An HO inch is 1/87"
OldTimer   

Neither my dogs nor cats pay any attention to my layout.  Engines are mostly equipped with Digitrax quiet-running ("SuperSonic") decoders.
OldTimer

Kadee 20 series couplers come with an adapter that will let you replace newer TYCO horn-hook truck mounted couplers (plastic trucks) with knuckle couplers compatible with your Bachmann engine.

Older Tyco and Mantua cars pose a different problem.  If your cars have truck mounted couplers, you'll have to do some surgery.  The coupler box is riveted together and the truck attaches to the car with a machine screw passed through a sheet metal bolster.  The best bet is probably to remove the truck mounted box and body-mount Kadee or EZ-mate couplers using a draft gear box.  That will require drilling and tapping for a 2-56 screw.

If your Mantua cars are so old that they have the old hook and loop couplers, you'll have to remove the old coupler (one screw as I recall), and modify the underframe to accept a draft gear box. 

A Kadee coupler height gauge is your best friend for these types of operations.  Good luck.
Kadee's web site is here:  http://www.kadee.com/htmbord/HOplc.htm
OldTimer

All the Genesis F-units take a Kadee #36 on the front of the A-unit and a #38 on the back of the A-unit and both ends of the B-unit.
OldTimer

One of the best things you can do for a small, island style layout is to put some sort of view-block down the center so you can't see the whole layout at once.  The view-block can be part of the scenery, hills for example, or it can be something like a sheet of masonite with backdrop  painted on it.  Extruded foam will work, too.   Building your benchwork high (mid-chest) also helps increase the apparent size.
OldTimer 

Lots of curved turnouts out there...there is no reason not to "mix and match" to get what you want. 
OldTimer

You can try looking at the web sites for the various decoder manufacturers.  You can find a list of manufacturers here:

http://www.tttrains.com/dcc/dcc_man.htm

And there's a list of recommended decoders by loco type here:

http://www.gatewaynmra.org/dcc/dccdecoders.htm#locomotives

Hope this helps. 
OldTimer

Your plan has a couple of serious shortcomings.  First, you have no run-around track.  Look at the Morgan Valley plan and see how the run-around track is used to help switch facing point spurs.  Second, I fail to see the purpose of the interior oval.  Once you've gotten your train on it, there is no way out, short of backing the train through an ess curve...unless you backed in to begin with.  And if you did back in, you need to be sure that any cars for the sppur off the inner oval are in front of the locomotive. 

On the plus side, the sidings in the upper corners could easily be extended to stageing tracks which could provide traffic for your railroad.

This is just my opinion, and I speak only for myself, but it seems to me that the plan is much more important than the track that it's made out of.   The Morgan Valley is a well-designed switching oval that can be operated with a purpose--a sure cure for lack of interest and bordom.   Hope this helps.
OldTimer

Powdered graphite makes an excellent lubricant for couplers.  Your local hardware store should carry it...comes in a little tube with a nozzle at one end.  While you're at it, examine the inside of the coupler box and around the box opening for flash (thin little ridges of plastic).  Use the edge of an X-acto blade to scrape away anything you find.  And....make sure you're not putting the lid on upside down.  Hope this helps.
OldTimer

Did you buy this locomotive new?  The ability to run on DC is controled by a bit in CV-29 and it's possible that a previous owner has disabled DC operation.  If you have a friend who has a DCC system, have him reset your decoder by writing the value 8 to CV-8.  Or, your LHS may be able to do that for you.  Hope this helps.
OldTimer

Dyed sawdust used to be the inexpensive stand-by.  You could get it in (bright) green for grass and a sort of reddish-brown for dirt.  Life Like sold it by the bag.  I looked through the scenery section of the Walthers catalog and found sawdust and real dirt for sale by Highball Products, but it doesn't seem inexpensive.  If you have a table saw, you can make little boards out of big ones, thereby producing your own sawdust.     You can use local dirt, too, but you should strain and sterilize it. 
OldTimer

The orange wire connects to pin 1 on the 8-pin plug.  The socket should be marked with a dab of paint, a little arrow, or something, to show you where to insert pin 1.  If you put the plug in backwards, no harm will be done, but the lights will not work correctly.  If that happens, simply unplug the decoder, reverse the plug, and reinsert it.   Hope this helps.
OldTimer

I don't know if Union Pacific ever had a 2-6-2 numbered 1836, but I can tell you that there is a UP locomotive wearing that number today--a GE B40-8.  Here's a pic of her.

http://www.rrpicturearchives.net/showPicture.aspx?id=532749

OldTimer

Athearn streamline cars ought to run on 18"R curves.  They're "shorties" (about 70') and have truck mounted couplers.  They're on e-Bay all the time.  They're "shake the box" kits and very easy to light.  The PRR cars are tuscan red; all the others are silver with a contrasting stripe.
OldTimer

If you want to make a day trip of it, head for Denver, the home of Caboose Hobbies, an excellent hobby shop.  They also have a web site at

www.caboosehobbies.com

See the bottom of their home page for store hours, phone numbers, e-mail, etc.
OldTimer