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Written by Bob Angel
As seen in the June 2019 issue of
Model Aviation.


Check out the History Project biography for Irwin Ohlsson online!

DURING THE 1940S, when a neophyte modeler asked for suggestions as to what engine he or she should choose, he or she would likely get a quick answer: "An Ohlsson 23." That was the shortcut name for the Ohlsson & Rice 23, which was also commonly abbreviated as O&R 23.

The name came from the producers, Irwin Ohlsson and Harry Rice. The 23 was derived from the .23-cubic-inch displacement and it is thought to be the first time that the size of an engine was combined into its name. That’s since become customary.

The 23 wasn’t the first of the many sizes of engines that O&R built, but it’s still remembered by many modelers as the company’s first engine. It had a reputation for being easy to start and reliable, with long-lasting performance while being reasonably priced. Most hobby shops stocked it, along with a fairly complete complement of spare parts.

Irwin was an accomplished, lifelong modeler who built his first model engine in 1934. He later partnered with Harry, an expert machinist, who took the lead in design and engine production. Irwin steered the business end, expanding the line of engines and accessories.

The sideport 23 engine was produced from 1938 through 1949. It had a long intake tube extending rearward, usually with a fuel tank attached below the tube.

In mid-1949, as glow plugs became popular, the 23 was produced as a front rotor design, along with the .19 and .60 sizes. All three of those sizes were produced as either glow or spark ignition. At roughly the same time, the O&R 29 and 33 came into production and were available as spark ignition or glow versions, but they were front rotor only.

steve roselle prepares his o and r 60 powered andersen spitfire
Steve Roselle prepares his O&R 60-powered Andersen Spitfire. This big brother to the O&R 23 also has its own special event. Eaton photo.

Let’s look at some of the technical details of the O&R 23. Many of the 23’s features were shared with other O&R engine sizes. They were designed to be lightweight with thin aluminum crankcase walls. The onepiece steel cylinder walls and head were also fairly thin, but the integral cooling fins around those cylinder walls helped maintain cylinder roundness.

A unique feature of these engines was the cylinder-to-crankcase attachment that did not use screws. A gasket was placed at the bottom cylinder flange and the cylinder was inserted down into the case. The two parts were pressed together, compressing the gasket, while two small, steel slugs were spot-welded through holes in the case’s front and rear. Small, aluminum slugs were pressed into two holes to complete the signature little, round bosses you’ll see on each of these engines.

This one-piece assembly didn’t allow modelers to disassemble and reassemble the parts themselves, which was a mixed blessing. If an engine was damaged or the piston fit was worn, it had to go back to the factory for parts replacement. In that era, shipping costs and factory overhaul were much smaller than the price of a new engine, so it was worth it. The factory placed an X before the serial number of engines that had been repaired.

The enclosed timer for the Ohlsson 23 was designed by Harry and later copied by other manufacturers. An identical timer was used on other .19- through .60-size O&R engines. If left untouched, it would work well for many hours of running time, but after it was disassembled, it was one of the peskier parts to readjust. Had Harry simply made the timer cases approximately 1/8 inch larger in diameter, they would have been much easier to assemble.

Many of us who were apprentice engine mechanics learned to take apart and reassemble these engines whether they needed it or not. I was surprised some time ago when I heard from a modeler who thought removing the piston was part of the required factory process. It isn’t. The simple trick is to remove the front plate and crankshaft, insert a 1/4-inch dowel into the bottom of the connecting rod (conrod), rotate it 90°, and bring it forward to where the piston can be fished down and out.

As with the timer, it’s generally not necessary, nor is it desirable, to disassemble the conrod from the piston. The piston pin’s tiny snap rings can be distorted, lost, or not placed properly into their grooves. If the rod is removed, it must go back with the more-protruding side of the lower bushing facing forward to clear the crankshaft. At the same time, that piston baffle should be assembled to the engine’s right and opposite the exhaust. The rest of the engine is otherwise easily disassembled and reassembled without instructions.

The Society of Antique Modelers (SAM) created a special RC event just for the Ohlsson 23 because it isn’t quite as competitive as many others in the Class B size (.20 to .29 cubic inch), yet it is abundant and treasured, especially by those who used it early in their modeling careers. Nearly 800,000 O&R 23s were thought to have been built.

come to think of it, many of us older people would be as happy today
Many youngsters would have been delighted to find this under the Christmas tree in the 1940s. Come to think of it, many of us older people would be as happy today.

At the 2019 SAM Champs, scheduled October 28 to November 1 at the El Dorado Dry Lake Bed in Boulder City, Nevada, the Ohlsson 23 will be a featured special event with relaxed rules. Specifically, the spark-ignition-only restriction will be dropped and glow ignition will be allowed using FAI (no nitro) fuel.

Scaling will be allowed. The existing rules allow stronger-running, front-rotor engines to be used with a shorter run time. The .19 sizes will also be allowed, using the same run time as the 23s. The SAM website, listed in "Sources," has the complete current rules.

Lost Model Finders

After I wrote about retrieving errant models in my February 2019 column, I received a couple of reader suggestions for lost model alarms. The one Michael Kukla suggested is a unit with no name, but I found it on the internet by searching for "lost model locator." Several sellers have them priced at approximately $2 to $3 each, postage free, but they are usually only sold in batches of a half dozen or more.

These small units weigh approximately 1/6 ounce. They are simple, little beepers that plug into a receiver port and begin sounding after a minute or so of no active transmitter signal. The inactivity can be anything from no stick movement to the transmitter being completely off.

A few years ago, I tested similar units that had a single protruding wire with a male servo plug. I bought a few of these newer ones and tested them. These have two wires, one with a male servo plug and the other with a female. The single male plug works okay alone, so the female one should be used when all receiver ports are occupied. That allows the servo signal to pass through in series to operate the servo normally while the alarm goes about its business.

They can also let you know when you’ve unintentionally left your receiver on. The only negatives I found were that the sound volume isn’t high and the advertised 200- to 300-foot range is questionable. The pitch is quite high and one modeler couldn’t hear it from 5 feet away.

Gary Maas recommended another unit called a Tile. It is marketed in several versions for use with smartphones to locate misplaced keys, wallets, kids in malls, etc. There are too many features to describe here, so you can study them in detail on the internet.

the venerable ohlsson 23-2
David Alchin displays his immaculate Snow White. The Snow White is seldom modeled, but is profusely photographed whenever one does appear. Photo by John Eaton.





AMA History Project

Biography of Irwin G. Ohlsson

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