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Unread 15-01-2013, 20:13
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Team 3081 - RoboEagles Prototype Launcher

Team 3081 Prototype Launcher - Final

Hello Chiefdelphi, this is a semi in-depth report on shooting frisbees. We have spent the last week prototyping shooters and I aim to report what we found here.

Selection of wheel - We prototyped with two wheels, one being the AM Pneumatic wheel and the second being the AM 8" 2010 wheel. We attached these directly to the CIM motors using AM hubs creating a 1:1 drive. We modified the speed of the wheels using a Jaguar controlled by a C++ program.

AM 8" 2010 Wheel - We initially started testing with this wheel because it was the only one we had on site. While it worked well it simply was not accurate enough for our liking. We used multiple different types of material on this wheel during our testing, from friction tape to plaction. For range plaction worked best in this application.

AM Pneumatic Wheel - In the end we chose to go with the AM Pneumatic Wheel because it was much more accurate then the AM 8" 2010 Wheel. My personal speculation is this is caused by the tread on the wheels.

Tread
The Pneumatic wheel has tread go farther around the wheel while the AM 8" 2010 Wheel only has tread straight out from the wheel. We used this fact to our advantage, instead of putting the frisbee linear with the wheel we actually placed the frisbee under the wheel. You can see it in action in the above picture. When we placed the frisbee under the wheel not only did we launch farther and faster but we were also more accurate.
PSI of the wheel
We tested two levels of PSI, 15 PSI and after filling it, letting as much air out as we could. We will call the second level 0 PSI. The first level shot the frisbee pretty far, at 70% speed we could hit the 3 pointer from ~30 feet away. Unfortunately it was highly inaccurate, making only 4 shots out of 24. Next we tested the second level (0 psi) we noticed a small decrease in range of the shooter at this point so we increased our test speed to 80%. After shooting another 24 shots and making 18/24 we decided this was the design we would go for.

The below tests are all results with the AM 8" Pneumatic wheel. The wheel is not perfectly beaded.

Compression
We did not test many different types of compression but the entry compression is less then the exit compression.

Exit compression:


Entry compression:


Saw blade

Why is there a saw blade on top of our wheel? It takes awhile to take the saw blade on and off so for all of the above results the saw blade remained on our wheel. The sharp edges were grinded(ground?) off before the saw blade was attached and it adds a lot of mass to the wheel. Initially the saw blade was attached on the underside of the wheel but we found it was not as effective as it being on top. The wheel has a lot of momentum because of the extra mass, it takes a lot longer for it to slow down and speed up.

Velocity
We measured velocity over about 18 tests using limit switches and an Arduino board. The average velocity was 17.62 feet per second.

CIM voltage/current?
We did not measure either.

Guiderail
During our initial testing we found adding a small guiderail to the arc of our shooter increased our accuracy and shooting distance. It is just some C-channel we bent to fit in our arc.

The Arc
We found that a 90 degree arc works just as well as a 180 degree arc in our prototype.

I most likely forgot to include something in this report so please ask questions if you have any.

I do not have a video at the moment but I hope to upload one later tonight.

Evan
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Unread 15-01-2013, 23:13
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Re: Team 3081 - RoboEagles Prototype Launcher

How did you go about bending the c channel?
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Unread 15-01-2013, 23:29
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Re: Team 3081 - RoboEagles Prototype Launcher

Thanks for sharing your results. Well documented. A picture is worth a thousand words .
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Unread 16-01-2013, 00:16
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Re: Team 3081 - RoboEagles Prototype Launcher

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Originally Posted by huurrpaderp View Post
How did you go about bending the c channel?
You can see that they cut te bottom and welded it back together. But wouldn't that mean that they would have cut the top too?
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Unread 16-01-2013, 07:02
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Re: Team 3081 - RoboEagles Prototype Launcher

We used an alternative bending form where you cut two pieces of wood. one is shaped to the right size of arc. the other is a chunk that allows you to hit the inside of the c channel. then hammer away. There was a slight difference between the size of the bend and the actual arc. but the screws made it work out. If this is confusing please let me know I can get a video up tonight or tomorrow night showing how we did it.
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Unread 19-01-2013, 21:04
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Re: Team 3081 - RoboEagles Prototype Launcher

I finally had the time to compile and upload a video of the shooter today.

Check it out!

http://youtu.be/AAAl2DQggYE
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Unread 19-01-2013, 22:00
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Re: Team 3081 - RoboEagles Prototype Launcher

Thanks for all the info! Looks great!

Is the tread there for compression so you can "fine tune" your arc? sorta like a push/pull adjustment with the screws?
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Unread 20-01-2013, 21:29
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Re: Team 3081 - RoboEagles Prototype Launcher

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Originally Posted by lcoreyl View Post
Thanks for all the info! Looks great!

Is the tread there for compression so you can "fine tune" your arc? sorta like a push/pull adjustment with the screws?
Kind of, when we were cutting the angle we forgot to take in account the size of the router bit. So out arc was a fraction of an inch too wide. This was just what was lying around when we were fixing it.
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Unread 22-01-2013, 21:57
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Re: Team 3081 - RoboEagles Prototype Launcher

Has anyone tried using a shooter with bane bots rather than CIMs?
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Unread 23-01-2013, 22:44
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Re: Team 3081 - RoboEagles Prototype Launcher

Quote:
Originally Posted by flamer075 View Post
Has anyone tried using a shooter with bane bots rather than CIMs?
We have not tested with bane bot motors. I could give some speculation to how they would work if asked but it wouldn't take my speculation for much.

*Launcher Update*

We did some additional testing this week and found that in order to get more distance, height and accuracy with this specific launcher it is required to have the extra mass on top. The mass allows for additional momentum from the wheel (think f=ma) and causes less motion loss when launching the frisbee due to compression. The frisbees we launched without the saw blade on top traveled aprox. 3/4 the distance of the frisbees with the saw blade attached.

Safety Warning I highly recommend anyone attempting this grind the blades off of the saw, add warning signs and tape the edge of the blade with safety tape. We made a very large cut in one of our tables.
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Unread 23-01-2013, 23:20
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Re: Team 3081 - RoboEagles Prototype Launcher

Quote:
Originally Posted by flamer075 View Post
Has anyone tried using a shooter with bane bots rather than CIMs?
Our team tried direct driving a Banebot with the 6" KOP wheel. At an incline between 20-30 degrees we got about 15 ft of distance.
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Unread 24-01-2013, 14:32
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Re: Team 3081 - RoboEagles Prototype Launcher

My team has already found use for all 6 CIMs so we were going to prototype our shooters using the bane bot motors. Has anyone tried prototyping a linear two wheeled shooter with it and what were the results?
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Unread 24-01-2013, 14:40
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Re: Team 3081 - RoboEagles Prototype Launcher

Quote:
Originally Posted by Negative 9 View Post
Our team tried direct driving a Banebot with the 6" KOP wheel. At an incline between 20-30 degrees we got about 15 ft of distance.
There are a large number of banebot motors. Could you be more specific on which banebot motor you direct drove?
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Unread 25-01-2013, 21:44
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Re: Team 3081 - RoboEagles Prototype Launcher

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Originally Posted by Tom Line View Post
There are a large number of banebot motors. Could you be more specific on which banebot motor you direct drove?
My apologies. We were using an RS-775.
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