We are working on our shooter which is inspired (not a copy) of our shooter/pickup from our stronghold competitions. Things we change is to lighten it and combat chain related problems we will use belt drive instead of #35 chain drive and use mostly 3DP and 1/2 in square Aluminum or steel 16 gauge wall tube and probably a short conveyor to hold a 2nd ball Here is a mock up for a 1 ball version
Using M5 Bolts and using the plastic as a guide for holes/positioning etc.
Here is a prototype of 1 of the 2 tires (For fitting purposes printed in el cheapo filament) which is going to be printed in TPU
Pulleys are also in PETG (I got 50 kg for 470) and we know from experience it will stall a Cim multiple times without damage with the 2mm key it has and tight (press fit) tolerances Shooter will get an axle to tilt down to pick up and then elevate/rotate into shooting position depending on if we get the targeting worked out properly it should be able - at least mechanically)to reach the target from anywhere on the field
Adapters for 1/2 in square shaft to 6805 bearings we decided to move away from hex shaft to square shaft as - especially with plastic but also with aluminum 1/2 in hex or smaller eats plastic and aluminum hex hubs sooner or later. 1/2 in square - especially tubing (inside hollow is lighter and does not eat plastic hubs sooner or later and is also easier to drill accurately
Like every year for everything cad will be published in the off season
so its going to shoot the ball the curvature conforms to the ball. And there are 2 to give way much accuracy. One wheel shooters are not that accurate the problem is that - to shoot you need to compress the ball that means it bounces away from the rigid side opposing the wheel - like in a C shooter. Now it states and has been true every year we were shooting balls that each ball bounces differently s you get 1 vector the forward speed from the wheel and another - uncontrollable one - from the bounce when it leaves the shooter so there is always an error in the resulting vector. With 2 opposing wheels You get 2 “bounces” 1 from the left wheel, 1 from the right wheel which are the same and in opposite direction and so cancel themselves out. The more squish you get the less slip between the ball and the wheel you get. So in years past we had softer balls that where easier to squish so using a hard wheel was ok This year we have a relatively hard ball so we are trying soft (TPU) wheels that will deform a 400ish gram 100mm tall and 100m at the thinnest spot wheel with 2mm walls and 5% infill out of TPU is not that easy of a print and as you can see we have some blemishes. Also nozzle and layer height is rather big to reduce printing time and so there is - as you can see - some stringing. But that should be ok. Its currently being printed on my slightly modified predator (370 mm diameter build plate with a mosquito style hotend and custom 3dp effector plate/fan/hotend mount assembly. I hope it finishes. as you can see there are slight variations on some layers - looks like ringing but its caused that the TPU the taller it gets slightly reacts the the mechanical forces of the printing mechanism. I use the predator instead of the chiron on this as with a delta printer compared to a bed slinger there is less “jiggling” of the part and the bowden tube is much shorter so there is less problems wiht “stuffing” the filament through it. I might at some point build a TPU printer with direct drive. All in all its about a 14 hour print it seems. The indexing will most likely be done by a PG 75 motor with a herringbone (double helical) gear as we can do them with no noticable backlash and that will be HIPS or Nylon.The drive will be 2 650mm (we got a ton in stock) HTD 5 belts each on a CIM motor on an adjustable mount to make sure the belt can be tightened
And PG75 for elevation (indexing) cause we have a bunch and they have an encoder on the back so that helps with that
Here is a prior year similar shooter in action with hard wheels
You can see at that test (slow motion) We fired a little to fast and did not allow the speed of the 2 Neos in that case to recuperate making each shot a little lower bot they are straight - no curves due to ball spin - and they leave the shooter dead center and straight as the 2 Bounces cancel themselves out
each of the ribs/teeth has enough room to “fold” over to increase the length of time the ball stays in contact with the wheel so I am optimistic this will work well. Kids still have to cad the 2nd part of the hub. There is an intential 2mm gap to allow the 2 hubs to squeeze the “tire”
One of the students will remove the brim later today
About 400 grams of TPU, 450 gram of PETG per hub/tire combo per wheel. Printed on sub $ 500 printers (You could print it on an ender 3 if you upgrade to an all metal hotend as this TPU prints at 260-265
