Ok, I got my answer about the Rochelle, IL webcam site being around 35mph for the diamond. My question is: are all diamonds made for only that low of a speed?
And, are diamond crossings treated like an interlocking with Home Signals, Interlocking Rules, etc??
Answers:
(1) No
(2) Yes, generally, but in some cases are manual and not signalled. Exception is usually yard trackage and industrial tracks.
Most Diamonds are around 40mph (main line of course)
There are Automatic Diamonds (which means, The first train that shows up is the first one to get the signal)
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 elect
Don’t stick your foot in the switch points !!!
like don’t tell your wife she’s gaining a few pounds!
Randy
Thanks for all of the replies. I do understand interlockings, it’s the diamonds I wasn’t sure about. I do find diamonds interesting!
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.
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.
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??
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.
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)…
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?
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!
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)
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.
Ok, but, aren’t those the backside’s of a signal we see in the Rochelle, IL webcam?
Yes, Rochelle is an automatic interlocking…first train to get to the approach circuit wins the diamond (if nothing is conflicting).
smashboards anyone?
Dear Mr. Hemphill,
Thank you very much for setting me straight on that.
Sincerely,
Daniel Parks