A journal following the history, design, construction and operation of Bernard Kempinski's O Scale model railroad depicting the U. S. Military Railroad (USMRR) Aquia-Falmouth line in 1863, and other model railroad projects.
©Bernard Kempinski All text and images, except as noted, on this blog are copyrighted by the author and may not be used without permission.

September 19, 2010

P48 Trucks - So this is what the fuss is about!

Paul Dobbs, one of the ACWRRHS members, is building an O Scale ACW layout in P48. For motive power he plans to kit-bash an old Rivarossi plastic model 4-4-0 into a P48 operating locomotive.

Where did this kit come from? Rivarossi was an Italian company founded in 1945. Lionel briefly distributed their models in the United States until Athearn and then Associated Hobby Manufactures (AHM) took over. AHM closed operations in 1985. It is common to find older packaging marked AHM Rivarossi.

Box art from an AHM Rivrossi 4-4-0 Genoa
During their heyday, AHM Rivarossi released at least five American prototype O scale kits including:  0-8-0 Indiana Harbor Belt heavy switcher, 4-6-0 Illinois Central "Casey Jones", V&T 4-4-0's  #12,  "Genoa", and "Reno"
In the 1990s Rivarossi acquired Lima (1992), Jouef and Arnold (1997). In 2003 Rivarossi went into receivership, the last of many times. In 2002 the US importer folded leaving debts greater than the capital value of Rivarossi. In 2004 Hornby Railways PLC acquired assets from Rivarossi, in particular the brands Arnold, Jouef, Rivarossi and Lima. Since 2006 products are sold again under these brand names. To my knowledge the O Scale locomotive kits have not been rereleased. The plastic kits can sometimes be found on Ebay.

I am not sure what powering kit Paul plans to use, but he mentioned that he needed P48 trucks for his freight cars.

I offered to convert some of my Alkem Scale Models trucks to P48 for use on his freight cars. (note these trucks are not yet available for sale, but they are coming soon)

What the heck is P48 anyway? Due to a historical quirk, standard gauge O scale locomotives in the US are made with wheels set to a 1.25 inch (a scale 5 feet) gauge. P48 standard gauge modelers use a correct scale track gauge of 4' 8.5 inches, though it should be noted that some American Civil War era railroads were 5 feet gauge. While they are at it, they also adopt fine scale wheels with realistic tread and flanges. For more information about P48 see http://www.proto48.org/

I modified the design of my O Scale my trucks to accept a p48 wheel set that Paul provided. The photos the P48 trucks compared to my standard gauge O Scale trucks.

The wheel sets in this test have a significant extension of the axle to the outside of the wheel face. As a result, I was unable to make journal covers for the P48 trucks since the axle shafts extended past the journal boxes. Otherwise, the truck uses the same design as my standard gauge trucks, including the working brake mechanism.

The P48 wheels will just barely rest on the standard O gauge track, but they will not operate on it. They require track built to those specs.

So you be the judge, is the difference worth converting all those SMR locomotives to P48? I know what my answer is.

In looking at these photos it occurs to me that I may be able to make the O Std truck narrower by using the same idea I used in the P48 truck. That is, make the axle hole in both the frame and the journal. That would allow the frame sides to lie closer to the wheel faces.  The main problem with these wheel sets in the amount of axle that protrudes from the wheel face. The O Std wheel sets have a pointed axle to reduce friction. But if you don't rely on that point to hold the axles, and use the flat part of the axle as a bearing surface, you could make the overall truck narrower.


  1. Would seem like a lot of work and expensive at this point for a hardly noticible difference.

  2. Answer depends on how you want to spend your time. Are you coming to Utah this week for the Great Basin? I am going to see if I can catch you at one of the layout tours as I would like to meet you.


  3. I will not be at Great Basin this year. But we do plan to head to Utah soon. Send me an email if you want to try to meet up.

  4. Perhaps not the best place to ask but what do you use to create such realistic dirt ballast?


    H Nilsson

  5. It is dirt I collected in Utah. I sellected a type of decompsed conglomerate that had been exposed in a road cut. I found a source of a reddish color such rock near the Jordanelle Reservoir. The red clay in my area doesn't work well in scenery as it cracks as it dries.

  6. How much is the genoa worth

  7. Any possibility in getting some O scale trucks? I would very much like to have them form my Civil War Era Cumberland Valley Railroad. Jus say'n...

    1. Yes, I plan to make some for my Aquia Line. I will make them available on my Alkem Scale Models Website.