Team 254 Presents: Dropshot Technical Binder 2016

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

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.

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!

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.

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.

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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.

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.

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.

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

Which solenoids/manifolds are you guys using on dropshot?

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

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.

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.

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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.

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.

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, 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. 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.

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.

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?


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