Why do diesel locomotives have brake wheels, and when are they used?
I understand rolling stock have brake wheels to render them immobile for safety or security purposes. But since a locomotive is large and heavy, and is immobile anyway unless running (whereby it has its own engineer-operated brake systems), what’s the purpose of a diesel loco’s brake wheel?
Hi,
When shut down and no air supply is holding the brake shoes against the wheel tread the brake cylinders will retract and the brake shoes will fall away from the wheel tread.
Then the engine will roll in whichever direction the grade is decending. The traction motors don’t offer much rolling resistance and in fact will act like kinetic flywheels to keep the locomotive rolling.
The brake wheel will pull a chain tight against the brake levers acting in the same manner as the air cylinder. Some of the old Alcos and maybe some GEs had really long hand brake chains.
There are some newer locomotives with electrically powered hand brake mechanisms.
https://www.wabtec.com/products/8409/419-series-safeset-wheel-style-locomotive-parking-brake
Good Luck, Ed
Thanks for the insight. So the brake wheel is only applied when a loco is parked on a grade? Or is it always applied when shut down? Does this require a second crew member to apply the brake while the engineer shuts down the loco?
Many a young and up coming rookie brakeman made that mistake by not tying a cut of cars down…A yard may look flat to the eye but,could have a slight grade.Tie 'em down is the safe way.
When I worked on the railroad engineers might elect to set the hand brake if the engine was going to left idling and unattended for a extended time.
Not sure about today though.
When leaving engines unattended all the handbrakes on the locomotives are applied. Doesn’t matter if they are running or not. An exception is made for engines in a remote distributed power consist. You don’t have to go to the mid-train or rear end dp consists to apply handbrakes.
Jeff
You couldn’t get much larger and heavier than a Missabe Road 2-8-8-4 “Yellowstone” engine, yet they had to be tied down. When the first one was tested, it was left sitting on a level yard track and before anyone noticed it started rolling away on it’s own - luckily workers were able to run it down and apply the brake before it went off the end of the track into a swamp. It was later worked out that the ‘level’ yard track actually had like a tiny grade - something like .2%. BTW thanks to it’s roller bearings, a ‘dead’ engine could be moved on level track by several men pushing on it.
The use of brake wheels on locomotives is almost universal now, however, most first generation power, especially EMD had “pump” or, ratcheting lever type handbrakes. Railroads came to prefer the wheels because during winter conditions, the recesses on the hood would become packed with ice and snow, making using the brake a job in itself. Additionally, when locomotives are tied down and left unattended, some railroads mandate the looping of chains over and under the rails, fore and aft of the wheels in case the handbrake is tampered with. These chains are secured with locks.
Jeff,On the PRR old head steam engineers would apply what you guys call the “three step” and let it go at that and leave the cab. Most of those old engineers agreed that diesels needed a “center off” position like steam engines.
“Dependency should never be placed upon air brakes alone to hold equipment left standing”. That’s pretty close to how it was written in the operating rules, as I recall.
Put a handbrake on, because if you didn’t, it might roll away. For a consist of several engines, if they weren’t going to be left there a long time and you didn’t shut them down, one would do for the whole consist.
The AEM-7’s had a “crank-up” brake, no room for a wheel. The HHP-8’s had a “parking brake” applied with a toggle switch. Not sure what the new electrics have – never been on one.
Not true. Hence hand brakes.
We had an engine runaway because the handbrake was bad. It had recently been repaired, but with an incorrect part. When the hand brake was applied, the chain would tighten and appear to be holding. It wasn’t. The engine had been shut down for fuel conservation when set out, once the air leaked off it started moving on it’s own. A train on an adjacent track saw it take off and alerted the dispatcher. This being in a terminal area had the presence of mind to line it into a track that was holding a portion of a coal train to be delivered to a local power plant. The train had an exMP caboose for use as a shoving platform.
www.rrpicturearchives.net/showPicture.aspx?id=905425
www.rrpicturearchives.net/showPicture.aspx?id=2749842
Jeff
Sorry, I can’t seem to get these links hot. It seems I can over on the Trains forums, but the MR side seems to give me trouble.
Happens to steam, too. No handbrake that I’m aware of but if they forget to chock the wheels —
3734GTW_Pontiac_6-9-55 by Edmund, on Flickr
Sometimes the hostler will move engines that have low boiler pressure, thus low air, and when they grab the independent there isn’t much stopping power left.
So it goes…
Cheers, Ed
Or forgot to “center off” the engine and the engine creep its way into the pit…
Or perhaps the hostler forgot to remove the DCC address or turn the block off when he moved another engine in the engine terminal.
Don’t ask…[:-^]
Another consideration the prototype has is that the handbrake on a locomotive typically only sets the brakes on one truck.
One terrible situation I remember was a crew set one handbrake on one engine of a several unit consist, they didn’t realize it only put a brake on 2 axles. A couple hours later the set of engines rolled out of the track, rolled down hill into an oncoming track, killing the crew on that train.
On CSX we had some ex SCL engines that did not have any handbrakes. We used to chock the wheels until they prohibited that practice. Then they had to left with another unit that had a handbrake applied.
The rules may say set hand brake(s), but I direct everyone’s attention to Lac Magellanic. Enough said.
Dave
Enough said? You didn’t say much at all. Want to say something more?
never mind.
“Enough said”? I’m not sure what you think you’re saying.
The issue at Lac-Megantic was not enough handbrakes were applied.
My point was that no matter what several people say about engine hand brakes, and hand brakes in general, no one has reported any hand brakes on engines or cars being set, it therefore seems this is not a universally followed rule, or practice, or whatever term you wish to call it.
It indeed should be.
Dave