| Author | Message | ||
| Doug Ritter (Texrbama)
Registered Member Username: Texrbama Post Number: 20 Registered: 3-2007 Posted From: 70.5.233.252 Rating: N/A |
Just returned from a trip and once I was on my street getting ready to pull in, I pulled my park brake. To my supprise, the break was not holding the coach in place. Not a fast roll but just enough for one who operates a coach to notice...something not right. My thoughts,the park brakes slack needs to be adjusted which I can do. This said, my bus has DD3. Your thoughts is greatly worth while. | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1051 Registered: 12-2000 Posted From: 74.12.79.237 Rating: N/A |
The rear brakes in totality may be out of adjustment. The parking brake is not seperate. Check that first. Also means it won't stop right in a heavy brake situation. If the brake adjustment is tight, it gets more complicated...check that first. happy coaching! buswarrior | ||
| Ken Turner (Pipesusmc)
Registered Member Username: Pipesusmc Post Number: 74 Registered: 9-2002 Posted From: 71.113.38.234 Rating: N/A |
DOUG Below is a snip from my OLD web page "Nik Nik Turner certified Bus Mutt, he's on his way to the D O L to get his C D L he had stepped on the DD3 brake button while we were in a restaurant and as result had his first driving test in Oregon. I had to jump in the rolling bus and slapped my hand on the foot brake just as it rear ended a car and almost shoved everything into the front of the restaurant" The day after I bought the bus this happend on my way to the Seattle area. I had never heard of the DD3 brake system and the dealer never told me about how they differ from the from the air brakes which is used nowdays. (I had driven several semi trucks prior to the bus purchase, and assumed all brakes were the same)!!!! I think that when I PARKED the bus I did not press the foot brake nowhere near hard enough when I pulled the brake button, because that is not done on said trucks Maybe that was/is your problem. | ||
| Doug Ritter (Texrbama)
Registered Member Username: Texrbama Post Number: 21 Registered: 3-2007 Posted From: 206.138.130.3 Rating: N/A |
Thanks guys, I not to sure if I pressed the brake paddle down when I was parking /stopping. I was not rolling fast and on an slite incline. This is the very first time in seven years that the coach has acted this way. I have my brakes adjusted yearly due to the lack of traveling I do. However, now that I'm travel in the North East, hills and mountains, maybe the brakes got a good work out. Anyone know any good shops near East Ct., Danbury Ct., off I-84 as a back up. Thanks guys, | ||
| Jim Wilke (Pd41044039)
Registered Member Username: Pd41044039 Post Number: 160 Registered: 2-2001 Posted From: 69.77.156.44 Rating: N/A |
If the DD3 is operating correctly it WILL hold the bus. I would adjust the brakes first then see what you've got. I have needed to adjust the brakes after just a couple of days of mountain driving on my 4104, a real pain in the butt to do on the side of the road or a campground. But it's do-able if you run the bus up on blocks, then block the wheels AND the body on air suspension buses. Then make sure the brakes & parking brake are off, adjust the shoes out while tapping the edge of the drum. the drum will ring like a bell 'till the shoes contact it, then it just "clunks". Back the adjustment out 'till it just rings again and you're there. If you can, get someone to apply the service brake & measure the travel. Shorter the better without dragging. I think 2 inches is max due to the amount of travel of the brake can. | ||
| norcal kyle (Kylexisxrad)
Registered Member Username: Kylexisxrad Post Number: 170 Registered: 12-2005 Posted From: 76.105.27.223 Rating: N/A |
ken i, too, have an Eagle w/ DD3's and i have been taught to NOT step on the service brake full boar when applying the parking brake knob, only when releasing. it has to to with making the release easier. im not a brake expert by any means, so its hard for me to explain exactly why(even though it makes total sense in my head, i just cant connect my brain and the keyboard right now, lol). is there anyone here that can help? kyle in norcal 1980 Eagle 10 #30223 | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1052 Registered: 12-2000 Posted From: 74.12.75.211 Rating: N/A |
Hello. From a forensic standpoint, for any brake types, if you are having brake trouble, the first thing to do is MEASURE what you have for brake stroke, and then work from there. Otherwise, once the wrench has gone on, you have no idea what you really started with and may be chasing the wrong problem. For instance, glazed shoes, burned linings and leaking wheel seals make for poor brake friction, yet there will be good stroke. Save yourself some trouble, and identify good or bad stroke first. DD3 are good for 2 and 1/4 inches of applied pushrod stroke according to the regulations. Your fronts and tags will be something less than that, depending on the size of the chambers. A well adjusted brake, inside a round drum, with good bushings on the camshaft, will stroke around an inch. You might get just a little tighter if you can raise the wheel