pic: Final 2011 Drivetrain

[poohbear]

loading photo ...

[RMS11]

Is this a teaser? Can we get some explanation? Are the wheels to be omni in the future?

[nighterfighter]

It looks really small. Really small...

[Andrew Remmers]

No gearboxes?

[GGCO]

Huh....

[ttldomination]

Originally Posted by nighterfighter

It looks really small. Really small...

Each CIM is about 4.3" long. Seeing as that model looks can it hold 4-5 CIMs end to end, I don't think that thing is more than 20" long.

- Sunny

[Kevin Sevcik]

Originally Posted by nighterfighter

It looks really small. Really small...

You think that's small? If those are CIMs, that thing is pushing right up to the edge of 28" wide, actually. I'll grant you it's not the full 28"x38", but I'd never call that a small robot.

[poohbear]

Hey comrads!

Here's our team's final design for our first drivetrain ever and its pretty innovative if i say so myself

-the body is milled from a solid block of 7071 aluminum (with our sponsor's five axis mill) to retain the maximum structural strength.
-the wheels are decagons instead of circles. NOW can we squeeze in more than tangential contact every tenth of a rotation, therefore we get more traction.
-the wheel formation allows for no "getting pushed around" and great defense. We might be the rookies, but thanks to our ingenuity, we're not going to get bullied on the field
-these four wheels are directly driven by CIMs so we can zip across the field at 154 fps according to JVN Design Calculator (great tool by the way guys).
-the bot fits in a 26x26 square. its octagonal shape allows for surface area for electronics.

I know its pretty good, but what are some design tips you veteran teams might want to bestow upon us?

P.S. The manipulator is coming soon with just as much innovation as you see here. Watch out for team 3815!!!

P.S.S. We would like to thank our professional mentors for their wisdom and guidance in designing this beastly beauty.

[AllenGregoryIV]

Welcome to CD, that is a pretty good first post if I have ever seen one. I thought 15.4 fps was going to be fast this year but you guys are taking this to whole different place (value).

[Joe G.]

Originally Posted by poohbear

-the body is milled from a solid block of 7071 aluminum (with our sponsor's five axis mill) to retain the maximum structural strength.
-the wheels are decagons instead of circles. NOW can we squeeze in more than tangential contact every tenth of a rotation, therefore we get more traction.
-the wheel formation allows for no "getting pushed around" and great defense. We might be the rookies, but thanks to our ingenuity, we're not going to get bullied on the field
-these four wheels are directly driven by CIMs so we can zip across the field at 154 fps according to JVN Design Calculator (great tool by the way guys).
-the bot fits in a 26x26 square. its octagonal shape allows for surface area for electronics.

-Frame milled from solid...um...wow! How long is that operation going to take, and how much does that block of aluminum cost??
(seriously, check this, if the block is over $400 market value, you may run into trouble)

-Has the wheels/wheel formation been prototyped? I'm intrigued, yet skeptical of how well it will work. Do the corners of the wheels have low-traction material? This formation typically uses omniwheels for multi-directional motion, and I'm not sure how it will work with traction wheels.

-Again, you may want to prototype and see just how much traction you gain from decagon-shaped wheels, and whether it's worth the bumpy ride.

-Direct drive from CIMs...That's not quite how it works. Gear reductions add torque, and a free-spinning CIM does not have close to enough to move a robot effectively. You may want to look at JVN's calculator again, and see how much torque it will take for a 6-8" wheel to effectively acccelerate 150-ish pounds of robot. The fastest I've ever heard of a robot moving is 18-ish feet per second. Also, consider the drivers. Do they have the reaction time to effectively control a speedy robot? Might slowing it down, in some ways, speed you up?

[Hawiian Cadder]

woah, that means it will cross the field in 1/3 of a second, if you can effectively make a frame like that i like it. also without gearboxes you will be pushed around quite a bit.

[Hawiian Cadder]

actually this would work, you just need to control it with a melty brain.

http://www.spambutcher.com/meltyb.html

[Nuttyman54]

Originally Posted by poohbear

-these four wheels are directly driven by CIMs so we can zip across the field at 154 fps according to JVN Design Calculator (great tool by the way guys).

Wow...just...wow. I thought fast would be good but, at those speeds you should be able to use the Lorentz Contraction to get away with a larger manipulator into the 84" cylinder (the refs will never be able to tell!). This is sheer brilliance! Have you considered the possibility of using the Picard Maneuver in match play?

[SirTasty]

um... wow... where to begin...

Brace yourself, this post is going to be extremely critical, but you will thank me for it later. Take it from a four-year FRC team member and a design/strategy specialist, there are like nine thousand and one problems with this drive train that will make it all but unusable on the field. I'll start with your bullet points.

Originally Posted by poohbear

-the body is milled from a solid block of 7071 aluminum (with our sponsor's five axis mill) to retain the maximum structural strength.

