Re: Frisbee shooter
 

our offseason is this saturday, maybe we could ask for pneumatic wheels to a team close to us.
we are going to try changing the fence from acrylic to wood

Re: Frisbee shooter
 

We had marginal success with a radiused shooter using similar speeds in the spring, but decided to attempt to recreate team 67's incredible shooter as an offseason development exercise for our new builders. The results were incredible. While it is obviously not the only way to do the job...it works.

Whatever you end up with - don't overlook compression of the discs...that was the biggest factor affecting the performance of our radiused shooter - but it was very difficult to adjust the compression in that configuration...in a linear shooter it's just a matter of moving the fence.

https://vimeo.com/75662715

Re: Frisbee shooter
 

I don't know what your team's situation is at the moment, but given your 2013 record (I checked The Blue Alliance) and the way you phrased your question, your team is in no to be creating a shooter.

I regret that I didn't discover this thread until today, else I would have tried to dissuade you a week earlier and saved you a week of wasted time. The other respondents to this thread have given excellent advice on creating a solid shooter, but that advice is the result of thousands of hours of cumulative experience and practice. Obviously, each individual shooter will be unique, and will need its own tuning. Your team does not have the time or experience to be able to make a consistent shooter by Saturday; the fact that you are posting today to say that you don't have a functional shooter yet only confirms my suspicions.

Your team should abandon all work on the shooter and focus on what is actually important for your robot: drivetrain and driver practice. It has been said for years, for very good reason, that a good driver on a terrible robot will consistently outperform a poor driver on a world-class robot. If you focus on training your driver, on a properly working drivetrain, for the next few days, your team has a chance of making a positive impact on your elimination alliance. If, on the other hand, you continue to work on your shooter, you will fail at both shooting and driving.

Of course, it's possible that your team cares more about creating a shooter as an engineering exercise than for competitive reasons. Even so, I, as a student in my third year of FRC, personally believe that engineering a good drivetrain is easily the most important part of creating a robot, and is by no means simple or easy.

I'm sorry if I punctured your bubble of happiness. If I could have done it sooner, I would have. In all honesty, I'm surprised no one else brought this up sooner.

Re: Frisbee shooter
 

Team 1986 shooter: 2 stage
1st stage - CIM direct drive, 2008 KOP wheel (6" w/ solid rubber tread), 50 degree arc of contact against bare solid wooden fence, 1/8" of compression.
2nd Stage - Mini-CIM direct drive, 2008 KOP wheel, straight path against bare aluminum fence, 1/8" of compression. Approx. 6" of close 3-sided guiding after the final wheel.

Re: Frisbee shooter
 

In our first iteration of our shooter we had a bare polycarbonate side wall supported by aluminum. Our initial results were less than satisfactory (only a few meters). We added a tacky material to the side wall and the results were astounding. We were shooting a few meters before and with the added sidewall material we could shoot full court.

Re: Frisbee shooter
 

As a counterargument, our two wheeled linear shooter had plenty of shot consistency with a smooth polycarbonate wall on the opposite side. Our shooter was far from an optimized solution, but if you're trying to build a simple cycler, you don't need a perfectly optimized solution. You just need a consistent and effective solution.

Here's our shooter specs, if it helps you:
- Two Banebots 4 7/8" wheels plugged into two mini cims or a cim + mini-cim (honestly doesn't matter) using the AndyMark 8mm to hex adapters
- 10.5" between the tips of the wheels and the opposite wall of the shooter (so .5" disc compression)
- Polycarbonate on the opposite side of the shooter. I've heard from MANY teams that wedgetop tread or other grippy material works well, so consider that an option too, but you might not need it.
- Plastic strips above and / or below the shooter barrel such that frisbees sliding through are physically constrained in the shooter. Basically what this does is it forces the frisbee to contact both wheels rather than lifting up between the wheels and not getting full contact. This dramatically improves vertical consistency.

We used an aimable shooter so I can't tell you if this consistently fires the exact same height over 1,000 shots, but if everything was working all 4 discs would hit almost the exact same place every cycle. This definitely isn't the best way to build a shooter, but "done" is better than "perfect".

Re: Frisbee shooter
 

Perhaps your larger-than-normal compression mitigated to some extent the sliding due to the polycarb fence.

Re: Frisbee shooter
 

That's possible, certainly. I was under the impression that .5 inch compression is standard for linear shooters. 1/4-1/2 turn shooters use less.

Looking at markings left on the frisbee by the wheel, the length corresponds to the contact patch of the frisbee on the wheel if it was being "rolled" through the shooter. A slippery system would have a shorter contact patch as pressure would be applied to the same spot for longer.

Re: Frisbee shooter
 

Our linear shooter also had .5in of compression. Three 1:1 Bag motors with 2 7/8in banebots wheels and wedgetop tread on the opposite side.

Re: Frisbee shooter
 

We evaluated multiple designs early, and ended up with a single wheel, 8" pneumatic, lineral shooter design. Our strategy was to shoot from back of pyramid, unblockable to the 3 point. We were a tall bot, and when we were too tall to be agile, we morphed into a full court shooter. We never had a reason to redesign the shooter to shoot 2's, shooting 3's we needed a little more power to get our accuracy above 80% shooting 3's.

We had very accurate and active speed control on the wheel, are you missing that?

http://www.mcbride4.org/?attachment_id=82

https://www.facebook.com/photo.php?v...type=3&theater

Re: Frisbee shooter
 

My team used a linear design, but the properties are the same for both linear and circular designs. The key is to have as much grip/friction on the wheel and the other plate the frisbee is riding on. With these two points of contact, the frisbee will get a good spin=longer distance and higher rise. Another main thing that you will want to focus on is the compression. The compression determines the friction between the two points of contact on the frisbee. My team never got our compression perfect, but after some trial and error, you will get it right. One last key is to have the frisbee travel through the shooter will little to no friction, this is to keep the spin and speed constant throughout the shot for an accurate ending location (use a material like delrin).

Re: Frisbee shooter
 

Finally we shoot as we wanted, we use the mini CIM and the CIM, and the wheels 6" diameter. we change the wall with wood.
We try to power the wheels at different speeds, the first motor (mini CIM) has a regulate speed and then the CIM the maximum speed.
We almost reach 110" hight at 6 mts distance.

Re: Frisbee shooter
 

How are you going to feed the shooter?

(Hawaiian Kidsth post!)

Re: Frisbee shooter
 

Very similar to our shooter however our CIMs are switched, with the full CIM first then the mini-CIM. The mini RPM is 20% higher the the CIM, so it naturally runs faster with both running full speed. Works wondefully for us.

Re: Frisbee shooter
 

This! flip the motors and run both on full, you might need to turn the speed down a bit if there's too much slippage the wheels will just do burnouts on the disk.

The wood probably added some much needed support. Shooter really need to be rigid, or the force will transfer to the robot instead of the frisbee.

In our 90 degree shooter(different beast), we found that using double sided tape with different thickness sheet metal/polycarb/traction material was an excellent way to tweak the compression/friction to see what gives the best the distance/accuracy.