paper: HOW TO: Make Homemade Orbit Balls

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HOW TO: Make Homemade Orbit Balls
by: artdutra04

Here’s how you can create a “Gus Ball”, an interwoven, spandex-covered ball that it functionally identical to the moon rock and fuel cell balls used in the 2009 FIRST Robotics Competition Game, Lunacy.

This PDF, as well as a downloadable MPEG4 video (for those of you with blocked Vimeo/YouTube connections at your schools or build season sites), is also available on GUS Team 228’s website at http://www.team228.org/media/documents/view/29

Also, a streaming version of the corresponding how-to video has been uploaded to Vimeo:
http://www.vimeo.com/2747374

How To Make Gus Balls - RevA.pdf (1.26 MB)

Thanks so much for posting this. Now that we know that we can only guarantee getting 4 balls max, making suitable stand-ins is more important than ever.

Has anyone built any of these? How many man-hours do you find it takes to make a non-fabric ball? How much does the non-fabric portion cost? We’re really looking to give our human players throwing practice.

I had five helpers and we made about 15 in 3 hours the other night. Three helpers then spent an additional 3 hours taping seems and cleaning up the edges.

For about $75 you can get a 4x8 sheet of 0.062 Polycarbonate. We then set up a jump shear 28 inches and sheared off 3 sections. We then set the jump shear for 1.125" and made about 110 strips. We used an 1/8" punch to put a hole in each end 1/2" in. We then followed the instructions from the instructable video. One thing I figured out too late is to make a wooden rivet pusher. Essentially a round slug that the pop-rivet stem can slide into (my fingers were very sore the next day). We then used special bonding agent after the straps were riveted. This acts as both anti-rotation and is also stronger than the aluminum pop-rivets. These balls seem nearly indestructible. We made 18 from 1 sheet and could have made at least 1 more.

All in all, 19 balls for $75 pollycarb, $5 glue, $5 pop rivet. You can buy a riveter at homedepot for about $12. If you don’t have a punch, you can use a drill. All in all 19 balls for about $100.

These don’t bounce quite like the real ones, but are accurate for size, weight, and feel. Most important they are more resilient so they are perfect for human player training. If you are planning on some sort of gather and dump system, they could work for the robot design, but I wouldn’t trust them for a shooter.

Does anyone know the name of the fabric that is used in the original Orbit Ball?

You can churn out non-fabric covered balls fairly rapidly. Simply cut 0.062" Lexan into strips and pop rivet. The two longest parts of this operation would be cutting the Lexan and deburring it so it would be safe for human player practice, and then the weaving process. It takes a little practice to learn the correct weave pattern. We’ve tried two different ways.

Weaving all six strips simultaneously. You’ll need two to three people two to weave and one to drill and pop rivet.

Weaving one strip at a time. Our preferred method, it takes two people one to weave and one to drill and pop rivet.

We estimated 2 man hours per covered ball in our initial tests, but I’m sure we can knock that time down if we set up more of an assembly line for production. That’s cutting Lexan, cutting fabric, cutting batting, gluing batting to Lexan, sewing fabric into covers, sliding the covers on, then assembling the balls. The extra steps from cutting, gluing, sewing the batting and covers, and installing the covers doesn’t add much time. Plus you can save a little time on deburring the Lexan since the fabric and batting will cover any sharp corners. The only other time consuming step is stitching the Spandex closed on the assembled Gus Balls. Its pretty hard to squeeze your hands into the ball to stitch the inside of the seam closed. I’m no tailor so it was taking me about twenty minutes to stitch all six strips closed.

After pondering this lengthy part of process, I’m now considering using gaffers tape to hold the spandex closed and hiding the seam behind another strip in the weave. Anyone want to try this right now, since we’re waiting for more 0.062" Lexan to arrive. :confused:

We paid $14/ yard for Spandex at a local fabric retailer, you might find it cheaper online. We estimate that you should be able to cover six balls per yard of fabric, therefore adding fabric adds about $2.50 per ball.

So our revised price per ball is closer to $8.00 USD. :cool:

If anyone finds a good source for inexpensive Spandex, please let the FIRST community know.

Go Teams!

Having spent most of the weekend helping to make Orbit Balls for our team and another local team, I learned a couple of things.

The label on our sample ball said it contains PU Foam (Polyurethane Foam, I believe). But when we opened up a damaged ball, there did not appear to be any foam, batting, or other padding. The fabric had some kind of knit backing, possibly rubbery stuff, but it did not look like foam. Someone said that in downtown Los Angeles (the Garment District, I presume), the same kind of fabric could be purchased. However, we did not choose to drive all the way downtown, so we just made our balls with ordinary Spandex and no padding.

