Quick, where's the air pressure gauge?

[Old Scout]

...given your experience with this sort of thing, you probably also know that air brakes were, at least in part, born out of the need for semi-trucks to quickly connect/disconnect from the brakes on the trailers they were towing....air brakes are a good solution for that application....realize it is a bit apples and oranges but if vehicle weight and size were the only factors here, then 747s would have air brakes?????.....both braking systems have their pros/cons, and both require periodic maintenance to function properly....

[paul65k]

Originally Posted by FL420

She and then I did press all the buttons and went through all the menus we could access. I saw beaucoup information that I would consider "nice to have" but very little "must have" information. Didn't see air pressure info in any of the menus.
The coach obviously has an air compressor if it can air up the suspension and I assumed it had air brakes since it had a compressor and a Parking Brake knob that looks exactly like the one required by federal law for air brake equipped vehicles. Also, there are very good reasons that almost all vehicles of that size and weight have air brakes instead of hydraulic brakes.
I have a special interest, education and experience in human factors engineering as it relates to the man-machine interface and unfortunately many designs of that era were not really ready for prime time.

Originally Posted by Old Scout

...given your experience with this sort of thing, you probably also know that air brakes were, at least in part, born out of the need for semi-trucks to quickly connect/disconnect from the brakes on the trailers they were towing....air brakes are a good solution for that application....realize it is a bit apples and oranges but if vehicle weight and size were the only factors here, then 747s would have air brakes?????.....both braking systems have their pros/cons, and both require periodic maintenance to function properly....

Just to echo on Old Scout's thoughts......most school busses also use hydraulic brakes and this would make me wonder why they don't use air on such beefy machines.....maybe safety???

[FL420]

Originally Posted by paul65k

Just to echo on Old Scout's thoughts......most school busses also use hydraulic brakes and this would make me wonder why they don't use air on such beefy machines.....maybe safety???

The school district I drove for had ~ 200 school buses spread over 3 terminals. As a relief driver qualified in everything in the fleet from 4WD Suburbans to 65 passenger CNG pushers I can assure you the only vehicles without air brakes were one old short yellow school bus, one small hybrid bus, the Suburbans and about a dozen 21 passenger white activity trip vans. The short bus was the only yellow bus that was gas powered. It was very rarely used and was the next bus to be retired.
Many of our regular routes and activity trips were in the Rocky Mountains. The long nose buses and the transit style FRED buses that were allowed to drive in the mountains had air brakes and electric drive line retarders. The drivers had to have an extra week of training and certifications in mountain and adverse conditions. In the five years I drove them school was never cancelled for a snow day, much to the disappointment of many kids and parents(and drivers.)

[RVPioneer]

I read on the internet, so it could all be wrong, that many of the Pacific Northwest coach builders, WRV/Alpine, Country Coach, Beaver and Monaco, which has its origins in Oregon, employed engineers and technicians from the aerospace industry. This may explain, in part, why different systems were utilized in these coaches compared to coaches built in other parts of the country.

In the case of our Alpines, the hydraulic disc brakes work quite well, as does the proprietary Peak chassis. With the 2-stage engine brake on the 400hp ISL and a 30K lb coach, it is a pleasure to drive.

[FL420]

Originally Posted by Old Scout

...given your experience with this sort of thing, you probably also know that air brakes were, at least in part, born out of the need for semi-trucks to quickly connect/disconnect from the brakes on the trailers they were towing....air brakes are a good solution for that application........

Good point. Frequently connecting/disconnecting hydraulic lines presents the probability of fluid leakage and the introduction of contaminates and air which must be bled.

Originally Posted by Old Scout

...realize it is a bit apples and oranges but if vehicle weight and size were the only factors here, then 747s would have air brakes?????

