help on a figure 8 layout with a 30 deg. crossing

[mikebalcos]

i'm in the process of reviving my old and simple layout. it includes a figure 8 with a 30 degree crossing and 18" radius tracks. i use standard atlas code 100 tracks. since it has been a long time, i do not remember how many 18" radius tracks i need and what kind of short straight tracks i need. it is just a simple figure 8, nothing fancy.

 

[cidchase]

Hi Mike,
RTS comes up with this:
20 AT-152 18" curve
4 AT-150 9" straight
1 AT-175 60 degree crossing

 

[mikebalcos]

thanks for the reply. i guess i have to get myself a 60 degree crossing. so a 30 degree crossing won't make a clean figure 8?

 

[pgandw]

The difference will be in the lengths of the straight pieces. If you are willing to cut some straight or flex track to fit, then you can use the 30 degree crossing. I like to substitute flex track for straight and small fitter pieces anyway to take care of small misalignments and measurement errors. A set of rail nippers to cut the flex and you are done - for less money and time than playing with various sizes of fitter pieces. Even the best CAD software isn't perfect - it depends on how accurately the track was measured for the software and how consistent the manufacturing is of that particular track piece - but it's generally a lot more accurate than the graph paper method.

my thoughts, your choices

 

[LoudMusic]

** nevermind

 

[MasonJar]

Maybe I am not getting the geometery correct, but isn't a 60* crossing the same as a 30* crossing rotated 90*? It just depends on which angle you are measuring - the wide or narrow one...?

Mike - if you rotate the crossing in your initial diagram by 90*, you will require less curved sections and more straights. Also, your table will need to be longer, and the "8" will be more stretched out.

Andrew

 

[60103]

Sorry Andrew, but the other side of a 60 degree crossing is 120 degrees.

However, a 30 degree crossing matches the angle on a single curved track (at 18" radius) so 11 curves each side are needed. I'm not sure about the straight bits. This does make the ends of the circle come in the middle of a curved piece, so you might want 4 half-curves (15 degrees).

 

[pgandw]

David

My oops too - I made the same error as Andrew. I just assumed they were the same crossing but different length on the straight.

MikeBalcos

What I said was wrong about the 30 degree crossing. You would have to redo the track plan with additional curved pieces. The plan wouldn't be as wide, and would have less straight track between the curves and the crossing.

In either case, using pieces of flex track for the straights is still a good way to account for any misalignments caused by track manufacturing or the software measurements being off slightly.

my apologies for leading anybody astray

 

[cidchase]

Rotating the 60 degree crossing gives you this option. The straights don't come out
exactly in either case, but the track joints have plenty of tolerance to make everything
smooth. And, like Fred said, if you want to use some flex track, it's even better. You
just have to do a little tie fitting on the ends.

 

[cidchase]

This one does use a 30 degree crossing.
qty Article no. Description
20 At-152 Full Section 18" Radius
1 At-173 30° Custom Line Crossing
1 At-823 3" Straight (4 pcs./pkg. - 4 Elements required)
1 At-834 1/2 Section 18" Radius (4 pcs./pkg. - 4 Elements required)

 

[MasonJar]

David - thanks for the math lesson...! I can't do geometry to save myself... hamr
'Course it didn't help when I looked up the parts at Atlas, and they showed the same picture for both crossings...

For the record then, its 60/120 and 30/150???

Andrew

 

[mikebalcos]

Thanks a lot cidchase!!! You really made my day. The figure 8 is now perfect (I made a mistake of using 2 3/4 inch straight tracks before you showed the correct layout). That 30 degree crossing sure did save some space. I'll be adding 2 ovals around it soon. My layout is really so simple that you'll probably laugh at. it's just an 8x4, but even with that size i used to have problems fitting it in my room. it made me think that i should rather have used n scale. however, i recently found a way to make things fit.

i'll put a hill on the middle of a half of the layout, and i'll be getting some paper model structures for the other half.


sorry for digressing.

 

[cidchase]

I'm glad that worked for ya, Mike! The Atlas RTS program is great for stuff like this.
The best part is that it's a free download!

 

[fsm1000]

This might help
http://fsm1000.googlepages.com/trackclearanceone
enjoy