how do long wheelbased steamlocos such as 4-8-4 handle tight curves. It would seem that if the track gauge were increased, shorter engines would slip through between the rails.
There are a few options. Some locomotive drivers may be flangeless or equipped with lateral motion devices to handle tight curves. The locomotive may also be restricted from a tight curve by the special instructions in the employee timetable.
Nuts2URKCUHV how do long wheelbased steamlocos such as 4-8-4 handle tight curves. It would seem that if the track gauge were increased, shorter engines would slip through between the rails.
Not well - just like 6 axle diesels. TTSI will indicate track(s) that various classes of engines are not permitted to operate on. Gauge must remain constant (within the allowed tolerances) for all equipment.
Never too old to have a happy childhood!
Steam locomotives and 6 axle diesels have curve restrictions, just like model railroads do. They also have weight restrictions and minimum rail size (the size of the rail itself, since heavier rail can carry more weight.) If you look at railroad employee timetables you will sometimes find certain locomotive classes restricted from certain lines due to size / weight restrictions. Of course, if you look at an Erie or Erie Lackawanna employee timetables you would see Alco diesels restricted from entering the Nabisco warehouse in Fair Lawn due to excess smoke that would gas out the workers in the warehouse!
Some long wheelbase steam locomotives have flangless center driver tires. Some have lateral motion bearings on the front and rear drivers. And some had both.
This is one reason why we don't see big locomotives (Big Boy, Challenger) much on eastern railroads. Those locomotives were built to run out in the wide open spaces. Sure, they have run in the eastern US, and there's one at Steamtown, but I'm sure there was plenty of special handling involved.
I'd bet there were plenty of restrictions on the articulated locos that did run in the east.
I believe Carl has referred to them as "switch straighteners..."
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
DS4-4-1000 Some long wheelbase steam locomotives have flangless center driver tires. Some have lateral motion bearings on the front and rear drivers. And some had both.
Johnny
Deggesty DS4-4-1000 Some long wheelbase steam locomotives have flangless center driver tires. Some have lateral motion bearings on the front and rear drivers. And some had both. Actually, it was the center driver wheels that had no flanges--and some called them "blind drivers." Even then, there was a limit as to the sharpness of the curves--it was possible for a driver to slip entirely off the rail if the curve was too sharp, and that would present a rather bothersome situation.
Actually, it was the center driver wheels that had no flanges--and some called them "blind drivers." Even then, there was a limit as to the sharpness of the curves--it was possible for a driver to slip entirely off the rail if the curve was too sharp, and that would present a rather bothersome situation.
Which is what I said !!! Flangeless tires on the center drivers and/or lateral devices on the front and rear drivers.
Suppose we are designing a 4-8-4 and decide to make some of the driving axles flangeless. I know in practice designers would select driving axles 2 and 3 to be blind. However, if the purpose is to enable the engine to take tighter curves, why wouldn't drivers 1 and 4 be the blind ones, thus minimizing the distance between the flanged axles?
If the answer is a concern that axles 1 or 4 would be completely off the rail in the curve, then isn't the curve so tight that it could not be negotiated with flanges on the 1st and 4th axles?
Having flanges on the #1 and #4 driver axles will significantly reduce side to side oscillations compared to having blind wheels on #1 and #4 owing to the longer effective wheelbase of the flanges. (we are talking horizontal motion only) If you still want the center drivers to be flanged but the curves are too tight then you could install the lateral movement devices on the #1 and #4 drivers. Since a 4-8-4 would be a higher speed locomotive you will need dampening devices on the #1 and #4 axles to reduce oscillations but still allow horizontal movement.
DS4-4-1000 Deggesty DS4-4-1000 Some long wheelbase steam locomotives have flangless center driver tires. Some have lateral motion bearings on the front and rear drivers. And some had both. Actually, it was the center driver wheels that had no flanges--and some called them "blind drivers." Even then, there was a limit as to the sharpness of the curves--it was possible for a driver to slip entirely off the rail if the curve was too sharp, and that would present a rather bothersome situation. Which is what I said !!! Flangeless tires on the center drivers and/or lateral devices on the front and rear drivers.
No, the tires include the flanges. Both wear. The reason for the tires is so the large and expensive casting that makes up the driving wheel centre does not have to be replaced.
I believe in some sharp curves the track gauge was intentionally increased slightly where long wheelbase steam locomotives were operated. The amount of lateral play in the axle boxes was also adjustable. Additional slack could be arranged for special moves.
John
Some railroads placed rails to the inside of curves so that the blind drivers could slip on to them and still provide traction.
pajrrSteam locomotives and 6 axle diesels have curve restrictions
Reading steam
I had read that the 1976 American Freedom Train used a Reading locomotive on the east coast because of the tighter curves.
greg - Philadelphia & Reading / Reading
The Reading T-1 is overall a smaller locomotive than the SP GS-4. The tighter curves were only part of it.
Long wheel based steamers tended to make straight curve rails. Each RR defines the restrictions for curve and (turnouts?) allowed per class of locomotive. On the following link, UP 9000 does her best to prove the point. A once in time moment making you wish you were track side.
https://www.pinterest.com/pin/345088390177697632/
For what it's worth, here's another perspective. I don't intend to deny the dynamics involved in getting a rigid wheelbase around a curve, but the problem was addressed with lateral motion devices, and it worked to a certain degree. In the 1960's, I recall talking to some NKP guys at Mogadore, Ohio, who talked about the squealing flanges of their SD9 local freight engine as it negotiated the sharply curved wye at the AC&Y interchange. They said they never had that problem with the W&LE class K-1 2-8-4's, or the NKP class S and S-1 2-8-4's that came to the line shortly before the SD's.
