# USAT's SP Hydra-Cushion Boxcar & Kadee 830s



## Ted Doskaris (Oct 7, 2008)

USAT's SP Hydra-Cushion Boxcar & Kadee 830s Vignette

I recently received my first 50 foot double door box cars - being the USAT Southern Pacific Hydra-Cushion car and its predecessor companion, the 50 foot conventional DD box car.











The first thing I noticed about the Hydra-Cushion car as configured by USAT is its Bettendorf type trucks having friction bearing journals. Being somewhat familiar with SP this seemed inappropriate given the era of the car, so having checked in several books, these type SP cars were equipped with the newer roller bearing type trucks. Another thing also apparent is that the Hydra-Cushion cars have projecting draft gear / couplers.

A picture of a similar car to that of the USAT Hydra-Cushion car can be seen at the link for SP's B-70-16 Box Cars.

So whilst the USAT conventional DD box car was easy to retro fit with Kadee 830s and your good to go, the Hydra-Cushion version needed some changes as will be described.


First - The coupler issue:

Having given consideration as to what coupler projection should be reasonably attained, I decided to mount the Kadee 830 box with a 0.70 inch face projection from the end sill of the car.
Though the prototype projection can be as much as 0.90 inch (when scaled to 1/29), the Kadee 830 box just does not look right if doing this. (The prototype actually has a narrower draft gear box cross section than the rectangular shape of Kadee 830.) So I compromised on this issue and chose the shorter projection - still sufficient to emulate a Hydra-Cushion type car.

Shown below is a drawing as to how I modified the Kadee 830 box, its lid, and the car's floor pad area to accommodate the projected box.











Shown below is the car floor pad area with the three new holes drilled and tapped for using the Kadee supplied 2-56 screws. (Alternatively, you can body drill for the 2-56 screws, and use the Kadee supplied nuts that can be installed with your fingers when reaching your hand through the side doors.)











For mounting purposes, I placed the additional two holes in the 830 box / lid so operation of the coupler shank would not be restricted. Though it was tempting to place the two holes near - but just below - the existing side holes, this would result in them being unacceptably located at the car's end sill area when mounting the box with the desired 0.70 inch projection.











Shown below is the Kadee 830 coupler assembly mounted to the car having the chosen 0.70 inch projection. (Note the supplied USAT extra uncoupling rod meant to straddle the Kadee 830 box was installed, too.) 












Now for the Trucks:

Available trucks include several possibilities.
Shown below from left to right is the car equipped with my choice of Aristo's Barber truck - but having AML wheels installed. At the center is the USAT Intermodal truck. At the far right is (was) the originally installed USAT Bettendorf friction bearing truck.











I used the AML metal wheels in the Aristo Barber truck because they were finished in black and had the widest back to back wheel spacing whilst being in specification using a gauge to check it. (Though not exact, this truck seem to best resemble the prototype, too.) 











Both the Aristo ART-29111D wheels and USAT wheels were too tight and out of spec.
Moreover, using wider back to back spaced wheels helps facilitate the 50 foot car to traverse 8 foot diameter track because of wheel proximity to the Kadee box during such an operation - though there is an ever so slight rubbing against the side of the Kadee box. Filing the side of the box in this area at the contact angle of the wheel should resolve this, and it won't take much material removal to do this. 
I am letting the wheels leave a tell-tail mark before doing this.
(My layout only uses the smaller 8 foot diameter track for its rail yard approach.)











The one problem I have is trying to affix the simulated Aristo bearing caps on the tips of the AML axes as these are about 0.010 inch less in diameter than the Aristo axle tips. (The caps normally press on the Aristo axle tips for their retention.) For the time being, I have used a drop of glue to secure the caps.

Shown below is the installed Aristo Barber truck with AML wheels on the USAT SP 50 foot Hydra-Cushion boxcar.











Shown below is the coupler alignment with the Kadee 880 gauge.











Shown below is the conventional USAT 50 foot DD box car in the foreground and the USAT Hydra-Cushion car in the background. The Hydra Cushion car's added coupler projection is very noticeable.











-Ted


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## Nicholas Savatgy (Dec 17, 2008)

Nice job Ted, Those 50ft box cars really look nice dont they???


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## fsfazekas (Feb 19, 2008)

Wow gotta get me some of those....Nice job!


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