Had a fire very close to me the other night; sorry to say the poor 84 year old woman died in the fire. Needless to say it is a very sobering experience. Had it been much closer, I might have received some damage in so far as bubbling paint and other heat radiation damage. So... I've decided to install a nitrogen tank and plumb it into the main system so I can air-up the bus in about 30 seconds. That in itself seems pretty fast, but my bus has been plugged into the wall at a service center and goes from zero to 135 in way less than a minute, so I'm assuming I can do the same with my tank.
It seems like it would come-in pretty handy when you have to leave an RV Park at odd hours. I mean, who wants to listen to a diesel engine for 15 minutes while the bus gets to operating pressure at 3 am. I know 70 or 80 psi will get me going, but I'd rather have the confidence of 135.
Has any body else ever done this?
Your comments are welcome.
Thanks!
Where did you connect your air fill at the service center? Under a minute just seems unlikely to me - I have an 80 gallon tank at 135 lbs that I can use to air up my bus, and the restriction of the fittings and valves makes it a lot slower than "under a minute". I'm going to have the opportunity to test in a day or so, but I would expect at least 5 minutes to fully air up the bus. You might want to look into legal transport of a high pressure tank, I did that once when I was thinking of carrying a nitrogen tank to air up tires at a race track, and decided not to. My buddies who did use nitrogen had it delivered to the track, they didn't transport it. The only other idea I have is calculating how many cubic feet of air/nitrogen you would need to air up the bus, including all of the suspension and what not. I guess if I was honestly concerned about being able to get away at literally a moments notice I would run a small, ultra quiet compressor all the time. People who do say it only runs once every several hours for a few minutes with normal leakdown.
If mine could air up in a minute, I wouldn't think twice on any other options.
Floyd
You're making me feel better about the hydraulic brakes on my bus!
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How about a SCUBA tank? Do you have a spare 3/4" fitting in your wet tank for it?
John
About 40 years ago American LaFrance fire apparatus, (both engines and ladders) had something called a quick air up system. Sometimes the fire equipment would sit literally hours, (rarely a day) between uses. The air brake pressure would drop. The system allowed the rig to respond Code 3 literally within 30 seconds. Air pressure was up. The brakes worked. I wonder how they did that.
Standard wedge type air brakes of the time period. Later anti lock type that did not work. Anti locks disengaged. Detroit Diesels. Usually 8V71N. The later ones had the 8V71T. Or was it a case of the brakes not leaking down that much and the air pressure was high enough to go? Long ago far away. Naming names ... Bakersfield Fire Department, Bakersfield CA. About 1975-78.
I distinctly remember the low air pressure buzzer sounding upon start up. While waiting for visible oil pressure the low air pressure buzzer stopped. Air pressure up. Off we went. Fuller T905 trannies. Small mufflers. Rowing through the gears. Much fun. :)
The harder you press the accelerator, the faster air gets into the tanks. I bring my bus up to 100psi after forgetting to turn the wheelchair lift off by raising it to 1500rpm. If I forget and leave the lift on then the system bleeds air rapidly.
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How about a 500 psi carbon fiber tank and special electric compressor?
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how about a 1-200 gallon shop tank with a 1 inch hose... and u will use it more than a one shot nitrogen deal...
A 110 pancake compressor to keep the bus aired up all the time would let you use the air for other purposes and accomplishes your goal of a quick getaway. Forget about the rapid air ideas. Rube Goldberg solutions to once in a lifetime occurrences are a waste of time, energy and money.
Air tanks need to be drained to avoid fluid buildup.
Besides, it takes 3 minutes to get a bus air tank to 100psi. You only need 25psi to get the emergency brakes off. That takes no one at all.
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What air brake system only needs 25 psi to release emergency/parking brake? Spring brakes need 65 psi, and DD3 brakes need around 90 psi. Is there another common system?
Quote from: bevans6 on September 08, 2017, 03:22:12 AM
What air brake system only needs 25 psi to release emergency/parking brake? Spring brakes need 65 psi, and DD3 brakes need around 90 psi. Is there another common system?
Emergency brakes come on at 25psi. 65psi is when the low air pressure warning comes on. 100psi is the recommended minimum for moving but... if you're over 25psi, as long as you don't use air, you should be able to move.
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A SCUBA tank is an excellent option. In the 80s used a SCUBA tank to run the turnpike from South Jersey all the way to northern Connecticut. It was only 1/3 exhausted with the air wipers running all the way. Compressor drive went out. Plumbed the 2nd stage line of the regulator(100 psi) into the air system at the engine. It was a heck of a conversation piece too. The yellow tank was bungee corded to the engine hanger strut on the back with the engine door open. The truckers we're having a time with that setup. At 3000 psi tank pressure, it will take you a long way. We have since installed an electric auxillary air compressor that runs off the genny & it has bailed us out a time or two...
Sometimes its a curious bit, finding your e-brake systems psi apply starting and finish rating, as each has their particulars. Long as they follow in the specifications.
