“Some fans cry whenever the MTA retires a train,” Max Diamond, a/k/a DJ Hammers, told a reporter recently. “I don’t go that far.” Celeste Sloman

With his back to an oncoming train and his hands pressed firmly over his eyes, Max Diamond strains all the muscles in his face as he tries to guess — by sound — which train is lumbering into the Broad Street subway station in Lower Manhattan.

He takes it all in: the melodic whine of the motor, the hiss of an air compressor, the airbrake’s distinctive squeal. Before the train is even halfway into the station, he smiles. “It’s an R160,” he says. “Probably in the 8000 or 9000 series.” Diamond knows he’s right before he opens his eyes; the tritone hum of an electrical component was the giveaway. And he is right — it’s an R160. But he glances over anyway to check the car number, the digits affixed to the train’s siding that can help identify its specific series. He’s spot-on about that, too: 8516 glides past in a blur.

There are a few telltale indicators, noticeable to even the most incurious commuters, that let us know whether we’re in a new or old subway car. (Are the announcements automatic, or are they delivered — possibly unintelligibly — by a conductor? Is the interior bright with shiny silver and blue, or is it dark, depressing, and somewhat reminiscent of the set of a Seventies game show?) But Diamond’s knowledge of the New York subway system borders on the encyclopedic. He can tell you why a decision made twenty years ago to remove “inshot valves” slightly changed the way engineers apply the brakes. He knows the radio code operators use when someone falls onto the tracks. (It’s 12-9, if you’re scoring at home.) He will point out the system’s most important “interlockings” — the areas where tracks separate and merge — as they zoom past in complete darkness.

For most riders, the subway’s noxious odors, man-spreaders, and migraine-inducing screeches are just the inevitable accompaniments to life in the city. But to Diamond, riding the subway is as much about learning the system’s subtle intricacies as it is about actually getting anywhere. A nineteen-year-old City College sophomore with neatly coiffed brown hair and a boyish demeanor, Diamond is disarmingly normal. The more you talk to him, though, the clearer it becomes that he is an autodidact transit savant. His freakish level of technical knowledge has made him a cult figure among “railfans,” a term used to describe train enthusiasts the world over. “If I go to a vintage train event or something, people will say hi to me even if I don’t know them,” he notes.

In context, his renown makes sense. As flawed as the city’s transit system may be — and as soul-crushing as those flaws can make your daily commute — the subway remains the throbbing heart of daily life here. And few know more about how it all works than the kid who calls himself DJ Hammers.

“If it was really just about the content knowledge, I would tell you absolutely he could operate a train today,” says Virgil Talaid, an education specialist at the New York Transit Museum, where Diamond spends some of his free time as a volunteer. “He’s beyond the knowledge of a lot of the staff we have.”

Diamond shooting his favorite train model, the grungy R32, which began rolling in 1964 Alex Zimmerman

“I’ve always been interested in the subway, ever since I was a toddler,” says Diamond, who remembers smuggling a book full of illustrated trains out of his preschool library. Though he was born in Park Slope — F-train country — he was raised in Westchester, far away from the underground beast that would one day capture his imagination.

He still prefers to ride in the first car, the better to get a glimpse of the tunnels out the front window. On this day, we’re riding a Brooklyn-bound J train past Chambers Street as part of a “railfanning” trip when Diamond notices an M train, which definitely isn’t supposed to stop at this station. It must be a reroute, he concludes.

“I’ve seen that like a billion times,” Diamond says. He’s already trying to diagnose the problem. “That same issue that’s causing that reroute may be causing some other interesting reroute that I’d like to catch. There’s probably an issue in Queens or Manhattan.” Later, after transferring to an N train at Canal Street, we emerge from the tunnel to cross the Manhattan Bridge. Diamond whips out his iPhone and pulls up a PDF schematic of the entire system’s track layout. Then he checks the MTA’s website. Right again: There’s a track problem in Queens, though nothing worth investigating. “If you have an understanding of the track layout and how the lines connect, you can almost guess or figure out [what’s wrong] based on one rerouted train,” he says.

Diamond has been a folk hero among train aficionados for some time, but recently he’s crossed into the mainstream. Using his online handle, Diamond curates a popular (among train geeks) YouTube channel, posting videos that document the various idiosyncrasies he discovers along the system’s more than 600 miles of track. He’ll sometimes spend hours shooting footage for what will eventually amount to a three-minute clip. His videos capture ordinary trains doing ordinary things, although their titles sound like Star Wars erotica — “R62A and R188 7 Train Action at 46th Street,” anyone? That video, one of his greatest hits, is nothing more than ten minutes of trains pulling into and out of a station. It has more than 95,000 views.

