Marble Vortex Repair / Upgrade

Our MakerSpace Maui Makers (yes on the Island of Maui, HI) has this Marble Vortex (actually a demonstration of how a gravity well works). Marbles are rolled around and then drop into the gravity well. This demonstrates how planets orbit a star. It is shown in the first photo after it fell off of a car roof rack on the way to an event. One of our members constructed it a number of years ago, and the basic functional unit was intact. Luckily, it was just the legs and support structure that broke when it hit the asphalt; the rest of the Marble Vortex was still in good shape, so for that event, we propped it between two tables and used it as shown in the photo with the orange bucket.

This accident also created a great opportunity for us to convince the original maker that we could improve the portability, stability, and usability! The overall original size would not fit in a standard 4’ x 42” x 4’ H pallet box, which meant we couldn’t ship it from Maui to the Oahu Mini-Maker Faire on another island. We had also noticed that the marbles flew all over the place, thus we needed a rim around the top to prevent them from escaping due to overzealous little hands! While this instructable doesn’t go into detail on the original Marble Vortex build, here is a short description: The top (black in the photos) was made by cutting a round 36” hole in a 4’ X 4’ plywood sheet. Lycra fabric was attached over the hole, and a golf ball was used to stretch the fabric down about 16” and create the proper shape. Once this was accomplished, fiberglass resin was used to coat and stiffen the material. Multiple layers created a stiff surface, which was sanded and spray painted with black enamel. Four diagonal braces stiffen the underside of the plywood top (you can see them in some of the photos). This made cutting down the size a bit difficult.

Router, Hand Saw, Router Table, Miter Saw, Trim Router Bits, Clamps (lots), Cordless Drill and ½” Bit, Cordless Driver, Back Saw or Pull Saw, Wood chisel (old), Speed Square, Tape Measure, Putty Knife, Sanding Block, Box Cutter, Hole Saw, and Bandsaw or Coping Saw

Problems working in Maui: Space is very costly, so some tools are not readably available in our Makerspace. One that I miss is a table saw, so I had to work with only a miter saw and a router as well as cordless drills.Starting the repair

1 x 6, 1 x 3, 1 x 2, and 2 x 3 pine lumber; urethane glue (aka Gorilla Glue); 1” drywall screws; 5/16” carriage bolts; wing nuts and washers; threaded inserts and screw-in table feet; 3 large snack jars with lids; 1-½” PVC Pipe and fittings; 1/16” brass rod; wood filler; paint and brush; disposable gloves and disposable brushes for applying glue (½” acid brushes); wax paper.

• Wear disposable gloves when using urethane glues. Buy only enough urethane glue for the project (the shelf life is poor if it is not handled and sealed properly).
• Use wax paper between glued surfaces and tools and other parts to prevent sticking.
• Wear appropriate personal protection devices while working

I do not have photos of these steps:

1: Remove the old outside frame without destroying the whole thing: The upper side had fiberglass, and the wood edges were nailed and fiberglassed to the top. I drilled holes at the corners and the inside edges of the diagonal braces. I was afraid of delaminating the fiberglass so I used a 3/8” router bit with a bearing on the end and cut the fiberglass from the black side (top) using the inside of the old frame for the guide. I then used a hand saw to separate the diagonal braces from the outside frame. I stayed to the far side of the router slot opening to keep away from the short nails that were used for original assembly.

2: Remove the ends of the diagonal braces so a new support board could be attached: I marked the diagonals at about 1-¼” in from the new edge of the top so I would have some material to trim after they were attached. I used a back saw to cut the ends off, and an old wood chisel to remove them from the plywood.

3: Cut the inner frame for the plywood: I then measured the approximate square frame that would be created by a wood edge at the ends of the diagonal braces. I used this measurement to cut 1 x 2 pine strips to length and then cut rabbets (using the router and router table) on the ends of two of them to form box joints. To fit these, I started at one edge and clamped it in place (dry) and worked my way around. Since I’m doing a repair, exact dimensions are not necessary just squareness of the frame.

Attaching and assembling the frame to plywood top:

After I was happy with the fit, I removed one piece loose at a time. I moistened the plywood side and ends, then put Gorilla Glue on the long edge and re-clamped to the plywood. I then did the same to the opposite side. I had only 10 appropriate clamps; I used 5 clamps per side, so I had to wait until it set before I could move on. Once they were set, I did the other two sides, placing glue on the ends. In addition to the 5 clamps per side, I used long clamps to clamp the corners.

5. Trimming the top: After the glue had set and cured, I flipped the top so I was working from the black surface. I used a flush trim carbide router bit (bearing guided) to remove the plywood, fiberglass, and glue that was on the outside of the wood support frame. This left me with a strong assembly with a smooth outside edge to work from.

6 Building the upper face frame: For this I used 1 X 6 pine lumber — the straightest I could find. Since the longest side was now less than 48”, I cut all of the 8’ lengths in half on the miter saw. I measured the largest thickness of the combined face frame and top, adding 1/8” to account for any warping. I decided that the upper rim of the new table should be about 1-¼” high to account for any marble bounce, so i created a ⅜” deep rabbet the full length of the face frame pieces. The width I used was equal to the thickness + 1-¼” from one edge, with the router mounted to a router table with a fence to use as a guide. I used a ½” carbide bit. I selected the edge that had the most defects for the side to rabbet. I would eventually also rabbet the ends of two of these.

