Trailer hand brake
#31
12-12-2007, 10:02 PM
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Originally Posted by headborg
Well bob's only part wrong,
the tractor protection valve will only engage when there's total air loss---from both tanks--when they both near 65pounds or so--that's when the protection valve on my truck kicks in-- I don't believe I have a way to drain just my primary so it could be triggered by it alone.(maybe) Trailer brakes dynamiting and protection valve engaging are 2 different things. here's another experiment: (1)park your truck on a hillside- engage the brakes--then supply air to the trailer brakes to dis-engage them(see-not holding in red button as that would damage it) (2) disconnect the blue service line--- FIRST( SIGNAL AIR ) (3) NOW disconnect the RED supply line- tractor protection valve should pop when air drops to around 65psi (4) get in the truck, and release the tractor brakes----get ready to cover the foot brake---your trailer spring brakes shouldn't have engaged( there's a protection valve on the trailer system just like the tractor--- very unsafe to have brakes lock up while rolling due to severed air line. this is the reason WHY I can't understand why anyone would want an Aux trailer braking system to feed off both your primary & secondary tanks--- that secondary is a (reserve)---if you were to loose brakes on the trailer---by way of broken service line, etc You'd want to keep as much air in the primary as possible---sure, every time you step on the foot brake you'd be losing air from both----but why would you want to compound the problem by piping air from Both tanks to a trailer brake via a hand valve? what ADVANTAGE would it really serve. 
#32
12-12-2007, 10:09 PM
Originally Posted by headborg
Originally Posted by bob h
Originally Posted by headborg
Originally Posted by RockyMtnProDriver
Originally Posted by bob h
Because the trailer still has service brakes with or without the hand valve. poor dumb limited experience driver's service line comes loose from glad hand or gets cut(what ever) he's rolling down steep hill, loosing air( but can't figure out WHY) he's pulling down hard on that hand valve----got his foot on the brake pedal. Do you really want him to bleed off all his air from both tanks? It is impossible to deplete the tractor air supply with an air leak from behind the tractor... that is what the tractor protection valve is for. preform the following experiment: with the tractor running, set the tractor brakes, supply air to your trailer as if you were ROLLING----now, take your seat belt and wrap around the hand valve like you would if you were checking your trailer brake lights---now go disconnect the blue- service line---and watch your air tanks deplete---- now, in my case--only the secondary tank empties out---- the trailer brakes will not dynamite unless the air is emptied from the trailer supply tank---which won't happen because there's no signal air to the control valve back there. Ok - so; 1. Your tractor uses secondary air for the hand valve... thanks for proving me correct on that. 2. The spring system on the trailer does not use a signal to control the valve, it uses supply air through the red line to charge the tanks and release the springs. That same air is used as supply for the trailer service relay... which is controlled by signal air from the blue line. 3. Where in my post did I claim that depleting sec air would cause the trailer springs to apply ??
__________________
Bob H
#33
12-12-2007, 10:16 PM
Originally Posted by headborg
Well bob's only part wrong,
the tractor protection valve will only engage when there's total air loss---from both tanks--when they both near 65pounds or so--that's when the protection valve on my truck kicks in-- I don't believe I have a way to drain just my primary so it could be triggered by it alone. All reservoirs must have a drain valve... maybe someone has stolen yours ??
__________________
Bob H
#34
12-12-2007, 10:18 PM
Originally Posted by headborg
Well bob's only part wrong,
the tractor protection valve will only engage when there's total air loss---from both tanks--when they both near 65pounds or so--that's when the protection valve on my truck kicks in-- I don't believe I have a way to drain just my primary so it could be triggered by it alone.(maybe) Trailer brakes dynamiting and protection valve engaging are 2 different things. here's another experiment: (1)park your truck on a hillside- engage the brakes--then supply air to the trailer brakes to dis-engage them(see-not holding in red button as that would damage it). Damage what ? What are you going to damage by holding in the red button ?
__________________
Bob H
#35
12-12-2007, 10:54 PM
3. Where in my post did I claim that depleting sec air would cause the trailer springs to apply ??
You didn't..and I didn't mean to imply you had--the other guy seems to have connected the tractor protection valve engaging and trailer spring brakes engaging as occuring at the same time/ which we both seem to know is not always the same depending the circumstances.... I'm sorry for calling you Wrong in the first post--I tried to temper/adjust it with the second---- If your trailer hand valve is piped correctly your tractor protection valve will do it's job( if we can agree that that job is to maintain an enough air pressure (at least in primary tanks to stop the damn truck). Thus, one shouldn't plumb their hand valve in a manner which would cause it to have to engage. All reservoirs must have a drain valve... maybe someone has stolen yours ?? Yes, correct: however I wasn't planning on crawling under truck in the snow to find it. Mine has pull cables for WET, and Secondary---maybe there's one for the primary on the passenger side---or maybe someone did steal it! Damage what ? What are you going to damage by holding in the red button ? See other thread post by: RockyMtnProDriver---Bendix warns against this practice as it can damage the tractor protection valve. RMPD claimed he has a manual stating this; and I support him--I've seen the same memo and was trained accordingly by a HOUSE CALL visit from the Bendix Pro Tech Traveling educational guy. But up until then....I'm ashamed to admit...I held my thumb over many myself. Wheither it's true or not...I don't know.
