pic: Cyber Blue Swerve Chassis - Rear View

[Chris Fultz]

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[Brandon Holley]

Looks extremely slick, kudos to 221 LLC and Cyber Blue. What kind of weight are you guys looking at for that setup right there?

Brando

[Collin Fultz]

To be honest, we have no idea how much it's going to weigh. Our focus so far has just been "get it done" so that the programming team can start working. Once it's finished, which it is now, we will look at ways to save weight for potential future usage, as right now it is way too heavy (estimation) to use as a competition robot

[Brandon Holley]

Originally Posted by Collin Fultz

To be honest, we have no idea how much it's going to weigh. Our focus so far has just been "get it done" so that the programming team can start working. Once it's finished, which it is now, we will look at ways to save weight for potential future usage, as right now it is way too heavy (estimation) to use as a competition robot

Yeah I had no intention of starting the "you can save weight here" discussion, I just wanted to know if you had a rough idea of that system. I know the one that was posted on 221's site was 100+ lbs. but that was for a client (non FRC). It's always nice to compare weights of different configurations to see what could be more beneficial. But seriously, it looks really nice thus far.

[Nikhil Bajaj]

What sort of sensors are you using for the angle measurement?
EDIT: Never mind, they're clearly potentiometers or something that acts as such (3 - pin)

[Andrew Schreiber]

<strike>Potentiometers, as can be seen here</strike>

Out of curiosity, if you are going to connect all 4 modules together why bother with 2 Globes?

[insert question by Dave about how well you can adapt legs onto it]

[EricH]

Originally Posted by Andrew Schreiber

Out of curiosity, if you are going to connect all 4 modules together why bother with 2 Globes?

Redundancy. I seem to recall that at one point in 2005, a PWM for an arm motor's controller somehow disconnected on 330's robot. We didn't notice for I don't know how long, simply because the other motor on the arm was enough. In 2007, with the same design, we removed one arm motor to make weight with both ramps.

[Andrew Schreiber]

Originally Posted by EricH

Redundancy. I seem to recall that at one point in 2005, a PWM for an arm motor's controller somehow disconnected on 330's robot. We didn't notice for I don't know how long, simply because the other motor on the arm was enough. In 2007, with the same design, we removed one arm motor to make weight with both ramps.

As good a reason as any I suppose. Thanks.

[Chris Fultz]

[quote=Andrew Schreiber;880335
Out of curiosity, if you are going to connect all 4 modules together why bother with 2 Globes? [/QUOTE]

Yes, for redundancy and accuracy.

Redundancy - One globe has the power to turn all for modules, two will make sure they will turn even if one fails or loses power (connector, software, etc.)

Accuracy - By tying all four together, we are assured that each wheel turns the same number of degrees all at the same time. Keeping the left side and right side separated would allow for error in the systems to let one set of modules turn a little more or a little less and possible not return to "0" after a turn.

Also, this is a prototype / demo and some of the precautions and redundancies we are putting in might not make sense on a competition robot where you are making the risk / complexity / weight trade-offs.

[Raul]

Looks great.

One concern - I cannot tell from the picture how the globe motor is mounted or how the sprockets are mounted to it. I've always understood that globe motors are not designed to have a cantilevered load on the shaft coming out of its gearbox.

[Collin Fultz]

Raul -

That is a legitamate concern. The globes are mounted to an aluminum plate which is mounted on the bottom of the top 80/20 rail. We then use the Globe DD hub from AndyMark (here) with two sprockets and spacers.

I, personally, don't have a ton of experience with the Globe motor, but the team does. If this is true of the globe, it wouldn't be too difficult to build a support structure for the top of the Globe/sprocket assembly.

How does 111 turn their crab modules?

Thanks for your thoughts. We are building this now so that we may learn from those with more experience than us without the stress of a build season. Any other questions or criticisms are welcome.

//Edit//

This photo may show the Globe mounting a little better.

[J93Wagner]

It looks extremely clean and uncomplicated. Definitely not ours. (we rushed ours into service four weeks into build after NO previous experience with crab/swerve drive xD) Keep the good work going. I'm looking forward to seeing more pictures in the future.

P.S. I have access to our drive frame if you need it.

[JVN]

Originally Posted by Raul

Looks great.

One concern - I cannot tell from the picture how the globe motor is mounted or how the sprockets are mounted to it. I've always understood that globe motors are not designed to have a cantilevered load on the shaft coming out of its gearbox.

I agree with Raul, and always support the output shaft of the Globe motor.
Maybe I'm overly cautious? Let me know how your prototype works unsupported.

-John

[Aren_Hill]

I can see why to be cautious, yet even that being said whenever my team has used globes the other end has been unsupported and hasnt given us any issues.
But the places in which we used them didnt have constant sideloads, just occasional ones.
In theory the chain going both ways off of it may cancel out some

[Mike Soukup]

Looks real nice.

Here's a tip that will save you time and money. If those pots have hard stops at each end and can be broken by being driven past those stops, add some mechanical stops to the system. Your electrical team will thank you. The system will get away from you at least once during early software development and will start spinning wildly. It's just something I've heard and not from any personal experiences

Can you share with everyone how you plan on using the data from both pots? We've contemplated adding redundancy in the past, but have never come up with an easy way to distinguish a good vs a bad pot so we always stick with one.