| Author | Message | ||
| John Jewett (Jayjay)
Registered Member Username: Jayjay Post Number: 369 Registered: 1-2001 Posted From: 70.249.224.160 Rating: |
Mark, the next time you "park" your Beast, do a service brake application and get system pressure down to about 95 PSI. THEN set the Parking Brake. That way you can readily overcome the residual parking brake pressure with your service brake the next time you start up. Unless it's sitting on a really steep grade 90 to 95 PSI will hold the coach quite well-put less strain on your shoes and diaphragms, and be far easier to release. Cheers...JJ | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 139 Registered: 8-2006 Posted From: 207.231.81.49 Rating: N/A |
ASSUMING Mark's bus has DD3s, this advice won't work, as the DD3 parking/emergency application reservoir has a check valve in the inlet line to it, and should stay at the highest pressure developed by the air system. The air pressure as indicated by the gauges will cycle as the compressor cuts in and out, but the emergency application reservoir is protected by a check valve to protect against loss of air in case of a failure in the air system anywhere between the compressor, the first tank, and the auxiliaries,etc. The way to protect against DD3s not wanting to release is to have NO SERVICE BRAKE PRESSURE applied when you pull the park knob. In other words, don't have your foot on the brake pedal when you pop the knob. This is also a good test of the parking portion of the system. If you release the foot brake and pop the knob on a grade, the bus should move a foot or so and stop, if it doesn't, you have a problem. DD3s have to apply the brake linkage slightly more to release the mechanical latch, which is why the instructions to apply the service brakes AFTER pushing in the knob are published. This increases the application force enough to release the latch. If that application force was already there, (service + parking) when the bus was parked, and some warm brake drums cooled off and contracted, = stuck brakes? The trick to releasing stuck DD3s, provided it isn't a control failure, is to get the bus to maximum air pressure, push the knob, apply full service pedal pressure, wait about two or three seconds, release and see if it worked. If not, have full reservoir pressure, pull the knob, let the emergency chambers charge fully, apply full service pedal, and about a second later, push the button, wait 3 or 4 seconds, release the pedal, and hope. (I know, I just told him to do what I told him not to when he parked, but this adds both chambers' effort to the application force, and hopefully the timing of the latch release is just before maximum force, and a release occurs. If not, they are really stuck!) HTH!, George | ||
| mark (Coolbus)
Registered Member Username: Coolbus Post Number: 39 Registered: 7-2006 Posted From: 71.54.203.149 Rating: N/A |
Thanks for the suggestion, JJ I'll give that a try next time. George... I sorta hate to show my ignorance...how do I tell if I have DD3 brakes? thanks! Mark | ||
| Ed Jewett (Kristinsgrandpa)
Registered Member Username: Kristinsgrandpa Post Number: 312 Registered: 2-2003 Posted From: 64.24.214.254 Rating: N/A |
Mark, here is a link to a website that has all sorts of info about airbrakes. I've had it stored for a year or so but haven't had time to look through it.(I'm busy converting a coach) http://www.bendix.com/bendix/downloads/air_brake_handbook/BW5057_online.pdf Ed | ||
| norcal kyle (Kylexisxrad)
Registered Member Username: Kylexisxrad Post Number: 144 Registered: 12-2005 Posted From: 75.5.251.60 Rating: N/A |
from what ive gathered(and please spare me if im wrong, i just drive, im still in the learning curve..), this is the layman's tell tale: if you have to make a full service brake(foot pedal) application after releasing the parking brake knob to completely disengage the parking brake, then you have DD3's. you should probably consult da book to be absolutly sure. on my Eagle, right above the knob there are instructions telling you to make a 100 psi foot valve application before moving the coach. hope i helped a little.... kyle in norcal 1980 Eagle 10 #30223 | ||
| Richard Bowyer (Drivingmisslazy)
