Diamond Speed

[agentatascadero]

Very informative discussion, I especially appreciate Mr. Hemphil's time and effort to share his knowledge. But, for me, it took me back to my early train riding days (40's-50's), on passes we rode the secondary(heavyweight) trains. I always favored the sound, not to mention the ride, of 6 wheel trucks through diamonds, interlockings, and just clickity-clacking down the jointed railroad.

[Anonymous]

Hey Mark, you can have my CORA!!! It weighs about 10 lbs and it's getting old carrying it in my grip. No, but seriously if i ever go on a foreign route it comes in very, very handy!!!

[Anonymous]

QUOTE: Originally posted by M.W. Hemphill

Umm ...

From UP829's description, he's looking at an absolute protecting the entrance to a control point.

Some notes: In this territory, these absolutes are controlled (by the dispatcher). A signal with a number plate is an automatic signal; it is never controlled. An absolute might be controlled, but there are lots of uncontrolled absolutes -- such as at a manual interlocking, or the leaving signal off a spur onto a controlled track. Absolute means you cannot pass it when it's red without verbal authorization from a dispatcher or control operator. A red intermediate is a "stop and proceed at restricted speed." Absolute signals authorize main track occupancy. Intermediate signals do not. Both advise of track conditions ahead.

Apparently these are not approach-lit signals, if they're lighting before the approaching train hits the previous block.

Thanks for all the answers - this stuff sure gets complicated.

I'm in the far western suburbs where just about every station has crossovers on both sides for the commuter trains that run express down the middle track, then cross over and make one or two station stops. That may be why I'm seeing so many absolutes. The one's I'm thinking of are all multiple head signals. When they go straight from red to green, a train will come within 5 to 10 minutes, but the train may be Empire Builder doing 70, so it was 5+ miles down the line when the signal changed. Next time I'm out I'll have to look for some intermediates and watch how they work.

Also I have noticed the U.P. racetrack has a lot fewer signals. I kind of assumed they have gone to cab signalling or ???? This part of the BN has been CTC for a long time. I remember seeing the old CTC office in one of the Cicero yard buildings way back in the mid 60s.

and 829 is a 2nd series alco U.P. Northern [:)]

[Anonymous]

Being a part-time railfan and a full-time conductor I have had the opportunity to run on CTC territory, ABS territory, and DTC territory. I have also gone across "manual interlockings and automatic interlockings. The CSX-NS diamond in Danville, IL has a speed cap of 20mph on it, but then the angle is probably about 55 degrees and there's a welding crew out there at least once a week!! Then on the 90 degree diamonds the speed cap is 40mph. Four of the interlockings I go across are controlled by the dispacher and two are automatic. The two automatic ones have the lightest amount of cross-traffic on them and I have only had to stop at one a single time in the past six months. The Dolton Interlocking in Chicago still has a tower in use and I have actually met one of the operators while I was wye'ing my power because of an engine failure. Of course, even Dolton will soon become remotely controlled, but that will be one HUGE PROJECT!!!!

[Anonymous]

Our definition of a "Distant Signal" is the automatic signal on either side of an interlocking.

[CShaveRR]

Yeah, you're right (can you tell that I don't work on the road?).

The latest issue of the CORA Operating Guide does a lot of referring to "distance" signals, when I think they should be "distant" signals. I thought at first that it was just my home railroad, but noticed it when looking at BNSF's section, too. They needed an editor!

[CShaveRR]

UP829 (are you a 4-8-4, a GP30, or a yard SD38-2?),

I suspect that on the Racetrack there is some sort of "neutral" setting for the signals that is not disturbed unless a train is coming. As an example, take the signal west of LaGrange for westbound trains. It has a single head for each track, so it's definitely an intermediate signal. If there's absolutely nothing in the area, all three tracks will show a flashing yellow (and they flash at exactly the same time, which is neat!). If one of those lights is red, I would suspect that a train is either in the block ahead of it (and I could probably see it!), or that the dispatcher had lined up the route for a train coming toward me.

If one of the lights is green, I'd turn around and look for a headlight. It might be a long way off, but yes, the dispatcher has lined it up. The train will go through, the signal will go red, then yellow, then flashing yellow. It won't go green until (s)he lines up another train.

