does Non-Electric 2-Rail Work with 3-Rail

No problem electrically speaking.  If it has scale trucks it may not like going through 3 rail switches.  A long car may also have problems with tight curves.

Electrically there is no problem.  2 rail cars insulated wheels, which makes no difference to 3 rail.  

Mechanically, 2 rail cars have smaller flanges, so they probably will not work well on traditional O gauge round-top tubular track.   Years ago, I had a layout with Gargraves 3 rail track that had flat top rail.   The cars with scale wheels worked fine on the track.   They did balk once in awhile on the switches but usually that was ok.   Some adjust maybe necessary on older switches.   

No such thing as a stupid question. Scale cars are fine on "flat-top" rail -- Gargraves/Ross, Atlas, MTH RealTrax, ScaleTrax, and Lionel FasTrack. You will likely have issues backing cars through curve-replacement (e.g. O-72, etc.) turnouts. In the example below, the CNW locomotives are scale-wheeled MTH GP38's that run on 2-rail and 3-rail track; the cars are Weaver with scale wheels.

I have some 2-rail rolling stock I built using MTH 2-rail trucks.  No problem running on 3-rail Atlas track and even goes through my #5 Atlas turnout without any problems.

I have a number of 1970's era Atlas 2 rail freight cars that with very minor mods works well on 3 rail track. Varies with model.....fine scale models may have issues.

I mix and match cars with three rail trucks and two rail trucks all the time without issue.  Yes they bounce a little through the turnouts, but I don't have any issues with derailments.  My goal is to have a fleet of era appropriate cars that will are "dual service" for use on my 2R layout and my 3R layout.

My own limited experience has been this:  A pair of unknown brand scale trucks with steel wheels I got from a forum member wouldn't begin to stay on my 027 curves; derailed every time.  On the other hand an AHM car with scale plastic wheels has never once derailed.  Go figure.

Maybe it is because the metal ones went on a tender and the plastic wheels are on a bobber caboose.  But that's such a drastic difference in performance - hard to imagine.

Sorry to say but there will be an electrical problem if you are using track activation devices, also won't work on non-derailing switches if backed onto one, as the two rail wheelsets won't complete the circuit because of being insulated.

Two rail wheelsets won't short out, but won't register on track activation devices like the highway crossing signal and 153C contacter.

Lee Fritz

What do you mean by "non-electric" ?

What I think the original person means is a freight car, like a boxcar or gondola, from two rail being used on three rail track.

Lee Fritz

id ran 2 rail box cars on my 3rd rail lionel 072 tube track..one thing you cant run them fast or other wise they can derail easly..

Weight is and isn't THE issue it's one factor. Several factors come into play with scale wheeled cars.

While they roll a bit better than their hi-rail counterparts, you have to factor in that the flanges are smaller and have less "bite" when being pulled in a sharp curve, so a long train can cause string-line derailments on sharp curves, so the weight needs to be concentrated toward the front of the train.

Curves need to be broader for long trains. My experience running scale-wheeled at the club has been that even with 48" radius, if the train is too heavy, the front cars derail unless there's a pusher at the back of the train -- i.e., you run sync'd multiple units with the last one at the rear of the train.

The rail head needs to have a more prototypical shape -- i.e. a "flat" top and an edge for the flanges to grip onto. Round top tubular track like O-27 and standard O Gauge tinplate track won't work well with scale wheels. Scale wheels will slowly pull through O-72 round-top with a short train but will be toast when they hit a turnout, the train is too long, or it's run too fast. So round-top isn't really a viable track option. ScaleTrax, RiteTrax, FasTrack, Ross, Gargraves, and Atlas-O track will handle scale wheels, but curve-replacement turnouts present potential problems when backing a train because of the frog configuration.

Too little weight in a scale-wheeled car (and even a hi-rail car) is a BIG problem because it will bounce. Fortunately, Atlas' Masterline cars are weighted to NMRA recommended practices 5 ounces plus 1 ounce for physical inch of car length (end-sill to end-sill). This puts a 40-foot car at 15 ounces. Citrus Empire had a rule of 4 ounces per axle which made setting up a train a little easier. Either works well with scale cars, but overall train weight needs to be considered.

The irony of scale-wheeled equipment is that you have to think and operate in a manner that more closely mimics the prototype with respect to operating speeds, train lengths and motive power arrangements. By the way, if an H.O or N scale operator comments about O gauge hi-rail flanges, (proportionally speaking) hi-rail flanges are nothing compared to what they are in smaller scales.

Hope this helps.

I've just acquired some old Athearn O scale cars with scale trucks.  They've been behaving pretty well on GarGraves track and Ross switches.  (So far anyway)  Athearn trucks and KD couplers really look great and kinda makes a guy want to leave 3 rail altogether!  (yeah, right!)

AF

Over 10 years ago, I suggested dumping the fast-angle hi-rail wheel in favor of the old-school code 172 scale wheel (and got blasted over it). This was in connection with a few Forum members proposing the "Hi-Rail 2000" standard for couplers and wheel sets for better inter-operability between equipment of different manufacturers.

The old code 172 wheels work very well with Gargraves, Atlas, FasTrack and MTH flat-top rail. They also don't dip as badly in the frogs because the flanges are larger. The up side is that because of the correct back-side wheel spacing for scale track use, they pass through 2-rail turnouts and crossings on Code 148 rail. I do buy the occasional vintage O scale car primarily as unusual items for my collection, but I have run them on the club layout.

This question is pretty pertinent to me right now. For better or worse (mostly better), I just acquired this beauty: 

It's one of the MTH 3/2 convertibles. It has the 3-rail wheels installed, but it came with the 2R wheelset, and Kadee couplers. Now I'm wondering what to pull behind it!

Protocouplers don't seem to be an option with the fixed pilot models, but I was thinking I could convert a couple of my Weaver cars to Kadee and 2R wheels. (I also have a couple of Weaver Katys (Katies?) coming from a forum member, so they're candidates as well.)

It's not like I'm running on a huge layout - just Carpet Central - so I don't need a lot of rolling stock, just enough to have fun. 

Is the combination of 3R wheels and Kadees ever done?

Fred

I have the same locomotive, but I kept the scale wheels in mine. I switched some Weaver cars over to scale wheels and Kadee couplers, but you can do it with the hi-rail wheels if you shim the bolster for the flanges and shim the couplers to the right height. I wanted the lower ride height, plus I need a couple of trains' worth of cars for when I operate with a 2-rail group.

The only source I know of is Northwest Short Line. They still cut them. 172's will wobble, but not as much as the current standard 145's.

Thanks Matt.

I'll check out NWSL.

Artie