Model Railroading > Atlas U23B (HO) sideframe woes

A word of warning to those wanting to change the truck side frames. Picked up an HO Atlas U23B (Santa Fe) at a local train show last weekend. I wasn\'t sure if the truck sideframes were the ones I needed for my B30-7A BN cabless project. I assumed it was an inexpensive proposition to swap them out, which assumes they are all interchangable. NOT!

There are 3 different sideframes available. Only 2 flavors will interchange sideframes. The EMD Blomberg and FB-2 are interchangeable. The AAR B is not. In order to "swap" the AAR B (Santa Fe) with the FB-2, I will need to purchase whole new trucks since the gearcase assemblies are totally different (presumably due to a wider wheelbase).

The U23B chassis will fit nicely under the Railpower B23-7 shell. The guy at the trainshow took the shell off of the U23B and let me place my RPP B23-7 shell onto it. (That kind of great customer service is why I purchased it from him.) The bolsters match. The couplers need to be stretched about 1/8" on each end, no biggie. However, the trucks are wrong.

Lesson learned: next time get the unit with the correct truck sideframes (FB-2). The units with the FB-2 option are the undec. #8651 (#8650 undec. has the AAR trucks), UP, Milwaukee, and CSX. He had a Milwaukee unit there for $10 less, but I guessed wrong on the sideframes and went with the Santa Fe. Dhooo!

Oh well, I need to order some spare parts from Atlas anyway... ;-)

A correctly rendered AAR-B has a different truck wheelbase than Blomberg or FB-2s, so therein lies the cause of your situation.

The funny thing is, many of us are very accustomed to the abbreviated-wheelbased AAR-Bs on the Athearn four-axle U-boats, so when accurate AAR-Bs were produced in model form (as on P2k FAs, Atlas U23Bs), it looks "WRONG" when compared to the original Athearn, which was truly incorrect in the first place.

If it makes ya feel any better, I kitbashed a BN 2nd-order B30-7AB using Athearn U33B (!!) components, and all-metal FB-2 sideframes from an old company called "Trackside Parts" about 18 years ago now! It looked okay, and well, asides from the fatty hood, still looks better even today in some ways than that RPP B23-7 shell I have lying around.

Cheers,
Harry

Yep, been there done that. :) I swapped some
trucks thru the mail with another guy, cause he
had an Atlas U23B with FB2\'s, and wanted AAR,
and I had one with AAR\'s, and wanted Blomburg\'s
(which I had ordered as a separate part from
Atlas while ordering something else). I\'m pretty
sure Atlas made that distinction pretty clear
when they came out, but it\'s been a few years
since then.

If your interested I have a U-23b drive with FB-2 trucks that need the AAR style trucks. Brand new never run Will swap the trucks for yours even up. Let me know by email. Thanks, Ken McCorry