Team 254 Presents: Dropshot Technical Binder 2016

[Cherry254]

Team 254 Presents: Dropshot Technical Binder. The binder can be found here (https://media.team254.com/2016/05/97d107e6-technicalBinder2016.pdf). If you have any questions or want more specifications, feel free to ask!

[Gravity]

Team 254 Presents: Dropshot Technical Binder. The binder can be found here (https://media.team254.com/2016/05/97d107e6-technicalBinder2016.pdf). If you have any questions or want more specifications, feel free to ask!
Wow, this is an amazing resource, just goes to show how prepared and well structured your team is. :)

[414cnewq]

This is an amazing look into the development of an effective robot.

[frcguy]

Incredible documentation of an incredible robot, as always :).

[orangelight]

Do you have any pictures of the camera and camera mount with the green light off?

[kyle_hamblett]

Thanks for posting this! I was glad I got to take a peek at it at champs. Will you be releasing code at some point?

[scott.smith]

I was going to do my homework, and then I saw this, well... 254 won over. Best reading I have done in ages. ::rtm::

[snekiam]

Are those dead LEDs in your ring on the last page?

[Michael Hill]

Awesome robot as usual.

I've been curious about your turret gear. It looks similar to 1114's from 2012, but from my guesstimates, it's 20dp @ 16.1" Pitch Diameter whereas 1114 had a much larger geartooth (something like 10-12dp). One of my main concerns is actually having our waterjet sponsor cut teeth that small (I've been contemplating turrets lately). Was it relatively easy for your sponsor to do or was there anything special you had to do to the gear design to make it easier to manufacture? I'm guessing going to 0.125" aluminum made it easier, but is that enough?

[caume]

What do you use as a thrust bearing for your turret? Also, why do you only use two CIMs in your drive? You need moar pushes

[AdamHeard]

Awesome robot as usual.

I've been curious about your turret gear. It looks similar to 1114's from 2012, but from my guesstimates, it's 20dp @ 16.1" Pitch Diameter whereas 1114 had a much larger geartooth (something like 10-12dp). One of my main concerns is actually having our waterjet sponsor cut teeth that small (I've been contemplating turrets lately). Was it relatively easy for your sponsor to do or was there anything special you had to do to the gear design to make it easier to manufacture? I'm guessing going to 0.125" aluminum made it easier, but is that enough?

We did 24DP gears in 2012 for turret (and some other systems) and they worked just fine w/ our waterjet sponsor.

254 did 20DP this year to mate w/ vex gears.

[trumpthero786]

Oh my goodness. That is absolutely beautiful. Your documentation has always been amazing and it's crazy to see that it is getting even better. I've never seen anything like this. Thank you so much for sharing and being such an amazing inspiration to all teams.

[z_beeblebrox]

Also, why do you only use two CIMs in your drive? You need moar pushes

They've got 4. See the image on page 10. The motor in the gearbox render is hidden to show the other components.

[bigbeezy]

Awesome robot as usual.

I've been curious about your turret gear. It looks similar to 1114's from 2012, but from my guesstimates, it's 20dp @ 16.1" Pitch Diameter whereas 1114 had a much larger geartooth (something like 10-12dp). One of my main concerns is actually having our waterjet sponsor cut teeth that small (I've been contemplating turrets lately). Was it relatively easy for your sponsor to do or was there anything special you had to do to the gear design to make it easier to manufacture? I'm guessing going to 0.125" aluminum made it easier, but is that enough?

I'm curious about this as well. Not just turrets, but any gear tooth profile like you used for the hood. I know y'all have a laser but would a waterjet be able to do 20DP gears?

[Dan Petrovic]

Can I get some more information about the 2" OD surgical tubing that was used on the intake? After searching for 2" OD black rubber tubing on McMaster, the only result given was nitrile tubing with a 60A durometer hardness. Is this the same stuff?

Bringing the OD down to 1.5" (still black opaque) returns latex tubing with a hardness of 40A, more in-line with what Banebots uses on their wheels.

Is there another supplier where 2" latex tubing is available?

[Greg Woelki]

would a waterjet be able to do 20DP gears?

Yes. We did it this year for our hood's sector gears and our waterjetting sponsor didn't have to do anything special for them. (Picture (https://drive.google.com/file/d/0B4upfebDeXT_Y21ZeVV3RHVKanc/view?usp=sharing))

[Travis Covington]

Can I get some more information about the 2" OD surgical tubing that was used on the intake? After searching for 2" OD black rubber tubing on McMaster, the only result given was nitrile tubing with a 60A durometer hardness. Is this the same stuff?

Bringing the OD down to 1.5" (still black opaque) returns latex tubing with a hardness of 40A, more in-line with what Banebots uses on their wheels.

Is there another supplier where 2" latex tubing is available?

I think this is an error and we are in fact using 1.5" OD latex tubing as you are finding on McMaster.

[Cory]

Awesome robot as usual.

I've been curious about your turret gear. It looks similar to 1114's from 2012, but from my guesstimates, it's 20dp @ 16.1" Pitch Diameter whereas 1114 had a much larger geartooth (something like 10-12dp). One of my main concerns is actually having our waterjet sponsor cut teeth that small (I've been contemplating turrets lately). Was it relatively easy for your sponsor to do or was there anything special you had to do to the gear design to make it easier to manufacture? I'm guessing going to 0.125" aluminum made it easier, but is that enough?

Depends on the water jet nozzle diameter. Our sponsor can't do anything a .035" diameter stream can't fit into. That diameter stream will just get into the root of a 20 dp gear tooth. It would not work for our hood gears, had we attempted to water jet them.

There was really no special design consideration. This was done on a very new water jet with a tilting head to compensate for stream lag and eliminate taper, which basically cuts perfect parts.

[TheModMaster8]

Is their anyway we could get a CAD download link of the robot?

[jkelleyrtp]

How was your experience with mechanum wheels for an intake? Are you likely to use them again in the future?

[s5511]

How did you guys have 3 positions on your utility arm using pistons? During matches, it looked like there was an all the way up, slightly raised, and completely down position for the arm.
Also, are the 1.5'' bore pistons which raise the utility arm mounted directly to the arm? It doesn't look like in it your pictures, but I can't exactly tell.

Thanks!

[sanddrag]

I've only had a chance to skim it, but once again, very nice looking, and a valuable resource to other teams like ours. Thanks for releasing this.

I'm curious to know what pneumatic wheel hubs those are, or if you made them. Are there any additional photos of the wheel hubs?

Also, the PDF text looks to have exported as a raster image rather than as vector text. Not sure if you meant to do that.

[Travis Covington]

I've only had a chance to skim it, but once again, very nice looking, and a valuable resource to other teams like ours. Thanks for releasing this.

I'm curious to know what pneumatic wheel hubs those are, or if you made them. Are there any additional photos of the wheel hubs?

Also, the PDF text looks to have exported as a raster image rather than as vector text. Not sure if you meant to do that.

