Curved Shooter help
 

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'.

Thanks.

Re: Curved Shooter help
 

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.

Re: Curved Shooter help
 

For me a picture would help to go with the description.

Re: Curved Shooter help
 

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.

Re: Curved Shooter help
 

Are you running your CIM at full speed? We read that some found that by having friction on the outside increased the discs spin and stability.

We definitely are not compressing it anywhere close to what you are. We will try that during the next practice.

Re: Curved Shooter help
 

http://www.youtube.com/watch?v=S-r5s...E_2wQA&index=2

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

Re: Curved Shooter help
 

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.

Re: Curved Shooter help
 

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

Re: Curved Shooter help
 

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)?

What worked best to balance the pneumatic wheel?

Re: Curved Shooter help
 

The pneumatic wheel works great!! It is a charm.

To balance it, haha we actually took some washers and taped them up with duck tape. Then we put them inside of the wheel "bracing" with a secure fit.

Re: Curved Shooter help
 

What PSI do you have in the pneumatic wheel?

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)?

Re: Curved Shooter help
 

We have the PSI at 35. (Recommend for that wheel.)

The 1" compression is just on the disk. The wheel does not give any because it is at high air pressure.


We use the 1" compression all the way through the entire curve

The shooter does not eat the disks. As long as you have a smooth curved surface, it will be fine.

Re: Curved Shooter help
 

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?

Re: Curved Shooter help
 

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.

Re: Curved Shooter help
 

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.

Re: Curved Shooter help
 

Those of you running direct drive to a 6-8" wheel using the CIM, are you running the CIM at max RPM or something less (eg. 70-80% power)?

Re: Curved Shooter help
 

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.

Re: Curved Shooter help
 

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.

Re: Curved Shooter help
 

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).

Re: Curved Shooter help
 

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.

Re: Curved Shooter help
 

We currently run at 100% power for our direct drive with a mini-CIM (more specs here).

Re: Curved Shooter help
 

We have a "combined" shooter:

A mini-CIM directly drives a small ~2" "starter" wheel, giving the disc an initial velocity and rotation before it comes in contact with a 6" AM performance wheel with wedgetop tread. This main wheel is driven by a full CIM sped up to a 1:1.2 ratio by a belt. The curved part of the shooter is about 70 degrees and has wedgetop on the curved wall.

Both motors are run at a "fixed" voltage of around 11 volts to account for battery voltage varying during the match. (We read the battery voltage and adjust the input to the speed controller accordingly.)

I don't know what the compression is, but it is not that much - perhaps .25". The wedgetop and the starter wheel really reduce the amount of slipping.

It shoots full court easily and accurately as seen in San Diego. In fact we were very surprised by how well this combined system works.

Good luck!

- Mr. Van
Coach, Robodox

Re: Curved Shooter help
 

Here is a slow motion video of our prototype shooter. We are running it direct drive with a CIM at full speed. Our real shooter uses 2 RS775 motors controling to 4000 RPM, so similar. We have quite a bit of disk compression. It is hard to force the disk through the shooter with your hand and you have to spin the wheel to get it out. We were definitely one of the hardest shooters at our past regional. We shoot full court.

http://team2052.com/Slow%20Motion%20Shooter

Re: Curved Shooter help
 

We have our curved shooter set up like this.
Direct drive mini CIM driving a 4 7/8 in banebots GREEN wheel.
We keep the rpm down to 4500 and easily shoot from behind the pyramid and much further. We use about 3/8 inch compression which humps the disk up about 1/2 inch. We use a progressive compression. At entry to the shooter there is only about 1/8 inch and at max it is about 3/8. Shot to shot is something like .4 seconds or less. Yes, the green banebots get eaten up but the funny thing is it does not seem to matter. New wheel or half eaten up wheel shoot to the same place from the pyramid. We do have a "few" extra wheels just in case.
Our frisbee wall is 1/4 inch laser cut polycarb with a rubber U channel over it for grip. There is a wider piece over the top to keep the frisbee from walking up and we angle the wheel down about 3 degrees at the exit. This keeps the bee from turning to one side.
Hope that helps.

