Last month I bought a pair of BLI Pennsy P70 coaches. These were the earlier non-AC versions. I have been very impressed by how smoothly and freely the wheels roll. These are easily the smoothest rolling stock I have. This morning I decided to turn one of them over and take a look at the trucks. I hadn't noticed this before but I was surprised to see they are two axle trucks. Prior to this I was always under the impression that passenger cars from the heavyweight era all had 3 axle trucks. Was this unique to the P70 coaches and why were they able to operate on two axles when all other full length heavyweight coaches I am aware of needed 3 axles?
I found this website with the specs for all the versions of the P70s over the years and all show 2 axle trucks:
The P70 in the Pennsy Coach Fleet (pennsyrr.com)
Yes 2DP5 trucks are correct for PRR coach's. Having ridden them many times they were very smooth riding on the corridor where I rode in them
1) The PRR had a very heavy track structure so they didn't need to spread the weight over six axles instead of four.
2) PRR was notorious for using the least number of axles possible on its steamers (prefering by a 2 to 1 margin the 2-10-0 Class I1s over the the 2-10-2 N1s and N2s, not adopting the four wheel trailing truck (on the J1's) until two decades after everyone else, feeling that reduced maintenance costs). The same logic may have applied to passenger equipment
3) The PRR could afford to keep its tracks and roadbed in anything from good to excellent condition, which meant the better ride qualities of 3 axle vs 2 axle trucks would not be noticable
4) A quick glance at the P70 diagrams in the PRR Equipment Diagrams site shows them all with 4 axle trucks
5) IIRC, many Northeastern roads, including the NYC, RDG and CNJ also used 4 wheel trucks on coaches - maybe Eastern roads made more money due to higher traffic caused by the large cities located there and could afford better track and roadbed
A while back I was busy building a roster of commuter coaches using the design of the Pressed Steel Car Co. single or paired window coach. In researching the use of two or three axle trucks, particularly to the New York Central, I found that the three axle trucks were replaced by the two axle, drop equalizer type when air conditioning was added.
Coach_two-or-three-axle by Edmund, on Flickr
(Why did Walthers turn the axle generator 90°? Gotta fix that!)
This didn't make much sense to me since I would figure the A/C would actually add weight to the car but who can argue with the railroad's engineering department.
I've found as-built photos of the cars with both 2 and 3 axle trucks:
Pressed-Car by Edmund, on Flickr
2-21_prints_0014 by Edmund, on Flickr
141 006 by John W. Barriger III National Railroad Library, on Flickr
My preference on these heavyweight coaches is to use the two-axle truck since it is what I'm used to seeing under these however I rely on the prototype photos for specific cars such as the Erie 1000 series coaches which always had the three-axle trucks. Of course journal size and truck design determine the truck capacity.
You can read about the NYC's reasoning behind the trucks here:
https://nycshs.files.wordpress.com/2014/03/nycheavyweightcoacharticle.pdf
A P70 at the builder, 1922.
9312 001 by John W. Barriger III National Railroad Library, on Flickr
You can bet the accountants were looking at the costs of that extra axle, too. With over a thousand cars in the P70 class that's a lot of journals to repack and wheels to true. From what I've gathered the brake shoes had to be replaced in less than a weeks time on the main-line trains traversing the Alleghenies.
Regards, Ed
I think the reason I thought 3 axle trucks were the rule on heavyweight cars because all the models I have from various manufacturers have three axle trucks, the exception being 60 footers. I had no idea quite a few railroads used 2 axle trucks.
Interestingly, the RPO/Baggage car from my Walthers 20th Century Limited set is a lightweight car with 3 axle trucks.
I thought those PRR and NYC coaches were commuter cars which were lighter weight. I used to commute on those NYC cars. Even the EMUs (which I presume would have been heaver) were 2 axle trucks.
Quite a few of the Pennsy's P70s were later modified and upgraded with wider seat spacing, air conditioning (refrigeration in PRR parlance) larger windows and sometimes a baloon roof to match streamlined cars.
The NYC cars didn't get so much of a facelift other than the A/C and perhaps new windows and better seating. Of course during the War years there was a serious shortage of long-distance cars so passengers were reminded to "bear with us" for the duration.
PRR_GI-coach by Edmund, on Flickr
gmpullman air conditioning (refrigeration in PRR parlance)
My dad grew up in Texas during the Thirties where everyone went to the movies on Saturday (double feature, cartoons and a newsreel) in part because it had what the theater advertised as "refrigeration" during those Texas summers (Fortunately, Greenville is not near Houston where you have heat AND humidity - the Astrodome had a reason behind it - and "Friday NIGHT Lights" was called that because you play football at night in Texas because of the heat). So it obviously wasn't just a PRR peculiarity. And, technically speaking, mechanical "air conditioning" IS refrigeration, same principles as the thing in your kitchen but blown up to railroad car size. And if Grandma had an ice box, there were plenty of railroad cars cooled by having air blown over huge blocks of ice, treating you like a side of beef in a reefer car.
https://www.superstock.com/stock-photos-images/4186-14435
https://www.trainorders.com/discussion/read.php?11,4560091
And there was even, in defiance of common sense and the Laws of God and Man, steam activated air conditioned cars.
https://www.trainorders.com/discussion/read.php?11,2971148
https://cs.trains.com/trn/f/111/t/60990.aspx
Actually it's in accordance with Boyle's Law
https://en.wikipedia.org/wiki/Boyle%27s_law
See what you learn by being a railfan and/or model railroader?
BEAUSABRESo it obviously wasn't just a PRR peculiarity.
I only mention it in passing as the PRR added an R suffix to any car class that had a system for cooling the passenger compartment be it ice, steam, ammonia, Frigidaire, Pullman Mechanical. The PRR began installing ice air-conditioning in the P70s in April of 1933.
Note the use of Frigidaire (A GM subsidiary) A/C - I bet some of you of you come from a family where the "Fridge" was called a "Frigidaire", so it was "refrigeration" in the PRR sense
Getting back to trucks. I remember seeing a builders photo of a heavyweight car with a three axle truck at one end and a two axle at the other. It may have been a one off RPO/ coach or even an RPO/ baggage. This was many years ago. I wish someone besides an expensive brass manufacturer would make some HW horse cars and scenery cars. Those would be cool.
Pete.
gmpullmanThe NYC cars didn't get so much of a facelift other than the A/C and perhaps new windows...
Along with the A/C the new windows were sealed and tinted.