Outside swing hanger trucks became popular in in the early 1950's. Their first use for passenger cars was under the "Train of Tomorrow" which lead to the moniker "EMD Trucks". The New Haven conducted a study and found passengers preferred the ride these trucks provided over that of the inside swing hanger trucks used previously. The HN used a variation of this truck under all its post war passenger cars. Santa Fe replaced trucks on many cars with variations of these trucks. They were easier to maintain since many of the bits were on the outside, so mechanical departments liked them. Neither the Pennsylvania nor the New York Central used them.
In the photos shown, notice that all three models share "41", "DO" and "11". The 41 means four wheels and one bolster. Therefore a large percentage of passenger trucks would be classified as "41 somethings". The "D" is for disc brakes. There were clasp brake versions of these trucks, but the disc versions took over early on. The "O" is for outside swing hangers. The "11" denotes a 6" x 11" journal size. The "B" in the first image denotes an 8' wheelbase while the "C" in the other two denotes an 8'6" wheelbase. The 41-NDO offered to S scalers has a 9' wheelbase. The code details differences that were important to people who had to repair them, but in truth, in S scale you are going to use the 41-NDO trucks that Des Plains Hobbies sells to represent any of these. The alternative is to scratchbuild them because the wheelbase is half a foot too long or too short for the car you are modeling. You could try to change the style of shock absorber. The use of helical bolster springs required the use of some sort of shock absorber. As shown above, all three types of shock absorbers were used on these trucks. Pullman's Truck Code did not distinguish between shock absorber types so your best hope is a photo. Note that all three truck photos from the previous page feed to this one. Also note that the Houdaille Friction Snubber has a spring at the bottom of the "tube" whereas the Monroe Shock Absorber has a smaller "tube" sticking out of the larger "tube". The Houdaille Rotary Shock Absorber has a thin metal rod that connects the spring plank to the bolster via the rotary part of the device. I have better photos of these that I will post at some point. The use of helical bolster springs required the use of some sort of shock absorber. As shown above, all three types of shock absorbers were used on these trucks. Pullman's Truck Code did not distinguish between these types. Your best hope is to find a photo. All three truck photos from the previous page feed to this one.
In the photos shown, notice that all three models share "41", "DO" and "11". The 41 means four wheels and one bolster. Therefore a large percentage of passenger trucks would be classified as "41 somethings". The "D" is for disc brakes. There were clasp brake versions of these trucks, but the disc versions took over early on. The "O" is for outside swing hangers. The "11" denotes a 6" x 11" journal size. The "B" in the first image denotes an 8' wheelbase while the "C" in the other two denotes an 8'6" wheelbase. The 41-NDO offered to S scalers has a 9' wheelbase. The code details differences that were important to people who had to repair them, but in truth, in S scale you are going to use the 41-NDO trucks that Des Plains Hobbies sells to represent any of these. The alternative is to scratchbuild them because the wheelbase is half a foot too long or too short for the car you are modeling. You could try to change the style of shock absorber. The use of helical bolster springs required the use of some sort of shock absorber. As shown above, all three types of shock absorbers were used on these trucks. Pullman's Truck Code did not distinguish between shock absorber types so your best hope is a photo. Note that all three truck photos from the previous page feed to this one. Also note that the Houdaille Friction Snubber has a spring at the bottom of the "tube" whereas the Monroe Shock Absorber has a smaller "tube" sticking out of the larger "tube". The Houdaille Rotary Shock Absorber has a thin metal rod that connects the spring plank to the bolster via the rotary part of the device. I have better photos of these that I will post at some point. The use of helical bolster springs required the use of some sort of shock absorber. As shown above, all three types of shock absorbers were used on these trucks. Pullman's Truck Code did not distinguish between these types. Your best hope is to find a photo. All three truck photos from the previous page feed to this one.