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Author Topic: Dual air pressure gauge  (Read 4624 times)
Lin
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« on: November 06, 2010, 12:23:42 PM »

I bought a new air pressure gauge at a flea market just because it looks better than the one I'm using and is lighted, while mine is not.  This new one though has two connection ports and two face needles-- a red and a white.  I figured I could just cap one port if it leaked back, but it would probably not make sense that it would.  Anyway, is there anything I might want to use the dual reading capability for.  My current connection reads the accessory tank, which leaks down even though the main tanks remain high.  I have a separate gauge in the engine compartment that reads the main system.  I thought of eventually hooking this gauge up to do both.  Does that sound like just busywork?
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luvrbus
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« Reply #1 on: November 06, 2010, 12:27:03 PM »

Lin, use the other needle for brake application pressure on that gauge that is what it is for


good luck
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Van
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« Reply #2 on: November 06, 2010, 01:17:44 PM »

Clifford, it must be, other wise it would say Front/Rear. Lin, You'll be proud to know I haven't blown my self up yet!  Shocked  Roll Eyes Sorry for the thread drift  Grin
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Dreamscape
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« Reply #3 on: November 06, 2010, 02:58:10 PM »

Clifford is right on as usual.  Wink That is the way my new gauge will be plumbed.
« Last Edit: November 07, 2010, 01:43:14 PM by Dreamscape » Logged

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Lin
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« Reply #4 on: November 06, 2010, 08:32:59 PM »

Okay, that sounds good.  How do I do that, just tap into the brake pedal line?
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Dreamscape
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« Reply #5 on: November 07, 2010, 06:39:11 AM »

I didn't plumb mine, it was already installed from the original configuration. I can crawl "Down Under" and take a look see if you want. If I remember (and that's a big if) it's plumbed from one of the ports on the treadle valve.
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Lin
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« Reply #6 on: November 07, 2010, 11:51:00 AM »

Paul, no rush. I guess that would be the only logical place.
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Dreamscape
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« Reply #7 on: November 07, 2010, 01:41:16 PM »

Here ya go Lin.

You can see where the lines T off from. They ran hardline up inside the coach then went to hose up to the gauge. I'm going to use nylon with the appropriate fittings for my VDO gauge in place of the hose. I don't know how your gauge is on the back, but mine has straight male thread. I bought two kits http://www.egauges.com/vdo_indA.asp?PN=150-851 Should be here on Monday so I can plumb it up.

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« Reply #8 on: November 07, 2010, 07:01:58 PM »

Hey Lin,


That gauge is for the newer two tank air systems. One is for the primary (rear) and one is for the secondary (front) air tanks.The gauges I have seen have a  green needle which is for the rear tank and a orange needle which is for the front tank. They should always line up on top of each other unless you have an air leak. Of course, not having a two tank system you would cap off the secodary port to avoid a possible leak.

Cade

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« Reply #9 on: November 07, 2010, 09:04:50 PM »

Cade, Could very well be, but my Eagle had a large gauge that had dual needles. It was originally set up with DD-3's, now have spring brake chambers.  I just got rid of the orginal gauge and will plumb the smaller one. Even though I have spring brakes, I still like to know the pressure when I make a brake application. It's just my way for our coach. Grin

Paul
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Lin
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« Reply #10 on: November 07, 2010, 09:21:36 PM »

Cade,
As mentioned, this gauge has a white needle on top, and a red needle behind it.  I like the idea of tying the red one to the brake.  Of course, it could still be used to show the difference in the brake tank and the accessory tank.

Paul

Thanks for the picture.  When I get to it, I'll have to follow the lines to be sure where they go anyway.  

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Gary '79 5C
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« Reply #11 on: November 08, 2010, 02:21:06 AM »

Lin,
I will be watching this tread, as I have the same dual white/red indicator guage.
I also can't get my simple mind around what information is yielded from a "application" guage for the brakes ?
Will this indicate a slight leak ? I am quite conservative in spacing and brake early, before I need to floor the pedal.
What am I missing, again ?

Thanks,
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« Reply #12 on: November 08, 2010, 03:54:12 AM »

The plumbing on the RTS buses use a dual gage with white and red needles and of course two fittings on the back.  They monitor the Primary and Secondary tank pressures and stay together if all is well.  We RTS folks have 4-tanks. One is the wet tank fed from a dryer(AD-2), one is Rear, one is Front, one is Suspension(accessories-etc). I think an 'application pres. gauge' would be interesting because it may show some trends towards how the brakes are working together.  Just a thought. Probably a 'duh' to the pros here.
phil
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luvrbus
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« Reply #13 on: November 08, 2010, 05:07:46 AM »

Eagles has always had a application gauge even with the dual air system you had a gauge for each system (front and rear)
they are nice to have 


good luck
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bevans6
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« Reply #14 on: November 08, 2010, 05:44:13 AM »

My understanding is that older buses had the air pressure gauge reading from the accessory tank, which is after the pressure protection valve.  When air brake systems changed in around 1979, the air pressure gauge was reading the dry (main) tank pressure as that was what fed the brakes directly.  With modern dual tank spring brake systems there are two dry or main tanks, one each for the front and rear brakes, and there is a dual gauge to show the pressures in each dry tank.

The only pressure that I NEED to know is the pressure in the dry tank, since that is what feeds the main service brakes.  If I have one gauge, that's the pressure I want to read.  With a DD3 system with an emergency brake tank, if I had a secondary gauge I would want it to read the pressure in the emergency brake tank.  The last pressure I would want to know about is the accessory tank pressure, sure it's interesting but kind of irrelevant to the safety systems on the bus.  Reading the brake application pressure is also interesting but not critical for me, it will tell you if you have a leak or if the system is requiring greater pressure than normal to operate, which could alert you to a problem.  But you can tell if you have a leak anyway by simply doing a full brake application and holding it for a minute and observing the gauge that reads the dry tank pressure.  But I guess it's kind of fun to see how much pressure you are using for a stop.

So I would connect one of your gauge pointers to the dry tank, and depend on it, and if you have an emergency brake tank I would connect the other pointer to it.  Since there are check valves that lock the air into the emergency brake tank, I would expect that it should read maximum system pressure at all times except when you apply the parking brake.  The dry tank pressure should rise and fall with the usage of air.

Brian
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