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Old 01-27-2021, 03:52 PM   #61
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Quote:
Originally Posted by Deezl Smoke View Post
CDL downhill braking history. To back up my previous claim of once accepted steady pressure.

Crash forensics
Thank your for finding and posting this article.

With all the nastiness online these days, I always hesitate to click on links, but this one is truly worth a read.
The article covers the pneumatic aspect of brake balance, and also of mismatched components; while I covered only the mechanical aspect of adjustment, which is most relevant for buses.
Pneumatic imbalance relates primarily to tractor-trailers, but the understanding of the concept is valuable knowledge for all of us.

Unrelated... but in response to a most kind comment above:
Sadly for them... SNL and Comedy Central cannot afford me.
...
...




But yes, I was quite well paid to write around 400 pieces for a European car magazine over almost 20 years. And I did use the Silent Radio Theater concept once or twice, to favorable reviews. Gotta have some fun in this often-tragic World.
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Old 01-27-2021, 04:15 PM   #62
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Quote:
Originally Posted by Deezl Smoke View Post
[video] Claimed the brakes failed. Thankfully no one was seriously injured. Was a heck of a ride for the owner/driver coming down Sylvan hill, 6%, and have to make the decisions he made.
I may still have security camera video of one of "our" 18-wheelers tipping over in a perfectly flat Sacramento intersection. (No, the driver was not one of my hires!)
Alas, I no longer have a machine that can play the disc. Heck, I probably tossed the disc long ago.
But the point is... Failure To Comprehend Vehicle Dynamics.

Comic relief:
The load that tipped over in the middle of town? 48,000 pounds of cheap beer.
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Old 01-27-2021, 10:07 PM   #63
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Join Date: Jun 2016
Location: Orange County, CA
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Year: 1990
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Chassis: Crown Supercoach II (rear engine)
Engine: Detroit 6V92TAC, DDEC 2, Jake brake, Allison HT740
Rated Cap: 37,400 lbs GVWR
In addition to considering installing a supplementary braking system (see my post 32), I also suggest fitting a dual-needle air pressure gauge to show brake application force. I did this in my bus for two reasons: 1) if your brakes are beginning to overheat on a constant downgrade you will need increasing air pressure to maintain a constant braking force or constant speed, and this is quickly shown on such a gauge; and 2) if you have a slight leak in one of the two brake systems you'll know because the two needles are no longer moving together.

Gauges are good - the more information you have, the better decisions you will make if everything's going tits-up in a hurry. Or as is said, knowledge is power, or at least wisdom (I hope).

John
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Old 01-28-2021, 12:55 AM   #64
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Originally Posted by Iceni John View Post
In addition to considering installing a supplementary braking system (see my post 32), I also suggest fitting a dual-needle air pressure gauge to show brake application force. I did this in my bus for two reasons: 1) if your brakes are beginning to overheat on a constant downgrade you will need increasing air pressure to maintain a constant braking force or constant speed, and this is quickly shown on such a gauge; and 2) if you have a slight leak in one of the two brake systems you'll know because the two needles are no longer moving together.

Gauges are good - the more information you have, the better decisions you will make if everything's going tits-up in a hurry. Or as is said, knowledge is power, or at least wisdom (I hope).

John
That’s a great suggestion there John on the dual needle gauge. Absolutely good to have that extra information to keep an eye on things. That extra second or so before the realization that sh*t is about to go south may make all the difference in walking away from it or not.
Cheers
Stay safe

Oscar
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Old 01-28-2021, 01:44 AM   #65
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Just to clarify the 2-needle thing. Most of those 2-needle gauges are showing the air pressure in the primary and secondary air tanks/systems...usually the front and rear. These are the supply gauges. An application gauge shows how much air pressure is being applied to the brakes and I've never seen it except as a separate gauge. I guess it would be possible to plumb a 2-needle gauge to show supply on one (which supply?) and application on the other...but I've never seen it done like that...and it would be non-standard.

If I missed something above, my apologies! I think you (Iceni John) posted something about an extra gauge which I missed. I'll look in the morning...after coffee. I'm just picturing all 2-needle gauges as showing supply air pressure. This might help clarify what I have experienced:

Screen Shot 2021-01-27 at 11.41.16 PM.jpg
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Old 01-28-2021, 08:41 AM   #66
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Quote:
Originally Posted by Elliot Naess View Post
I may still have security camera video of one of "our" 18-wheelers tipping over in a perfectly flat Sacramento intersection. (No, the driver was not one of my hires!)
Alas, I no longer have a machine that can play the disc. Heck, I probably tossed the disc long ago.
But the point is... Failure To Comprehend Vehicle Dynamics.

Comic relief:
The load that tipped over in the middle of town? 48,000 pounds of cheap beer.

Basic physics teachings have been going away now for quite some time. It's not that we can place blame on any certain generation or aspect of progress, but the handing down of basic physics comprehension is no longer being handed down from infancy. It now has to be taught at higher levels of education (a topic for another time and as such, IMO, has become somewhat..........sterile in nature. It is not understood anymore, but rather the book teaching is just memorized.


