Im a retired locomotive mechanic installing 26L in a big steam engine and I was wondering if the drivers or empty tender would slide wheels in emergency (If I remember correctly it might be 70 psi for a 45psi system) if the engineer forgets to bail off.
Ask Ed Dickens [}:)]
Short answer: yes. Drivers can slide very easily, and I think the problem can occur even if fairly sophisticated blended braking techniques are applied to the independent. Flatting driver tires is an expense out of proportion to the gain in stopping effectiveness from aggressive use of the independent on driver foundation.
With respect to the tender: use one of the commercial devices used on centerbeam pulpwood cars and some others with radical loaded-to-empty weight ratios to adjust brake proportioning. And be certain to put a placard in the cab indicating the range of derating for ranges of low fuel or low water.
Anytime you see sparks coming from the wheels whether it’s in a movie or real life, it means the emergency brakes have been applied.
I’ve seen a few scenes where the emergancy brakes are applied and the wheels are still spinning.
Blanket statements like this make me just shake my head!
I totally agree with you BigJim. I spent many an evening at the horseshoe curve and would watch the coal trains and ore trains coming down the hill with a ring of sparks encircling every wheel. And no, ATSFGuy, they were not in emergency. It was just everyday railroading on the hill.
The ‘sparks’ are a consequence of the brakeshoes doing what they’re supposed to, helping to remove frictional heat from the wheels. Modern composition brakeshoes can work similarly to ablative heat shields for orbital re-entry, and are generally ‘better’ than the old sacrificial cast-iron or matrix type.
Of course, the outgassing that goes along with the sparks can impede the actual friction that does the braking. That is why a train that exceeds a speed of 23mph on parts of Seventeen Mile Grade will proceed to run away no matter what the brake-cylinder pressure is – and yes, the wheels will still be “spinning” even as they are acquiring a beautiful blue oxide coat.
Thanks Ed,
If I remember right 26L goes to at least 70psi in emergency and when bailed off comes right back which would not be good for our steam engine engineer who has to worry about alot else in emergency. As I recall #6 airbrake with the #6N distributing valve ( the Milwaukee 261 and the Calif 3751) has a 55psi pop valve that prevents any brake cylinder pressure above that pressure. I was wondering what our origional 8ET Westinghouse system did for brake cylinder pressure in emergency or your 844 if it has the old brake valves.
Gentlemen- I was an ass’t train master for 5 years back in the '70s for the Pittsburgh-area Union RR. I don’t remember ever seeing any load sensors on any of the hoppers or covered hoppers we handled in & out of the 6 US Steel mills we serviced. Also, I never saw any of our “car knockers” adjust any brake rigging s as a car’s shoes wore - they only replaced cpndemnable shoes with new ones. Are new hoppers typically equipped with load sensors, and if so do these merely detect spring compression or can they tell a “part-load”?
Load sensors in the '70s did exist – you can see some of them referenced in contemporary Car Builders Cyclopedias (and perhaps wanswheel can put a couple of them up to see, or provide live links to online content). They were of course not something that would be put on lowly hoppers, even the simple mechanical kind that gauged the deflection of the truck springs; if I recall correctly, the only real place they were used (e.g. by some of the Canadians) was on relatively low-weight cars like centerbeams used for lumber shipment, where the actual braking ratio would change dramatically from loaded to unloaded and it would be comparatively rare for the car to operate partially loaded.
Modern ‘adjustments of brake rigging’ are handled by automatic slack adjusters (just as adjustments to shoe clearance in drum brakes have been done ‘automatically’ just by reversing, for a great many years) precisely to accommodate shoe wear, stretch and pin wear appropriately. I have a suspicion that composition brakeshoes wouldn’t be as cost-effective if this ‘feature’ weren’t commonly provided.
There are some modern load-sensor devices that ‘weigh’ the car (and condition, debounce, etc. the signal) just as if it were sitting on load cells. This is one of the kinds of data that the ‘wireless train line’ in last week’s story would communicate. I have my doubts that more than a few steps of resolution purely in car weight over a three-piece truck is going to give you highly different and more exact braking control in equal proportion. That money would be much better spent in adaptive wheelslide control (which, I am finding, can be done in a foundation setup!)
The situation with modern ‘hoppers’ – meaning mostly things like aluminum bathtub gons – is a bit complex. On the one hand these things have comparatively high payload and minimized tare, so they need some sort of accommodation of brake strength
RME- thanks for the reply. So, today if I buy a unit train’s worth of regular 110-ton mixed-use bottom-drop hoppers for use on the US, will either load sensors or automatic brake rigging adjusters come as standard feature?
Load sensors, probably not. (But I am not an expert here, and there are others on the forum who have experience here)
Slack adjusters have been standard issue for many decades, and I almost can’t imagine a car released into interchange service that wouldn’t have them.
When I was a high school senior (1954), our class trip was on the B&O from Cincinnati to Washington DC. On our return to Cincinnati, on the National Linited (#1) west of Cumberland (Cincinnati trains took a cutoff and bypassed it) I spent a lot of time in the coach’s vestibule and coming down some of the WV grades was a sight that I have wished I had had a camera for as it was dark, and there were only the EMD’s headlight shining ahead sometimes on the track for the short stretches that didn’t have a curve, the car window lights showing the woods below us and a string of fire from all the brake shoes on the train. Trainman had come through the train and set the retainers. After we got off the grade, the fireworks ended and we did not stop, just continued on to the next station.
I concur with another poster that "ATSFguy"s quote is incorrect.
If sparks only fly in emergency why do they want us using DB and as light as an air brake application as possible in the summer to prevent right of way fires???
Air brakes decrease speed by forcing brake shoes against wheel treads and turning the motion of the wheels against the brake shoes into heat - heat that can throw off hot particles that can start fires - there doesn’t need to be visible sparks to ignite fires.