View Full Version : Linear Path Shooter vs. Circular Path Shooter?
skottmorris
07-01-2013, 17:12
Has anyone considered a linear path shooter for their design?
Everything I've seen on YouTube is built with a circular path. I'm curious if this was for design convenience or there is some magic to the disc following a circular path. My team has proposed creating a linear path shooter with two parallel motors to "spin" the disc down the launch path. Has anyone tried this? If it works, it would make a nice compact shooter.
Has anyone considered a linear path shooter for their design?
Everything I've seen on YouTube is built with a circular path. I'm curious if this was for design convenience or there is some magic to the disc following a circular path. My team has proposed creating a linear path shooter with two parallel motors to "spin" the disc down the launch path. Has anyone tried this? If it works, it would make a nice compact shooter.
http://www.youtube.com/watch?v=GT88vWTYgj0
http://www.youtube.com/watch?v=iyE4Ir6dkY8
Christopher149
07-01-2013, 17:22
Beaten to the punch, but:
http://www.youtube.com/user/robotin3days
in particular
http://www.youtube.com/watch?v=iyE4Ir6dkY8&list=UUgtwgUTTxuldvAGW1u8SDSA&index=2
Tom Line
07-01-2013, 21:37
A circular path shooter allows more distance while the disc is in contact with your shooter wheel. This will allow the disc to speed up to more closely match your shooter wheel speed. That isn't necessarily good or bad. Last year it was important because you needed very consistent speed and spin.
This year, I'm guessing not so much.
F22Rapture
08-01-2013, 00:11
A linear shooter seems, from all that I've seen, much easier to deal with. Easier to load, easier to fit, and potentially easier to manufacture (you've got to get that curve just right, and keep it that way).
This comes at the expense of being slightly less accurate and slightly less powerful. Our team hasn't made it that far into the prototyping stage yet, so I can only speak from what I've seen others do.
As has been said, its a matter of contact speed.
The circular pathway allows more contact time between your spinning wheel and the frisbee. This gives the wheel more time to accelerate the frisbee to more closely match its own tangential velocity.
In a linear pathway, the wheel touches the frisbee for a fraction of a second; thus, a fraction of the speed of the wheel is delivered to the frisbee.
Of course, there's dark magic with various other variables such as the compression of the frisbee, space between wheel and a guide rail, type of wheel, surface area of wheel, as well as the torque and speed of the accompanying motor.
It's a matter of testing :)
What says the linear shooter only touches the frisbee at the tangential point of the wheel? I can think of a way to have the frisbee in contact with the mechanism for a longer period of time.
What says the linear shooter only touches the frisbee at the tangential point of the wheel? I can think of a way to have the frisbee in contact with the mechanism for a longer period of time.
Please elaborate?
Tem1514 Mentor
08-01-2013, 06:03
Please elaborate?
A linear pathway with a belt along the length to give the spin and forward speed might just do it.
A linear pathway with a belt along the length to give the spin and forward speed might just do it.
So you're going to run a linear belt, essentially a conveyor on it's side, at thousands of rpm and expect that to work the same as a wheel going thousands of rpm?
Robogineer1649
08-01-2013, 07:59
We built a prototype and it had two parallel wheels as you were saying you might try. I must add that it was in a linear fashion. But what i really want to tell you is that the frisbees go much further if one side is stationary compared to both sides spinning. Additionally our team has not tried to make a half circle shooter design only a linear so i can not take about that aspect of your question. What i can ask you is why would you use a half circle shooter that takes up much more space especially this year with smaller robots rather then building a linear shooter that works just as well?
knuckleduster
08-01-2013, 08:20
In our tests in the shop we have found that linear shooters are not as accurate as circular shooters and don't shoot as far. I hypothesise that it is because the wheel doesn't get to work on the disk as much (W=FxD) and will therefore put less energy into the disk before it is released.
Here are videos of our attempts:
http://telly.com/01F3LB
they should all be on there.
