3 Wheel 3 CIM shooter

[nathannfm]

No more mannequins, 3929 is getting serious, here is our new crossfield shooter prototype.

http://www.youtube.com/watch?v=2QNnHawyM00

We finished right before clean up today so we will be taking down stats on it tomorrow, enjoy.

[Gregor]

Yay for 3 CIM drivetrains. :rolleyes:

Seriously, impressive distance.

[ENeyman]

Yay for 3 CIM drivetrains. :rolleyes:

Seriously, impressive distance.

Well, two of the "CIMs" are really mini-CIMs.

[LeelandS]

Wow! That's very impressive. What size and kind of wheels are you guys using, and are they directly mounted to the wheels? Those motors looks pretty closely spaced together.

[Akash Rastogi]

Conveniently not mentioned: This is being run off 1 battery per CIM.

Hopefully the team will figure out a more realistic way of making their goal of a full field shot happening this week and finalize things. Crunch time doesn't leave room for too much iteration.

-Akash

[Garrett.d.w]

If you still want four CIMs on your drivetrain you could put a 775 as one of your stages. You can gear it down to match the CIM's rpm using a CIMulator gearbox.

This is really cool by the way :)

[nathannfm]

If you still want four CIMs on your drivetrain you could put a 775 as one of your stages. You can gear it down to match the CIM's rpm using a CIMulator gearbox.

This is really cool by the way :)

Thanks!

As previously stated only one of those is a full sized CIM so our drive is fine (unless we have power draw problems, but I don't think we will be driving and shooting at the same time)
(the Mini CIM is my favorite thing about VEX Pro)
We did get a CIMulator and 2 550s with our BaneBot voucher, should come in handy even if not this year.

We are somewhat happy that we can get away with not using gearboxes and just go with something like this http://www.andymark.com/product-p/am-0588.htm

[dtengineering]

Even though you are using CIMs and mini-CIMs to shoot, I suspect their current draw is very low relative to your drivetrain.

I agree that you likely won't be driving and shooting at the same time, but I wouldn't about massive current draw being a problem, even if you were doing both.

Jason

[daniel_dsouza]

Darn, 3 motors in a mechanism and no Frisbee shards.

Anyone built anything where you put in frisbees and (unintentionally) shoot out shards?

[nathannfm]

Anyone built anything where you put in frisbees and (unintentionally) shoot out shards?

As fun as that sounds I don't think you will be finding any of that...
http://www.chiefdelphi.com/forums/showpost.php?p=1212245&postcount=39

[Akash Rastogi]

Darn, 3 motors in a mechanism and no Frisbee shards.

Anyone built anything where you put in frisbees and (unintentionally) shoot out shards?

Breaking frisbees is probably mostly from wheels that don't conform to the contours of the frisbee or there is too much compression. I think the setups our students made are pretty safe as the wheels are relatively squishy.

Either way, we'll cross our fingers and hope no students "shoot their eye out." :)

[ENeyman]

Wow! That's very impressive. What size and kind of wheels are you guys using, and are they directly mounted to the wheels? Those motors looks pretty closely spaced together.

The wheels are 4 7/8 in. Banebots wheels. The first one is driven directly by a CIM and the next two are directly driven off of mini-CIMs.

[ENeyman]

Here is a video from today of all three motors being run off of one battery. While the distance isn't quite as impressive as yesterday's, we are still quite pleased.

http://www.youtube.com/watch?v=xcHiwdZuMKM

[Jeffy]

Here is a video from today of all three motors being run off of one battery. While the distance isn't quite as impressive as yesterday's, we are still quite pleased.

http://www.youtube.com/watch?v=xcHiwdZuMKM

In this video, you will notice the Frisbee flies out of the shooter at an angle. I have seen this happening in videos, but it wasn't noticeable in our prototype. While it may not be an issue for most, it can make scoring a bit tougher.

When you find a way to solve the issue (which I think you will), I'm sure I wouldn't be the only one eagerly awaiting to know what causes the "off angle" exits of Frisbee. Much appreciated if you don't mind.

[nathannfm]

Here is a video from today of all three motors being run off of one battery. While the distance isn't quite as impressive as yesterday's, we are still quite pleased.

http://www.youtube.com/watch?v=xcHiwdZuMKM

Note that yesterday we were shooting at a 22 degree angle and today a 0 degree angle, we tried to go up to 10 degrees but hit the first light on the ceiling there.

