What Engine Is This

[JBodenmann]

Hello My Friends
A friend gave me this print to hang in the shop. He was surprised that I didn't know what engine it was and what railroad. I'm sure that some of you would know. It's obviously a simple articulated engine but aside from that I haven't a clue.
Jack

[randallg]

With the number board on top of the headlight and shape of tender tank it is likely a great northern .
Z6 possibly ?

[Short Line Tom]

Northern Pacific 4-6-6-4 #5118 (Z-6)
https://www.american-rails.com/4-6-6-4. ... allery]/3/ scroll down to pic #4

Cheers!
Tom

[rkcarguy]

What's with all the stuff on the front of the smoke box? The other one doesn't have that. It's much more easily recognizable as a challenger without it.

[Mike Walsh]

air pumps.

[Fender]

I’ve never understood why air pumps were mounted on the smokebox front vs. being mounted lower on the pilot deck or in front of the cylinders. Didn’t this prevent access to the smokebox, without having to disconnect the pumps? I know they had to go into the smokebox for monthly inspections.

[Comstock-Friend]

Dan, the smoke box door is rectangular between the pumps...

[Fender]

I guess they only had to take the whole smokebox front off to pull the superheaters and flues.

[Bill Shields]

ease of maintenance on the air pumps...right out in the open.

Many were mounted on 'swing out' frames so that you only had to disconnect air and steam line to pivot them clear of everything

[JBodenmann]

Hello My Friends
Thanks for all the info, I knew you guys would know. The main reason they put air compressors on the front of engines is that as they got bigger and the boiler diameter increased, there just wasn't clearance along side the boiler.
Jack

[Rwilliams]

Placement of the pumps on the front of the smoke box not only gave a more massive appearance to the front end, but also served other real engineering purposes. One was to get more weight on the front end of an articulated locomotive which often suffered from less than perfect weight distribution causing slipping of the front engine.

If a rigid frame steamer, the placement of pumps on the front end often helped to keep the driver axle weight within the maximum allowed for the track the locomotive operated on. A bit more weight on the engine truck was often welcome when axle weights were right at the maximum allowed for track and bridges. Often times just placing the pumps on the smokebox front could take the driver weight total down a bit and keep the crew pay scale at a lower rate for the life of the locomotive.

[Fender]

There are a number of reasons to put the pumps on the front. In addition to what has been said, it facilitated them being run on superheated steam, if the loco had a front-end throttle. But what I was getting at was why put them on the front of the smokebox vs. on the pilot like many other modern engines had. I guess there wasn’t enough room in some cases.