Jared Russell
08-01-2013, 08:21
So you're going to run a linear belt, essentially a conveyor on it's side, at thousands of rpm and expect that to work the same as a wheel going thousands of rpm?
Theoretically there is no difference. For a given contact length, CoF, compression, and surface speed, and a given energy supply (including any storage of rotational energy via flywheel effect) the shape of the pathway is irrelevant.
Theoretically.
You are not limited to one wheel with a linear shooter design. Watch the videos posted here (http://www.chiefdelphi.com/forums/showpost.php?p=1210105&postcount=2).
Tem1514 Mentor
08-01-2013, 09:48
So you're going to run a linear belt, essentially a conveyor on it's side, at thousands of rpm and expect that to work the same as a wheel going thousands of rpm?
I am not saying that a belt is the best way, rather just pointing out that it is a method that would work or maybe I should say, should work.
A multi ribbed flat belt will run at 3600 rpm with no problem at all on a 4 inch diameter wheel which translate to a very fast linear speed.
A multi ribbed flat belt will run at 3600 rpm with no problem at all on a 4 inch diameter wheel which translate to a very fast linear speed.
It translates into approx 21 mph, assuming no slipping.
3600 rpm / 60 min/sec = 60 rev/sec
60 rev/sec * pi*4/12 ft/rev = 62.8 ft/sec
62.8 ft/sec / 2 = 31.4 ft/sec
31.4 ft/sec * 3600 sec/hour / 5280 ft/mile = 21.4 mph
Jon Stratis
08-01-2013, 10:14
In Lunacy we ran timing belts instead of wheels in our shooter, in an attempt to compensate for the holes in the orbit balls. The belts were driven with only a small gear reduction from a CIM motor, and we never, at any point in the season, had an issue with them. They never came off, never wandered, no issues at all. A lot of design and work went into building a stable, adjustable system that would allow us to ensure everything was perfectly parallel, and using belts with teeth in them also helped.
I'm not saying I recommend going this path, but it certainly is possible to get your belts up to speed and keep them there without any issues.
Tem1514 Mentor
08-01-2013, 10:31
[/I]
Ether. That 31.4 ft/sec sounds like it might do the job. I wonder what a CIM motor at full speed with a direct drive 6 inch wheel would be? Just don't have the CIM specs handy.
MyNameIsPaul
08-01-2013, 10:32
A circular shooter gives the Frisbee spin and more accuracy
DjScribbles
08-01-2013, 10:34
What i can ask you is why would you use a half circle shooter that takes up much more space especially this year with smaller robots rather then building a linear shooter that works just as well?
It can be argued that 1 circular shooter may use less space than 2 parallel shooters, if you are trying to minimize the length of the shooter, and width doesn't matter.
Ether. That 31.4 ft/sec sounds like it might do the job. I wonder what a CIM motor at full speed with a direct drive 6 inch wheel would be? Just don't have the CIM specs handy.
CIM free speed is 5310 rpm. But you don't want to drive your shooter wheel at free speed. You need some headroom to accelerate back to the setpoint after a frisbee passes through.
A circular shooter gives the Frisbee spin
so does a linear shooter
... and more accuracy
What is your source for this statement?
billbo911
08-01-2013, 11:27
You can see from some of our testing video (Thanks Kevin!) that we have tried a couple of different approaches. Granted, some of the tests aren't as valid because the mechanical setup's were a bit shoddy.
When you get to the 90 deg. circular shooter, you can notice some issues with the stability of the wall. We will be working on that tonight.
One really important take away from this testing is that increased RPM of the shooing wheel did not always translate to further distance. This is because the slipping that is occurring between the wheel and the Frisbee. Again, this is something we will be addressing tonight.
BTW, High Speed Video Capture (HSVC) is rapidly becoming one of our favorite new prototyping tools.
