I want to know the opinions of as many engineers as I can . What are the benefits and drawbacks of the dynamic brake holding feature?
A significant benefit is not having to use the air brake as much. That helps keep the train line charged. Dynamics don’t work at very low speeds.
Again , the question is regarding the DB holding feature , not the dynamic brakes themselves.
Randy, What is that? A feature to automaticly match the DB force to hold a certain speed? Please explain.
The simple explanation to DB holding feature is a device to maintain the dynamic brake setting the engineer has selected while the locomotive is in emergency. The loading in dynamic brake is unaffected by an emergency application of the airbrakes.
Just FYI - because this is over my head:
From a webpage captioned as “Canadian Pacific Railway - Southern Ontario Area - Cartier Subdivsion - Mile 77 - Monthly Operating Bulletin” at:
http://www.personainternet.com/mile77/mob.html
MARCH 2002
REVISED OPERATING DOCUMENTS EFFECTIVE MARCH 1ST, 2002
Canadian Rail Operating Rules (CROR)
General Operating Instructions (GOI)
Clearance Form
REVISIONS TO THE GENERAL OPERATING INSTRUCTIONS (GOI)
GOI Section 16
Item 7.11 - CEFX locomotives: DB Holding and other features
Please add the following new item 7.11
7.11 CEFX 100 - 139 series locomotives: DBI, DB Holding and other features
a) On CEFX 100 - 119 locomotives (which are equipped with DB holding and extended range DB), if an EMERGENCY or a PENALTY brake application occurs, DBI is still enabled thus preventing locomotive brake cylinder pressure build-up. This means that if the locomotive is in DB holding mode, locomotive air brakes can only be applied with the independant brake valve.
CAUTION: If a CEFX 100 - 119 locomotive is controlling and is in DB, special consideration must be given to EMERGENCY of PENALTY brake applications; maximum retardation will be a function of DB handle position and independant brake handle position. Close observation of DB effort displays and locomotive brake cylinder pressures is required.
b) Some important features of these SD90MAC/4300 locomotives (CEFX 100 - 119 and 120 - 139):
- they are equipped with GM’s FIRE screen which means that you
This may also add some insight:
TSB # R01/2009
THE TRANSPORTATION SAFETY BOARD OF CANADA RELEASES FINAL INVESTIGATION REPORT INTO THE APRIL 2007 TRAIN DERAILMENT IN TRAIL, BRITISH COLUMBIA
http://www.tsb.gc.ca/eng/medias-media/communiques/rail/2009/comm_r07v0109.asp
Gotcha, Thanks Randy.[8D]
If I remember right it only works if I am in dynamic when the emergency happens all that I hahe to do is bail off the engine brakes to keep them working.
Rodney
Randy I have never had a engine with this feature, If A emergency happens ( train line ) while in power or dynamic the pcs would hold for 20 sec before cutting out a Operator emergency would cut power right then. It is my opinion ( with out operating a engine with this feature) is it would be useless to me as if in emergency and buched up i use independant to keep engines from running out and when stopped apply them fully no need to have dynamic. But 1 question for you randy is how does it work? The dynamic is a system that uses the wheels when turning to slow or control speed of train. if stopped there is no power generated by the wheels so how would it get its power to hold the train?
Your right Wabash , the dynamic brakes do nothing at a stand still .
Here’s a scenario- You are operating a train that is topping a major grade. the next 5 miles or so are downhill . You notch the throttle handle to off , wait 10 seconds and setup your dynamic brakes. You begin to bunch slack and suddenly the air pops (kinked hose) . On engines without db holding feature your dynamic brakes will shut off. You will bail off the independent and then apply the independant at a contolled rate to keep your now bunched train , bunched. If you had a locomotive with the holding feature the dynamic brakes will not shut off but they will work normally. Once you are stopped you must of course set the independant.
If you have a penalty application the dynamic brakes will still work . If you initiate an emergency applicati
The big benefit is the independent stays released and units stay in dynamic. With out the holding feature there is a hash to severe slack run out when emergency occurs, dynamic drops out and before the independent can get set up from the emergency application. Worst case is a drawbar near the head end causing a derailment. After the independent applies fully from the emergency application there is the possibility of flat spots, especially on poorer rail conditions. Trying to bail some pressure off the independent while still keeping the head end bunched can be a delicate balancing act that the engineer doesn’t always get right. If you have enough units, full independent pressure can easily exceed maximum buff force.
Can’t really think of any drawbacks of the holding feature.
Didn’t SOU (NS) have that feature on assigned units that was only activated for downhill on Saluda grade?
Except, as in any technology, one might become too dependent on its function.
Like Wabash1, I never had units with that feature; however, there were many times I found myself wishing my units had it.
Well sorta there was a switch that operated with a key that would not let the pcs cut out . and only guys on the pokie had it and signed for the key. good points i would say you would not haft to bail and apply independant brakes, bad points once the speed was down anyways the dynamic would not be affective in fact you would go to independant braking anyways. and as far as run out you here your train go into emergency there is no reason to have any run out from improper bunching. the ns engines no longer have this feature they did away with it.took the keys and lights out for the cut out.