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Country Discussion Topics
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Air brakes?
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Clod    Posted 07-23-2003 at 19:31:19       [Reply]  [No Email]
It was later in life before i really understood that air brakes were actually spring brakes.The spring is the reason the brakes stop.So if your air pressure drops too low the spring shoves the brakes on.Too bad people do not explain things like that without makeing it sound complicated.

Willie J    Posted 07-24-2003 at 06:35:48       [Reply]  [Send Email]
I presume here we are talking about truck brakes, as railroad brakes are another completly different style.
The handle on steering collumn is to apply trailer only,rarely used except when adjusting axle apacing.
There are 2 air lines,"supply or emergency" and "service or control"
Supply line charges the tank under trailer & controls the emergency valve. When tank pressure reaches approx 60 psi the valve charges the spring chamber to release parking brake & holds it released. Any pressure drop below approx 60 will allow the springs to set brake.
Service line is normal 0 psi, & works on another port on the relay valve. Operating foot pedal or "trolley" valve sends a low pressure signal to tank valve. This sends pressure through a seperate line to a seperate diaphram to apply brake. Pressure varies with amount of movement of pedal. The emergency & service diaphrams are piggy-backed in the big canister, operate independently, but push the same push-rod.
During normal driving, one hose will have tank pressure, up to 125 psi, the other will have no pressure.
Now that you are all thoroughly confused, it's time for more coffee

Clod    Posted 07-24-2003 at 06:46:20       [Reply]  [No Email]
They are so simple untill a problem developes.I saw one guy here saying the front brakes are air applied.Well,,That is why I had trouble with the front brakes of a Gradeall that I couldnt fix a few years ago.The owner will spend 90 thousand bucks on a used machine but not 30 on a repair manuel for it.

Lazy Al    Posted 07-24-2003 at 03:47:01       [Reply]  [No Email]
Front wheel brakes are air operated and back wheels are air release . Don't tear apart unless
you know how .

steve ii JD 4000    Posted 07-23-2003 at 20:00:39       [Reply]  [No Email]
yes that is right.. got to think different than driving a car or a 18th wheele.
as you drive down the road and see 4 long black marks on the road those are from the trucks that lost it's air to brakes in far back end it locked up when truck is moving down the road! I did see that happen in front of me. and I have a CDL too..

Clod    Posted 07-23-2003 at 20:28:54       [Reply]  [No Email]
Cat Scrapers used to use air brakes,,Think they still do.Often a line leaks to the back and it locks.I used a compressor on my mech truck to locate leaks and test to unlock a certain brake I suspect is bad.The Gradeall ditch diggers are a nightmare when they have leaks because the cab circles and leaks get there.

Willie J    Posted 07-23-2003 at 19:47:49       [Reply]  [Send Email]
You are partly right. The "service" chamber on air brakes is air operated, spring release. The "emergency" or "park" chamber is spring set, air release. The chambers are "piggy-back", both work on the same push rod.
Willie, diesel pilot-retired

Clod    Posted 07-23-2003 at 19:59:36       [Reply]  [No Email]
Oh,,Will J.. The park handle on the steering wheel?I bet that is the air applied brake.I never cared because everyone said not to use or trust them.I guess they serve some purpose.I only drove the big trucks when I had to.Glad you dropped in here ,Come by often.

Old Sarge    Posted 07-23-2003 at 19:36:18       [Reply]  [Send Email]
Yeah and they're the easiest, and cleanest to work on too. No leaky cylinders, no sloppy mess.

Clod    Posted 07-23-2003 at 19:39:46       [Reply]  [No Email]
My nephew was in a shop one time and took a spring out of the diaphram cylinder.It went through the tin roof.They are very stout springs.

markct    Posted 07-24-2003 at 11:22:41       [Reply]  [No Email]
yea there was a guy killed about a few years back in a local shop by one of those springs, the chamber was badly corroded and he was under the truck banging on some suspension parts, the shock from that was enough that the chamber broke and the spring flew out and hit him in the head and he died instantly. dont mess with airbrakes unless ya know what you are doing, and clod it sorta scares me that ya were operating trucks with air brakes and ya didnt even know how they work or how to operate them, dont mean to insult ya but that could have been real dangerous even just driving them around the farm

Clod    Posted 07-24-2003 at 15:58:50       [Reply]  [No Email]
Hello up there. I had a TEN TON truck license in 1963 from the Army.I guess I did ok though my job was not driveing trucks.There are many fighter jet pilots who have never took apart a turbojet engine nor an inverter or gyro.Do you do diesel mechanic work?I have set in truck stops and listened to drivers talk trucks.Though I worked on dozers and didnt study gear ratios.I have had these same drivers come back in the resturant and ask me to get their truck going.No.I am not an expert on air brakes nor have I driven an 18 wheeler across this country .But I can park one in a big refinery where many of the professionals could not.Have you delivered to a construction site where they are building the big buildings you have to drive inside?With al the studs sticking up in the concrete floor.That is not like down on the farm.

Redneck    Posted 07-24-2003 at 04:20:05       [Reply]  [No Email]
I know an old diesel mechnic that is disfigured because of a chamber spring.Knew better but was in a hurry and didn't have it locked.

randy    Posted 05-02-2004 at 02:21:37       [Reply]  [Send Email]
how do you cage the spring brake?

Bob/Ont    Posted 07-24-2003 at 14:53:50       [Reply]  [Send Email]
Redneck, that's the Darwin principal applied to Maxi Brakes Eh. They are right next to recoil springs when it comes to Dangerous.
Later Bob

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