036 Fastrak vs 042 Tube Track

If the manufacturer specified O42 minimum curve over O36, there is a reason. Safest bet is to trust the manufacturer.

You may also go to your LHS and politely make your case that your purchase is contingent upon testing a certain track configuration right there in the store. Some may oblige, others may just refer you to the manufacturer's declaration.

Be aware that it is much more complicated than just making the turn - there are s-curves, back to back switches, pickup spacing and so much more that is taken into consideration as these values are derived.

Or you could buy-it-and-try-it. It’s only money. Still make a nice shelf queen.

bmoran4 posted:

If the manufacturer specified O42 minimum curve over O36, there is a reason.....

MTH Realtrax is offered as 031 042 054 072 082 The 042 could be based upon what MTH offers. The 036 FasTrack might work fine.

Lionel FasTrack is offered as 031 036 048 060 072 081

Probably the biggest factor when it comes to minimum curve dimeters are turnouts.  The MTH P47 Scale Premier is listed as 042 minimum. HOWEVER, the RailKing P47 is listed as 031 minimum. It sounds like you are already committed to non-scale. Stick with the RailKing product line and you should be just fine. Want better detailing? Look at the RailKing Imperial offerings.

Gilly, I am already committed to scale.  All my locos are Scale Lionel, K-line or MTH  which run fine on 031 (also the manufacture's specification).  I have had some Rail King steamers but they do not compare with MTH Premier loco's detail.  At this time I do not envision getting any more elaborate than my figure eight.  No "S" curves or switches.  I was just wondering if any other OGRers could say "my scale MTH P47 runs on 036".  I dealt with specifications my whole career and know that sometimes they are just a swag.   Jeff 

Jeff, how close to O42 can you go?   Here is a O41 Fastrack compound curve that will likely run a lot of O42.   Add in the width of FasTrack 3.5" wide roadbed, and you need 44.5" of width for the O41 compound. (red sections are O36 quarter, gray sections are O48).  Its not perfectly regular as a circle, but close.   Lots of small sections runs the cost up some.

Right curve is slightly narrower, but less "perfect" IMO.

The left curve has O48 lead-ins, giving you O48 easements in effect.

Well, this version specifically states that it will operate on O36 curves - 20-3461-1 clickety-click

This comes up frequently enough there should be a sticky. MTH and Lionel Fastrack measure their curve diameters differently so a bit of apples/oranges.

A Fastrack "O31" curve measures 31 inches center-rail to center-rail:

An MTH Realtrax curve:

An MTH "O31" curve measures 31 inches to the edge of the roadbed ballast slope.

So to compare apples with apples, an MTH "O31" curve measured center-rail to center-rail:

The Realtrax curve measures 28⅝ inches

So then, a Fastrack curve diameter is 2.5 inches larger than the same numbered Realtrax curve.

Thus MTH "O42" = Fastrack "O39.5".

OTOH, IIRC Lionel O27 tubular track measures 27 inches to the outside of the ties.

Jeff Noll posted:

Gilly, I am already committed to scale.  All my locos are Scale Lionel, K-line or MTH  which run fine on 031 (also the manufacture's specification).  I have had some Rail King steamers but they do not compare with MTH Premier loco's detail.  At this time I do not envision getting any more elaborate than my figure eight.  No "S" curves or switches.  I was just wondering if any other OGRers could say "my scale MTH P47 runs on 036".  I dealt with specifications my whole career and know that sometimes they are just a swag.   Jeff 

My scale MTH P47 runs on o36 just fine. Had it on my Christmas layout. I wouldn’t run it on o31 though; tried this and it wasn’t the best. 

My premier GS4 with the LED Christmas lights also ran just fine on o48 even though it’s rated for o54. 

As long as you don’t race them, you should be okay. It really depends on the engine/car. 

One thing to note as I read above, you said scale P47. Are you referring to the scale wheels version of the premier line or the high rail premier? 

Thanks for everybody's input.  It is with great interest I note that MTH changed the min radii for their premier Blue Comets (high wheels) from 042 to 036 in their newer PS 3.0 locos.  Everything PS 2.0 and earlier are 042???

The analysis of Realtrax and Fastrack is superb!  I just learned something.

My track constraint is the fact my layout is on the floor of my office (like a 12 year old's).  The larger the radii the less room for humans to move around.  I really like the figure eight (another throwback from being 12 years old) and as the radii increases the length of the figure eight grows.  Ideally I would like to have the length limited to seven feet but could be a bit more flexible.

What a wealth of knowledge this forum contains.

I would caution that we are not necessarily “home free” if a unit’s wheels successfully hold the rails on a curve tighter than the mfr. spec. Remember that in doing so, the trucks have to swivel to the max. I have seen the inside of nearly all the units I own, and all too often, the leads between the motors and their other connection points are a bit too short to allow extra swivel without tension. I have also seen the wires from the pickup rollers cut into and shorted by the sharp edge of the unit’s floor. Do the overseas assemblers really save that much money by not asking “what if” and including a bit more slack?

I wonder as well with steamers where an umbilical with four or more wires has to bend more over the life of the locomotive. And what about alignment with the infrared engine/tender couplings? Having written all this, I confess to running a couple favorite locomotives on under spec curves in the hope of “getting away with it.” 

So, here is a FasTrack Figure 8 at 90 long x 40 wide

Perhaps you will be interested in this O44.5 Figure-8.   It goes together nicely, and should run most O42 equipment without speed limitations.

For comparison, a fully O-48 figure-8 will be minimum of 52" wide, so this saves a bit on both length and width.

Here is a variation that breaks down four O-48 full sections, so that there is one O48-Half and one O48-Quarter uniformly between the O36 sections (except at the middle, where there is an O-48-Full section).  There are also three small straight sections in place of the 5" section (times 4).  [The cost goes up a bit with more sections.]

It is fun to connect the Figure-8 with four O-48 turnouts, for more routing options:

And, here is an O48 (no O36) Connected Figure-8 "Squished" 52"x104":

Just playing around:  here is an O43 (compound) Squished Connected Figure-8, in 47"x97":

1" less than 4' wide, and 1" more than 8' long.  Pretty good condensation.

No place to insert O48 turnouts for spurs.

Build an outside frame, trim off 1" from the width of a 4x8, and insert that inch at the end to make 97.

Might make a good Xmas layout, with the tree in one circle, and presents in the other (or the cat).