My son recently had a school assignment to invent something. It could be a new idea, or an improvement on an existing idea.
After talking over the project guidelines with him and tossing some ideas back and forth, he decided he would like to make a Plinko board to be used to decide household chores for him and his sisters.
Step 1: Materials
Foam core - two 20"x30" 1/8" thick sheets of foam core
Bamboo Skewers - 30 9" skewers
Step 2: Planning and Layout
Graph paper is your friend.
Making the collection bins at the bottom 5 inches high and three inches wide, except for the center bin allowed 7 bins across the bottom. The center bin ends up being only two inches wide instead of three, so it gets the honor of having the biggest reward, a night off from having to do a chore.
Spacing the rows of pegs by an inch and a half, allowed for 15 rows of pegs. The columns lined up directly above the bin walls, and then half way between the bin walls. This causes the pegs to be denser towards the middle of the board which tends to direct the pucks out towards the outer bins. While the center bin is harder to land a puck in, it is very possible.
Once you figure out your spacing it is time to transfer the plan to the first sheet of foam core. A long straight edge makes this job very easy. If you don't have a T square you can do this with a regular rule, just be careful to keep your column and rows in line.
Step 3: Reinforcing the Board
The foam core is a bit thin and not very structurally strong so adding a layer of cardboard helped to reinforce the board, and give a stronger base for the pegs to be attached to.
A liberal application of glue spread evenly over the back of the foam core, and the foam core is placed on the cardboard. A few good sized books will make sure the foam core and cardboard are pressed together while the glue dries.
Once the glue dries trim away any excess cardboard.
Step 4: Making the Pegs
While he was waiting for the glue to dry he got to work making the pegs for the board.
Cutting the bamboo skewers into 2" pegs, 30 skewers will give you 120 pegs.
We tried several different ways to cut the skewers:
Fail #1 - diagonal cutter pliers - The diagonal cutter will snip the skewer no problem but it mashes the point of the cut flat and causes the bamboo to flair out and fray.
Fail #2(sort of) - razor knife - by rolling the skewer back and forth under the razor knife blade you can get a clean cut but it takes a long time to get through each cut.
Success - a coping saw with a fine tooth blade - the fine tooth blade gives a clean cut through the bamboo skewer, and you are able to cut multiple skewers at once. He found that he was able to control 5 skewers at once without having difficulty.
Step 5: Pilot Holes
Initially the plan was to use an uncut skewer to poke the pilot holes through the foam core and cardboard. That idea was quickly discarded because after the first hole was poked through the board the point of the skewer started to roll over and the skewer quickly became too dull to push it through without causing damage to the board.
Grabbing a few pieces of scrap wood to protect the table and the drill with an appropriate sized bit, He was soon making pilot holes quick and easy.
Step 6: Placing the Pegs
Some teamwork made placing all the pegs a quick job. Dad manning the glue bottle and Son placing the pegs we made quick work of the whole board.
Now is the time to check from different angles to make sure the pegs are straight. He also added an extra dollop of glue around the base of each peg to reinforce it.
Take another break while the glue dries.
Step 7: Adding the Sides and Dividers
Using the second sheet of foam core it was time to make the sides and dividers.
Cutting three 2" vertical strips will make the two sides and the third strip trimmed to a 20" length will make the bottom border of the board.
Another 2" vertical strip cut into 5" lengths will make the 6 dividers at the bottom of the board where the puck ends up in.
A 1" strip cut to 20" length will make the top trim for the dividers. You will need to cut a notch in each of the divider tops so that the trim strip sits flat.
Step 8: Making the Pucks
The Pucks need to be smaller that the space between the pegs in order to get to the bottom. Since our pucks were hand cut they vary slightly in diameter. The smallest has a diameter of 1.25 inches. The largest is 1.375 inches. The closest pegs are 1.625 inches apart.
After testing several different materials as pucks for the board he found that 2 discs of foam core glued together worked best.
Quarters - failed - to heavy, didn't bounce between pegs well
Water bottle cap - failed - kept bouncing out of the board
Milk bottle cap - failed - kept bouncing up onto its side
Gatorade bottle cap - failed - too large, got stuck between the pegs
Single layer foam core - failed - not heavy enough, would not always slide all the way to the bottom.
Double layer foam core - success - stayed flat on the board and made it to the bottom of the board.
Step 9: Making the Angled Support
In order for the board to work properly it needs to be at an angle.
If the board is straight up and down the puck will keep bouncing out.
If the board is leaned too far back the puck will not have enough momentum to slide to the bottom of the board.
A 30 degree angle seems to be a good blend between enough angle to keep the puck moving while keeping it in touch with the board.
The angled support is made with two sides of a box connected at one edge. Placing that connected edge at the top, trim the sides down at an angle. If you open up the cardboard it will look like a giant bow tie.
When the angled sides are folded in the cardboard has triangular sides. A liberal spread of glue will keep these sides together.
Now it is time to wait for the glue to dry again.
Step 10: Adding the Chores
Since the middle goal slot is only slightly wider than the puck it is more difficult to land the puck there, so that became the "Get out of Chores Free" slot.
The other six slots have various chores (These can be changed or rearranged as needed).
Set and Clear the Table
Wash the Dishes
Take out the Trash
Vacuum the Rug