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Spectrum 3847 Blog
The Blue Alliance Blog Post
Blog posts with links to download the full CAD model either as Solidworks files from our GrabCAD partner space or a STEP file.
Spectrum 3847 on Episode 4 of check_in
With a discussion about some of the design decisions that went in to this robot.
01-02-2017 14:14
flemdogmillionThat arm on the front stays inside the maximum robot volume, right? It looks like you're going with the tall dimension set, and it also looks like lowering that arm is against the rules.
01-02-2017 14:19
notmattlythgoe
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That arm on the front stays inside the maximum robot volume, right? It looks like you're going with the tall dimension set, and it also looks like lowering that arm is against the rules.
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01-02-2017 14:22
lukekaiser
01-02-2017 14:23
Chris is me|
That arm on the front stays inside the maximum robot volume, right? It looks like you're going with the tall dimension set, and it also looks like lowering that arm is against the rules.
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01-02-2017 14:23
Ryan Dognaux
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That arm on the front stays inside the maximum robot volume, right? It looks like you're going with the tall dimension set, and it also looks like lowering that arm is against the rules.
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01-02-2017 14:28
fresh_prince|
That arm on the front stays inside the maximum robot volume, right? It looks like you're going with the tall dimension set, and it also looks like lowering that arm is against the rules.
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01-02-2017 14:31
AllenGregoryIV
The robot frame is a ~29in square making our dimensions with bumpers about 36" square. That gives us 4 inchs of room to extend past the bumpers. The mecanum intake and the gear intake both come close to the full extension limit but can't possibly break it.
And of course we are short. Top of the robot is 23.8in I believe but the student that's doing most of the shooter CAD can tell you for sure that we are under.
01-02-2017 14:34
fresh_prince|
Top of the robot is 23.8in I believe but the student that's doing most of the shooter CAD can tell you for sure that we are under.
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01-02-2017 14:42
Michael Corsetto
Allen,
Really cool bot, love what your team is doing with the open build/blog. Seems like a great learning experience for your team.
Whats the process for scoring the gear once in the gear holder?
Great work as always,
-Mike
01-02-2017 14:42
lukekaiserVery nice. What is the upper appendage intended for?
01-02-2017 14:45
notmattlythgoe
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Allen,
Really cool bot, love what your team is doing with the open build/blog. Seems like a great learning experience for your team. Whats the process for scoring the gear once in the gear holder? Great work as always, -Mike |
01-02-2017 14:46
JesseKThis makes me wonder how they'll inspect boundaries this year. Our arm is 1" within the boundary with fully-down, but comes to within 0.25" of the boundary during articulation up/down.
01-02-2017 14:48
dodar|
This makes me wonder how they'll test things this year. Our arm is 1" within the boundary with fully-down, but comes to within 0.25" of the boundary during articulation up/down.
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01-02-2017 14:50
fresh_prince
01-02-2017 14:52
RoboChair|
The roller with the Vectored Intake wheels is our full-width fuel intake.
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01-02-2017 14:55
D_PriceGreat looking robot there! Awesome cad work as always.
01-02-2017 14:56
AllenGregoryIV
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Allen,
Really cool bot, love what your team is doing with the open build/blog. Seems like a great learning experience for your team. Whats the process for scoring the gear once in the gear holder? Great work as always, -Mike |
01-02-2017 14:57
Cothron Theiss
01-02-2017 14:59
EricLeifermannWhat is your shooter drum made out of?
This is awesome, just wish my computer would load the step file so I could get into the model more.
01-02-2017 15:09
fresh_prince|
What is your shooter drum made out of?
This is awesome, just wish my computer would load the step file so I could get into the model more. |
01-02-2017 15:11
EricLeifermann|
The current version is 45A high-temperature silicone rubber tubing from McMaster, I believe 1" ID 1.25" OD, stretched around 1.25" aluminum tubing. We hope to Smith to some white 35A though to keep with our colour scheme (and maybe get some better grip on the ball).
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01-02-2017 15:17
fresh_prince|
We used that in our testing but it expanded too much. It looks like your're using a belted 2:1 reduction from a 775pro, have you not seen this expansion as well?
