bronzeonion
Member
Just thought of something, I know that older stuff like CIGs and 37s have manual screw down handbrakes but how is it applied on modern stuff without the manual handle?
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Parking brakes on modern stuff?
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asylumxl
Established Member
I'd imagine it'd be automatically applied depending on the reverser position etc. but I can't say as I am not a driver.
Class 66 = Automatic with push button in either cab or manually with crank handle if the automation doesn't work.
On London Underground trains there is a Spring Applied Parking Brake (SAPB). The brake is held off by air pressure and is applied by a spring when the pressure is lost. This is an automatic procedure as the train loses air the brakes apply, so no manual intervention is required on behalf of the Train Operator or depot staff (unless you can't get the thing off!)
bronzeonion
Member
How does the automation work? For example if in a totally dead locomotive without any air pressure at all, how is it applied or released? Or would this be done with the handle on the 66?
Nym
Established Member
For some more detail on this...
On conventional stock the SAPBs apply only on driven axles, and will apply when main line and train line air drops below between 0.8bar and 1 bar.
The more modern stock with smart valves and SAPBs where fitted, have brake gateway units that hold main line air pressure hard on with a non-return so when the air dies on the train, there is still air on the brakes before SAPBs come in.
Please do note though, that SAPBs can be driven through if motoring, but this would never happen on conventional or modern stock due to several pressure switches that do not allow motoring without train line air or a round train circuit, and sufficent main line air. Unless of course braking has been cut out on a spesific car / unit.
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bronzeonion
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driver9000
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Parking brakes can be applied by hydraulic or electric on locomotives using a push button in the cab.
Modern multiple units have a spring parking brake which is held off with air pressure to provide the fail safe. No air in the system and the parking brake applies, it can also be applied from the cab in emergency. On Sprinters the brake holds on 2 wheels on the unpowered bogie.
Modern multiple units have a spring parking brake which is held off with air pressure to provide the fail safe. No air in the system and the parking brake applies, it can also be applied from the cab in emergency. On Sprinters the brake holds on 2 wheels on the unpowered bogie.
Nym
Established Member
Not a clue...
If you want any more spesific info drop me a PM or ask on here, braking systems on conventional stock at the moment are pretty much second nature, not so much so on the newer stock (the likes of 2009TS)...
Its electrical via the loco batteries. If the batteries are dead then its a case of doing it by hand.
edwin_m
Veteran Member
Isn't it permitted to drag a dead Underground unit against the parking brakes if there is no other way of recovering it? I believe also the parking brakes will stop it from the low speeds that would be used in such a rescue, if the unit became uncoupled.
On 321's and 360's the parking brake is merely a spring brake equivalent to step one on the brake control. It is held off by the air in the main reservoir pipe so if all the air drains out of the main res the parking brake will apply. On the 321's there is a parking brake isolation valve on the second mans side so you can apply the parking brake even if the unit is full of air.
JB25
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377's are Sprung applied, air released, so eventually if you lose all the air on one you can't get the Parking brake off and a fitter would have to come and wind it off.
Cherry_Picker
Established Member
Most (if not all?) modern units are spring loaded. It is a bit of a culture shock if you are used to not having to worry about the parking brake when you go to loco hauled work where you do. I was so paranoid about potentially forgetting to put the parking brake on a 67 when I first signed them that I would find myself checking I had done it half a dozen times!
Nym
Established Member
I have been told it is permitted to drag against SAPB either with intra or inter unit coupling, or train to train emergency coupling.
SAPB after being dragged any kind of distance will be cooked, and therefore useless, the only assured braking force when dragging a dead unit is the brake force on the unit dragging it.
You cannot however drag a dead unit without having used the brake release valves on any stock, especially on conventional stock that has a healthy air system, dropping the train line will slam the brakes hard on with everything the aux resoviors have...
Put it this way, when I was on a T&W Metro with what looked (and smelled) like a dragging SAPB on one bogie, sparks were flying, even at around 15 - 20mph...
PS: You'd never do this in a depot, using the SAPB Overide works very nicely, see the thread "How many people to push a Mk3" for how many of me it takes to push a single D end trailer
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This is similar with 319's, though there are two types:
Modified - every time the desk is shut down the air is vented from behind the spring and the parking brakes come on. They also come on if main air pressure drops below 3 bar. You can manually apply the parking brake via an isolating cock and can also manually represurise them if they are stuck on too.
Unmodified - only come on if the air in the main reservoir pipe drops below 3bar. Can also be manually applied.
Both modified/unmodified parking brakes on a 319 are on both DTS only and only on the inner bogeys.
If you are dragging a dead loco the parking brake has to be isolated. If you switch out the batteries on a class 67 the parking brake will automatically apply and this is why you need to isolate when dead hauling a loco.
bronzeonion
Member
Is the driver not allowed to wind it off?
Nym
Established Member
Why would a driver want to move a train with no air? (and therefore no brakes!)
This isn't unusual, we don't let our drivers anywhere near the SAPB, no air = no train!
Southern313
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No we aren't allowed to wind off the parking brakes on 377's. Job for fitter from Lovers/Selhurst with his big spanner.
bronzeonion
Member
A driver would be able to move a unit with a rescue unit by dragging the parking brake on the dead unit using the '10-2-10' rule in order to clear the line or get the unit to a location where the problem can more easily be sorted out but yes, certainly wouldn't wind it off. You can easily move a train against a parking brake though-take 313s for example, they generally start rolling when you take power against step 1 on the brake until you release it.
The parking brake on modern stock will only normally apply when the unit is cut out in the sidings and so is only to stop it rolling away-as has been said it is usually only equivalent to step 1 which in some units (especially 321s) won't be nearly enough to stop a moving train any time soon (I once accidentally left step one in on a coasting 100mph 321 on the downhill section from potters bar and didn't notice until southgate when I saw the gauge as there was no slowing down whatsoever!)
If the unit runs out of air most modern stock has a low air governor or low brake res gov which will automatically apply the emergency brakes when the main air drops below 4-6bar.
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