7 Cutting the face frame length: This is the tricky part. First cut the length of two boards 1-¼” longer than the top is wide. This will allow for excess to cut off in final assembly. Next mark the inside side (with the dado) so that you have a reference. The length between the marks is ¾” less than the width of the top (on the sides where these boards will be attached). Make sure you center the marks on the board. Next using the router and router table, cut a rabbet on each end of the two boards ⅜” deep all the way to the end of the board. Clamp (dry) these two boards to the corresponding edges. Next measure the length between the dados when they are mounted. Use the miter saw to cut the remaining two boards to their respective lengths (don’t cut both at the same time). Sneak up on the measurement to get proper fit. Clamp these two in place and check for frame squareness. When satisfied, glue the face frame. Repeat the procedure for the last frame, but add 1” drywall screws at 8” intervals between the face and support frames to keep the expanding glue in check. These screws will be removed later. Once the glue is set and cured, use a box cutter to remove any excess that has squeezed out. Now is the time to use the back saw to remove the ends sticking out from the corners.

You now need to construct an identical sized frame to support the bottom of the fixed legs. Use the same process as Step 7, but without the long dado. Build it on top of the last frame as it needs to be the same size on the outside. Note that only the corners are glued.

The frame legs are composed of two 1 x 3 pine boards cut to length and joined with a rabbet joint along the edge. The length should provide adequate protection for the bottom of the fiberglass cone, as well as providing space to mount a ball catcher assembly. This was 22” in our case. I used the miter saw to cut 8 pieces 22” long from the 1 x 3 stock, picking the straightest lengths. I then used the router (mounted to the router table) to cut a ¾” wide by ⅜” deep rabbet along the edge of four of them. I glued these pieces together using the methods described in Step 7, clamping till cured. Now I used the miter saw with a length guide to clean up all of the ends and cut to the same length.

Cutting the Rabbets on the ends of the legs:
I used the router table to cut rabbets on the outside faces of both ends of the legs. These rabbets were ¼” deep and on both faces. Make sure the shoulders of the rabbets are the same distance apart on all four legs. The width of the rabbets are different on the two ends of the legs due to the depth of the wood they are attached to. To make this easier, clamp all four legs into place on the inside of the frame on the top and mark them. Cut one end of all of them at once then do the other end.

Gluing the legs:

At this point, all of the legs should be clamped at both the upper and lower frames in the corners. Remove one leg at a time and glue using the method described in Step 7. Use clamps to hold in place. Wait until all glue cures before proceeding to next steps.

Remove excess glue Use a box cutter and wood chisel to remove excess glue from outside of unit.

Smooth edges Use a router with a 3/16” roundover bit to break all the sharp corners and edges.

I cut 4 pieces of 2 x 3 pine to 22” for the folding legs. I drilled a 11/32” hole through the 2” depth at 1-½ “ from the end, centered in the width. I then used the bandsaw to put a full diameter curved edge on it. On the other end I mounted a threaded insert matching the screw size of the adjustable foot. Drill the pilot hole for the insert 2” deep. This gives room for the foot stem threads.

Mount the legs:
Clamp the legs to the table so they have room to fold in. Use the hole in the leg as a pilot for drilling the pivot bolt hole. Place a carriage bolt from the outside through the frame, a flat washer for spacing, and then the leg with another flat washer. Finish with a nut of your choice My suggestion is a nut with a locking feature or Locktight. Once you have the leg attached, drill a second hole near the bottom support frame 90 deg from the other bolt ( see in picture above that the leg bolts are 90 deg to each other) across the long width of the leg. This will act as the anti-folding attachment. Use a carriage screw from the outside again, but the center washer is not needed and the nut can be a wing nut. Make the hole through the leg larger to make it easier to remove for storage.

This was an afterthought. I used 1-½” pvc fittings and three plastic candy jars to build a catch chute so the marbles are directed to the outside of the unit. The original design used a 5-gallon bucket in the center. In the center is a cross PVC fitting (used for venting drain lines). In the middle I placed three ⅛” brass rods spaced about ⅜” apart. I bent the middle higher so the balls would be directed to the sides and coins could drop through. This is about 90% effective. I had to do a lot of experimenting to get this to work. In order to provide access for jams, the outside ends are standard “T”s with the extra end plugged with a 1-½ to ¾” adaptor fitting (not glued). The support board is a 1 x 4 with three holes drilled through for the PVC parts. I mounted the lids for the candy jars on the board first and then drilled through the lid and then the wood. I attached the board at both ends with ¼” knobbed bolts and thread inserts into the side frame. I had to relieve the upper edge of the frame to provide enough clearance when I added the coin feature.

Addendum Coin Ramp:
This was an upgrade I added, just to to see if I could. I used a Hot Wheels track and two aluminum strips to connect it to the top, as well as providing shape and support. The exit angle is critical to get coins to roll around on their edges. The track needs to be aligned with the edge tangent to the profile of the hole with a gentle transition to the surface. The mounting allows the ramp to be upgraded to get the proper angle through trial and error. Kids also like to use it to launch the marbles.

This is when I did the final fill, sand, and finish.

The ball catcher system will hold about 10 lbs of marbles before it needs to be emptied. Small children will play with it for as long as you can stand the noise. It is LOUD, especially on a solid floor in an enclosed space. Outdoors on grass was an improvement.