Wheel hubs are custom, but very similar to the WCP ones. The obvious difference is that these are sized for the 8" pneumatic tires, and as such, have similar dimensions to the AM plastic hubs. Not a lot of weight savings though. Probably not worth the effort for most.

Our guys are updating the PDF now. Nice catch!

[Ashwin Adulla]

What do you use as a thrust bearing for your turret? Also, why do you only use two CIMs in your drive? You need moar pushes

We have 7 bearing assemblies along our turret gear which you can see if you look closely on page 16. Each bearing assembly consists of 3 ball bearings in the following order: a large bearing, a small bearing, and a large bearing (I do not know the exact bearing size). Each bearing is separated by a small shim and is lined up along a 10-32 screw with a locknut threaded at the bottom of the screw. The locknut is not tightened to its fullest extent in such a way that as the two large bearings sit upon the top and bottom of the plate connecting the two sides of the superstructure, they are able to slide along the plate's surface in addition to the small bearing with can rotate freely as it contacts the inner edge of the plate.

[AdamHeard]

We have 7 bearing assemblies along our turret gear which you can see if you look closely on page 16. Each bearing assembly consists of 3 ball bearings in the following order: a large bearing, a small bearing, and a large bearing (I do not know the exact bearing size). Each bearing is separated by a small shim and is lined up along a 10-32 screw with a locknut threaded at the bottom of the screw. The locknut is not tightened to its fullest extent in such a way that as the two large bearings sit upon the top and bottom of the plate connecting the two sides of the superstructure, they are able to slide along the plate's surface in addition to the small bearing with can rotate freely as it contacts the inner edge of the plate.

1601 (large bearing) - R3 (small bearing) - 1601.

R3 handles the radial load, 1601 acts as the thrust load (but has a sliding contact on the face of the bearing ring).

[JesseK]

Thanks for posting!

[Cherry254]

How was your experience with mechanum wheels for an intake? Are you likely to use them again in the future?

We experienced some jamming and stalling issues but that was because the intake geometry was not perfect. Additionally, neither roller extended past the weldment so we were not able to pick up Boulders from the edge of the intake. The major issues with the intake were separate from the use of mecanum wheels.

[seans341]

Thanks for posting this! I noticed that turret compatibility was a significant factor in the overall design process. What did you notice about the game that made a turret so appealing?

[Cherry254]

How did you guys have 3 positions on your utility arm using pistons? During matches, it looked like there was an all the way up, slightly raised, and completely down position for the arm.
Also, are the 1.5'' bore pistons which raise the utility arm mounted directly to the arm? It doesn't look like in it your pictures, but I can't exactly tell.

Thanks!


The Utility arm can go into 4 positions using deployable hardstops and kickstands. Its 4 states were drive mode, Low Bar mode, Starting configuration and hang mode. The pneumatic cylinders mounted to the plates extending down at the bottom of the arm as seen on page 21. Below see the deployable hardstops.

[Cory]

Thanks for posting this! I noticed that turret compatibility was a significant factor in the overall design process. What did you notice about the game that made a turret so appealing?

Low robot with a blockable shot that had to be in one specific place on the field to make shots, or have the front of the robot normal to the goal to shoot was clearly going to be a death sentence at high levels of play.

[caume]

They've got 4. See the image on page 10. The motor in the gearbox render is hidden to show the other components.
I meant to say two CIMs per side, four total. Why not use six?

[Mike Schreiber]

The Utility arm can go into 4 positions using deployable hardstops and kickstands. Its 4 states were drive mode, Low Bar mode, Starting configuration and hang mode. The pneumatic cylinders mounted to the plates extending down at the bottom of the arm as seen on page 21. Below see the deployable hardstops.

Given an arm that needed four positions, why was the decision made to go pneumatic compared to a motor driven arm?

[JesseK]

I meant to say two CIMs per side, four total. Why not use six?

The only real advantages to 6 CIMs (when considering the risk of tripping the main breaker) are Powered Take Off and acceleration on an open field. Looks like 254 didn't do PTO, and the field wasn't really "open" like in some prior years.

[caume]

#35 Chain runs along the side rails running on 12 tooth sprockets to clear the bellypan
Why did you decide to go with #35 chain this year, instead of the usual #25?

Sector gears on the back are driven by the servo to adjust shot trajectory
Why did you use a servo in place of the pistons you used in 2014? I'm guessing it was for theoretically infinite hood positions, but I would think 4 or so would be enough. I guess it could possibly require some motor speed modification, but I would think that would be fairly easy...

A surgical tubing feeder roller on a dead axle is driven by a BAG motor with a compact 5-stage reducing using lightened 32DP gears.
Isn't a bag motor with a 5-stage gearbox a bit overkill...? I would think having some mechanism like a piston ball loader would be enough, or at least a bag motor with a (planetary?) gearbox with fewer stages

Thanks in advance for any response.

[microbuns]

I'm curious where the ball sat while the turret was swiveling, and how it avoided the flywheel as well as the chassis during rotation. This was our teams biggest problem with turreted shooter who went under the low bar.

[Cherry254]

Why did you decide to go with #35 chain this year, instead of the usual #25?


Why did you use a servo in place of the pistons you used in 2014? I'm guessing it was for theoretically infinite hood positions, but I would think 4 or so would be enough. I guess it could possibly require some motor speed modification, but I would think that would be fairly easy...


Isn't a bag motor with a 5-stage gearbox a bit overkill...? I would think having some mechanism like a piston ball loader would be enough, or at least a bag motor with a (planetary?) gearbox with fewer stages

Thanks in advance for any response.

We bagged Dropshot with #25 chain but during driver practice we broke chain often. We modified the drive train and made the change to #35 chain at CVR (our first event) and did not have any issues during the season.

A servo was used for that very reason. Having a large range of hood positions allowed us to have an accurate shot from anywhere in the Courtyard.

We initially had a delrin basket that was pulled up by pneumatic cylinders to feed the ball into the shooter. The system had many issues leading to inconsistent shots. A custom gearbox was necessary because a planetary did not package inside the hood. The feeder roller and gearbox drastically helped our accuracy along with the other shooter modifications between Week 2 and Week 6.

[Cherry254]

I'm curious where the ball sat while the turret was swiveling, and how it avoided the flywheel as well as the chassis during rotation. This was our teams biggest problem with turreted shooter who went under the low bar.

The Boulder stalled against the feeder roller and the 0.25" aluminum "horseshoe" which supports that rails that guide the Boulder into the shooter. Can see the rails and roller on page 16.

[s5511]

I'm curious as to why you guys use chain instead of belts on your drivetrains. Is there any specific reason why you guys prefer chain?

[Tal_Esh]

Any link or properties about the Fairlane wheels? Saw those on 1241's shooter as well but couldn't manage to find them online.

