THIRD CYLINDER

[snookiedoe]

I have read references to a third steam cylinder located on the trailing truck or even on the tenders trucks of some steam locomotives. Can anyone enlighten me on this as to how it worked and where, when and by which roads it was used?

Thanks, Tom

[NorthWest]

Hello Tom,

I think what you are describing is a booster engine. They typically had two small cylinders to provide starting effort before cutting out at around 30 MPH. Figure around 300 HP.  Tender boosters were usually only used for yard locomotives, while trailing truck boosters were used on various railroad's main line power, as long as it had a four wheel trailing truck.

Here is a cutaway view of one.

On roads, they were common only in North America, but I can't tell you an all inclusive list.

Hope this helps,

NW

[K4sPRR]

snookiedoe

which roads it was used

The C&O and PRR used them on a few locomotives also the CPRR, the NYC applied boosters to many of their Hudsons.  Their use was on limited number of locomotives,  those who did try them deemed them unnecessary for most of their needs. 

[henry6]

There is a huge difference between a booster and a three cylinder locomotive.  Boosters were auxiliary units which could be cut in or cut out as needed and usually found either on the trailing truck of the engine or on one or more of the trucks on the tender.  A three cylinder locomotive would have a third cylinder between the drivers of the engine to increase steam pressure to the driver's cylinders.   Booster, three cylinder, two different things entirely. 

[Tweedy]

Several months ago, someone provided a link to a manual on operation of boosters that was quite interesting.

The link showed them to be a plumbers night-mare and definately NOT very user friendly, but they worked. Quite common on SP Pacifics on the SF/San Jose run. (This was in the '40s and I was facinated but totally ignorant about their operation--but, finely, now I know)! 

 

Tweedy

[daveklepper]

Boosters:  New York Central's Hudsons all had them.   No K4 had them.   The PRR Duplexes did not have them.  The only PRR locos that had them were the "J" 2-10-4's, a slightly modified C&O design.  Most were not maintained and were removed before the J's were retired, although some did keep them to the end around 1957.

The only really succesessful 3-cylinder USA locomotives (third between the other two, under the center of the smokebox) were the UP 9000's, the 4-12-2's.   Excessive valve-gear and driving rod maintenance was normal.

[CSSHEGEWISCH]

Three-cylinder steam locomotives seemed to have the same problem as most poppet-valve equipped locomotives,  they were oddballs and suffered from a lack of proper maintenance.

I would be curious to find out the track record of the grandest 0-8-0 of all, IHB's three-cylinder U-4a's.

[Deggesty]

henry6

There is a huge difference between a booster and a three cylinder locomotive.  Boosters were auxiliary units which could be cut in or cut out as needed and usually found either on the trailing truck of the engine or on one or more of the trucks on the tender.  A three cylinder locomotive would have a third cylinder between the drivers of the engine to increase steam pressure to the driver's cylinders.   Booster, three cylinder, two different things entirely. 

Henry, I'm sorry, but I found your description to be somewhat unclear. Would it not be better to have described the third cylinder as being connected to the second driver axle (with the first driver axle having a crank in it so that the rod between the cylinder and the driven axle would clear the first axle).?

With the valve gear, along with the rod from the cylinder to its driven axle all inside, it was very difficult to reach any of the mechanism for maintenance, so three cylinder locomotives were not at all popular. Booster engines were more accessible, yet few roads had them on their engines.

[henry6]

A three cylinder locomotive has a third cylinder between the drivers of the engine taking low pressure steam and feeding the drive wheel cylinders with higher pressure steam.  A booster is just a cylinder which can be cut in and out as needed and can be located on the trailing truck of the engine or one or more of the trucks on the tender.  A three cylinder locomotive can in fact feed to a booster unit.   If you are confused by this, then go to you library and find books on steam locomotives which would have diagrams and the same explanations.

[timz]

Deggesty

the third cylinder as being connected to the second driver axle (with the first driver axle having a crank in it so that the rod between the cylinder and the driven axle would clear the first axle).?

Most 3-cyl engines in the US connected the inside cyl to the 2nd drivers-- was the MP 2-8-2 the only one that didn't? But in England the 3rd cyl sometimes drove the lead drivers.

Dunno how many US engines had bent first driver axles. Not all, it seems.

Deggesty

With the valve gear, along with the rod from the cylinder to its driven axle all inside

In the US, usually no valve gear inside.

[timz]

henry6

A three cylinder locomotive has a third cylinder between the drivers of the engine taking low pressure steam and feeding the drive wheel cylinders with higher pressure steam.