The YouTube channel is popular enough that Diamond is starting to attract fans of his own. During a recent event in a program for young autistic railfans that he helps run at the transit museum, some of the participants recognized him immediately. “A couple of these kids tapped each other on the shoulder and said, ‘That’s DJ Hammers,’ ” says Talaid. “They were in disbelief, apparently.”

Since he launched the channel in 2009, Diamond has posted more than a thousand videos that, together, have been watched more than 2.2 million times. He now boasts 4,500 subscribers. Some of his clips — like an entire rush-hour run shot from the front window of a 7 train and sped up to ten times the norm — are strangely soothing. A few of those time-lapse entries have been republished by media outlets with headlines such as See what a train operator sees while riding the 7 line. “Am I surprised that there are some people interested?” he says. “No. Am I surprised that there are this many people interested? Yeah — some videos transcend the line between the railfans and the general populace.”

Due largely to the popularity of his YouTube channel, Diamond’s media profile has grown dramatically over the past few months. He has become something of a go-to expert for some of the city’s transit reporters, especially those tired of trying to chase down comments from the notoriously tight-lipped MTA. “People [are] interested in understanding how the system works, why delays happen,” he says. “The questions people ask are symptomatic of people seeing things and not understanding why they happen.”

A recent video he posted helped break the news that the MTA might abolish its iconic “stand clear of the closing doors” announcement, and Diamond has been quoted as a transit “enthusiast” by Vice, amNewYork, the New York Post, and the city’s CBS affiliate. He recently hosted a Reddit AMA (the title: “I’m an NYC Subway Expert. Ask Me Anything”) that garnered more than seven hundred comments, from the technical (why hasn’t the MTA upgraded those glitchy loudspeaker systems?) to the morbid (is it true that many train delays are caused by suicides?). No one asked, but he’ll also tell you when you’re most likely being watched by a hidden camera (beware of the car numbered 4792, J-train riders).

Reporters trust Diamond because he can offer more detail than most press releases and because he spends countless hours poring over contracts, budgets, and RFPs — all of which are available to the public (and to journalists), if you’re into that sort of thing. One reporter recently asked him if he knew the vertical distance a set of escalators travel in the newly opened Hudson Yards station. Diamond instantly found the MTA document with the station’s specs and calculated the answer in minutes: 81.4 feet. “It’s stuff you could figure out as a member of the public if you dig hard enough,” he says. But Diamond is careful not to speculate or give out information he can’t verify: “I don’t want to end up [saying] something that may end up being inaccurate or might damage my credibility.” After all, he hopes to maybe work for the MTA someday.

And does the agency know of the existence of its most plugged-in non-employee? “I’ve never seen him say anything or quoted as saying anything we don’t believe is true or [believe to be] harmful to the MTA,” says Adam Lisberg, an agency spokesman. “If he’s got a deep understanding of the system and is building a media presence based on it, all the power to him.”

Diamond at the Corona Yard in Queens Celeste Sloman

Last spring, Diamond played a key role in the eventual arrest of “the Conquestors” — a group of pirate railfans whose small-scale pranks escalated into commandeering trains and causing small explosions on the tracks by placing pieces of metal on the electrically charged third rail. The group regularly boasted on Facebook and posted videos of their “Conquested” trains. “They had enough innate interest in how the system worked to draw a connection to this community, and that’s sad because it kind of paints [railfans] in a bad light,” Diamond says. “It got to the point where another month or two [and] someone would get killed.”

So Diamond traded in his Clark Kent glasses for his Superman cape. “I realized I should just take one of these videos they’re posting on Facebook and send it in,” he says. After copying the Conquestor videos to his own YouTube channel and sending the links to local reporters, Diamond says, “The media coverage sparked some action and they were arrested.” In fact, his documentation of the Conquestors is partly what put Diamond on the MTA’s radar in the first place. “I think it is safe to say that him shining the spotlight on these guys drew everyone’s attention to it much more quickly in ensuring appropriate action was taken,” the MTA’s Lisberg says.

Over the past few months, Diamond has returned to scouting new construction projects and irregular train-traffic patterns. Winter Storm Jonas, he says, was a boon. “I took advantage of the fact that we had a huge blizzard coming and basically filmed all the unusual stuff that happened. It was a lot of fun.” A video he shot of an L train running along the A track to be stored away from the snow has already racked up almost 5,000 views.

It’s hard not to think Diamond’s interest borders on obsession, but he bristles at that description. “Some fans cry whenever the MTA retires a train,” he recently told Vice. “I don’t go that far.” The way Diamond sees it, he’s “a hobbyist, or just a historian.” It just so happens that his hobby can help demystify a system millions of people use every day.

“I’m not riding the subway every day just because,” he says as the evening commuters emerge from the Broad Street station. “I wouldn’t want to do that. I would get so bored.”