting was pretty much a disaster. When I reduced the speed of the spindle to somewhere reasonable the motor liked to stall. Running the spindle faster resulted in the cutting tool loading up and then digging in. Add to that the fact that I somehow managed to fasten the casting down crooked resulted in some very ugly machining.

At this point I remembered that this was the very bottom and couldn't be seen anyway.

I broke out the belt sander and made it look kinda sorta like it was on purpose.

I wanted the bottom plate all in metal because I planned to have it powder coated. After I got to the powder coater I was informed that JB Weld had been successfully used in the past to fill parts before coating them. I didn't bother and surprisingly the coating filled most of the problem areas.

Turning the casting over I began the learning process of cutting an arc in G code. This ability was needed since I wasn't real excited about making the locating rib shorter with a file. So tradition be darned, fire up the CNC, what could possibly go wrong?

I learned the difference between G2 and G3, the hard way. Good thing the rib is buried inside the air cleaner and can't be seen without x-ray vision.

Then I got set up to cut out the holes for the carburetors. I semi carefully measured the carburetor air horns figuring to pick up a good (expensive) hole saw when we went to lunch.

Thinking about lunch enabled me to forget that there is a difference between inside and outside diameters. It turns out this is important when making holes for things that fit together, who knew?


So I carefully made 4 1/2” carburetor holes in my casting. Too bad that they should have been 4 1/8”. when I dropped the bottom plate onto the carburetors it fell halfway to the center of the earth.

After getting over my extreme pique I grabbed a piece of sewer pipe and made an adapter to take up the extra space. Poop.


Eventually I figured out that this whole (hole?) thing was good for a couple of reasons. First I couldn't find a 4 1/8” hole saw and I really didn't want to cut the holes with a boring head. Secondly having the adapter allowed me to set the air cleaner height anywhere I wanted above the carburetors. This is important since I don't know how much (if any) hood clearance I will have. The adapters also keep the bottom plate from resting on the top of the carburetors.

What happened above is the definition of serendipity.

The inner part of the adapter is made from a piece of PVC sewer pipe that I had laying around. The outer part is made from a 4” PVC coupling that I had to buy. The only difficulty I had was remembering which way to turn the “T” wrench on the lathe chuck since I was using the inside chuck jaws. I had to remove 3/8 “ from the inner diameter of the PVC pipe to get it to fit the carburetors.


The down side is that I can't use the adapters in a supercharged application since the sewer pipe is clearly labeled “not for pressure”.......


After completing the lower plate it was time to attack the upper plate.

In the center of the upper plate there was a low spot caused by shrinkage. I believe that it was due to the gate clogging up at the end of the pour and so there wasn't enough metal to compensate for the shrinkage. Regardless of the cause it needed to go away.


Using what I learned on the bottom plate I got out the belt sander and promptly made some discoveries. The sanding belts that I used came from the place everyone seems to love to hate, Harbor Freight Tools. The store that I frequent had two styles of sanding belts in 80 grit, expensive blue ones and cheap red ones. The blue ones work pretty well; the red ones like to shred right away. After the red ones shred some of the remains can be cut to fit a hand sanding block where they work really well.

Shredding the sanding belts wasn't a problem on the bottom plate since I did all of the sanding before cutting the holes. With nothing for the belts to catch on they didn't shred.

On the top there are all of those fancy looking fins for the belt to snag on.

Regardless, I was able to sand the top o' the top down even and make the low spot go away.

Naturally I also had to redo the filter locating rib like on the bottom plate. This went better since I had already learned the difference between G2 and G3.


Next chapter covers finish sanding, polishing and paint.

 

Norm,

I got to thinking that seeing as how you are a "sand caster" if someone were to tell you to "go pound sand" you could literally go do that. I suspect that would take some of the sting out of there hurtful intent.

I also thank you for the informative and humorous write-up. In tech school I had the opportunity to do some sand casting of aluminum. It was fun and learned a lot but it is definitely sonething you need to have a passion for. Unfortunately, I do not have that passion.

