Can someone explain these brake canister bolts to me?

[daschae]

Brake canisters, one has bolt, the other side doesnt. What is their purpose and do they need to be there?

 

[Coffey1]

Yes they need to be there and will kill you if you take them apart incorrectly.
They are your brakes and the parking brake.

 

[wheelspinner]

The bolt indicates that someone caged that brake can. For some reason. Need to uncage it (take the bolt out) and see if it is operating properly. With only one you will probably find that can has got a problem.

 

[quickfarms]

The bolts are called caging bolts.

There are two types of air cans

The single chamber, they have one retaining band and only apply the service brakes.

The air cans in the picture have two cambers. One chamber is for the service brakes. The second chamber is for the spring, parking or emergency, brakes and this chamber also has a big spring in it under a lot of pressure that is very dangerous if taken apart incorrectly. The caging bolts are used to manually release the spring brakes. There are several reasons this may be necessary, they range from towing to a problem with the brakes.

The truck should not be driven with the caging bolts in place. It is an out of service condition.

I would suggest that you go to school to learn about this stuff before it bites you.

 

[Coffey1]

Amen brother Amen.

 

[wreckerman893]

What Jeff said. Better read than dead.

 

[dawico]

Brake canisters, one has bolt, the other side doesnt. What is their purpose and do they need to be there?

View attachment 561886

The brake on the left is normal. The brake on the right is caged. This means the brake is rendered inoperable, either for towing (with no air supply) or to take it apart and service it.

There is probably a reason why it is caged and should be checked out immediately. The spring inside there is very dangerous and the caging bolt hold it tight so the brake canister can be serviced safely.

This is a very dangerous part of the system to work on. Since you seem unfamiliar with it, professional help is advised. At the minimum, lots of research about the operation and dangers is required for your safety before you attempt to mess with it.

So yeah, what these guys said.

 

[Castle Bravo]

The brake on the left is normal. The brake on the right is caged. This means the brake is rendered inoperable, either for towing (with no air supply) or to take it apart and service it.

Caging the spring brake renders the spring brake inoperable, but the service brake still functions.

 

[daschae]

Ok, thanks for the info everyone. It lead me to the right answer. I just bought 2 5 tons in Barstow and was noticing this. I am very mechanically inclined, but not familiar with brake canisters, as I have never ventured there, I pay to have brake work done. So it makes sense they are caged, for towing, since they were at Barstow for auction. I will leave them that way until I get the trucks home. Towing 1 with the other. Do the 5 tons have air couplers on the front to keep supplied while towing? Ive never looked closely before.

 

[gimpyrobb]

They should have glad hands on the front.

 

[porkysplace]

It would probably be a good idea to read this before picking them up .

TM9-2320-272-10.pdf
TM9-2320-272-10 Operations manual for the M939 series trucks. Sept 2004

 

[sed6]

This video shows one of our members servicing the brakes. It shows how to remove and install the pins. It also explains why you can kill yourself working on them. My disclaimer is the same as his, for informational purposes and should not be attempted. https://m.youtube.com/watch?v=i8qp53AIQrA

 

[bigbe5678]

Hi Sed6 Thanks for the heads up I bet you probably saved someone from hurting themselves

 

[Floridianson]

It is easer to remove the whole canister and while you do it do the inner pancake too. The vid makes it look harder than it is. There is nothing to be afraid of if you caging key fits and locks correct. Bring the whole unit to the work bench and R&R there is what I find easer.
http://www.steelsoldiers.com/showth...lems&highlight=rebuild+the+air+brake+chambers

 

[daschae]

Printed out the TM, thanks! Ill leave the brake work to the guy who does the brake work on my Prevost, he's cheap enough and knows what he's doing!

 

[98G]

While towing one truck with the other THERE IS NO REASON TO CAGE THE BRAKES!

Hook up service brake air, and emergency brake air, AND LEAVE THE BRAKES UNCAGED. This way if something goes wrong, you still have your spring brakes applied . Otherwise if something goes wrong the towed vehicle has no brakes.

I'm in Tucson, not far from you. I have the appropriate air lines and the appropriate towbars and safety chains for your upcoming recovery. Come by and I'll demonstrate the safe way to set up to flat tow one 5ton with another, no charge....

 

[daschae]

I appreciate the offer! Ive got a fella up here named Bill in Mesa that buys and tows these things all the time, Im going by to see him and borrow his bar, chains, air lines, and lights in about an hour.

While towing one truck with the other THERE IS NO REASON TO CAGE THE BRAKES!

Hook up service brake air, and emergency brake air, AND LEAVE THE BRAKES UNCAGED. This way if something goes wrong, you still have your spring brakes applied . Otherwise if something goes wrong the towed vehicle has no brakes.

I'm in Tucson, not far from you. I have the appropriate air lines and the appropriate towbars and safety chains for your upcoming recovery. Come by and I'll demonstrate the safe way to set up to flat tow one 5ton with another, no charge....

 

[98G]

I will leave them that way until I get the trucks home. Towing 1 with the other.

Don't do it that way, seriously. Take that cage bolt out. See why it was in there in the first place. If your brakes are funtional, tow it with the service brakes live and the emergency spring brakes enabled. You're playing with tremendous forces here; there's no good reason to disable a safety mechanism. The life you save may be your own.

 

[daschae]

The site keeps telling me in not logged in every time I try to post a reply....

He's got the socket to take those off, I will remove them and see if the brakes function properly. Do these 5 tons have the hand controller for the trailer air supply like a regular over the road tractor? So can you apply the brakes to the vehicle in tow from the tow vehicle?

 

[98G]

If you supply air to the emergency circuit, it is very likely that the cage bolt will wiggle out anyway - the 120 psi is likely to compress the springs more than the cage bolt, allowing the cage bolt to rattle out.

I won't tell you to go to school to learn this stuff, but you really really need to have a thorough understanding of how the airbrake system works before you drive one of these things, let alone flat tow one with another. You need to understand it well enough to intuitively know what will happen next in a failure, and the possible modes of failure.

PM sent with some info that the site doesn't like discussed...