[Ty Tremblay]

Any link or properties about the Fairlane wheels? Saw those on 1241's shooter as well but couldn't manage to find them online.

http://www.mcmaster.com/#2476k37/=12o2dgv

[apache8080]

What other wheels did you guys try out for the flywheel?

Do you guys use laser cut wood for majority of your prototypes? I assume that this makes prototyping easier and more accurate.

When is your code going to be released?

Thanks for this incredible resource.

[Michael Hill]

I'm curious as to why you guys use chain instead of belts on your drivetrains. Is there any specific reason why you guys prefer chain?

Because of the design of the gearbox, it would be a real PITA to change a broken belt. Also, it lets them get away with a slimmer gearbox because belts needed in a high torque, drive situation are wide.

[Ashwin Adulla]

What other wheels did you guys try out for the flywheel?

Do you guys use laser cut wood for majority of your prototypes? I assume that this makes prototyping easier and more accurate.

When is your code going to be released?

Thanks for this incredible resource.

We bagged and tagged our robot with 2 4" Colson wheels acting as our shooter. At CVR, we used 4 4" Colson wheels. At SVR and Champs, we used 2 4" Fairlane wheels with safety wire wrapped around it to stop it from expanding a significant amount past 5000 rpm.

Yes we did use a laser cutter for prototyping with wood and it greatly aided our prototyping process as we were able to quickly CAD and test different variables for our flywheel shooter (pg 13) such as hood angle, pulley ratios, ball traction, and moment of inertia. In addition we did use the laser cutter to test out different intakes and also to cut the hubs for our mechanum wheels.

As for the code, our programming team is performing a code clean and is planning to release it soon.

[Knufire]

Do you have a source for the various SHARP sensors the technical binder mentions?

[apache8080]

We bagged and tagged our robot with 2 4" Colson wheels acting as our shooter. At CVR, we used 4 4" Colson wheels. At SVR and Champs, we used 2 4" Fairlane wheels with safety wire wrapped around it to stop it from expanding a significant amount past 5000 rpm.

Yes we did use a laser cutter for prototyping with wood and it greatly aided our prototyping process as we were able to quickly CAD and test different variables for our flywheel shooter (pg 13) such as hood angle, pulley ratios, ball traction, and moment of inertia. In addition we did use the laser cutter to test out different intakes and also to cut the hubs for our mechanum wheels.

As for the code, our programming team is performing a code clean and is planning to release it soon.

Why did you guys switch from the Colson wheels to the Fairlane wheels?

[Kevin Sheridan]

Yes we did use a laser cutter for prototyping with wood and it greatly aided our prototyping process as we were able to quickly CAD and test different variables for our flywheel shooter (pg 13) such as hood angle, pulley ratios, ball traction, and moment of inertia. In addition we did use the laser cutter to test out different intakes and also to cut the hubs for our mechanum wheels.


Here is a picture of my favorite prototype from this year.
http://imgur.com/WTzdPiy.jpg

[TheModMaster8]

could i get a reply to my question??:confused:
It was easy to miss :)

[frcguy]

Heres a picture of my favorite prototype this year.

http://imgur.com/WTzdPiy.jpg


That's awesome :D

[Travis Covington]

could i get a reply to my question??:confused:
It was easy to miss :)

We have no plans to release the CAD of the robot but are happy to answer any questions you have.

[bigbeezy]

For the hood, it looks like you milled out a slot/track. Did you just use track rollers from McMaster or something different? How did you insure that the motion was smooth and didn't bind/be too lose and wobble?

For the Nexus 5 you have for vision, did you have to power it off of the robot? If so, did you just power via the USB or someother way?

Thanks for sharing, I (and my team) learn a lot from these.

[roboruler]

For the Nexus 5 you have for vision, did you have to power it off of the robot? If so, did you just power via the USB or someother way?

Internal Batteries are allowed for COTS computing devices. They did not open the phone up and remove the battery, instead they just ran a USB cable from the robo-rio to the phones charging/data port.

[bigbeezy]

Internal Batteries are allowed for COTS computing devices. They did not open the phone up and remove the battery, instead they just ran a USB cable from the robo-rio to the phones charging/data port.

Good to know, thanks!

[sanddrag]

Do you guys do your laser cutting in house? Whether it is or not, I'm curious what make and model of laser you use.

[ThemisH]

Why did you guys switch from the Colson wheels to the Fairlane wheels?
We saw that the Colsons weren't efficiently transferring energy to the ball, mostly due to not having a high enough coefficient of friction. Our 2014 robot Barrage used two 775 motors on the flywheel just like Dropshot, and yet it was able to launch a ball that was several times more massive than the Stronghold boulders. Barrage used Fairlane wheels, so we tried them on Dropshot and they greatly increased our power output, so we stuck with them. If you compare videos from CVR to SVR/Champs, the power difference is very noticeable.

[apache8080]

We saw that the Colsons weren't effieciently transferring energy to the ball, mostly due to not having a high enough coefficient of friction. Our 2014 robot Barrage used two 775 motors on the flywheel just like Dropshot, and yet it was able to launch a ball that was several times more massive than the Stronghold boulders. Barrage used Fairlane wheels, so we tried them on Dropshot and they greatly increased our power output, so we stuck with them. If you compare videos from CVR to SVR/Champs, the power difference is very noticeable.

Thanks for the information. It is always great to see how elite teams iterate their designs.

On the subject of iterations, why did you guys go away from gas shocks in the hanger.

[Ashwin Adulla]

For the hood, it looks like you milled out a slot/track. Did you just use track rollers from McMaster or something different? How did you insure that the motion was smooth and didn't bind/be too lose and wobble?.

For our hood, we did mill out a slot on both hood plates and used what could best be described as a T-slot roller to move along the slot (I have attached a link of a T-slot roller to better visualize how our sector gear was able to move along the slot). In our case, the T-rollers, two on each side, were made out of plastic and turned down on the lathe. While assembling the hood, we did encounter an issue of the motion being somewhat rough due to the friction as the lateral surface of the T-slot roller contacted the inner surface of the slot. To fix it, we simply took a small file and filed down the lateral surface of the roller in addition to cleaning the slot with isopropyl alcohol (we used the same alcohol on the inside of our hanger weldment to ensure the inner tube would smoothly extend out for hanging). As the sector gear did extend past the halfway point on the slot, a slight wobble was noticeable by virtue of the distance between the bottom of the sector gear and the top of the hood plate shortening. However, this wobble was not deemed to be significant concern affecting our shot.

http://el34world.com/Misc/Cnc/images/Img_7561.jpg

[Ashwin Adulla]

Thanks for the information. It is always great to see how elite teams iterate their designs.

On the subject of iterations, why did you guys go away from gas shocks in the hanger.

Initially, the idea of utilizing gas shocks as the means to scale the tower after time had ended seemed like a feasible idea in CAD. When it came to assembling them on the hanger however, we encountered the issue of both gas shocks releasing at different times as was evident in a test which consequently bent the hanger weldment. This problem could have either been attributed to a difference in the force exerted by each gas shock or a difference in force exerted by the pistons with a spring coiled around the rod that were used to compress the gas shocks. We knew that a winch gearbox was both a proven and feasible option, and thus we decided to implement it following SVR.