This is almost definitely outside of the budget allowed within the rules and is also a huge waste of money and resources. Frankly, I am a bit dumbstruck that your sponsor is willing to commit their five-axis mill to this kind of project.

Originally Posted by poohbear

-the wheels are decagons instead of circles. NOW can we squeeze in more than tangential contact every tenth of a rotation, therefore we get more traction.

I have no concrete criticism of this one, but suffice it to say that I am extremely skeptical. Wheels are circular for a reason, if decagons worked better, some automotive specialist would have noticed in the last hundred years or so. Of course, robots are not cars, so if you really think you've hit on something here, I would create a prototype to see what happens, but I am 99% certain that this will not be effective. I think the most likely result is your motor does not have enough torque to turn the wheel.

Originally Posted by poohbear

-the wheel formation allows for no "getting pushed around" and great defense. We might be the rookies, but thanks to our ingenuity, we're not going to get bullied on the field

Are you referring to the 45 degree angle "holomonic" wheel configuration? Every year we see a team try this. Traditionally it's done with omni wheels, but I've seen it done with regular traction wheels. It never works. The traction from the "front" and "back" wheels gets in the way of the "side" wheels, and all you can do is spin. You can use omnis to fix this, but you end up with no traction. If you want omnidirectional steering, take four hundred bucks you would spend on that aluminum block and invest them in a good set of mecanum wheels instead. Better yet, if you have access to the kind of machine shop that lets you use a five-axis mill, you probably have the ability to make a legitimate swerve drive. Or, since you're a rookie team, you could go with a traditional four-wheel or six-wheel drive. Anything but this mess.

Originally Posted by poohbear

-these four wheels are directly driven by CIMs so we can zip across the field at 154 fps according to JVN Design Calculator (great tool by the way guys).

Either you missed a decimal point (or two?) or you're doing something very wrong. This number is completely ridiculous, throw it out (btw, I rolled on the floor laughing when I read the comment about the Picard maneuver). Seriously. The most likely result is your motors stall from not being able to rotate your (decagonal) wheels. Particularly without gearboxes. Seriously, get some gearboxes.

Originally Posted by poohbear

-the bot fits in a 26x26 square. its octagonal shape allows for surface area for electronics.

No problem here, moving on.

Originally Posted by poohbear

I know its pretty good, but what are some design tips you veteran teams might want to bestow upon us?

Here's a tip: don't try anything crazy in your first year. Innovation rocks, but if there's a traditional way of doing something, the reason "everyone else is doing it" is because it works. Learn from historical teams' mistakes, not your own. One should never be afraid to depart from the norm, but should never do it without careful thought (which clearly wasn't given here). You have to really understand the rules before you know how to break them.

Of course, there's a chance that you'll just ignore me, in which case I hope I don't end up on an alliance with you. Just remember that Dolan from 2374 warned you.

Anyway, that whole post was very rude (inb4 "you're trampling creativity"), but you really needed to hear that before you wasted all of that time and money. Now you're out a third of your build season, it's time to think about reprioritizing.

[Andrew Y.]

Originally Posted by poohbear

Hey comrads!

Here's our team's final design for our first drivetrain ever and its pretty innovative if i say so myself

-the body is milled from a solid block of 7071 aluminum (with our sponsor's five axis mill) to retain the maximum structural strength.
-the wheels are decagons instead of circles. NOW can we squeeze in more than tangential contact every tenth of a rotation, therefore we get more traction.
-the wheel formation allows for no "getting pushed around" and great defense. We might be the rookies, but thanks to our ingenuity, we're not going to get bullied on the field
-these four wheels are directly driven by CIMs so we can zip across the field at 154 fps according to JVN Design Calculator (great tool by the way guys).
-the bot fits in a 26x26 square. its octagonal shape allows for surface area for electronics.

I know its pretty good, but what are some design tips you veteran teams might want to bestow upon us?

P.S. The manipulator is coming soon with just as much innovation as you see here. Watch out for team 3815!!!

P.S.S. We would like to thank our professional mentors for their wisdom and guidance in designing this beastly beauty.

JUST INCASE THIS IS N OT A TROLL JOKE

Hey Poonbear, my name is Andrew and I am a mentor for the Westminster School's Robotics team, team 2415, the WiredCats. I looked up your team number and I see that your team is from North Forsyth County. My team is located in Atlanta and are not too far from you guys and that you guys are rookies.

I see that there are a few design flaws (and boy do I wish that we had a 5 axis CNC mill) and we are always looking to help other teams whenever we can. If you would to set up a meeting, some students as well as myself can make the trip up there and help out some if you would like.

But remember, time is of the essence in this situation, we dont have much time left in the season but I know that if this is not a joke, we can really get something workable together.

Thanks and good luck in the season,
Andrew