• Steel Soldiers now has a few new forums, read more about it at: New Munitions Forums!

  • Microsoft MSN, Live, Hotmail, Outlook email users may not be receiving emails. We are working to resolve this issue. Please add support@steelsoldiers.com to your trusted contacts.

Saw an air braked M35a2 yesterday

Westech

CPL
6,104
207
63
Location
cow farts, Wisconsin
you guys know that most deuces/5 tons are late 60's early 70 production right? I bet you take any auto from that time and drive it your going to have problems if the brake system has not been rebuilt.
Look brakes are brakes. Just because you have air does not mean you can stop any faster then fluid. If you can lock them up the braking system can max out the stopping power of the tires and that is that. your not going to stop faster with air then fluid.
It all comes down to what you prefer.
I for one do not like air on the military trucks. There have been more then one time I was sidelined due to frozen lines and brake chambers. And for all you smart a55es yes I drain my tanks every time I shut down, add alcohol to the dryer and drain the dryer and clean it out. If you compress air you are going to get some amount of water no matter how many times its filtered or what is added to it. Yes some systems are better then other but we are talking about the US government. Everything is supplied by the lowest bidder.
I for one never had a brake loss on my military trucks due to me replacing or overhauling every single part of the braking system. I dont just look at it and go "yup it loos ok to me durrrrrrr". I treat my trucks like air planes.. replace it if it needs it or not. Now yes that is still not a fool proof plan (See wheel bearing and truck stop) but its better then the alternative.
 
429
1
18
Location
Berkeley Springs, WV
I personally prefer air brakes on large trucks mostly for the parking/emergency brake feature. If the air system suffers a catastrophic failure, your truck is going to come to a very sudden halt and you won't be going anywhere. Hydraulic systems don't have that feature. If you lose your hydraulic system in a deuce, you're relying on a small driveline brake to stop nearly 7 tons of steel.

In a full air brake vehicle, if you have a leak in the system and you're not checking it out on a periodic basis, then the compressor will run more often. If it's leaking so much that your compressor can't overcome it, then you will get a audio and visual warning signal in the cab that you are low on air. If you ignore that, eventually the maxi brakes will kick in and you will come to a sudden stop.

In a hydraulic brake vehicle, if you have a leak in the system and you're not checking it out on a periodic basis, then you will lose hydraulic fluid. There is no machine making hydraulic fluid to replenish it in the system, so your fluid level will continue to drop. You will get no audio or visual warning in the cab that you're leaking hydraulic fluid. If you ignore a pedal starting to go mushy, eventually you won't have any brakes and nothing to stop you dead in your tracks.


The only thing an air brake endorsement means is that you can pass a simple test step by step and recite the air pressures at which certain things happen.
 

wehring

Active member
1,375
26
38
Location
Angleton, TX
Single Point Faulure

Single Point Failure... this is what our current brake system contains. Serviced or not it is still one failure away from becoming a 14K missile that the issued parking brake will not phase.

Justin Wehring
979 997 3112
 
429
1
18
Location
Berkeley Springs, WV
As a few others in this thread have already pointed out, the biggest issue with the deuces is the single circuit brake system. If you simply break it into front and rear circuits with two separate reservoirs, then you can have a critical failure of one circuit and still have some braking enough to stop the truck. This is probably what I will do, but I might also fabricate an air actuated emergency brake on the driveline sufficient enough to stop the truck.
 

Kohburn

New member
655
6
0
Location
SOMD
In a hydraulic brake vehicle, if you have a leak in the system and you're not checking it out on a periodic basis, then you will lose hydraulic fluid. There is no machine making hydraulic fluid to replenish it in the system, so your fluid level will continue to drop. You will get no audio or visual warning in the cab that you're leaking hydraulic fluid. If you ignore a pedal starting to go mushy, eventually you won't have any brakes and nothing to stop you dead in your tracks..
that is only on the stock deuce. almost every hyd brake vehicle out there has a pressure switch int he master cylinder that indicates a pressure imbalance between the multiple circuits. for the deuce atleast one person has done a remote reservior setup with a fluid level switch that turns on a brake indicator light.
 

stumps

Active member
1,700
12
38
Location
Maryland
Air brake systems have single point failures too. The treadle is one such point. If it gets its air passage way clogged, or it gets mechanically blocked, you have no brakes. If you think to pull the emergency brake valve, your truck will stop so fast it might go out of control... there is no part way on with the emergency brake. And there is no applying it for just a second to slow things down!