[thatprogrammer]

Based on your technical binder, it seems that you ran the neoprene wheels directly on hex shaft. How did you manage to do this?

[s5511]

Which solenoids/manifolds are you guys using on dropshot?

[Ashwin Adulla]

Based on your technical binder, it seems that you ran the neoprene wheels directly on hex shaft. How did you manage to do this?

We machined custom delrin hubs for each wheel which were able to be pressed on a 1/2" hex shaft.

[waialua359]

Travis, I had heard that you are the lead on the technical binder. Is this true?
Kudos to the mentors and the students who worked on this.
The most impressive part besides the actual robot with its features, is that you have it really condensed yet very informative on the whole design process, decision making and explanation of each of the systems.
Cory, our former mentor who was with my alma mater Team 4158 cut a lot of gears with a jet sponsor. Our team needs to get on board with ours soon and I need to research more about different nozzle sizes and what they can cut. Skies the limit.

[Torrance]

Travis, I had heard that you are the lead on the technical binder. Is this true?
Kudos to the mentors and the students who worked on this.
The most impressive part besides the actual robot with its features, is that you have it really condensed yet very informative on the whole design process, decision making and explanation of each of the systems.


The technical binder has always been a student led and written project as the students who compose it use it as practice for their presentation in the pits to Technical Award Judges. I wrote the binder in 2014 and 2015 and Travis did some editing to keep it concise and relevant. In 2016, Technical Director Alex Cherry and Documentation and Submissions Director Matt McDonald wrote it with me (now 1st-year mentor) serving as the editor.

The binder also required a lot of work from our Media Director Peter Feghali to do the renders, layout, and aesthetics.

[Travis Covington]

Travis, I had heard that you are the lead on the technical binder. Is this true?
Kudos to the mentors and the students who worked on this.
The most impressive part besides the actual robot with its features, is that you have it really condensed yet very informative on the whole design process, decision making and explanation of each of the systems.
Cory, our former mentor who was with my alma mater Team 4158 cut a lot of gears with a jet sponsor. Our team needs to get on board with ours soon and I need to research more about different nozzle sizes and what they can cut. Skies the limit.

Glenn,

As Andrew explained, the mentors typically have very little involvement in the technical binder other than helping edit content towards the end. This has been the students project from its inception.

[waialua359]

The technical binder has always been a student led and written project as the students who compose it use it as practice for their presentation in the pits to Technical Award Judges. I wrote the binder in 2014 and 2015 and Travis did some editing to keep it concise and relevant. In 2016, Technical Director Alex Cherry and Documentation and Submissions Director Matt McDonald wrote it with me (now 1st-year mentor) serving as the editor.

The binder also required a lot of work from our Media Director Peter Feghali to do the renders, layout, and aesthetics.

Thank you to you and Travis for sharing. You mentioned some other mentors who helped who I never heard of or met.
Teams like yours are an inspiration to many, including us. As a follow up, it would be cool to hear about the team structure and the mentors that support both the robot (many who we know) and the non-robot technical support that you folks have.
I'm sure many others would like to have something similar, but cant do so because of lack of support/expertise or mentors who wear too many hats. Sounds like Team 254 has the right mix of mentors to do the other parts as well besides dedicated and highly intelligent students.

I hope this is a project you folks continue to do and share post-season annually.

[Torrance]

Thank you to you and Travis for sharing. You mentioned some other mentors who helped who I never heard of or met.
Teams like yours are an inspiration to many, including us. As a follow up, it would be cool to hear about the team structure and the mentors that support both the robot (many who we know) and the non-robot technical support that you folks have.

Of the people I mentioned, only Travis (and sorta me) are mentors. Alex, Matt, and Peter are Directors on our student leadership team.

The team leadership structure is divided amongst the mentors and student leadership team which consists of Directors that lead sub-teams of other students and Captains that serve as project managers on particularly large tasks.

The team certainly has a lot of mentors, but this is essential for managing the 100+ students working on multiple projects. Our mentorship is unofficially divided into technical and non-technical mentors.
Going off of our Mentor Page (team254.com/mentors), the following are technical:
Travis Covington, Pat Fairbank, Cory McBridge, Tom Bottigleiri, Leigh Pauls, Kevin Sheridan, Paul Ventimiglia, Dan Judnick (mostly VEX), Kenneth Lloren, Jared Russel, Colin Wilson, Nick Eyre, Trevor Kearse. Also myself and fellow SCU student Mani Gnanasivam.

Nontechnical mentors include: Esteban Parker, David Wilson, Nick Hammes, and faculty Peng Yav and Brad Lindemann.

Not all of the mentors attend every build or every competition.


The student leadership team breakdown (recently updated for 2016-2017) is also on our website (https://www.team254.com/leaders/). As you can see, 1/2 of the positions are non-technical in nature.

The Directors closely collaborate on a lot of projects. For example, this technical binder was written by the FRC Technical Director with the help of a technical mentor (me or Travis). Then the Documentations and Submissions Director and a nontechnical mentor or 2 helped edit and clean up the bullets before giving it to the Media Director who's sub-team did the renders and formatted it using Word into the final document.


I hope this is a project you folks continue to do and share post-season annually.

We plan to! Creating the technical binder is a great learning experience for all the students involved, in addition to being a useful resource for judges or other teams.

[Michael Hill]

How do you guys do project management? Do you have design/concept reviews? What tools do you guys use to keep organized?

Also, somewhat off topic, we used a modified version of the 254 part management tool (cheesy parts) this year and it was fantastic. It really helped us especially get orders put together. Instead of writing orders down on a marker board or a piece of paper that can get lost, it was great to have everything organized the way it was.

[DinerKid]

Awesome write up.

I'm very intrigued by the safety wire that you used on the flywheel.
Would you mind elaborating on the reason you use it, process for installing it, and perhaps a picture?

Thanks
~DK

[waialua359]

How do you guys do project management? Do you have design/concept reviews? What tools do you guys use to keep organized?

Also, somewhat off topic, we used a modified version of the 254 part management tool (cheesy parts) this year and it was fantastic. It really helped us especially get orders put together. Instead of writing orders down on a marker board or a piece of paper that can get lost, it was great to have everything organized the way it was.
I vaguely remember seeing this previously. Can you share the link?

[waialua359]

Of the people I mentioned, only Travis (and sorta me) are mentors. Alex, Matt, and Peter are Directors on our student leadership team.

The team leadership structure is divided amongst the mentors and student leadership team which consists of Directors that lead sub-teams of other students and Captains that serve as project managers on particularly large tasks.

