Team 254 Presents: Dropshot Technical Binder 2016

[Cory]

Originally Posted by 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?

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]

Originally Posted by Cory

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]

Originally Posted by Michael Hill

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]

Originally Posted by 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?

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]

Originally Posted by aphelps231

Awesome robot guys.

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

Literally 2 posts above you...

Originally Posted by Torrance

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]

Originally Posted by Ashwin Adulla

.... 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]

Originally Posted by bkahl

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

[Chris Mounts]

Originally Posted by 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.

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]

Originally Posted by 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.

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]

Originally Posted by 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?

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]

Originally Posted by Cory

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?