Can you mix 'n match airpacks? - One long one short on an USAF Deuce.

[lino]

http://www.mgmbrakes.com/documents/Section10-Tech.Info.pdf

This discusses, among other things, mixing different stroke air brake actuators on a common axle for an air braked truck. A very different animal from this situation.

 

[gimpyrobb]

As I see it, they work in each other's places, meaning you can put a long one in place of a short one and visea versa. The only thing I'd worry about is if one "can" was a larger diameter than the other.

I say it makes no difference.

 

[zout]

Lino - I totally agree. It was info only as to help others on chambers that do not know how to identify a long stoke from short stroke chamber by looking at it.
Currently to switch either chamber the S cam has to be changed as well as the FMVS has shortened the stopping distance by forcing this compliance. Both done equally on the same axle.

Our stuff - it was just helpful info - even if the language helped one it was worth it.

 

[rustystud]

As I see it, they work in each other's places, meaning you can put a long one in place of a short one and visea versa. The only thing I'd worry about is if one "can" was a larger diameter than the other.

I say it makes no difference.

Your right, it makes no difference. The long and short air-pac share the same size air chamber piston,and hydraulic pistons. So the amount of pressure applied will be the same in both systems. The long system will of course have more volume then the short, so you cannot (or should not) use the short air-pac in a single hydraulic system. Especially if you go with the larger wheel cylinders, but in the dual system it is a none issue.

 

[welldigger]

Your right, it makes no difference. The long and short air-pac share the same size air chamber piston,and hydraulic pistons. So the amount of pressure applied will be the same in both systems. The long system will of course have more volume then the short, so you cannot (or should not) use the short air-pac in a single hydraulic system. Especially if you go with the larger wheel cylinders, but in the dual system it is a none issue.

I have found zero evidence that it matters one way or another which air pack the truck has regardless of split or single circuit brakes. The master cylinder volume is the limiting factor. Not the air pack.

 

[rustystud]

I have found zero evidence that it matters one way or another which air pack the truck has regardless of split or single circuit brakes. The master cylinder volume is the limiting factor. Not the air pack.

The Master cylinder applies the air-pac, then the air-pac applies the pressure to the wheel cylinders. Actually that is a over simplification but in general that is what happens.

 

[rosco]

I don't mean to hijack this thread, but does air pressure effect operation, or just volume? The "low air buzzer" comes on at 60 PSI, so that must be intended minimum, in a Deuce. The dashboard gauge reads a maximum pressure of 120 PSI, so the regular operating pressure must be less. What is the governor set for? It must be less then a vehicle with a full air brake system - their dashboard gauge reads a maximum pressure of 150 PSI. Many want to class the "air over hydraulic" brake systems, in the same class as the "air brake systems", but they operate differently, and at different operating pressures. This is especially true of DOT Inspectors - while they may be versed in air brake systems, few are in the "air over hydraulic" systems.

 

[welldigger]

The Master cylinder applies the air-pac, then the air-pac applies the pressure to the wheel cylinders. Actually that is a over simplification but in general that is what happens.

Exactly. So if your shoes are way out of adjustment then the MC runs out of fluid/stroke on a single circuit system. It doesn't matter which airpack you have. The result is the same.

 

[peashooter]

Yes, you are.

A look at the TM will help you better understand it. Look at the parts TM for the brake lines.

Incorrect, they do independently control circuits. The driver's side airpack controls the rear axles circuit and the passenger side airpack controls the front axle circuit. Id be comfortable using one of each airpack on my truck.

 

[welldigger]

I don't mean to hijack this thread, but does air pressure effect operation, or just volume? The "low air buzzer" comes on at 60 PSI, so that must be intended minimum, in a Deuce. The dashboard gauge reads a maximum pressure of 120 PSI, so the regular operating pressure must be less. What is the governor set for? It must be less then a vehicle with a full air brake system - their dashboard gauge reads a maximum pressure of 150 PSI. Many want to class the "air over hydraulic" brake systems, in the same class as the "air brake systems", but they operate differently, and at different operating pressures. This is especially true of DOT Inspectors - while they may be versed in air brake systems, few are in the "air over hydraulic" systems.

The more air pressure the more brake boost.

 

[rosco]

The more air pressure the more brake boost.

To a point, and that's my point: skidding wheels is all that you need, and then its over kill. What is the mean operating pressure? Certainly less the the 120 psi found in air brake systems.

 

[rustystud]

According to what I have read 80PSI to 100PSI is the optimal range. It will still stop at 60PSI , though you will be in the danger zone of being able to lock-up the brakes any lower. Hence the warning alarm.