HO scale model trains are 1/87 the size of real trains and 1/2 the size of O scale model trains (HO stands for "half O"). As with O scale trains, the letter "O" in HO is a misnomer since the designation was initially conceived as a zero to identify trains that were smaller in scale than 1. But the use of the letter O rather than the numeral 0 crept into everyday speech among model-train buffs and remains the standard way to refer to HO scale today.

Though first invented in the 1930s, HO scale model trains didn’t become popular in the U.S. and Europe until the 1950s when the scale was heavily promoted by Märklin, Lionel, Athearn, and others. HO never quite gained acceptance in England, though, where larger 00 scale trains still predominate.

HO has two important benefits over trains of larger sizes. First, an HO scale layout of reasonably ambitious detail and complexity can fit on a table rather than requiring an entire room, as is the case with larger scales. Second, HO trains are less expensive to manufacture than OO, O, and other large-scale trains, which makes them more affordable to collectors and enthusiasts alike.

Most HO scale trains run on two-rail tracks using direct current (DC). Adjusting the voltage delivered to the tracks can increase or decrease the speed of the trains; reversing the polarity causes the trains to roll in reverse. Some manufacturers, notably Märklin, produce HO scale trains that operate on alternating current (AC), which is delivered to the train via a conductive third rail.

The gauge used by the majority of HO scale model trains is a standard HO gauge track that’s roughly proportional to the size of the trains running on top of it. But as with the OO scale trains in England that run on HO gauge tracks, HO scale trains are also made to run on a variety of different gauge tracks, which themselves are scaled-down versions of historical railroad track sizes.

Of these variants, the most common is called HOn3. This code denotes an HO scale train running on a track similar to the 3-foot, narrow gauge tracks used by Rocky Mountain railroad operators in the late 19th century.

One of the most enjoyable aspects of HO for collectors is the opportunity to join a local module club. Members of such clubs build modules of predetermined size; each module has a finite length of track. When members get together at model train exhibitions or in private homes, the modules are linked up and trains are run on the resulting massive layout, which often feels like more than just the sum of its parts.

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Airfix Model Railways

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Gateway NMRA

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Postwar Lionel Trains Library

Postwar Lionel Trains Library

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Eric's Trains

Eric's Trains

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Tech Model Railroad Club of MIT

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Recent News: HO Scale Model Trains

Source: Google News

REC: Marveling at model trains
Sierra Vista Herald, May 23rd

Dan Bolin, president of the club, has loved trains, “ever since I was a kid,” he said, a common refrain from others in attendance. The club features a main layout of an HO scale occupying two large rooms. There is an N-scale layout under construction...Read more

Show 'n Shine
U-T San Diego, May 21st

Tours of the Escondido History Center include a barn with vintage vehicles, working blacksmith shop where classes are taught, 1888 train depot filled with photographs and exhibits and a railroad car with an H-O scale model train inside. Also featured...Read more

Model railroads a fun past time for group at Henry Ford Village
Dearborn Press and Guide, May 20th

Paul Atkins, a retired NASA engineer, uses a DCC (Digital Command and Contol) handheld wireless unit, to operate a train on the Henry Ford Village HO model railroad. Residents in the Henry Ford Village Model Railroad Club can operate up to four trains ...Read more

Meet the electrical engineer who powers his passion in South Elgin
Chicago Daily Herald, May 18th

Now 31, Pechous has an electrical engineering degree and uses it to modernize the power system that drives as many as 15 trains at a time on almost a mile of model train track at the club's headquarters in the historic Clintonville Station in South Elgin...Read more

Model railroad club testament to timelessness of trains
Longview Daily News, May 8th

Ray Bilodeau, who has been a member for four years, sat in another corner, using a pair of large magnifying glasses to renovate HO-scale train cars, a skill he learned from other club members. He said he enjoys seeing young and old react to the club's ...Read more

Model train show rides into Augusta Expo
Staunton News Leader, May 3rd

"There's sound and options to turn on lights that you didn't have way back when," he said. The appeal of model train building is recreating the scene of a real train. With HO scale models, there are numerous option of finding different types of trains...Read more

Fairgrounds not renewing lease with railroad club
Benitolink: San Benito County News, May 1st

A big issue Feltman anticipates is losing a large portion of the current display. “The layout as it exists now, at least half of it will be gone,” he said. “The older layout of our HO scale is going to be torn down, as will a bunch of the N scale. They...Read more

All aboard! Rutland RR Museum celebrates trains, past and present
The Eagle, April 27th

A visit to the museum should include a peek at the miniature HO scale train layout erected by the Rutland Railroad Museum Model Railroad Club. #“Children of all ages will delight in our room-sized HO scale operating display and N-scale model railroad...Read more