(An aside to Nora, who wasn't familiar with searchlight signals when she came through this summer: this is the place to be if you want to see searchlight signals in action! But act quickly, as some of them are being replaced.)

I would submit that wherever you are on the Racetrack, if your signal is going through the four-aspect cycle, the dispatcher is allowing trains to follow. If it stays red, you're either at an absolute signal, or (s)he's planning a move in the opposite direction. If it stays yellow, you're at a distant signal; if it stays flashing yellow you're at the signal in advance of a distant signal.

(I'm just a short distance to your north, and our three-track raceway [yeah, right!] doesn't have any signals to worry about, except for distant and home signals at the interlockings, which are 'way too few and far between. They work in much the same way, though...the distant signal will stay at Approach until the dispatcher has cleared the route through the interlocking beyond, or done the same for a train coming toward you --in which case it will drop to Stop-and-proceed).

These statements are based purely on observation--someone with dispatching experience may choose to concur, clarify, or rebut.

[Anonymous]

QUOTE: Originally posted by M.W. Hemphill

I'd need to know the exact sequence and where the train is at the same time. Is the signal you're looking at an absolute or an intermediate? Intermediates have number plates on them, and are not controlled, but automatic only.

For an absolute, after the train is past, if the signal reverts to a red aspect and stays that way even after the train has passed several more block signals, then the dispatcher has lined up no following movement -- or has lined up an opposing movement on the same track. If it progresses from red to more favorable aspects, then the dispatcher has lined up a following movement.

Guess I'll have to go out and look for some intermediates[:)] These are most likely absolute as the blocks beyond them have high speed crossovers between the center and outer tracks. They operate as you described, except it seems the operator is able to set them up for multiple following movements. I've seen as many as 4 trains go through with the signals cycling as described. This is typical when they're trying to get a lot of freights through just before the evening rush hour.

[ValleyX]

Yes, reduce throttle to no more than power notch four no less than eight seconds before crossing diamond.

[mvlandsw]

QUOTE: Originally posted by tree68

Seems like I recall reading once that on DE locos it was necessary to throttle down when crossing a diamond. The purpose was to minimize the possibility of arcing of the traction motors. Still true?

Still required on DC locomotives but not on AC's.

[Anonymous]

At WABIC tower just east of the Wabash passenger station at Decatur, IL, five tracks of the Wabash crossed three tracks of the IC at very close to 90 degrees - that's right - fifteen diamonds in less than a football field. Listening to an IC coal train going across there was a hoot!

And I once drove from Decatur to Taylorville just to listen to a train of loaded ore jimmies on their way to Granite City go across the B&O diamond at 35 MPH. Another hoot.

Old Timer

[Anonymous]

MC--

Hah--Haven't smashed any boards in a long time. Kicked the habit[}:)][}:)][}:)]

[Anonymous]

Dear Mr. Hemphill,
Thank you very much for setting me straight on that.

Sincerely,
Daniel Parks

[mudchicken]

smashboards anyone?

[CShaveRR]

Yes, Rochelle is an automatic interlocking...first train to get to the approach circuit wins the diamond (if nothing is conflicting).

[Anonymous]

Ok, but, aren't those the backside's of a signal we see in the Rochelle, IL webcam?

[Anonymous]

I don't recall using the word "interlocking". The words were "diamond crossing".

A manually-controlled crossing (for the purposes of the gentleman's question) can and is also often protected on low-speed and branch lines by a locked gate and no signals except a red light/stop sign on the gate. Want to cross?? Unlock the gate, wait the allotted time, swing the gate across the other track and lock it, then go. Special Conditions in TT determine if you have to move the gate back when across and vary by site.

Then there is the IC interlocking in Memphis, down by the river where all the main lines cross--IC/CN, UP/SSW/RI, BNSF/SLSF. Not interlocked. NO ELECTRICAL SIGNALS, NO TOWER. Protected by a 4-way stop--LITERALLY. Stop boards (stop signs) on all tracks, with priority governed by the rules (1st one there goes). Just like at a 4-way highway intersection. Truly manual.

