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Thread: Jake Brakes

  1. #1
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    Default Jake Brakes

    We had an incident this weekend that I wanted to get everyone's opinion on. While driving a new E-One pumper, I noticed that the air horn was not working properly, it sounded more like a duck call than a air horn. While returning from a call, I stopped at a red light and everyone in the truck started smelling something burning. We all got out of the truck and saw that there was smoke coming from all four wheels of the truck. I pulled through the intersection and into a gas station for a closer inspection and sure enough, the smoke was coming from the calipers on the brakes. One of our Chiefs came out to inspect the truck and said that another Chief told him to check the Jake Brake, which had been turned off by the previous driver. He said that if you turn the Jake Brake off, it will cook the brakes. There are many opinions about turning off the Jake Brake in the rain and slippery conditions, but it was not raining, nor was it slippery. My question is, has anyone heard of cooking the brakes by not having the Jake Brake turned on? I have never heard of this, and have driven fire trucks for a long time, some with Jake Brakes and some without. I have never seen a truck cook the brakes because the Jake Brake was turned off.

    What I think is that there is an air issue that it is not supplying enough air to the horn, and perhaps too much to the pancakes and not allowing them to dis-engage completely when you release the brake pedal.

    I would like to get your thoughts on this, and I thank you in advance.

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    Obviously, with the Jake Brake off there is going to be more "work" for the brakes. Was it too much work? Can't tell you that. I admit, I am old and I don't use the Jake Brake often at all, I normally turn it off. In the 4 years of driving the current engine with a Jake Brake, have not had a brake issue.

    I'm not an expert nor did I sleep in a Holiday Inn last night...but I would agree there may be an air pressure issue. But, too much pressure doesn't sound like the issue. Too little pressure sounds more like it. Air pressure is used to release the brakes, not apply them. The truck should be plumbed in a way that the air horns will fail before you don't have enough brake pressure.
    "This thread is being closed as it is off-topic and not related to the fire industry." - Isn't that what the Off Duty forum was for?

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    Thanks Bones42! No, it really wasn't very much work on the brakes at all. We went about 10 miles lights and sirens, but I am not one to ride the brakes. At no time did I have to lay on the brakes.

    You are correct about the too little air over the too much air. I wasn't thinking while I was typing this out, and you are also right that the air horn would not work correctly before there was an issue with the brakes. I was just blown away when I was told that not having the Jake Brake on would cook the brakes. I have never heard of that and I too have driven trucks without the use of a Jake Brake. I am not a fan of them at all.

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    Quote Originally Posted by smarion View Post
    Thanks Bones42! No, it really wasn't very much work on the brakes at all. We went about 10 miles lights and sirens, but I am not one to ride the brakes. At no time did I have to lay on the brakes.

    You are correct about the too little air over the too much air. I wasn't thinking while I was typing this out, and you are also right that the air horn would not work correctly before there was an issue with the brakes. I was just blown away when I was told that not having the Jake Brake on would cook the brakes. I have never heard of that and I too have driven trucks without the use of a Jake Brake. I am not a fan of them at all.
    In general, not having the Jake Brake turned on shouldn't cause you to cook the brakes unless either:
    A. The vehicle is badly overloaded
    B. The driver is using poor driving/braking techniques
    HBofCJ likes this.

