[FTC]: Drive Platform- Design Exercise

[orangemoore]

Originally Posted by DavisDad

Where's the term churro come from?

The bars running across the mountain are known in FRC as a churro.
http://www.andymark.com/product-p/am-churro.htm

[wgardner]

Originally Posted by orangemoore

The bars running across the mountain are known in FRC as a churro.
http://www.andymark.com/product-p/am-churro.htm

Yeah, but they're called a churro in FRC too because they're just like the mexican dessert. It's not like FRC came up with the term out of nowhere.

[DavisDad]

Here's a revised version of the drive platform User Requirements document: FTC 2016 Drive Platform URS-Rev1

[orangemoore]

Originally Posted by wgardner

Yeah, but they're called a churro in FRC too because they're just like the mexican dessert. It's not like FRC came up with the term out of nowhere.

I was just trying to explain the origin of the term that most FTC teams wouldn't know about.

[GeeTwo]

Originally Posted by orangemoore

I was just trying to explain the origin of the term that most FTC teams wouldn't know about.

Really? Are there that many FIRST teams in places without Taco Bell or Panchos? I know they aren't "real" churros, but when I read the name on an AndyMark parts list, I knew sort of what to expect. Maybe if the world were a bit more like Demolition Man, where "all restaurants are Taco Bell now"...I'd still like to know how the three seashells work without massive chafing.

[orangemoore]

Originally Posted by GeeTwo

Really? Are there that many FIRST teams in places without Taco Bell or Panchos? I know they aren't "real" churros, but when I read the name on an AndyMark parts list, I knew sort of what to expect. Maybe if the world were a bit more like Demolition Man, where "all restaurants are Taco Bell now"...I'd still like to know how the three seashells work without massive chafing.

What I mean is that in the post that was first questioned about the term "churro" came from. (To my knowledge) he was asking what a churro part was and not the actual piece of food.

But hey, I might be totally wrong. Because we seem to be talking about two different issues. I am talking about what the actual part a churro is. While everyone else is talking about the food term and what type of food it is.

[DavisDad]

Drive Platform Design Strategy

My son and I have been thinking about this season's game vs. drive platform design. The "Mountain" element provides new and difficult challenges that are very different from previous years. Here are some of the issues we've been thinking about:

1. Scoring- The scoring capability related to drive design is challenging related to climbing the mountain. We estimate that purely driving/climbing ability can score 80 points by driving up to the "Mountain High Zone" (40 autonomous & 40 tele-op). And... if the robot can climb to the High Zone, we'll be able "hang" using fairly simple mechanisms (80 points hang & 20 points "All Clear Signal"). So... climbing could affect a total of 180 points for the team.
   
   
   
   
2. Drive vs. Climbing- To climb into the High Zone, the robot has to climb the 30 deg angle ramp and drive over the "churros" (rungs), and then climb the rungs at 50 deg. We're thinking of the High Zone as a ladder leaned at a 50 deg angle with rungs spaced at 5.33" intervals. Possible drive types:
   • Standard 4" wheels- will fall through the rungs
   • Big wheels- approximately 8", wheel base is only about 8" and center of gravity (COG) must be low or robot will flip. Wheels could "trip over" debris; hindering autonomous navigation.
   • Tank treads- much more complex system to design than wheels.
   
   
   
   
3. Physics- Any wheel or tank tread design will not have enough friction to climb at 50 deg with smooth contact with the rungs (assume < 1 coeff friction) . The treads or wheels must be able to "grab" the charro or the charro's ribs. The power required to climb 50 deg is much higher than previous years’ 15 deg incline. It’s complicated, but we’ve done a rough estimate for a 30 lb robot with wheels, and got about 500 in-lb torque at each axle.

[DavisDad]

Big Wheel Design

We did some design and testing. We modeled the AM-0420 8" Wheel with an automotive "cogged V-belt", model # AX-23. The idea is that the belt will be flipped inside out and snugly fit the wheel OD. We're thinking well cement the 2 rubber surfaces together.

