Seeking a good reference on compressed air systems

[dentarthurdent]

Hi All:

I am seeking a good book or web site with lots of information on the compressed air systems used in buses, etc. I found "Air Brakes & Accessories for Coach Conversions" by George Myers and I am thinking about ordering it. Does anyone have any experience with this book? Can you comment on it? A good value?

Any other suggestions would be greatly appreciated. I am new to buses, air brakes, air throttle, etc and I want to understand those systems well and maintain them well.

It seems that my "wet tank" (is that the right term - that's what the previous owner called it) is getting lots of sludge in it - has to be drained daily and I am not sure if that's normal or not.

thanks again! - Tony

[the_experience03]

I will ask the guys over at the diesel program at school what book they use for their 5 credit (!) air brakes class.

[dentarthurdent]

That would be great!

[swinada]

how about this here? http://www.gnb.ca/0276/vehicle/pdf/ab_manual-e.pdf right click on the link and choose "save target as"
84 page PDF manual from the province of NewBrunswick with colour pictures and all. happy reading to you.

[Elliot Naess]

Regarding your wet tank sludge:
It is normal to drain the air brake system daily (when driven). If this has not been done lately, there may/will be quite a lot of goop in there. The goop is water (moisture from the air) and oil (from the engine -- blowby ("reverse blowby") in the compressor). Nothing to worry about, so long as you keep it drained.

The basic air brake system has two tanks in series. The first tank after the compressor is called the primary or wet tank, because that's where most of the moisture settles out. The secondary tank then supplies the less contaminated air to the rest of the vehicle. There is a check valve between the primary tank and the secondary tank, so that air will not be lost "rearward" in the system if a breach occurs in the wet tank.

Many vehicles have more than two tanks. Millicent has four, but it looks like two at first glance. Each of those two has a divider in the middle, making each effectively two tanks. No, I have never bothered to learn exactly how the four interact.

I recommend pull cord drains on all tanks. Four bucks a piece at any truck parts store. I rigged mine so they are easy to reach, and I give them all a tug each time I drive the bus.



You are looking at four little steel cables that I ran thru holes in the bottom rub rail. Each has a loop on the end for tugging on, and the other end is attached to a spring loaded drain valve. Makes it really easy to keep the tanks drained.

[dentarthurdent]

swinada - Thanks for that link - I'll be doing some reading now...

Elliot - thanks for the info. It appears that my All American has 4 tanks as well - at least there are 4 spigots inside the door under the driver's window. I do know that the very front tank is for accessories - door opener, air throttle, etc. I think the two in between that and the wet tank are for front and rear brakes respectively. I was concerned by large amount of sludge that came from the wet tank - but I guess that with dramatically falling ambient temps there's been more condensate.

I am interested in pull cord drains - anything that makes it easier also makes it more likely to get done routinely. And with the valves like they are, you have to stand back a ways to avoid splatter from the sludge hitting the side of one of the tanks there near the valves.

Is there any sort of routine inspection or maintenance that needs to be done on the air throttle?

thx again - Tony

[Elliot Naess]

anything that makes it easier also makes it more likely to get done routinely.

You bet! See photo I added above.

[wtd]

The Bendix site has some good info. The Air Brake Handbook is a good read. They also have data sheets and repair/replacement info on most of the components that you'll most likely see on your bus.

Here's a link http://www.bendix.com/en-us/service/...ages/Home.aspx. This does right to the documents page on the Bendix site.

[dlor1]

Wow, those are some good links. Air Brakes really aren't that complicated. Well I've been having a problem with my breaks for a bit now. It seems that when I apply small amounts of pressure on the brake pedal the driver's side front wheel's brake does not engage. Only after substantial breaking force does the drum and shoe engage. When it does the shoes smack out against the drum with an unmistakable thud, thus locking the wheel until I back off the pressure and reapply the brake pedal. (Pumping the brake) I've adjusted the brakes several times and seem to be doing it properly. Turn all the way in then back off 1/4 turn. I've greased the brakes at all of the fittings. I've repeatedly drained the tanks. What else should I do?

[wtd]

Sorry I didn't reply sooner - usually threads stop abruptly after I post, so I never really go back and look at 'em.

If your bus is a rear engine you probably have a relay valve near the front brakes. I'd check the line pressure between this relay valve and the brake chamber to see if it's at the brake itself, or the relay valve sticking or not working right.