So we sat down and looked at some commercially available ramps, and got some ideas for size. Then we sketched some construction ideas and came up with a plan.
We went to the local home supply store and picked up a sheet of 3/8" plywood, a 2X4X10 and a box of 2" screws. As we don't have a truck, and the ramp was going to be 2 feet wide, we had them cut the plywood sheet lengthwise. This gave us two sheets of 2'x8' plywood. This is more than enough to make two ramps with scraps left over. Also, I ripped the 2x4 in half (for the support cross beams) on my table saw. You can do the same, or you can use 2X4. Our supplies were about $17 (a real bargain, eh?).
The project shouldn't take more than 4 to 5 hours to complete. I used my table saw, jig saw, and drill. You can use a circular saw as well, just remember to use a guide and cut really straight.
Please wear a helmet when using the ramp. Also, be aware of your ability or the abilities of your child. This ramp was designed for a ten yr old for recreational use. If you are bigger or want to hit it harder I recommend using thicker plywood for your vertical supports.
So what do you need?
3/8" plywood sheet
Table or Circular Saw
Drill and bits for pilot holes and driving screws..
So, here is the result. Enjoy.
Does it work? Sure check out the video.
Step 1: Cross Beam Supports
These will support the ramp deck, and lock the vertical supports together.
I started with a 2X4X10 that I ripped in half (lengthwise) on my table saw. This gave me a cross beam that was roughly 1 1/2 x 1 1/2. You can do the same, or use the full 2X4.
Cut them to a length of 24".
In addition, you will need one more support beam that is 23" long. This will go on the back bottom edge.
Step 2: Vertical Supports
Start by cutting your plywood into rectangles that are 24" x 12". Take three of these rectangles and tack them together temporarily. You can use screws or nails, as long as they are kept together and all the sides are square. If they are not perfectly square, use your table saw or circular saw to cut them so they are square.
Now sketch a curve on one side. This will be the profile of your ramp. Feel free to make it straighter or more curved than mine. We wanted a little 'kick' so we could get some 'air'. Our curve was made with the TLAR (That Looks About Right) method.
Using your jig saw, cut the curve from one end to the other. Now you should have good shape for your ramp.
Now you need to cut the slots for the cross beam supports. Find three points on the curve, one near the top, one near the middle, and one towards the bottom. Draw an outline of the shape of your cross beam (either 2x4 or 1 1/2 X 1 1/2) at those three points.
Start cutting the support slots with your jigsaw. Make 7 or 8 parallel cuts for each slot. Then using a screw driver or chisel, break out the pieces. Next use your jigsaw to clean up the bottom so your opening is clean and square.
Test each slot with your cross beams to make sure they fit snug and are flush with the curve.
When you are satisfied with the fit, separate the supports, and pick one to be the middle support.
Cut the bottom corner of the middle support to allow the bottom cross beam support to pass through it. See the diagram below.
Step 3: Cut the Deck
The deck should be 24 inches wide, and approximately 26 inches long. So cut this out of your plywood sheet using your table saw or circular saw.
The next issue to overcome is the curve of the deck. Honestly, I figured that 3/8" plywood would easily bend to the curve on its own. I was wrong. However, before I started, my wife advised me that I should score the back of the deck to allow it to flex. Yeah, she was right.
So here's how to do it. Set your table saw, or circular saw to a depth of 1/8" and cut lengthwise channels approximately 1" apart on the back of the deck.
Step 4: Base Plate
This is a portable ramp, and if you went to use it without that extended base, then there is a good possibility that the ramp would tip when you used it. Not only could it be dangerous, you would lose momentum and not get the air or distance you were expecting.
Cut the base plate to be 24 inches wide, and at least 34 inches long. That should allow it to extend at least 10 inches beyond the end of the ramp.
See the picture below for detail.
Step 5: Assemble the Frame
Start with a clean level surface. (Or as clean and level as you can get it.)
Start by screwing one of the outside vertical supports into the bottom rear cross beam. Make sure the supports are lined up square. I used at least two screws to prevent the cross beam from rotating. Do the same for the other vertical support.
Next, attach the middle vertical support to the bottom cross beam. Carefully drill a pilot hole from the cross beam into the vertical support, and the drive in a screw.
Now, you can start the the horizontal cross beams that will support the deck.
Pick a cross beam and insert it into the slot. Drill a pilot hole from the cross beam into the vertical support at and drive a screw into it. Repeat this all the way across and for the two remaining cross beams.
When you are done, you should have a pretty sturdy skeleton for you ramp.
Step 6: Attach the Ramp Deck and Base
Get your ramp deck and align it on the frame. The back side of the deck should have the horizontal scores that will allow it to flex.
Push against it and drill a pilot hole through the deck into one of the cross members, either the left or right side so you can see where the cross beam is located.. Then drive a screw to hold it. Make sure your screw heads are countersunk so they don't tear up any bicycle tires. Repeat this on the other side of the deck.
Attach the deck to the other cross beams in the same way. You might want to snap a chalk line from side to side to ensure you hit the cross beam, and to make your screw line look straight.
Now you can attach the deck to the vertical supports the same way.
Turn the ramp over and align the base plate to the ramp. Attach to vertical supports and rear cross beam by drilling pilot holes and driving screws.