#36
12-12-2007, 11:44 PM
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Originally Posted by bob h
Originally Posted by headborg
Well bob's only part wrong,
the tractor protection valve will only engage when there's total air loss---from both tanks--when they both near 65pounds or so--that's when the protection valve on my truck kicks in-- I don't believe I have a way to drain just my primary so it could be triggered by it alone. All reservoirs must have a drain valve... maybe someone has stolen yours ??
#37
12-12-2007, 11:48 PM
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Originally Posted by headborg
See other thread post by: RockyMtnProDriver---Bendix warns against this
practice as it can damage the tractor protection valve. RMPD claimed he has a manual stating this; and I support him--I've seen the same memo and was trained accordingly by a HOUSE CALL visit from the Bendix Pro Tech Traveling educational guy. But up until then....I'm ashamed to admit...I held my thumb over many myself. Wheither it's true or not...I don't know. Subject: Proper Use of Two Button Modular Dash Control Valves Two button modular dash control valves are designed so that the control valves operate in the following manner: When the yellow (system park) button is pulled out, the trailer supply valve automatically “trips” and the red button “pops out.” This operation applies the parking brakes of both the tractor and trailer and closes the “control” and “supply” lines to the trailer. (See Fig 1) The red (trailer air supply) button may be subsequently pushed in. This operation releases the trailer parking brakes and supplies air to operate trailer auxiliary devices. (See Fig 2) Pushing in both the yellow and red buttons releases both the tractor and trailer parking brakes and opens the trailer “control” and “supply” lines. (See Fig 3) It has come to our attention that some vehicle operators are using dash control valves improperly when parking combination vehicles, overriding the automatic function of the system by holding the red button in when pulling the yellow button. Bendix does not recommend parking combination vehicles in this manner, since this parks the tractor but does not park the trailer. Fig 4 depicts the improper use of the dash control valve. There may, however, be situations where it is desirable to release the trailer parking brakes while the tractor remains parked, by depressing the red button. This procedure is generally used with the vehicle attended, to enable the use of auxiliary devices on the trailer, ie pump-off. Bendix has determined that if vehicles fitted with its MV-3 dash control valve are operated in a manner where the red button is not allowed to “pop out” automatically and the valve remains inoperative for extended periods, under pressure, this may impact its ability to function automatically during parking brake applications. It is recommended that when parking, both yellow and red buttons should be in the outward position and whenever possible the engine should be off, with the vehicle in gear and the front wheels turned toward the curb. This procedure will ensure safe parking and proper operation of the dash control valves.
#38
12-12-2007, 11:50 PM
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Originally Posted by bob h
Ok - so;
1. Your tractor uses secondary air for the hand valve... thanks for proving me correct on that. [/color]
#39
12-13-2007, 12:58 AM
Originally Posted by RockyMtnProDriver
Originally Posted by headborg
See other thread post by: RockyMtnProDriver---Bendix warns against this
practice as it can damage the tractor protection valve. RMPD claimed he has a manual stating this; and I support him--I've seen the same memo and was trained accordingly by a HOUSE CALL visit from the Bendix Pro Tech Traveling educational guy. But up until then....I'm ashamed to admit...I held my thumb over many myself. Wheither it's true or not...I don't know. Subject: Proper Use of Two Button Modular Dash Control Valves Two button modular dash control valves are designed so that the control valves operate in the following manner: When the yellow (system park) button is pulled out, the trailer supply valve automatically “trips” and the red button “pops out.” This operation applies the parking brakes of both the tractor and trailer and closes the “control” and “supply” lines to the trailer. (See Fig 1) The red (trailer air supply) button may be subsequently pushed in. This operation releases the trailer parking brakes and supplies air to operate trailer auxiliary devices. (See Fig 2) Pushing in both the yellow and red buttons releases both the tractor and trailer parking brakes and opens the trailer “control” and “supply” lines. (See Fig 3) It has come to our attention that some vehicle operators are using dash control valves improperly when parking combination vehicles, overriding the automatic function of the system by holding the red button in when pulling the yellow button. Bendix does not recommend parking combination vehicles in this manner, since this parks the tractor but does not park the trailer. Fig 4 depicts the improper use of the dash control valve. There may, however, be situations where it is desirable to release the trailer parking brakes while the tractor remains parked, by depressing the red button. This procedure is generally used with the vehicle attended, to enable the use of auxiliary devices on the trailer, ie pump-off. Bendix has determined that if vehicles fitted with its MV-3 dash control valve are operated in a manner where the red button is not allowed to “pop out” automatically and the valve remains inoperative for extended periods, under pressure, this may impact its ability to function automatically during parking brake applications. It is recommended that when parking, both yellow and red buttons should be in the outward position and whenever possible the engine should be off, with the vehicle in gear and the front wheels turned toward the curb. This procedure will ensure safe parking and proper operation of the dash control valves. I do everything wrong, I mean Everything... :wink: The only thing I did right when I parked tonight is shut the engine off, it warmed up, otherwise it would be running too... I'm pretty sure it won't go anywhere without me :? The only time I set my tailer brakes is when I spinout on a steep hill barefoot.
#40
12-13-2007, 02:00 AM
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Originally Posted by COLT
I do everything wrong, I mean Everything... :wink: The only thing I did right when I parked tonight is shut the engine off, it warmed up, otherwise it would be running too... I'm pretty sure it won't go anywhere without me :? The only time I set my tailer brakes is when I spinout on a steep hill barefoot. |
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