Can someone comment on the RPM and disc compression that works well on their curved shooter? We are only getting about 8’ with our shooter and not sure what variables we should be focusing on. We see some teams shooting almost full court and we are a long way from that. We would like to shoot from behind our pyramid.
Our shooter is a curved shooter using a 2010 8" FIRST Wheel, Rubber Treaded (am-0420) driven by a chain (not sure of gearing) from a 2.5" CIM motor (eg. not direct drive). Does it work best to gear up he motor (eg. have wheel spin faster than motor so motor doesn’t have to be run at full speed and have faster RPM recovery after a shot).
We added some Roughtop tread (AM-0523) to the curved fence and this increased our distance from 5’ to 8’.
The things that we found important are speed (RPM). compression and reducing friction. Granted, our shooter is not curved, but it does rely on the same basic principals as yours.
Good luck
Edit: after some digging here are some specs.
We use a 6" performance wheel directly driven by a CIM. Any faster and we found that we didn’t have enough torque.
The compression on the frisbee is about a half inch (the plastic actually deforms). The trick here is to find a point where you get the proper surface contact with the disk while not stalling your motor.
Reducing friction is the tricky one. You want the disk to travel through your shooter with as little resistance as possible while still imparting spin. We just used plywood with a nice finish.
1 The wheel
Trying to switch out the wheel with a different type it seems like the wheel you are using does not have much traction with the Frisbees
2 RPM of wheel
Faster is not better. We were testing our shooter and found that the wheels would grip the Frisbees better when they were going slower.
Watch this video. This is my teams new shooter. We learned from others. And yes we can shoot full court.
**Details **
Direct Sim Power
8inch wheel
Wheel filled up with air all the way
Slick sliding surface
Black frisbee “guide” on top of slick surface
1inch compression
At the time of our testing we did have the CIM running at full speed. It is important to have grip on the outside but it sounds like the wheel is not griping the Frisbee. I would advise to look at either compression or adding additional traction to the wheel. If the wheel isn’t griping the Frisbee adjusting other aspects would most likely useless.
My team has a curved shooter as well and from our experiences here’s my advice. As said before try different wheels we went through 3 types before we found what worked for us. Also don’t be afraid to just keep upping the compression because that’s where the actual distance the disk gets comes from. Also we ran a mini cim direct drive and that provided ample power for pyramid shooting. If you have any other specific questions just post below and ill answer as best as I can
We didn’t consider the pneumatic wheel because some teams indicated that it might come apart at high RPMs. Was this concern overstated (eg. not a safety issue)?
Is the 1" of compression just the disc or a combination of the disc and wheel?
Do you use the 1" compression the entire time the disc is in contact with the wheel or only the last several inches before release (eg. does compression increase as it moves through the curved shooter)?
Does your shooter “eat” discs (eg. cause unusual wear)?
Is your smooth sliding surface supported on the back side with curved aluminum flat stock? How rigid does this need to be (eg. does your sliding surface flex between support brackets)?
Does your last part of the shooter change the angle of the release (eg. looks like it slopes up at the end)? It looks like your Delrin (or other material) across the end of the shooter slopes down from the sliding surface towards the wheel? Is this because the disc when compressed climbs the outside sliding surface?
What area of the disc should contact what surface of the wheel? It looks like the bottom 1/2" in of disc edge is contacting below the center line (highest point) of the wheel. Is that correct?
What is the purpose of the plastic post just in front of the wheel?
We setup a curved piece of flatstock as a backing on our shooter (and posts of 80/20 that the flatstock is secured against), then added plastic (not sure what material, it’s the milky white stuff) in layers with double sided tape until we got the shot/compression we liked (this also covered up the fasteners inside the curve).
For the wheel, unfortunately, curved shooters are very difficult to swap wheels out in because the curve is (or should be) fit to the wheel, if you go bigger or smaller, your compression won’t be consistent throughout the curve, even if you move the wheel (you can make it work at the middle, but the ends won’t have good contact and you end up having a shorter contact distance even with a larger wheel).
We use a metallic wheel (apparantly it’s no longer available, but it was in the kit 3 or 4 years ago), with waffle tread (light brown rubbery waffle material). I think the wheel is 6-8", but I’m not sure. We direct drive the wheel with a standard CIM motor.
I don’t think you want to gear the wheel up for higher rpm (unless your chain drive already gears it down), we’ve found the sim RPM at direct drive to work very well with the right compression and wheel grip.
As a side note, balancing a pneumatic wheel wouldn’t really effect whether it “comes apart”, since it’s the RPM pulling the tread off the wheel that would cause that; balancing makes it much less scary though. I’ve not heard anybody say they’ve actually had the pneumatic wheels come apart since early on, but they aren’t designed for the RPM teams are using them at.
I would try working with your compression before you try changing wheels. Changing wheels means changing the curve, so it’s a bit more work.
Do you support the end of the CIM shaft? We had concern that the bearing in the CIM (if unsupported) would degrade from the side load of the disc going through the shooter. Has anyone had issues with that?
It would save weight and complexity if we could do a direct drive.
One thing we noticed with chain drive, is that chain tension is critical…if it’s just a little too tight, the binding will really reduce rpm (and distance).
987 uses a 6" smooth tread kit wheel from a few years ago, their curved shooter is spectacular. It might have something to do with the quality of the rest of the robot, too.
We hadn’t considered or observed the side-loading force as being a problem; however CIM motors are cheap enough that it’s not a burden to replace as long as it doesn’t die completely mid-match, just bring a few spares :).
We use a hall-effect sensor to determine our RPM (surprisingly easy to setup hardware for, code isn’t too bad either, I can share details if you want to give it a go), and shoot at 3900 RPM (we can get up to 4400 RPM with the wheel).
Aside from consistency, the closed loop (using a fairly simple bang-bang controller) provides a huge benefit to spin up time. We went from at most 1 shot per second (with inconsistency depending on how long we let it spin up), to one shot every .4 seconds, and much more consistently.
90 degree curved shooter. Two mini-CIMs driving a 4" wheel geared up to 9700 RPM. I think we have about 1/4" of compression against black roughtop tread. Shooting from the far side of the pyramid without issue. Ours didn’t shoot far at all until we added more compression (had 1/8" before).
Yes, the smooth surface is supported by an aluminum wall on the back. We support it with L aluminum brackets. It needs to be pretty rigid. There can’t be much flex at all
The only reason we angle it was to make sure the frisbee didn’t curve on the flight pattern. When you increase the angle when it comes out, it doesn’t curve as much when flying through the air. We are shooting full court so that is the reason we wanted that.
Think of a shotgun. The more accurate shotguns have a longer barrel to keep the bullet from moving much when it comes out. The is exactly what we are doing. That as a short barrel so the frisbee stays as straight as possible.
