“The Salt Lake City Police Department is investigating a suspicious item that resembled a possible explosive device,” the Salt Lake City Police Department’s press release from yesterday begins. “This investigation started at 9:49 a.m. on Wednesday, June 29, 2022, when SLC911 received information about a possible explosive device in an apartment, located at 999 South Main Street. Officers responded, secured the scene, and evacuated parts of the apartment complex, including the center courtyard. The evacuations were done out of an abundance of caution.” The release goes on to say that the “on-scene incident commander” asked for help from the department’s “Hazardous Devices Unit” which is “a member of Utah’s statewide Bomb Response Task Force and is accredited by the FBI.” The unit includes not just Salt Lake City Police Department members, but also support from “FBI-certified bomb technicians from the Salt Lake City Police Department’s Airport Division and the University of Utah Police Department.” The press release lists off some of the team’s capabilities just to show that these folks mean business: Wow, that all sounds pretty serious. This must be the most overqualified team of humans ever to have escorted a timing belt tensioner out of a building. Oh yeah, that’s right — this grenade-looking device is nothing more than a spring-loaded belt tensioner/damper for a VW Passat, Audi A5, or Audi A6. Its job is to make sure the engine’s timing belt — which wraps around the crankshaft and camshaft sprockets to make sure the valves open at the right time relative to the pistons’ stroke (you want the valves open as each piston goes down during its intake stroke so you can pull in fuel/air, closed as the piston goes up during the compression stroke so you can seal the combustion chamber, open as the piston goes back up after the combustion stroke so it can shoot exhaust out, etc.) — is nice and taut. Here’s a look at that timing belt tensioner/damper in-vehicle: You can see how it pushes against a lever that’s part of a bracket to which the tensioner pulley is fastened. The tensioner helps to torque the bracket around the pivot bolt, forcing the pulley against the belt to keep the belt tight. The tensioner itself contains a piston that doesn’t just have a spring on its back side, but also oil; so the device isn’t just there to help keep belt tension, but to act as a hydraulic damper to keep that tension steady under loads/vibrations so the pulley doesn’t bounce around and throw the belt off. This would be quite bad, as that belt flying off or even slipping could let the pistons rise at the wrong time, and if that “wrong time” happens to be when the valves are open: BANG, you’ve destroyed your engine. This has happened to our very own Jason Torchinsky not too long ago:
Rock Auto, your favorite site for dirt-cheap car parts, actually does a great job breaking down how a hydraulic belt tensioner works, and even includes a cutaway of the very “possible explosive device” that led Salt Lake City Police to call the bomb squad and evacuate an apartment building: Because there’s a spring trying to force that piston out against a timing belt tensioner bracket/lever, the way you install these devices is you bolt them into place, then remove a pin (which does look like a grenade pin or a fire extinguisher pin), which allows the piston to apply pressure to the tensioner bracket. Here’s a look at a guy removing the pin from his timing chain tensioner (which is quite similar to a timing belt tensioner):
I called the Salt Lake City Police Department, and they told me they’d figured out that it is a timing chain tensioner (close enough). The department has been getting some hilariously snarky comments on Twitter about this, as you might imagine. Have a look:
— Mike Ganas (@MikeGanas) June 30, 2022
— sPibot (@pibot_s) June 30, 2022
— Karen (@kadelopa) June 29, 2022
— Frankfürter (@Birdsonbranches) June 30, 2022
— Mike Ganas (@MikeGanas) June 30, 2022
— gina @ SOW track prep ✨ (@s2kgina) June 30, 2022 It’s the tweet from “Localized datum structure enjoyer” that resonates with me the most:
Give it back to that poor renter. — Localized datum structure enjoyer (@literallyantifa) June 30, 2022 Seriously, give that thing back to the poor renter. They’ve got the real grenade right there under the hood of their VW/Audi, and it could go off any second! Update (June 30, 2022 6 P.M. ET): The Salt Lake City Police Department, whom I applaud for having taking precautions in this instance but whom I’ll also poke fun at because mistaking a timing belt tensioner for a bomb is still funny, sent me this statement unsolicited after I published the initial article: Thank you for your interest in this story. And to be fair i’ve never seen a car part with such an obvious granade pin XD /jk In all of the 300Gazillion people in the world… we cant find 1 who can I.D a car properly?
