[Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

This week, we’ll be talking about mechanism design with our three awesome guests:

Lucien Junkin: from FRC 118 on Intakes
Allen Gregory: from FRC 3847 on Shooters
Adam Heard: from FRC 973 on Arms

These long time mentors are going to share their years of experience with all of FIRST on how to design effective mechanisms from a non-game-specific perspective.

Drivetrains are always the most popular project to try in the off-season, mostly because it's really hard to design a mechanism without knowing the game. Our guests are going to show you the basics you need to know about shooting, collecting, and manipulating objects for whatever Stronghold throws our way. Don't spend the first week of build season relearning how to collect, pickup, or score. You will not want to miss this hour-long show!

We want to hear questions from the community, so send them in via any of the following methods:

Email: btl@frcgamesense.com
Twitter: Tweet with #FRCBTL
GameSense Twitch Chat: Type "!question", followed by your question and our chat bot will automatically send it to us during the show!
Chief Delphi: Post your question in this thread!

Join the GameSense crew and our distinguished panel of guests Wednesday at 9 PM ET at frcgamesense.com, twitch.tv/FRCGameSense, or youtube.com/FRCGameSense.

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

I am looking forward to this as this covers an area that my team has struggled with in the past. I hope that I will learn something new from this broadcast, I can't wait.

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

Just a reminder, the show is TONIGHT at 9 PM ET. Lucian's got a pretty sick setup at 118 HQ that you won't want to miss!

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

This episode is going to be pretty dope.

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

We agree! It goes live in just a few minutes. Tune in at frcgamesense.com, twitch.tv/FRCGameSense, or youtube.com/FRCGameSense.

Don't miss it!

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

Enjoyed it. Well worth the time to watch.

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

Good to see #TeamTexas representing! Awesome presentations!

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

Great presentations, I especially liked watching Lucien's football demo and 118's prototype video.

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

I really enjoyed this one! Does anyone have any information about the drill trigger setup that 118 uses? I remember seeing plans for it a while ago but can't seem to find them now.

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

Lot of teams use them, they are very easy to build. Just open up a 12v drill (118 uses 18volt drills sometimes but that's a bit risky with some motors) and remove the motor. Connect the wiries to Anderson connectors or some other quick dissconnects. This allows you to change the speed and direction of whatever motor connects to it.

We use a small makita 12 volt drill that we broke the chuck off of and a cheap 12 volt model from Walmart that we bought specifically to use for that purpose.

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

It is really simple. Get a 12 volt drill with variable speed(old ones with burnt out motors are fine). Remove the motor, gearbox, chuck, etc. All you are left with is a handle with a switch and battery contacts. Wire your connector of choice to the output of the trigger (Where the motor used to be). That's it.


The advantage of this is you get the right voltage (assuming a 12 volt battery), variability in speed that is easy to control, and reversibility (without removing the wires.

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

Here's a great video tutorial created by team 1939 The Kuh-nig-its on how to convert a drill.

http://youtu.be/3q4nHCzSer0

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

I got around to watching the video this morning. Thank you all for the time and effort put into this one! There are some great tips here. I really appreciate the prototyping philosophy presented by Lucien. Lord help us if it's a high-throughput football game.

The arm and shooter bits were great too. In particular Adam's history of arms in FRC should help younger teams understand where they may excel compared to elevators in certain situations. Then there's the theory of crashing on purpose (ha). And the details in the wheels for shooters and their prototyping still show me (at least) that there's still a lot to be learned by veterans who watch these videos.

The only thing I feel is missing from the shooter portion is a tip about design of experiments: if we're trying to figure out the "best" wheel, account for larger wheel edge speeds by slowing the motor down. Of course the 8" wheel will do better at the non-adjusted speed, even if the grip/wear is a quite a bit worse than its 4" counterpart.

