"I feel like I've been

How long do these extensions need to be? and what kind of layout benchwork do you have to connect them to, is it sturdy enough to support a long cantilever? and could the wall be used to support the far end of the extensions with some kind of removable bracket? .DaveB  

Options ahoy...

Dear ???

What it sounds like you are considering is "clip on" track-on-plank extensions.
If so, there are a number of well-proven ways home.

- Lance Mindheim has described supporting of "Track on Plank" extensions for his "East Rail" and other layouts previously. check out http://www.lancemindheim.com 

- Iain Rice has authored a number of books covering the unique challenges of designing and building small and micro layouts. This includes various forms of "clip-on" extensions. Reccomend picking up a copy of "Small Smart and Practical Trackplans".

- If there is a door available within striking distance of the "free end" of the "track on plank" extension, it may well be possible to make a "support hanger" which hangs over the open door and catches the "non layout end" of the extension.

- If you build the "shelf layout" as a full proscenium module with proper structural exoskeleton
(Qubelok + Foamcore comes to mind), then the extensions can be "fold-down" with chain-supports to the main module itself.

- "Shortliner Jack", a proliffic small-layout-builder from Scotland developed "the fiddlestick" extension, using PECO LocoLifts joined end-to-end, along with a very clever "plug in" free-end support to create a "staging extension". See details on RMWeb 
http://www.rmweb.co.uk/community/index.php?/topic/44026-the-fiddlestick-switch-job
/> (Make sure to follow all the way thru BOTH pages, detail pics of the sleeved extension support are on Page2!)

Hope this helps...

Happy Modelling,
Aim to Improve,
Prof Klyzlr

@Dave - Doesn't need to

@Dave - Doesn't need to be  too long, 1-1.5 feet would be enough.  A canteliver would be my ideal solution, the issue was that I was at a bit of a loss on how to: 1. construct my benchwork sturdily enough to support the cantilever section while still being low-profile enough to call a "shelf", and 2. have the cantilever section be (relatively) easy to remove while also being sturdy enough to support a train and not shift around causing derailments.  I do have the extra wall space for a removable bracket at the end, I'd just like to avoid mounting anything to the walls that I don't need to, so I'm considering all other options first. 

@Prof - Thanks for the reading suggestions, I've been meaning to get a library started, but there's so much out there it can be a bit intimidating. Shortliner Jack's solution is actually similar to something I was considering, good to see that some of my ideas are on the right track.  It looks like his "fiddlestick" is supported out close to the end, but a shorter cassette and a longer "stick" under the layout might reduce the need for that. Also very cool using the headphone jack as a power connector, might think about implementing something like that

Also I thought I had set up a signature, and just double checked, but in case nothing shows up again, the name's Brad.  

I am facing a similar issue

I am facing a similar issue with an extension for a switch lead on two free-mo modules. This is the best design that I have found so far.

http://dmirhillcitysub.blogspot.com/2010/12/removable-staging-installed.html

Best of luck!

1.0 to 1.5 feet

is not going to be very heavy so should be possible to support it without using the wall. If the layout benchwork is designed strong enough a pair of dowels could be inserted into holes drilled thru the end crossmenber and the next crossmember then the removable section could be slid onto the dowels thru holes drilled in it. If drilling the holes in the benchwork is not possible the same method could use brackets hanging below the benchwork with slats that slide into them to support the extensions. However if there's more length available a longer extension supported by a wall or door frame bracket on the far end would give a longer lead for more switching flexibility along with better mechanical leverage.......DaveB

Beer Line idea

Model Railroader's series on the Beer line some years ago used the dowel idea as a short switching lead extension. Their idea was to attach the dowels on the extension and then just slide them into the adjoining end when needed. At one time I did the same thing only I used a hefty C-clamp to hold it in place. The extension end had a couple of rail joiners that I slid in place and a piece of soft foam at the other so nothing would run off the end into the great pit known as the floor. Used a couple of short pieces of masonite on the sides also. Ugly, but it worked great.

Jack

Lance Mindheim suggests a

Lance Mindheim suggests a clamp-on extension/fiddlestick/staging board using large C clamps. If you have followed The Profs post you will see how my fiddlestick worked. Another clamp-on device is one of these  http://www.ebay.co.uk/itm/Stanley-Metal-Spring-Clamp-50mm-Single-983080-/331704783743?hash=item4d3b25537f:g:wDQAAOSwT5tWQiBv

They come in two sizes 25mm and 50mm (approx 1" and 2") and should hold a foot/18"-long extension board - especially if two clamps are used to join two vertical end frames - or bolts screwing from underneath the extension board into Tee-nuts in the end of the board - use two and feed power to the end board through them. Be advised the springs in those Stanley lamps are STRONG - DO NOT GET SKIN BETWEEN THEM

EDIT don't forget broom handles - available cheaply from ironmongers are effectively large (and strong)  dowels, and if fed through two crosspieces with holes under the main board - and fitted into corresponding holes in the cross-pieces under the extension board - will act as a strong support

How did you power it

I have two extensions similar to the Duluth line but need to know how to power those sections.  Any assistance would be appreciated.  Chris