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Old 11-01-2011, 02:23 PM   #1
Smokinapankake
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22" vs. 24"?

So I've been planning a double decked HO layout and was debating between 22" radius and 24" radius curves. I'll be doing cookie cutter construction and so will require track boards. Probably 90% flex track. A helix to go from lower to upper level. I'll also be running mostly Athearn 6 axle locomotives with 85' passenger cars, but also some 4 axles with freight (40, 50, and 60').
Problem is, the 6 axles tend to pull the cars off the track on 22" curves unless you weigh the crap out of them. Also, the locomotives don't really like to couple/uncouple on those kinds of curves. 24" isn't really much better for coupling.

Some pros of the 22":
Easy to make curves - sectional track is readily available
To make a helix with 2-1/2" wide track boards can be cut out of a standard 4x8 sheet of plywood.
Does not use up as much space.
22" cons:
Coupling is more difficult.
6 axle locos tend to pull the cars off the track unless you weigh them down heavily. Not really an issue as I'll be running short trains and gradual grades.
Not super attractive-looks too sharp. To my eye, anyway.

Some pros of 24":
More gradual curves are more realistic looking.
Coupling/staying coupled less of an issue.
Larger locomotives run better, don't pull the cars off the track on the curves.
24" cons:
Uses up more space.
Helix building will require more material - don't know where I can find sheets of plywood larger than 4x8 to cut a circle of trackboard from.
Have to use flex track. Not an issue as I've built lots of layouts with flex before - mostly in N scale but the procedure is about the same for HO.

I've got about 21 ft by 14 ft to work with so space isn't really an issue.

Any thoughts or am I missing something?

Thanks for the help!
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Old 11-01-2011, 02:35 PM   #2
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With the space you've got I'd go 24" minimum and go as big as you can throughout the layout. It will operate more reliably with the larger curves.

You don't need to cut complete circles out of the plyboard to make a helix. I went 26" in my helix and I was able to cut 270 degrees of circle in a single swath around the board. Doing this also staggers the joints within the helix which can help in building it. Take a look in my build thread (14x16) and you can see the helix construction I used. I simply marked the centerline of the curve at 26" then made the wood strip 4" wide (24"inner, 28" outer curve) and cut with a jigsaw.

You'll get 1 big curve and a few smaller curves out of a 4x8 sheet.
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Old 11-01-2011, 06:14 PM   #3
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And don't forget that if you use MDF instead of plywood, your standard sheet size is 49" x 97" ... a precious inch larger than a sheet of ply. Might help with those 24" turn pieces.

Also, plywood mfrs also make oversized plywood sheets ... 5' x 9', for example. I've never bought an oversized sheet, so I'm not sure if this is something you could special-order through your local lumber yard. Worth checking into, though.

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Old 11-01-2011, 06:48 PM   #4
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Even with a 49" wide piece of plywood (or mdf) you're not going to be able to do full 360 cuts @24" radius. Leaving 2" outboard of the track centerline would give you 22" radius if you wanted a 4" wide roadbed.

I'd much rather buy an extra piece of plyboard and have curves that operate better.
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Old 11-01-2011, 07:00 PM   #5
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What engines do you have that throws the cars off? I had a Genesis SD70MAC that would do that when I tried to go around 18" radii, but it was fine on anything 20+. Aside from that you should give yourself the largest radii you can afford and the larger the better. I wish i could have done at least 22" on my layout I dont really like 18" but if I wanted a layout I needed to make it 18".

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Old 11-01-2011, 07:37 PM   #6
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I run mostly Athearn 6 axle stuff with the vast majority of that being SD40-2's. Body mounted couplers + body mounted couplers on the cars typically spell disaster on sharper radii curves.

I use Accu-Mate couplers and on these particular locos I use the longer shanked version which helps, but find that I have to over weigh the shorter freight cars to keep them from pulling sideways off the track on 22" and smaller radius turns. I currently have an oval with 22" radius turns and will have to do some more testing, but preliminary investigation suggests that a larger radius is preferable if I can pull it off.

I still need to secure the right of way from Mrs. Smokin before I actually lay out any cash so wish me luck in that department as well.

I'm leanin' towards the 24" radius in spite of the extra material required. If it helps things run smoothly rather than causing undue frustration then I'm all for it. This is supposed to be fun, right?
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Old 11-01-2011, 08:33 PM   #7
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I have 2 BB SD40-2s which the RTR versions are almost identical to and they can take 18" just fine with out throwing anything off the tracks. One of those SD40-2s has the plastic couplers that came with the kit and the other had a Kato in the nose and Kadee in the rear pilot. Neither are extra long. I have no problems.

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Old 11-01-2011, 09:13 PM   #8
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I must be doing something wrong. They can pull the 18" radius, but to pull cars behind them they just tend to pull the cars to the side, then the cars come off the track.
At any rate, since I have the room, I'll probably go with 24" radius.
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Old 11-01-2011, 10:00 PM   #9
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Quote:
Originally Posted by Smokinapankake View Post
Any thoughts or am I missing something?
Thanks for the help!
I had a simular problem with some of my cars when being pulled or pushed by my SD40-2s. But only my problem was only with 18" radius curves. The 22" radius track worked fine. So rather than to tear down the layout, redesign it and start again. I purchased a 40' car from Model Power. Their couplers are "truck mounted" rather than body mounted.

I replaced it's wheels with Protos, installed different couplers, installed a (car length) weight strip (slightly thicker metal). The metal that the weight strip is made of is available in 3 and 4' lengths and in different widths at Lowes. I got one that was the correct width (I brought the car with me so to check it). I cut it to the correct length with a metal cutting disk on my radial saw.

When finished, I connected the car to the engine as a "spacer" car, if you will (It now runs as good as any Athearn). The rest of the train is connected to it. Because it has a truck mounted system, it resolved the "coupler binding" problem I was having. Though the car is now a slightly bit heavier, I usually always run at least two powered engines connected together anyway, so the extra tad of weight is not an issue even for one engine, much less two.

I now can either pull or push any of the other cars with the SD40-2s, using my spacer car around the 18" radius curves without incident. The strange part about all of this is that both of the SD40s, while connected together, or when connected to either GP or RS type engines, can go around the 18" radius curves and their couplers never bind against one another. One time I even had an SW1500 connected to one of the SD40s, and they both ran well around the curves together. Go figure.

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Old 11-01-2011, 10:26 PM   #10
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Scott,

I agree with your earlier comment ... I wasn't suggest a full 360 on MDF, but rather just a bit more room for a 270 curve or the like.

I did ask a contractor friend of mine, and he said that he's been able to order oversized plywood in the past.

TJ
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