Of course, anyone who has attempted sewing with Spandex will groan at the thought. My first attempts resulted in broken thread and a jammed machine every few inches. It took me a couple hours to sew the first few strips. I consulted with the ladies at our favorite local fabric store, and came away with the following:

–needles for stretch synthetic fabric (not ball point needles, which apparently are for coarser knits such as sweaters)

–new thread. I was told that over time, thread ages and can rot. I’ve sewn for over 40 years, and this was the first time I’d heard this. So I bought the exact same brand and type of thread.

After replacing both upper and lower threads, replacing the needle, adjusting the tension, and switching from a knit stitch to a slight zig-zag with a stretch-and-sew technique, I finally began getting decent results.

For those who have little sewing experience, here’s how to turn the tubes right side out: The old standby is a large safety pin. Open the pin, stick it through a single layer of fabric at one end of the tube. Close the pin, insert it into the tube, and keep pushing it through to the other end. Work the fabric over itself as you go.

A quicker way to turn the tubes is to go to a fabric store notions department and look for a bodkin. These are gadgets specifically designed for turning fabric tubes. They are essentially some kind of long stick with a fastener at one end. For this project, larger sizes would be better. I have something called an Easy Turn, which can turn a tube in a matter of seconds.

Once your Orbit Ball is assembled, you could use tape to fasten the ends of the fabric together. We discovered by accident that electrical tape sticks to Spandex really well. I suspect that one piece on the inside of the loop would do the trick. You might even be able to get electrical tape in the same color as your Spandex!

I’m not sure that fastening the ends of the tubes is even necessary, as long as one end is rolled under and overlaps the other end. Suppose you secured the ends by tightly stitching all the way around, like on the original Orbit Balls. Then if the plastic inside broke and needed to be re-riveted or something, you would have to undo all that stitching. My thought is that tacking the ends together with a few stitches in a couple places would be adequate, and make repairs a lot easier. It would save your team time, too.

Anyway, my thanks to you who pioneered this effort.

Anyone else noticed that the How To document for the Orbit Balls has disapeared?

I just went in and looked for you and it is where it belongs! So try it again! :slight_smile:

Its just not on the front page anymore. Just click the “more new papers” link.

After completing the first dozen or so balls, we have noticed that they seem substantially stiffer than the real balls. At some point, a decision was made to place the rivets at a slight diagonal in the overlapped space. Would that add the extra rigidity? Since we have predrilled the holes for all 100 balls, do you think it would be ok to use only one rivet per strip, or would we be compromising the durability of the balls? The rivet would be on one edge of the strip rather than centered.

Do the balls loosen up with time and play?
We are making them for the pre-ship rally. Do you think it will impact the other teams if our balls are more rigid than the competition balls?

The balls made with lexan will be a little stiffer than real Orbit Balls in general. Placing the rivet on a diagonal or inline may add to this stiffness, but generally just causing a stiff region at the splice. If the splices are rotated to different positions on the ball it balances out the stiffness over the entire ball.

We haven’t tried using only one rivet it may relieve just a little of the stiff, but will decrease durability. The material (lexan) is just a little stiffer than the plastic in the real orbit balls. This was a compromise between a perfect copy and price. Most of the plastics we looked at would have doubled the price per ball for construction.

As far as your pre-ship event. It should not have a major impact. This is usually a time for teams to shake out the bugs. If they’re relying on a pre-ship scrimmage to definitively test they’re design, that’s always a dangerous decision. Teams should always test their robots repeatedly under various conditions. Remember, Orbit balls can, and do, break, trackballs and other inflatables deflate, tetras break, teams must understand how these non-optimal conditions will affect their design.

Simply remind teams attending your event that these are NOT official playing field pieces, and performance of their robot may be affected.

You folks might want to check this out

http://www.chiefdelphi.com/forums/sh...192#post813192

Parents of a Team 980 student member have produced a kit for assembling ten, high-quality, durable Lunacy Game balls at ~$125 (shipping included) for on-line sale to FIRST teams:

Lunacy Game Balls - The Complete Kit

The professionally manufactured kit includes 60 pre-cut lexan strips, 60 sown spandex fabric tubes (30 ea. orange and purple), super-strength adhesive patches and tape for fastening the plastic strips, and simple instructions for assembling the balls.

It’s way easier to get them here than Wal-Mart b/c they’ve been discontinued. Hope this helps!