Steam Engine Boosters

Trains Magazine General Discussion
1

I have several books on locomotives but have yet to see any detail about booster engines. The most specific description I’ve seen is in the Drury book (“Guide to N. Amer. Steam Locomotives”), and that was only a couple of sentences.

  • Every picture I’ve seen of a locomotive with a booster engine has the exhaust just behind the main stack. What was the reason for going to the trouble of running it all the way back to the front-top of the engine? I can see that exhausting out the side or bottom might be an unpleasant experience to bystanders. Were boosters so loud such that it would have been a major nuisance to locate the exhaust above the engine cab? One possibility, for example, might have been to route it back into the boiler to aid the draft. How about exhaust from a tender booster – where was that usually located?
  • What was the booster drive mechanism: pistons through a drive shaft? Directly linked to the wheels? What types of valve mechanisms were used?
  • I notice that many of the later engines entirely dispensed with boosters. Was that because modern designs had enough starting TE or had boosters gotten a reputation as a headache? I guess the engineer had to remember to shut it down when his train attained speed. I take it that few if any restored locomotives have operable boosters.

Thanks for the input!

2

The tender booster exhaust was behind the coal bunker. To see some neat shots of one in action, check out “Lehigh & New England”, by John Krause and available from RMC [sorry, Trains] In that book there is a sequence of shots with an LNE 2-10-0 hauling coal up a twisting, steep hill with his booster cut in. With a speed of about 7mph, you can almost hear the roar almost 60 years after the fact.

BTW, no less an important foobar than Leonor F. Loree [PRR;D&H] was a business partner in marketing and producing boosters; later they sold out to Bethlehem, who made them to the end of steam.

Also BTW, the LNE’s decs were knock-offs of WM’s, which were the largest as built. But with the Wooten fire box and tender boosters, the LNE decs were the heaviest in the World.

3

In answer to your other comment, I don’t think any engineer would likely forget to cut it out; a booster was only good for low-speed lugging, and the ashcat would quickly remind him to cut it out to ease his own work load.

4

You answered your own question as to why the booster’s exhaust was routed back to the front and into the smoke box, to aid draft.

5

The L&NE booster is atypical, for fairly obvious reasons – it’s on the tender. (There’s no place on a Decapod for a conventional one, obviously, and the roads that used tender boosters certainly found their low-speed torque useful in running trains. I can’t say as much for the Southern’s attempts with motor tenders!)

There are some pretty good pictures of boosters on the Web – the basic technology tried to keep up with that of primary steam-locomotive tech and almost did, but you keep seeing swaps back and forth between booster and no booster, with the ‘last grand hurrah’ of American steam essentially ignoring them.

The late form of booster is a small steam engine, with multiple pistons (so it’s self-starting), usually running through a geared transmission to the rear axle of the trailing truck (the ‘only’ axle on a two-wheel trailer). One of the intermediate gears could be thrown in and out of engagement; with this out, the axle could presumably freewheel without the drag and overspeeding of booster parts.

The principal advantage, of course, was that boosters could use boiler steam at low main engine rpm, to produce very high starting TE, and convert idling axles into loaded, powered ones (increasing both TE and effective factor of adhesion), then allow the main engine to start developing power when the number of pulses per minute became high enough that surging, slipping, etc. were less of an issue. Theoretically this allowed the use of higher drivers than would otherwise have to be installed (note that better engine balance practice in the '40s is a piece of why boosters went out of favor then)

Disadvantages were fairly many, starting with the fact that you had lots of tiny little pieces, difficult to enclose, hanging out at the back of the engine where cinders, heat, road dirt, blowdown, tender water, etc. etc. etc. could get at them. You needed flexible connections for both supply and exhaust steam, which needed to be insulated, etc. The effective

6

Some of the pictures that I have (such as the J1-e to J3 NYC Hudsons) show a separate stack for the booster, seemingly spaced too far away from the main stack to have much of an effect on draft.

7

C&O 4-8-4 614 has a trailing truck booster. I rode the engine on one of the “ACE 3000” trips and engineer Steve Wickersham used it in starting the train.

It didn’t make a great deal of noise in the cab, and did not begin to be a drain on the steam-producing capabilities of the boiler, because Wickersham was able to accelerate the train quickly with it and cut it out appropriately. Which was its intended use.

I have some video of the 614 lugging some heavy excursion trains on the steep grades on the B&O at low speed, but can’t recall if the booster was in use at the time.

Old Timer

8

The 4449 has a trailing truck booster, but it has never been used beyond its original service on the SP.

9

CPR # 2860 also has a truck booster - we are having a main steam pipe made for it , the origional had to go back to #2850 in the museum . Not sure when it was last used - looks in good condition.