Hello,
I have seen a lot of hooded shooter implementations where teams were able to create a flat hood out of aluminum. What are some simple ways that we can achieve this considering we don’t have a lot of experience in this domain? Would another material than aluminum be a better option? Please share your ideas.
polycarbonate is great because you can ziptie it to some spacers and it will take the shape of the arc you create. you just have to drill holes in the shape of the arc you want to create run bolts and spacers through it and ziptie the plastic to the spacers. cant find any examples right now maybe someone else can add some screenshots.
Polycarbonate is a really easy option for making a curved hood. Just make sure it’s rigid - otherwise, it will eat a lot of the energy you’re putting into the ball. For one of our shooter prototypes this year, we bent a sheet of it around curved pieces of wood, and constrained it using churro tube behind it and L-gussets to mount it to the wood. Worked like a charm!
As the other two replies have suggested, polycarbonate is a great alternative. However if you are set on using aluminum, if you have a metal shop near you, there’s a good chance they’ll have some sort of metal roller. In our shop we have a three in one tool with a sheet metal shear, bender, and roller. We made a really nice and quick curved hood for a prototype using it in the beginning of the season. You might unknowingly have one or have access to one; they’re more common than you might think.
If you use something like 3003 aluminum, instead of 6061, and you pick the right thickness, you can bend a pretty decent curve over your leg, or another large round object. I would guess a thickness in the .030-.063" range would be appropriate.
But it’s also likely that hand forming metal parts, without using a machine, is anathema to your build policies 
We use this little guy:
Used the 2017 shooter as an excuse to purchase it.
I would also recommend the polycarbonate-and-standoff method if you don’t have good sheet metal resources.
However, my team has made aluminum shooter hoods in the past and will be using one this year. The parts are laser cut and the bent on a CNC press brake. The finished product looks like this (this is our 2016 shooter hood):
This would normally be riveted to flat side plates of some kind.
One question I get asked a lot is whether the faceted nature of the hood causes any problems. It does not. The “bumpiness” is actually less severe than it looks and the ball really doesn’t seem to care about it.
If you don’t have access to a laser cutter/waterjet and a press brake, you can still make this part by hand, albeit with less precision.
You’ll need a manual brake (a vise could work in a pinch but the part might be pretty ugly). Cut out a rectangle of aluminum that is ~2in wider than the width you want for the shooter hood.
Bend ~1in flange on either side to make a wide C channel. Like this:
Use a Dremel, angle grinder, or even snips to make V-shaped notches in the flanges. It is VERY important that the notches line up on either side of the part.
Once you do this, you can make the slight bends (at the point of the V notches) to form the hood. Use the brake if possible, but you could probably make these bends by hand if needed.
Also, you could design the part in CAD, flatten it, and print out a 1:1 scale flat pattern on paper. Glue the paper to the piece of aluminum and then cut it out with a band saw. Then do the bending.
A note about alloy here. You cannot use aluminum 6061 for forming. It’ll crack under most conditions. 5052 is what is used for most aluminum sheet metal parts.
EDIT: I forgot a step. Once you’ve done all the bending, just clamp it to your side plates or shooter structure and then match drill through both parts. You can then bolt or rivet it together.
We have fired our shooter with and without the polycarbonate and it doesn’t seem to care much either way. We’re keeping the polycarb just in case a ball gets damaged — we don’t want it catching on the standoffs.
On a slightly separate note: How was that inertia wheel made? Looks really good
Thanks! We bought a 7" chunk o’ aluminum round stock, used a lathe to face and pocket it as well as drill and ream the center hole, used a CnC mill to cut the spokes, then broached it with a big honkin’ press. Oh, then after testing we turned the knurling off of it, because it shredded the skin on the balls – the smooth aluminum grips great on these balls.
This post shows some pictures and video of the process.
Wow that’s really cool… we were thinking of ways to make a flywheel and this looks like a really good way
I expect that is a big hunk on your BOM? 
I looks great. I am jealous.
$55. No big deal at all.
If you’re going to make your own, it’s CRITICAL that it’s well-balanced. Very dangerous otherwise.
It would be an ambitious project for our 9" South Bend.
I see why you insist on a low robot, that’s a lot of weight right there!
It was an ambitious project for us, too – we had to start with a four-jaw chuck, which is a real pain to get centered well. Fortunately, the technology teacher who runs the metals class offered his help; we couldn’t have done it without him.
As for weight–sure, 6 lbs is a lot, but if you’re going for maximum consistency with minimum weight, you want as big a moment of inertia as you can get per pound. A 5" diameter, 1" thick steel disk also weighs about 6 lbs and has a moment of inertia of .0055 kg * m^2, rather than this wheel-flywheel combination with a moment of inertia of .0072 kg * m^2 for six pounds. …so overall, for similar performance we’re saving weight rather than losing it.
I wasn’t just referring to the flywheel, the whole assembly is a monster. I expect it will work well.
We’re under a hundred pounds total.
And it’s mostly down low, which is good!
Use a slip roll. It’s meant to bend stuff like aluminum and it will be a perfect angle.
