Running 2 rail cars on 3 rail track

The gaps in the rails at track switches may be too long for the scale wheels.  As long as you don't use track switches you ought to be okay.   John in Lansing, ILL

Adding to Johns reply about Atlas switches, when high flange wheels traverse the switch gap, the flange of the wheel takes over and the weight of the car rides on the flange along the floor of the gap. The elevation between the floor of the gap and the top of the rail is very closely matched to the height of a three rail wheel's flange. High flange three rail cars pass through their switches very smoothly with little or no rocking of the cars. If you run 2 rail short flange cars through a 3 rail switch, the wheels passing through the gap are going to drop off the top of the rail down into the gap and really rock the cars as they pass through.

Yes, I have the same experience as Rattler, no switches, no problem.  But then if you run through a straight switch leg, not try to go on the curve, you will be ok.  At least through my Ross tinplate switch. 

I run some cars with scale wheels on my layout of Atlas track and Ross switches. They can be a little finicky but as long as you're watchful it can be done. I run my trains pretty slow and pay close attention any time I'm shoving a scale-wheeled car through a switch.

I know you didn't ask but if you don't like the height of your 3 rail cars you can lower them. Dave Minarik has a post with excellent instructions on how to lower an MTH gon. You can also use that same technique with other MTH cars.

Here are a few pics of cars I've recently lowered; an MTH gon, an MTH bulkhead flat, and a Lionscale box. For the box car I had to remove the bolster and frame from under the truck area and replace it with a 1/8" spacer. The floor is really flexible so you need to glue the remaining part of the frame to the floor to make it rigid.

Joe Shipbaugh

(waiting on #740 Kadees to arrive)

I also run stock 2 rail cars on my layout with no trouble - Ross track, #4 and regular switches.  Nothing larger than 40' cars, O64 min curves although I did the same on my last layout with O54 curves.

I lengthen the frog with a thin shim to close the gap. It has to be thin for the three rail wheels to ignore it, they're so wide, and the two rail wheels can ride on it. Lots of trial and error, but doable.

Our layout is all Atlas O solid nickel silver track, with only one spot at 072 curve (all other curves are larger than 072). I have modified each turnout to accept 2-Rail scale wheeled freight rolling stock, by adding thin styrene shims on the top of each and every guard rail (thus the height of the guard rails are now the same as the running rails). Many of the scaled wheeled cars do make some noise going through the 3-Rail frogs, but derailments have pretty much been eliminated. For what it's worth, I have found that the Weaver 2-Rail Bettendorf freight trucks seem to work best on the Atlas 3-Rail track & turnouts.

Ron H posted:

I lengthen the frog with a thin shim to close the gap. It has to be thin for the three rail wheels to ignore it, they're so wide, and the two rail wheels can ride on it. Lots of trial and error, but doable.

Forgot to mention I use scaletrax turnouts.

I have a few cars...kit-built...for which I used O2R trucks.  But with a caveat....

My track is all Gargraves/Ross, having a good flat-topped cross section for potential O2R truck use.  What I discovered is that OLD O2R trucks....the old die cast ones (often in kit form themselves) that came with metal/wood Athearn, All-Nation, etc. kits...had wheelsets that had pre-NMRA flanges.  These are a tad deeper than the later RP-25 flange contour adopted by most of the 2R industry.  And, having the deeper flanges, they ride/track very well, even through the Ross turnouts.  In fact, I can't recall a single derailment.

Now, these old truck are not the smoothest, free-rolling trucks in the world.  They require some fussing and fine-tuning to have a decent roll quality, but you can't beat the price.....if they came with the kit!!  

So, not a simple answer to your question, but a pleasant surprise for me since I enjoy building/detailing the old rolling stock kits.

KD

AmeenTrainGuy posted:

I have not read all the replies but wouldn't be possible to use a modified 2-rail switch to run the cars?

Since the flange-ways through the frogs are MUCH smaller/shallower on 2-Rail turnouts, the "pizza cutter" flanges of 3-Rail trucks will jump up&down like you wouldn't believe.

Also how hard is it to convert a 3-rail engine to 2-rail? 