Keep up the good work! I look forward to your future installments to this thread.

 

In my youth, I worked at an investment casting shop, not in the casting area, but as a machineist cleaning up the rough castings. So I was exposed to a lot of the issues, such as shrinkage, etc. In general, the rule is, the thicker areas of a casting will have the most shrinkage. The pouring gate in your case was additional thickness and mass on the bottom side which caused a matching area of shrinkage on the top side. You placed the gate in a good spot to pour so the shrinkage was pretty much unavoidable there. In the casting business, the cure is to add a little bulge or crown raised up on the "flat side" of the pattern to compensate for the pull-down of the shrinkage. It's better to add a little more "bulge" than you need and only have to sand down a half dollar size area than it is to have to sand the entire top surface down to the lowest spot.

Ultimately, you made a good looking, good functioning set of somewhat flat pieces and you taught yourself how to do it. That's a win. I'm not an expert but I've picked up a few general ideas along the way. I'm going to stick my neck out past my education and way past my intelligence and say I think casting shrinkage is more pronounced regarding 3D thickness than it is regarding 2D length/width. As always, I'm subject to and welcome correction.

 

Thank you ,sir. I am hoping that my misadventures will help someone else.

You are "spot" on. I didn't expect the low place and so had to sand the entire area, a smaller raised piece would be much easier to deal with. The nice thing is that after sanding it down the top was ready for polishing!
As you pointed out the shrinkage in thickness seems to be more that the length/width. I don't know why that should be so but that is what happened.

 

Finish work

At this point most everything fit together and the assembled parts resembled an air cleaner. I wanted to make sure everything was right before the paint/polish/powder coat since I really didn't want to do that over.

I used the inner carburetor hold down bolts to install the bottom latch bracket. Naturally I needed longer hold down bolts since they were now doing double duty. Then I was surprised by the fact the carburetor hold down bolt spacing was not equal side to side.

I am using TransDapt carburetor adapters since when I started the project I didn't have any original Offenhauser adapters. I was told that the Offenhauser adaptors are no longer in production and that TransDapt had taken over manufacturing of the adapters.

After having the TransDapt adapters powder coated I accidentally came across a set of original Offenhauser adapters (I bought another manifold and they were installed on it). Long story short; the original adapters are way better than the later ones. I would use the original Offenhauser adapters but I am too far down the rabbit hole at this point.



I sanded the parts that were going to be polished until I got through the 1000 grit paper and then buffed them. I thought that they looked pretty good. I need to say that they are good to justify the effort in them.

Sanding and polishing can be a bit tedious but at least it is quiet enough to hear the rock and roll radio. I also enjoyed seeing the parts coming out of the mist and looking something like what I imagined when starting the project.



The parts that were to be powder coated I sanded with 220 grit. The areas between the ribs that were to be painted I cleaned with a file and 80 grit.

When I took the bottom plate and latch bracket to the powder coater I was informed that they could powder coat over JB weld. Meaning that I could have filled all of the remaining casting flaws in the bottom plate. I may try that next time, I was just wanting to be done at this point. If I leave the air cleaner installed the bottom is hidden anyway.

I was very happy with the result. Yes, the bottom plate isn't perfect but it is a lot better than I expected it to be. The reason for powder coating the bottom plate is to provide an accent line around the edge and I believe that I have succeeded with that.

Powder coating the latch bracket also provides contrast with the silver parts. To me there is such a thing as too much shiny. Of course my tolerance for shiny is a lot higher than most.

I painted inside the ribs with Rustoleum using a small brush. It took several coats to fill the streaks left from the brush strokes. I'm hoping that the paint lasts and that it doesn't need to be redone in the future. This is the same procedure that I used with the valve covers.

When planning the air cleaner top I used the valve covers as an example for the fin spacing and height since I wanted a coordinated look to the engine. You know, don't wear tennis shoes with a tux.



Next up is to put it all together and make the hidden hold down latch work.

 

Sounds like a lot of work, but the results look fantastic!

 

Thank you! It was a lot of work but I have found that the things that take the most effort are usually the most valued.

