Friday, February 13, 2015

The Secret Science of Sleet Scraping

Ice is an insulator.  So if ice or sleet forms on the third rail or trolley wire, as often happens during the winter, it can bring an electric railroad to an embarrassing and expensive halt.  To solve this problem, we need the aid of Science.  So if you like scientific details, keep reading!

We shall, of course, start with the CA&E.  When the line was built in 1902, nobody had much experience with keeping a third-rail interurban running. In the early days they tried putting a tank of either brine or calcium chloride solution in the front vestibule and letting it drip through tubes onto the third rail.  This was a real mess, as you can imagine, and it damaged the rails, the insulation, and so on.  The third rail fixtures themselves were in a state of flux at this time, but by about 1913 or so the road had settled on the third rail beam design that was used until the end.  This design includes pneumatic sleet scrapers.

Here's what the standard sleet scraper looks like.  The cylinder is fed through a flexible hose, and the piston pushes the cast iron scraper shoe down onto the third rail.  There's one on each side of each truck, and all four operate in unison.

The cylinder looks like this, upside down.  The shaft goes down through a slot in the wooden beam, and the shoe is bolted onto the bottom.  You can see the spring that pushes the piston up when air is released.  I meant to measure the vertical travel, but it's about 6".

The shoe looks like this.  They tend to be pretty worn down.  The shoe has an electrical connection so it will act as a current collector when in use.

The scrapers on the lead car are controlled by a valve to the right of the brake valve.  On the wood cars there's just a simple on-off valve as seen here.  

On the steel cars, however, there's a more complex valve that uses a second brake handle, of the same type as the M-23 motorman's valve.  This is more than a simple on-off valve, but I'm not sure how it works since we never use it.  I must confess that David was basically correct about this, although I doubt this was actually a motorman's brake valve of some sort.

Because of the great force the pneumatic cylinders could exert, I would assume it was necessary for the motorman to raise the scrapers wherever there was a gap in the third rail.

The CRT/CTA has always been able to use simpler means of scraping the rail, largely because traffic is much more frequent on the rapid transit lines, and during sleet storms they would send out extra trains just to keep the rails clear. Here's what one of the more modern scrapers looks like.  At the top is a long leaf spring, which drives down the scrapers at each end.  Ordinarily these are kept in the up position, as here, by means of a lever.  By turning the handle, the scrapers drop into position.  Of course, they are then always down and cannot be raised while the train is in motion.  But that is evidently not necessary with the flexible scrapers used here.  I think most of our rapid transit cars had these scrapers on only one truck.  

As for other third-rail equipment at IRM, the Michigan Electric car had pneumatic scrapers similar to the CA&E's mounted on the front truck only.  The Com Ed 4 and the S motor used an under-running third rail where sleet would not be an issue.

But of course sleet can be a problem with trolley wire as well as third rail.  The greater flexibility of trolley wire (particularly simple suspended) makes it easier to knock the ice off, but most cars can have only one pole up and you have to remove the ice and collect current at the same time.  Somewhere we have examples of sleet-cutting trolley wheels and I'll try to get a picture of one.  It looks sort of like a miniature turbine wheel.

Here's an interesting solution from the Illinois Terminal.  Combine 277 has a trolley pole mounted near the front of the car with a special sleet cutting shoe.  During the winter, a retriever would be mounted so the front pole could be raised.  This would enable the rear pole to collect current reliably.  Of course, if the front pole dewired, a crewman would have to climb onto the (presumably icy) roof to take care of it!  We are certainly lucky that IRM can just shut down during the winter.


Anonymous said...

What about pantograph operations in sleet - ice stroms?

Anonymous said...

Thanks for the information. I always enjoy learning about how things worked on the CA&E, and am fascinated with the effort to refurbish this rolling stock to (mostly) operational condition. It reminds me of a burning question. The last time I rode the CA&E, the buzzer cord that runs down the center of the cars was used by the conductors to signal the motorman on when to start (double buzz). At least one of the cars at IRM has another buzzer cord that runs down one side of the car. What was that for?
Thanks again for this blog and your great posts.
Lee Wells

Randall Hicks said...

1) I knew the question about pantographs was going to come up. I've got to do some more research about that, and get some pictures.

