Hello...
Finally got some ramps built:
http://acer-access.com/~placebo@acer.../ramppic0.html
My primary purpose was too create a set of cheap and safe ramps which most anyone could create with a simple set of tools and simple materials:
Materials:
Standard construction lumber and wood construction grade screws. I built my ramps from recycled lumber from a 1940-50s farm building I tore down. It has a weathered look on the outside, but is solid inside (and actually is probably stronger than modern lumber as its from older growth forest). I plan to coat the ramp sections with some wood preservative I had left over from building a garage (probably not a good idea to put any preservative on the outdoor plywood cap since this may cause the plywood's glue to fail).
If I were to buy new lumber I'd probably go with treated green lumber, typically used for decks, as its rot resistant and I feel it holds fasteners much better than plain new untreated construction lumber which I find very dry. Green treat will cost more, but I feel its worth it.
The plywood I used consists of scraps left over from the construction of a garage. Although the plans call for 36" long sections of plywood I used smaller sections of scrap to cap the ramps as none of my scraps were that long. If I had to purchase new plywood I would use 1/2" (9/16") outdoor grade. I'd stay away from that wafer board made from wood chips as if it gets wet it effectively turns into "wet cardboard" over time). I also cut my sections of plywood slightly less than 36" (1/8" less) so that the plywood cap would not interfere with assembling the sections.
I had most of the screws on hand, but did buy a box of 3 inch screws for $8.00 + tax (my total cost as everything else was essentially free). I used construction grade green colored screws and some silver colored galvanized screws for securing the 2 X 6's together; and and shorter screws for the plywood.
Tools:
Saw (you can use a hand saw, but I would suggest at least a circular saw; however, a chop saw will be faster). The angled sections will probably be need to be cut with a circular saw.
Electric drill with a screw bit insert will save a lot of time! Pre-drilling holes should allow the screw head to countersink themselves into the wood as the downward torque of the screw will compress the wood around the head (using too light of screws may cause the screws heads to break off).
Square and a pencil for marking drill points. I liked to stagger the screws points slightly so the screws don't run into each other (such as on the inner sections) or cause cracking (i.e., too close to the edge of a timber).
Sander (belt sander, palm) may or may not be needed. If you find that some of the tongues are a little tight when sliding the section together simply sand them of both sides. A sander can also be used to sand off slight differences in the height of 2 X 6's before applying the plywood (lumber width typically varies from board to board).
Notes:
These finished ramps are around 6" high and 15 foot long, and provide enough access for me to slide completely under the entire length of the car using a wheeled mechanic's board (with several inches above my head). My 2005 Matrix XR, with factory side skirts below the doors, cleared the ramps with 4" above the car's "hang-up" point (i.e., when the front wheels are on the ramp, the bottom of the car in front of the rear wheels may hit the top of the ramp as you drive on if the ramp grade is incorrect - I crudely calculated this on graph paper at 3" using the planned ramp size, the wheel base, and tire size).
These plans can be easily modified to make higher ramps, such as using 2 X 8's or 2 X 10's instead (if you make the ramps higher the ramp section should be longer so as make the grade less steep so the vehicle does to scrape the ramp tops when driving on). The sections can also be made longer; however, I tried to keep each section to a maximum of 4 feet for storage purposes and a weight of 50-60 pounds. To facilitate the easy assembly of the sections I drew reference lines on the garage floor using a carpenter's chaulk line. I also cut some spacers of approximately 49" each, which are removed after assembly (overall width of ramp is approximately 72"). I also screwed a 2 X 6 stop at the front of the ramps so you cannot drive off the end and cut 4 similar loose stops for placing under the wheels so it cannot roll (though I do not think there is much chance of that since its level and the emergency brake is set).