# Curve Question:

Discussion in 'HO Scale Model Trains' started by MCD4x4, Mar 17, 2007.

1. ### MCD4x4Member

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Hi Guys,

I'm looking to build an HO layout on a 4x8 sheet of plywood. There is a train show this weekend and I would like to pick up the track. I know there are different numbered curves, 18, 15 etc.... I have a double crossover that I would like to use. The rails are 1 1/4 inches apart, which curves would I need to use in order to have one loop, inside the other? (what number curve tracks inside, and what number curves tracks outside?) Thanks.
2. ### Russ BellinisActive Member

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The best way to do it is with flex track. The problem with sectional track is that each connection is a chance for a bad electrical connection, and with sectional track you have a connection every 9 inches. The numbers on the sectional track curves give the radius of a circle made with the track sections. 15=15 inch radius, 18=18 inch radius, etc. You would need to use 22 inch radius and 18 inch radius for two curves one inside the other on a 4 x 8 plywood. Your separation between the 2 tracks is fine at 1 1/4 inch in the straight, but in a curve you need to increase it to 2 inches or a bit more to keep the trains from bumping if there is overhang. The difference between 18 inch radius and 22 inch radius will make the distance increase to what you need. I can't tell you how many of each size track to get because I don't use sectional track. You could also use 15 inch and 18 inch, but you would be severely restricted on the size of locomotive and rolling stock you could run.
3. ### YmeBPMember

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I used 18" radius turns and am currently ripping it all up becuase the larger 6 axle engines look very funny going arund them, sometimes they pull the rolling stock off the track becuase of the extreme angles. 22" radius is the reccomended minimum for 6 axle engines and i now know why .

I just (like just ..i'm leaving dap all over my keybaord) put together a connected figure 8 inside a loop for my boys using 18" radius but i only have 4 axle engines for them.

A fellow gauger helped me w/ the plan:

I'm sure he'd be happy to share the plan w/ you or allow me to post it, let me email him to find out.
4. ### cidchaseActive Member

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First, Russ us right on about the flex track. If you want Atlas sectional track it's #532 18" radius sections (6-pack) and #535 22" radius sections (6-pack) It takes 8 sections to turn 180 degrees, and don't ask why they come in packs of six! (The HDB syndrome)

I suggest you check at Trainworld (right in your area) for pricing.
TrainworldÂ®
751 McDonald Ave
Brooklyn, NY 11218
Phone:
718-436-7072
(or trainworld.com)
You won't do any better at a show, except maybe Sunday at 4 if there's anything left!! Look at some track plans to get a better idea of where your layout will take you. For some workable and interesting layout plans, look online, in Model Railroader mag, or the Atlas HO plan book!

And right here on The Gauge we can tell you how we would do it !!
5. ### cidchaseActive Member

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Did you get the RTS to work? Just wondering. It can be sticky at first, but keep at it.
6. ### MCD4x4Member

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Hi Guys,

I would like to have another two track elevated line above the lower tracks. I'm into the NYC Subways. Life-Like has come out with some nice stuff. I happened to win a set on e-bay as well, link below. Would I be able to fit some where off the lower level a few lay up tracks. Maybe a ramp from lower to upper? Or am I pushing it? Thanks guys.

Brian NY
7. ### green_elite_cabKeep It Moving!

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i'll be at that trainshow. If i catch you, i'll help you out.
8. ### MCD4x4Member

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I'll be there around 10-10:30.

.
9. ### 60103Pooh Bah

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Brian: how did you measure your crossover? Did you measure between the nearest rails or from one rail to the same rail on the other track? Normal measurment is to the center of the track (for radius) but parallel tracks can be measured to the rails.
I think going for elevated as well as flat on a 4x8 may be pushing it a bit, but g_e_c may be able to work it out in person.
10. ### MCD4x4Member

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The two iner rails, closest to each other are one and a quarter inches apart.

.
11. ### TriplexActive Member

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Try measuring from the inner rail on one track to the outer rail on the other track. That should be the same as the center-to-center measurement. That, therefore, will be the difference in radii for the two mains.
12. ### MCD4x4Member

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The measurement from the inside rail to the outside rail is 2". Pictured below:

Now what I'm trying to end up with it this, two loops on the bottom along with a few lay-up tracks and a ramp from the lower to the upper level in the back. I don't really know how to use this track program, and I don't want to use realtrax either but this was the closest I could come up with to give you guys an idea. There's no crossovers in the program so I just used two pieces of straight to simulate it. I'm trying to figure out what curves to use inside and out and what switches. My actual measurements are 47 1/4" x 96" Thanks for any help.

13. ### cidchaseActive Member

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That's one nice car you bought! Do you really want to run it an inch from the table edge,
on elevated tracks? It's hard to picture what you want the finished layout to represent.

It looks like you need 10-15% grade to get up from the lower level. It's quite steep and
might be tough for that car to pull itself up.
14. ### MCD4x4Member

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For the most part I'll be using the LifeLike four car subways on the upper level. I also have the Atlas NJT set with the toaster engine. Is there a switch track that can be bought so I can get more lay up tracks in the yard? It seems waste of a lot of room with just four. Also, maybe the switches from lower to upper can be moved to the rear outer curve to allow the climb on the full eight foot?
15. ### jetrockMember

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The main problem you'll encounter is that your ramp is far too short. You will need, at a bare minimum, about 2" to clear the upper level, and you have a ramp about 2 feet long. That means an average 8% grade, with no transition. If there isn't a transition (a gradually sloping curve upward) your train will simply bump into the track and stop. With a transition, your grade will be much sharper, like 15%, which is pretty much impossible to climb. Grades of 4% or so are appropriate for traction equipment like a subway, but you will *definitely* need a longer ramp--at a bare minimum, I would recommend a setup like this:
16. ### jetrockMember

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whoops, the photo didn't upload...let me try again.

Four tracks for a layout that size is plenty of yard.

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17. ### Spawn of ChaosMember

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Oh, for the crossover just use the 30 degree crossing and four turnouts.
18. ### MCD4x4Member

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That change to the ramp sounds good. Taking a measurement of the trains width, at 1 1/2" why not have a yard that I can park more trains? It's a bit of a hassle to use the finger crane to add and remove. Is there a way to add more lay-ups? Tighter switches maybe?

I have the pre-made crossover tracks for the crossovers. Is there a reason I would change it?
19. ### Russ BellinisActive Member

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The poster was not suggesting you change the crossover, he was telling you how to draw one with the cad program you were using.

I think you are maxed out on the 4 x 8 without the lower level. The ramp up will have to be outside of the outside oval. There just isn't room on a 4 x 8 with 22 inch radius to put anything outside of the oval. You will need to add 4-6 inches along the side of the 4 x 8 to make it work.

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