They may have air brakes as a very last resort but I doubt it. I have ridden on the jumpseat in a few 747s from the Classics to the -400s but never trained on them. Given the number of engines with thrust reversers and for redundancy in generators and hydraulic pumps they probably have emergency braking pretty well covered.
The F-4s I flew and taught in had an air compressor under the front seat to provide air for braking (but not differential braking) in case all the hydraulic fluid was lost from the Utility Hydraulic System. We used it primarily as a parking brake if we needed to get out of the cockpit, usually for "urgent physiological reasons." Otherwise, a field arrested landing using the tailhook was the preferred method of getting stopped with a hydraulic failure.

The F-4s have 3 independent hydraulic systems powered by 2 hydraulic pumps on each engine. Each pump produces 3000 + or- 200 psig. I was taught to never stick a hand near a pressurized aircraft hydraulic line because if it had a pinhole leak you could easily lose a finger or worse.

Commercial aircraft systems are more dangerous because they use an almost invisible clear hydraulic fluid rather than the red MIL-H-5606 fluid the military uses.

Originally Posted by Old Scout

......both braking systems have their pros/cons, and both require periodic maintenance to function properly....

True but because I drive my coach towing a toad in the mountains a lot and brake fluid can boil in the lines when the brakes get hot and is flammable I prefer air brakes in a heavy vehicle.

[wolfe10]

Originally Posted by FL420

True but because I drive my coach towing a toad in the mountains a lot and brake fluid can boil in the lines when the brakes get hot and is flammable I prefer air brakes in a heavy vehicle.

Brake fluid (unless brake fluid changes every couple of years are not done) boils at over 400 degrees F. If brake fluid gets that hot, the driver is doing something VERY WRONG! 400 degree fluid with the much higher temperatures at the shoes/pads would likely also crystallize brake shoes/pads and check the drums/disks.


I have had DP's with air and those with hydraulic brakes. Both worked very well and with normal preventive maintenance, no issues with either type in over a quarter million miles.

[FL420]

Originally Posted by wolfe10

Brake fluid (unless brake fluid changes every couple of years are not done) boils at over 400 degrees F. If brake fluid gets that hot, the driver is doing something VERY WRONG! 400 degree fluid with the much higher temperatures at the shoes/pads would likely also crystallize brake shoes/pads and check the drums/disks.


I have had DP's with air and those with hydraulic brakes. Both worked very well and with normal preventive maintenance, no issues with either type in over a quarter million miles.

When liquids get hot they expand. Since liquids are basically incompressible they greatly increase the pressure inside brake lines possibly causing line rupture and leaks at fittings.
No thank you. And yes, I know very well how to take care of MY brakes be they air or hydraulic.

[Tom and Patty]

Alpines have a redundancy. The coach has an electric boost if the hydraulic system goes out...engine failure. It is tested by stepping on the brake pedal before starting it. However, unlike air, the brakes engage work if a line breaks.
The 35K pound coach stops very well with hydraulic brakes. And response time is instantaneous[emoji3]. My 2000 has disc all around.
BTW an Alpine could get spec’ed with air brakes at a discount.
I do hope they know what they are doing and thank you for helping them. Kinda scary[emoji15]

[RVPioneer]

Originally Posted by FL420

When liquids get hot they expand. Since liquids are basically incompressible they greatly increase the pressure inside brake lines possibly causing line rupture and leaks at fittings.
No thank you. And yes, I know very well how to take care of MY brakes be they air or hydraulic.

I believe the point that Brett was making was that if someone is applying the brakes in such a manner that boiling the brake fluid became a concern, well, the brakes would be useless and quite possibly, on fire. This type of braking technique would yield equal results with either an air or hydraulic system. We’ve all seen it and smelled it.

We’ve all pulled toads over mountain passes with our hydraulic disc brake equipped coaches. I rarely touch the service brakes on a descent. The Jake in low usually holds a comfortable speed. When slowing is required a flip of the switch to high will quickly reduce speed as needed.

Both systems work well. You’re comfortable with yours and we’re comfortable with ours. All of us.

[FL420]

Air Brakes or Hydraulic Brakes?
https://www.worktruckonline.com/1480...s-the-question
Considerations when specing your next small, medium or large vehicle.