Tom
There were big (long-wheelbase, high drivers) locos in the East. The NYC 6000 class had 79 inch drivers - and rolled them at high speed.
Actually, PRR tightened the gauge 1/4 inch on long tangents, to minimize side-to-side action of long locos with big pistons.
From what I have read, the Russian 4-14-4 was the all-time curve straightener and turnout wrecker. That in spite of lateral motion devices on four driver axles.
For some latter day steam locos the drivers weren't the big problem. They had Commonwealth tender frames with five axles rigidly mounted in pedestals.
Fun, isn't it?
Chuck
seppburgh2 Long wheel based steamers tended to make straight curve rails. Each RR defines the restrictions for curve and (turnouts?) allowed per class of locomotive. On the following link, UP 9000 does her best to prove the point. A once in time moment making you wish you were track side. https://www.pinterest.com/pin/345088390177697632/
As seppburgh2 points out AN EXCEPTION to the operations by a major railroad to a straight framed 12 coupled engine was the UPR's 9000 'Union Pacific' class steamers. started in the middle 1920 and by the end of the 1930's there were approximately 90(?) roaming the UP rails.
The 9000's were odd not only because they were 4-12-2's but they were also 3 cylinder powered. They used a 3rd cylinder drive that was designed by the English locomotve designer Nigel Gresley. Apparently there were problematic maintenance issues and towards the end some were converted to a different valve gear system. [Baldwin Locomotive Works built the #60000, a 4-10-2- using the three cylinder system on their locomotive, as well.]
AS to the issue of the use of 'Blind Drivers' ALCO provided the UPs with an ability to have its drivers move from side to side, a couple of inches using a mechanism of 'lateral motion devices'.
And then there was the Russian Steam Locomotive which was 4-14-4, possibly, built in response to the Union Pacific's 9000 class. It [an AA20-1] was the largest ridgid frame engine in the world, until the PRR built the S-1 in about 1937(?). [The AA20 was an experiment that was nowhere nearly, as successful as the 9000's or the PRR S-1.]
cx500[snipped - PDN] . . . I believe in some sharp curves the track gauge was intentionally increased slightly where long wheelbase steam locomotives were operated. . . .
- Paul North.
In most cases, mainline curves are not a problem with steam engine drivers. The engines can take the curves fine. The problem on the east coast is the clearance around curves. A big articulated engine has a lot of overhang.
I have run a DD40X around a loop at a coal fired power plant, which are tighter than most main track curves. It made the curves OK, the only limitation was it (and the dome cars in the consist) wouldn't fit through the dumper.
The curvature issues were mostly off the main track in yards where there would be tighter radii and sharp turnouts on switches down to #7 or #8 .
Dave H. Painted side goes up. My website : wnbranch.com
Agree with PDN (not quite so much with GregC)...the issue wasn't so much with the main tracks as it was the backtracks. No main track was as sharp as the curves listed in that Reading steam chart. (for that matter, anything to this day over 12d-30' is a no-no requiring a ChE to sign off on it.) First and second generation diesels rarely can track curves over 23 degrees on their own and won't couple into anything. The current generation locomotives (esp. passenger loco's) with limited or restricted drawbar swing get in trouble at seventeen degrees of curvature.[They really hate anything sharper than a No. 8 turnout) Radial trucks help with the angle of attack, but....wheels want to climb and the operating bubbas don't want to see grease sneaking up on top of the rail above the gage corner.
ACY...who talked about the squealing flanges of their SD9 local freight engine as it negotiated the sharply curved wye at the AC&Y interchange.
Squealing isn't all flanges - in fact, it may not be flanges at all.
Remember why there's a differential on an automobile. There is no differential on railroad equipment. On a dry day, our passenger cars will squeal around our ~5 degree curves. One wheel or the other has to slip, and when it does, it may well squeal.
If I'm engineer that day, I'm glad to hear the squealing - it means the rail is dry and the likelihood of slipping is next to nil.
tree68 If I'm engineer that day, I'm glad to hear the squealing - it means the rail is dry and the likelihood of slipping is next to nil.
mudchicken...and all those shiny flakes are telling you that 105# dry rail is getting curve-worn and on its way to an earlier replacement ($$$)along with a trip to the lathe for the geared axle driving wheels...
Probably isn't doing the coach wheels much good either...
Anyone who's been at Deshler when coil cars are running the SW transfer knows some real squealing....
tree68Remember why there's a differential on an automobile. There is no differential on railroad equipment. On a dry day, our passenger cars will squeal around our ~5 degree curves. One wheel or the other has to slip, and when it does, it may well squeal.
That is why the wheels are tapered. Inertia will push the outside wheels to a larger diameter part of the wheel and the inside wheels to a smaller diameter portion of the wheel. The wheels do not slip unless the curve is very sharp. The taper also keeps the axles centered on the tangents. Any tendency to go one way or the other will be automatically corrected by the difference in diameter from the taper on the wheels.
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