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

We were pretty short on time so I couldn't really do any of the simple math required for figuring out your ideal exit velocity, etc. Larger wheels may not perform better if you don't have enough torque to keep them going. Direct driving a larger wheel at to high an rpm will have much worse results than with a smaller wheel especially if the wheel slips on the game object instead of transferring energy. This is why linear shooters in 2013 had to start with slower spinning wheels and increase the rpm of subsequent wheels/motos. Also your overall strategy and packaging goals (how much room you have for your shooter) will play a role in wheel diameter selection as well.

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

Awesome episode. Going to make my whole team watch.

Thanks so much for this.

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

Be warned, the really cheap ones can "burn up". did this with some $10 specials. It worked really well for a while then fried itself.

Thanks for the reminder that I need to make a couple new ones.

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

I'm interested in learning a bit more about shooters as our team hasn't had to do anything with flywheels just yet. The wheel selection was well presented, but I just don't understand 254's robot in 2014 could fire the balls with a shooter! Considering the speeds and torques the 2012 motors ran out, it boggles me that the yoga balls could be fired with significant speed. Allen, do you have any resources pertaining to the deeper physics involved with shooters?

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

Also like Lucian mentioned in the video adding fuses will help your prototyping and increase the safety of using these devices.

A cheap fuse holder can hold a snap action breaker too. We purchased a few of these to add to ours.

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

The Poofs do a great job of explaining their development process each year. Their build blog and technical binder are available on their website.

One suggestion is to go back and read some of the early season threads from previous shooter games. Each year we as a community learn a bit more.
2013 small wheel linear shooter design for example.

Another suggestion is the behind the design series. The 2006 book is getting hard to find but it's a great read.

The Fighting Pi posted some great Behind the Design articles for a variety of awesome 2012 robots.

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

Awesome, thanks. I wish we didn't throw out the rest of the drill that we took the gearbox out of last year. :(

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

Does anyone know where I can get the power point that they used in the video as it had some great info. It was a great episode and I learned a lot, thanks!

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

Here

Here are a few more.

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

Our engineering journal for the 2015 season can be found here.

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

Here's FIRST's archive:
http://www.firstinspires.org/resourc...hind-the-lines

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

I just reviewed the video again. Lucien mentioned a "magic rubber strip tape". What is that and what is it used for? Any links to where to buy it?

Thanks.

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

This is from memory from a few years ago but I believe it's 3M self sealing tape. Something like this but someone from 118 can confirm it.

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

Not from 118, but can confirm that it's linerless electrical rubber tape. I took a picture of it to remember what it was when I was talking to them once, because I knew magic tape wasn't going to help me find it later.

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

Rescue Tape?
http://www.rescuetape.com/

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

The picture I took specifically says it's rubber tape and not silicone. I can't imagine you'd need the high temp resistance (or the cost) that would go with the silicone tape.

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

OH! that comes in various permutations from 3M, and googling "rubber splicing tape" brings up a lot of options.

What's the difference between it and normal electrical tape?

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

Electrical tape is vinyl, not rubber, for what it's worth.

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

I'm pretty sure this also doesn't have any adhesive on it. It basically only sticks to itself.

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

It's also a lot thicker than regular electrical tape and stronger. It also has a good tacky texture to increase its coefficient of friction with most materials.

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

double post

Re: [Behind the Lines] Ep. 5 Mechanism Design with 118, 3847, and 973!
 

It sticks to itself then fuses over time into a continuous mass. The ones I have used did not have adhesive and would stick to itself due to "tackiness".

It is also called "self amalgamating tape". It is used to create a continuous electrically insulating "coating" on objects that were not previously insulated and are inconvenient to apply insulation to using "normal methods".

A mechanic I used go to in Toronto used self amalgamating tape to replace the insulation on part of a wiring loom in my car where it had dried out and crumbled away, causing all kinds of shorts. We use the silicon type to cover up the bolted joints in the insulated bus bars, to get continuous insulation, in some of the large industrial electrical equipment built in our plant at work.

http://solutions.3m.co.uk/wps/portal...gamating-tape/