Track Curve for MTH Crocodile Scale Wheels

As a 2R'er I am not able to duplicate your brand of track and curvature -- but I can offer the following information:

1.  I have 'your' locomotive, and while my layout does not have any curves of a uniform radius that are that sharp, I was able to set up a short test track using 2R sectional track of about 32" radius;  the locomotive went into that curve OK.  The loco wheelsets and the track were checked and exactly met the applicable NEM standards [ neither of which is the NEM 540 MTH references, as an aside ].  And since 36"= 914 mm [ more or less ], and the latter is the defacto standard minimum radius in post-Lenz Germany, it would be surprising if the loco was not designed to take this radius.  BUT:  That's on 'real' 2 rail track.

2.  The European standard for 2R 0 ga track is 32mm - 0 as the inside dimension between the rails.  You should measure the Ross 36" curves and see if you have at least that distance;  more, up to a point, would be better.  Let us know what you find.

3.  The difference between 2R and modern -- say, post MTH -- high rail wheelsets is not just in the height of the flange;  the back-to-back inside dimensions of the flanges are also different.  An MTH E94 3R wheelset has its flanges approximately 1/16" closer together;  for a given truck this means the greater slop [ "That's an industry term"] between flange and railhead should permit the 3R truck to go around a sharper radius on the same brand of track.

4.  Although in theory it shouldn't make any difference at the 36"radius, it should be noted that the MTH high rail [ "-1 "] versions of the E94 have blind [ flangeless ] drivers in the center axles.

5.  Have you tried this locomotive on the diverging route of any of your turnouts, irrespective of their equivalent radius ?

With best regards,

SZ

@ScoutingDad posted:

. . .

My layout has curves ranging between 36 to 44 inch radius. Track and switches are Ross. MTH suggests a minimum 36 inch radius for this engine.

As far as I understand this engine should take these curves. Anything I am missing???

. . .

Are your curves "O-36" and "O-44"? If so, the locomotive will have issues. Looking at the wheel arrangement, from my experience it looks like you'd need about 36" radius (O-72). My scale-wheel 6-axle diesels with a similar truck wheelbase seem to do fine (Gargraves/Atlas/MTH ScaleTrax).

Hi-Rail wheelsets have the flanges inset substantially (plus at least one flangeless axle) compared to scale wheelsets to accommodate the sharper curves, plus the rounded top of tubular track (and FasTrack). Scale wheels are less forgiving, but I got away with running them on the club layout because the track is "flat-top" rail and the turnouts are #5's which don't curve through the frog.

@AGHRMatt posted:

Are your curves "O-36" and "O-44"? If so, the locomotive will have issues.

He clearly specified radius, so hopefully he's not math challenged and using the wrong term!

@gunrunnerjohn posted:

He clearly specified radius, so hopefully he's not math challenged and using the wrong term!

I know, but you and I have been on this list long enough to know why I posted that.

Thanks everyone for the comments and suggestions. Quite a learning experience going from Hi-Rail to Scale Wheels.  I do understand in the 3R world curvature is referring to diameter (from center rail) while scale (for argument sake I'll refer to scale wheels as 2R) curvature refers to radius. Fortunately 2 times radius equals diameter so I don't have to re-learn differential equations to figure out which is which. I try to use dia or rad when asking these questions, but sometimes I leave things off - my apologies for not being precise. (no I am not trying to be a "smart a##", I appreciate the comments - I had no idea of the significant differences in thinking approach 3R vs 2R)

Getting to the issue - I took the engine to a non-powered test track to see if the engine would navigate into a Ross 72 inch dia curve /  36 inch radius. The answer is yes it will as long as the bed is perfectly flat. It will go into a Ross 80 inch dia curve seemingly easier considering it is such a minor increase in diameter. Back on the layout, it will run a little bit on some curves before derailing. In other instances it will come out of a 90 degree turn, run straight and then derail entering the next curve. It seems the lead wheels are misaligned coming out of the curve but does not cause a problem until the next curve. I cannot quite tell if it will run a Ross switch in the through position, because I have curves leading into virtually all my switches - the misalignment rears its ugly head again.  It is also very apparent what is OK for 3R is not necessarily OK for 2R. This engine shows every dip and flaw in the less than perfect job I did laying my track base - which I do not see (barely see) with Hi-Rail wheels - I thought I did a decent job - yikes!   Yep - found out 2R is far less forgiving than 3R.

