Thanks for your interest in my Dual-Width Extension Wing
for the Ryobi BT310x series table saw.  This text file
contains instructions and commentary that may be useful
in getting your own version of it built.

First, some terminology:

1. The Dual-Width Extension Wing will be known herein as
the "DWEW."

2. When the short leg of the "L" is horizontal, I will
call that the "narrow position."

3. When the long leg of the "L" is horizontal, I will
call that the "wide position."

Next, some design parameters:

1. On my personal BT3100, I had the rails set so that
the rip fence scale was zeroed to the blade.  I liked
being able to use the scale, so this preference was the
starting point for working out the dimensions of the
DWEW.

2. In the narrow position, I wanted the footprint of the
saw to be no larger than the way it came from the
factory, and I wanted no gaps in the top surface.

3. In the wide position, I wanted a rip capacity of at
least 30", without having to move the rails.  This
matches the capacity of many contractor and cabinet saw
fence systems.

4. I wanted to be able to switch from narrow to wide, or
back, as quickly and as easily as possible, without
taking anything off or on the saw.

The design I ended up with satisfied all these design
parameters in every respect.  Especially the fourth: I
was able to switch the saw from one configuration to the
other in less than one minute, without using any tools of
any kind.

You can refer to the pictures in this thread ...

https://www.sawdustzone.org/forum/discussions/bt3x00-related-discussions/30491-dual-width-extension-wing#post842101

... to get a better idea of how I built the prototype.

Now, some tips, caveats, and general discussion that may
or not prove useful:

My BT was fitted with an 8.25" wide, shop-built fixed
table between the saw's main table (the one in which the
throat plate is located) and the DWEW.  The short wing of
the DWEW was then sized to put the right end of the DWEW
approximately even with the right end of the stock rails.

The long leg of the "L" was sized to provide the desired
30" minimum rip capacity with the DWEW in the wide
position.  This required a pair of extension rails
sections 11" long.  If desired, the rip capacity can be
further increased simply by lengthening the long leg of
the "L" (the only limitation is that it won't hit the
floor).  Obviously, the short extension rails would have
to be lengthened by the same amount.

The 8.25" width of the fixed table is about the minimum
necessary to keep the short wing clear of the power
switch jumper cord when the DWEW is rolled up into the
wide position.  No matter what other changes you might
make, the entire DWEW cannot be less than about 8" from
the saw's main table; otherwise, you're going to have an
interference problem at this point.

This fixed table also provided the means to keep the DWEW
from rotating when in the short position, when the DWEW
is hanging off only two T-nuts (one at the front rail,
one at the rear).  I used a simple lapped joint between
the fixed table and the DWEW, which in practice proved
less than satisfactory.  You can see what this looked
like in the thread photos; I'm not providing any drawings
for it because it's not really a good solution.  On the
never-built final version, I planned to use a
tongue-and-groove arrangement in which a strip of UHMW
plastic mounted to the DWEW would engage a section of
miter track on the edge of the fixed table insert.

In the wide position, the long leg of the DWEW hangs off
four T-nuts (two front, two rear), which holds it in the
correct position and keeps it from rotating.

There are really only three critical dimensions for the
entire assembly.  Two of them are the same: the holes at
the corner of the "L", on which the DWEW pivots, must be
exactly 2-5/16" down from the top surfaces of BOTH legs
of the "L".  If they aren't, one or both legs won't flush
out properly with the top of the saw.  The third critical
dimension is the 1'-10 7/16" overall width.  This is
sized to fit snugly but not tightly between the BT's
front and rear rails.  YOU SHOULD VERIFY THAT THESE
DIMENSIONS WILL BE CORRECT FOR YOUR OWN PARTICULAR SAW.

The continuous notch along the top edge of both legs on
the rear-rail side of the DWEW is to clear the locking
mechanism on the back end of the rip fence.  The 3/16" x
1-3/16" dimensions of this notch are not really critical
except in the sense that they can't be any SMALLER than
these values.

The bolts that hold the rail extensions to the DWEW can
be located anywhere along their length; all that matters
is that they are exactly in line with the holes on which
the DWEW hangs.  You might want to make the holes for the
extension rails slightly oversize, so that you can tweak
the position of the extensions when the DWEW is rolled up
into the wide position.  (Note: do NOT make the four
pivot/hanging holes oversize!  They need to be precise,
for correct operation.)  My extension rail sections
simply butted up against the stock rail ends, with no
kind of interlocking alignment mechanism.  Sometimes I'd
feel a slight bump when I slid the rip fence past the
butt joint, but it wasn't a problem.

If you plan to cover the tops or sides of the wings with
plastic laminate, don't forget to adjust these critical
dimensions as necessary to allow for the laminate's
thickness.

I built the framework mostly out of 3/4" MDF (plus a
little 1/2" Baltic birch plywood), skinned it with 1/2"
MDF, and left it unfinished.  You can use whatever
materials you wish, and finish it (or not) however you
like.  I suggest materials that are dimensionally stable,
like those I used, although you could use some nice,
straight-grained hardwood for the framework.

I put a router mount in the short leg of the "L" since I
normally left the DWEW in the narrow position and wanted
the router available as much as possible.  If you prefer,
the router could be in the long leg; or you can have no
router at all.  It's your choice.

I hung the DWEW on the rails using plastic knobs with 1"
long, 1/4-20 studs into T-nuts that fit in the tracks on
the rails.  A 1" stud through the 3/4" sides left just
the right amount of threads left to engage the T-nut.
These stud-type knobs were quick and easy to operate, but
you could also use hex bolts and turn them with a wrench
if you don't plan on switching configurations often.
Adjust the bolt diameter and thread pitch to match the
T-nuts you use ... they don't have to be 1/4-20s.

Depending on how you build it, and whether you
incorporate a router, your DWEW could get pretty heavy.
Depending on how much it weighs, you might want to think
about putting some legs or knee braces under the ends of
your stock rails.  I personally don't think this is
necessary if you make it roughly the same size as mine
and keep the router mount simple (i.e., no heavy lift).
But it's your saw and, again, it's your choice.

I will STRONGLY suggest you start by making a simple "L"
shaped mock-up or template out of a piece of 3/4" plywood
or MDF, hanging it on your saw with a single T-nut, and
rolling it into both positions to make sure you have the
pivot hole in the right place and all the other geometry
correct.  This is what I did when I was working out the
dimensions of the design, and it helped me head off a
couple problems (like the interference at the power cord)
that I might otherwise have missed.  If the flat mock-up
template doesn't fit correctly, scrap it and make another
one.  Keep doing this until you get it right and you
understand the dimensional relationships of the DWEW in
both configurations.  This will not be a difficult
project to build in terms of complexity, but unlike most
woodworking projects it has some interrelated dimensions
in all three planes that must be pretty much spot-on in
order for it to work as intended.

Good luck, and have fun building your own DWEW!  If you
have any questions, I'll be glad to answer them as best I
can.  Just shoot me a private message on the forum; while
I am no longer active there, I will be notified that your
PM is waiting.

-------
Best,
LarryG