off the ground and spin it to be sure you aren't dragging the brake linings. If your adjustment measurement are longer than that after you have tried adjusting, you might want to have your brakes inspected by a pro to identify what is loose, worn or otherwise not letting you get a tight stroke. DD3 is supposed to apply with a regulated air pressure from the parking tank, when you apply the control knob up front. Pressure varies depending on coach and vintage. My 1975 MC8 is spec'd for 85 lbs. The DD3 parking feature will set and lock at whatever pressure is applied when it is parked. The trouble can be if you set the parking brake circuit while applying a heavy foot brake application, you will lock the parking mechanism quite tightly, then you will have a hard time applying the slightly higher squeeze needed to unlock the parking mechanism in the chamber when it is time to go driving again. Remember, you only have so much air pressure available to you, if you use it all to park, where are you going to find a higher pressure to unlock the parking mechanism? Folks, please be careful in what you subscribe to. DD3 seem to be one of the most misunderstood things out there, yet a ton of us have them as brakes on our coaches. The "advice" that may have been dispenced by helpful others, and indeed by bus fleet types too, must be regarded with suspicion unless you can find it in print from authoritative sources. This situation will only get worse, as the last of the new ones are approaching their half life with the front line carriers... happy coaching! buswarrior | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 706 Registered: 10-2003 Posted From: 71.58.117.21 Rating: N/A |
If the dd3's aren't holding you can have- out of adjustment brakes, bad parking diaphram that isn't applying proper pressure to pushrod, bad pushrod surface where rollers lock, corroded rollers that aren't locking properly, a lot of lost motion in brake bushings, badly worn brake camshafts in the bushing area, etc. causing a lot of lost motion,or grease on one or both brake drums.These are the most probable possibilities, although there are more remote ones. | ||
| Doug Ritter (Texrbama)
Registered Member Username: Texrbama Post Number: 22 Registered: 3-2007 Posted From: 68.247.196.99 Rating: N/A |
Ok guys, I'm headed up to a bus service center on Thursday.Not because I'm unable to adjust, I just want to be sur all is a-ok. the $$$ amount for a 37,000 pounds of knowing is worth it all. I will let you all know the outcome for furture Bus Nuts like me. what a great web site. Just as a side note, I named my coach..Drag~N~Fly She drags up one side of the mountain and flys down the other.  | ||
| Ken Turner (Pipesusmc)
Registered Member Username: Pipesusmc Post Number: 75 Registered: 9-2002 Posted From: 71.113.38.234 Rating: N/A |
Kyle.....When I got the bus home, one of the first things I did was to replace the DD3 system with spring brakes. So I never learned how to operate the DD3 brakes! | ||
| Doug Ritter (Texrbama)
Registered Member Username: Texrbama Post Number: 23 Registered: 3-2007 Posted From: 206.138.130.3 Rating: N/A |
Update, out of adjustment. While under the bus the service center did some minor repairs just to thigten up some of the slack on the slack. And yes, 30 DD-3 is somewhat out dated but they will have to do until I save enough for a major overhaul. Again, thanks guy for the info. | ||
| David Dulmage (Daved)
Registered Member Username: Daved Post Number: 171 Registered: 12-2003 Posted From: 142.46.199.30 Rating: N/A |
DD-3s work well and one advantage is that they can be disassembled without having to deal with the potentially lethal spring that is in spring brakes. I'm not aware of a special procedure for applying them as parking brakes; releasing them requires a full application of the service brakes however. DaveD | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1053 Registered: 12-2000 Posted From: 70.53.128.89 Rating: N/A |
Thanks for reporting back Doug! Glad it was relatively painless! happy coaching! buswarrior | ||
| RJ Long (Rjlong)
Registered Member Username: Rjlong Post Number: 1273 Registered: 12-2000 Posted From: 67.181.189.94 Rating: N/A |
David - Buswarrior covered setting the DD3 parking brake in his August 8th post above. In a nutshell: Apply the parking brake while using just enough service brake pressure to keep the bus from rolling (no service brake at all if possible). Simple, eh? Doug - Now you know the importance of keeping an eye on brake adjustment, eh? (PS: IF you'd been doing your pre-trip air brake check properly, you'd have found this problem a lot sooner!! Check the "Articles of Interest" section of this BBS for details.) FWIW & HTH. . . (Message edited by rjlong on August 09, 2007) | ||
| norcal kyle (Kylexisxrad)
Registered Member Username: Kylexisxrad Post Number: 172 Registered: 12-2005 Posted From: 76.105.27.223 Rating: N/A |
RJ: thats exactly the post i was thinking of. i just couldnt think of the way to word it. Ken: sometimes i wish i didnt have the DD3's and my bus let out a big rush of air when i set the parking brake. just seems like more majestic way to pull into a campground. lol kyle in norcal 1980 Eagle 10 #30223 | ||
