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Re: BART's new cars: Why hydraulic brakes instead of air brakes?
Author: Dr Zarkoff
Date: 05-01-2016 - 11:32
>Hydraulic brakes are used, but rather rarely in railroad applications.
Actually, on AAR railroads, not at all (unless you count the now retired IC highliners). Some transit operations use them, but their advantages over air brakes are questionable, especially because of the closeness of the machining tolerances involved and the maintenance required to maintain them. Think "Washington Metro" here.
>So far, all I have seen and read about is using as parking brake (also known as hand brake). In a closed system (as a parking brake is), it is essentially unexhaustible.
What if a leak develops somewhere in the hydraulic system? Think "Washington Metro" here.
>Nowadays, parking brakes are typically spring-loaded brakes.
The only spring applied, air released brakes that I know of on railroad equipment can be found on Amtrak's P-40s and P-42s (and their derivatives like the P-32ACDMs). This doesn't mean there aren't other applications out there, and I've heard talk of newer transit equipment having them (Els, subways, lighter than rail vehicles, etc.).
>Their biggest advantage is that they are definitely not exhaustible
Until the brake shoes wear out.
Actually, on AAR railroads, not at all (unless you count the now retired IC highliners). Some transit operations use them, but their advantages over air brakes are questionable, especially because of the closeness of the machining tolerances involved and the maintenance required to maintain them. Think "Washington Metro" here.
>So far, all I have seen and read about is using as parking brake (also known as hand brake). In a closed system (as a parking brake is), it is essentially unexhaustible.
What if a leak develops somewhere in the hydraulic system? Think "Washington Metro" here.
>Nowadays, parking brakes are typically spring-loaded brakes.
The only spring applied, air released brakes that I know of on railroad equipment can be found on Amtrak's P-40s and P-42s (and their derivatives like the P-32ACDMs). This doesn't mean there aren't other applications out there, and I've heard talk of newer transit equipment having them (Els, subways, lighter than rail vehicles, etc.).
>Their biggest advantage is that they are definitely not exhaustible
Until the brake shoes wear out.