The trailer behind my neighbor's truck may have been, but I can not confirm it, one of the last "wedge brake" trailer in the area. Locals are pretty certain, as we know a bit more of the details about the owner/driver, he went to downshift while on the way down, and missed the lower gear, killed the engine, and then had nothing but the tow vehicle park cans, and maybe on axle park can on the trailer to attempt to slow him once he used all the onboard air. Just harmless armchair theorizing is all. But life experience on the road here in the PNW has taught me that spring cans on all straight axles is a must for any air brake vehicle I will be driving. Youtube has taught me to respect my teachings of the way back masters of otr freight relocation engineers. The vehicle is replaceable. The very second brake failure is recognized, ditch it.
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Old 01-28-2021, 11:48 PM   #67
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Rated Cap: 37,400 lbs GVWR
Quote:
Originally Posted by rossvtaylor View Post
Just to clarify the 2-needle thing. Most of those 2-needle gauges are showing the air pressure in the primary and secondary air tanks/systems...usually the front and rear. These are the supply gauges. An application gauge shows how much air pressure is being applied to the brakes and I've never seen it except as a separate gauge. I guess it would be possible to plumb a 2-needle gauge to show supply on one (which supply?) and application on the other...but I've never seen it done like that...and it would be non-standard.

If I missed something above, my apologies! I think you (Iceni John) posted something about an extra gauge which I missed. I'll look in the morning...after coffee. I'm just picturing all 2-needle gauges as showing supply air pressure. This might help clarify what I have experienced:

Attachment 53477
I plumbed my brake application force dual gauge to the spare ports on my E6 treadle valve, so it's reading the exact pressure being applied to both brakes. I also have the usual two separate gauges for each system's reservoir pressure, read directly off each tank. The only air system whose pressure I don't monitor closely is for my accessories, and that's less important.

With eleven gauges in front of me, plus another three "fun" gauges nearby, and nine more gauges back in the engine room, I now have no excuse to not know what's happening!

John
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Old 01-29-2021, 12:04 AM   #68
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Quote:
Originally Posted by Iceni John View Post
I plumbed my brake application force dual gauge to the spare ports on my E6 treadle valve, so it's reading the exact pressure being applied to both brakes. I also have the usual two separate gauges for each system's reservoir pressure, read directly off each tank. The only air system whose pressure I don't monitor closely is for my accessories, and that's less important.

With eleven gauges in front of me, plus another three "fun" gauges nearby, and nine more gauges back in the engine room, I now have no excuse to not know what's happening!

John
Nice! More info is better...well done. Two of our buses have air starter tank pressure gauges, too (I plan to convert those to electric start, though). But I've not currently got any with application pressure gauges. It's a good idea, though. You, sir, are the Gauge Master.
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Old 01-29-2021, 09:07 AM   #69
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Join Date: Mar 2017
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Year: 1998
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Quote:
Originally Posted by Iceni John View Post
I plumbed my brake application force dual gauge to the spare ports on my E6 treadle valve, so it's reading the exact pressure being applied to both brakes. I also have the usual two separate gauges for each system's reservoir pressure, read directly off each tank. The only air system whose pressure I don't monitor closely is for my accessories, and that's less important.

With eleven gauges in front of me, plus another three "fun" gauges nearby, and nine more gauges back in the engine room, I now have no excuse to not know what's happening!

John
the air pressure your are reading is NOT what is at your brakes. the treadle valve only controls a relay valve. the relay valve gets its air supply directly from a tank so if you want to know what pressure is in the brakes you must plumb it to the relay delivery ports. not a good idea as with air you can not see the leaks as in hydraulic and any modifications may not be legal. all air brake fittings used must be identified with a stamp (dot) to prove its certified for use with air brakes. use of other fittings,hoses ect. can cause a failure on a inspection until corrected even tho you are not a cmv. get a air brake flow chart and it will help you understand how it works
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Old 01-29-2021, 10:49 AM   #70
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Join Date: Jun 2016
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Posts: 988
Year: 1990
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Chassis: Crown Supercoach II (rear engine)
Engine: Detroit 6V92TAC, DDEC 2, Jake brake, Allison HT740
Rated Cap: 37,400 lbs GVWR
Quote:
Originally Posted by mmoore6856 View Post
the air pressure your are reading is NOT what is at your brakes. the treadle valve only controls a relay valve. the relay valve gets its air supply directly from a tank so if you want to know what pressure is in the brakes you must plumb it to the relay delivery ports. not a good idea as with air you can not see the leaks as in hydraulic and any modifications may not be legal. all air brake fittings used must be identified with a stamp (dot) to prove its certified for use with air brakes. use of other fittings,hoses ect. can cause a failure on a inspection until corrected even tho you are not a cmv. get a air brake flow chart and it will help you understand how it works
Yup, I know that! I could have plumbed my Application Pressure gauge to the individual relay valves, but that would have been a lot more difficult to do; I still like to know if have any leaks between the E6 and the relay valves. Also, I use only DOT air fittings and DOT air hose everywhere, including where they're not even needed, just for peace of mind. And I always follow a complete Air Brake Checklist before every time I drive the bus, without exception - it's especially important for buses like mine that are not driven very often while it's still being converted. So, don't worry, everything's under control!

