Anyone make type 3636 brake chambers in long stroke?

belfert · April 15, 2012, 08:45:17 AM

I'm considering switching to all long stroke brake chambers if I have the room. My spring brakes are type 3636. Does anyone make these in long stroke? I've been looking without success so far. Long strokes seem to only come in type 3030 or smaller.

belfert · April 16, 2012, 08:06:45 PM

Anyone? I noticed that type 3636 chambers have 3" rods. Are those considered long stroke?

I have noticed that the smaller brake chambers like the type 16 only have a 2.5" rod on the long stroke models. Do all of the chambers need to have the same length rod? I suppose some of these questions can be answered when I go to my Bendix air brake class in two months.

buswarrior · April 16, 2012, 08:30:23 PM

The length of the rods sticking out is not relevant, they can be any length.

It is the potential travel of the rod that determines whether it is a long or standard stroke chamber.

Depending on what you weigh, Type 36 are awfully big chambers.

Provided you have enough swept area, both on the drives and the rest of the braking, dropping to Type 30's might be a safe choice.

happy coaching!
buswarrior

belfert · April 17, 2012, 06:08:57 AM

It looks like I need to look at the total stroke travel of the chambers if I can find that data.

My bus weighs around 38,000 lbs unloaded. I am guessing with full water, cargo, and passengers I would be closer to 41,000 lbs. GVWR is 45,000 or 46,000 lbs. Dina used all kinds of unique brake chambers. They used rotochambers on the steer and tag axles and they used type 36 chambers on the drive axle. The rotochambers on the tag axle have been replaced with standard chambers. The cost for two standard chambers and labor was less than the cost of one rotochamber.

rv_safetyman · April 17, 2012, 08:16:10 AM

OK folks, I have to show my ignorance here. I don't understand why long stroke chambers are needed for a "standard" application. I am not sure what "standard' is, but let me give you my definition. If a standard (non-long stroke) chamber is used on a bus now, then it seems to me that the geometry (actuating arm length vs stroke required) would not benefit from a long stroke chamber. Certainly you would not want to use the long stroke to somehow compensate for out of adjustment brakes.

On my bus, the stroke is quite short if the brakes are adjusted properly.

I could see a need for a long stroke chamber if the brake arm is designed with a longer length (and thus, more throw for the same angular rotation of the S cams).

So, would someone educate me as to why Brian "needs" the long stroke?

Jim

bevans6 · April 17, 2012, 09:11:55 AM

AS far as I know, long stroke just lets you get away with not adjusting the stroke as often. They can be considered safer, in that if the auto adjust slack adjuster stops adjusting, you have longer before it gets to be a problem DOT inspection-wise. You are correct in that the geometry of the slack adjuster angle to the push-rod gets less advantageous as the stroke gets longer, hence less braking power per unit of pressure. I don't know of any other advantage to a long stroke chamber, except for the ability to overcome worn parts or lack of maintenance. Obviously in line-haul work, being able to keep rolling is a bigger advantage. On the other hand, I don't know of any disadvantage to long stroke chambers, either.

Brian

belfert · April 17, 2012, 10:14:09 AM

I don't "need" long stroke chambers. My bus has very expensive rotochambers on the steer axle and used to have them on the tag axle. I've been having issues with need to replace the rotochambers because they quit retracting all the way. I already replaced one rotochamber on the front before realizing I could have just put standard brake chambers on and saved $200 or more.

My thought is if I need to replace one of the rotochambers on the steer axle to just replace all six brake chambers with long stroke. The real question is would the long strok chambers fit, but if I can't even find the appropriate 3636 brake chambers in long stroke so it may be a moot point.

belfert · April 17, 2012, 03:21:04 PM

Quote from: buswarrior on April 16, 2012, 08:30:23 PM
The length of the rods sticking out is not relevant, they can be any length.

It is the potential travel of the rod that determines whether it is a long or standard stroke chamber.

I was thinking what I read was the length of the push rod, but rather what is listed is the length of the stroke. Isn't stroke length generally supposed to be equal amongst all brake chambers? I'll have to do some more research.

rv_safetyman · April 17, 2012, 04:14:44 PM

Before I asked the why question, I did a bit of searching. This PDF seemed like a pretty good resource:

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CE8QFjAB&url=http%3A%2F%2Fwww.newlifeparts.com%2Fcatalog%2Fsection3.pdf&ei=RoSNT4iDJsaX8AGhg-2SBw&usg=AFQjCNHElvaTNeJ6_g6SwnFS2mzRU_ER9g

Sorry about the long link.

It looks to me like the long stroke chamber is taller (longer) as you would expect. It would also require a special diaphragm that would allow more stroke.

Jim

belfert · April 17, 2012, 04:38:27 PM

I've looked at the New Life Parts catalog several times. I just noticed they have a local location, but it isn't clear if they sell to individuals.

Most places are really good at selling you a replacement for what you already have. It is a lot harder to find someone who will recommend a replacement that is different. They don't want to take the time and they usually don't want to take the liability either. A parts guy isn't going to know much about replacing short stroke brake chambers with long stroke brake chambers.

buswarrior · April 17, 2012, 07:22:20 PM

ok, here we go...

A long stroke chamber has a deeper body, allowing the push rod more travel before the piston inside runs out of room to move at the end of the chamber interior.

Since it has more room inside, the chamber has a longer legislated adjustment limit. For instance, a long stroke Type 30/30 parking/service chamber will have a trapezoidal tag attached to the clamp bolts that advertises a 3" maximum stroke, not to be confused with the legislated 2 1/2" adjustment limit.

So, it can stroke 2 1/2 inches before it is considered unsafe or illegal, you choose your terminology.

A regular Type 30/30 chamber is only legal out to 2". DD3 are 2 1/4".

Automatic slack adjusters were known to allow the stroke of regular chambers to approach and sometimes slightly exceed the adjustment limits before they did their adjusting thing.

Which is bad, because a high heat stopping event will extend your cold push rod travel by at least 1/2 an inch due to the brake drums expanding from the heat, and all the parts having to move out further to keep squeezing.

And tickets get issued when they stroke too far.

Long stroke chambers were developed to help automatic slack adjusters do their jobs. As well, you will appreciate that the deeper diaphragms necessary for the internals may not have been as reliable with the materials of yesterday.

As for power, a long stroke chamber does not degrade in power output as it nears the adjustment limit like a regular stroke chamber does. Less internal forces opposing the direction of brake application.

The angles involved with the mechanical leverage of the slack adjuster don't change much in the way of degrees over the extra 1/2 inch of legal travel allowed.

There are more problems with push rod/slack adjuster angles being of less than optimum orientation for mechanical strength due to installation errors in the choice of how long to cut the push rod, than installing a long stroke chamber ever could. Too many busnuts blindly install new chambers unwittingly mimicking what the last inept installer did.

Be sure to research proper installation techniques, don't just copy the last idiot that worked on the coach.

Regardless of your kind of slack adjusters, from a safety standpoint, the more push rod stroke you can have available to apply the brakes, the better, regardless of whether you pay attention, or not, or somewhere in between.

As for the meaning of life, I expect that there will come a day when the world will look back on the 2 decades from the early 90's to the early 20teens and wonder why those old short chambers kept on being specified on new equipment for so long after the long stroke was introduced. The transportation industry has a long history of resolutely denying change.

If it was me, if long stroke chambers will fit in a particular vehicle's axle geometry, and you are buying new brake chambers anyway, by all means upgrade to get another 1/2 inch of usable push rod stroke.

happy coaching!
buswarrior