# FRC 95 The Grasshoppers 2024 Build Thread

Related to the above testing, and all of our prototypes, I always had an intuition that ‘full width rollers’ were a bad idea. My mental model said that full-width drivers would distort or collapse the note* but I couldn’t explain why in a technical sense. And like my momma always said: “if you can’t prove it and show your work why should anyone believe you?”**

So this morning, I did.

This free body diagram makes the assumption that the note is a loop of rope or chain, i.e. only a tensile member and incapable of supporting any bending load. Obviously this is not completely true, but it’s probably closer to the truth than assuming the note is rigid like a frisbee.

This FBD indicates that as the infinitely floppy note is driven closer to the outside the more force from the shooter is converted into force accelerating it down-range. We can make some logical leaps from these results:

• Single-sided shooters (like configs 1, 2, and 5 from earlier) should have a contacting solid backer on the non-drive side so the note doesn’t pop out of the drive wheels (see configuration 1 flub in HSV)
• Full-width rollers are not super efficient and commit significant energy to distorting the note (see configuration 7 in the HSV)
• Driving from the narrowest wheels, situated as wide apart as possible, will likely result in the best shooter performance overall (assuming contact time and traction are sufficient)
• Configurations like 4 and 6 will add power AND support the note from lateral deflection AND add spin. This is evident in configuration 6’s increased power.

*I think @Bjorn @Justin_Foss and co. have a lovely freeze-frame of a note going full-hotdog, but I can’t for the life of me find it.
**Nearly a verbatim quote from my mom when explaining why I needed to show my work in Algebra.

Addition: here is a good image from Team Scream’s build thread that shows how the notes get laterally distorted during shooting.

https://www.chiefdelphi.com/uploads/default/original/3X/f/2/f205c1c4ff478239adc58f824c42d0d51d02b311.jpeg

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