| Hans (Buellhans)
Registered Member Username: Buellhans Post Number: 75 Registered: 2-2007 Posted From: 199.60.189.9 Rating: N/A |
DD3 brakes need an aplication to apply ,dont mat it because if you apply 50lbs it will need 60 to release them . If you dont know if the brakes need adjusting you souldnt be driving air brake unit . Part of the pre trip inspection you should do before you go on a trip . DD3 are great units and the spring brake chambers you can rebuild them as well but dont forget to cage the springs | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 252 Registered: 8-2006 Posted From: 207.231.81.129 Rating: N/A |
I don't want to get into a contest with Hans, BUT, no way do you do anything other than pull the knob to apply DD3s. Period. If you have to step on the service brake to get the DD3s to hold, SOMETHING IS WRONG! The DD3 system has a seperate emergency/parking reservoir, seperate valving system, seperate diaphragm, and seperate latching control from the service brakes. The DD3 knob will pop up by itself if the service air pressure falls below about 90 psi. Holding the knob down won't cause a release with low air pressure either, as the inversion valve won't allow it. I didn't want to beat Doug up in his own thread, and since RJ has said it all, exactly correct, I won't have to! Kyle and the Buswarrior are also right on, and lets think about something else here. We all know that the brake drums on drive axles are essentially TWICE the width of the steer and tag axles, because they have two tires, and two times the weight, right? Just maybe they do twice the work???? Now if the drive axle brakes were so far out of adjustment that neither of them worked, what about the steering and tags???????? This seems to be to me like a rear end collision just about to happen. I won't even mention a SMALL hill! DD3 operation, and emergency stopping distance, is in the archives, along with a video comparing emergency stopping distances from a full foot pedal application, and just "popping the knob." As DD3s hold all of the application force with a mechanical latch, it takes slightly more force (total force, service + parking) to release them. This is where the complaint about "failure to release," comes from. If the knob is pulled while the pedal is depressed, service force is added to parking force, which must be overridden to get a release. A simple test is to pop the knob at one or two MPH. If the bus doesn't stop immediately, something is wrong, if its LACK of adjustment, SHAME ON YOU! I didn't even ask how many miles, or years it has been since these brakes were looked at last... Sorry to beat you up in your thread, and I hope a few other people will crawl under and look because of this! George (Message edited by George Mc6 on August 14, 2007) | ||
| Jim Wilke (Pd41044039)
Registered Member Username: Pd41044039 Post Number: 166 Registered: 2-2001 Posted From: 68.187.183.190 Rating: N/A |
Hans, while it is really important to cage the spring on spring brakes before removing the can from the vehicle, you can not rebuild a recent spring brake can. They no longer are fastened together with removeable fasteners. They are crimped together with some HUGE press. Even if you cut one open, there's no way to put it back together. But they are so cheap it doesn't matter. The last ones I bought about 3 years ago were $39 each! | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1055 Registered: 12-2000 Posted From: 74.12.73.40 Rating: N/A |
In shorter words, George is telling you that a DD3 makes its own application when you pull the knob. Leave the brake pedal alone. And I will echo: When was the last time you (any of us) actually did what is right, and crawled under there and measured the applied pushrod stroke? Never mind having a look around for leaking seals (adding some lube to your brake linings doesn't help get you stopped) and all the curious other things one finds if one has a look underneath... Who would bother rebuilding a spring brake chamber, exposing oneself to that danger, when the replacement units are almost as cheap as the parts? Please, just buy new ones and have the old ones properly decommisioned so they don't explode in the dump, hurting someone. happy coaching! buswarrior | ||
| Doug Ritter (Texrbama)
Registered Member Username: Texrbama Post Number: 28 Registered: 3-2007 Posted From: 68.247.13.4 Rating: N/A |
Doug - Now you know the importance of keeping an eye on brake adjustment, eh? (PS: IF you'd been doing your pre-trip air brake check properly, you'd have found this problem a lot sooner!! Check the "Articles of Interest" section of this BBS for details.) Thanks for busting my balls (FWIW) concerning the pre trip brake check. For the record, I do go over my coach before,during and after each trip. Do we catch every issue...no. That's why I ask, seek and take advice from more then one. None the less, problem found, solved and had a wonderful trip up in the mountains this past weekend. As a matter of fact, parked my rig with six other coaches and all wanted to board our rig. Made us prouud to be the owner and operator of the Eagle. |