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01-02-2017 15:21
EricLeifermann|
What speeds were you testing at? We were testing primarily at 6000 rpm and didn't notice any separation from the aluminum or excessive expenses.
Granted, we did used solid 4" conveyor wheels [I know them as fairline (Fairlane?) Wheels, but maybe Allen can reply with their proper name] to shoot in 2016, and those loved to expand so maybe we're just used to shooter wheel expansion. |
01-02-2017 15:29
fresh_prince|
I don't know what we were spinning them at accurately but it was faster than 6000. The problem wasn't that the expansion was affecting the shots, its that I wasn't comfortable safety wise with the expansion. We were also using 2in roller over a 1.5 aluminum tube, so maybe the smaller diameter doesn't expand as much was we saw with the large.
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01-02-2017 15:34
jkelleyrtpHow many balls can you guys hold? Doesn't look like the traditional hopper to me, are you planning on intaking only?
01-02-2017 15:37
fresh_prince|
How many balls can you guys hold? Doesn't look like the traditional hopper to me, are you planning on intaking only?
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01-02-2017 15:42
Mecanum Wheel|
So if "vectored intake wheels" are now a thing, does that mean we can add mecanum to the list of misspellings of mecanum-err-vectored intake wheels?
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01-02-2017 15:54
holygrailGreat bot as always! I really like the built-in handles.
Nice work!
01-02-2017 16:11
Kevin Sevcik
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I don't know what we were spinning them at accurately but it was faster than 6000. The problem wasn't that the expansion was affecting the shots, its that I wasn't comfortable safety wise with the expansion. We were also using 2in roller over a 1.5 aluminum tube, so maybe the smaller diameter doesn't expand as much was we saw with the large.
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01-02-2017 16:14
EricLeifermann|
Centrifugal acceleration* = w^2 * r. More RPMs and more radius = more force expanding your tube. Since this acceleration applies to all of the tube, thickness won't matter, aside from the smaller force on the ID of the tube. The only material property that matters is some sort of ratio of density and elastic modulus, but that'd be the same since ou said it was the same stuff.
So all in all, not surprising your tube wanted to expand more than Spectrum's. Are you guys going for a longer shot to need that much more surface speed? |
01-02-2017 17:16
Brian SelleNice job 3847! What are the servo motors on the front/back of the shooter for?
01-02-2017 17:21
fresh_prince|
Nice job 3847! What are the servo motors on the front/back of the shooter for?
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02-02-2017 01:32
Joy4201This is so amazing!
My team and I just had a few questions:
What is your shooter compression and how did you settle upon this number?
What is your intake height and how did you find this number?
02-02-2017 03:34
AllenGregoryIV
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This is so amazing!
My team and I just had a few questions: What is your shooter compression and how did you settle upon this number? |
| What is your intake height and how did you find this number? |
02-02-2017 14:19
GeeTwo
Great design! Ironically, just looking at your rather complex robot, I was inspired of a way to make our gear pickup MUCH simpler (replace two motors with one belt). Thanks!
02-02-2017 15:11
Bob SteeleBeautiful looking robot... and the CAD is nicely done.
I am looking forward to seeing how this plays on the field.
Well done!!
02-02-2017 15:50
Joe G.
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Agreed
Teams need to make sure they read all rules pertaining to robot size carefully. I would hate to see a robot this well designed get to a competition and then not pass inspection. |
02-02-2017 16:11
Chris is me|
I'm equally worried about teams building drive base/bumper assemblies to the maximum allowed dimension, and then regretting this decision when they realize all the cool things they could have achieved with a smaller base that enabled over-the-bumper dropdowns. In past years, iterating in new systems was just a matter of finding the space and weight, this year there are going to be a lot of teams boxed out of improving their robots and adding features like Spectrum has because they assumed bigger=better early in the process.
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02-02-2017 17:13
Ty Tremblay|
I honestly expect the opposite to happen - teams built chasses that were too small so they could do over-the-bumper stuff, expecting a huge advantage, then realizing it was more trouble than its worth and are now sad about the substantial decrease in ball capacity they traded for that decision.
