Soccer rebounder - looking for fab ideas

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I recently picked up a used Lincoln Squarewave 175 that I have been using to fabricate useful odd and ends and can run a reasonable TIG bead with it.  The other day, a co worker found out I had a welder and asked if I would be willing to build a soccer rebounder for his kids.  Basically, it is an 8' x 24' frame that holds a net taught enough to return the ball when kicked into it.  I questioned the need for something 24' wide, but apparently that is the width of a regulation soccer goal Looks kinda like this:For reference, this particular unit would run about $600 delivered if store bought....In thinking about it, I was planning on using square steel tubing (not skilled enough to think about Al yet).   A couple of questions though for you skilled fabricators and metal workers? - What size square stock would you recommend?  There really isn;t any load, per se, on the frame, but you wouldn't want too much sag on the 24' span.  It would be a shame to make this heavier than it needs to be- This thing would have to be disassembed and stored each fall.  Consquently, the frame would have to be broken down into 8' sections.  Any ideas on how to make the top cross bar sectional so it can be taken down for the season and stored away?  Assuming I use three, 8' sections of tubing, what would be the best way to securely connect them?  Does square tubing come in varied enough sizing so that I could get one tube that would slide securely into the frame tubes to support a joint?  Any other thoughts?
Reply:Try telescope tubing- Local Steel yard should be able to get it or have it. Common out here.http://www.alliedtube.com/steel-tube...telescopic.aspEd Conleyhttp://www.screamingbroccoli.com/MM252MM211 (Sold)Passport Plus & Spool gunLincoln SP135 Plus- (Gone to a good home)Klutch 120v Plasma cutterSO 2020 benderBeer in the fridge
Reply:Great Idea !If you really think about it, you could likely make the bottom supports out of steel (for stability) and the rest of the unit out of AL....  I don't see a 'lot' of welding here.Anyway...,If I were building it out of steel, I would consider a smaller OD at the top and perhaps an additional larger OD support at the bottom of the same length.  I would also consider 8' lengths with connecting sleeves (slightly larger inside diameter pipe lengths around 18" long to connect the 8' lengths) for both top and bottom supports.  I wouldn't think you would have much problem finding the proper 'dimensions' (inside and outside OD) for your purpose.  Doing it this way might enable you to keep the longer 'top' supports a bit smaller in OD and therefore a bit easier to assemble for the kids and such..You could likely put in more footing on the bottom sleeves but I'd likely use a ' V ' shape instead of what's pictured there so there would be more stability for side shots and really HARD ball shots and repeated stresses, etc..Alternatively,...Have you thought about PVC ?  The fit up would basically be perfect, the unit lighter and you could use thick diameter pipe.  The thicker OD pipe would allow you to use just about any anchoring system as well !Cheers,/Jman...
Reply:JMan -The general goal is to design it so it will dismantle into 8' max lenths for storeage.  The connecting sleeves (preferably internal to the framework) is what I am looking for input on.  Broccoli's idea of the telescopic tubing is the closest to what I was thinking so far.  I'm curious what a length of it costs....  Aluminum would be nice as it would save me a bunch of prep, priming, and painting.  Maybe I'll go get some Al scrap and give it a try.  PVC would work, but it is also subject to potentially shattering or cracking under the right circumstance.  Plus, I don't get to weld it!With respect to the supports, I was planning on some flat stock (like in the picture) with some sort of ground spikes to hold it in place.
Reply:More ideers...We put together 10x10, 12'x12', 20'x20'  Etc etc  sized Frames for Photo shoots and stretch material across the frames.Sleeve the Frame and Corners for breakdown, couple pics of the connectors. Attached ImagesEd Conleyhttp://www.screamingbroccoli.com/MM252MM211 (Sold)Passport Plus & Spool gunLincoln SP135 Plus- (Gone to a good home)Klutch 120v Plasma cutterSO 2020 benderBeer in the fridge
Reply:a nutter option is Canopy Corners & connectors as they support common size tubehttp://www.creativeshelters.com/Fitt...y-Fitting.aspxEd Conleyhttp://www.screamingbroccoli.com/MM252MM211 (Sold)Passport Plus & Spool gunLincoln SP135 Plus- (Gone to a good home)Klutch 120v Plasma cutterSO 2020 benderBeer in the fridge
Reply:Originally Posted by Broccoli1More ideers...We put together 10x10, 12'x12', 20'x20'  Etc etc  sized Frames for Photo shoots and stretch material across the frames.Sleeve the Frame and Corners for breakdown, couple pics of the connectors.