This is in Std. Res.
http://www.youtube.com/watch?v=p5bLi2z60gE&feature=youtu.be
This one is in 1080.
http://www.youtube.com/watch?v=Wa6pcoB90Bc&feature=youtu.be
ayeckley
08-01-2013, 11:47
Some of the confusion/disagreement/misunderstanding/whatever seems to be because folks are unintentionally discussing different implementations of the linear shooter. The major sub-categories would seem to be "single drive side" vs. "double side drive" and "nip point contact" vs. "continuous contact". So far I've mostly seen videos of "single side drive, nip point contact". I haven't seen any videos of teams prototyping a "single drive side, continuous contact" design...yet.
rcmolloy
08-01-2013, 11:50
Has anyone considered a linear path shooter for their design?
Everything I've seen on YouTube is built with a circular path. I'm curious if this was for design convenience or there is some magic to the disc following a circular path. My team has proposed creating a linear path shooter with two parallel motors to "spin" the disc down the launch path. Has anyone tried this? If it works, it would make a nice compact shooter.
Why not just quickly test both? You're going to have some discrepancies between the performance of the two anyway. Also, you might be using different materials than other teams and the such. Grab a bunch of wheels and have at it. You guys might also develop another idea just from doing that!
Good luck!
I stand corrected on the belting. I misunderstood what was meant by belting; I was imagining that the belting in question was polycord or some other cord variant.
Some of the confusion/disagreement/misunderstanding/whatever seems to be because folks are unintentionally discussing different implementations of the linear shooter. The major sub-categories would seem to be "single drive side" vs. "double side drive" and "nip point contact" vs. "continuous contact". So far I've mostly seen videos of "single side drive, nip point contact". I haven't seen any videos of teams prototyping a "single drive side, continuous contact" design...yet.
"NIP point contact"? Can you elaborate on to what this means?
It can be argued that 1 circular shooter may use less space than 2 parallel shooters, if you are trying to minimize the length of the shooter, and width doesn't matter.This depends largely on wheel diameter. If you can achieve the linear velocity and contact time you're seeking using wheel diameter < the disc, even a dual linear can be shorter (final shot axis) than a 90deg turn.
RSaunders
08-01-2013, 12:25
One consideration for the circular vs linear shooter is how the Frisbee is released. The circular shooters I've seen in videos have a very gentle release, the outer wall very gradually moves away from the wheel until the gap is larger than the Frisbee. This means that small variations in Frisbee geometry, perhaps from prior rough handling, give slightly different release points. The theory seems to be that the Frisbee is "up to speed" well before the release point and so the exact point where it loses wheel contact doesn't matter.
The linear shooter used by the robotin3days folks uses a compliant wheel to hit the Frisbee with a pulse of energy. Given the speed involved, it it a very quick, violent, pulse. Ignoring the risk of Frisbee damage, there is no way to do that without adding some flex to the Frisbee and corresponding random velocity. I'm not at all worried that belts can't take the speed or forces required, just Google "serpentine belt" and see how they are used in cars.
Replacing the two wheels with two wheels connected by a belt, or 5 wheels and a belt if you want to go all-tank style, could mean you don't have to pinch the Frisbee as hard because you have more distance (= time) to add energy to it. It sounds like this could be better, but convincing experimental measurement of the magnitude of the effect is what we're lacking in this discussion.
"NIP point contact"? Can you elaborate on to what this means?
My understanding of this is that he means the very short contact time and small contact area that a wheel and a linear wall creates compared to a curved wall and a wheel.
AdamHeard
08-01-2013, 12:59
When making prototypes, keep in mind there are more variables than just linear versus curved.
Our linear prototype currently worked AWESOME, and our curved is merely pretty darn good.
We're smart enough to realize we haven't proved anything yet, and need to explore more.
My understanding of this is that he means the very short contact time and small contact area that a wheel and a linear wall creates compared to a curved wall and a wheel.
Oh.
Related Physics Question:
Take 2 different sized wheels with the same material making the outer edge.