Probably the rest of you know better than to believe that. Webb compounds in England had one low-pressure cyl inside-- did anyone else's engines do that?

Was BLW 60000 the only compound 3-cyl in the US?

[Deggesty]

Here is a reference to the only type of three cylinder (other than Shays) that I had heard of. http://www.steamlocomotive.com/3cylinder/

I do not understand how you can operate a cylinder without valve gear. The article also states that the UP 4-12-2 did not have a crank in the first axle. Some others, such as the engine developed for the Southern Pacific, did.

Henry, can you cite a reference that describes how a low pressure cylinder produces high pressure steam>

[henry6]

SO you are saying I am a liar?  All of you better read some books on this topic and others pertaining to railroading before you start calling people out.  If I am wrong, cite chapter and verse that will show how and where and why.  Otherwise don't say anything.

[timz]

Deggesty

I do not understand how you can operate a cylinder without valve gear.

It has "valve gear"-- which in the US was usually the Gresley-Holcroft levers in front of the outside cylinders, on the pilot beam or whatever it's called.

[daveklepper]

Any c\ylinder has to have valves and valve gear.   ON USA three-cylinder locos the valves for the inside cylinder were generally operated by a gear motion derived from the two oustide cylinder's valve-gear, rather than directly from drivers on either side.   This was the case of the UP 4-12-2's.   I had forgotton about the Indiana Harbor Belt 0-10-2's, and they could be called successful also.   Also with derived moition for the inside valves.

[henry6]

Deggesty

Here is a reference to the only type of three cylinder (other than Shays) that I had heard of. http://www.steamlocomotive.com/3cylinder/

I do not understand how you can operate a cylinder without valve gear. The article also states that the UP 4-12-2 did not have a crank in the first axle. Some others, such as the engine developed for the Southern Pacific, did.

Henry, can you cite a reference that describes how a low pressure cylinder produces high pressure steam>

Johnny, I don't have to...just go to the library and find all the books on the subject.  If you can't do that, then don't make comments to me about what I say.  If you are too lazy to go to the library, then Google it or BIng it or search.  You--and quite a few others here--ask questions and make ignorant statements then refuse explanations and directions to information and make derogatory remarks to us.  I don't like that and others have quit these pages because of that.

[Deggesty]

henry6

SO you are saying I am a liar?  All of you better read some books on this topic and others pertaining to railroading before you start calling people out.  If I am wrong, cite chapter and verse that will show how and where and why.  Otherwise don't say anything.

Henry, I am puzzled as to how you can consider my asking for a reference is equivalent to my saying that you are not telling the truth. I simply asked for information describing the workings of a cylinder that converts low pressure steam to high pressure steam; that is my understanding of your description; did I misunderstand what you wrote? Do you know of any site on the internet that describes such? Can you please give us the names of particular books that describe this?

All the information that I have seen, my sixty-five or so years of gaining information on the operation of railroads, has never had mention of such a mechanism, and I would be glad to learn how such works.

[Deggesty]

timz

Deggesty

I do not understand how you can operate a cylinder without valve gear.

It has "valve gear"-- which in the US was usually the Gresley-Holcroft levers in front of the outside cylinders, on the pilot beam or whatever it's called.

Thanks, Timz. I did find photographs of both the SP and UP three-cylinder engines, in Michael Swift's Iron Horses (London, 2008, Compendium Publishing , Ltd.) The particular edition that I have lists Book Sales, Inc., Northfield Avenue, Edison, New Jersey, 08837 as being the source in this country.

There is one picture of an SP engine on page 164, and there are two pictures of the UP 9000, on pages 166 and 167. All three pictures show mechanism projecting from the front of the valve cylinders which, as you say, connects with the valve for the third cylinder There is no head-on view which might give more detail of the exterior workings. However, there must be mechanism beside the third cylinder to regulate the movement of the valve; would not this be considered a part of the valve gear?  Also, there needed to be some means of converting the valve motion so that the motion of the inside valve is 120 degrees out of phase with that of the two exterior valves. Was this phase differential worked out in the exterior coupling? (I do not know if the SP valves were exactly 120 degrees apart as those of the UP were).

[timz]

Deggesty

there must be mechanism beside the third cylinder to regulate the movement of the valve; would not this be considered a part of the valve gear?

The inside valve is driven by its valve stem that extends forward and is driven by the shorter of the two levers on the pilot beam. No need for anything beside the inside cylinder.

Deggesty

Was this phase differential worked out in the exterior coupling?

