SP Cab Forwards - an idea not that widely used[?]

[espeefoamer]

QUOTE: Originally posted by eastside

1. Cab forwards would have required switching to oil firing
2. For crash survivability, many engineers wanted all that iron in front them, not behind. Witness the insistence of some railroads up until recently to order road diesels with the cab in the rear

I also heard that the SP CFs were limited to low speeds. I'm not certain if that was characteristic of CF designs in general or only in this particular case.

I always found it quite interesting, that the two railroads (Southern & N&W) that bought high hood diesels,also ran them long hood forward.They ordered high hoods for crew safety,then ran them long hood forward for the same reason.

[Modelcar]

...In theory I suppose that could be a factor...but I'm sure the fireman had to keep the crown sheet covered above the firebox or the boiler wouldn't have stayed in assembled condition very long. Don't know what kind of compensation was made [if one was needed], to make sure all that area was water covered in an up hill attitude. I would think it would have been a critical factor but maybe the grades they operated on didn't make that much difference in keeping the water level above all the critical parts.

[WDGF]

I recall reading somewhere that there was also some trouble keeping them steamed properly on grades. With a normal locomotive, the water in the boiler is highest over the firebox when going uphill, where with the CFs, the water is lowest over the firebox going uphill.

[Modelcar]

....In the basic question of cab forward designs...that of safety, I consider the fact all large railroad engines are large in size including their height...I realize it would be a nasty experience to be an engineer in one of the SP units back then and see a non preventable accident looming ahead....With exception of hitting a fuel tanker of some kind, wouldn't the engineer [and fireman], still have a good chance of survival being up high off the rails and of course massive steel structure underneath and right in front of them....

[CSSHEGEWISCH]

According to Dan Ranger's article about cab-forwards in TRAINS in about 1968, Western Pacific also considered a cab-forward design but it was voted down in a poll of engineers in the operating district in which they would have been used.

The same article includes a photo of a cab-forward on the "Overland Limited" at Dutch Flat, CA, with a 2-8-0 as a helper.

Kozzie, it's interesting that you would bring up the cab-forward question when you consider the cab-forward design of the latest Australian diesels compared to the North American designs with which I'm familiar.

Paul

[M636C]

Apart from Southern Pacific, I believe, in the USA only one short line ever built a cab forward, and it was a strange 4-4-0.

The Italian State Railways, Ferrovie della Stata, (FS) had some coal burning four cylinder compound 4-6-0 locomotives which were cab forwards, and had coal carried in a bunker above and around the firebox. The shape of the cab front was a sharp vee, even sharper than the later SP AC-9 to AC-11. The bogie was under the cab and firebox, and the four cylinders were reasonably accessible all at the back end under the smokebox. My memory is that they were class 670 locomotives in the FS system. These were high speed (for the day) passenger engines. One was rebuilt in the 1920s with a Crosti feedwater heater on the tender, and was fully streamlined, retaining the pointed cab.

The FS also had four cylinder compound 0-10-0s which had bunkers around the firebox and very small water tanks. They were used as pusher locomotives in the Alps, and ran with a six wheeled auxiliary tender with a cylindrical tank! This allowed them to uncouple from the tender, so that the engine was always leading, whether cab or boiler was leading. At least some of these were rebuilt as conventional 0-10-0s with normal tenders carrying both water and coal at the cab end.

The German State Railways, Deutsche Reichsbahn Gesellschaft (DRG) ordered a cab forward version of the 05 4-6-4 (the real world steam record holder- remember the "Mallard" was unserviceable after its run downhill in which it beat the 05, running on the level, by only ONE mph) in 1935. This loco, 05 003 used pulverised coal which was blown by compressed air up a tube under the boiler and directly into a burner in the throatplate of the firebox. It too was fully streamlined, with a curved cab reminiscent of the E18 and E19 electric locomotives and the later "Flying Hamburger" diesel electric railcars. It didn't actually enter service, and was rebuilt as a non streamlined version of the other 05s in the early 1940s. Liliput make a model, but not (so far) in cab forward form (that I know of).

So while Southern Pacific had the best known "Cab Forwards", they weren't the first nor were they the fastest, but they were the last in service.

Peter

[eastside]

I've never seen any serious statistics in support of rear-end cabs. I agree it seems mostly psychological when it came to cab forwards. The engineers must have been uncomfortable with the imagery going through their minds. It must have been something like that they're the nut between the hammer (the locomotive or whatever else is coming at them) and the anvil (their locomotive), conveniently ignoring the many thousands of tons of the following consist [:)]. My hunch would be that the benefits of better visibility of front-end cabs outweighed the potential increased survivability of rear-end cabs, but that's easy to say in hindsight after decades of experience with mostly front-end cab diesels.

[Modelcar]

...I understand about the long hoods forward for safety, etc....and the C F's but as some engineers stated...long part of the steam engine forward made them feel safer...but what about a hard hit with a steamer....Wouldn't that have put them in much danger with all the coal slamming forward from the tender....? And worse yet the tender being mashed right into the back of the engine cab, etc....Often wondered about all of this...I'm talking about a hard hit to brake metal, etc...

[Anonymous]

QUOTE: 2. For crash survivability, many engineers wanted all that iron in front them, not behind. Witness the insistence of some railroads up until recently to order road diesels with the cab in the rear

That was one of the things that I could never understand....

Why would the engineers run their diesels long hood forward......why why why.....

And as you said it turned out to be because of safety reasons, it makes sense to me.

Apparently there were a lot of RTEs complaining when the newer diesels started arriving that could really only be operated in the one direction with the cab up front.

[Kozzie]

[tup] Thanks very much Ed and eastside [;)]

Very interesting stuff.

Since it was what one could call a 'line requirement, they could have hauled passenger as well as freight?

Dave

[eastside]

1. Cab forwards would have required switching to oil firing
2. For crash survivability, many engineers wanted all that iron in front them, not behind. Witness the insistence of some railroads up until recently to order road diesels with the cab in the rear

I also heard that the SP CFs were limited to low speeds. I'm not certain if that was characteristic of CF designs in general or only in this particular case.

[edblysard]

Exclusivly a SP design, due to the smoke inside tunnels and snow sheds, of which SP had many.

Due to the nature and location of the tunnels on the SP, proper venting was not the rule, so putting the cab up was the easiest(cheapest) solution.

Other railroads had tunnels, of course, but also had the ability to use power venting, fresh air blowers ect...

The need for the design became moot with the advent of the FT and the GP diesel, but they lasted for quite some time, there are several photos of the SP fleet, mixed first generation diesels and AC Cabforwards in the tie up and fuel racks, side by side.

An informed source has provided 1910 as the beginning of the cabforward use on the SP, with a MC-1 Mallet Consolidation as the first cabforward.


Ed

[Kozzie]

After looking at pictures of those SP cab forwards, I've ended up with another Kozzie Question. [:I] [;)] [:)]

Was the cab forward design used by a lot of other RRs? Haven't seen many images of that principle being used extensively across other RRs.

Maybe the design, although possibly a good idea, was over taken by the advent of the diesel loco? hmmmmm....

What's the thoughts from the Forum Folk? [;)] [;)] [;)]

Dave [:)]