10-10-2009 21:44

Jared Russell

Re: pic: Wild Swerve Demo Chassis

How much does this weigh?

10-10-2009 22:32

Lowfategg

Re: pic: Wild Swerve Demo Chassis

So each module is driven by a window motor for turning? Since we only get two of the Denso motors in the kit (in past years), what motor is turning the other two modules? From the picture it looks like you are using four window motors.

10-10-2009 22:58

IndySam

Re: pic: Wild Swerve Demo Chassis

This is just a demo bot, I doubt they were concerned about that.

11-10-2009 00:33

Dr Theta

Re: pic: Wild Swerve Demo Chassis

Looks like a beautiful swerve system. Kind of random question, where did you get the material that you used for the frame? I want to advocate using this sort of frame construction with our team this year.

11-10-2009 01:11

EricH

Re: pic: Wild Swerve Demo Chassis

Looks like 80/20 extrusion. There are many places to get it. The advantages are ease of modification and use. The disadvantages may include (note: may) having to readjust where that front frame rail [or other frame piece] is after every match due to fasteners. There are ways to get around that one, though.

11-10-2009 08:28

Tom Line

Re: pic: Wild Swerve Demo Chassis

To reiterate what Eric H said - 80x20 is problematic at times because the fastening system that it uses is simply not meant to withstand repeated bot collisions, etc.

My team used 80x20 for their bot their rookie year in '06. They resorted to using a sledgehammer between matches to force the bot back into shape by championships (and had to retighten every fastener between each match).

11-10-2009 09:41

Jared Russell

Re: pic: Wild Swerve Demo Chassis

341 usually gets around this by using T-bolt fasteners for prototyping, but once the final design has been locked down we drill through the extrusion to make solid connections that don't budge.

The only other drawback of 80/20 (and Bosch extrusion, which is what we use) is that its strength to weight ratio is about 20% worse than for 1" square (.125" wall) tubing. For our team we are willing to eat this extra weight for the flexibility (and ability to avoid welding) that extrusion gives us.

11-10-2009 17:20

ajlapp

Re: pic: Wild Swerve Demo Chassis

It came in around 100 lbs. The 80/20 extrusion is quite heavy.

This is not a FIRST robot. It was built to a customer specification. As a result they chose to use four AM Equipment motors. They are very similar to the kit motors.

AM Euipment Window Motor

That said, the steering modules pictured are designed to interface with either kit window motor or a globe motor. These will most likely be a part of our FIRST product lineup for 2010.

11-10-2009 22:22

Raul

Re: pic: Wild Swerve Demo Chassis

Besides that, trust me, it is a major pain to write SW to control 4 individually steered modules.

I suggest anyone doing crab/swerve should steer at least two wheels together with each globe motor. Either the fronts and backs together, or the sides together, depending on what type of flexibility you need for your driving strategy. For example, in 2008, having the two fronts tied together and the two backs tied together allowed what we call monster truck steering easily around the tight hairpin turns.

Last year, 2009, we tied all 4 together for the first time since the low traction surface made it moot to control them separately.

11-10-2009 23:02

ajlapp

Re: pic: Wild Swerve Demo Chassis

This particular customer was interested in designing a platform that would tax their product and put heavy demand on their technology.

They eventually plan to put a different motor at each wheel to further increase the challenge.

Its been done before, Chief with tank tread swerve, independent steering at each wheel and a different steering motor at each location. One of them may have been a seat motor. If memory serve me. Circa 2001.

11-10-2009 23:06

Chris is me

Re: pic: Wild Swerve Demo Chassis

469 also had an 8 motor (non-coaxial?) swerve this year. They certainly had manuverability to play efficient defense, though I don't know how much of that was due to independent swerve steering; 111 was in my mind just as mobile.

17-10-2009 08:09

Don Wright

Re: pic: Wild Swerve Demo Chassis

Actually, this was the first year we didn't have 8 motor swerve and did 4 motor coaxial. We had 8 motor swerve the last two years (2007, 2008)...