Quite a bit is involved, since the wheels are common, i.e. NOT insulated on one side of the engine from the other side, but there are machine shops that do such complete conversions (Baldwin Forge & Machine).

AmeenTrainGuy posted:

I have not read all the replies but wouldn't be possible to use a modified 2-rail switch to run the cars? Also how hard is it to convert a 3-rail engine to 2-rail? 

It can be hard and expensive.

the slight bump when 2 rail cars go through the frog on 3-rail switches is no big deal in my opinion.   

A good way to increase the reliability of the 3 rail switches for the non straight route is to raise the height of the guard as someone suggested, so it actually "guards" the 3 rail wheels.    I did/do it by glueing 1/8 inch square piece of styrene strip to the top the same length as the guard rail.   I then paint this dull black like the guard on most switches.   

It is very difficult to convert 3 rail locos to 2-rail     Steam locos take the most work.   Diesels are easier because you can often buy replacement axle/wheelsets that just drop in.      The wheels have to be insulated and pickups added.   On a steamer this requires moving all rods and wheels and replacing or maching and adding new tires.    

It relatively easy to go from 2 rail to 3 because all you have to do is add 3rd rail pickups

The only thing I'd watch out for is the old Weaver plastic wheel sets. Some of them are ever so slightly out of gauge and will find your bad spots on three-rail flat-top track. I switch them over to Intermountain metal wheel sets. They roll much better and don't have the problems of the plastic wheels (crud build-up, getting track dirty, and gauge issues).

AmeenTrainGuy posted:

Another good question is, can 2-rail engines use TMCC or DCS?

Yes. Atlas used to make 2-rail TMCC engines until 2005/2006 when they replaced TMCC with QSI DCC sound decoders. Now they use ESU LokSound in their 2-rail sound-equipped engines.

MTH scale wheel locomotives can run on either DCS or DCC. I opt for the latter since DCS will only control ProtoSound 2 and ProtoSound 3 engines. DCC allows you to operate any manufacturer's DCC-equipped model.

Thank you all for your input and experiences

I have lowered a few cars but kept the CLAWS on them.

On my holiday setup I am limited to 045 curves and run  small steam and 40 ft cars.

I bought 2 o scale cement cars and put hi rail wheels on them and left the KD's

I will have to see how they run on 045 curves and may convert a few others.

I really love the looks of the KD's!!

Thanks for posting the video, lots of food for thought!!

When I get some free time I'll set some tracks on the floor and do some experimenting with my rolling stock and Atlas switches.

AmeenTrainGuy posted:

I have not read all the replies but wouldn't be possible to use a modified 2-rail switch to run the cars? Also how hard is it to convert a 3-rail engine to 2-rail? 

The electricity is the problem, 2 rails have one positive the other negative so everything about the locomotive has to be isolated so a short circuit doesn't develop.

This  means that all metal wheels and attaching gear drives or in the case of steam the side rods as well need one side at least to be electrically isolated. This means from frames and axles as well as wheels and couplers.

While not impossible it is time consuming and often expensive. Each locomotive must be taken individually to where on diesels the side frames may or may not touch the wheels so isolation will depend on contact or not. At least one sides wheels need to be insulated from the axle, this can be accomplished by boring the axle hole then pressing in a plastic bushing. But getting the wheel firmly attached to the axle becomes a problem where most adhesives are not up to the task thus requiring essentially a means of keying the wheel to the insulator and the insulator to the axle.

Steam locomotives need to isolate the wheels and side rods, typically this is done by machining the hub then placing a insulator between the hub and what becomes its rimmed tire on one side. This results in a center hub wheel that is electrically isolated so then the drive rods are also isolated with only the tire in contact with the rail circuit.

The next problem is how to put the wheel of a diesel or the tire rim of a steam into a circuit that runs the motor, lights, and sounds if used. This is usually accomplished with light spring contacts made of phosphor bronze that are mounted on an insulator that is discretely 'hidden' and lightly in contact with the wheel rim/tire.

This should give you an idea why 2 rail locomotives are considerably more expensive than their 3 rail cousins. It just isn't the fineness of the detail which certainly does add cost, but the electrical systems are far more complex and costly.

Bogie