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07-08-2019, 10:27 AM
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#1
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Senior Member
Country Coach Owners Club
Join Date: Aug 2017
Location: Fort Smith, AR
Posts: 307
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DOT brake fitting failure at 60mph
The brass elbow came apart while traveling 60 mph on I29 near Omaha. The brakes locked the right rear Tag an wore it through in seconds. My wife managed to pull to the shoulder where we waited (1 foot from the white line) 7 hours for Progressive pro roadside assistance. (press
You see in the attached picture the 1/2 npt part came out of the elbow part. I do not see what held them together. It just slips in and out. there is an Oring in the elbow but i see no mechanical retention feature that failed. Perhaps the failed portion disappeared.
You can see on the elbow a symbol which i guess represents the manufacturer's logo. I would very much like to see and understand the feature that held it in and failed.
any help?
__________________
Wendell
CC 630 Magna
BMW R1200RTLC
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07-08-2019, 10:46 AM
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#2
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Senior Member
Monaco Owners Club
Join Date: Aug 2017
Location: Orlando, Florida
Posts: 5,819
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I'm not a fan of those Push-to-Connect fittings because the o-ring will eventually leak and it can't be replaced. Those P-T-C fittings are only good for assembly line workers. IMO
The P-T-C fittings (if made by reputable company like Parker) are pretty robust. I have not seen or heard of one coming apart like yours. But since those fittings have the "extra machining" (for the swivel and o-ring) it adds an additional point of failure.
Of course any fitting can fail. I always replace the P-T-C fittings with a standard DOT air-brake compression fitting when I have to replace one for leaking.
I suppose it is a good idea to go under the coach during your annual inspection and grab/wiggle all the brake fittings to check for any pending failures.
P-T-C fittings on top, and standard compression fittings in the middle and bottom of photo.
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07-08-2019, 02:22 PM
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#3
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Senior Member
Country Coach Owners Club
Join Date: Aug 2017
Location: Fort Smith, AR
Posts: 307
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the push to connect feature end is not the one that failed. the failure is on the NPT end.
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Wendell
CC 630 Magna
BMW R1200RTLC
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07-08-2019, 04:34 PM
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#4
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Senior Member
Monaco Owners Club
Join Date: Aug 2017
Location: Orlando, Florida
Posts: 5,819
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But it is the same fitting.
A P-T-C swivel fitting has two o-rings inside and a gripper to hold the hose, so it has more parts to fail than a standard compression fitting.
But they lasted 14 years (at least on my coach - you didn't say the age of your coach) before some started leaking, so if you want to use the style again I think you will be fine for the rest of the coach's life.
good luck
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07-09-2019, 09:38 AM
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#5
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Senior Member
Entegra Owners Club
Join Date: Jun 2004
Location: Bayfield, Ontario
Posts: 5,456
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Glad you found the problem. I am curious, what caused your right tag wheel to lock up?
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Don & Gerri
2014 Entegra Anthem 44B
2014 Honda CRV Touring
1300W Solar, 1200AH LiFePO4 FMCA F443497
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07-10-2019, 03:52 PM
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#6
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Senior Member
Country Coach Owners Club
Join Date: Aug 2017
Location: Fort Smith, AR
Posts: 307
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brakes on an air system are clamped down by springs. When you press on the brake, air is let off at the wheel cylinders and the springs clamp the brake according to the remaining air pressure. Let up on the brake and the increased air pressure opens the springs to allow rotation. When the Tag air line came apart, the air holding the tag brake escaped first and the springs clamped on the brakes. You wont believe what that did to the NEW 550$ tag. I will attach a pic.
__________________
Wendell
CC 630 Magna
BMW R1200RTLC
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07-10-2019, 04:05 PM
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#7
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Senior Member
Entegra Owners Club
Join Date: Jun 2004
Location: Bayfield, Ontario
Posts: 5,456
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Quote:
Originally Posted by wsmcycle
brakes on an air system are clamped down by springs. When you press on the brake, air is let off at the wheel cylinders and the springs clamp the brake according to the remaining air pressure. Let up on the brake and the increased air pressure opens the springs to allow rotation. When the Tag air line came apart, the air holding the tag brake escaped first and the springs clamped on the brakes. You wont believe what that did to the NEW 550$ tag. I will attach a pic.
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I see. Thought the spring brake was usually on the drive axle and not the tag axle. I guess yours is different.
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Don & Gerri
2014 Entegra Anthem 44B
2014 Honda CRV Touring
1300W Solar, 1200AH LiFePO4 FMCA F443497
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07-10-2019, 04:11 PM
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#8
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Senior Member
Join Date: Jul 2014
Posts: 35,349
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Your explanation of how air brakes work is not correct.
Air pressure applies the brakes, to all wheels, when you step on the brake pedal.
Rear brakes ( typically only the drive axle ) have dual chambers with spring sections that apply the brakes when air pressure is lost or the parking brake is applied.
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07-10-2019, 04:31 PM
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#9
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Senior Member
Join Date: Mar 2011
Posts: 681
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Twinboat is correct. Pressing on the brake pedal applies air pressure to the brake cylinders to stop the coach. This is the service brake system.
If the air pressure drops out of the system, the springs clamp the brake shoes to the brake drums.
Just like when you park your couch, pull the yellow brake valve which drops the air pressure out of the system to set the brakes for parking.
Great system.
Regards,
JimB
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07-10-2019, 05:38 PM
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#10
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Senior Member
Join Date: May 2019
Posts: 2,392
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Did the brakes apply to your drives as well? I'm wondering if the tag locked up and not the drive axle because it's carrying much less weight than the drive.
__________________
Richard
1994 Excella 25-ft (Gertie)
1999 Suburban LS 2500 w/7.4L V8
1974 GMC 4108a - Custom Coach Land Cruiser
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07-15-2019, 04:32 PM
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#11
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Senior Member
Country Coach Owners Club
Join Date: Aug 2017
Location: Fort Smith, AR
Posts: 307
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I am embarrassed by my ignorance. I am glad to have been straightened out.
The failed fitting was part of the right-side tag brake. I do not know why the other brakes did not clamp but the tag sure did.
thanks
__________________
Wendell
CC 630 Magna
BMW R1200RTLC
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07-15-2019, 04:39 PM
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#12
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Senior Member
Country Coach Owners Club
Join Date: Aug 2017
Location: Fort Smith, AR
Posts: 307
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My original question was directed at the failure of the swivel joint on the NPT end, not PTC female on the opposite end. I can appreciate the disdain for the PTC end but that end did not fail. what was the design of the swivel joint? any drawings available?
__________________
Wendell
CC 630 Magna
BMW R1200RTLC
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