Wouldn't the bigger wheel cause the frisbee to exit the shooter faster due to faster tangential velocity on the wheel?
Related Physics Question:
Take 2 different sized wheels with the same material making the outer edge.
Wouldn't the bigger wheel cause the frisbee to exit the shooter faster due to faster tangential velocity on the wheel?
http://www.chiefdelphi.com/forums/showpost.php?p=1210612&postcount=16
It translates into approx 21 mph, assuming no slipping.
3600 rpm / 60 min/sec = 60 rev/sec
60 rev/sec * pi*4/12 ft/rev = 62.8 ft/sec
62.8 ft/sec / 2 = 31.4 ft/sec
31.4 ft/sec * 3600 sec/hour / 5280 ft/mile = 21.4 mph
Why did you only multiply by pi and not by 2pi? Also why did you divide by 2?
(I might just be missing something but I thought linear velocity was Angular Velocity(in radians) * r?
http://www.chiefdelphi.com/forums/showpost.php?p=1210612&postcount=16
Also, I understand that linear velocity at the edge of the wheel increases with a bigger wheel. I was unsure about whether that entire increase would still go into the frisbee
Why did you only multiply by pi and not by 2pi?
because the wheel circumference is equal to pi times the diameter
Also why did you divide by 2?
because the speed of the exiting frisbee is theoretically half the speed imparted to the frisbee's circumference (assuming, as stated in the post, that there is no slipping, i.e. the frisbee is rolling along the non-motorized edge)
(I might just be missing something but I thought linear velocity was Angular Velocity(in radians) * r?
That's correct. Punch the numbers and you'll get the same answer.
Also, I understand that linear velocity at the edge of the wheel increases with a bigger wheel. I was unsure about whether that entire increase would still go into the frisbee
The faster the tangential velocity, the more likely that the explicitly stated "no slipping" assumption won't be entirely accurate.
The faster the tangential velocity, the more likely that the explicitly stated "no slipping" assumption won't be entirely accurate.
So in other words, a bigger wheel "might" speed up the frisbee's exit velocity?
Dr Theta
08-01-2013, 22:44
So in other words, a bigger wheel "might" speed up the frisbee's exit velocity?
And that is why you prototype ;)
And that is why you prototype ;)
Exactly what I'm working on tomorrow :) Reason I was asking these questions was so that I could have some direction in the modifications I make to my prototype, but oh well :P
So in other words, a bigger wheel "might" speed up the frisbee's exit velocity?
It's highly likely, everything else being equal*.
* same wheel speed, same compression, same wheel material, etc etc
billbo911
08-01-2013, 23:53
When making prototypes, keep in mind there are more variables than just linear versus curved.
Our linear prototype currently worked AWESOME, and our curved is merely pretty darn good.
We're smart enough to realize we haven't proved anything yet, and need to explore more.
As Adam stated, there are many variables that need to be identified and worked out before any designs are made. The following video and the one posted yesterday are proof that prototyping works.
The four things that changed between yesterday and today are:
Larger wheel (6in to 8in).
Different tread to reduce slippage.
Much more solid backing to the wall.
Added traction tape to the wall to stop slipping.
The result is, we can run the wheel at a lower RPM and get much longer and repeatable flights. This will allow us to also have more headroom in the drive for faster spin up and shorter recovery time.
Can anyone say "Bang Bang" Speed Control"?:yikes:
Yesterday's
http://www.youtube.com/watch?v=Wa6pcoB90Bc&feature=youtu.be
Today's
http://www.youtube.com/watch?v=_iqd_oA-Y4o&feature=youtu.be
NIce video but w a y to m u c h s l o w m o
billbo911
09-01-2013, 00:50
NIce video but w a y to m u c h s l o w m o
I'll pass that on to the editor.
But remember, we are using these for analyzing a prototype, not for entertainment. :)
I'll pass that on to the editor.
