Why not a layout that can slide under the bed so all the monsters that reside there can play with them also. Humor aside it might be worth considering.
Regarding easements: They actually don't add that much to the net diameter of a 180 degree turn, but they do add considerably to its length, that is, it takes up more of the otherwise straight sections on either end. Try adding one 9-3/4" or 11" radius section to each end of the 180 degree turns and see if that solves the problem and still fits on the dresser.
There's so much good advice here and bad advice. Newbies helping newbies to make the same mistake. Did I really say that? I did. Rule of thumbs some of us experienced model railroaders use. Couplers body mounted versus truck mounted. A truck mounted car coupled to a body mounted car is trouble. Especially on tight radius curves Ie., 8", 9", and 10". I understand space constraints but you might want to look for another option for the base of your train layout. Wide radius curves are the best curves. Point made above. Easements work nicely and are used by most of us. It does widen the overall curve so you will need more space for your layout. Story time: Oh no he isn't doing that again, is he? Yep, I sure am. I once worked in a hobby shop and the most asked question (I actually tracked it) "What is the tightest radius I can buy"? My thoughts but never verbally expressed. Wrap the flexible track around your little finger (what the heck). Instead I offered up 0-27 in the Lionel Train Department. Followed by if you want a Toy Train that's the best place to start. I did say that. Made my boss all kind's of happy. That's what he preferred we sell. Not that I was crazy about doing that but oh well! I went to visit a HO Model Railroad Club in Apple Valley, CA. Note I didn't say which one as there are several. They were trying to install rerailers at the beginning and end of their tight 18" radius curves. First note: 18" radius is the N Scale (approximate) equivalent to 9 3/4" radius curves. They were running an old Atheran FP45 (w/body mounted couplers) behind an Athearn baggage car (w/truck mounted couplers) in behind the motor (locomotive). At the club, I took the time to point out the problem. I don't think anyone in the club actually caught on to what I was sharing with them. "Everything normal" and I think you can finish that. Well, honestly the first time I saw it, it took me forever to catch on. What with my first HO layout 18" radius curves, six axle motors (diesels) pulling truck mounted couplers. It was an article in one of the Model Railroad Wig Wags of the time that got me to thinking. Tangents, angles, and the fact the body mounted couplers will pull the truck mounted coupler-ed cars behind them off the track. Here's the thing. Most Newbies come here wanting affirmation that what they are doing is right or okay. Some of us know better then to leave you hanging there and will throw our two cents into the discussion. Others, usually other newbies, will give you that affirmation. We also know this is a mission of self discovery. So it will be up to you to solve your own problem as best you can. Take what you want from here and leave the rest behind. You will. We've all done that. See signature.
I just looked at mine and I don't think so. The trucks have a lot of details that stick out plus there are step ladders on either side front & back, so their rotation is fairly limited. Even 9¾" probably has them right on the limit.
Humm, no on liked my last post. Typical !! It was that way in the hobby shop. Most would be newbies would look at me, a blank look on their face. Not understanding the Help, the were getting. You'll figure it out. When is the question???
It will run and drag cars around those tight curves but no well. You can expect to pull the truck mounted cars behind it off the track. Like I said you'll figure it out.
Most locomotives are designed to run on a minimum 9.75 radius. Does not mean they run as well on it but they will run. Some Japanese and European Types are designed to run on a tighter radius because of less modeling space and tighter curves and turnouts. A long time ago I did the research on what would run on a tighter radius because I was intending to build a compact layout. I put that result up on Trainboard listing the locomotives tested at the time and it has been 6 or 7 years ago at least. I found that the 44 tonner would take 6 inch and the 70 tonner would take 7 inch. I found that most all small drivered steam of not more than 3 axles would do fine. Besides the mentioned 44 and 70 tonners I also found that the SW-9,1200, and 1500 would run on the 8.5 and surprisingly the RS-1. The Shays also can run on it. Today I have a 14 foot by 3 foot layout with 8.5 inch mainline curves and 6 inch and 7 inch curves on the sidings. My turnouts are Kato small radius type which have 6 inch radius. My rolling stock is all limited to a max of 40 foot length. I can easily drag a 30 to 40 foot train around the layout. A small dresser top layout is just fine with small locos and short cars and 8.5 radius. Trying to run a big 4-8-4 Northern or large diesel with long cars is a recipe for disaster.