[mudchicken]

QUOTE: Originally posted by jeaton

Mudchicken

Do you mean to tell me that spikes aren't manganese??[:O][:O][:O]

Jay

[:D][:D][:D]

...and the pseudo gold coating/plating they treat them with doesn't exactly bond as nicely as the stuff coming out of the wire feeder/ or arc-welding element either! Wish I had a picture of the spike imbedded filler the lept out of that manganese frog insert! (leaving a big hole)

[jeaton]

Mudchicken

Do you mean to tell me that spikes aren't manganese??[:O][:O][:O]

Jay

[mudchicken]

QUOTE: Originally posted by M.W. Hemphill

Mud: A Santa Fe dispatcher friend (refuses to call himself BNSF) says the crossover frogs on the transcon are welded every two weeks minimum, some of them every 10 days. What's it take to weld a frog in your experience? I recall it was an all day project for a universal crossover for a welder and a helper. And people wonder why the second track is necessary ...

Depends how badly chewed up the tip or wings of the manganese frogs were chewed-up... is 2-4-6-12 inches of the frog point gone? We finally went back to swapping out long-toed frogs (14s, 20s and 24s) and rebuilding the points on a jig back in the maintenance yard. Welders and overtime are synonimous. Your fellow DS speaks the truth. I had the far west end of the transcon (LA to Fullerton, Chico's own enema) and it was a struggle. (Building up the frog while still keeping it cool enough to add the next row of micronang bead with the arcwelder is an art with those guys, I am amazed they can do much of anything now with the few remaining troops)....

Remember clearly as an assistant rdm what happens when an SP welder cheated at Colton and tried to use the bottom 3/4s of a spike as a filler in the manganese insert for the NW crossing frog )[:(][:(][:(]

[tup] to your dispatcher compadre!

[tree68]

Seems like I recall reading once that on DE locos it was necessary to throttle down when crossing a diamond. The purpose was to minimize the possibility of arcing of the traction motors. Still true?

[mudchicken]

The lower speed on the crossing frogs (proper name for diamond$) is to lessen the impact damage on the metal components on the flangeways where the rail hops over the 2 1/2 inch flangeway space. The more acute that angle becomes, the more the gap the wheelsets have to cross over) Design of crossing frogs and manufacture of these highly specialized track component by the big three (ABC/Meridian , CTM/Pettibone and Conley) is an expensive engineered proposition.

Most operating department requests to speed up trains over diamonds die quickly when the chief engineer/ roadmaster [with blood in his eye] asks the Superintendent/trainmaster / ds how he is going to pay for new frogs and continuous maintenance out of HIS budget.

Most of these crossing frogs are custom built [no two frog angles are ever the same, 90 degrees exactly is rare), take 9-12 months of lead time, require explosive hardened (Dharmon should love this) manganese castings and require custom milled rail parts to hold the assembly together. They are the most brittle/ fragile thing to be found in the track structure and are avoided like the plague in new construction. Any frog is job insurance for welding crews and budget eaters for roadmasters. You could run faster over them, but they would wear out faster (at $150,000+ a pop for materials only, not cheap) and you would have maintenance gangs living full time at the crossing frog sites to keep them serviceable)....

[CShaveRR]

Back to the subject of the title:

I suspect that the maximum speed over a diamond might be determined in part by the angle of intersection. The more acute the angle, the bigger the gap in the flangeways, and the more likely something could go wrong. A 90-degree crossing wouldn't need to have much of a restriction at all. But that's a pretty sharp angle at Rochelle, so I doubt that the speed will ever go much above 35. It remained at 35 when they replaced all of the diamonds a couple of years back.

[Anonymous]

QUOTE: Originally posted by M.W. Hemphill

CTC is an outgrowth of the Absolute Permissive Block system of operating automatic block signals, which was a two-way method of running, and beneath that rests the track circuit. The CTC machine sits on top of an APB signaling system -- to this day -- and gives the dispatcher the ability to prioritize traffic, by selecting the direction of the current of traffic, and the position of switches. But the dispatcher merely requests -- the CTC/APB system decides if it is safe or not, using its track circuits, and grants a request after it has checked.