2) All of our interurban cars (CA&E, NS, IT...) will have a cord for the conductor's valve, used to set the brakes in an emergency. This is always along one side of the car. And we test it to make sure it works. Now I know of at least one place where the conductor's valve and its cord were removed from their CA&E car because they had had problems with passengers stopping the train for frivolous reasons, I guess. But for multi-car operation we think it's essential for safety that the trainmen or passengers in a rear car can stop the train in an emergency. And I don't know when that's ever been done unnecessarily.

Brian L. said...

I believe, at least with the PRR GG1s, and perhaps with the South Shore 800s, the leading pantograph was used to knock off the sleet and ice, with the rear one used to collect current.

Other than that, I'm not sure.

Randall Hicks said...

I believe Brian is correct. Pantographs are usually set with a much greater force against the wire than poles would be, and there are two contact surfaces to keep the pan level, so that should usually be enough. I believe I read that on the Lackawanna, the motor cars each had two pans; one was set for normal operating pressure, and the other was set at higher pressure for use only during sleet storms.

We also talked about whether it was necessary on the CA&E to raise the scrapers at every third rail gap. This would no doubt be a lot of work for the motorman, but I don't think these pneumatic sleet scrapers could easily be forced up, and why else would you need the handy valves at the operating position? Does anybody know of some other line that had scraper controls like this?

Anonymous said...

When the CA&E cars were run with multiple car trains, were the sleet scrapers used only on the leading car?
Given that the CA&E shops probably used solid pieces of wood to construct the 3rd rail beams, I wonder how long it took their shop forces to construct one of these from scratch?

Randall Hicks said...

The scrapers could only be operated on the lead car, since there's no way to connect the piping between cars.

I would think that once the machinery is set up to produce these beams, it would go quickly. We can see from pictures that every year during the summer, the usual third rail beams on several cars would be replaced with ones lacking sleet scrapers, so they could be overhauled. And presumably the wood was replaced as necessary at that time.

Anonymous said...

OT - Switching a bit from sleet scrappers to snow - while looking at the snow mess in Boston I ran across a picture showing a Boston Green line Light Rail Vehicle pushing a yellow contraption with a plow. Link here:

Can anyone explain why they don't mount the plow on the LRV? - Weight?

Randall Hicks said...

It's a miniature Russell plow! I hadn't seen one of these before, so thanks. As for the advantages of such a device, I can only guess. Presumably this plow is ballasted and can be much heavier than anything mounted on a car. And if it derails, it should be easier to put back on the track, and nobody much cares if it gets a little dented in the process.

Anonymous said...

Speaking of a "Russell Snow Plow," since Mr. Kutella took a leave of absence from the blogs, I have not heard any updates on IRM's Russell plow. Will its restoration be completed this summer possibly?

Thank you.

Randall Hicks said...

Although it is not possible to work on the plow itself in this weather, a lot of work is being done in the shop on various parts. I'm not sure what the schedule is, but I would think the exterior painting could be essentially complete this year.

Anonymous said...

About the sleet scraper valve pictured on the 431...that was indeed designed originally as a motorman's brake valve. It's a National type PV-2 or PV-3 straight-air brake valve, more commonly seen on streetcars...though the first AE&C "shorties" used a similar-looking straight-air valve from Christiansen. I suspect the use of streetcar brake valves to work the sleet scrapers began with surplus streetcar valves from the Fox River Division, and later led the CA&E to purchase new-production valves for their cars.

The handle is a solid brass handle like what's used on the Vera Cruz car...some of the CA&E issue handles had the lower anti-removal projection cut off.


Randall Hicks said...

Thanks, Scott, that's quite interesting. What you say certainly makes sense. The first steel cars were acquired in 1923, at the same time that most of the older cars on the river division were being retired, so their brake valves would be available. Neat!

Chris said...

The Bahston plow looks like a stack of steel plates on wheels. The motor looks beat up.

Randall Hicks said...

Our friend Eric Lorenz writes:

I wanted to chime in on sleet scraping. At CTA we operate a modular sleet fighting train that consists of pumping deicer fluid thru tubes from inside the car down to special trolley shoes. Jugs of fluid and a portable electric pump are plugged in inside the car. A car repairman then rides the train and manually switches the pump on and off to whichever side the third rail is on at the time. This is usually done with a revenue service train while passengers are riding.

Eric Lorenz, Repairman, Midway Shop.