Lionel made a submarine that really floated and submerged and a rail car to carry it.
I found two toy submarines that may work but I have never tried them. I did make mounts for the submarines on two rail cars and have a new different car from most of mine.
Charlie
Atomic Generator Car
This car started life as a Kusan KMT (later K-Line) search light car Number USA 401098 without the search light and operator. I added a mini Christmas tree flasher light bulb and socket, light for the new operator and control panel and a red plastic "thing a ma jig" red flashing light cover.
The car now enjoys life as an Atomic Generator Car. Every train layout needs a portable power source for emergencies.
Charlie
A Christmas car......a red Lionel flat with a little wood decking.......and, a ceramic manger set I picked up on Amazon....
Peter
Peter
I love the manger car. My wife collects mangers and I hope to borrow one and make a manger car. Thanks for the inspiration. I would add it to my secular reindeer and Santa Christmas train.
Charlie
I modified a Marx work caboose by adding a flood light to allow night operation to be performed more safely. I added a homemade light pick-up to power the light.
Charlie,
Nice, clean and professional job.
Tom
I made a ballast hauling gondola car load and placed a small back hoe machine on top to add to my track maintenance train. The ballast load was made from a piece of Styrofoam (to keep it light weight) with ballast glued on with Elmer's glue.
Part of Maintenance Train
Keep your homemade cars coming in.
Charlie
"Prewar cast iron" loco made from an old Marx 999 with styrene and copper parts.
"Prewar" freight cars made from various parts...
Caboose is a real prewar Flyer item. Gondola and boxcar graphics were drawn on the computer and printed on photo paper. Gondola body is cardstock with the photo paper glued to it.
Beaver-tail observation made from AF prewar coach.
Had to build an Army Flat to match Menards Air Force missile car
Darned like button never works on this thread; which is a shame because everyone deserves two.Bob, the rocket car looks great!
My latest...
Mitch
Nothing as awesome as what you guys have done; I guess I'll need some stock to run on 3 rail track to go behind my new loco.
I've had an old Athearn boxcar sitting around for years, so I slapped on a couple of Atlas/Roco trucks and now at least I have a full-size O scale car with big flanges:
Still have to add details, but it's a start.
Disclaimer: I am not responsible for the crappy glue job on those grab irons; this car came to me this way, I swear! 
Mark in Oregon
Cab-Forward Engine
Years ago I purchased a Lionel 2025 2-6-4 steam locomotive that came with a homemade enclosed cab and white wall painted wheels. I left both intact. The Lionel 2025 and 2035 are my favorite engines to run on my layout.
My closed cab Lionel 2025 with white walls
Recently I was reviewing a March 1999 Classic Toy Trains magazine and read a product review of a 3rd Rail Brass O gauge Southern Pacific Cab-forward 4-8-8-2 steam locomotive. I was not familiar with cab-forward engines. The article pointed out cab-forward steam locomotives were made to solve a life and death problem Southern Pacific had due to asphyxiation of crew when operating in long tunnels and snows sheds in the Sierra Mountains in the early 1900s. Baldwin developed the cab-forward style locomotive and over 195 engines were made from 1920 and used into the 1950s.
Real Cab-Forward steam locomotive
Since I already, more or less, had a enclosed cabin steam locomotive, the Lionel 2025 mentioned above, all I would have to do to make a cab forward locomotive is find oil tender (an oil tender must be used as there is no way to get coal from a coal tender to the fire box with the cab in the front of the train). Next was to make a hookup connector from the front of my 2025 steamer to the front of the oil tender at the tender slot coupling. I know a Lionel 2025 2-6-4 is not a 4-8-8-2 which would have no chance of running on my O27 track !
I found a metal case from a junk DVD player as a source of sheet metal for the connector. This metal sheet is thicker than tin can, strong enough for the connector and can be cut easily with a pair of tin snips.
Sketch of connector
Bottom view
Top view with tabs going on top of front wheel axle
View of connector in action, it turns well and navigates my Marx 1590 switches
Lionel 2025 as Cap-Forward engine pulling oil tender
Close up of an oil tender I found I already had
Connector is strong enough to pull other cars after the oil tender
The connector was quick and easy to make and works well. It is a little weird to see a steam locomotive tooling around the layout backwards ! Someday I may add a headlight and markers lights to the front of cab-foward loco. (see headlight on first picture of real cab-farward Loco)
Charlie
I attached a coupler to the front of a General's pilot truck after figuring out with a body mount, the front overhang pulled cars right off the rails in curves, or if heavier, the cars dragged the drivers off. I imagine fast angle wheels wouldn't do as well; the flat tread and deep flanges of early and loco wheels do a great job keeping the pilot truck on the rails, though you'd likely think "not". I think it's that the center of gravity and attachment point is so low; nearly at pilot truck axle height.
I expect making a "home-bilt" Vanderbilt tender would be pretty easy for you too Charlie.. hint, hint, 
Here is a homemade General Motors EMD Train Generator hauling car. I figured this electric motor would be about the scale size of the diesel driven generators used on F3 EMD diesel locos. I may be wrong but it works on my layout! It fits well on a depressed flat car.
Charlie
Here is a project I just completed. I took an inexpensive Lionel woodsided reefer and transformed it into a representation of a Mathers outside braced boxcar...
The donor car...
and the prototype I am attempting to relatively mimic...
Here are some shots with the first color sprayed...
and then the second color...
and now the finished car with Protocraft decals applied and some weathering...
Mark
Great job on making the Lionel woodsided reefer into an outside braced boxcar. I was unaware of that class of car and its rarity in being modeled.
Not having or not finding or not being made are some of the best motivations for homemaking a car allowing one to have the fun and experience at doing for yourself.
Charlie
Wow! This is probably the coolest thread of seen here! I'm 28 and love building stuff. In a hobby that is full of plug and play items it's awesome to see people still building things!
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