Was intended to be; they say the center-cyl cutoff tended to be longer than the outside cyl due to play and the levers not being perfectly rigid.

Deggesty

I do not know if the SP valves were exactly 120 degrees apart as those of the UP were

We can't expect exact, but it's a good bet the three pistons were supposed to be front-dead-center at 120-degree intervals of driver rotation, and presumably the valves likewise. Since the center cylinder was inclined 9.5 degrees on the SP and UP engines it's a good bet the inside crank was shifted 9.5 degrees from 120-120-120.

[henry6]

You have to read more books because most all railroads struggled with or tested three cylinder locomotives.  In all my 70 years it has been part of the lexicon especially in written materials.

[NorthWest]

Guys,

Before we get too far off track (and start a flame war), I'd like to repost the OP's opener (coloring mine):

snookiedoe

I have read references to a third steam cylinder located on the trailing truck or even on the tenders trucks of some steam locomotives.

Oh, and Deggesty? Here is a head on of a UP 9000.

NW

 

[henry6]

NorthWest

Guys,

Before we get too far off track (and start a flame war), I'd like to repost the OP's opener (coloring mine):

snookiedoe

I have read references to a third steam cylinder located on the trailing truck or even on the tenders trucks of some steam locomotives.

Oh, and Deggesty? Here is a head on of a UP 9000.

NW

 

And the answer begins with: do not confuse a three cylinder locomotive and boosters.  A three cylinder locomotive by defnition has a third cylinder between the drivers taking steam and increasing its pressure to the main or driving wheel cylinders of the engine.  Boosters are units on trailing trucks of engines and on one or more trucks of tenders, cylinders driving the wheels of the trucks.  Lots have been written on both in books and magazine articles.  

[ACY Tom]

OBOY!

I don't think anybody intended any insult, but this discussion has gone in two directions at once and managed to hurt some feelings in the process.  Quite an accomplishment!

The misdirection is the discussion of 3-cylinder locomotives.

These were found on IHB (0-8-0's, as discussed); UP (4-10-2's and 4-12-2's as discussed); SP (4-10-2's as discussed); MoPac (2-8-2's as discussed); DL&W (4-8-2's); D&RGW (4-8-2's); NH (0-8-0's and possibly other types); and probably a few more.

The point of the question was trailing truck boosters, which were applied to an awful lot of locos in the '20's and '30's, but usually (not always) removed during the '40's and '50's due to high maintenance costs.  On engines with a single trailing axle, they could not be installed on built-up trailing trucks like the Cole or Hodges, and required a cast (i.e. Delta) trailing truck.  Some roads therefore used tender-mounted boosters on Mikados and engines that did not have trailing trucks, most often heavy switchers  On the Akron Canton & Youngstown, Mikados 400 and 401 were delivered with Hodges trailing trucks and Franklin tender boosters.  After that, no's 402 and 403 were delivered with cast Delta trailing trucks and Franklin tender boosters to match those on the earlier engines, presumably to simplify the road's parts inventory.  In any case, the boosters were all removed from the AC&Y engines in the early 1940's.

My 1947 Locomotive Cyclopedia shows booster engines mounted on the trailing trucks of the following:

2-8-2's: SLSF

2-8-4's: C&O, B&A, L&N, NS

2-10-2's: C&IM

2-10-4's: PRR, C.P., B&LE,C&O

4-6-2's: B&M

4-6-4's: C.P., C.N., C&O, NYC

4-8-4's: C&O, C&NW, LV, SP, RDG

I am certain that this list is not complete.

  

[Semper Vaporo]

Another confusion factor in the question is that the booster engine would not be a single (3rd) cylinder engine (with a single cylinder there is a chance that it would come to a stop at TDC or BDC [Top or Bottom Dead Center] and thus be useless for power since it would not be able to determine which direction to turn when steam is applied).  The booster engines had two cylinders at quadrature (90° to each other) so that if one was at TDC or BDC the other would be in the middle of the power stroke for the desired direction.

On the other hand... the valve gear for a 3rd (center) cylinder in the front (main) engine on the locomotive was often derived by a system of levers that combined the angles of the other two valve levers (called a "Conjugated Valve Gear") invented by Sir Nigel Gressley.  Some had a 3rd valve gear arrangement.  It might even be of a totally different type, such as having Walshaerts for the two outside cylinders and Stevenson's for the center cylinder.