Thank you for you concern, John
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Old 01-29-2021, 10:58 AM   #71
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Rated Cap: 7 Row Handicap
Doing a good visual before driving (like using cheese wagon”s ore trip sheet) is also a good way to pick up on other possible issues .. broken exhaust clamps, hanging wires , hub oil leaks as they start, etc
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Old 01-29-2021, 12:55 PM   #72
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i can see a advantage as to knowing pressure on the brake chamber itself as leaks would be more evident in all my years treadle valves were not often prone to failure as the relays were,. most relays also have a screen on the control port which can get plugged or ice up when air dryers are not present or working. i also will be adding gauges as i dont think there is a issue with too much info. my first is going to be a boost gauge and a mechanical engine temp gauge as i dont trust electric temp units. had quite a few electrical ones that were incorrect
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Old 01-29-2021, 05:40 PM   #73
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Quote:
Originally Posted by Elliot Naess View Post

But if you stack 20 bricks on the pedal, all the brakes will each be doing a pretty fair amount of the work.

Starting down the hill at "ridiculously" low speed in the first place is vital, yes.

And even if you can learn by rote to perform the pre-trip steps in correct order, it means little for traffic safety if you do not understand – comprehend – the what-how-&-why of what you are inspecting.

I was sledding down Ashland Grade on water-no-longer-running.

What to do?!

(Hint; Free Bird knows.)
Thanks for the vote of confidence but as a Canadian (who could possibly find himself on an icy summit in a loaded 18 wheeler with 0 previous experience) I would probly just soil the seat and jump!

In regards to school busses in less slippery conditions - applying lots of pedal pressure to ensure you are getting the best response on all wheels is a great point.

My bus has front discs and rear drums so I spose that technique would would be quite useful?
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Old 01-29-2021, 06:59 PM   #74
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Quote:
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With the AT545 ... ... maybe disengages, starts freewheeling, when you recognize this you have to get on the throttle to reengage. ....
You had just said it yourself, except you were talking about an automatic transmission.

I will guess the basic concept of "stabbing" probably applies to discs also, though disc brake pads are always almost-touching or even very-lightly-touching the rotor, with no mechanical steps of adjustment involved. Drum brake shoes have return springs*; disc brake pads do not.

(*Any "leading" shoe in a drum brake applies itself via friction and leverage, so it would never release without a spring.)
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Old 01-30-2021, 01:40 PM   #75
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Hey Elliot,

We are on the same page here, I also assume that hard intermittent braking is a good technique for my bus. I have (in summer conditions) traveled some pretty steep logging roads with no issues. Dropping a couple of thousand feet on grades ranging from 6 to 15% is a pretty good test. No Jake and no gears low enough puts the brakes to a serious test. So I can definitely say that "stab" braking works with hydraulic brakes, what I don't know is where the expert opinion and science leans on this.

After it became clear that my bus was not suitable for the intended application I dumped the AT545 and stuck in a 6 spd standard. Now I can gear down to where the brakes are casually sitting in reserve, it's a good feeling.

On an unrelated topic here are a couple of links which might interest you.


https://trialsitenews.com/slovakia-b...d-19-patients/
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Old 01-30-2021, 03:28 PM   #76
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Quote:
Originally Posted by Free Bird View Post
... ... ... I dumped the AT545 and stuck in a 6 spd standard. Now I can gear down to where the brakes are casually sitting in reserve... ...
Here we have the answer to this entire thread; what I call "hanging the truck on the engine" -- like hanging a winter coat on a peg on the wall in the mud room, and it stays there until next time you want to wear it, requiring zero attention in the meantime.

I used to go thru all this (and much more!) with my trucking trainees. Abstract concepts are never easy for any human to grasp. But the coat on the peg seemed to help, since it is so easily visualized by anyone who has ever worn such a garment.

Then "hang the truck on the engine", and/or "hang the engine on a gear" -- either way, whatever made the trainee's eyes open a little wider in comprehension.

I ramble on and on about this, because so many of us skoolie folks are trainee drivers.
Also, I remember stumbling clueless into truck driving school in 1982! lol
Yet, I was immensely lucky to be well ahead of the curve, since I was already a journeyman auto mechanic with a side order of automotive engineering. (As opposed to any normal life skills, ha ha.)

I would love to install in Roadranger in Millicent, yes.
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Old 01-30-2021, 04:03 PM   #77
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Rated Cap: 7 Row Handicap
Yep I love gears!!! I’m my red bus I installed a 6 speed allison and wrote the software to drive it down one gear at a time .. in fact I wrote the software to essentially let cruise control drive my bus down a mountain if I wanted.. something that my newer pickup trucks have all had built in.. set the “fake cruise” as I call it (I don’t really use the bus cruise control although it willl ).. and the computer drops up and down gears to stay within a range..

No clutch no grinding no floating just pure allison automatic perfection
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