Reply:I don't make them- just use themEd Conleyhttp://www.screamingbroccoli.com/MM252MM211 (Sold)Passport Plus & Spool gunLincoln SP135 Plus- (Gone to a good home)Klutch 120v Plasma cutterSO 2020 benderBeer in the fridge
Reply:I made a similar one for my kids - but ~ 8' across.I uses 1 1/2" tubing for the uprights and cross members. I welded a 3" piece of 2" tubing onto the underside of the cross member at each end - the cross bar just drops onto the uprights. I later welded a 3" piece of 1 1/4" tubing to the inner side of the base of each upright and use a 1" cross member at the bottom (the shock cord was pulling the bottoms of the uprights together.) I used a rear leg at ~45 degrees to support mine, rather than the flat bar.When the net is stretched on - holds the whole thing tight.If you need a cross bar that breaks down, at each 8' increment weld a 10" piece of 1 1/4" inside the 1 1/2" and slip it into the adjoining piece. Only need a couple of inches into the piece welded to - leave about 8" to slip into the other piece. No need for pins or bolts - the elastic will hold it tight. I just went to my steel supplier and picked thicknesses that slipped into each other with the "right" amount of clearance. 0.100" wall 1 1/2" seems to be about right over top on 1 1/4"I initially used a truck cargo net - but the sun ate the bungie cords pretty quickly - went to netting with some shock cord weaved into it. Doesn't bounce the ball back as hard - but it still stops them nailing the windows on the house quite so often.Here's an old picture - before the bottom cross member was added. Attached ImagesLast edited by Big_Eddy; 06-01-2009 at 12:58 PM.
Reply:If it where me here's what I would do.Get your aluminum square tubing 2x2" is what I would use.Rather than welding the corners get some steel square tubing with an ID of 2.0625".Weld up some of the steel tube into an L shape. Give yourself about 3" or purchase for the aluminum to slide into.Drill a pair of holes on two sides of the steel tube so you can weld a pair of nuts onto the steel for a pair of bolts to clamp down on the aluminum.Make yourself a base that can accommodate some nice large spikes to hold it all down.For the corner brackets I would recommend cutting 2 3.5" piece of steel tubing and welding a plate to the end of one piece. Then weld the second piece on the end of first piece to make an L.Paint the steel, and enjoy.Basically you are making simplified square versions of these.
Reply:Kids being kids, they'll probably try and use the top cross-bar to hang from/on.  So ixnay on the PVC option.  Twenty four feet of PVC pipe -ain't- gonna hold up a kid too well.And as Eddy posted, a bottom cross-bar may be needed to hold the uprights from pulling inward AND to keep tension on the rebound netting along the bottom area of the netting.  Otherwise the net just sort of stops the ball instead of rebounding it back to the player.24 ft span (simple beam load condition, as opposed to a fixed beam), assumed 100 pound kid hanging in the middle and a distributed net 'tension' load (the tension on the net that is pulling on the cross-bar from the bungies/shock-cord/etc) of 25 pounds per foot of length of the bar/beam, and you need a pretty beefy top bar to not have it fail in bending from that kid hanging in the middle.  In steel, standard 36 ksi yield (A36 or equivalent) material means something like a C6x13 channel or a HSS5x4x3/8 rectangular tube in order to keep the bending stress low enough to not fail the bar/beam and to keep the deflection low (about 1/2 inch in this case).Even without the kid hanging in the middle, you still need about a steel C6x8.2 channel or HSS5x4x1/4 tube to keep the bending stress low enough just from that long length and the pull from the net (assumed to be a distributed force of 25 pounds per foot of length of the top bar/beam).  Cause that pull from the bungies adds up to 600 pounds all together!YMMV, etc, etc.And, yup, the dimensions of the goal are listed as 8 yards (24 feet) apart on the inner edges of the vertical posts and the lower edge of the horizontal cross-bar must be 8 feet above the ground.  http://en.wikipedia.org/wiki/Soccer  The best laid schemes ... Gang oft agley ...
Reply:Moonrise -Thanks for the math!  The good thing is that my coworker's kids are Jr. High age so at least they should have enough common sense not to hang on the cross bar (I know.... big assumption, but let's run with it).  In college, I had a buddy who's father was a plumber.  He constructed a set of lofts for his dorm room out of black iron pipe and various fittings.  To keep people from hanging off the cross bars, he smeared the tops with vasoline.  Needless to say, no one did it twice.....In looking at one of Broccoli's posts, he pointed to the Creative Shelters website.  They have plenty of fittings and other doo dads for building shelters out of 1 3/8" tubing.  Corners, unions, and so on.  Assuming the little grommets aren't going to be hanging from the cross bar, would you expect that a full 360 degree frame of 1-3/8" steel tubing would suffice - assuming we can mitigate the bungee force somewhat?  I would assume the net wouldn't have to be spiderweb tight......With these connectors and tubing, the only welding/fab I would have to do would be for the bases and ground spikes to hold it down.Last edited by mackdx; 06-02-2009 at 11:57 AM.