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07-14-2014, 07:29 AM
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#1
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Senior Member
Monaco Owners Club Freightliner Owners Club
Join Date: Oct 2009
Location: Arlington, VA
Posts: 1,043
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Apply EMERGENCY brake "at speed" ??
I'd like to hear experiences or opinion as to what happens if you apply the Emergency / Park Brake while traveling "at speed" (45, 65 MPH range). Does the brake lock the rear wheels (dangerous !!!). If on cruise control, does CC disengage?
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Robi & Dale ---- Go Navy ----
2016 Winnie TOUR 42'
Tow: '19 Buick Envision
or: '08 Buick Lucerne
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07-14-2014, 07:32 AM
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#2
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Senior Member
Join Date: Apr 2012
Location: Louisville, KY
Posts: 1,489
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I've applied mine for testing purposes at around 15-20 mph. It slowed me down real quick, but didn't lock the wheels.
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Mark Anderson - FMCA 351514 - NRVIA Certified Level 2 Inspector
Louisville, KY
2011 Tiffin Phaeton 40QTH
2006 Jeep Commander
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07-14-2014, 07:35 AM
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#3
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Senior Member
Tiffin Owners Club
Join Date: Jun 2013
Location: Western NC
Posts: 595
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At Camp Freightliner they show a short video clip of Freightliner test folks doing exactly that. It will stop the coach rapidly, but it doesn't lock the rear wheels.
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Seeing this country from ground level.
2016 Allegro Bus 40AP
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07-14-2014, 07:40 AM
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#4
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Senior Member
Winnebago Owners Club
Join Date: Apr 2005
Location: Texas
Posts: 2,481
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Not sure exactly why you are asking, but in an actual emergency situation, seems the application of brakes via the brake pedal would provide the most effective stop.
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Warren and Debbie, Deep in The Heart of Texas
2018 Winnebago View 24D
2014 Tiffin Breeze 32BR, 2012 Winnebago Navion 24G, 2006 Winnebago View 23H
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07-14-2014, 07:55 AM
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#5
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Senior Member
Ford Super Duty Owner
Join Date: Jan 2011
Location: Lowell, Arkansas
Posts: 7,303
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The auto industry has learned that locking wheels does not stop a vehicle sooner. Brakes are designed to convert energy of motion into heat energy. More heat is generated by correctly working brakes than tires skidding or sliding on pavement.
Would the EB lock the wheels?? No.
I don't know what other chassis use for an EB but the F-53 uses a small drum brake assembly around the drive shaft. It is operated by a mechanical lever and a cable. It will provide one additional brake besides the other four. It is a drum brake which don't work very well. The other four brakes are disc/hydraulic and they will provide significantly greater stopping power than the EB brake.
IMHO! The phrase emergency brake or also called a parking brake is a phrase used for a long time. It really should be called a parking brake. I don't really believe it was ever intended to be used except for parking and in the event you lost either your front or rear brakes. In that situation it will slow you down but not very well. The dual master cylinder has been around since the last 50's or early 60's. In the event of a hydraulic leak (past the master cylinder) you only loose two wheels. So the EB/PB still has two wheels working to help.
I have never used an EB in an emergency but rest assured it won't lock up any wheels.
TeJay
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TeJay Auto Instructor/4-yrs USAF/ Liz: RN/ WBGO 2014 Vista 30T/ F-53/CHF/5-Star/Koni * Bella & Izzy * Golden /Cocker mix/ Louie The Cat* All Retired
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07-14-2014, 08:19 AM
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#6
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Senior Member
Join Date: Apr 2012
Location: Louisville, KY
Posts: 1,489
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I think the OP was referring to an air brake, not a cable brake.
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Mark Anderson - FMCA 351514 - NRVIA Certified Level 2 Inspector
Louisville, KY
2011 Tiffin Phaeton 40QTH
2006 Jeep Commander
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07-14-2014, 08:36 AM
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#7
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Senior Member
Winnebago Owners Club
Join Date: Aug 2002
Location: Indian River, De
Posts: 1,024
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On a coach with air brakes, pulling that big yellow knob, will apply the rear brakes, and bring the coach to a (probably not very rapid) stop. If there were a sudden loss of air pressure while driving the motorhome, the rear brakes will be applied automatically, as it takes air pressure above 50 psi, to keep them released.
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CaptBill
USAF 1965-1971; USCG Master
2002 Horizon 36LD
Indian River, De
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07-14-2014, 08:44 AM
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#8
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Senior Member/RVM #90
Monaco Owners Club
Join Date: Nov 2002
Location: Columbus, MS
Posts: 54,794
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Joe & Annette
Sometimes I sits and thinks, sometimes I just sits.....
2002 Monaco Windsor 40PBT, 2013 Honda CRV AWD
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07-14-2014, 08:55 AM
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#9
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Senior Member
Join Date: Nov 2008
Location: Cosby, Tn
Posts: 6,587
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Quote:
Originally Posted by MSHappyCampers
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Actually, pulling out that big button dumps the air from the big air brake chambers on the drive axle. The ones back there have a second part and when the air pressure drops below a certain point, large, heavy springs engage and cause the drive axle brakes to be applied.