But remember, we are using these for analyzing a prototype, not for entertainment. :)
They are very useful. But a bit long to get through :P
ttldomination
09-01-2013, 01:10
Different tread to reduce slippage.
Are you guys using roughtop here? If so, I don't think it'll actually reduce it, but it's just not audible anymore.
- Sunny G.
DampRobot
09-01-2013, 03:16
In regards to Ether's numbers, at those high speeds, don't trust that you'll get anywhere near no slippage. We ran our belts at a surface speed of about 60 miles per your last year, and it was an unmitigated disaster. Tons of slippage and lack of any speed sensing (or even compensation for voltage changes) led to a shooter that was completely inaccurate. Our two CIM shooter (given, at a large angle) could barely get shots for the key.
When you're designing a shooter, think about what your numbers say and what your testing demonstrates. I really appreciate 2073's testing, especially their result that indicates that lower speeds mean more consistency. But remember, what works for their team (or my team, or robot in three days, or anyone else) may not work for yours. We're prototyping using pneumatic wheels, and have had a lot more success with the straight shooter, for example.
billbo911
09-01-2013, 09:41
Are you guys using roughtop here? If so, I don't think it'll actually reduce it, but it's just not audible anymore.
- Sunny G.
Yes, it's roughtop.
The audible indication of slippage is definitely reduced, no screeching at all.
Whether it is because of the compliance of the tread is gripping the Frisbee better or because it's dampening the sound out isn't really clear.
We can tell by a couple sections of the video that the slipping appears to be greatly reduced. That is part of why we added the mark on the small piece of pool noodle on the hub.
With the hard tread, we were actually transferring material from the Frisbee to the tread. The tread was becoming whiter with every pass. With the roughtop, we saw no transfer to the tread, and the tread has shown no signs of wear....yet.
Bob Steele
09-01-2013, 10:38
As Adam stated, there are many variables that need to be identified and worked out before any designs are made. The following video and the one posted yesterday are proof that prototyping works.
The three things that changed between yesterday and today are:
Larger wheel (6in to 8in).
Different tread to reduce slippage.
Much more solid backing to the wall.
The result is, we can run the wheel at a lower RPM and get much longer and repeatable flights. This will allow us to also have more headroom in the drive for faster spin up and shorter recovery time.
Can anyone say "Bang Bang" Speed Control"?:yikes:
Yesterday's
http://www.youtube.com/watch?v=Wa6pc...ature=youtu.be
Today's
http://www.youtube.com/watch?v=_iqd_oA-Y4o&feature=youtu.be
Did you also add something to the wall on the inside? The black material? Or is it just plastic? It seems you are increasing the spin rate of the frisbee as it leaves. Nice job and many thanks for sharing!,,
billbo911
09-01-2013, 12:19
Did you also add something to the wall on the inside? The black material? Or is it just plastic? It seems you are increasing the spin rate of the frisbee as it leaves. Nice job and many thanks for sharing!,,
Ah, good catch Bob.
That is basically just traction tape, or anti-slip safety tape. It has a rough, rubberized surface, with a texture much like sprayed in truck bed liner. It is pliable enough to not mar the Frisbee's surface and prevents it from sliding on the polycarbonate. We had applied it the previous night, but it was applied after we had stopped recording.
I'll edit the post to include it as a change.
ayeckley
09-01-2013, 13:29
"NIP point contact"? Can you elaborate on to what this means?
Basically how Jeffy interpreted it. Some folks might call it a "pinch point". A place where the object (your finger, a frisbee, etc.) passing thru the mechanism would get deformed, rather than the path itself deforming to accomodate the object.
wireties
09-01-2013, 13:50
We built a prototype and it had two parallel wheels as you were saying you might try. I must add that it was in a linear fashion. But what i really want to tell you is that the frisbees go much further if one side is stationary compared to both sides spinning. Additionally our team has not tried to make a half circle shooter design only a linear so i can not take about that aspect of your question. What i can ask you is why would you use a half circle shooter that takes up much more space especially this year with smaller robots rather then building a linear shooter that works just as well?