The team certainly has a lot of mentors, but this is essential for managing the 100+ students working on multiple projects. Our mentorship is unofficially divided into technical and non-technical mentors.
Going off of our Mentor Page (team254.com/mentors), the following are technical:
Travis Covington, Pat Fairbank, Cory McBridge, Tom Bottigleiri, Leigh Pauls, Kevin Sheridan, Paul Ventimiglia, Dan Judnick (mostly VEX), Kenneth Lloren, Jared Russel, Colin Wilson, Nick Eyre, Trevor Kearse. Also myself and fellow SCU student Mani Gnanasivam.

Nontechnical mentors include: Esteban Parker, David Wilson, Nick Hammes, and faculty Peng Yav and Brad Lindemann.

Not all of the mentors attend every build or every competition.


The student leadership team breakdown (recently updated for 2016-2017) is also on our website (https://www.team254.com/leaders/). As you can see, 1/2 of the positions are non-technical in nature.

The Directors closely collaborate on a lot of projects. For example, this technical binder was written by the FRC Technical Director with the help of a technical mentor (me or Travis). Then the Documentations and Submissions Director and a nontechnical mentor or 2 helped edit and clean up the bullets before giving it to the Media Director who's sub-team did the renders and formatted it using Word into the final document.




We plan to! Creating the technical binder is a great learning experience for all the students involved, in addition to being a useful resource for judges or other teams.

Thanks for the info. Half of the info, I should have just looked on your website, but very helpful with the explanations.

That is one impressive list of mentors, where many have come from other teams originally.:ahh:

I noticed seeing Leigh Pauls. I had just asked about him at VEX Worlds and heard from Karthik that he was with you folks. I met him at 2010 VEX Worlds when we teamed up to get to the World's Finals matches, ironically, with a 3rd team partner deemed the "Chinese Poof Clone" robot.

[Michael Hill]

I vaguely remember seeing this previously. Can you share the link?

Info page: https://www.team254.com/documents/cheesyparts/

Github page: https://github.com/Team254/cheesy-parts

I modified it for my team to accept our part numbering scheme (IRYY-AA-SPP)

IR = Innovators Robotics
YY = 2-Digit Year
AA = 1-up Assembly #
S = 1-up Subassembly #
PP = 1-up Part #

[Torrance]

How do you guys do project management? Do you have design/concept reviews? What tools do you guys use to keep organized?

Also, somewhat off topic, we used a modified version of the 254 part management tool (cheesy parts) this year and it was fantastic. It really helped us especially get orders put together. Instead of writing orders down on a marker board or a piece of paper that can get lost, it was great to have everything organized the way it was.

Our team's project management is still not as clean and organized as we'd like it to be. We do still use Cheesy Parts but only really as a method of generating part numbers so we can label CAD files according to their assembly and not overlap file names. For example: "254-16-P-0308" is a shaft in the 0300 drive gearbox assembly.

Project management is largely run by a team of core technical mentors (Travis, Cory, Colin, Nick, Pat) and the student FRC Technical Director. We'll sometimes write a To-Do List on a whiteboard and have a brief meeting at the beginning of the build during dinner to cover what we want to accomplish that night.

Other than Cheesy Parts and whiteboards, a big portion of the project management relies on mentors and upperclassmen being in constant attendance so they can manage what they're working on. By only having builds Monday, Wednesday, Friday, and Saturday this year we got higher attendance at each and that helped ensure there was always an available project leader.

Design reviews often occur unofficially, late at night, or just with relevant students and mentors. By not having "too many cooks in the kitchen" we can keep them concise and on topic. However, we notably had a team-wide discussion a few days after kickoff to finalize our decision to go with the "Steph Curry" robot (see Tech Binder pg 5).

In the past we tried project management softwares like Trello but gave it up because the hassle of constantly entering and editing meant our students didn't keep it up to date.

Finally, we have an Action Items project management page that our student Leaders use for mostly non-technical action items assigned to them as weekly leader meetings. An example might be "Call welding sponsor and ask if they will sponsor us again".

[Jay O'Donnell]

Andrew (or other 254 members), would you mind giving a general timeline of your season? Such as when certain robot decisions and milestones occurred?

[waialua359]

Andrew (or other 254 members), would you mind giving a general timeline of your season? Such as when certain robot decisions and milestones occurred?

I recall they had this also? Or I might be confusing it with some other team.

[Ashwin Adulla]

Awesome write up.

I'm very intrigued by the safety wire that you used on the flywheel.
Would you mind elaborating on the reason you use it, process for installing it, and perhaps a picture?

Thanks
~DK

The main purpose of the safety wire, as suggested by Team 1678, was to prevent our fairlane flywheel from expanding a significant amount past 5000 rpm. During prototyping, the fairlane wheels expanded to the extent that we were fearful of testing them out. As a result, the safety wire constrained the expansion of the wheels to a certain diameter which allowed us to ramp up to around 6000 rpm at Champs for taking shots. As for the process of installing them, the safety wire was wrapped once around the wheel, cut to its length, and then two ends were twisted together and then stuck inside the neoprene so as to prevent it from contacting the boulder. I have attached a picture of the flywheel below.

[sanddrag]

Andrew, you say you had build days on MWF and Sat. Did the team still meet on the other three days of the week or did you really meet only 4 days per week?

[Cory]

Andrew, you say you had build days on MWF and Sat. Did the team still meet on the other three days of the week or did you really meet only 4 days per week?

We were very conscientious about only meeting those 4 days until week 6. We met more during the final week of build, went back to the 4 day schedule, and then did more like 5-6 as we got deeper into the season. We tried to make sure we left at 11 pm at the latest most nights, which we did a reasonably good job of during the build period and a less good job of as we got into competition season.

On the whole it was much better than previous years in which we worked 7 days a week the entire season, often until 2 am or later every Friday/Saturday.

[Michael Hill]

We were very conscientious about only meeting those 4 days until week 6. We met more during the final week of build, went back to the 4 day schedule, and then did more like 5-6 as we got deeper into the season. We tried to make sure we left at 11 pm at the latest most nights, which we did a reasonably good job of during the build period and a less good job of as we got into competition season.

On the whole it was much better than previous years in which we worked 7 days a week the entire season, often until 2 am or later every Friday/Saturday.

What prompted you to do that? Change of venue? Mentor/student burnout?

[Cory]

What prompted you to do that? Change of venue? Mentor/student burnout?

It's not sustainable and you aren't very productive when you've been there that many days in a row for that long each day.

[NWChen]

How was your experience lasercutting a bellypan from 1/4" thick ABS? I've read that ABS tends to curl and melt rather than vaporize under a laser.

[Torrance]

Andrew (or other 254 members), would you mind giving a general timeline of your season? Such as when certain robot decisions and milestones occurred?

This a question we get asked a lot and unfortunately we don't do a very good job of documenting this besides the build blog (which was largely incomplete and thus unlikely to be released this year).

I've attached a general timeline from 2016 of major subsystems (all times are for the end of that day/week). This was done mostly off of memory and the build blog was not consulted, so take it with a grain of salt.