Also, I have a feeling the curve may be due to the change in position/ compression of the opposite rail because the one we had on yesterday was coming off. As well as the change in possession of the bar that keeps them from riding up.
So many variables! :confused:

[ENeyman]

In this video, you will notice the Frisbee flies out of the shooter at an angle. I have seen this happening in videos, but it wasn't noticeable in our prototype. While it may not be an issue for most, it can make scoring a bit tougher.

When you find a way to solve the issue (which I think you will), I'm sure I wouldn't be the only one eagerly awaiting to know what causes the "off angle" exits of Frisbee. Much appreciated if you don't mind.

I believe the spin comes from only one side of the disc being spun. Because the force is exerted on the right side of the disc, the frisbee will curve slightly to the left. That's just my theory.

[theawesome1730]

And I thought 2 miniCIMs for a shooter was crazy. I look forward to seeing this launch some disks!

[Chris is me]

Have you guys directly compared this to a 2 wheel, 2 minicim shooter? I am really curious how much more distance and repeatability you get.

[Jeffy]

I believe the spin comes from only one side of the disc being spun. Because the force is exerted on the right side of the disc, the frisbee will curve slightly to the left. That's just my theory.

I actually intended to describe the frisbee coming out of the shooter not level with the base. The curve is a direct result of an un-level frisbee.

I thought about it further and think it may be a function of the stored energy in the pneumatic wheel compression. The compression coupled with the wheel deforming to "cup" the frisbee gives a reaction where the frisbee comes out non-level with the launch base.

[Ether]

I actually intended to describe the frisbee coming out of the shooter not level with the base. The curve is a direct result of an un-level frisbee.

I recall seeing another thread a while back where a team had a similar issue and found the cause: the frisbee was slightly climbing up the wall of the guiderail -- it was not staying flat on the base. Can you take some video with a camera angle looking "down the barrel of the gun" - you might be able to see this effect.

If that's what's happening in your case, you might be able to solve it by tilting the guiderail slightly toward the frisbee, or adding a piece to keep the frisbee from climbing the guiderail.

[Lil' Lavery]

Have you given much thought to incrimentally increasing the speed of each subsequent wheel?

In other words, why directly drive all three wheels? A lot of teams have shown significant success with (relatively) lower speeds on the first wheel the disc comes in contact with. Additionally, it should (theoretically) increase your throughput (and potentially overall efficiency), as the first wheel will lose less energy and thus return to effective speed quicker.

[TheCrayButton]

WOW! Very impressive you guys. That is getting some distance. Do you all plan to shoot full court?!

[nathannfm]

Have you guys directly compared this to a 2 wheel, 2 minicim shooter? I am really curious how much more distance and repeatability you get.

The day before we had CIM > Mini > wall and it was hitting 9 feet up at about 40 feet away, this is at least double that with the extra mini


Have you given much thought to incrimentally increasing the speed of each subsequent wheel?


This is doing that to an extent as the first wheel it contacts is going 5,300 RPM and the next 2 are going 6,200, We enjoy not having to worry about chain or gearboxes and seeing as we are getting more than full court shots (with amazing accuracy, hitting the same cinder block on the wall 3 times in a row from 70 feet) this is the design we are going to go with.


WOW! Very impressive you guys. That is getting some distance. Do you all plan to shoot full court?!

Thanks! It looks like that's the plan after today's tests, you will see one of them in our Vlog this week, I think they forgot what years game they were playing if you know what I mean ;)

[Racer26]

This is doing that to an extent as the first wheel it contacts is going 5,300 RPM and the next 2 are going 6,200, We enjoy not having to worry about chain or gearboxes and seeing as we are getting more than full court shots (with amazing accuracy, hitting the same cinder block on the wall 3 times in a row from 70 feet) this is the design we are going to go with.



You know you don't *have* to do this with gearing, right? Those motors are on speed controllers, so you can simply experiment with the speed values you send them once you have a proper control system in place. Many teams have reported great success with 2xCIM linear shooters, direct drive to the wheels, with the first one set about 60% speed.

[Chris is me]

The day before we had CIM > Mini > wall and it was hitting 9 feet up at about 40 feet away, this is at least double that with the extra mini

Good to know. We tried mini -> mini a while back and got results that were good enough to move forward. I'll see if I can't leave space in the design for a third motor just in case we end up feeding or something.