Can I run 2 rail cars on 3 rail layout?What is the difference in the trucks??

There is not enough flange on two wheel trucks to keep you on the relatively tight curves of three track and get you through three rail "switches"

You should change the wheel sets or complete trucks.

If the cars have no electrical pick ups from the track they will work just fine electrically. Mechanically it depends on if the coupler systems match up.

But, if they have lights in them  they get power from each of the rails just like HO or American Flyer trains do and the wheels are insulated from each other. In that case you will have no lights because in three rail both outside rails are common to return so the lamps will see no voltage drop across them, thus no light.

To make the lamps work you would need a roller pick up that will ride the center rail where the hot side, or opposite electrical potential to the outside rails lives.

The most simple way to accomplish this is to install three rail trucks. 

Good luck and have fun

The answer is "it depends" on the following:

• Is your track tubular (round top) or flat-top (FasTrack, Atlas, MTH, Gargraves/Ross)?
• How big are the cars? The general math formula is that your curves need to be at least three times the distance between the truck bolsters (where they swivel on the cars). For a distance of 12" (60-foot car) you'd need 36" radius (O-72).
• In determining the last point, are your curves large enough?
• Do you have Kadee couplers on at least some of your equipment. I have several transition cars with a scale coupler on one end and a hi-rail coupler on the other.

For the record, I run scale-wheeled locomotives and rolling stock at the club all the time (almost exclusively now). We have a 48" mainline radius (O-96), Gargraves and Atlas track, and Ross turnouts (#5 as opposed to O-72) on the mains. I don't get a lot of derailments on the rolling stock, but some of my six-axle diesels take issue with some areas of the layout. My plan for lighted cars is to just put them on batteries and LEDs. You can see the stuff run on my numerous YouTube videos.

I'd say probably not.  Our club layout is all Atlas, and 2-rail cars derail on many of the Atlas switches.

Two rail cars have no problems on my GarGraves track and O96 curves.  However Ross switches cause problems. The narrow flange on the O scale wheel sets allows the truck to slide going through a Ross switch. The wheel hit the gaurd rails in the Ross three rail switch and cause the car to derail.

Richard

The old atlas/roco cars had two-rail high wheels and will run on atlas three rail

gunrunnerjohn posted:

I'd say probably not.  Our club layout is all Atlas, and 2-rail cars derail on many of the Atlas switches.

Unless the Atlas turnouts are modified, generally 2-Rail SCALE wheels will derail, especially when backing through the turnout. It is an very easy modification; simply glue the appropriate thickness styrene strip shim stock on top of each and every guard rail on the Atlas turnouts. The idea is to have the height of the guard rail the same as the running rail. After the glue dries, simply paint the shims on top of the guard rails black, and you will never see them.

Our entire layout is all Atlas solid nickel silver, and every turnout has been modified. I have no problems with 2-Rail SCALE wheel equipped freight cars and cabooses, even backing through the modified turnouts. Also, for what it's worth, I tend to prefer the Weaver brand of 2-Rail plain bearing Bettendorf freight car trucks, as their wheel treads are just a little bit wider than other brands of 2-Rail freight trucks.

I am just a "LOOPER",so I guess the cars will run on my layout.If the problems are just with the switches,I should have nothing to worry about I guess.And if I ever need to add switches,I can just shim them up,I guess.But for right now,I am limited in space,so I am just running some loops.

kennyb posted:

I am just a "LOOPER",so I guess the cars will run on my layout.If the problems are just with the switches,I should have nothing to worry about I guess.And if I ever need to add switches,I can just shim them up,I guess.But for right now,I am limited in space,so I am just running some loops.

Well OK, but again,,,,,,it depends on what track system you are using, as previously mentioned above. Not to mention how sharp the curves are since 2-Rail SCALE rolling stock have body mounted Kadee couplers.

I have tried to run scale wheels on my layout as I really do like the look of the scale wheels.

That said,  as others have pointed out . . . switches are a problem. I just tried HW's styrene-strips-on-the-guard-rail solution on one of my Ross switches. Big improvement for sure on the most troublesome areas but I'm not entirely there yet. Also my trackwork is not up to snuff as I have occasional derailments on other sections too, where no switches are involved. My switched loop is all O-72.

On my outer loop, which is switchless and min. radius O-80, no problem with the scale wheels. Ross track, BTW.

But, illuminated pass. cars seems a whole other thing! My scale wheel cars are all freight and none are long.

Flat top rail is essential.    The big difference in wheels is that the 2-rail wheels have much smaller flanges.    They do not like round top rail like the old tubular track.    They run fine on old Gargraves.    I had a layout years ago that was all gargraves, including switches and I ran 2-rail stuff without many problems.    I do stick with 40ft cars for the most part.

As for the trucks, it is easy to go 2-rail to 3-rail.   2-rail trucks/wheelsets are insulated on one side.   3-rail are not.  If  you put a 3-rail axle on 2-rail track, you get a dead short.

You do need avoid kinks, your curves have to be smooth.    Also you need to avoid big dips and bumps in the track.   Shorter cars handle the dips and bumps better than longer ones.

Smaller cars obviously handle smaller radii better.