Registered Member Username: Drivingmisslazy Post Number: 1890 Registered: 1-2001 Posted From: 75.108.86.176 Rating: N/A |
Strange. My 80 Eagle 10 I only had to pull the knob to set and push it to release. Maybe someone changed them out before I got it? Richard | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 140 Registered: 8-2006 Posted From: 207.231.81.49 Rating: N/A |
This is a chance to answer two questions with one post, easy! My MC6 definitely has DD3s, and fortunately I have never had trouble with a release, and apparently I am one of the lucky few. Anyhow, the easy way to tell if it is DD3s or maxis, (springs) is on the parking application. Maxis exhaust all the spring opposition air from the second chamber thru the relay valve exhaust port. This is LOUD and obvious, and will blow dust, etc. DD3s apply essentially silently, the only exhaust is from the latch cylinder, as the parking/emergency cylinder is charged on application. The hard way is to go under and count hoses on the drive cans. Two if by maxi, three if by DD3, said Paul Revere. If you don't have an Eagle, BLOCK IT UP FIRST! Richard, your driving habits probably save you, I can only guess you never set the parking brake with your foot all the way down on the pedal? At the price of a rebuilt DD3 can, I wouldn't blame somebody for changing them out. George | ||
| Jack Conrad (Jackconrad)
Registered Member Username: Jackconrad Post Number: 564 Registered: 12-2000 Posted From: 76.1.180.218 Rating: N/A |
On the buses I have seen/driven, the buses with DD3 brakes had a black round knob to set/release the parking brake. The buses with maxi(spring) brakes had a six sided yellow knob to set/release the parking brake. I am sure there are probably exceptions, but that has been my experience. Jack | ||
| Mark R. Obtinario (Cowlitzcoach)
Registered Member Username: Cowlitzcoach Post Number: 140 Registered: 4-2001 Posted From: 204.245.228.213 Rating: N/A |
I have seen just about every shape and size knob for parking brake applications. The most common were round and black or square and yellow. Some were DD3, some were not. Since Mark has a Gillig that was formerly a school bus, I would venture a guess he has spring brakes and not DD3's. I could be wrong of course but I have never seen a Gillig with DD3's. Even the really old Gillig buses I have seen that had driveline parking brakes did not have DD3's. When the rules changed and the school buses were retrofitted to a better emergency brake, spring brakes were retrofitted. Again, I could be wrong but I seriously doubt Mark's Gillig has DD3's. Our church has a 1979 Gillig and it has a single round black knob and it has spring brakes. Just my $0.02 worth. Mark O. Castle Rock, WA | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 545 Registered: 10-2003 Posted From: 71.58.117.21 Rating: N/A |
dd3's have 3 hoses, maxi's have two. Third port applies air to lock port. | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1007 Registered: 12-2000 Posted From: 74.12.80.105 Rating: N/A |
Hello. Info here so far on DD3 is accurate. DD3 have problems when the maintenance hasn't been done. No grease to the locking rollers in the chamber, inversion valve and/or pressure regulator on parking circuit old, leaking, corroded... A frequent problem when busnuts don't do the maintenance, or the fleet before us didn't do the maintenance, or both... And a spring brake retrofit won't work on most MCI because there is no space to fit a spring brake chamber's mother of 6 children big backside into the axle space intended for the sexy and yet to be spoiled tush of a DD3. And of course, one must properly diagnose whether one's lack of movement is due to an air system valving problem, or the linings rusted to the drums. Sometimes you need a hammer, sometimes you need a spanner? happy coaching! buswarrior | ||
| Tom Hamrick (Tomhamrick)
Registered Member Username: Tomhamrick Post Number: 73 Registered: 12-2000 Posted From: 167.83.101.23 Rating: N/A |
The model 10 Eagle has spring brakes but also includes an air relay in the circuit that requires the 100 pound application to release the spring. I was told this was a safety feature to prevent a passenger from pushing the release button in and start the bus rolling if the driver was unloading luggage. Tom Hamrick 1984 Eagle 10S |
