1973 Blue Bird

[somewhereinusa]

They are quick release valves, described on page 23 of the manual.

I found the one on the bottom of your tank on page 13, it is an automatic drain valve.

[Rudy]

They are quick release valves, described on page 23 of the manual.

I found the one on the bottom of your tank on page 13, it is an automatic drain valve.

Dick, you are making me want to go read that stuff right now. It helps that you identify the components. Now I won't feel so ignorant when I read the manuals.

[Sharkey]

See this topic for discussions of how "Jake" brakes work:

http://www.mrsharkey.com/forum/vwtp.php?t=377

[Rudy]

I just perused the Bendix Air Brake PDF. All those words and schematics are somewhat intimidating.

I never was good with book learning.

Basically, I just want to know how to adjust my brakes and drain my tanks.

[Sharkey]

"About dusk on the fifth day, we reached the top of Cajon Pass west of Barstow, California. Before retiring to the sleeping compartment, Dave had warned me against this thirty-five-mile stretch of mountainous down-grade. ‘Wake up Ford and me when you get to Kayhone Pass,’ I had understood him to say, ‘I don’t want to be in this box when you start down that twister with the kind of brakes we’ve got.’ I had heard but not seen, my Spanish being nonexistent, the word Cajon failed to register when the sign appeared. Soon, however, I realized my error. The brakes wouldn’t hold. Now running in third gear, I tried desperately to get into a lower speed. Nothing doing. I saw I would just have to ride it out. Well down the long grade by now, I suddenly saw something moving across the road ahead. There was along dark shadow and then a red glow flared in the sky. I realized with new alarm that a freight train was cutting across our path. The truck roared on. Dave and Ford screamed bloody murder in the compartment behind me. And I clung to that steer-ring wheel like a madman. Had Mack Sennett been on hand with a movie camera, he would have gotten enough footage for one of his famous Keystone Kops features. As we raced inexorably toward the crossing and doom, the train’s caboose loomed out of the darkness. Its red lights cleared the highway just as we reached the tracks. We had escaped certain death by inches." - Clessie Cummins

I know ~exactly~ where this RR Xing is, crossed it many times myself, and have had to stop for trains a time or two as well. It's probably long ago been converted to a road/grade separation.

[Rudy]

Hey Sharkey, thanks for the scary story. Fortunately there are no steep grades where I am going.

[Headache]

I have had it explained to me several times and I still don't understand how they work.

<snip>

Blue Ox and other exhaust brakes do the same sort of thing by blocking off the exhaust.

The best layman's language explanation I ever got for jake brakes was during the compression stroke, instead of the valves staying closed in certain cylinders the cam opens them(while no fuel is injected into the cylinder) releasing the air. Think inertia, the cylinders that do get fuel and compression have to work harder to push the rest that now don't have it. Or think of your own body pushing a boulder. It's easier with friends but as those friends drop out it's harder for you and you slow down.

I had a switch labeled with 2, 4 and 6 on it. The numbers represented how many cylinders were "cut off" from fuel injection and compression during engine braking. The higher the number the stronger the braking(inertia slowdown).

The best explanation I ever got for exhaust assist braking was that it was similar to cramming a potato into your exhaust pipe.

[ezrablu]

How in the hell am I EVER going to take my bus through any mountains reading stuff like this?!?!?

[Dennis The Bus Dweller]

Just go for it

[ezrablu]

Dennis...that's been my way ever since I can remember. At least when I was younger I was naive enough to think I could do anything. Now days I've failed just enough to realize I should be in one of those Holiday Inn Express commercials

http://www.youtube.com/watch?v=l8Ah8WTL2i8

[Sharkey]

This probably deserves a topic of it's own, but I'll post here for brevity.

Exaust Brakes:

Exhaust brakes are nothing much more complicated than a throttle butterfly plate in the engine exhaust pipe. The one on my bus is just after the turbo and actuated by a pneumatic cylinder. The air supply to this cylinder is modulated by a lever on the dash, and a lockout valve is connected in line with the cylinder air supply to prevent it's actuation unless the accelerator pedal is not depressed.

Exhaust brakes work by building up back pressure in the exhaust system. This produces a moderate braking effect on the engine, retarding downhill speeds in a useful manner.

