Vex Challenge coach/mentor advice

The organization that promotes and runs our local FLL program is investigating what would be necessary to support a similar Vex program. We have a huge number of local FLL teams and only a few FRC teams so we are hoping a Vex program could provide a continuing path for those that would otherwise be facing a dead-end. My role is to try to determine what new Vex coaches and mentors (many but not all will be previous FLL coaches/mentors) will need and how we can best support them. I’ve spent some time with my sons working with the Vex hardware and developing software and have started to identify differences in the development process:

  • Large variety of LEGO parts used “as is” verses cutting and shaping limited number of parts to meet your needs.
  • Fully autonomous behavior verses limited autonomous behavior and R/C control.
  • Robolab/RCX which provides development of robust event and multi-threaded software verses Vex/EasyC/MPLAB (I’m still learning how to do some of the more complex behaviors with C/Vex that I could do with Robolab/RCX).

So, I would like input from anyone who has coached or mentored a Vex team on what to expect and what resources a local organization could provide to make you more successful (workshops, etc.).

Thanks,
-Glenn

I would say become good friends with your local RadioShack, but they no longer will continue to sell Vex merchandise, bah. So, if IFI recruits a new retail outlet for Vex, become good friends with your local branch. Get a discount if possible (many stores offer educational discounts to organizations run by schools as well, be use to take advantage of those as well). Other local organizations can provide monetary funding is always helpful, but other contributions can help to. A local restaraunt may provide coupons or catering to your team, a local Kinko’s or other copying place may allow free/discounted printing and copying (great for producing advertisment material for at the competitions, community outreach, etc.), or plenty of other things.
While the bare minimum hardware recquired is only 1 Vex starter kit, we have found that you will need much more to build a competitive robot. In the 2 years we have competed, we used 8 motors in 2005, and 7 this year. This year, we also used about 2 hardware kits worth of metal, a tread kit, a chain and sproket kit, 2 additional all purpose wheels (beyond the 2 issued in the Starter kit), and a programming kit, 2 vexlabs rubber bands, and vexlab grip treads. We also found that having a hacksaw, dremel, vice, plenty more allen wrenches, wire cutters, pliers, and hammer were useful for when we had to modify parts (although, it is possible to build a vex bot with limited or no modification to stock pieces, like this bot (which only had a couple bends, done by hand ). For when producing the final product (we’d recommend at least some prototyping of components, particularly any actuated joins and sensor mountings), use loc-tite (we used purple) and/or the vex nylon lock nuts. The crown nuts have been known to fall off during the intense competitions.
I do not know of any official vex workshops in your area, but there are vex camps in New Hampshire, and run by a few FRC and FVC teams around the country designed for kids. I’m also positive that you can find a mentor team to help you with any problems you do encounter, and can also provide various tricks they learned to help them with their season, from generic design procedures, to outreach, right down to how to fasten a nut.
I hope that helps, and if you have any other questions, feel free to contact me.

One thing that we had to adjust to is that it takes A LOT longer to assemble something with Vex than Lego. For example, we wanted to lengthen the robot to accomodate a longer drive train, which took 5+ hours, including disassembling, splicing, cutting, filing, reassembling, and repeating this process twice before we got it right. Doing the same with a LEGO robot took about 20 minutes. With Lego, much of our kids’ learning was done by trial & error - they’d try something, take it apart, reassemble, and try 6 new configurations in a half hour. With Vex, guided instruction is more essential, because each trial takes so long. We would have loved to have a training course.

I would recommend that each team purchase at least 2 starter kits. With 2 robots, teams can compete with themselves with simple mechanical challenges that don’t require much field assembly: tug of war, speed races, basketball (lop a ping pong ball into a waste basket), bowling (knock down a maximum number of 2-liter bottles in a desired configuration), simple mazes with butcher paper and electrical tape.

Yolande

There were several Vex presentations at the 2006 FIRST Robotics Conference held in Atlanta in April. The presentations can be found at http://www.usfirst.org/robotics/2006/Workshops/wrkpresentations.htm

Thanks everyone, this is exactly the type of info I was hoping for.