My apologies for the crappy photo - I do have the Swiss Hi-Rail version and the German Scale wheel version. As SZ mentioned the Hi-Rail version is missing flanges on the middle wheel set - this is apparent in the top engine directly below the engineer figure. The Hi-Rail version runs fine on my layout.

As some of you may know - my layout is destined to be dismantled as we prepare to move to another home in another state. We just have not found that home as yet. As a result I am hesitant to rip up part of the existing layout to try different track or larger radii curves. I will be able to start fresh with a new layout.  However I do have several sections of Atlas flex 3 rail track which I could insert to see if there is an operating difference between the solid rail track and the flattened tubular of Ross. At this point I cannot address the underlying track base issue. 

Lastly - what is a 3-railer doing with scale wheels? I have a small set of MTH British passenger cars and EU style wagons all with scale wheel sets and representative couplers and I wanted to match them up. Plus I am interested in scale wheels and 2R operations. I like learning new things.

Thanks again to all.  Jeff

I got my introduction to what a 2-rail guy does to build a layout when @Tom Tee came over to help me build the benchwork.  It was actually closer to letting me watch while he built the benchwork, but that's another story.   Stuff that I would have glossed right over as far as leveling, etc. were addressed in spades.  I can honestly say that my current layout is the most level of anything I've ever done!  I suspect that's the difference between your 3-rail stuff running and your 2-rail stuff not running.

If you're really going to get into 2-rail in any meaningful way, I'd suggest you consider 48" radius curves as your minimum on your upcoming build.  For large steam 2-rail, think even larger.

@Steinzeit 

"The European standard for 2R 0 ga track is 32mm - 0 as the inside dimension between the rails.  You should measure the Ross 36" curves and see if you have at least that distance;  more, up to a point, would be better.  Let us know what you find."    ====  I put a manual micrometer on the track to check distances between the rails: Anything less than 1mm reading is a bit of a guess.

• Ross wood ties 36" radius 72" diameter  32mm - pretty uniform down the length of the track section
• Atlas Flex track plastic ties 32mm (-0.5 mm)  - absolutely uniform rail spacing down the track section
• Gargraves wood ties 21" radius / 42" diameter  32mm (+0.5mm) - some minor variation down the length of the track section

Essentially all the track is at the 32 mm standard. However the Atlas track spacing was tighter than Ross and Gargraves was looser than Ross. Maybe 0.1 to 0.3 mm either way.  For what its worth - I do not think Ross 3R Switches will reliably work with scale wheels. Always derailed if the wheels hit the points first - even straight through.

To @gunrunnerjohn  @AGHRMatt  @Tom Tee @David Minarik  thanks for your insights.

Not to be deterred - I put a fine scale coupler on my Hi-Rail Croc (proto coupler was busted)  and coupled it to an MTH British 2-Rail scale wheel Coach. Ran great until it hit the curve. Those couplers are pretty cool being spring loaded and all. End result --  Scale wheels on my current layout are not a workable option.

This has been a fun adventure learning about scale wheels. While I suppose solid rail such as Atlas would perform better than Ross or Gargraves, my layout was not built to the exacting standards necessary for scale wheels. So I'll keep what I have, box it up and lay in a 2-Rail line when I build the next layout - hopefully not later than 9 months from now. I suppose I need a different transformer to run 2 rail DC - yet another purchase to go along with the 2 rail switches and track.

Best - Jeff

Well, that blows my 'tight track gauge' theory out of the water.  I can think of other things to try on the loco trucks that involve swapping some  wheelsets between the '94's, removing pickups, etc, but given your situation [ the move ]  I don't think it's worth your time.

If you stayed with just the MTH locos and rolling stock for the 2R initially there would be no need to change power supplies, just feed the 2 rails [ or catenary + 1 rail ] with your existing AC supply.  You could switch to DC or DCC later.

If you have not done so already, before you go fully into 2 rail try to visit one of the shows dedicated to 2 rail 0.  The 9 month hiatus gives you a good opportunity to not only specifically plan a layout, but more importantly to decide what, in terms of general looks, operation, modeling era and locale, you want.  Having a focused goal will be a big help in planning and purchasing.  Your wallet will thank you.

Have fun !

Best regards, SZ