Passenger Trains > New Disc Brakes vs. Older style

Am really hoping for a few photos to go with this-even ONE of the current Amtrak-standard & those FRA-legal would help immensely? But both are virtually identical. Except that one style is totally (for vented disc brakes used since the steam era into the streamliner era & DEEP into Amtrak Era) is composed of solid internal cooling vents between the outer rims of the disc. The other style has a 3rd rim situated right in the MIDDLE of the vents. I do so HOPE that I'm explaining myself properly??? Other than this difference, the 2 types of discs look virtually identical to the extent one would have to get under the car-or-look closely, to tell the difference! And I just can't recall which is the newer type? Furthermore-I understand that the older type is now FRA-condemned for Amtrak equipment, PV cars, etc.??? Per an Amtrak mechanical inspector I encountered circa 2009 who gave a waiver on a beautiful PV I was lucky enough to ride-think the one wheel set had x-amount of time to go, now long since past. But this older type was in service well into the 2000s, perhaps into the teens. Can anybody help clarify this for me? Words will help! But photos as they say are worth a thousand words! Certainly in this instance. Thanks!

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>The other style has a 3rd rim situated right in the MIDDLE of the vents.

Presumably you're talking about the difference between these two examples. The fins between the rotor's friction surfaces form a squirrel cage blower to cool the rotor. That new type is has an added plated in between the rotor surfaces for additional strength.

>Furthermore-I understand that the older type is now FRA-condemned for Amtrak equipment, PV cars, etc.???

It isn't so much a case of "FRA condemned" as "Amtrak condemned" because the FRA has given all the psg reg stuff to Atk, and then goes along with whatever Atk wants.

>Per an Amtrak mechanical inspector I encountered circa 2009 who gave a waiver on a beautiful PV I was lucky enough to ride-think the one wheel set had x-amount of time to go, now long since past.

This kinds of sounds like you're confusing the issue with wear limits (wheel and/or disc rotor).

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Under heavy brake applications, do the rotors ever glow?

* JB *

prr4828 Wrote:
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> Under heavy brake applications, do the rotors ever
> glow?
>
> * JB *

Lets rephrase your question: During normal or emergency braking applications, do the rotors ever get hot enough to glow or turn red? No. During extended continuous downhill heavy braking, do the rotors ever get hot enough to glow or turn red? Possibly.

When they changed some of the commutes to galley cars they had a disc brake. The trouble was you could only use so much air and then that was it. Too much air and they released. Same with the long haul silver side equipment. Now the old official cars had the regular shoes.(except the 150) They were heavy but you could plan on having good brakes.

When Atk came along and the blended brake you had to change the way you operated a passenger train.



Nudge



Edited 1 time(s). Last edit at 06/28/17 09:47 by spnudge.

>When they changed some of the commutes to galley cars they had a disc brake. The trouble was you could only use so much air and then that was it. Too much air and they released. Same with the long haul silver side equipment.

The gallery cars were built with composition shoes (inherent in disc brakes), and using more than "so much air" would cause weehls slide and the decelostats to pop off. Many of the SP's long-haul cars also had them (such as the Budd-built Sunset cars). By the late 1960s, all of the 80 footers (the so called "Harrimans") had been converted to composition shoes.

> Now the old official cars had the regular shoes.(except the 150) They were heavy but you could plan on having good brakes.

Some of them were retrofitted with composition shoes. After the take-over, the UP has changed them all to ABDX, including the 150.

Red
Glad to see you are back

Englewood Wrote:
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> Red
> Glad to see you are back

Second that motion. Good to see you signed in and writing a post again, Red.

>Am really hoping for a few photos to go with this-even ONE of the current Amtrak-standard & those FRA-legal would help immensely? But both are virtually identical. Except that one style is totally (for vented disc brakes used since the steam era into the streamliner era & DEEP into Amtrak Era) is composed of solid internal cooling vents between the outer rims of the disc. The other style has a 3rd rim situated right in the MIDDLE of the vents.

FWIW, if someone has told you the "3rd rim style" is now the only "legal type of disc brake rotor", they're blowing smoke, because that's all the Capitol Corridor cars have, the "two rim" style (I was by WPOY today and made a point of checking).

I thought that Amtrak's recent grievance with disc brakes was in regards to the hub style or configuration.

There are many older spoked or slotted hub disc which were prone to cracking - the newer solid or integral hub discs are much preferred in general service
and required for Part 238 service.

>I thought that Amtrak's recent grievance with disc brakes was in regards to the hub style or configuration.

This makes sense because hub-plate-rim issues keep recurring. In the late 1960s, there was a campaign to get rid of "3-riser wheels" on freight cars. These were made with a pressure pouring process using three risers, and for some reason the configuration of the risers, actually their remnants in the wheel plates, were acting as stress accumulators which eventually resulted in sudden catastrophic wheel failure. There was a re-run of sorts about 25-30 years later with straight plate wheels: thermal heating of the rim (the tread) was causing sudden catastrophic failures because the plate couldn't withstand the rim's expansion. This was solved by adopting curved plate wheels as standard equipment. The problem was similar to one with chilled iron wheels as they cooled after casting: the curved ribs on the backs of most cast iron wheels are designed to prevent rim-plate-hub separations.

>There are many older spoked or slotted hub disc which were prone to cracking - the newer solid or integral hub discs are much preferred in general service and required for Part 238 service.

The 1961 Carbuilder's Cyclopedia shows both kinds of rotors, the ones with the "two rims" (ASF) and the "tree rim" variety (Budd). Both have a solid hub which bolts to the back side of the wheel hub, but what the book doesn't show are hub details. Without the slots between the two friction faces form a squirrel cage blower which dissipates the heat, otherwise if solid, the rotor would overheat and warp. At the time, Buffalo Brake Beam Co advertized a single-sided rotor for freight service.

The OP was asking whether you could tell the difference between the "legal" and "illegal" discs by counting the "rims", and the answer to that is "no, you have to look a the hub".