Assistance on track clearances with Kato Unitrack

[defor]

So, I've only got a few pieces of rolling stock on hand, and very little track (yet), so I'm having trouble testing this, but what is the actual minimum spacing between tracks that is generally acceptable?

The design I'm currently working on in RailModellerPro needs really close track spacing to match the prototype (after that I'll be shrinking everything and removing a lot of the track so it'll actually fit in my apartment, and not a 26x9ft space!), and I've come up with a combination of 20-221 + 20-121 (or the reverse, 20-220 + 20-121) to create a 27.1mm track pitch.

 

• Will I see any collisions occur on straights, running Koki's and DE10, EF210, EH500, or similar with this nonstandard (at least where standard is the dual-track plate) spacing?
• Also, are there any good solutions for obtaining fractional angles, outside of 15 degree increments with unitrack?

 

I've also looked at non-unitrack solutions, but I like the flexibility of "rip it up and reuse" if I decide to at some point in the future for now as I'm just getting into the hobby... I do wish It didn't come at the cost of raised track ballast. As a partial solution, I'm planning to "embed" the unitrack below the "ground" surface level, so it should camouflage it at least somewhat.
 

[defor]

I should add that I am aware that NMRA seems to say that 25.4mm pitch is minimum on straights (https://web.archive.org/web/20051226034519/https://www.nmra.org/standards/s-8.html), so it sounds like I have clearance, but I'm still wary.

Edited March 13, 2018 by defor

[kvp]

On a straight track, just put the two tracks together until the ballasts are touching. This was the old ttrak standard, still used by unitram. On curves, this is inadequate and for longer stock and at 249 mm 33 mm is suggested. For 300 mm and above it's possible to go down to 25 mm. For smaller radiuses, the minimal distance grows.

[kvp]

1 minute ago, defor said:

I should add that I am aware that NMRA seems to say that 25.4mm pitch is minimum on

Unitram and the old ttrak uses 25 mm. However some larger US outline models would just barely touch, so 25.4 mm for US prototype is a good idea. For japanese stock, unitram/ttrak classic is good.

[cteno4]

defor,

 

one issue with doing the straights butt up against each other with 25mm spacing is getting the points and curves to line up as that geometry is set for 33mm with #4 Kato points and 47.5mm spacing on #6 point and #4 with the extensions on them.

[defor]

Just now, cteno4 said:

defor,

 

one issue with doing the straights butt up against each other with 25mm spacing is getting the points and curves to line up as that geometry is set for 33mm with #4 Kato points and 47.5mm spacing on #6 point and #4 with the extensions on them.

Right, also 25mm spacing doesn't match the prototype I'm basing this on. The closest match I've been able to get by combining parts is around 27.1mm.

Below is the combination (ugly) of parts I need to achieve this- perhaps there's a better solution out there?

Thankfully, I only really need this pitch on straightaways, the actual yard switching is a spaghetti mess, and tons of room (at least potentially), but I'm going to need a lot of short spacer bits to line all these turnouts up right.

[cteno4]

Defor,

 

yep the short, tight 15s will work but can be harder for larger equipment to snake thru sometimes.

 

you can easily make your own custom straight pieces by taking a straight section and just cutting out a section of roadbed in the center of the piece the size you need to shorten with a razor saw in a little miter box. then slide one end of the roadbed down flush with the other once the center section is removed (cut along the track to break the track hold on the rail) and epoxy together on the bottom side of the roadbed. then nip your rails off to the exact length needed and clean (cutoff disc in the roto tool works great for this). then you end up with the needed custom length and unijoiner slots on both ends intact.

 

cheers

 

jeff

[defor]

13 minutes ago, cteno4 said:

Defor,

 

yep the short, tight 15s will work but can be harder for larger equipment to snake thru sometimes.

 

you can easily make your own custom straight pieces by taking a straight section and just cutting out a section of roadbed in the center of the piece the size you need to shorten with a razor saw in a little miter box. then slide one end of the roadbed down flush with the other once the center section is removed (cut along the track to break the track hold on the rail) and epoxy together on the bottom side of the roadbed. then nip your rails off to the exact length needed and clean (cutoff disc in the roto tool works great for this). then you end up with the needed custom length and unijoiner slots on both ends intact.