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    This area of Pennsylvania has some extended and steep (between 4 and 11%) grades. Under these circumstances, failure to gear down and to use the engine brake will result in rapid loss of braking. Although fire apparatus are exempt from required stops and reduced speeds (20 mph) it is imperitive that the DPO uses a lot of common sense and available equipment to control the decent on the hills. When running MA going south, I typically drop one gear (4th) in the beginning of the long hill (approximately 5 miles) and use the engine brake on high, with the initial grade at around 5%. There is a level spot, where it is possible to run back up into 5th, but still use the Jake. The second section has about a 10% grade and requires dropping down into 3rd with the Jake on full and periodic application of the air brake to control the decent for the last 3/4 mi. This is hard on the shoes and pads, but the wear needs to be balanced by the degree of urgency on the call. If you are just going on stand-by, then I drop down to #2 and use only the engine brake to control the speed by flipping between high and medium. (The aerial and lead engine have a 3 position engine brake that uses either two, four and all six cylinders for braking.) After working the brakes hard it is wise to check the action of the parking brake adjustment. There are two ways of doing this. 1 - Roll slowly out the pad 3 to 5 mph and pull the parking brake on with the transmission in nutral or clutch in. The truck should stop quickly before reaching the street. #2 - (we have numerous hills) take the apparatus to a grade of at least 12%, stop on the grade and apply the parking brake. The truck must not drift or move with the parking brake applied. If your engine is equipped with "S" cam or wedge braking system it is possible to "Cam over" the brake system. This is usually caused by mis adjusted shoes and then a hard application, This will usually apply one brake, but not all brakes. It can result in a fire, especially with an inexperienced driver who does not yet have a feel for how much throttle is needed to roll the apparatus down the road. Automatic transmissions make this harder to recognize. If running a standard shift, the driver will feel the brake dragging when making the shift. City running, the brake system should be designed to handle the sort of brake applications that occur in a normal, high congestion run. Slippery conditions will see me running with the Jake off or with it in the lowest position. The braking system on the apparatus is designed to balance the forces between axles, so that one wont slide any sooner than the other. Since the down forces determine the "adhesion" of the tire to the pavement, the braking force of the front axle and rear axle need to match the weight load on each axle. 40,000 lb engine with 24,000 on the rear and 16,000 on the front should be set-up with 60% braking on the rear and 40% braking on the front. This way, you won't get one axle sliding before the other one reaches its maximum stopping force. On slippery surfaces, with the Jake on high, the holding power of the engine brake is added to the braking power of the rear axle. This will make the rears slide before the fronts and on a high crown road or a super-elevated turn, the rear will slide toward the ditch, while the steers still roll normally. I do not claim to be an expert, but I spent 10 years driving over-the-road for a national freight carrier pulling 53-102's. It creates a certain "Pucker Factor" when you look in the mirror and see "The Billboard" swinging in that direction. While speaking of TTL's, there are still a number of conventionally braking trailers being pulled by modern anti-skid braked tractors. The better stopping power of the controlled braking tractor makes a jack-knife a great danger under slippery conditions. Stay Away!!!

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    All drivers need to be trained to drive with and without the Jake brake. You can be quite a bit more aggressive with the Jake brake on but if you haven't practiced driving the route without the added stopping power the Jake provides, you'll be in for a surprise.

    Lot's of downshifting, slowing down before the top of the hill, and generally slowing everything down is the way we have to drive in the somewhat hilly territory we have around here.

    We've had a truck without a Jake where you had about two chances to stop on the way to call, otherwise you'd end up being unable to stop anywhere if you needed to. Surprisingly, we were able to add the Jake for ~ $3,500 (onto a Detroit 6V92) and it made a world of difference.

    The braking power of the Jake is dependent on the horsepower of your engine. In rainy weather, we've never had a problem with the rear end locking up. With snow or ice, our SOP is to shut the Jake off.

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    maybe I am missing something here , but sounds like you had low air pressure and your low air alarm wasn't working, so your brakes were dragging.

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    Quote Originally Posted by slackjawedyokel View Post
    maybe I am missing something here , but sounds like you had low air pressure and your low air alarm wasn't working, so your brakes were dragging.
    I'm with you.

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    Quote Originally Posted by slackjawedyokel View Post
    maybe I am missing something here , but sounds like you had low air pressure and your low air alarm wasn't working, so your brakes were dragging.
    Exactly what I was thinking.
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    Quote Originally Posted by Stuart View Post

    The braking power of the Jake is dependent on the horsepower of your engine. In rainy weather, we've never had a problem with the rear end locking up. With snow or ice, our SOP is to shut the Jake off.
    All of our trucks have the Jake Brake is tied into the ABS system. If wheel slip is detected, the Jake is kicked out. I think this is the standard these days. I would check on your particular vehicle though.

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    Wow. I suppose it depends upon local conditions, grades, run length, transmission type, driver training, experience, etc., etc.. In 1970 my School bus I drove part time pretending to go to junior college had a Jake. My old Crown Supercoach ex schoolie Bus Conversion motor home had a Jake. Also had the infamous RTO910 Roadranger. Most all the on/off road trucks I drove had Jakes. I had a old pickup truck with a Jake. 353N. Yep! Lots of Jakes. They are cool.

    If your fire apparatus had a Jake Brake, then one might assume that the driver training would include the safe and proper use of such. A Jake Brake is a safety device intended to complement the service brakes. That means the driver ideally would know how to safely operate the apparatus even if the Jake Brake was not working, or had failed. Any competent operator would instantly know if the Jake is not working. The noise and the feel are pretty obvious.

    Perhaps there is more to the story here? I do not have enough information to make a value judgment. Perhaps the air horn and the smoky brakes are separate incidents? Unrelated? For the air horn to not blow right may indicate a low air pressure situation with all the warning lights, bells and whistles implied? The important thing is that you took the correct action and got the apparatus stopped safely. No Jake equals smoking brakes? Dunno. HB of CJ (old coot)

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