Union Pacific's "Big Boy" No. 4014 Steam Locomotive at FULL Throttle! Turn Volume UP!

[@daemn42]

If you look at the smaller horizontal bar above the main driving rods, you'll see that the forward end is relatively fixed and just moves fore/aft and the rear end is connected to a fat vertical bar with a curved slot in it that is rocking back and forth around a fixed point. That is the Walshearts valve gear setup, which is effectively the throttle and reverser. The horizontal bar can be moved up and down within that slot, so that at the ends it stokes further letting more steam into the drive pistons at each end before it's cut off. Visually the closer the rear end of the horizontal bar is to the pivot point in that slot, the closer to neutral or zero throttle it is. Full throttle forward would have that horizontal bar slid all the way to the bottom of the slot. For max efficiency though, you want to let steam in for only about 20-25% of the stroke and then just let it expand to closer to atmospheric pressure before exhausting it. When you let in much more steam than that, then it doesn't have time to fully expand, and your exhaust higher pressure steam and that's what makes the "chuff" sound we associate with smaller, less powerful steam engines. With more steam the instantaneous push (or torque) is higher throughout the stroke but you're exhausting high pressure steam before it has done all the work it could do. As it relates to UP4014... Since it's bean restored, I've yet to see any video where it's running at more than about 20% throttle, or really ever heard it chuff meaningfully. Either it's just so powerful that it's idling most of the time, or it's getting a little help from the diesel engine behind it (used to conserve fuel/water/brakes), or both.

[@FlatheadTerry]

WoW! Thanks for the detailed information! Learned something new today.

[@maxwellsteam5810]

Not really Full Throttle, but Ed did have her open pretty good. If it was Full Throttle you'd be hearing the Stack Talk before the whistle haha.

[@FlatheadTerry]

Thanks for your insight! Good to know!

[@ironcladranchandforge7292]

It's a good thing I read the comments first because I was going to say the same thing, LOL. Not full throttle!!

[@Joe_C13T]

“he”

[@maxwellsteam5810]

@@Joe_C13T get a job

[@waynemiracle8928]

You sure don’t see that kind of trains anymore! Thanks for sharing!

[@terrybeckham8118]

She was designed to be stable at 80mph so that wasn't "FULL throttle" but that might be as fast as they'll let her go now to protect her components

[@FlatheadTerry]

@terrybeckham8118 Thanks for the info Terry. I was just guessing at it. It just went flying by and the crowd barely had time to enjoy it!

[@Joe_C13T]

“he”

[@ronaldosorenstein3546]

What an incredible was of train we know that combo could easily hauls some cargo too

[@SGTDuckButter]

Sweet Jesus

[@AndrewRolfe-j7u]

What an amazing locomotive. All those carriages are deadweight. Not one is a driver. So that locomotive has to pull every one on its own. Yup, the entire train, from a standing start, unaided. The torque required and the traction to transmit that torque with that unbelievably enormous dead weight. No superlative can do justice to that single locomotive.

[@James-xo4uv]

Nice