Re: Curved Shooter help
 

We did lots of prototyping of our shooter.

Our shooter:
CIM motor with wheel mounted directly to it.
Wheel is custom made out of HDPE
-8" diameter x 1" tall
-Wedgetop tread mounted to the HDPE wheel with rivets. Ends attached with AM clamps from performance wheels.
Shooter deck is made of HDPE sheet that is 1/2" thick. We had to brace the bottom of the deck to prevent sag which caused more compression on the frisbee.
Rails of shooter are made of HDPE with weather striping foam on inside edge. The rails are attached by machine screws about every 5" to prevent warping/bending when the frisbee moves around it.
The spacing from the shooter rail to the wheel is 11 1/16 inches. The foam is 1/4" inch thick so we get some compression on the frisbee but not much.
We also have a lexan cover over the top of the entire shooter.
You can see a picture of it here: http://www.chiefdelphi.com/media/img...ed21b3a4_l.jpg Notice that the wheel here is a performance wheel that has been replaced.

Here is an image with the shooter on the robot: http://www.flickr.com/photos/chaprob...57632928507774

Compression and surface on the wheel and rails were were the factors we spent the most time on. The diameter of the rails need to be determined by the size of your wheel so it is consistent all the way around.

Our shooter actually shoots better without full voltage. We have experimented with 9.2 - full voltage. I do not have any specific data but we mark the frisbees less with lower voltage and get more consistent distance and accuracy we think with the 9.4-9.5 voltage range. We competed at our first tournament and our encoder was not giving us the feedback we needed to control the shooter speed. We ran either full voltage or 80% for all the matches.

We can shoot from full court consistently at the two point goal.


Hope this helps.

Re: Curved Shooter help
 

What material is your "black frisbee guide on top of the slick surface"? How high above the frisbee do you have it and how far out does it protrude from the slick surface?

In your video it looks like your frisbees have black marks on them. Is that from this material or the wheels?

Thanks.

Re: Curved Shooter help
 

What my team noticed when experimenting with the shooter is that there are a couple of factors. First thing is that Higher RPM doesn't necessarily give you more distance. We are running a direct drive Cim to an 8" wheel. We have about 1/4 " compression on the frisbee from the side. We added a stop at the top with some more compression near the exit of the shooter.(basically it funnels a bit). The angle and height at which your shooting make a big difference as well. Greater angles give you less distance. For our full court shots we run the Cim at about 90% power. We put a weight on top of the wheel as well, pretty much just a steel coupler since we noticed stability and no wobbling when we added that. The interior is lined with plastic(the back end of the Regolith from Lunacy since we had a ton of it). Another thing that effects the firing is how you push in the frisbee. The angle at which its being pushed in and speed.

Re: Curved Shooter help
 

Do you know off hand what angle you shoot at for full court?

Re: Curved Shooter help
 

Off hand i would say the angle is around 20 degrees.Its something you need to play around with.

Re: Curved Shooter help
 

Info on our curved shooter:

https://www.youtube.com/watch?v=S5gVpo6PZh4

Check out 1:08

90 Degree wrap
8" 40A durometer rubber wheel
CIM motor direct drive running at ~2000 (normal shot) to 3000 RPM(full court)

We use very light compression and the reason is that when you compress the frisbee, it will bend which causes it to track vertically on the curved wall of the shooter. This can result in extra friction or a curving shot. Using a softer durometer wheel provides a lot of traction which permits significantly less compression.

Also, if you are shooting at full speed and you start to see a purple halo on your wheel, this will make you shooter almost nonfunctional. This happens
when you are spinning your wheel too fast and it is melting the frisbee upon initial contact. You have to grind the halo off as soon as it starts to appear. Once it gets fairly thick, its almost impossible to remove.

Hope this helps.

~Matt

Re: Curved Shooter help
 

Where did you get your wheel? The rubber ones on AndyMark have a rating of 65A.

Re: Curved Shooter help