steveintoronto
Superstar
Many thanks for that, as it allowed me to delve more on the MPXpress series of locos and braking systems only to find this gem:
Note: [...a Bombardier regenerative braking system, visible as a thin black "block" above the exhaust section.]
I was exploring the tendency for wheel lock-up for the loco independent brakes v. those of the coaches, and the lack of a sensing circuit inter-coupled with the coach brakes as in an 'anti-skidding' system for airplanes and road vehicles. The indirect answer is to use dynamic braking on the loco in lieu of an 'all train' friction system, (ostensibly facilitated by electro-hydraulic brakes used on trainsets) but that reference to "regenerative braking" puts a further onus on why GO would prefer to avoid braking dissipated as just heat, rather than regenerated. It helps them meet their Tier IV standard!
There's a delicious story in there somewhere...but as you remark, a lot of the juicy bits aren't published for public eyes to read. I'm still looking to suss out the details of the Sharyo "regenerative braking" system. The only reference is to recharging the main batteries and hotel power in published docs. (ZF refer to various PTOs (Power take-offs) available pre and post clutch to engage during freewheel braking and prime motor idle disengaged from the xmssn)
The disc brakes on the coaches are a wondrous thing in themselves, the size alone must render them capable of a very high braking rate, and if there's no inter-coach wheel lock sensing, some other facet of design seems to apply them equitably. I can see how the coach braking would be far superior to mechanical braking on the loco, and much less prone to flat spots.
Edit to Add: Would the MP-54ACs be a lot more immune to this type of "complete mechanical failure"? (dual prime motors, can run independently even if one is completely unusable) If so, it would be the silver lining to this incident.
Monday morning edit to add:
Digging on locomotive 'blended' braking systems (esp for passenger, including E-P, Electro-Pneumatic) shows a lot of results. Getting the specifics as used by GO very difficult, even from Wabtec for the locos, and they produce some of the most sophisticated braking and traction control systems available. But *specifically* relating to the bi-level coaches, the Transit Toronto website has some excellent info as that relates to Vegeta's points on GO braking procedure:
[...]
An interesting feature of these cars is the use of pneumatic tread brakes and disk brakes. It’s the disks that allow a speeding train to stop within the length of a platform. The cars are rated to provide braking up to almost 1 m/s2, which is unusually quick for a car of it’s size. The quick deceleration, coupled with quick acceleration, speeds up service and gets commuters to their destinations without a significant delay at intermediate stops.
[...]
http://transit.toronto.on.ca/regional/2507.shtml
With the new MP54AC locos, newer electronically controlled train braking system (a type of E-P) might be feasible, along with a higher degree of regenerative brake recovery, due to the high level of electronic control and the AC motors. Finding that information is not readily available, at least for my recent searches, on the internet. A lot of it might be held close to the manufacturer as propriety commercial advantage.
http://locomotive.wikia.com/wiki/MPI_MP40PH-3C[...]In 2013, GO Transit ordered 10 more units numbered 657-666, initially to replace the remainder of their F59PH fleet (but instead ended up supplementing them), and to expand/increase service on its lines. These locomotives differ from the older (600-656) units because these are Tier-III/IV compliant, as such they feature a noticably quieter engine as well as a Bombardier regenerative braking system, visible as a thin black "block" above the exhaust section. The locomotives' prime mover and HEP configuration has not changed. [...]
Note: [...a Bombardier regenerative braking system, visible as a thin black "block" above the exhaust section.]
I was exploring the tendency for wheel lock-up for the loco independent brakes v. those of the coaches, and the lack of a sensing circuit inter-coupled with the coach brakes as in an 'anti-skidding' system for airplanes and road vehicles. The indirect answer is to use dynamic braking on the loco in lieu of an 'all train' friction system, (ostensibly facilitated by electro-hydraulic brakes used on trainsets) but that reference to "regenerative braking" puts a further onus on why GO would prefer to avoid braking dissipated as just heat, rather than regenerated. It helps them meet their Tier IV standard!
There's a delicious story in there somewhere...but as you remark, a lot of the juicy bits aren't published for public eyes to read. I'm still looking to suss out the details of the Sharyo "regenerative braking" system. The only reference is to recharging the main batteries and hotel power in published docs. (ZF refer to various PTOs (Power take-offs) available pre and post clutch to engage during freewheel braking and prime motor idle disengaged from the xmssn)
The disc brakes on the coaches are a wondrous thing in themselves, the size alone must render them capable of a very high braking rate, and if there's no inter-coach wheel lock sensing, some other facet of design seems to apply them equitably. I can see how the coach braking would be far superior to mechanical braking on the loco, and much less prone to flat spots.
This is fascinating information! I wonder on the use of two coaches and a loco? Even 50mph is fast enough to get a rescue loco from Willowbrook to Ajax in about half an hour, clear track permitting. The question remains on available track switches to get it in front or behind the stranded consist. What hasn't been made clear that I can find is where the consist that finally did tow it (push it?) back to Ajax came from? Was it sitting there stranded itself all that time? Or waiting empty in Oshawa?It's not a TC restriction but a CN one and is found in their GOI which unfortunately is not a publicly available document. Also 2 units are restricted as well (one locomotive and a coach or two locomotives) to 50mph. But GO had that restriction recinded(after lots of testing) for the UP DMU's.
Edit to Add: Would the MP-54ACs be a lot more immune to this type of "complete mechanical failure"? (dual prime motors, can run independently even if one is completely unusable) If so, it would be the silver lining to this incident.
Monday morning edit to add:
Digging on locomotive 'blended' braking systems (esp for passenger, including E-P, Electro-Pneumatic) shows a lot of results. Getting the specifics as used by GO very difficult, even from Wabtec for the locos, and they produce some of the most sophisticated braking and traction control systems available. But *specifically* relating to the bi-level coaches, the Transit Toronto website has some excellent info as that relates to Vegeta's points on GO braking procedure:
[...]
An interesting feature of these cars is the use of pneumatic tread brakes and disk brakes. It’s the disks that allow a speeding train to stop within the length of a platform. The cars are rated to provide braking up to almost 1 m/s2, which is unusually quick for a car of it’s size. The quick deceleration, coupled with quick acceleration, speeds up service and gets commuters to their destinations without a significant delay at intermediate stops.
[...]
http://transit.toronto.on.ca/regional/2507.shtml
With the new MP54AC locos, newer electronically controlled train braking system (a type of E-P) might be feasible, along with a higher degree of regenerative brake recovery, due to the high level of electronic control and the AC motors. Finding that information is not readily available, at least for my recent searches, on the internet. A lot of it might be held close to the manufacturer as propriety commercial advantage.
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