Community Forums

G Schulz · 06-19-2016, 08:26 AM

Quote:

Originally Posted by Mike_Harriet

Anyone ever set the brake when still slightly rolling, to see if they really lockup. How quickly they activate would be interesting.

Sent from my iPhone using iRV2 - RV Forum

Never done it but they will lock up right away. Everyone driving a coach with air brakes should take an air brake class. It is a requirement in Alberta and should be everywhere.

2009 Safari Cheetah 40'
350 HP Cat
2014 Ford Focus
Air Force One

JFXG · 06-19-2016, 08:58 AM

Quote:

Originally Posted by Mike_Harriet

Anyone ever set the brake when still slightly rolling, to see if they really lockup. How quickly they activate would be interesting.

Sent from my iPhone using iRV2 - RV Forum

Just to be clear, it is only the emergency/parking brake that is activated by lack of air pressure and released by the application of pressure, and the E-brake applies only to the rear axle. The service brakes on all four wheels apply with the presence of pressure and deactivate with the release of pressure.
As to the ebrake application when rolling, yes, I've done it, from about 20 mph. What you get is a very firm, continuous application of the ebrake until the coach is stopped. On my coach nothing locked up, no screech of tires, no stuff flying around inside. All that would cause more problems than it solved. Probably worth doing in a parking lot somewhere, just for familiarity. One caveat: my coach is always at max gross weight. If you're significantly under your GVWR you may get some rear wheel lockup. Be advised.

John & Diane, fulltiming since '12 02 DS, FL, Cat, '04 Element NHSO RVM103

MSHappyCampers · 06-19-2016, 12:46 PM

Quote:

Originally Posted by jondrew

I store my Discovery about a mile from my house. It's a pretty quick pick up when I want to do some work on it. Today I drove it to the house to wax the 2nd half (did the front and passengers side last week). I parked in front of the house where I had some nice shade, turned it off and got to work. Just as I finished the storms started rolling in. I cleaned up my stuff, got in the MH to drive it back and started it up. Immediately I heard an alarm. No air pressure? Nope, that was fine. Some engine alarm? Nope, not that. Finally I realized what it was; I had put the coach in neutral and had shut it down without putting the parking brake on. It had been sitting out in front of the house all day like that. My street has the slightest of inclines and I'm kind of suprised it never started rolling away. I got real lucky and hopefully will learn something.

WOW! That's SCARY!

tim myers · 06-19-2016, 01:07 PM

You should see the springs that apply the braking force. I met one of these Springs in a way you would not want to experience when working at a truck stop as a mechanic. They call it a maxi spring.

twinboat · 06-19-2016, 01:28 PM

Yes, it a very heavy spring. Back in the day, we used to cage the brake pot and change the diaphragm.

Once in a while, the spring would be broke and the sharp end, trying to get out, is what poked the hole in the diaphragm.

Talk about a tiger by the tail !!

On another note, it takes 60 psi to fully release the spring brake.

So, it stands to reason, that it can only apply the equivalent of 60 psi of pressure, of brake applacation, and that's on the rear axles only.

Stepping on the brake will give you double that force and on all wheels.

With half the avalable force, your not going to lock up the wheels on a loaded MH.

tim myers · 06-19-2016, 08:18 PM

I was a young 17 year old and thought I was opening up to change a leaking pancake. Big surprise when it flew out of the housing and slammed my arm up against the fuel tank. If it had hit my head I wouldn't be tying this.

tim myers · 06-19-2016, 08:19 PM

Or typing even

bluepill · 06-19-2016, 08:27 PM

Freight train going into emergency is even more fun.

(Start at 1:40)

https://youtu.be/6YOD1gC00LQ

Rich-n-Linda · 06-19-2016, 10:10 PM

Quote:

Originally Posted by G Schulz

Never done it but they will lock up right away. Everyone driving a coach with air brakes should take an air brake class.

No, the parking brake will NOT lock up the rear wheels. And if YOU had taken an air brake class, you would know that. That is bad and potentially dangerous information.

I purposely engaged the parking brake on our Mandalay at 50 mph so I could see what to expect if I ever had to use it in an emergency. The coach stopped about the same as a hard stop with the service brakes, with NO wheel lock ups. The springs are not that strong. The final stop was fairly abrupt because the emergency brake doesn't feather off as you would do when using the service brakes. But nothing moved inside the coach and we stopped just fine. It wasn't a big deal.

Now I know what to expect if I ever lose my air and have to use it to stop.

DeWat · 06-20-2016, 07:07 AM

Quote:

Originally Posted by Rich-n-Linda

...
Now I know what to expect if I ever lose my air and have to use it to stop.

I think I know what you are trying to say, but if you ever lose your air, you won't have to use it... it will stop.

G Schulz · 06-20-2016, 08:47 AM

Quote:

Originally Posted by Rich-n-Linda

No, the parking brake will NOT lock up the rear wheels. And if YOU had taken an air brake class, you would know that. That is bad and potentially dangerous information.

I purposely engaged the parking brake on our Mandalay at 50 mph so I could see what to expect if I ever had to use it in an emergency. The coach stopped about the same as a hard stop with the service brakes, with NO wheel lock ups. The springs are not that strong. The final stop was fairly abrupt because the emergency brake doesn't feather off as you would do when using the service brakes. But nothing moved inside the coach and we stopped just fine. It wasn't a big deal.

Now I know what to expect if I ever lose my air and have to use it to stop.

I did take the air brake course and it is a very large spring that activates the brake. Just assumed it would lock up but I guess there is a lot of weight holding the unit to the road to lock them. In the class they said if you start losing air to pull over and apply the service brakes in one application.

2009 Safari Cheetah 40'
350 HP Cat
2014 Ford Focus
Air Force One

ByeTheWay · 06-20-2016, 05:03 PM

Thanks for the info Rail. It all makes more sense now.

Mr_D · 06-20-2016, 05:13 PM

Quote:

Originally Posted by Mike_Harriet

Anyone ever set the brake when still slightly rolling, to see if they really lockup. How quickly they activate would be interesting.

That's one of the tests you're supposed to perform at least weekly if not more often. IF you try it you better have stuff "battened down" if they're working correctly. They won't quite lock the wheels up but should come close.

Atom Ant · 06-20-2016, 05:16 PM

Quote:

Originally Posted by jondrew

I store my Discovery about a mile from my house. It's a pretty quick pick up when I want to do some work on it. Today I drove it to the house to wax the 2nd half (did the front and passengers side last week). I parked in front of the house where I had some nice shade, turned it off and got to work. Just as I finished the storms started rolling in. I cleaned up my stuff, got in the MH to drive it back and started it up. Immediately I heard an alarm. No air pressure? Nope, that was fine. Some engine alarm? Nope, not that. Finally I realized what it was; I had put the coach in neutral and had shut it down without putting the parking brake on. It had been sitting out in front of the house all day like that. My street has the slightest of inclines and I'm kind of suprised it never started rolling away. I got real lucky and hopefully will learn something.

Almost....