Metal Casting Zone

I use as an excuse, 'my magazine needs new content,' to stick my nose into Model Engineering topics I've always wanted to fully investigate.

I am planning a column in my magazine about casting and although I have numerous contributed articles about high-end lost wax work, nothing about the basics. Since I cannot expect my readers to start at the top, I am starting in at the bottom to learn the skills about which I can then write.

The stimulus that kicked off this venture was a local college Junior who is working on his ME and needed a summer intern project. Since he was familiar with 3D CAD, I enlisted him to pick up a long term project to make a 1/4-scale model of the first marine gas engine (1913) that was used in the San Francisco and Monterrey Bay fishing fleets, the Hicks. His assignment was to model the cylinder in 1/4-scale with allowance for shrink, extra metal for machining finished surfaces and to model the core boxes. With these files I am going out to a 3D printer and having the patterns and core boxes 'printed.'

In addition, a local Model Engineer with a bit of casting background in the distant past, agreed to let us use his foundry (very small, very old) in which to do the work. Parallel to the computer effort, he made wooden patterns and core boxes for the same cylinder and we poured with those so we'd have a comparison to the printed patterns and core boxes. A full-size Hicks is sitting on his patio so measurements were easy.

It had been 20 years since he had poured any metal so we had the normal series of 'issues.' First we rammed up one pattern and then remembered we hadn't used any parting dust. Pull the pattern and you guessed it, it comes out perfectly. So we dust the pattern (on a match board) and ram up both sides in the normal way. We pull the pattern and discover that we hadn't rammed the sand really tightly and it was a bit loose. Oh well, we decided to forge ahead.

Carefully measured out the water glass according to the weight of the core sand and mixed it well. Who called that stuff 'water?' More like molasses glass if you ask me. Anyway we stir and stir it until it must be well mixed. Lightly ram the sand into the core boxes and then put them in a plastic bag and fill that with CO2 which is Viagra for cores. Gets hard fast, doesn't it?

We gingerly (no pun intended) put the core into place and then turn on the furnace. It's a commercial furnace, about 30 years old and it takes 2 hours before it gets to temperature and melts the aluminum. Degass and skim the aluminum and pour. Now there's something that pours like water. Pretty too!

Clean up the space and finally knock the cylinder out of the sand. Looks pretty good, no voids that we can see. Start to chip out the core and suddenly realize that 4% Water Glass is much too hard. Go find vise, run a masonry drill through the center of the core to give us some chipping room. Spend 30 minutes chipping all the core out of the casting. Note to self, 2% next time!

This casting could be machined and made part of a nice model engine. Hummmmm. Beginner's luck. Its catching and I've gotta do it again Real Soon Now.

Time to make patterns for the head, base and other miscellaneous parts.

Took lots of pictures, many of which are NOT how to do something but sand casting is amazingly forgiving. I want more.

First casting picture attached, warts and all.

Mike Rehmus

Excellent job!!! I am currently working on a pattern for a steam engine cylinder and will also be casting cores for it. I will definetly be taking your advice on the 2% mix lol. So you dint blow the co2 thru the mold but rather bagged it and flooded it? was the core still in the core box? and did you need a release agent in the core box?

Welcome, and don't worry, you can quit any time you want. Not addicting at all...(Muahahaha! We got another one! )Pretty cool casting. It's kind of like golf, you hit one good shot and spend the rest of the round trying to figger out what the heck you did right the first time. Where are you sending to have the patterns printed? I've heard of that, but for most of us backyard schlubs it's probably prohibitively expensive.

You want to start at the bottom... so you came here? Hmmmm, oh well I resemble that remark.

If your going with CAD design, you may as well go with CNC machined matchplate. SOunds like a cool project and very good for first results.
OddDuck mentioned golf, I usually take the shot and spend the rest of the day looking for my ball, But I always came home with more than I took with me.
Same with casting, I take a shot and it lands in the bean feild, then I learn what I did wrong and go on.
What's the name of the magazine, and is it available online? We do like pictures.
Is this the engine?
Hicks Marine

That model of the Hicks is a 2-cylinder, the one we are modeling is the first Hicks, a single-cylinder.

The magazine is Model Engine Builder and is only available by subscription unless you live in Portland, OR and want to visit Powell's Technical Bookstore. It is not available on-line. www.modelenginebuilder.com is our Web site.

I am guessing that the next pour will not be so good. Although the one experienced foundry owner/user is a mechanical whiz and builds everything from experimental aircraft to model engines.

You can see some of what we do at www.baemclub.com and www.wemeshow.com Our next engine show is in Vallejo, CA the third weekend of July. These engines all run and get as complicated as 4-row radial and 24-cylinder Roll-Royce, multi-cylinder steam engines and very unusual Stirling engines (hot air).

There is, by the way, a dearth of good casting kits of unusual engines. Which is one other reason for talking up the hobby. And with the price of metal these days, casting is, I think, going to come back into its own. Engines cut from solid metal are quite expensive and, of course, are difficult to make with water passages, etc.

I have found a commercial 3D printing service in Ohio who are quite reasonable. Another, more reasonble printing service is the Community College in Hayward, CA where our club President teaches SolidWorks, a high-end 3D CAD program. They just received a nice new 3D printer and are willing to do the work for free (although schedules are sometimes a bit loose due to the nature of the school environment).

I wanted to try direct metal sintering but that looks to be out of sight price-wise right now.


Here is an image of the Hicks that is at the head of the Maritime Museum Pier in San Francisco. The guy is the owner of another Hicks (the one on the patio) from which we are taking measurements.

Forgot to answer the question about hardening the cores.

The attached picture shows it all but what we did was leave the lightly packed sand in the core boxes and insert them in a plastic bag, evacuated the air and then squirted in a shot of CO2 until the bag was inflated. What you cannot see is that I placed a pinch of the core sand inside the bag and tested that with finger pressure to tell when the cores were likely hardened. We then waited another 15 minutes before removing the cores from the boxes. They fell out with one light tap.

Finished cores.

We did not use core paste to glue the halves together since they are held quite well in the pattern.

The Hicks on display at the Hyde Street Pier in San Francisco

excellent work. casting is very addictive. welcome to the forum.

One thing is for certain, that is one heck of a job for a first try
the casting looks quite large for a model, what will be the finished bore size?
Im also assuming there will be a cast iron sleve installed?
that would be a neat engine to fit into my wherry.....