On some engines the 3rd (center) cylinder was mounted higher and angled downward and the rotational spacing of the crank  pins was thus set to 120°/113°/127° instead of 120°/120°/120°.  Other arrangements sometimes had the center cylinder at 135° and produced a pronounced unequal exhaust beat.

 

As for the pressures in the cylinders...

Some engines had equal size cylinders and ran boiler pressure to all the cylinders... a "simple" engine.  This produced 6 exhaust beats per revolution of the drivers.

On a "Compound" engine, the outside cylinders were fed steam directly from the boiler and were thus considered high pressure cylinders.  The exhaust from them were fed to the 3rd (center) and larger cylinder which was the considered the low pressure cylinder.  The exhaust from that cylinder was then sent up the stack to create the draft for the fire.  This produced only 2 exhaust beats per revolution of the drivers.

Some engines did it the other way around.  The center cylinder was the smaller of the three and was fed from boiler pressure and was thus the high pressure cylinder.  It exhausted to the other two (outside) larger cylinders which were thus the low pressure cylinders and they exhausted to the stack (for draft).  This produced only 4 exhaust beats per revolution of the drivers but somewhat unequal in timing.

Discussion of the Shay engine is outside of the OPs original question, but had 3 sizes of cylinders in an arrangement called Triple Compounding.. The smallest one was the high pressure cylinder fed directly from the boiler.  It exhausted to the medium sized cylinder (mid pressure) and its exhaust fed the larger size cylinder (low pressure).

 

 

 

 

[timz]

Semper Vaporo

Other arrangements sometimes had the center cylinder at 135° and produced a pronounced unequal exhaust beat.

Three-cyl compounds (with one high-pressure and two low-pressure cylinders) would likely do that-- BLW 60000 did. Why would a simple 3-cyl do that? What would be the point?

[Semper Vaporo]

There were two basic reasons to have to mount the center (3rd) cylinder at an angle. 

One is because there just was not room for it to fit between the other two cylinders and the associated valve gear all in a line and have the frame members of sufficient size for rigidity.  The cylinder was often cast as part of the frame itself.

The other was the need to connect the drive rod to the 2nd drivers with a sufficient strength drive rod and yet not have too large an offset crank in the number 1 axle to clear the center cylinder drive rod.

I used to have an animation of a cutaway of the setup and it was fascinating to watch the crank in the 1st axle barely miss the drive rod to the 2nd axle.... Mighty close tolerances.

[efftenxrfe]

Back there in this in this post(age) there was a how can you get high pressure (I think that meant power) out of low(er)  steam pressure cylinder?

W/O getting algebraic, say the boiler feeds 300 pounds per square inch into a cylinder which makes a piston move. At the end of movement, the pressure is 200 psi, a lot of energy left.

At that moment, the steam against the piston head originally produced power to the drivers, let the drivers roll!

Using the steam again to get the same amount of power for the same (or other, compound articulateds) to the engine's driving wheel says to the logic god that 200 psi needs a third more cylinder surface to get the same psi against the piston head that 300 psi needs on a primary cylinder.

Many air brake valve functions relied on a greater area with low pressure working against smaller areas of higher air pressure. the differential of psi times area made things happen.

[KCSfan]

I just realized how little I know about booster operation so my questions may seem very elementary to some of you who are far more knowledgeable than me.

1. I assume there was a separate throttle for the booster engine. Was it either a wide open or fully closed valve or was it possible to control the amount of steam supplied to the booster cylinder(s)?

2. I believe there was an automatic cutoff device that functioned when the booster's top operating speed was reached. How was this actuated?

3. What about the possibility of wheel slippage? Was the booster engine powerful enough to cause the powered trailing truck or tender wheels to slip?

4. An earlier reply contains a link to a cutaway view that shows a pinion gear that I assume is mounted on a crankshaft and engages a gear on the axle of the trailing or tender wheels. Was this arrangement common to all boosters?

5. The same cutaway view shows two cylinders. Was this typical of all boosters or did some have only  a single cylinder?

6. How was the booster engine mechanism lubricated?

Thanks for your help in gaining a better understanding this subject.

Mark

[timz]

Baron Vuillet's account of a ride on a T&P 2-10-4 mentions the engineer letting the booster warm up with a bit of steam before they reached the foot of the hill and cut the booster in.

The booster crankshaft had a gear, and the axle had a gear; when the booster is cut in a third idler gear moves into mesh with the other two gears.

[Overmod]

KCSfan

I just realized how little I know about booster operation so my questions may seem very elementary to some of you who are far more knowledgeable than me.

