Custom Scale Model Engine Builder

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This 1/3-scale 2-1/2 hp air-cooled Red Wing engine was David Stewart’s second model project. All of the engines he makes are designed to run on gasoline.
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Top view of David’s 1/3-scale 5 hp Galloway water-cooled hit-and-miss engine. With a larger piston and longer stroke, the Galloway produces a respectable sound when firing.
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David with his 1/3-scale 5 hp Galloway engine. David produces four or five engines a year. Work in recent years has been steady. “When the economy isn’t doing well, it slows down a little bit,” he says.
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David Stewart’s 1/3-scale 5 hp Galloway water-cooled hit-and-miss engine.
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This 1/4-scale 5 hp Red Wing water-cooled engine was David’s first project. He came out of the gates strong, and won a job building engines for the manufacturer.
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David’s current project, a 1/4-scale 5 hp Galloway engine.
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David’s current project, a 1/4-scale 5 hp Galloway engine.
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David’s current project, a 1/4-scale 5 hp Galloway engine.
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The engine cylinder casting set up in a 4-jaw chuck on David’s lathe for cylinder boring. The open space visible in the casting is the water jacket for cooling. Once the mating surface is machined the water hopper will be bolted to the cylinder. Two casting bosses are also visible on the side of the cylinder, one for the igniter and the other for the igniter and exhaust pushrod.

David Stewart was just looking for a project when he bought an antique drag saw with a 4 hp Wade gasoline engine. But he found more than that. The drag saw eventually led him to a post-retirement job building scale model engines.

After buying the antique drag saw, David decided to subscribe to Gas Engine Magazine to learn more about gas engines. “In November 2004, I read about Richard Allen Dickey building a 1/4-scale 2-1/2 hp water-cooled Red Wing engine,” he says. “I wanted a hit-and-miss engine, and I knew a scale model would be lighter than a full-size engine, so I ordered an air-cooled kit and made the engine.”

When the casting company changed hands, fate stepped in. “When I looked at the new company’s website, they were asking engine builders to display photos of their projects,” David says, “so I sent photos of the two engines I’d built. Later I got an email from the company’s owner, asking if I would be interested in building engines for him.”

After some discussion, David (who lives in Lamar, South Carolina) agreed to build one engine for hire. Since then, he has finished 53 engines (including three for himself) and is working on engine number 54. 

Starting with Red Wing

David’s first engine was a 1/4-scale model of the 5 hp Red Wing water-cooled engine (serial no. 580). “It looked like a hit-and-miss engine,” he says, “and I thought it was pretty cool.”

He followed that with a 1/3-scale 2-1/2 hp Red Wing air-cooled hit-and-miss engine (serial no. 11). The third model he built for himself is a 1/3-scale 5 hp Galloway water-cooled hit-and-miss. The engine has no serial number, he says, because it is unclear whether the numbers on the original engine were serial numbers or casting numbers.

Either way, he’s a fan of Galloway. “I like the Galloways because they have a larger piston and longer stroke,” he says. “The Galloway makes a louder sound when it fires, so it’s easy to hear the hit and miss. With the Red Wings, you have to listen close to hear the hit and miss.”

A deliberate approach

The scale model company has since changed hands and David is now working for the new owner. The company sends him the casting kits and he takes it from there. “I machine all the kits, supply metals, assemble it and make it run, crate it up and ship it to them,” he says. The entire process takes about 80 hours for each engine.

After removing the unpainted engine from the crate, David examines it and starts to work on the base. “Then I work on the part above it, followed by the area where the piston ends up going,” he says. “After that, I work on the various other parts as I take a notion to do them.”

The engine itself is made of cast iron. David provides most of the remaining parts. “I supply the metals,” he explains, “the parts on the engine that are not castings. I buy piston rings, metals to make a crankshaft, connecting  rods and a few other parts.”

