Tomix Wide PC track end loop

[sandiway]

I'm having trouble designing a Tomix Wide PC end loop.

Consider two variants: one using C354/C317 compound radii curves, and one using C391/C354 radii curves. 

I drew them below. The S99 seems to work for the C354/C317 compound case so that the straight tracks line up side-by-side properly again.

But it seems I'd need a non-existent S94 for the C391/C354 compound case. Hmm. Any thoughts? Thanks very much.

 

 

[JR 500系]

I like the first one much better, it looks symmetrically correct, plus S99 is easily available... I dun think I have seen a S94 though... 

[kvp]

I'm not sure, but it looks like you have two canted track transition pieces back to back in an S curve. That usually leads to derailments, unless there is a full car length of straight between them. (140 mm for conventional lines, a bit more for shinkansen)

 

You could try to add a 45 degree section  between the large curve and the smaller one to remove the S. Also that would allow the use of the same radius for both as the length compensation could be done in the diagonal straigth section. It would be a bit longer but much more stable at higher speeds.

[katoftw]

Two opposing transition pieces together will cause derailments.

[sandiway]

Thanks for the feedback! How about this one? 

Very close to being exact (small gap between the tracks can be taken up in the slack).

Has straights to separate the opposing transition 22.5 degree curves.

Edited August 23, 2018 by sandiway

[katoftw]

The transition pieces have one flat end and one canted end. So no the new version wont work either.

[sandiway]

30 minutes ago, katoftw said:

The transition pieces have one flat end and one canted end. So no the new version wont work either.

I see my problem. The sequence of transition pieces are as follows:

1. C354-22.5 from flat to canted

2. 4 x C354-45, all canted.

3. C354-22.5 from canted to flat.

4. 2 x S280 all flat.

5. C391-22.5 from flat to canted. DANG!!!

6. Won't work with S140 (flat)

7. C391-22.5 from canted to flat.

[sandiway]

Revised version! 

[sandiway]

A friend of mine called this one a lollipop...

[bill937ca]

Why not use a stock rail 354-45 curve for the initial turns?  There would less stress on the couplers and trucks than the twisting and turning in and out of super-elevation.

Edited August 25, 2018 by bill937ca

[sandiway]

8 minutes ago, bill937ca said:

Why not use a stock rail 354-45 curve for the initial turns?  There would less stress on the couplers and trucks than the twisting and turning in and out of super-elevation.

I'm using Tomix Wide PC track. So the cant is important.

[sandiway]

This one uses only C391 for curves.

[sandiway]

A friend just pointed out to me that this also works and is more compact. The C280 receives a warning from Tomix about use with Shinkansen, I wonder why?

[kvp]

280 mm is the minimal passable radius for many shinkansen. Passable means a slow speed is recommended. The setup above avoids a direct S curve, but could be still a problem for cars above 20 m scale length (140 mm).

 

The 140 mm straights could be left out for short cars or when running with bogie mounted rapido couplers. 20 cars with TN couplers will also pass if ran slower.

[katoftw]

If it is for shinkansen. I would use 158.5mm instead if 140mm to increase distance between opposing banked curves due to shinkansen cars being longer than 140mm.

[sandiway]

Thanks for the comments. Revised diagram. We can eliminate the S18.5s with S158.5s as well.