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

This is a short video of Union Pacific's "Big Boy" No. 4014 Steam Locomotive at full throttle as it passes thru Sussex, Wisconsin in July 2019.
Twenty-five Big Boys were built exclusively for Union Pacific Railroad, the first of which was delivered in 1941. The locomotives were 132 feet long and weighed 1.2 million pounds. Because of their great length, the frames of the Big Boys were "hinged," or articulated, to allow them to negotiate curves. They had a 4-8-8-4 wheel arrangement, which meant they had four wheels on the leading set of "pilot" wheels which guided the engine, eight drivers, another set of eight drivers, and four wheels following which supported the rear of the locomotive. The massive engines normally operated between Ogden, Utah, and Cheyenne, Wyo.

[daemn]

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.

[ronaldosorenstein]

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

[maxwellsteam]

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.

[waynemiracle]

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

[terrybeckham]

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