Great point. I’ve been thinking that using CAD software might help (I’ve been a user and designer of EDA software for many years). I’m hoping that it would help the designers work out some of the construction issues and identify the Vex parts to be used (and what modifications - cuts, bending - might be needed). Is CAD software available for FVC teams through a similar program as for FRC?

Thanks for bringing this up. In FLL, all the teams I have seen have access to a playfield for practice during the development season (low cost and small size). It really lends itself to the iterative nature of LEGO robot design. For Vex (do to larger cost and size of the playfields), do most teams build a mock-ups of some of the field elements and practice with them “piece meal”? Build full playing fields? Have a shared, community playfield that everyone can schedule time on? Can anyone share their experiences with any of these options (or others)?

Thanks,
-Glenn

There is a large library of vex parts already drawn for Inventor at www.vexcad.com

Currently, FIRST does not supply FVC teams with Inventor software. Hopefully, they can reach an agreement with Autodesk to supply at least one seat to each registered FVC team in the future. I’d contact your local FRC teams who should have several seats on Inventor installed for their teams use. They should be able to assist with training and possibly mentoring FVC students at the FRC teams location.

The playing field components will be available through www.vexlabs.com. FIRST is working with IFI to keep the cost of an official playing field around $1000. While this may seem high, most of that cost is for the playing field walls which should be reusable for at least a few years (FIRST has promised that playing field dimensions shouldn’t change for ‘several’ years), similar to the FLL plywood and 2x4 playing field. If you have multiple teams in your area, they could share the cost of the playing field walls and share use of the playing field during the build season. Once you have purchased the playing field walls, each year’s playing field components should be able to be constructed for under $500, which isn’t too bad for official field components. Low cost components could be built for even less. Another nice feature is that teams can buy a ‘half field’ kit which gives you the wall components for half of an official playing field for about $400. This is the route that our team took this year. We’ll probably buy a second half field kit next year so that we’ll have a full field to use for local competitions and demonstrations. Most FVC field components are available “Ala Carte” from IFI so you only have to purchase the components that you can afford or need.

As far as extra time needed for cutting and bending of metal components. Just one big word of advise - NEVER throw out any metal components. Keep everything because sooner or later you’ll need the exact same custom piece on another robot. At WPI they have been working with the vex hardware for quite some time so they have a large box of pre-cut pieces from old projects. Before a student cuts a piece they are instructed to check that box first. Chances are they find a piece ready to go, saving both time and money. :wink:

Good Luck with Vex!

There are several CAD models of Vex parts out already. Vexlabs does not have the complete library up. See

It shows you a Carnegie Mellon site to get almost all the Vex parts in Autodesk Inventor and Solid Works. I have just recently completed several more models and they should up soon as well.

Also, you can constuct a majority of the field with wood and other common materials from your local home improvement or hardware store. This year we built a quarter-field, and the only piece we bought from Vexlabs was the auto loader (the rest we made from plywood and foam matting). This was also the size of the divided autonomous field for this year’s game, so it allowed us to test our auto modes, and do some driver training for the operator controlled matches.
Also, even though it still takes significantly longer to build and rebuild robot features and systems, it is still significantly easier than it will be if the students go on to FRC, and it is quite feasable to rebuild and redesign features during the season, or even in a krunch, at competition. We have typically found a mix between general designing and trial and error. We first create a general design concept of how we want to play the game, what mechanisms we can use to acheive that, and can we build the mechanisms (do we have enough motors, are they too complex, do we have the parts, and are they too big?). After that we come up with some simple drawings, but we often leave specific gear ratios and lengths up for trial and error, identifying which ratios and sizes work best for each situation. Thus we go with fairly easy to repair and rebuild designs. This also leads to a longer build period, but it helps us acheive the most from our design. We spent several hours during one weekend working on our “shoulder” design this year trying different gear and sproket ratios until we found one that could lift our arm in a reasonable amount of time. It all depends on how much time your team has to build and test before your competition.