The rules and exams have this mention varible for this reason "not us". So the warning light should come on around 65psi (and before 60). Our air brakes with spring brakes for parking, have the automatic apply rating with air pressure between 45-20psi. http://www.truckingtruth.com/cdl-training-program/page45 (http://www.truckingtruth.com/cdl-training-program/page45)
I always thought it interesting in a spring brake setup to safely push the knob in from an empty air system and see the pressure when the knob stays in on its own. Its just a curiuos bit to again safely know this, also to understand the ability to roll or not safely and ofcourse respectfully to the equipment.
It takes a bit of homework understanding these systems for sure. I myself always have been around the spring and hydraulic brakes the majority of my time. And I can easily see and put very very much respect in any system designed to carry passengers.
ps: nothing aggrevated me more than a full throttle in startup because some idiot couldn't put the doughnut down earlier to get to the vehicle earlier to let the air build up respectfully on the equipment.
Its Friday so have a good day
Floyd
Quote from: Zephod on September 08, 2017, 06:27:03 AM
Emergency brakes come on at 25psi. 65psi is when the low air pressure warning comes on. 100psi is the recommended minimum for moving but... if you're over 25psi, as long as you don't use air, you should be able to move.
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No, to put it short form. Part of this is correct. A typical DD3 system will auto-apply the parking brake when the air pressure in the emergency/parking brake tank falls to around 25 psi - the pressure setting in the push-pull valve spring. A spring brake will auto apply when the air pressure falls to around 65 psi, or the pressure where the spring overcomes the force of air on the diaphragm in the brake canister. To release a spring brake you need to build air pressure over the 65 psi level to force the spring to move to take it's pressure off the push rod.
DD3 are a different beast from spring brakes. Typically the parking brake diaphragm is fed through the inversion valve and through an 85 psi air regulator which is supplied from the emergency/parking brake tank. As well, the parking brake diaphragm is smaller than the service diaphragm so it develops less push for a given air pressure. If a bus is parked normally and the parking brake is set, it's set with 85 psi of air pressure in the parking brake section of the canister. At the same time, the locking clutch on the pushrod locks. To release the parking brake, the first thing is the push pull valve is operated and the inversion valve removes air pressure from the parking brake section of the DD3, and applies air pressure to the locking port to release the push rod locking clutch. Normally that will not release the parking brake. To release the brake, the second step is a service brake application of greater force than the parking brake force needs to be applied to move the push rod out slightly farther than it was locked at, so the locking clutch can actually release the push rod. Only then is the parking brake actually released. Typically this requires around a 90 psi application of the service brakes, so you need at least 90 psi in the air system to release the brakes.
135psi is a bit high for your brake system. 120psi is more like. Believe it or not, those extra 15psi is extremely hard on the compressor. But-you choose. Good Luck, TomC
We carry a bottle of dry nitrogen, argon, and co2. For tig ,tires and tools. Most dangerous is still propane, more deaths and property damage worldwide. Best accelerant and enhancer . rdw
Thanks all for replying. I did look into the legal transport of a high pressure tanks and you can transport a few... I think it's 4 scuba tanks simultaneously. Beyond that I think it's illegal. Anyway I would only have a single tank mounted in the center of one of the bays to avoid any possibly of a mishap during an accident. When I was plugged into the wall at the service station, they had two huge air compressors in the back and the hose itself was larger than normal. I'm thinking about a 60 CF Steel cylinder permanently attached. If I fill it with helium, would my bus become lighter on air-up? ;)
A small 120V air compressor and a bendix DV2 drain valve should be able to keep the air pressure at the right levels without the risk of compromising any parts of the system.
Depending on where you tie in to the system, you may need to set the pressure below the coach Bendix d2 governor so it doesn't vent thru the air dryer exhaust.
On a spring applied park brake, 30 psi may start to release the brake, but it takes 60 psi to fully retract the brakes.
Then, if you have an air throttle, you will need air for that . . . .
My 80 gallon shop air compressor at 150 psi can air up the coach (from 0 psi) to 120 psi in around 5 minutes (If it is at 150 when I start)
In all reality we used a pancake compressor for years to keep our first bus aired up in rv parks. Worked perfect. Nothing needs to be exotic here. Simple it probably better. But I'm all for new ways.
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I like the idea of a small compressor that always keeps the bus aired up versus a high pressure canister. My bus will hold air for a long time in the summer, but not long in the winter.
Instead of work-arounds...
How about make your air system tight?
The new stuff is start and go. For the last 20 years, no leaks overnight.
Our shutters, belt tensioners, air wipers, can all be isolated from the "brake tanks".
By design, some older models already are.
You might be quite surprised to see your own bus release the parking brake and go, with the air gauge very low.
The "brake tanks" can't be seen on the dash in many older models, the gauge is plumbed into the auxiliary.
Catch up the preventive maintenance, check valves and pressure protection valves.
happy coaching!
buswarrior