Try spinning one wheel faster that the other to impart spin on the disc.
HTH
Justin m
09-01-2013, 14:27
Isn't it possible to have several wheels along a path, imparting speed and spin along a linear pathway? I apologize if this has been restating a previous post
vikesrock777
09-01-2013, 15:09
Isn't it possible to have several wheels along a path, imparting speed and spin along a linear pathway? I apologize if this has been restating a previous post
Yes, it certainly is possible. It can be seen in this prototype:
http://www.youtube.com/watch?v=GT88vWTYgj0&list=UUgtwgUTTxuldvAGW1u8SDSA&index=9
that was then utilized in this final design, illustrating moderate consistency and power:
http://www.youtube.com/watch?v=BfyzbV6k02A&list=UUgtwgUTTxuldvAGW1u8SDSA&index=1
billbo911
10-01-2013, 12:45
Here is a link to a bit more video from last night.
http://youtu.be/gWvWDQKd-8k
It is a bit long, but I will try to summarize the details we took away from it.
1) The traction tape is preventing any slippage between the Frisbee and the outer wall.
2) As we increase the voltage to the motor, the exit velocity of the Frisbee increases until we get to around 10 vdc. At that point the exit velocity begins to slowly fall off. This, along with basic observation of the images confirms that the wheel is slipping on the disk.
3) We can comfortably shoot a Frisbee 45+ ft. at waist level. We also verified we can easily hit the top goal from the bottom of the Pyramid, and the Pyramid goal from the base of the Alliance wall.
4) A top plate will be needed at least around the wheel contact area and possibly along the wall contact area to allow inverted Frisbee's to be feed through. A single piece plate is also an option.
Even if we go with this current design, we feel we have a competitive solution. Although, we plan to try to improve on the findings in #2. Possible options include: a pneumatic wheel, over wrapping or replacing the tread with the same traction tape applied to the wall.
Feel free to watch the video when you have a few minutes. It is educational, and sometimes entertaining.
1) The traction tape is preventing any slippage between the Frisbee and the outer wall.
2) As we increase the voltage to the motor, the exit velocity of the Frisbee increases until we get to around 10 vdc. At that point the exit velocity begins to slowly fall off. This, along with basic observation of the images confirms that the wheel is slipping on the disk.
These are useful observations. Thanks for sharing them!
[edit] Just watched the video:
1) There's a lot of wobble in the shooter wheel. Is that due to the motor mounting, or the wheel itself?
2) One camera angle seemed to show the frisbee "climbing up" the curved chute as it was exiting.
billbo911
10-01-2013, 13:56
These are useful observations. Thanks for sharing them!
[edit] Just watched the video:
1) There's a lot of wobble in the shooter wheel. Is that due to the motor mounting, or the wheel itself?
2) One camera angle seemed to show the frisbee "climbing up" the curved chute as it was exiting.
The wheel is only attached to the motor shaft via a hub. The motor is mounted to a plywood sheet with a couple if screws and a stack of washers is used to fine tune the height of the wheel. This is not a really solid mounting method, thus it allows a small amount of wobble. Additionally, there is some silver "Sharpie" markings around the rim of the wheel that add to the appearance of the wobbling.
We did see the climb up on the shot you mentioned.
We will be testing to see if that occurs regularly, or just by not inserting the Frisbee to the shooter correctly.
This is also one of the reasons we are looking into a top plate(s).
waialua359
10-01-2013, 18:35
If making a "wide" bot, I'd assume one would make a circular path shooter vs. a linear one OR vice versa.
Online videos have shown both to be effective and consistent.
