A milestone was reached Thursday when a nine-ton boiler was hoisted onto a steam locomotive that is being restored in Medford's Railroad Park.

A milestone was reached Thursday when a nine-ton boiler was hoisted onto a steam locomotive that is being restored in Medford's Railroad Park.

The 1925 Medco No. 4 locomotive has been undergoing restoration by the Southern Oregon Railway Historical Society for 15 years.

"The boiler is the heart of a steam locomotive and is the largest and most expensive part of this restoration effort," said Jerry Hellinga, chief mechanical officer and project manager.

In addition to the boiler, workers installed the steam engine and the cab for the 70-ton locomotive at the park, located off Berrydale Avenue.

An $18,000 grant from the Oregon Cultural Trust helped pay for the boiler restoration performed by Chelatchie Boiler Works Inc. in Washington state.

On Thursday, Hellinga and other train buffs struggled to mate the boiler to the frame.

Hellinga laid on his back, his head resting against the tracks, while he helped direct a crane operator. As Hellinga peered up through the frame, the crane operator raised and lowered the boiler, which resembles an antique submarine.

After much trial and error, the massive frame and boiler were reunited.

The engine with three cylinders was then mounted, though some of the bolt holes didn't quite line up as expected.

Grenada, Calif., resident Bill Ainsworth offered his expertise to help put the pieces together on the complicated-looking contraption.

"I've been messing with these things for about 20 years," he said.

With the major reassembly completed, the next step in the restoration will involve rebuilding the appliances, piping and valves that will make the boiler functional. The work is being funded by $2,500 in grants from the National Railway Society and $5,000 from the Oregon Cultural Trust.

Hellinga said it will probably take about two more years before the locomotive is fired up.

The historical society obtained the locomotive in 1998, and it was dismantled the following year.

"It's been sitting here for several years," said Tom Baldwin, a member of the historical society.

Steam engines have always required a lot of maintenance, even in their heyday. They were still being built in China until 1981, Baldwin said. Before World War II, the U.S. continued to produce steam engines because the materials were cheaper and more readily available than for the more popular diesel locomotives.

"A lot of railroads had to settle for steam instead of diesel," Baldwin said.

The Medco No. 4 is one of 33 locomotives built between 1923 and 1929 by the Willamette Iron and Steel Company of Portland. The locomotive is the only one of those engines still in Oregon.

Built for the Medford-based Owen-Oregon Lumber Co., the engine transported timber around Butte Falls.

The lumber company failed during the Great Depression and was reorganized as the Medford Corporation.

The locomotive was retired in 1959 and donated to the city of Medford.

Restoration began one year after the city donated the locomotive to the historical society. Since then, $215,000 and 6,750 man-hours of work have been invested.

Baldwin said the boiler is the most significant piece of the restoration. It has to be certified to withstand continuous pressures of 200 pounds per square inch.

"It has tremendous pulling power," Baldwin said.

Once completed, the locomotive won't be able to travel very far in its current location.

"Right now, there is no track for it," Baldwin said.

Reach reporter Damian Mann at 541-776-4476 or dmann@mailtribune.com. Follow on Twitter at @reporterdm.