The use of an exhaust brake stalls the turbocharger, so if you hit the accelerator just after using the exhaust brake, expect lots of black smoke until the turbo spools back up.

The danger of using an exhaust brake is that if enough back pressure is produced, the exhaust valves may be forced open to relieve the pressure. This poses a hazard because if the valves are floating open and the piston comes up to the top of it's stroke, it can hit the open valves. My system has a pressure gauge on the dash that shows the exhaust manifold pressure, presumably so the driver can let off the exhaust brake if the pressure exceeds a safe level.

Jacobs Brakes

Jake brakes supply a much stronger braking effect. The premise behind this is that when the piston is at the top of the compression stroke, the exhaust valve of each cylinder is opened, allowing the compressed air in the cylinder to escape into the exhaust system. The valve remains open of some portion of what would have been the power stroke before it closes. This is the reason that engines using Jake brakes exhibit such a loud racket BRRRRRAAATTTT, a very large amount of highly compressed air (probably 500 PSI or so) is simply released into the exhaust manifold and escapes though the muffler (if any).

The reason that this produces such a pronounced braking effect is that each cylinder requires a lot of power to compress the air during the compression stroke cycle. Normally, this power is recovered when the piston starts it's power stroke. Even without fuel, the compressed air itself will force the piston down. Adding fuel at the top of the compression stroke adds power to the total amount being recovered by this "spring effect". Without the spring effect, the cylinders become net energy consumers rather than producers.

When the switch on the dash is moved from 2-4-6 the effect is compounded as additional cylinders are made to dump the power they "saved up" by compressing air in preparation for the power stroke that never comes.

As for fuel injection during this process, if you have your foot off the accelerator pedal and the engine is running faster than an idle, then there is no fuel being injected whether the Jake is on or not, the governor in the injection pump will see to that.

[Mark R. Obtinario]

The item on the bottom of the tank on the right of the picture is an automatic spitter valve. It is supposed to spritz moisture out every time the compressor cycles. They work okay but you still need to manually drain your tanks on a regular basis.

The two valves that have all of the lines going in and out are relay valves. They are in place to make sure that whenever brakes are applied that they get applies in the correct sequence and with the same amount of pressure. It isn't so important on a single vehilce but on combinations it is important that the rear most brakes go on fractionally sooner than the more forward brakes. It helps to pull the string straight rather than have the back of the string bunching forward.

In the picture of the brake cans you can see how the rear brake can is made up of two compartments. The one farthest away from the actuating rod is the spring compartment. The one closest is the service brake can. In the left portion of the picture you can see the slack adjuster.

When the brakes are applied, the actuating rod pushes against the slack adjuster and rolls the 'S'-cams against the rollers that push the brake shoes against the brake drums. The slack adjuster pivots on the rod in order to keep the stroke of the actuating rod to a minimum. You want a little slack so the shoes don't drag. But you don't want too much slack or you will run out of actuating rod length to fully apply the brakes. If the linings are too worn out or way too far out of adjustment you can "roll" the 'S'-cam over the rollers and end up with the 'S'-cam on the wrong side of the rollers.

On the back side of the slack adjuster there is a 9/16" head with a locking collar. To adjust the brakes you need to take a socket or box wrench to the head, push against the locking coller to release the locks and then turn the wrench to adjust the brakes.

The first few times ou do this you should have the wheel off of the ground so you can spin the tire around as you adjust the slack adjusters.

Call me if you want to and we can talk about what I am describing.

[Rudy]

Thanks Mark. As soon as it stops raining here, I will investigate adjusting the brakes. Jacking up the bus to get the rear wheels off the ground will be tricky.

I must say that the bus stops pretty good already.

[Rudy]

Oil filters. The oil, oil filters, transmission fluid, and transmission filter were changed about 100 miles ago.



This is a Cat 1160 motor. People tell me that that is a GOOD motor. I wonder what that rectangular box with the silver thing on the side of it is.

Anyone know about that box?

[Sharkey]

Well, considering it has two low-budget NAPA oil filters hanging off the bottom of it, I'd say it's a good bet that it's the engine's oil pump. Oddly-shaped thing, though. Usually, oil pumps are internal and resident somewhere in the vacinity of the crankcase sump. The silver can with the wire looks to be an electrical oil pressure gauge sending unit.