[joemost]

I would love to hear more about the android app you guys used for vision.. thats such a cool idea

[aphelps231]

Awesome robot guys.

Will there be a build season blog released for this year?

[bkahl]

Awesome robot guys.

Will there be a build season blog released for this year?

Literally 2 posts above you...

This a question we get asked a lot and unfortunately we don't do a very good job of documenting this besides the build blog (which was largely incomplete and thus unlikely to be released this year).

[lnex1357]

.... the safety wire was wrapped once around the wheel, cut to its length, and then two ends were twisted together and then stuck inside the neoprene so as to prevent it from contacting the boulder. I have attached a picture of the flywheel below.

We are throwing some fairlane wheels on our shooter for an offseason event in place of our colsons. Did you guys use round or flat safety wire and what was the rough OD or width respectively, as I would prefer not to guess and check through a series of McM orders. Thanks so much!

[aphelps231]

Literally 2 posts above you...

Whoops, I searched the page for "blog" and got no results, but I must have made a typo (on my phone). My bad :o

[Chris Mounts]

How was your experience lasercutting a bellypan from 1/4" thick ABS? I've read that ABS tends to curl and melt rather than vaporize under a laser.

Can't speak for 254 but we've used ABS for several years now. We love the material but you are correct on the challenges of laser cutting especially at 1/4". That does not stop us though. We just run at a real low cut speed and get pretty clean cuts. Some cleanup is required.

For reference we use a WKLaser LC1280 which is a 150 watt laser. Going real slow we can make it through 1/4" ABS in one pass. Thinner material cuts without an issue.

[Chris is me]

How was your experience lasercutting a bellypan from 1/4" thick ABS? I've read that ABS tends to curl and melt rather than vaporize under a laser.

Not on 254, but lots of laser cut ABS parts on my robot this year, most from 1/4". It's not too hard to do, but it takes a little trial and error. Multiple passes, playing with the feed rate and power level, and making sure your air / ventilation is good are all good steps to try. After some tweaking (approximately 1 practice robot worth of parts tweaking) it was pretty easy to get a quick and consistent part out of the laser cutter. This made manipulator fabrication quick and easy for us.

[gc_coxen]

I may be mistaken but it doesn't look like there are CAMs on your bearing blocks to tension the chain. Did you tension chain or just find an optimal position that was permanent?

[Cory]

I may be mistaken but it doesn't look like there are CAMs on your bearing blocks to tension the chain. Did you tension chain or just find an optimal position that was permanent?

This is the same as last year. We did fixed center to center distance that was the nominal chain pitch plus some fudge factor (I think .015" ish added to each run, but I don't remember for sure off the top of my head).

[Monochron]

This is the same as last year. We did fixed center to center distance that was the nominal chain pitch plus some fudge factor (I think .015" ish added to each run, but I don't remember for sure off the top of my head).

I know this has been discussed a lot but can you explain why this works? How does accurately getting the fixed center to center distance remove the need for tensioning? Is there less stretch? Or what about loose chain normally does require tensioning?

[Starke]

Thanks to the Cheesy Poofs for continuing to inspire our students.

Would you be willing to explain the relationship between 254 and 971? Looking at 971's reveal video (https://www.youtube.com/watch?v=CMX4ynSQsyI&feature=youtu.be) this year, it looks a lot like 254's place (https://www.youtube.com/watch?v=aFZy8iibMD0) in previous reveal videos, while Dropshot premiered (https://www.youtube.com/watch?v=EguhIdvBDMA) in a different field.

[Cory]

At champs I was doing field reset on Newton and talked to Travis a bit about it. He mentioned that they have a better set up at their school and mostly work there now. I believe he also said they missed giving students the opportunity of working at a NASA facility which is an interesting point I never thought of.

So... yea that's what I have figured out from me digging around. Ill delete this post once someone actually from 254 gives a better response.

We have been lucky that our school is committing a lot of resources to their STEM programs, including FRC. This has given the team more resources on campus. We still have a strong partnership with NASA, as we always have.

971 has been an official "house team" for the last few years. I don't know if the robotics.nasa.gov link is current but it lists 842 for NURC, not FRC. 842 has never used the NASA lab.

254 has had a long running relationship with 971. We helped with a design review for them in 2007/2008 and have been close since then, often bouncing design or strategy ideas off each other, sharing prototype results, etc. In 2015 we collaborated on the design and manufacturing of our can grabbers for championships, which was a lot of fun.

[caume]

Are CADs for Dropshot available anywhere?

[Knufire]

Are CADs for Dropshot available anywhere?

254 historically does not share CAD.

[frcguy]

Are CADs for Dropshot available anywhere?

We have no plans to release the CAD of the robot but are happy to answer any questions you have.

See above.

[RoboChair]

The main purpose of the safety wire, as suggested by Team 1678, was to prevent our fairlane flywheel from expanding a significant amount past 5000 rpm. During prototyping, the fairlane wheels expanded to the extent that we were fearful of testing them out. As a result, the safety wire constrained the expansion of the wheels to a certain diameter which allowed us to ramp up to around 6000 rpm at Champs for taking shots. As for the process of installing them, the safety wire was wrapped once around the wheel, cut to its length, and then two ends were twisted together and then stuck inside the neoprene so as to prevent it from contacting the boulder. I have attached a picture of the flywheel below.

We are throwing some fairlane wheels on our shooter for an offseason event in place of our colsons. Did you guys use round or flat safety wire and what was the rough OD or width respectively, as I would prefer not to guess and check through a series of McM orders. Thanks so much!

Round safety wire 0.032" diameter. 1678 ran 2 wraps around our wheels. It's a little bit of a tricky process. You must get the safety wire tight and squeezing into the wheel a little and you will almost definitely break some wires in the process of twisting them. Try until you succeed To stuff the twisted wire end into the wheel use a screwdriver or awl to stab into the rubber right next to the twisted end, then stuff it in.

Attempted destructive test of a shooter wheel (https://www.youtube.com/watch?v=vOYEp6tjQDg)

[asid61]

Round safety wire 0.032" diameter. 1678 ran 2 wraps around our wheels. It's a little bit of a tricky process. You must get the safety wire tight and squeezing into the wheel a little and you will almost definitely break some wires in the process of twisting them. Try until you succeed To stuff the twisted wire end into the wheel use a screwdriver or awl to stab into the rubber right next to the twisted end, then stuff it in.

Attempted destructive test of a shooter wheel (https://www.youtube.com/watch?v=vOYEp6tjQDg)

I felt myself shying away from that wheel...
Out of curiosity, does it explode if you run it without the wire, and if so how did you find out?

[Cory]

I felt myself shying away from that wheel...
Out of curiosity, does it explode if you run it without the wire, and if so how did you find out?

For us it was less about keeping the wheel from exploding and more about the fact that since we retrofitted the wheel into the shooter, the expansion would cause it to rub dramatically on the turret plate, without being safety wired.