The auto parts store didn't have this small a fan belt, but I got a longer one with the same cog pattern and cross-section. We mocked up the 50 deg angle with a churro at the correct alignment, rigged the belt around an 8" wheel and rolled the wheel per design by hand. It felt like it should work; worked well enough that we ordered 4 wheels and 4 belts.

[Gdeaver]

Time to review the concept of center of mass with the students. Both static and dynamic. Saturday we let the students go on design for different aspects of the game. Half way into the meeting, we gave them a power point presentation on COM that we give the FRC students. After a little playing on the mountain with this summers practice bot, the concept of COM really sunk in. We can "crash" the practice bot up the 30 degree slope. To drive up the 50 degree slope is challenging.

[GeeTwo]

Originally Posted by orangemoore

What I mean is that in the post that was first questioned about the term "churro" came from. (To my knowledge) he was asking what a churro part was and not the actual piece of food.

My quote then was a response to the side discussion about familiarity with the food. I fully understand that the original question was about the aluminum stock, not the fried dough. My point was that if you are familiar with the food, you wouldn't ask the question about the aluminum.

Originally Posted by DavisDad

Big Wheel Design

We did some design and testing. We modeled the AM-0420 8" Wheel with an automotive "cogged V-belt", model # AX-23. The idea is that the belt will be flipped inside out and snugly fit the wheel OD. We're thinking well cement the 2 rubber surfaces together.

This looks like a great solution - if you can find the right pitch timing belt, it should interface well with the churros even at the steep angle. If rubber cement doesn't do the trick for you, you might want to check on glues meant to hold a patch in a tire. These glues are usually painted on, set in place, and then partially burned to form a solid joint. Of course, I suggest doing the burning outside, on a metal pad, away from other combustibles, with a class A+B fire extinguisher handy just in case things go awry.

Originally Posted by Gdeaver

Time to review the concept of center of mass with the students. Both static and dynamic. Saturday we let the students go on design for different aspects of the game. Half way into the meeting, we gave them a power point presentation on COM that we give the FRC students. After a little playing on the mountain with this summers practice bot, the concept of COM really sunk in. We can "crash" the practice bot up the 30 degree slope. To drive up the 50 degree slope is challenging.

Thanks! I'll incorporate a bit of this into our FRC pre-season training this year.

[DavisDad]

Originally Posted by GeeTwo

... - if you can find the right pitch timing belt, it should interface well with the churros even at the steep angle...

I have one of these arriving tomorrow:

Gates 255L050 PowerGrip Timing Belt

[manojkr]

Thanks for all the information on this thread. We are a rookie team of 6 with mostly 7th graders this year. While the team is starting to use PTC, I came across this thread and got quite interested in onshape. We are using tetrix kit. Are there tetrix models available on onshape? How does that work? Thanks in advance for the help.

-Manoj
FTC 10295 - Yellow Jackets

[DavisDad]

Originally Posted by manojkr

...Are there tetrix models available on onshape? How does that work? Thanks in advance for the help....

Hi Manoj,

Yes, there are Tetrix as well as Modern Robotics Inc. and Matrix models that have been added to OnShape. You asked: "How does that work?" Are you asking about how use OnShape? Or... specifically how to use the "Public" models at the OnShape site?


Craig

[cadandcookies]

Looking at that spreadsheet, I might consider re-reading the rules. To my knowledge you cannot score points for both hanging and parking in the high zone during the same match-- see 1.5.3-4 in the Game Manual Part 2.

I'm also interested in your numbers for debris scoring-- were you able to fit 20 pieces of debris in the goals? My team isn't meeting again until Thursday, so I can't check this myself.

Thanks, and have a great season!

[DavisDad]

Originally Posted by cadandcookies

...you cannot score points for both hanging and parking in the high zone during the same match-- see 1.5.3-4 in the Game Manual Part 2.

Hmm... looking at the scoring table in Scoring Summary 1.7, it looks like you can. I don't understand what 1.5.3.4.e means: "e. Cliff Zone: See End Game scoring". But... we'd be in the "High Zone", not the "Cliff Zone", at the end of Driver-control period.

...were you able to fit 20 pieces of debris in the goals? ...

We haven't set up the field; just eye-balling it from the CAD models.