The choice to do either becomes how you acquire the pieces and load them into the shooter themselves.
robotinthreedays wasn't really using a nip contact - they were using pneumatic tires, with a couple inches of contact per wheel thanks to compression. You can really see it in http://www.youtube.com/watch?v=GT88vWTYgj0 when they're feeding the frisbee through by hand. 2009 and 2012 both had flexible game pieces, so the contact patches got extended by squeezing the balls through a cannon, but this year that give needs to be on the tire instead.
scaryone
11-01-2013, 09:31
Looks like a Plexi table/base material? We started with plywood (we always use wood), tried plexi and found remarkable loss of distance. Try sliding a Bee across plexiglass vs plywood by hand and you can feel the difference. Nice jig by the way.
Our circular (90) degree shooter uses and AM pneumatic 7.5 inch wheel with a 32 tooth sprocket on it and a 25 tooth sprocket on the CIM. We have it set up so the wheel is hitting just above the widest diameter of the disk and just below the widest diameter of the tire with about 1/4 inch of compression and the tire at maybe 10psi. This ensures the disk does not ride up on the tire. This puppy will hit the top of a 10 foot door at 45 feet. up down variation is about 6 inches and side to side variation is almost nonexistent.
This is just with a plywood POC. You can read that as Proof of Concept or Piece of C&^%. Whatever. Still need to add a guide on the outer rail to keep the disk from riding up on that.
We have also tested a straight shooter bot so far it is not as consistent and much less powerful even with 2 wheel powered by separate CIMs.
Still plan on a little more testing here as I think it would be easier to incorporate to the robot.
Our circular (90) degree shooter...
You posted this identical post in three different threads.
http://www.chiefdelphi.com/forums/sh...46#post1213846
http://www.chiefdelphi.com/forums/showthread.php?p=1213856#post1213856
It might be better to post it once and provide a link.
Hey I was wondering what kind of high speed camera do you have and how much did it cost??
Thanks
F22Rapture
12-01-2013, 21:55
What do you guys think about an in-line loader and shooter, similar to 548's design last year? Other than some difficulty getting it compact enough to fit length wise and keeping it stable at the very end (since the CIMs would be placed at the tip of the "cannon") it seems the easiest to aim because there is no second loading mechanism that has to stay in alignment.
Is there a point where too much rpm on the flywheel causes the exit velocity of the Frisbee to drop?
Is there a point where too much rpm on the flywheel causes the exit velocity of the Frisbee to drop?
http://www.chiefdelphi.com/forums/showpost.php?p=1212312&postcount=55
http://www.chiefdelphi.com/forums/showpost.php?p=1212312&postcount=55
Okay, thank you. Now to expand on my question. How can we tell (without a high speed camera) when this is happening? Should we just very the voltage until we find it shoots the furthest? What is the best way of going about this?
billbo911
13-01-2013, 01:58
Hey I was wondering what kind of high speed camera do you have and how much did it cost??
Thanks
It is the GoPro HERO 3 Black edition (http://gopro.com/hd-hero3-cameras). Right now they are listed at $399.99. It is capable of WVGA at 240 f/s.
RRLedford
13-01-2013, 04:17
Has anyone thought of whether a benefit could derive from a hybrid combination of a 90 degree circular shooter with a linear double wheel shooter?
There would only be one wheel but the frisbee would be pinched twice during its transit through the launcher.
The twist would be that instead of a pure circular arc roll edge shape, the shape would be a straight going into a 90 degree corner having a radius that matches the frisbee. So there would be linear roll contact with wheel for some period, then the frisbee would separate from wheel and whip around through the sharp 90 degree corner radius, going back to contact the wheel a second time, and then exiting rolling against a straight edge.
Would the effect of being whipped around the sharper corner help to possibly give some better acceleration grip from a higher centrifugal force there than a larger arc, despite there being no pressure from the wheel while going through the corner, or is it just the wheel squeeze that transfers all the energy, and longer squeeze contact is the main goal?
Also, could a straight roll edge going past the wheel then transition to a spiral curve shape on the outlet side to improve acceleration?
-Dick Ledford
Very interesting information. TNX
Question is: Where you driving the 8" wheel with a single CIM?
Jon, who were you asking that question of?