1. I assume there was a separate throttle for the booster engine. Was it either a wide open or fully closed valve or was it possible to control the amount of steam supplied to the booster cylinder(s)?

2. I believe there was an automatic cutoff device that functioned when the booster's top operating speed was reached. How was this actuated?

3. What about the possibility of wheel slippage? Was the booster engine powerful enough to cause the powered trailing truck or tender wheels to slip?

4. An earlier reply contains a link to a cutaway view that shows a pinion gear that I assume is mounted on a crankshaft and engages a gear on the axle of the trailing or tender wheels. Was this arrangement common to all boosters?

5. The same cutaway view shows two cylinders. Was this typical of all boosters or did some have only  a single cylinder?

6. How was the booster engine mechanism lubricated?

Thanks for your help in gaining a better understanding this subject.

Mark

Many of the answers you want can be found here.  This is an instruction manual for the Franklin booster models C1 and C2.  There were subsequent improvements allowing the Franklin booster to run at higher speed, and to be reversible.

I'm not aware of a posted copy for the Bethlehem Auxiliary Locomotive (the tender booster) but here is an eBay link to a copy if you want one.

In rough order:

1) The Franklin booster was arranged to require minimal tinkering: all the operations were controlled sequentially with air logic.  The arrengement was set so that power would be proportional to cylinder thrust at a given throttle opening.

2) Interestingly enough, there does not appear to be an automatic overspeed trip (although designing one with some kind of speed-governor arrangement would be trivial).   Note that because of the way the booster is constructed, if you have power on the booster the gears will be held in engagement, so overrunning the booster engine would cause the intermediate gear to try to lift, at which point (presumably) the spring preload would disengage the idler carriage fully.  Note also that the "clutch" engagement cylinder only acts long enough to get the gears to lock in, after which only the gear engagement force keeps the gears engaged.

3) Slip management is covered in the manual.  Yes, it would slip, and if properly adjusted would slip about the same time as the drivers would.  Since it did not have separate sanding lines, enginemen were instructed to lay down sand under the booster's axle if a slip were anticipated at starting.  A cautionary note: rail washing arrangements should act after the booster axle, not immediately at the rear of the coupled wheelbase...

There was a slip-control arrangement (which was essentially a sprung push valve that when engaged reduced steam pressure from the main throttle temporarily, until the slip stopped).  There is also reference to exhaust check valves, which would presumably act if excessive exhaust steam were present (the sign of a slip!)

4).  It's probably the best arrangement.  I'm not aware of a successful version with 'direct drive' (as, for the same reasons that apply to 'reverse turbines', the mechanical losses for a system constantly in engagement, and the consequences of any of a wide range of potential mechanical failures, would be needless complications.

Note however that Livio Dante Porta favored adoption of Peter Lewty's system, which uses an efficient multiple-expansion engine, located close to the superheater header, driving a hydraulic pump; the motors on the auxiliaries, including the booster, are then some appropriate form of hydraulic motor (such as a vane motor) and it is possible that these could be permanently keyed or constant-mesh geared to the shaft(s) they drive.

5)The booster motor would not be self-starting with only one cylinder; remember that it is "very important"  (emphasis theirs) to idle the booster before using it, and if it were to stick on a dead center things would not be good.  In addition, the torque peaks from only one cylinder would be much more prone to induce slipping for a given developed wheelrim torque, at reasonable valve operating and piston speeds.

There would be comparatively little gain *on the trailing truck* for a three-cylinder booster engine (the center cylinder and throw would be right where the pinion ought to be; you could offset it, but you'd have uneven thrust; you could double up on piniona and driven gears, but 'the prices go up up up".  Four cylinders (or more) might be practical with something like the Besler arrangement used on the B&) W-1 motor locomotive, but all the complication and first cost of providing a multiple-cylinder arrangement and then keeping it adjusted and maintained is out of proportion to what a booster on a typical reciprocating locomotive would require.  The cost of boosters was already high enough that some railroads (including the LNER in England), despite finding the things very useful in train-running, could not justify their acquisition and use for general service.

6) I note that the instruction manual called for hydrostatic "drip" feeding -- not less than 2 drops/min where the booster was to be used.  One implication here is that the booster lubrication can be monitored from the cab, which indicates that the lubricator itself has flexible or jointed feed lines to the booster engine bed on the trailing truck.

On a modern locomotive the booster lube feeds would be provided via taps on the mechanical lubricator.  I do not know what the 'best' range of supply pressure would be.  A full modern system would be pressure-lubricated with 'closed loop' return lines and minimized loss.