Kato switch radii?

[Zack L-J]

This feels like a dumb newbie question, but google isn't quite giving me the information I want.

I've got an old Kato K3 viaduct set, and I want to add a couple of staging yards. What is the correct switch radius to match the curves that came with this set?

Thanks!

[Spruslayer]

The K3 set comes with 12 3/8" r  45 degree curves
Kato offers #6 turnouts with 28 1/4" radius curves and #4 turnouts with 19" radius and compact turnouts with  6" radius

[Zack L-J]

The K3 set comes with 12 3/8" r  45 degree curves
Kato offers #6 turnouts with 28 1/4" radius curves and #4 turnouts with 19" radius and compact turnouts with  6" radius

So in other words there is no match for my curves. Darn. I’ll have to kludge something together.

[Spruslayer]

There are modelers that build turnouts from scratch,i have not tried this and i dont think i have the skills to do so but i feel sure there are members here that can do this.

[robert3985]

I'm no expert on Kato Unitrack turnouts, but after doing some research here: http://www.sumidacrossing.org/ModelTrains/TrackandRoadbed/KatoUnitrack/UnitrackSwitchesEtc/  I find what appears to be the listed diverging radius for Unitrack turnouts, which this site lists as 19" for a Unitrack #4, and 28 1/4" for a Unitrack #6.

This seems to be totally incorrect as the correct diverging radius for a correctly proportioned #4 is 8", and for a #6 is 23" according to Fast Tracks Printable Turnout Templates.

I'm not 100% sure what radius of Single Track Kato Curved Viaduct Track is in your set, but it appears it is the smallest radius, which would be a 9.8" (249mm) radius.

I also notice that Kato warns that some longer cars and engines will not run or have trouble running on their Unitrack #4 turnouts, soooo....the listed 19" diverging track radius would not require a warning.

After doing a bit more reading, it appears that the #4 works for a certain radius of track as a "drop-in"...which takes the place of a section of curved track.  Whether that section of track would be the same as a curved section of Single Track Curved Viaduct is another question, but...it COULD be.

Photo (1) - Photo from Sumida Crossing showing a Kato #4 and a section of curved track:


I'd suggest going to the Sumida Crossing site...and maybe to other sites to find out what works best with placing a turnout most seamlessly into the curved sectional track you have...or, maybe someone here will be able to help more than I can.

Good luck!

Cheerio!
Bob Gilmore

[Maletrain]

As you can see in Bob's photo, Kato #4 turnouts are not prototypically shaped.  They are close to a continuous curve that matches their (nearly) 19" radius track sections, so it is possible to insert them into a 19" sectional track curve without changing the geometry of that curve.

be advised that Kato #4 turnouts have a reputation for locos "picking the points" and derailing - the one not-so-smooth thing in Kato's track component offerings.  There are threads somewhere here on TRW and elsewhere on the 'Net that show how to modify the #4s to solve the point picking problem.  It is a lot easier to fix a Kato #4 than to build a turnout from scratch, even with a Fast Tracks jig.

I use Kato #4s, and some exhibit the problem and some do not.  Where they are located within a track plan as well as individuality of the turnouts seem to be factors that make picking a problem or not.  Sometimes, I have just swapped another turnout into a place where some equipment is picking the points and that solves the problem, and sometimes only filing the notches in the stock rails fixes it.

[Zack L-J]

Thanks for the info, folks! I'll pick up some #4s and see if I can make them work for my crappy lil' layout.

[C62-2]

The R481-15 curve is a drop-in for the #4 turnout, and the R718-15 curve is a drop-in for the #6 turnout. The 15° aspect matches well with the 15° 30° 45° nature of much of the unitrak universe, but the radii for the turnouts and matching curve pieces are designed to get specific track spacings (e.g., for the island platforms), and not to match the radii of the rest of the curves (i.e., the 249/282/315/348 system)

[reinhardtjh]

be advised that Kato #4 turnouts have a reputation for locos "picking the points" and derailing - the one not-so-smooth thing in Kato's track component offerings.  There are threads somewhere here on TRW and elsewhere on the 'Net that show how to modify the #4s to solve the point picking problem.  It is a lot easier to fix a Kato #4 than to build a turnout from scratch, even with a Fast Tracks jig.

Here's a video from Mike Fifer of Fifer Hobby on this topic.

  He has a fair amount of info on Unitrack and other topics on his shop's site.
Fifer Hobby How-To

I use Kato #4s, and some exhibit the problem and some do not.  Where they are located within a track plan as well as individuality of the turnouts seem to be factors that make picking a problem or not.  Sometimes, I have just swapped another turnout into a place where some equipment is picking the points and that solves the problem, and sometimes only filing the notches in the stock rails fixes it.

I've heard that a lot but haven't seen it with my #4's.  But mine are all from the late 80's and early 90's except for 2 (I think) I got in the mid 2000's.  Mine are also all in sidings and "industrial area". I used #6 switches on the main loop (it's mostly a test track)


Another video from Fifer on Unitrack turnouts:

Here's a good page on combining different pieces to make a variety of curve radii that are not the normal ones

How To Make Kato Unitrack Curves Using Multiple Sizes

Kato has a PDF showing a good number of the track pieces.  I don't think it's complete though.
https://katousa.com/wp-content/uploads/2021/03/Download-N-Tracklist.pdf

They also have a site dedicated to Unitrack.  It takes some digging, but there is good stuff here:
https://www.unitrack-kato.com/lineup-en

None of this specifically answers your question but if you need info on Unitrack, these are good links to have.

[Zack L-J]

I freaking love this forum. Y’all are just so great and helpful.