Team 254 Presents: Dropshot Technical Binder 2016

[Kevin Sheridan]

Originally Posted by Ashwin Adulla

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.

[TheModMaster8]

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

[frcguy]

Originally Posted by Kevin Sheridan

Heres a picture of my favorite prototype this year.

That's awesome

[Travis Covington]

Originally Posted by TheModMaster8

could i get a reply to my question??
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]

Originally Posted by bigbeezy

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]

Originally Posted by roboruler

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]

Originally Posted by apache8080

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]

Originally Posted by ThemisH

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]

Originally Posted by 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 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]

Originally Posted by apache8080

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]

Originally Posted by 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?

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