So my last few posts have been very Vex centric, so I figure my next one should focus a bit more on FRC. With 2011 slowly approaching, now’s a good a time as any to review and analyze the design of the 2010 drivetrain. I was tasked with picking out the gearing for it, but it was designed before I got there so I basically got to say what to do with the Toughboxes and the sprockets. What I’m trying to say: It wasn’t my fault. 😛 That being said, we had a nearly problem free drive all year, with the only failure being when a wheel got stuck in one of the chains of the goals. Our speed and acceleration were good and we had no structural problems.

However, I still think there’s room for improvement.

So here’s the drivetrain…

Shaker drivetrain

Drivetrain with some electronics thrown on it to make it go.

Drivetrain Printed Render

Nicely shows how the sides were connected.

Problem 1: Weight. While weight wasn’t much of a concern for Shaker this year, there were numerous ways we could have made it lighter. First, we had no chain reduction whatsoever, so we wasted about a pound overall not direct driving a wheel. Secondly, we could have very easily used 4 inch wheels instead of 6 inch wheels. This saves something like a pound and a half just in wheels, plus with a different gear reduction you cut weight just a bit as well. (If you wanted to stretch it, we could have used a single gear reduction and chain for the second stage, but we would have needed a custom transmission). Also weighty was the sideplates. Unpocketed 1/4″ AL didn’t weigh THAT much, but we could have done 1/8″ and just made some crappy flanges on our hand brake. (They didn’t need to be precise!) Overall, we could have easily knocked off 5 pounds from this drive before any serious lightening efforts (25 chain, lightened gears…)

Problem 2: The cross section. All of the support for the drivetrain was on top because we wanted to leave as much freedom for the kicker team as possible, but the side effect of that is that the drivetrain had a terrible shape. Essentially it was an upside down U. Bottom supports would have made it a lot more rigid and better able to stand up to side loads. I imagine we could have made a 1/2 standoff with a 1/4″ bolt through hole in it, and tapped a piece of 80 / 20 between two axle bolts to use as a cross support. Or we could have just put one somewhere… anywhere.

Overall, it was a pretty great drivetrain that taught Shaker a lot of lessons. We survived our first custom high traction drivetrain. And we know how to do it differently next year!

Next up in the CAD directory: A 4 inch wheel drivetrain in a similar style to this one. It’d be up by now if my hard drive was intact.

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