 

Exactly!

 

Looks great Norm! You had better sign it now for some future collector to proudly display on the shop wall.

 

A great guy on YouTube is Myfordboy in the UK. No talking, no music just demos and a lot of casting. https://www.youtube.com/user/myfordboy/videos

 

I am suppressed you did not use the lid you threw out for its scrap value, or did you?
Frank

 

I did cast my name and the year into the parts, when in grade school I was told that if I didn't put my name on my work I wouldn't get credit for it. I'm afraid that a lot of my work didn't deserve any credit!

I have watched several of his videos and I really enjoyed the traffic noises in the background. His work is first rate also.

The eBay special lid is taking up space in my shop. I suppose that I should put it up on my "trophy wall". All of the failed castings were broken up and re melted so I guess that they are all represented in the final part.

 

Enjoyed the ride, very educational. Thanks Frank

 

You are welcome. Next up is the hidden latch system, I think that you will get a kick out of that.

 

That's awesome and thank you for taking the time and sharing !

 

Latch assembly

One of the goals that I made was to have no visible hardware on the top of the air cleaner. This resulted in making a hidden latch assembly.

My first thought was to use an air hose coupler with one end attached to the air cleaner and the other part anchored between the carburetors.

Then I found these little gems:


They cost a lot more than the air hose coupler but are prettier.

Naturally the bottom of the latch assembly needed a place to anchor to.


The latch anchor is installed between the carburetors and attaches with the carburetor mounting bolts. I had to make longer carburetor mounting bolts to accommodate the latch anchor. When I made the latch anchor I was careful to make sure it cleared the idle adjusting screws and vacuum ports. This resulted in the sexy dog bone shape.


I also had to make an extension between the upper plate and the latch pin.


After getting it all together I decided to install a helper spring so that when the latch is released the air cleaner assembly lifts up. I am hoping that this will make removing the air cleaner a one handed operation.


The helper spring came from a storm door over travel chain. It is the correct diameter and only needed a little trimming to be the correct length. So far it seems to be close in the tension department. It was also cheap and available. The low cost helped to make up for what I paid for the push button catch.

The release button is on the bottom of the latch anchor bracket. So far it is easily accessible, I'm hoping that it remains so after the rest of the carburetor parts are installed.


The entire air cleaner assembly comes off as a unit. Removing the hitch pin allows the air cleaner and latch assembly to be dismantled.

It was a lot of work to make the hidden latch for the air cleaner and so I am required to say that it is an unqualified success.

All that is left to do is the final assembly and adjustment.

 

You are right Norm, that is "sexy".
They used to say anything worth doing is worth doing right. I guess you were listening. Nice work and great write up. A pleasure to read.

 

Final assembly and adjustment

Wanting the air cleaner to be reasonably easy to remove and install I glued the carburetor adapters in place with clear RTV. That way I didn't have to juggle several parts while installing the air cleaner. The RTV also provides a seal between the adapters and the bottom plate.


This was the same reasoning that I used with the clip on the latch spring. The whole air cleaner comes off in one piece. If any work needs to be done on the air cleaner (like cleaning or replacing the filter) it can be dismantled on the bench without tools.


I needed to trim a little off of the inside of the adapters to get them to install onto the carburetors without binding.

The pin on the bottom of latch assembly is adjustable for length. It took a little fussing to get it where it would easily “click” into the latch bracket without a lot of play in the air cleaner. After I was satisfied with the fit the lock nuts were tightened.

To adjust the spring tension all I had to do was turn the spring on the hitch pin so that there was more or less spring pressing on the latch bracket.


The amount of spring pressure still isn't as good as I would like; it requires a pretty good push on the button to release the air cleaner. There is a larger catch available and that might be better but at this point I'm not going to change it.

There is a felt gasket under the washer that is not shown because it wasn't made when the pictures were taken.

I figure that this is about the point where I will find some vital part that needs to occupy the same space as the latch.

Now that I have an air cleaner I guess that I need to finish building the engine that it goes on.