He also provides round and hex brass stock, no. 303 stainless steel in round and hex, brass and mild steel in various shapes (including rectangle, key stock and sheet metal), as well as cold-rolled steel rod. And he follows the instructions very closely.

“I use the company’s blueprints, which are very detailed, to make the parts that are needed,” he says. “The blueprints tell me the kind of material to use and all the sizes and information to make the part. I do all the machining required for this engine, along with the timing gears, which come with the castings.”

Transferring career skills

In his scale model engine hobby, David uses the skills he acquired during a 40-year machine shop career. “I was fortunate to be hired by a company into their machine shop,” he says, “so I went through their training program. I did machine work most of the time, using a milling machine, and lathe work, along with some cylinder grinding. The last few years I did programming for a CNC machine.”

Today, most of David’s work is accomplished on an engine lathe and milling machine. “They are my two most useful tools,” he says. “I also use a drill press and a hand-held drill.” To make springs, he uses pliers and wire cutters. That process involves buying spring material (either a straight piece or a coil of wire) and winding each part around a thin rod to produce the spring.

Because some parts require extreme precision (within 1/1,000th of an inch), David occasionally makes a mistake. So far, he’s been able to work his way through any problem encountered. “At this point I’ve been able to fix most of them without very much trouble,” he says. “All my experience working with other engines really helps.”

Most of the scale model engines he’s built have been either Galloway or water-cooled Red Wings, although he did make a pair of Woodpecker engines. “The Woodpecker has an unusual tap, tap, tap sound during the ‘miss’ portion of the hit-and-miss cycle,” he says. Otherwise, it wasn’t dramatically different from the others. “Even though different engines’ parts might look different,” he says, “much of the process of building them is exactly the same.”

For the Red Wing engine’s trucks, varnished oak is used to produce a cart similar to that used by the original manufacturer. The Galloway also uses varnished oak, but those trucks are made with a brass rod at each end for easier transport. The Galloway model weighs about 75 pounds; the Red Wings weigh about 35 pounds.

Popular show display

Because they are smaller than the full-sized engines, models are easy to take to shows. There, they attract attention from people who’ve never seen scale model engines. “Some people ask, ‘What do you use them for?’ and I have to say, ‘Truthfully, they’re not good for very much,’” David says. “People ask how much horsepower they produce, and if I would have to guess, it would be a very small amount. Not more than 1/10 of a horsepower.”

Sometimes David hooks the engines to a water pump to turn a little water wheel. “The kids love to look at that thing. Adults like it too,” he says. “When I first started showing the green water-cooled Red Wing engine, someone wanted to know if it was a sewing machine.”

At times David has thought of building an engine from scratch. “I could use scrap metal and things from my shop, but I’ve never done it,” he says. “I’ve never taken the time to do something like that, because I’m fairly busy and don’t really have the time. I have so much going on during the summer that I like working on engines more in cool weather.”

Off and running

Once he finishes an engine, David is usually in a hurry to get it started. But things don’t always go according to plan. “Some engines have given me a little trouble getting them to run, but the more experience I get, the easier it is to get them going,” he says. “Lately, some of the engines I’ve cranked up are running on the first or second try.” After he gets them running, David returns the engines to the factory for painting.

Onlookers at shows are often surprised that the engines actually burn gas and run. The Galloway uses an igniter; the Red Wings use a spark plug for ignition. “Just common spark plugs,” he says, “like those you’d find at the local auto store.”

It’s meticulous work, but David enjoys the process of creating something for someone. “I like to think I’m a creative person, and these scale model engines are part of that,” he says. “When I finish an engine, I just hope the customer will like it, and be really satisfied with it when it cranks and runs well.” FC                     

For more information, contact Dave Stewart, P.O. Box 86, Lamar, SC 29069.

Bill Vossler is a freelance writer and author of several books on antique farm tractors and toys. Contact him at Box 372, 400 Caroline Ln., Rockville, MN 56369; email:

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