I recently saw a lone GP-something trundling down the middle track on the Q racetrack. High-greens as far as the eye could see but the engineer was throttling back and forth to keep the speed down to maybe 25mph. I’ve seen other light moves on the racetrack and none that I remember were going very fast. Assuming there is a speed restriction, what’s the reason? Braking ability, electro-mechanical, or something else?
Gate circuit activation shunt issue
BN/BNSF used to restrict light engine moves to 50 mph but that was changed in the last few years to 60 mph, system wide.
I always thought light engines were authorized for passenger train speeds, At least out here anyway.
Sir Mudchicken, could you please expand on this? I don’t see what the problem would be unless everything was restricted.
Short train or engine hop
Polished rail
The fewer the axles, the more likely there will be a continuous active shunt causing the relays to detect an occupied section of track. More speed increases truck hunting and oscillation in the wheelsets.
Result:Pumping Gates
(similarly, rusty side tracks at gated crossings cause a similar problem)
enuf?
PS - What’s this “Sir” stuff?..Mookie has attempted, and so far failed, to “crown” this old dirty iron bird - But that is another tale…
EMD has been known to run test engines and an instrumentation car at speeds in excess of 100 MPH at times between La Junta and Trinidad, CO with a special liability permit absolute block and nothing ever happened.
I dont know about the modern stuff but Big steam Locos dont have enough brake power to stop them selfs over 20 or 30 mph, so movment is slow with out a train to provide braking.
Gunns
any locomotive running single is ussualy restricted to 50 mph max and 30 mph approacing crossings with protection., One is earlier mentioned shunting problem, were the gates could go up with engine aproaching a crossing.
the Max speed is low for braking purposes, a Light engine has no brake redundancy and any mech issue will make brake distance sometimes 3 times that of a multiple engine consist.
Sorry, didn’t mean to offend. I got that from Mookie.
Anyway thanks for the explaination. Is this a problem on highly polished mainlines too. I wouldn’t think so.
Can get that anywhere- remenber that the wheel contact patch on the rail is very small and add intermittent contact with a weak DC current. Sometimes the potential is not there to affect the circuit.
Dear Gunns,
You mentined this earlier, but I have trouble believing it. I crunched some numbers with 2926, and it has about the same braking capacity as a loaded freight car–nada problema. After all, what would happen if a knuckle broke between the tender and the first car–your locomotive at 90 mph would, by what you say, be in deep trouble. No railroad would ever let a locomotive run faster than what it could safely run with its own brakes. After all, braking a knuckle is fairly common occurance. If you have some literature on this, please clue me in.
Sincerely,
Daniel Parks
How many wheels have brakes on a steamer??? I know there are lots of different answers but what would be typical? The way I understand it the earlier ones did not even have brakes.
On CSX…single light engines are restricted to 30 mph. Multiple light engines can operate at track speed.
From my limited observations, normally the drivers and the wheels on the tenders have brakes. Since drivers normally had ‘sweated on’ tires to provide the flanged wheel it was advisable not to use the engine brake to any great degree as the heat from braking would go directly to the tire thus causing it to expand…too much expansion and the tire comes off the wheel center and now you really have a mess.
Hi All,
the 2926 weighs in at allmost 500 tons, brakes exist on all the drive wheels and on the tender wheels. This gives about 4 and a half square feet of breaking surface, <24 * 30 inches square approx> riding on 24 rail contact points. Lock her up and you will burn the brake shoes off of the holders, during opperation the Loco depends on the train brakes to slow down and stop If you broke a knuckle, you can still stop, but it is a matter of many miles. As far as I know the only crew fatality was caused by an Engineer misreading a speed limit sign and hitting a 35 MPH curve at 90 mph outside of Flagstaff, the surviving crew said they tried to stop but locking up the brakes didnt seem to help.
Intresting spec sites,
http://www.nmrhs.org/p-steamloco/sl-specs.html
4-8-4 comparison site
http://www.sbrhs.org/484com.html
Thats what I have for hard numbers, Evrey thing else comes from survivng Engineers here in Albuqurque, and from Steam Hoggers I’ve met…
Of course I could be wrong, It wouldnt be the first time…
Gunns
There might be a track restriction,say 30MPH,but on UP we run track speed.
Thanks baltACD and Gunns for your answers.[8D]
Back in the 80s I got called for a dog catch on the BN and we deadheaded w/ a light eng. As soon as we got out of yard limits it was 79 MPH. I won’t vouch for the legality but it was kinda fun.
on csx…alone 1 light unit is restricted to 30mph… 2 or more units…good for what ever track speed is…1 unit and 1 car…good for what ever track speed is…
csx engineer
If this was the case, we would have wheels falling off locomotives and railcars all the time…they are pressed on the axels also.
The fact that we can drag them around with the handbrake set and heat the wheels till they glow red hot and still not fall off should put to rest this theory.
If you have ever seen them “sweat” a tire on rim, you will understand that you would burn away the brake shoe, down to the brake head, even with the old cast iron shoes, and never get the tire hot enough to make it expand enough to slip off the rim.
The heat generated by the braking forces is dissipated through the entire tire and rim, they expand at the same rate, so the rim expands as much as the tire, and that’s a lot of steel to heat up!
Add to that the tremendous weight resting on the drivers….
Driver tires are heated to the point they achieve a “plastic” quality, fitted, then allowed to cool, and trued up to run straight.
In 40 plus years of rail fanning, I have yet to see a photo, or find a credible story, of a tire parting from a rim due to braking heat or braking force.
Ed