"Tired of dumping the air".....?

Except for heritage steam lines, many of the steamers plying the rails are modernized, to a degree. The last time I worked on it (on its way to LA for the Olympics), in addition to air modifications SP 4449 had full MU capability with a diesel consist for both air and dynamic. It did not have a conventional control stand, but a simple looking rheostat affair. With this particular engine the diesel is ready power, air supply and dynamic brake.

Some think that since there are only a couple of engines and a tool car, another support car and auxiliary tender, that dynamic isn’t that important, since there’s not a bunch of tonnage. You may have 8,000 trailing tons with a train, but if you have 100 cars, you have 100 cars of braking power. There is significant tonnage involved even in a lite-engine movement, with not a lot of air at your disposal for brakes. For that reason, dynamic brake is even more important than when handling a train. In grade territory there are strict limits on permissible tons that can be handled without dynamic brake.

Another trip 4449 broke a flue near Lathrop, Ca. Diesels right behind, they never missed a lick. I think that was the train, headed for a Super Bowl game at the Super Dome.

The flip side are UP engines I was a fireman pilot on when they came from Cheyenne to Sacramento for the grand opening of the California State Railroad Museum. 30 years ago the end of this month, actually. At the time the Northern was numbered UP 844 and the Challenger 3895. The 844 was steaming well, but the 3985 was early in movable restoration and was having some trouble with the stoker and a cylinder cock stuck open on the fireman’s side. They did not MU and had original air brake schedule, if not wrong. There was a pre-trip meeting with all involved for maneuvers. One caution was for the diesels to not push hard. Coupler alignment was an issue. The diesel engines along played their usual role, with one addition on this trip.

There was a sound recording run-by scheduled for track between Truckee and Norden on the eastern flank of the Sierras. At this point both the engines were working steam, with the diesels actually in dynamic brake so the engines could work some heavier steam on this up hill stretch without exceeding the track speed.

I gotta admit that was pretty cool. Cold morning, high altitude, lots of steam vapor and coal smoke.

This is an example of the oft misused term, double heading. It is perfectly legal, but not often used, except for in an emergency of some sort or excursion trains. Simply put, an engineer runs the lead engine and controls the train‘s air brakes. The next engine is only connected with the brake pipe, it has its own engineer, who has his brake pipe control valve cut-out, but still in control of the power, engine brake and/or dynamic brake of the loco he is on. Add a third and you are triple heading. But if all three units are operated from a single control, then they are one, multiple unit engine.

As far as moving an engine DIT, you are right. Having a blob of something as heavy as a loco in the rear ten cars makes for interesting train handling opportunities. The last one I saw was about six or eight years ago. Maybe 10 years, for the CSRM 20 year bash? Anyway, it was a vintage F7 Black Widow headed south by my house entrained in the rear cars but I didn't count. These locos not much heavier than a 138 ton car.

The problem is with older locomotives that lack alignment control blocks for coupler pockets, or modern switch engines without them serviceable. These engines are made so that they can traverse very sharp curves with a car as you would find in industrial switching operations. They do this with wider than usual coupler pockets on the engine. The blocks are heavy steel tabs on hinges. Fold them in and lock in place to narrow the pocket to standard dimensions for road operations. If these are at the head end of a train and next to the train, without that coupler control, buff forces will cause the engine to jack-knife. That’s why when you see SW1500s and others alike, you’ll see them with-in the road consist, not next to the train, running or not.

But, that original F7 never had them and never will, and won‘t MU with modern consists. So, it had to go toward the rear of the train, with the dead engine feature cut-in so it would act like a box car, as far as the air goes.

As far as assisting in charging or recharging the brake pipe from the rear of the train, unless the engine is part of a DPU consist, its air brake control valve is cut-out, which takes its compressor out of the mix.

On special trains special rules are either employed or disregarded. This is particularly true with steam movements so the crew may be told to disregard warnings from hot box detectors, for example.

The engine in the lead does the braking. If the diesel compressors help with the air load, it's because the diesels are feeding main reservoir air up to the steamer's main reservoirs to assist its air pump. The steamer's brake stand controls the entire train including the diesel, which is set in "trail" mode. Always. No braking is done elsewhere in the train, unless the steam engine is Thomas, and even the dummy Thomas's have an ability to set the brake, and there is a crewman on board (to work the eyes).

Generally you should have ONE place on the train from which the brake pipe is controlled. Injecting more air from mid-train helpers is only done on very long freight trains and it's a modern innovation that requires a lot of care in setup. There'd be no reason WHATSOEVER to use that in a steam excursion.

The diesels are there mainly as a backup plan, in case the steamer has an issue, and that happens a lot. It also assists on starting, particularly up hills, as the steamer can pull loads it can't start, and the reverse is true for the diesel. Also, I hear some roads like to use the diesel's dynamic brakes instead of friction brakes. That's pretty much standard procedure on freight trains nowadays. And the owners of those heritage coaches will thank them for the reduced brake shoe wear. Everything on a heritage coach is expensive. They ordinarily do not use the diesel to pull the train, as that would offend the people paying $100/seat for a ride behind the steamer!

The best "diesel helper" I've ever heard of was a second tender behind the steamer. It happened to have Blomberg (EMD) trucks and made a "Shrum shrum shrum" sound!! LOL!

The Federal laws are surprisingly minimal. I suspect you could get away with running a 6 or 14-EL or BL, in fact, many museums do just that. The issue is the mainline railroad companies want to see modern stuff, not least to interact with their modern diesels.

The mainline steamers are not terribly loyal to "historic original fabric". They have to replace some systems to be compatible with modern stuff.

I think you'll have to wait for Samurai again. However, I think I can tell you a couple things here. If the steam engine is in the lead (your 3rd paragraph), the Engineer still has complete control of the train brakes/ brake pipe air pressure. The diesel is handy in that its more modern air compressor can recharge the system and recover air pressure faster than the steam engine. So in a sense (I think), and in that situation, the diesel is there for the compressor advantage. But all the train handling would be done from the lead engine/steam engine.

Sometimes the owners, or the organizations, that own a steam engine don't want to work it too hard and accelerate the wear of moving parts - parts that are no longer available. (Your 2nd paragraph.) And sometimes this is why they incorporate diesel helpers. One the other hand, there are steam excursions that are intended to be truly steam, and no modern assistance is used.