brake survey

[bevans6]

Long stroke answer - long stroke brake chambers are identified by having a square boss cast into the chamber body where the air hose attaches.  Long stroke brake chambers have an allowable stroke of  3".

Brian

[DaveG]

Brian, you are partly correct. Some brake chambers (MGM) have a square boss at the air connections, but I don't believe all do. Others are marked in different ways. And while the stroke of a type 30 long stroke is 3", the readjustment is more like 2.5". Just like a type 30 stroke is 2.5", the readjustment is 2"

[bevans6]

That bears investigation, then.  So far, from what I have read and from my DOT air brake course, the square boss is a mandatory identification feature for DOT inspectors to be able to easily see if the can is LS or not.  And the 3" was to be the DOT failure test (max allowable stroke on a roadside DOT inspection), not where it should be on readjustment.  It seems that LS chambers are now highly recommended!  I am planning to change my front cans this spring, I think I will search out the long stroke version.

Brian

[buswarrior]

Long stroke chambers have square air line connection ports, in the spring chamber models.

Long Stroke plain chambers (for the fronts) have round ports, and a tag on the clamp, which can vanish. Sometimes you'll get an "L" stamped into the cover with the size, around the air connection, but the end covers are the same for both types, so sometimes not.

A long stroke is fairly noticeable in that the depth of the body is fatter than a standard stroke chamber.

But, of course, that's no good if you aren't familiar with some kind to compare them...

I'd suggest that an article for the magazine on brakes had best stick closely to published facts. Taking a poll on here for content is a little scary...

happy coaching!
buswarrior

[DaveG]

The survey was to determine how many different size brake chambers should be covered and how much time to spend on ASAs

[bevans6]

Not beating a dead horse, but I was captured by the idea that there should be a standard for identifying LS brake chambers, and obviously there is and I found it: SAE J1817.  I'm too cheap to pay the money to actually buy a copy of the standard, my SAE membership isn't current, and I couldn't find a copy free on the internet...  But I did find this useful little presentation -

http://www.leonardbus.com/images/photos/Air%20Brake%20HM.pdf

I strongly suspect that the pictures on pages 7 and 8 or thereabouts in that presentation are copied directly from the SAE specification document, they just have that look about them.  They specify both a tag and a square port - since there are  three different types of long stroke actuators (Classes 1, 11, and 111) each with a different maximum stroke, the tag is to further identify and specify the stroke.  I had been taught that there was only one class or type of LS actuator, so that was good to learn.  Also note that compliance with SAE specification isn't necessarily mandatory for a manufacturer.  Further reading indicates that the maximum allowable stroke in service is 80% of the maximum stroke listed, and that a vehicle is placed out of service if more than 20% of the brakes on the vehicle are out of adjustment.  If you have a bus with tags, you can have one brake out of adjustment and roll on, if you have a two axle bus like mine, one out is 25% and go directly to jail...

So I learned a bunch this morning!  It's a good day when you learn something both useful and new!  Now I am going to go out and plug in my bus block heater, this afternoon I am going to start it to load test the batteries that I ran totally flat in the fall (less than 1 volt), and recharged to 100%.  I figure starting the bus at 30 degrees is a load test...

Cheers, Brian

[DaveG]

In addition to the Out of Service (OS) criteria you listed, one of those brakes can not be on a steering axle, so keep and eye on your steer axle brakes for stroke, lining thickness, etc.