Total brake failure during a panic stop

[scboolitcaster]

Wolfgang:

TM 9-2320-361-24-1

Fresh in my mind because I'm about to do this stuff for the first time.

 

[Tracer]

This thread reminds me to check both wheels on my front axle. Sobering to read this thread and see the pictures.

 

[Wolfgang the Gray]

Wolfgang:

TM 9-2320-361-24-1

Fresh in my mind because I'm about to do this stuff for the first time.

Thanks. I found I didn't have it in my collection (45 TMs & counting), but I found it at this site & the diagrams are very clear & readable. http://www.liberatedmanuals.com/search.mpl?q=tm-9-2320-361-24-1&..

 

[eme411]

I had a issue on my CCKW's rear cylinders after a D-day trip , truck had Chinese rear cylinders installed in the UK, and US in the front, by the time the truck was shipped home the rears had brake fluid pouring out of them , replaced all the rear with US cylinders and 10 years later still dry as a bone, I'm VERY careful about parts I buy and where they are produced, NO Chinese parts of any kind!

 

[18operator]

I had a front metal brake line let go on me. Fortunately I was still in the barn doing my pretrip inspection. Lots of spraying dot 5! Easy fix, took about an hour with bleeding the system.

 

[DavidWymore]

I had my VW sand rail wad up a shoe just like that going down a big rocky hill. Scary. Now I will be welding my deuce shoes when they're off.

I think a good idea would be to periodically find a safe place and practice panic stopping our deuces. Good practice for driver to know what to expect and find any weaknesses in the system.

 

[rustystud]

I had my VW sand rail wad up a shoe just like that going down a big rocky hill. Scary. Now I will be welding my deuce shoes when they're off.

I think a good idea would be to periodically find a safe place and practice panic stopping our deuces. Good practice for driver to know what to expect and find any weaknesses in the system.

Every 6 months our busses must pass a brake safety inspection. One of the tests is to take it out back and get the speed up to 20 mph then slam on the brakes. We have a nice testing device that measures brake force and total "G" force. We have to do 3 passes. All busses must pass at .500 "G" force on all 3 passes. If it doesn't pass then the brakes must be replaced on all axles. I believe you can get one of these testers for a pretty reasonable price and test your own truck.

 

[DavidWymore]

Every 6 months our busses must pass a brake safety inspection. One of the tests is to take it out back and get the speed up to 20 mph then slam on the brakes. We have a nice testing device that measures brake force and total "G" force. We have to do 3 passes. All busses must pass at .500 "G" force on all 3 passes. If it doesn't pass then the brakes must be replaced on all axles. I believe you can get one of these testers for a pretty reasonable price and test your own truck.

Thanks. That reinforces my idea. Everyone always preaches brake inspection, but how is a guy supposed to inspect the inside of his brake lines for rust pitting? I'm going to do some brake testing on my deuce. Start on dirt and work up.

 

[rustystud]

Thanks. That reinforces my idea. Everyone always preaches brake inspection, but how is a guy supposed to inspect the inside of his brake lines for rust pitting? I'm going to do some brake testing on my deuce. Start on dirt and work up.

As far as the brake lines go, just replace them with stainless steel or that "cuprinal" that peashooter was selling. I believe he lists the place where you can buy it. Then you know your brake lines will never rust out ! Peace of mind is a good thing !

 

[m1010plowboy]

Every 6 months our busses must pass a brake safety inspection. One of the tests is to take it out back and get the speed up to 20 mph then slam on the brakes. We have a nice testing device that measures brake force and total "G" force. We have to do 3 passes. All busses must pass at .500 "G" force on all 3 passes. If it doesn't pass then the brakes must be replaced on all axles. I believe you can get one of these testers for a pretty reasonable price and test your own truck.

You're probably the guy that can answer this question for me then. The Early Deuces, G749 series of trucks seem to begin leaking at the wheel cylinders, premature of scheduled maintenance. Mine have been good for 5 years, except for one WC on the bottom left rear, but I'm real light on the pedal and avoid heavy braking.

I have a wee understanding on hydraulics but the air-pak in the Early Deuce has me wondering.......

Do the Wheel Cylinders receive the same pressure that the 'input' from the pedal is giving them in an Air-Pak system??

Paslcal's theory tells me that if I slam on my brakes, the entire system receives the same in-put. I'm assuming it's designed to accept the maximum pedal inputs over and over and the only way to test it, by your bus example, is to tromp hard on the system to see if it breaks...the brakes.

I was trained not to use the brakes up so when we need them most, they are the best they can be. All compliments of my efficient Irish father and brilliant truckers.

Could we reduce damage to our braking systems by being lighter on the pedal, timing our stops and better situational awareness?

 

[Wolfgang the Gray]

Every 6 months our busses must pass a brake safety inspection. One of the tests is to take it out back and get the speed up to 20 mph then slam on the brakes. We have a nice testing device that measures brake force and total "G" force. We have to do 3 passes. All busses must pass at .500 "G" force on all 3 passes. If it doesn't pass then the brakes must be replaced on all axles. I believe you can get one of these testers for a pretty reasonable price and test your own truck.

Can you provide the make & model of your break tester? Definitely sounds like a "gotta have" tool in the Deuce tool box.

 

[scboolitcaster]

You're probably the guy that can answer this question for me then. The Early Deuces, G749 series of trucks seem to begin leaking at the wheel cylinders, premature of scheduled maintenance. Mine have been good for 5 years, except for one WC on the bottom left rear, but I'm real light on the pedal and avoid heavy braking.

I have a wee understanding on hydraulics but the air-pak in the Early Deuce has me wondering.......

Do the Wheel Cylinders receive the same pressure that the 'input' from the pedal is giving them in an Air-Pak system??