In 2014 when testing with the same wheels we wanted to determine how much they expanded and make sure they were safe to use at those speeds. We mounted them to a shaft held in a collet chuck in our cnc mill, spun them up to ~5000-5500 rpm with no safety wire and measured the difference in size at speed vs static and saw no issues with exploding. That's substantially slower surface speed than at ~8k rpm like Devin's test though.

[RoboChair]

I felt myself shying away from that wheel...
Out of curiosity, does it explode if you run it without the wire, and if so how did you find out?

We were having issues with delaminating wheels, which lets them expand far more and in a highly unbalanced way.

While I was trying to see if we could make it come apart it wasn't really the goal. The goal was to make sure that the wheel would not delaminate from the steel hub at a speed the shooter would never need to reach, it did not. The wheel was pulling well over 2000 times the force of gravity expanding outward in that test and nothing failed. It managed to handle around twice the stored wheel energy than what was required on the robot. The secondary effect of reducing the expansion of the wheel was just an effect of the wire resisting the outward force to a level that the rubber could handle.

Without the wire it would have delaminated or disassembled itself for sure.

Also, when you have that much energy stored in a disk the only places the pieces can go is the plane of rotation. So everyone was well clear of that plane with further room to move away. If something did fail the only damage would be to the ceiling tiles or the requirement of fresh pants.

[caume]

How is the drive gearbox attached to the chassis frame?

[Cothron Theiss]

How is the drive gearbox attached to the chassis frame?

I'm not affiliated with the team in any way, so take this with a grain of salt. But it appears from the close up of the gearbox that there is a screw on either side of the output shaft that was screwed from the inside of the chassis rail into the gearbox plate that is flush against the rail. It appears to be very similar to how the WCP gearboxes are attached.

[pilleya]

http://www.vexrobotics.com/bearingblocks-g.html

A custom bearing block, very similar to that of the WCP Gearbox bearing block.

[NotInControl]

So just a few questions from your friends on 2168.

1. Can you share a little bit more about how you arrive at shooter geometry (compression, contact time, exit speed etc.) required to make the shot. Every year these factors seem to be areas teams must learn from trial and error, wondering if the poofs have a more polished process.

2. Can you share more about what drove the Team to a turret all together, as far as I know this is the first turret 254 has used in competition. I am curious what drove the design, where did 254 pull the inspiration from if anywhere, did any team mentors/students have prior experience with turrets in FRC applications in the past? I find it typical for teams to avoid certain solutions because they have never fielded them in an event and would rather choose a solution they have more experience with. That definitely is always a good approach in my opinion, just wondering how 254 gets over that idea to follow a solution they never fielded.

3. Can you share a little more about how you determine whether to go chain #25, #35, or belt. This has been an age old question, and I am not really asking which you think is better, but how do you go about choosing which one for the application. The reason I ask is some teams use belt, and use it for everything, some teams use chain and use it for everything, and other teams kind of are in the middle, they use one, have failure, and use the other, and keep bouncing around. I am wondering if 254 has a more scientific approach to the choice because it seems like 254 chooses different solutions more purposefully.

4. Going back to the chain question. I recognize that in certain years 254 has went from belt to chain or #25 chain to #35 chain etc. When this occurs do you have to redesign your drive rails or are their certain considerations into the design that makes changing from one to the other easy without much modification? (i.e certain spacing common to all)

5. Your Vision on the Nexus was stated to come out of necessity due to the unreliability of the Tegra, I am curious if the android solution seems like something 254 would use in the future or if there are equal pros and cons to possibly look for another? We did use a tegra, and after soldering come caps off to make it boot reliably we did not have an issue with the board. But again thats besides the point, looking for 254's opinion on the next best solution. Could you share some pain points, or cons/hurdles which needed to be overcome before the android solution was put into practice. I am sure many teams are testing an android solution in the off-season (we may be one).

6. Can you share more on the servo solution? How did you ensure the servo was meshed properly and never skipped? We tried to use a servo this year for our articulating hood, but slippage was a big issue so we pulled it for a multi position pneumatic solution right before our first competition. Typically on this team if it failed once we never try it again. I am curious how 254 was able to have a successful servo implementation. Would you mind sharing which servo was used, and how it was interfaced to the hood and did you have any issues with slippage?

7. How was the hood angle determined from vision? Was it based on distance to target, center of target to center of camera frame, or some other method?

8. How many drivers were used this year for the machine? I have heard that some years 254 has 2 drivers, some years 254 has 1 driver with a bunch of automated stuff. Could you share what was automated, requiring little/no commands vs what was always manual for this years bot?

Thank you very much for the answers to these questions. Truly is awesome learning from you.

[ThePoopieBandit]

WOW!

[mman1506]

For us it was less about keeping the wheel from exploding and more about the fact that since we retrofitted the wheel into the shooter, the expansion would cause it to rub dramatically on the turret plate, without being safety wired.

In 2014 when testing with the same wheels we wanted to determine how much they expanded and make sure they were safe to use at those speeds. We mounted them to a shaft held in a collet chuck in our cnc mill, spun them up to ~5000-5500 rpm with no safety wire and measured the difference in size at speed vs static and saw no issues with exploding. That's substantially slower surface speed than at ~8k rpm like Devin's test though.

I guess it's only okay to use machine tools to spin up a shooter wheel when 254 does it ;) (https://www.chiefdelphi.com/forums/showthread.php?t=41670)

/S

[Cory]

I guess it's only okay to use machine tools to spin up a shooter wheel when 254 does it ;) (https://www.chiefdelphi.com/forums/showthread.php?t=41670)

/S

I can't remember what their setup was that my comment was in reference to, but we did this in a fully enclosed machine with no chance of any debris flying out of it in the event of the wheel disintegrating at speed.

[AdamHeard]

I guess it's only okay to use machine tools to spin up a shooter wheel when 254 does it ;) (https://www.chiefdelphi.com/forums/showthread.php?t=41670)

/S

Weren't you shooting balls with the lathe? requiring hands, etc... to be involved?

[mman1506]

Weren't you shooting balls with the lathe? requiring hands, etc... to be involved?

I'm just kidding, none of the people who were involved on 865 in 2006 are still on the team today nor is it something we would repeat.

We use the thread as an example of how not to post on CD.

[Jared Russell]

Whoa, this thread died before I saw these questions

So just a few questions from your friends on 2168.

1. Can you share a little bit more about how you arrive at shooter geometry (compression, contact time, exit speed etc.) required to make the shot. Every year these factors seem to be areas teams must learn from trial and error, wondering if the poofs have a more polished process.

Nothing too polished here, just prototype-driven iteration. We knew that our overall design concept would not result in a whole lot of contact time/wrap, so we made sure our prototypes convinced us that we could still shoot consistently despite that. We went through dozens of variants of our prototype to play with various factors.