Real catastrophes can happen in the winter. The compressor makes water, and water makes ice. If you don't realize your wet tank has frozen up, and you are punching your brakes to slow down on a long icy hill you can empty your dry tank. When your dry tank pressure drops low enough, your spring brakes will come on whether you like it or not, and then it is skid city. Again, a single point failure.

Sure, there will be some advanced notice in the form of an alarm. But what are you going to do about it?

-Chuck
 

Jake0147

Member
782
18
18
Location
Panton, VT
I've really got to disagree here...

Hydraulic brakes are simpler, cheaper, and more reliable long term than air brakes. That is why they are used on every car and light/medium weight truck on the road today.
Every car, maybe... Light truck? Where are you breaking that class? half tons? No air brakes in a half ton trucks, but how many of those little cabover city trucks have air, and are rated at a lower GVW than a lot of 3/4 ton pickups...

Look at all of the rigmarole that truckers have to go through with air brake systems: Daily checks and maintenance, special training and licenses,
No, not at all. Look at the rigmarole that truckers have to go through because they are commercial. Brakes are irrelevant to that. If you operate air brakes, then you pretrip air brakes. If you operate hydraulic brakes, then you pretrip hydraulic brakes.

finesse with the brake treadle...
That depends what you're driving. FMVSS has set forth minimum and maximum pedal efforts, and any braking system made is free to use the whole range. Both air and hydraulic system manufacturers like to skirt the line both light and heavy depending on their target market. Some treadles can even be adjusted to driver's preferences.

With hydraulic brakes, that can be safely put off to an annual maintenance program. Anyone that can find the brake pedal can make hydraulic brakes work.
Same goes for air. The vehicle won't move until it's safe to do so. Can't say that for hydraulic brakes. Air brakes are not inspected any more than hydraulic brakes. Barring a few states that needed a new law for whatever reason, typically under 26K vehicles do not need any kind of licensing. Nor do the CDL trucks anywhere for that matter. Air brakes are not a "special license", but rather they are a restriction. Are you familiar with the licensing? It's just like a manual transmission. You do not need a special license, but if you demonstrate to the instructor that you can't operate one, he can place a RESTRICTION that you may only drive an automatic... The endorsement on your license for air is not really anything special. It pretty much just certifies you to determine which glad hand to couple together and how to figure out if you got them wrong, which trailers are required to have spring brakes, which trailers and vehicles are required (or allowed) to have which warnings, and covers the pre-trip portion specific to that type of braking system. Used to cover adjusting them too, but manual slack adjusters are so few and far between any more that they no longer cover even that.

Air brake systems had such a bad reputation for catastrophic failure in the 1950's and 60's that the ICC (now DOT) had to insist on double redundant safety systems on every axle
Yeah they did. But then again, they did that with hydraulic brakes too. Either system was typically a single circuit back then, both were prone to catastrophic failure, and it was eventually required that any braking system whatsoever have redundancies and failsafes and warning systems built into them.

; spring brakes that prevent the vehicle from moving even one inch if the air system had a failure anywhere;
Why... Because they CAN... Can you set up a hydraulic drum brake default to a moderately applied mode to serve parking and emergency secondary failsafe stopping duties? Lucas Girling. Nuff said.

alarms and gauges to alert the driver to catastrophic failure;
And hydraulic brakes do what when there is catastrophic failure? Prior to the redundancy requirements, they did nothing. After the redundancy requirements, they did exactly that. The light in front of you is red, and traffic is crossing in front of you, and your brake pedal is flat on the floor... Your car, truck, motorhome, whatever you're driving will inform you that the pedal is on the floor and that it's now OK with the FMVSS people for you to go ahead and wet yourself.

and special training for every driver.
Special training again... Absolutely, but no more "special" than driver's ed. That training (or demonstrated mastery) was already absolutely required of every driver in the US in order to acquire a "regular" license. Air brakes do require a demonstrated mastery. Just like driving cars, you can go to school for this if you wish, you can learn on the job, you can just be born knowing everything and just walk in and take the test. Do you hold it against hydraulic brakes that they are taught in driver's ed, and require a demonstrated mastery before you can get your regular license?