Bruceb:
Sorry for the confusion. I intented to address the question to billbo911.
billbo911:
Very interesting & useful information. TNX
Question is: Were you directly driving the 8" wheel with a single CIM?
billbo911
13-01-2013, 11:55
Bruceb:
Sorry for the confusion. I intented to address the question to billbo911.
billbo911:
Very interesting & useful information. TNX
Question is: Were you directly driving the 8" wheel with a single CIM?
Yes, it is an AndyMark 8in. Plaction wheel with roughtop tread (http://www.andymark.com/product-p/am-0513.htm).
It is being direct driven by an AndyMark 8mm Key Hub (http://www.andymark.com/product-p/am-0320.htm) from a CIM. Alrhough, we also did a test with the Mini CIM and it worked well too, but the current draw was higher.
Yes, it is an AndyMark 8in. Plaction wheel with roughtop tread (http://www.andymark.com/product-p/am-0513.htm).
It is being direct driven by an AndyMark 8mm Key Hub (http://www.andymark.com/product-p/am-0320.htm) from a CIM. Alrhough, we also did a test with the Mini CIM and it worked well too, but the current draw was higher.
Keep in mind that AM probably hasn't don't impact testing at high speeds (2k rpm +). If you're keen on using 8" AM wheels for the actual robot, perhaps you're better off paying for 1 single Aluminum wheel that doesn't flex than 2 or more plaction wheels that may (or may not) shatter. Personally, I'd put as many discs through that launcher as possible just to see what the wear will be like.
Team Leader
15-01-2013, 00:44
Our team is currently prototyping both a linear and curved shooter.
We posted a video on YouTube:
http://www.youtube.com/watch?v=bsaWp0URvN4
Squeakypig
15-01-2013, 22:15
We did side-by-side comparisons of a 1-wheel round shooter to a 1-wheel straight shooter. The straight shooter is powered directly by a CIM, the round shooter is actually spinning at a 1.5:1 ratio off of a CIM.
http://www.youtube.com/watch?v=ba6m4Ac9Ehc
http://www.youtube.com/watch?v=umH8X2zHP8k
They seem pretty equal except for the fact that we have the motor on the round shooter spinning at 150% of what the straight shooter is spinning at.
We did side-by-side comparisons of a 1-wheel round shooter to a 1-wheel straight shooter. The straight shooter is powered directly by a CIM, the round shooter is actually spinning at a 1.5:1 ratio off of a CIM.
http://www.youtube.com/watch?v=ba6m4Ac9Ehc
http://www.youtube.com/watch?v=umH8X2zHP8k
They seem pretty equal except for the fact that we have the motor on the round shooter spinning at 150% of what the straight shooter is spinning at.Can I ask why you're shooting so low?
karomata
16-01-2013, 11:49
Robot in 3 days did a linear shooter, and it seemed to have really good accuracy, but the linear shooters also have a larger footprint. On the other hand, it can be fed from an end, and fire out the opposite, whereas the circular path shooter type needs to be fed on a side that is 90 degrees away from the place where the discs exit the shooter. This can make storage and transportations of discs through robots a lot more complex. It really all depends on how your robot is layed out component wise.
Squeakypig
16-01-2013, 12:33
Can I ask why you're shooting so low?
Just doing a side-by-side comparison. We just decided to do it at the same height and angle as each other. We were just keeping the conditions of the 2 shooters as equal as possible, no real rhyme or reason for doing it the way we did except for simplicity purposes.
RRLedford
17-01-2013, 15:39
Basic dual belt concept with pivot bar idlers fixed => i.e without any spring loaded swing arms added between idlers & pivot bars. It is explained in detail in this other thread --
http://www.chiefdelphi.com/forums/showthread.php?t=111200&page=2&highlight=dick+ledford
http://i489.photobucket.com/albums/rr259/RRLedford/FRC2013/DualBelt_zps405d60fa.jpg
-Dick Ledford
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