Embarrassingly, the robot that we competed with at CVR shot nothing like our prototypes. We transferred over all of the geometry, contact materials, and speeds correctly, but our initial competition shooter could deform during the shot and did not cradle the ball as consistently (after driving over defenses) as we had hoped. We found out about these issues before the event, but did not have time to address them until SVR.


2. Can you share more about what drove the Team to a turret all together, as far as I know this is the first turret 254 has used in competition. I am curious what drove the design, where did 254 pull the inspiration from if anywhere, did any team mentors/students have prior experience with turrets in FRC applications in the past? I find it typical for teams to avoid certain solutions because they have never fielded them in an event and would rather choose a solution they have more experience with. That definitely is always a good approach in my opinion, just wondering how 254 gets over that idea to follow a solution they never fielded.

Even though 254 has never rocked a turret before, a number of mentors have used them while on past teams (ex. 973, 341, 190). We chose this design because we were more confident that we could quickly and accurately aim with a turret than by servoing a pneumatic drivetrain. The traditional wisdom is that if FIRST gives you a protected area to shoot from, you should build the simplest robot possible and shoot from there. But we figured that most good teams would do this, and moreover thought that shooting from the outer works would lead to congestion and more difficulty aligning. So we set out to differentiate ourselves from the pack. As it turned out, while we ended up being one of the quickest shooting robots on the field, other teams were able to optimize their outer works shooters to be nearly as good (at a cost of a fraction of the complexity).

3. Can you share a little more about how you determine whether to go chain #25, #35, or belt. This has been an age old question, and I am not really asking which you think is better, but how do you go about choosing which one for the application. The reason I ask is some teams use belt, and use it for everything, some teams use chain and use it for everything, and other teams kind of are in the middle, they use one, have failure, and use the other, and keep bouncing around. I am wondering if 254 has a more scientific approach to the choice because it seems like 254 chooses different solutions more purposefully.

4. Going back to the chain question. I recognize that in certain years 254 has went from belt to chain or #25 chain to #35 chain etc. When this occurs do you have to redesign your drive rails or are their certain considerations into the design that makes changing from one to the other easy without much modification? (i.e certain spacing common to all)


254 has never used belt in the drive, and had only used #25 chain in the drive (in the bumper era) until 2016. Chain is nice because it is easy to replace, easy to tension, cheap and modular, etc. We started our build with #25 chain in our drive, but knew that this year the tensile load would eat into our safety factor (small sprockets, big wheels). After busting a few chains on our practice field, we swapped out for #35 chain. The chassis was designed to support this contingency from the start.

On non-drivetrain mechanisms the team has used belt exclusively since I joined the team (on things like intakes, flywheels, and elevators). None of these have been super high load applications.

5. Your Vision on the Nexus was stated to come out of necessity due to the unreliability of the Tegra, I am curious if the android solution seems like something 254 would use in the future or if there are equal pros and cons to possibly look for another? We did use a tegra, and after soldering come caps off to make it boot reliably we did not have an issue with the board. But again thats besides the point, looking for 254's opinion on the next best solution. Could you share some pain points, or cons/hurdles which needed to be overcome before the android solution was put into practice. I am sure many teams are testing an android solution in the off-season (we may be one).

We would definitely consider going the Android route again (if a simpler solution doesn't make more sense...Pixycam is pretty sweet). A lot of the biggest hurdles were integration questions that we largely were able to answer. Adb port forwarding for communications (which allows charging over the USB cable), the fact that you get a screen and input device build-in, the availability of great APIs (seriously, Camera2 is awesome) and IDEs for development, relatively powerful hardware and a nice camera, and low cost...it all just makes sense.

Pain points were (a) figuring out the comms and power interface (including ways to make sure that you can unplug/replug the cable and reboot either side and have the link come back immediately); (b) physically mounting the thing such that the camera was facing the right way (phones are not designed for ease of mounting on a robot); (c) finding the most performant way to capture an image and process it (there are a bunch of ways available - we tried em all). Also, we noticed that we got lots of tearing in our images at times due to the camera being mounted so close to our flywheel (likely because of optical image stabilization capabilities...the camera is basically mounted on a tiny spring). Our vision code was able to deal with this, but it was a nuisance.


6. Can you share more on the servo solution? How did you ensure the servo was meshed properly and never skipped? We tried to use a servo this year for our articulating hood, but slippage was a big issue so we pulled it for a multi position pneumatic solution right before our first competition. Typically on this team if it failed once we never try it again. I am curious how 254 was able to have a successful servo implementation. Would you mind sharing which servo was used, and how it was interfaced to the hood and did you have any issues with slippage?


We used continuous rotation servos that drove a pinion along a curved gear rack on our hood. We used a separate encoder for feedback, so slippage wasn't a big deal. Someone else should be able to lookup the servo part we used (we also used a digital programmer to make sure that the servo stopped when the robot got disabled...it didn't out of the box!).

While this worked, it was a big pain in the butt. I wish there was a tiny, lightweight, low-speed motor in the kit last year appropriate for such an application and we could have used a Talon and been done with it. We burned out a lot of servos during testing while we tried to find the best ones, and still shredded gearboxes from time to time (typically when we would accidentally lower our hood onto a still-spinning flywheel, such as if we accidentally drove into the low bar).


7. How was the hood angle determined from vision? Was it based on distance to target, center of target to center of camera frame, or some other method?


We calculate the pose of the goal relative to the robot origin (where we started the match) for each camera frame. We then track the pose over time (keeping track of robot motion using encoders and gyro while tracking) so that the goal remains roughly in the same place during tracking. We can determine range by taking the distance from our shooter to the goal pose (both relative to robot origin). Of course our estimate of robot position (and therefore goal position) drifts significantly over a match (especially after going over a few defenses), but it doesn't matter since this error cancels out during aiming.

Once we know the range, we use a lookup table to determine hood angle.


8. How many drivers were used this year for the machine? I have heard that some years 254 has 2 drivers, some years 254 has 1 driver with a bunch of automated stuff. Could you share what was automated, requiring little/no commands vs what was always manual for this years bot?


2 drivers this year and every year since I've been here. This year the base driver controlled all things drive (shifting, traction control mode) and had the "fire" button (since the driver knows what he wants to do, this way we don't have issues pressing "fire" just as the robot changes direction). The operator was responsible for our utility arm (hanger and defenses manipulator), intake, and state of the turret assembly (low bar configuration vs. intaking vs. auto-aim). For shooting, the operator basically just holds down the auto-aim button until the driver shoots.

That's a lot of responsibility on the operator, so aside from auto-aim, we had a massive state machine for the robot to help automate transitioning from intaking to low bar, to shooting, to hanging, etc. The operator presses buttons that command a "wanted" robot state, and then the state machine transitions through the correct sequence of operations (ex. stop the flywheel, center the turret, bring back the hood, stow the hood, etc.) with the correct timing and/or sensor events to ensure that no matter how the operator console gets mashed, the robot always gets into the goal configuration as quickly and safely as possible.