 

cheers

 

jeff

Aha! that's a great idea- I see, cut out the middle, to preserve the unijoiner mounts!

 

It sounds like a similar method could work for making, say, 10-degree curves.

[bill937ca]

It would probably be best to build a small test section to see how your rolling stock couplers handle the curves. Will loco wheels bind on tight curves? Most rolling stock may work on the minimum, but does it look good? Old t-trak used 25mm but many freight cars were 2 axle cars. Nothing like finding out if you truly are happy with the results.

Edited March 13, 2018 by bill937ca

[defor]

gotcha- need to place some orders in the next few weeks, and I'll check this out!

[cteno4]

1 hour ago, defor said:

Aha! that's a great idea- I see, cut out the middle, to preserve the unijoiner mounts!

 

It sounds like a similar method could work for making, say, 10-degree curves.

 

yep!

[Kiha66]

That looks like a good start defor, one suggestion is instead of trying to fully recreate the yard you can selectively compress to maintain the same feeling while simplifying the track work or removing extra tracks.  Of course making the scale yard could be cool too, just a lot more work to build and will take up a bit more space.

[keiichi77]

Saw this video years ago but it might help in your situation.

 

 

[kvp]

Kato 20-121 is 315 mm, but you could safely go down to 282 mm and all japanese equipment will still work. This is because the double crossovers are 282 mm, so japanese made rolling stock could handle those S curves. 282 mm is also the inner curve of the ttrak 33 mm (alternate/mainline) standard.

[defor]

20 hours ago, Kiha66 said:

That looks like a good start defor, one suggestion is instead of trying to fully recreate the yard you can selectively compress to maintain the same feeling while simplifying the track work or removing extra tracks.  Of course making the scale yard could be cool too, just a lot more work to build and will take up a bit more space.

Oh totally- I'm recreating the yard to understand how it works, then I'll effectively cut it down- I've already gotten most of it figured out (I'll be cutting the yard into about a third of its original size, then reversing the interaction between JR East and Tokyo Metro to better fill a rectangular layout.

 

11 hours ago, kvp said:

Kato 20-121 is 315 mm, but you could safely go down to 282 mm and all japanese equipment will still work. This is because the double crossovers are 282 mm, so japanese made rolling stock could handle those S curves. 282 mm is also the inner curve of the ttrak 33 mm (alternate/mainline) standard.

for some reason I thought 248 was still considered within tolerances, but maybe it's an issue for 3-axle trucks?

Right now I've been reworking a lot of the design to accomodate 481mm radius parts and increase consistency. It's a little wiggly in parts, thanks to the aforementioned issues involving needs for non-standard angles, and realistically VERY deep, what look like almost symmetrical, turnouts, but once I reduce the design to the parts I want to keep, I think most of those issues will go away.

 

16 hours ago, keiichi77 said:

Saw this video years ago but it might help in your situation.

Nice- I actually took the tips yesterday and said "hey, I can totally rework this now that I know I can cut stuff to length, and create partial curves" and redid a good chunk of the design using this, but today, after rethinking it, I decided, "what do I really want to do with my life, buy a ton of unitrack, only to create custom one-time use lengths, or just 'make things work' with default lengths wherever possible, and with that and some more open-ended interpretations, I went back to the drawing board and redid a lot of what I had already done. I'm pretty happy how i'ts turning out, and when I convert it to my eventual design, I think I'll be better off anyway.

[kvp]

7 minutes ago, defor said:

for some reason I thought 248 was still considered within tolerances, but maybe it's an issue for 3-axle trucks?

No, it's the close couplers or some trains, mainly on shinkansen. They don't like sub 280 mm curves, and really look good on much larger ones. 248 mm is ok for most suburban emus and other shorter stock. For S curves (like turnouts), 280 mm is the safe minimum.