These systems add four or five thousand dollars to the cost of every truck.
That's because you get what you pay for. I'm not seeing the correlation to this though? A deuce already has all of the expensive stuff, deciding to check the "air" or "hydraulic" brake option wouldn't have change the price much, and I suspect air would have been a touch cheaper.
On another vehicle, WITHOUT an air system, you're right it's an expensive up front cost. It's paid for in short order in the reduced maintenance and extended service life of the wearable parts, and a lot less expensive to operate over time, measured in both cash and down time.


The past and present hazards of air brake systems are permanently enshrined in the special training, and constant checking every truck driver is required to get/do before he is allowed to drive an air brake equipped vehicle on the road.
That is an unfortunate misconception that you have about the way the inspection process works. Every commercial driver (regardless of brake types) is required to inspect every vehicle that they drive, including it's brakes and keep a record, as does their employer. The requirement is one of being a commercial driver and applies to every vehicle in commerce. Doesn't matter what you're driving, air or no air.

Why would anybody put up with air brakes?
You should try it before you knock it.

Pretty much for the same reason that some folks want automatic transmissions and power steering: The chief advantage to the air brake system is also its chief disadvantage: the driver doesn't feel any more pedal pressure for heavy loads and hard braking than for light loads and easy braking.
That's just crazy... I'ts a pedal, you push down on it when you'd like to stop... Pedal effort is already mandated and regulated to minimum and maximum levels. If loading your vehicle makes ANY brakes, including hydraulic brakes difficult to operate, then there is a problem with the brakes or there is a problem with the load.

A secondary advantage is trailers are super easy to connect, and add no additional braking effort.
Two hoses and a seven way electrical plug, and two safety chains unless it's on a kingpiin.
Versus electric brakes, with one tether, a seven way electrical plug and two safety chains unless it's on a kingpin... Saved one hookup.
Or Surge brakes, there's a tether, a four way electrical plug, two safety chains...
Not a deal breaker either way in my book...
And the braking effort... If an air or electric or surge brake trailer is causing you excessive pedal effort, then there is a problem with the truck's brakes, a problem with the trailer's brakes, or a problem with the load.

A properly set up and maintained air assisted hydraulic system gives you all of the braking the deuce needs, and gives you easy trailer connection too. The best of all worlds in my opinion.
Absolutely, you are quite right on that point. It will certainly give you all the braking you need. The foundation brakes are awesome, the hydraulic system mediocre, but the job at hand does not at all exceed it's limits, it will do the job quite nicely.

Where the deuce brakes lack is in being high maintenance, short service life for the mechanical components, having no failsafe mechainisms, ZERO redundancy in the event of the smallest of failures, and most often giving no signs of impending failures. This is the issue that people are addressing when they discuss "upgrading" a deuce's brakes, be it air or hydraulic upgrades.
 

m16ty

Moderator
Moderator
Steel Soldiers Supporter
9,579
214
63
Location
Dickson,TN
I am in the "air brakes are better" crowd but there is one slight disadvatage to air brakes that hasn't been brought up. There is a small amount of lag time from the time you step on the pedal until the brakes activate. This is not a big problem but somebody used to hyd brakes will need to be aware of it.
 

stumps

Active member
1,700
12
38
Location
Maryland
Ok, efficiency isn't an argument for air brakes that I have heard before. Care to elaborate Stan?

In my opinion, one of the prime reasons the deuce has become so popular among collectors is they can drive it with a standard Class C drivers license. With air brakes, many states (all?) would require a minimum of a Class B, or Class B CDL, with air brake endorsement.

It's just another driving test... and passing driving tests makes us real men... no big deal.... right?