[Hayduke]

Originally Posted by FL420

Air Brakes or Hydraulic Brakes?
https://www.worktruckonline.com/1480...s-the-question
Considerations when specing your next small, medium or large vehicle.

Interesting that when I search for "hydraulic vs air brakes", I see the link you provided. Second. You conveniently skipped the first link.

This one. https://www.constructionequipmentgui...mparison/12756
Paints quite the opposite view of air vs hydraulic. Nice thing about this article, is they point out some specific reasons hydraulic are better. The one you linked is a little light on specifics. They mostly seem to suggest an attitude of, "this is how it's done".

It's already been said, but the air brake advocates never seem to address it... why do aircraft use hydraulic brakes, especially the large 747's, if air brakes are better on larger equipment?

Please read the article I linked, ie the FIRST search result.
TLDR version: air brakes came from railroads, so older tech was more reliable for heavy equipment many many years ago. As tech has advanced, hydraulic systems now outperform air systems. Unfortunately, we have the 'fiddler on the roof' syndrome happening, ie tradtition!

I get it. You like air brakes. We will both have to live with the fact that we're probably never going to agree on everything. That's a good thing though. It's the variety of different people in this world that made me want to get in an RV and go explore in the first place.

[paul65k]

Originally Posted by Hayduke

Interesting that when I search for "hydraulic vs air brakes", I see the link you provided. Second. You conveniently skipped the first link.

This one. https://www.constructionequipmentgui...mparison/12756
Paints quite the opposite view of air vs hydraulic. Nice thing about this article, is they point out some specific reasons hydraulic are better. The one you linked is a little light on specifics. They mostly seem to suggest an attitude of, "this is how it's done".

It's already been said, but the air brake advocates never seem to address it... why do aircraft use hydraulic brakes, especially the large 747's, if air brakes are better on larger equipment?

Please read the article I linked, ie the FIRST search result.
TLDR version: air brakes came from railroads, so older tech was more reliable for heavy equipment many many years ago. As tech has advanced, hydraulic systems now outperform air systems. Unfortunately, we have the 'fiddler on the roof' syndrome happening, ie tradtition!

I get it. You like air brakes. We will both have to live with the fact that we're probably never going to agree on everything. That's a good thing though. It's the variety of different people in this world that made me want to get in an RV and go explore in the first place.

Damnit Kevin, don't argue with this guy....... don't you realize facts are irrelevant when you are more interested in defending your position of ignorance.......this is afterall the internet....what the heck are you thinking??

[FL420]

David Ewel, the author of the link you posted works for....MICO Inc.

Originally Posted by Hayduke

Interesting that when I search for "hydraulic vs air brakes", I see the link you provided. Second. You conveniently skipped the first link.

This one. https://www.constructionequipmentgui...mparison/12756
Paints quite the opposite view of air vs hydraulic. Nice thing about this article, is they point out some specific reasons hydraulic are better. The one you linked is a little light on specifics. They mostly seem to suggest an attitude of, "this is how it's done".

It's already been said, but the air brake advocates never seem to address it... why do aircraft use hydraulic brakes, especially the large 747's, if air brakes are better on larger equipment?

Please read the article I linked, ie the FIRST search result.
TLDR version: air brakes came from railroads, so older tech was more reliable for heavy equipment many many years ago. As tech has advanced, hydraulic systems now outperform air systems. Unfortunately, we have the 'fiddler on the roof' syndrome happening, ie tradtition!

I get it. You like air brakes. We will both have to live with the fact that we're probably never going to agree on everything. That's a good thing though. It's the variety of different people in this world that made me want to get in an RV and go explore in the first place.

WHAT WE DO

MICO designs and manufactures hydraulic and electrohydraulic components, controls and brake systems for Off-Highway machines.

Providing custom solutions for the world's toughest machines; keeping your off-highway operation on the right track.

Consider the source. Follow the money.

[rrthor]

Did anyone mention our hydraulic brakes have ABS.