A little off the main topic, but I have a CTC question you can probabl;y answer. On the BNSF racetrack in Chicago, the signals seem to operate 2 ways. Most of the time they'll show red, change to green when a train is coming, then go red and stay that way. I assume that's the CTC operator setting up the track for a single train. At other times, they'll go green, and after the train passes they'll go through the red. yellow, flasshing yellow, green sequence. Sometimes they'll do this for 2 or 3 trains, then go back to staying red. Is the CTC operatpr setting up the track for multiple trains or is the system able to operate in automatic block or what??

[Anonymous]

QUOTE: Originally posted by amtrak-tom

Thanks for all of the replies. I do understand interlockings, it's the diamonds I wasn't sure about. I do find diamonds interesting!

The BN track at Rochelle has a pretty good sized hump going over the diamonds, while the UP is much better. Neither goes through there very fast.

I used to think that maintenance and signaling were the responsibility of the road that got there last, but at Joliet IL, UP's diamonds look relatively new while BN's have a lot of wear and a big dip right in the middle. The tower at Joliet is manned by Metra which runs commuter trains on the former Rock Island which crosses both the BN and UP. With the station on one side and the tower on the other, that one gets really noisey when a stack goes through on the BN.

At West Chicago, the EJ& E mans the tower but I doubt they run more than one or two trains through there during the day, so it seems like that would be a candidate for automation. The Metra commuter trains on the UP over that one don't go more than about 30-35mph.

[Overmod]

A tiny addition: We have a 90-degree crossing just south of Central Station in Memphis. Essentially all the trans-Mississippi traffic going through here crosses this, on three major systems (UP, BNSF, NS) with some 'legacy' features.

The crossing is protected by ordinary stop signs, although not in the north-south (Amtrak) direction! There is also an instruction to use whistle signals when proceeding east-west across the crossing, and a posted 5mph speed limit on at least two of the crossing mains.

[Anonymous]

Thanks for all of the replies. I do understand interlockings, it's the diamonds I wasn't sure about. I do find diamonds interesting!

[Randy Stahl]

Don't stick your foot in the switch points !!!!
like don't tell your wife she's gaining a few pounds!
Randy

[Anonymous]

Dear amtrak-tom,
As I recall, the old interlocking controls and machines were the precursor to CTC. Originally, in the early- to mid-1800's interlockings were often the only places to have operators, as trains operated by timetable only before the train order was developed. This operator manually controlled the interlocking with mechanical signals, such as the ball signal, which was well suited for junctions because it could be seen from practically every angle. A different number of balls visible would authorize movements in different directions on different tracks (I believe), so ball signals would usually have at least four balls (two directions on two tracks). In Britain, the mechanical interlocking machine was developed to ensure that procedures for train movements were carried out in the correct order--if a step was out of place, then he would encounter resistance and not be able to execute the poorly ordered step. However, a well trained operator who enacts the steps in the correct sequence should encounter know resistance. I believe that the mechanical interlocking came into general American use circa 1890. As technology improved, several changes took place. Firstly, electric signals replaced mechanical ones, saving the operator from great exertion. Even so, the mechanical interlocking (and later the mechanical control tower away from diamonds) with its long lines of trakcside rods remained into the end of steam, and probably later. Also with the advent of electricity, electric relays replaced mechanical levers to govern interlocking movements, and the electric interlocking became prevalent. Also, the kind of signal used went from the ball signal, (and a signal in which a long, narrow object was made vertical or horizontal depending on block occupancy--the very first sinal I believe), to lower-, and then on some lines upper-, quadrant semaphores, to eventually searchlights (target signals), and other modern signals. Anyway, it was only a matter of time before someone got the idea of taking the electric interlocking, and using it to govern normal track--CTC. In a CTC system, the electric relays prohibit the operator (dispatcher) from making dangerous moves, such as routing a train into an occupied siding, just like an old mechanical interlocking. When NYC got CTC on its main, it was able to go from two tracks to four, without loosing capacity.

I'm probably wrong about a lot of this, so take this with a grain of salt. This is mostly what I remember from Railroad Signaling by Brian Solomon.

By the way, are the stories about people getting their foot caught in switch points on CTC lines true?

See you around the forums,
Daniel Parks