3847's robot is a good example of leaving a conservative amount of space (just an inch or three) for OTB stuff, but I bet others left way more than they should have. |
02-02-2017 17:37
ngreen
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Why does a smaller frame necessarily mean a reduction in ball capacity?
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02-02-2017 23:00
Chris is me|
Why does a smaller frame necessarily mean a reduction in ball capacity?
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02-02-2017 23:32
Ty Tremblay|
I mean, if you grow your hopper out over the top of your intake, sure. But if you grow your hopper out in that direction, isn't that just going to stick out the same distance as your over-the-bumper intake? Which then isn't sticking out farther than your robot's frame anymore? Isn't that kind of defeating the purpose then?
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02-02-2017 23:44
cadandcookies|
I mean, if you grow your hopper out over the top of your intake, sure. But if you grow your hopper out in that direction, isn't that just going to stick out the same distance as your over-the-bumper intake? Which then isn't sticking out farther than your robot's frame anymore? Isn't that kind of defeating the purpose then?
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03-02-2017 09:57
nick4130This CAD looks beautiful, cant wait to see this robot on the field.
03-02-2017 10:03
Chris is me|
I'm not 100% sure I follow. If you're extending your hopper with your collector, you negate the effects of making your frame smaller while still gaining the advantages of an over-the-bumper collector.
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03-02-2017 10:09
Ty Tremblay|
The primary advantage of an over-the-bumper collector, other than width (which is significant), is that the leading edge of your robot is your collector instead of your frame and/or bumper. If you move your "frame" (hopper) out just as far forward as your collector, you remove that advantage - your frame could contact a wall before your collector contacts a ball along that wall, etc. If your roller still protrudes out farther than your hopper, then you have to at least some extent compromised your hopper space.
Considering even a full length robot can actuate their front roller so that it occupies the space between the frame and the edge of the bumper, this advantage starts to seem limited to making the collector wider. Again, this is a sizeable advantage, but at the same time, the field will have hundreds of balls on it, and I'm not sure the complexity of this solution is justified for this benefit. It's not zero benefit, and it's certainly worth exploring for many teams, I just wonder if the tradeoff in complexity and / or ball storage will end up being clearly worth it or not. This isn't the path my team took and it certainly simplified a lot of the robot once we decided not to do this, plus we still have the option to switch to a drop-down "in-the-bumper" intake if we really need that little bit of roller to grab balls against walls. |
03-02-2017 10:26
Chris is me|
The balls are 5" in diameter. This means you can have a 4" collector wheel/drum, bring your hopper out to the outside edge of those wheels, and still have your collector touch the ball before your hopper touches the wall. If you make your collector smaller in radius, your hopper well be even further away from the wall when the ball gets collected.
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03-02-2017 12:33
RobomarfaNice work 3847. SJCP has come a long way since I left in 77.
03-02-2017 14:36
Keefe2471Another benefit of an over the bumper intake being the full width of your front bumper (minus the 3.5 inches of side bumbler on each side) is that it minimizes the ability of balls to space you off the wall by 5 inches. Even with the maximum size gap in your front frame perimeter you still have 19 inches (6*2 + 3.5*2) of bumper without a way to move balls out of the way Scoring gears, picking up gears, inbounding fuel from both the hopper and human player station, and catching HE fuel rebounds are all potentially compromised when your robot can't get flush to the wall. With some spinning and approach angle practice maybe you can knock those balls flying with some consistancy, but critical seconds could be wasted each time you perform one of those operations.
03-02-2017 18:42
Lil' Lavery
Are you using a PTO for your climber? Or will it be linked to one side of your drive at all times? If so, are you concerned about any additional drag generated for that drive side? Are you going to steering correct with sensors/software?
03-02-2017 20:10
fresh_prince|
Are you using a PTO for your climber? Or will it be linked to one side of your drive at all times? If so, are you concerned about any additional drag generated for that drive side? Are you going to steering correct with sensors/software?
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05-02-2017 00:07
fresh_prince|
Nice job 3847! What are the servo motors on the front/back of the shooter for?
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