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Author Topic: Bendix BVA-85 brake valve actuator  (Read 3916 times)

Offline Iceni John

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Bendix BVA-85 brake valve actuator
« on: March 15, 2013, 12:27:52 PM »
I was reading through the Bendix Air Brake Handbook (yes, I know I'm weird to actually read things like that), and for pre-trip safety inspections it mentions a BVA-85 brake valve actuator.   The handbook says it "enables pre-trip brake inspections safely and easily with only one person.   It uses air from the trailer supply of the Bendix MV-3 valve to keep the foot pedal applied at an accurate 85 PSI service brake application."   I don't have a MV-3, but I do have an accessories air reservoir with a PR-3 valve.   I also have a brake application force dual pressure gauge, but that doesn't help me if I'm alone when I'm checking the brakes.

Does anyone here have one of these BVA-85 on their bus?   Without one, how would I apply the recommended 85 PSI brake force to accurately check the pushrods' extension and the slack adjusters?   Would it be OK to jam the brake pedal down with a stick to maintain 85 PSI application force, or is that too redneck?   I don't have automatic slack adjusters, but even though I don't drive much now while I'm converting the bus I want to be sure that my entire braking system is always 100% safe and functional.

I'm sorry if this seems like a silly question, but I take brake system safety to be of paramount importance, even if driving only a few hundred miles a year now.   Am I being too obsessive about this?

John
1990 Crown 2R-40N-552 (the Super II):  6V92TAC / DDEC II / Jake,  HT740.     Hecho en Chino.
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Offline luvrbus

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Re: Bendix BVA-85 brake valve actuator
« Reply #1 on: March 15, 2013, 12:39:06 PM »
School buses use BVA-85 valve actuator without the MV-3 fwiw
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Offline Iceni John

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Re: Bendix BVA-85 brake valve actuator
« Reply #2 on: March 15, 2013, 12:51:10 PM »
Yes, the Bendix handbook mentions that schoolbuses can use this valve, presumably to keep the brakes applied untill all doors are closed.   However, my bus's air system schematic doesn't show such a valve anywhere, and the emergency door and window each have switches to sound a LOUD buzzer if they're not fully closed.

Thanks, John   
1990 Crown 2R-40N-552 (the Super II):  6V92TAC / DDEC II / Jake,  HT740.     Hecho en Chino.
2kW of tiltable solar on the roof.
Behind the Orange Curtain, SoCal.

Offline bevans6

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Re: Bendix BVA-85 brake valve actuator
« Reply #3 on: March 15, 2013, 12:54:38 PM »
A stick is exactly how you do it, to be honest.  That's how I was taught during my air brake course.  If you are a truck driver and don't have a stick ( they sell nice adjustable brake application sticks at my local truck supply store, fwiw), the DOT inspector is going to ask you do demonstrate exactly how you apply the brakes for your daily inspection.  I have a stick that lives under the passenger seat.  What you do is this:  You get the engine running and get all the way up in air pressure, turn off the engine and fan the brakes until you have your checking pressure ( I was taught 90 psi to 100 psi, but no matter).  You mark or check all your brake pushrods with no brake applied, then you do a full brake application and jam the stick in place to hold the pedal down.  You then go out and measure the pushrod extension on all of the brake chambers.  It's a heck of a lot easier to do on a truck than a bus.  What I actually do, a variation on this, is measure the front brake pushrod extension with that stick method, but I just put the DD3 parking brake on and measure the extension of the rear brakes with that.  That lets me verify the parking brake operation and the pushrod extension with one check, and the parking brake is an 85 psi application anyway.  I can check the front brakes quite easily by turning the wheel outwards, but I have to take the rear wheels off to check the rear brakes.

Edit - you chock the bus so it doesn't roll over you, obviously...

Brian
« Last Edit: March 15, 2013, 12:56:34 PM by bevans6 »
1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
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Offline buswarrior

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Re: Bendix BVA-85 brake valve actuator
« Reply #4 on: March 16, 2013, 11:25:34 AM »
And don't go paying good money for a device advertised as a brake prop that costs more than a good old carpenter's bar clamp.

Choose one that will allow you to reverse the ends so the clamp pushes outward, instead of clamping inward.

Depending on the coach model, the clamp may be employed against the bottom of the dash, against the seat or seat base or up to the underside of the steering wheel.

happy coaching!
buswarrior

Frozen North, Greater Toronto Area