BS: Resurrection of a Big Boy 4-8-8-4 locomotive

Subject: RE: BS: Resurrection of a Big Boy 4-8-8-4 locomotive
From: DaveRo
Date: 08 May 19 - 05:42 PM

This describes one pretty well:
https://en.m.wikipedia.org/wiki/Garratt

The middle section of the three has the boiler and cab, and both front and back sections have the cylinders and driving wheels. The back one has the coal bunker on top and, from the picture, it looks like the front one has the water. (I would expect it must be important to get the weight distribution right to maintain traction as the coal and water reduces.)

The tricky part of this concept is the need for flexible high-pressure steam pipes between the sections!

Subject: RE: BS: Resurrection of a Big Boy 4-8-8-4 locomotive
From: Joe Offer
Date: 27 Jun 19 - 01:57 AM

Here's Mike Armstrong's great video of the Big Boy on its first trip since it was restored:

https://www.youtube.com/watch?v=aX26XzZVQus

Seems that the train drew huge crowds wherever it went. I'm thinking of following its Midwest trip next month on my drive to or from Detroit, but the thought of crowds makes the idea less enticing.

-Joe-

Subject: RE: BS: Resurrection of a Big Boy 4-8-8-4 locomotive
From: Joe Offer
Date: 30 Mar 20 - 03:11 AM

This Big Boy locomotive video is called "The Great Race Across the Southwest.Chasing and Pacing!" Dumb title, but it's so good I could almost call it "railroad porn."

https://www.youtube.com/watch?v=xT6B3a9eZzM

Subject: RE: BS: Resurrection of a Big Boy 4-8-8-4 locomotive
From: leeneia
Date: 30 Mar 20 - 11:28 AM

Thanks for the info, Dave Ro.

Subject: RE: BS: Resurrection of a Big Boy 4-8-8-4 locomotive
From: JHW
Date: 30 Mar 20 - 03:03 PM

Saw O gauge or bigger Steam powered artic model earlier this year, radio controlled, big boiler on 2 driving bogies.

Subject: RE: BS: Resurrection of a Big Boy 4-8-8-4 locomotive
From: gillymor
Date: 30 Mar 20 - 03:34 PM

Wow, seeing that beast in motion is mind-blowing.

Subject: RE: BS: Resurrection of a Big Boy 4-8-8-4 locomotive
From: Joe Offer
Date: 14 May 20 - 03:30 AM

The Big Boy is a 4-8-8-4 articulated locomotive. I thought that was as big as they got, basically two locomotives under one boiler, hinged in the middle. But Wikipedia has an article on Triplex locomotives with three sets of 8 driving wheels and 6 cylinders. The triplex locomotives were unsuccessful, and were rebuilt into 2-8-8-0 and smaller locomotives.

There were plans for Quadruplex 2-8-8-8-8-2 locomotives and even a Baldwin Quintuplex 2-10-10-10-10-10-2, but these were never built.

-Joe-

Subject: RE: BS: Resurrection of a Big Boy 4-8-8-4 locomotive
From: Joe Offer
Date: 14 May 20 - 06:07 PM

Here's a fascinating YouTube video, titled How Gresley's A4 Pacifics became the World's Fastest Steam Engines:

https://www.youtube.com/watch?v=hp7k36hXeb0

Seems to me that there's a difference in the connecting rods between US and UK steam locomotives, but I'm not exactly sure what that difference is. The connecting rods on UK locomotives seems to be continuously horizontal, and the US connecting rods look different. What's the difference, and why?

-Joe-

Subject: RE: BS: Resurrection of a Big Boy 4-8-8-4 locomotive
From: DaveRo
Date: 15 May 20 - 04:40 PM

That was a very comprehensive video. I noticed some railwaymen's jargon crept in. Do US railways have 'consists' and 'diagrams', I wonder?

Joe Offer wrote: Seems to me that there's a difference in the connecting rods between US and UK steam locomotives, but I'm not exactly sure what that difference is. The connecting rods on UK locomotives seems to be continuously horizontal, and the US connecting rods look different. What's the difference, and why?

I don't know about US locos in general, but take a look at this photo of Big Boy from the US National Railroad Museum website.

The sloping bar is the connecting rod and drives the third wheel back. In common with all (?) locos there is one or more horizontal coupling rods joining all four wheels, but you can barely see most of it behind other gear.

I think on most British locomotives the coupling rods are more visible. See this photo for example - though in that case it's stopped with the conecting rods and the coupling rods all lined up.

Subject: RE: BS: Resurrection of a Big Boy 4-8-8-4 locomotive
From: Black belt caterpillar wrestler
Date: 15 May 20 - 06:47 PM

Most UK loco designers seem to have tried to keep the cylinders horizontal and the centre line of them close to the centre line of the axles. There were exceptions such as the LMS "Crabs", but that was unusual enough for the design to have acquired the nickname because of the different appearence.

Churchward on the GWR kept his cylinders horizontal but allowed them to be 2.5" higher than the centre line in order to get sufficient outside clearance on the "loading gauge", that is the outline profile that all the stock on the line had to fit inside. UK loading gauge is much more restricted than USA, and I think USSR was even bigger.

Also bear in mind that the "stroke" (length that the piston moves through) of the cylinder has an effect, the radius of the circle that the connecting rod describes where it is attached to the wheel is half the length of the stroke and coupled with the diameter of the wheel this can give a very different visual effect for different locos. Later UK express locos tended to have driving wheels about 6' 6" to 6'9", but in the days of the single drivers 7' and 8' were more common. The Bristol and Exeter even had some 4-2-4T express tank locos with 9' wheels with no flanges, no coupling rods or connecting rods on view either!

Another thing to influence the appearance is the type of valve gear fitted and whether it is outside on view or hidden inside.

Robin