Steve Ownby
Full time since '07
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Steve Ownby
Full time since 2007
2003 Monaco Signature
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07-14-2014, 09:03 AM
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#10
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Senior Member
Join Date: Oct 2012
Posts: 2,328
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At a driving school the question was asked what to do if the driver becomes incapacitated. Answer was for the copilot to grab the wheel and pull the park brake. Don't try and use the foot brake while standing up, perhaps supporting the driver, and steering the MH.
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Paul, Kathy, and Tux the Mini Schnauzer
2014 Tiffin Phaeton 42 LH, 2013 Honda CRV
"When the time comes to look back, make sure you'll like what you see"
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07-14-2014, 09:06 AM
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#11
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Senior Member
Solo Rvers Club
Join Date: Jul 2014
Location: Ham Lake, MN
Posts: 3,038
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Quote:
Originally Posted by MSHappyCampers
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Joe,
CaptBill is right. The air brake chambers on the rear axle are spring loaded, not just a "pancake" type chamber requiring air to apply the service brakes, but an additional chamber that contains a very heavy spring. When you release the air brakes you charge that extra cylinder to pull the actuator rod back from the service brake pancake. When you set the PB/EB the spring in the chamber reapplies that rod to the pancake thereby actuating the brake rod. They are installed on the rear axle as this will stop the vehicle in the safest manner. This is the reason when towing a vehicle with the rear axle on the ground the brake chambers need to be "caged" (manually released with a special T bolt) to release the spring from the service brake pancake.
Some, not all, vehicles that use hydraulic brakes may have a drum or band type brake at the rear of the transmission that will have the same effect. Others use a cable arrangement to actuate the brake shoes on the rear axle.
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Have a wonderful day!
Ken (RVM 87)
FT DP Wanna B The journey is the destination!
Retired & perfecting procrastination!
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07-14-2014, 01:25 PM
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#12
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Senior Member
Damon Owners Club Workhorse Chassis Owner
Join Date: Mar 2009
Posts: 24,024
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Alot depends on the vehicle,,
Gas motor homes with drive shaft braking: SLOWS the vehicle, will not lock 'em up not powerful enough to do that.
Diesels with air brakes, blown air tank.. See above, Brakes are powerful enough but springs that set them,,, not so much.
Cars.. On a car and most pickups the emergency brake is the same as the service brakes, only operated mechanically instead of hydraulically, so they ARE powerful enough to lock the rear wheels and initiate panavision In fact this is used in Genuine Chauffer's training schools (NOT the one that teaches truck driving but the one that teaches how to protect a VIP when terrorists try to kidnapp him from the LIMO you are driving)
Fact is.. A really good VIP chauffer... The kidnappers might just end up .. "Retired" as it were, from the kidnapping business (And the breathing business) when the smoke clears.
(The smoke, made by the spinning tires on the limo, having obstructed the attacker's view of the sign and the guard rail, causing them to miss the curve and .. Well, it was a high cliff and when they got to the bottom .. they were "Retired".)
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Home is where I park it!
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07-14-2014, 01:46 PM
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#13
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Senior Member
Join Date: Jan 2010
Posts: 474
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Your coach does not have an 'emergency brake' It has a parking brake whose sole design purpose is to keep and parked coach stationary without driver involvement.
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38ft 2008 Damon Daybreak 3575 (forward kitchen)on Ford 22,000lb chasis, 242" WB.
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07-14-2014, 02:11 PM
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#14
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Senior Member
Ford Super Duty Owner
Join Date: Jan 2011
Location: Kitts Hill, OH
Posts: 2,252
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Quote:
Originally Posted by Selah
At a driving school the question was asked what to do if the driver becomes incapacitated. Answer was for the copilot to grab the wheel and pull the park brake. Don't try and use the foot brake while standing up, perhaps supporting the driver, and steering the MH.
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I have told a few of my More responsible students on my School Bus that very thing with the caution they get(sit) on the floor first.
Quote:
Originally Posted by wa8yxm
Alot depends on the vehicle,,
Gas motor homes with drive shaft braking: SLOWS the vehicle, will not lock 'em up not powerful enough to do that.
Diesels with air brakes, blown air tank.. See above, Brakes are powerful enough but springs that set them,,, not so much.
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I don't buy for a second the emergency (parking brake) on a air brakes vehicle won't lock the rear wheels.
Whether or not he wheel lock depend on several factors.
First the ABS is not hooked to the parking brake function.
The weight on that axle, brake adjustment, road condition,(Dry,Wet,snow covered,Ice) tire tread.
I Am positive they would lock on mine. 8K-9K lbs on a 20K lbs axle, brakes have 4000 miles on them, and they are adjusted up the way they should be.
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(RVM#26) THE U-RV 94 F-700/24 foot U-haul box home built RV
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