Paslcal's theory tells me that if I slam on my brakes, the entire system receives the same in-put. I'm assuming it's designed to accept the maximum pedal inputs over and over and the only way to test it, by your bus example, is to tromp hard on the system to see if it breaks...the brakes.

I was trained not to use the brakes up so when we need them most, they are the best they can be. All compliments of my efficient Irish father and brilliant truckers.

Could we reduce damage to our braking systems by being lighter on the pedal, timing our stops and better situational awareness?

That's interesting. I wonder which wears brake parts more (or builds up more heat for that matter), more pressure for a shorter period or less pressure for a longer period?

I'm going to have to look into the physics of it now.

 

[rustystud]

You're probably the guy that can answer this question for me then. The Early Deuces, G749 series of trucks seem to begin leaking at the wheel cylinders, premature of scheduled maintenance. Mine have been good for 5 years, except for one WC on the bottom left rear, but I'm real light on the pedal and avoid heavy braking.

I have a wee understanding on hydraulics but the air-pak in the Early Deuce has me wondering.......

Do the Wheel Cylinders receive the same pressure that the 'input' from the pedal is giving them in an Air-Pak system??

Paslcal's theory tells me that if I slam on my brakes, the entire system receives the same in-put. I'm assuming it's designed to accept the maximum pedal inputs over and over and the only way to test it, by your bus example, is to tromp hard on the system to see if it breaks...the brakes.

I was trained not to use the brakes up so when we need them most, they are the best they can be. All compliments of my efficient Irish father and brilliant truckers.

Could we reduce damage to our braking systems by being lighter on the pedal, timing our stops and better situational awareness?

OK first question. Yes we know in a sealed system the pressure will be the same in any place along the line, but the Air-Pak is basically two systems. It gets a little confusing since it does share the same fluid source, but the master cylinder only applies the Air-Pak. The Air-Pak using air pressure increases the line pressure up to around 800 PSI. The master cylinder itself only pushes a small valve which opens an air valve in the Air-Pak which allows air to push against the large air piston which pushes the rod in the Air-Pak fluid chamber which pressurizes the fluid out into the brake lines then to the wheel cylinders. The harder you apply the brake pedal, the more air your allowing into the Air-Pak chamber which in turn pushes harder against the rod which pressurizes the brake lines more. There is a small metered orifice between the master cylinder and the Air-Pak which allows fluid to flow when it is "Not" pressurized. I know it gets a little hard to follow. If only I had a "Power Point" on this. But basically there is two brake systems. I have a brake gauge installed in my deuce and without any air pressure built up I can get the gauge to go up to about 500 PSI if I really push hard and use the steering wheel to pull against. Something you normally would not do. With normal air pressure (120 PSI ) and applying the brake normally I can reach pressures well over 800 PSI . If I really mash down like I did without air pressure I can reach over 1000 PSI . So basically the Air-Pak doubles the pressure from the master cylinder.
Second question. I'm not saying to stomp on your brakes, just use them normally, and yes it will keep your shoe linings and drums lasting longer if you are better aware of your surroundings so you "don't " need to slam on the brakes. It is a good thing to "exercise" your brakes daily. It keeps things moving which can rust up and helps keep seals lubed. I once did a complete brake system rebuild on a truck which the owner proudly said " I never need to apply my brakes ! " . Well the whole thing was a pile of rust ! The rear shoes had actually rusted to the anchor pins and backing plate. I needed to hit it with a hammer to remove them ! The springs had rusted as did the adjuster wheel. Since this was a truck that used DOT 3 brake fluid the wheel cylinders had also rusted since the pistons never came out of the bores. The only thing stopping this truck was the front brake pads (disc brakes) and if he really ever needed to do an emergency stop, his truck wouldn't !
I always say our vehicles are just like the human body. If you don't use them they stop working. So use your brakes normally.

 

[rustystud]

Can you provide the make & model of your break tester? Definitely sounds like a "gotta have" tool in the Deuce tool box.

The one we use at work is the "Vericom" VC4000 .
I realize this unit goes for $1400.00 but there are other cheaper units out there like the "Matrix" 3 Axis unit which sells for $250.00 plus shipping on eBay.

 

[DavidWymore]

Had an idea...valve to close off air intake, probably after turbo. Emergency shutdown in case of runaway and would provide engine braking in case of brake failure.

 

[daytonatrbo]

The one we use at work is the "Vericom" VC4000 .
I realize this unit goes for $1400.00 but there are other cheaper units out there like the "Matrix" 3 Axis unit which sells for $250.00 plus shipping on eBay.

There are a number of choices in any smartphone's "app store" for G Force meters or accelerometer readouts. Since almost any modern smartphone has a surprisingly good 3 or 6 axis accelerometer.

It may not be as well calibrated as a 1400 or even 250 dollar unit, but it should give you a very good idea if you have a sturdy way of mounting your phone in the cab.

 

[daytonatrbo]

Had an idea...valve to close off air intake, probably after turbo. Emergency shutdown in case of runaway and would provide engine braking in case of brake failure.

There are a few members that already have this. The first one that comes to mind is HanksDeuce.

 

[DavidWymore]

There are a few members that already have this. The first one that comes to mind is HanksDeuce.

Yeah, been reading up on it. Trying to decide between intake shutoff or exhaust brake or both.

 

[daytonatrbo]

Yeah, been reading up on it. Trying to decide between intake shutoff or exhaust brake or both.

I seem to recall reading that exhaust brakes were not recommended on these trucks.

 

[scboolitcaster]

Neither is blasting the intake with a fire extinguisher I imagine, but most of us would do it in an emergency.

Interesting reading here: http://www.steelsoldiers.com/showthread.php?17584-Exhaust-Brake