Problems With Trolley Shoes on Flexity Cars

The streetcar system on Tuesday evening suffered a major outage when all Flexity cars were ordered to “stop and stay” on their routes following an overhead failure at King and Spadina. At the time, a problem with power surges was also reported.

Through comments and emails I received, I learned that there had been a developing problem with the carbon inserts on trolley “shoes” on the new Flexity streetcars, and I pursued this issue with the TTC. Following an investigation, their response arrived this morning.

Premature wear of carbons on pole configuration is normal during periods of high humidity and high precipitation.  The carbons absorb the moisture, become softer, and wear out faster.  Under dry conditions, the carbons are expected to last 4-5 days.  Under wet conditions, they are expected to last 1-2 days.  A review of maintenance records for the past 3-4 days indicate the latest carbons that were installed on the LFLRV fleet lasted less than 8 hours.  We believe this significant reduction in carbon life is due to a combination of factors that include:

  1. A potential quality problem with the material composition of the carbons.
  2. The use of pole configuration with the LFLRV design.  The LFLRV design requires a higher current draw through the power collection system.  Normally this higher current draw is handled through a pantograph system.  The pantograph system has a larger carbon strip which helps to dissipate heat and distribute wear.  On a trolley pole, the higher current draw through a smaller carbon generates more heat and wears quicker.

Due to the reduced carbon life, usage of these parts in the past 48-72 hours has more than doubled. Subsequently some vehicles burned through their carbons and started to run on the bare harp that resulted in numerous pole dewirements and the downed overhead on St Clair.

To conserve and maximize carbon life the following plans are being implemented:

  1. Immediately drop the 12 mm threshold for replacement to a nightly check of 7mm min. material remaining at the front, leading edge of the carbon.
  2. Strict control of carbon shoe counting and sign-out.
  3. Keep all replaced carbons for evaluation/recordkeeping.
  4. Sort through old, discarded stocks of carbons and retain those with more than 9mm depth remaining at the leading edge. Use these on a dedicated fleet of panto only cars for Harbourfront. We only need to use these carbons to get us to Exhibition and back each day. Save all new carbons for pole only routes.
  5. Expedite the testing and start-up of panto use on Spadina.
  6. Reserve “Seattle” carbons as a last resort. These carbons are thinner and our previous experience found they had a shorter service life. At best they should be used on the shortest mileage/time based runs. There is added risk of them wearing out mid-day, requiring more frequent road inspections.

In addition the above, staff will be expediting test runs of LFLRV on the pantograph system along the Spadina route.  Overhead crews are also expediting the conversion of the St Clair route.

[Email from Brad Ross, Executive Director Corporate and Customer Communications, February 22, 2018]

There have been several problems with overhead down in recent weeks, and events of the past few days are clearly connected with the long run of rainy weather.

The move to accelerate the conversion of Spadina and St. Clair to pantograph operation is welcome news, but this begs the question of the status of the King and Cherry routes which use a large and growing part of the Flexity fleet. Conversion to full pantograph capability of the overhead along them is still some time off, and the schedule for this work lies in 2019, notably at the King/Queen/Roncesvalles where replacement of the track is also planned. A further problem is that service on King routinely short turns and diverts via streets that are not planned for conversion until 2020.

This project has slipped by about a year from plans in earlier capital budgets with more work now in 2020 than in previous versions.

2017 Version

[Source: TTC 2017 Capital Budget Blue Books Page 57]

2018 Version

[Source: TTC 2018 Capital Budget Blue Books Page 61]

Updated: In response to a comment asking for an illustration of this problem, it turns out that I have an old trolley shoe with a broken carbon in my collection. This is from a Peter Witt car.

This shows what one does not want to see. The contact wire should run along the carbon surface, but instead here will drag against the metal. Also the shoe will ride higher on the overhead potentially contacting pieces of the suspension system.