New Belpaire firebox emerges for K4s 1361
The first new Belpaire steam-locomotive firebox built in Altoona, Pa., in 76 years is taking shape at the Railroaders Memorial Museum there.
In early December 2022, employees of consultant FMW Solutions
LLC and volunteers fabricated a new firebox for former Pennsylvania Railroad Class K4s 4-6-2 steam passenger engine No. 1361 (Juniata Shops, 1918). The last such work was completed in 1946, when the Pennsy built 25 T1-class streamlined 4-4-4-4 passenger engines in its shops there. Those locomotives, along with others, were supposed to replace the road’s 425-member K4s fleet, but instead were themselves quickly replaced by diesels starting in 1947.
No. 1361 is undergoing a $2.6 million restoration to return it to running condition. One of the obstacles is the original mechanical specifications — drawn up by Pennsy in 1914 — do not meet present-day federal pressure-vessel safety standards. The museum has hired FMW to engineer and build a new firebox that’s visually identical, but with thicker steel and other modifications that simplify and strengthen the component.
Shane Meador, FMW vice president-mechanical, and Zach Hall, an FMW foreman, oversaw the work of cutting out 7/16-inch steel plates for the side and roof sheets, then assembling and welding them together to form a new firebox. Pennsy used 3/8-inch steel, which doesn’t meet the Federal Railroad Administration’s “factor of 4” standard that a boiler must withstand a force of four times its normal operating pressure — for a K4s, 205 psi.
The unusual squared-off Belpaire top results from a standard Pennsy adopted in the 19th century, differing from the radial, smoothly rounded shape of most North American locomotive boilers. Many British and European steam engines employed the Belpaire design, as did many Great Northern locomotives.
Used on thousands of Pennsy locomotives of many classes, the odd shape added to the cost and complexity of No. 1361’s restoration, including press-brake work to gently bend the side plates to meet the dimensions of the squared top.
Pennsy retired No. 1361 in 1956 and placed it on display at Horseshoe Curve. In 1985, the museum removed it from display and restored it to operation for 19861987.