I know some very bright men who have repeatedly failed the Maryland Class B CDL.... It isn't the driving, or the rules of the road test that is the problem; it's the walk-around portion of the test that does them in.

And, some states don't even have the non-commercial Class A, or Class B, licenses, choosing to standardize on the Federal CDL. That CDL brings with it a Federal mandate for a health exam, minimum commercial insurance coverage, log book, and minimum sleep requirements...

The Federally mandated health exam scares a lot of drivers, because if your blood pressure is above 140/90, you fail. If your BP is lowered by drugs to below 140/90, you have get a new checkup every 6 months. Got diabetes? You fail, with no exceptions for having it under control.

All for air brakes.

-Chuck:deadhorse:
 

stumps

Active member
1,700
12
38
Location
Maryland
I'm not against air brakes, I just don't think they are something to wish for on a deuce. Multiple circuit hydraulics would be a great addition.

-Chuck
 

m16ty

Moderator
Moderator
Steel Soldiers Supporter
9,579
214
63
Location
Dickson,TN
Chuck, TN doesn't require a CDL on anything that is not commercial. You can drive a 80,000lb 18-wheeler (air brakes and all) with a standard class D license as long as it's not commercial. I understand that other states are different though. The roads around here are packed this time of year with farmers (not having CDL) carrying thier grain to market on big air brake trucks.
 

jaxsof

Member
584
15
18
Location
Dundalk, MD
When Uncle Sugar went to air on the (I believe) later(Singles, CTIS) 900 series 5-tons. they had a whole lot of drivers who had to be retrained. We lost a LOT of good drivers in panic situalions in less than perfect weather(rain) on good roads due to all-wheel lock up. I had a 900 series license before the problem, and never had the opportunity to test on the "improved" brakes although i did receive the training. There was a definate lack of pedal feed-back and if the operator was suddenly surprised, people died. I believe they eventually corrected the problem(situation?) with progressive springs. The TrackMobiles I work with now use an air over hyd system, but unlike our "old" trucks, there is no brake application without air. No pushrod. Two master cylinders-one for each side. I have seen both fail, not pretty at all. To be fair, they didnt fail at the same time, operator failed to shop the vehicle when the brakes got weird.

I like air brakes. I also like hydraulic brakes. Pretty much I like a vehicle that stops on command. The low/no air P-Brake is a thing of beauty, until it (the air) fails suddenly. And can we be honest here? Whom among us couldn't stop their truck, albeit in a greater distance with the trans. It isnt what we want, but if you have to, I would hope we would all pass this test, and be able to come back here and tell the rest of us about it. Or at least be able to hug their spouce/partner(PC)/kids/dog/cat/bottle-of-boubon one more time. Always hope for the best, but, Murphy was a grunt, and he will give you a test or two in your life. DON'T FAIL IT!! Be prepared for that possibility.

And Please, Pardon my rambling.
 

stumps

Active member
1,700
12
38
Location
Maryland
Chuck, TN doesn't require a CDL on anything that is not commercial. You can drive a 80,000lb 18-wheeler (air brakes and all) with a standard class D license as long as it's not commercial. I understand that other states are different though. The roads around here are packed this time of year with farmers (not having CDL) carrying thier grain to market on big air brake trucks.
Maryland is similar, but our license classes are A, B, C. A is tractor trailer. B is trucks over 26,000 lbs, and C is cars and trucks below 26000 lbs (used to be D). The system has no means of giving an air brake endorsement on trucks below 26000 lbs, so they require a class B with air brakes endorsement to drive any non tractor/trailer truck with air brakes.

Class B is the same as a CDL Class B, test wise, but is non commercial. It gets you out of the strict log, and medical requirements the Feds require with the CDL... However, not all states have the non commercial Class A and Class B.

In Maryland, farmers are exempt from most things in the vehicle code. We can drive farm tagged tractor/trailers on a Class C drivers license. In neighboring Virginia, farmers must have a CDL to drive any farm truck.

The state laws are a mess. The one thing that is consistent is the CDL... and that is because it is entirely a Federal invention. The Feds can mandate the CDL over commercial drivers because they have strict authority over all things that affect interstate commerce.

-Chuck
 
Top