12-09-2016 10:14 AM

Chris is me

Re: pic: Holo

I'm really impressed by the quality of both the design and manufacturing of this prototype. Design wise, I like the use of 1.5x1 tubing below to save weight and 1x1 (16 wall?) tubing up top for bumpers / superstructure / etc. Manufacturing wise, the nice surface finish on everything and the very well done belly pan and gearboxes stand out. This is art!

12-09-2016 11:57 AM

GeeTwo

Re: pic: Holo

Yes, it's definitely a good looker!

Now it makes a more sense to me.. those long holes in the belly pan were for gearboxes, not wheels. I was trying to figure out how you would mount the gearbox from the first post.

Were you planning this as a competition-capable robot (ready for bumpers), or more as a demo? If the latter, I probably would have made the upper layer a square rather than an octagon to better protect the wheels from bumper interaction. As a showpiece (or Recycle Rush), it's spot on. [Now that I notice there are no mount points for manipulators or bumpers, I'm guessing the latter.]

With the upper frame as well as the lower, it looks quite stiff for a 4-wheel holonomic drive. This may cause you some unusual behavior on uneven ground, with the weight being on two or three wheels. The cantilevered wheels may provide a bit of suspension to compensate for slight irregularities like a plate under the carpet, but probably not something larger. If you plan to drive on carpet on solid floor, again, not a concern.

12-09-2016 12:04 PM

rlance

Re: pic: Holo

We also built a holonomic robot using the omni-wheels just for fun in the past few weeks. It does not look nearly as nice as yours, but it was a great experience for the programmers and drivers and gives us a second option for a drivetrain. Since ours wasn't intended for competition we used BAG motors on VP Gearboxes to run the wheels, which got really hot after about 3 minutes of use. I noticed you have heat-sinks and fans on your CIM motors. Did you have an experience in the past that influenced that decision?

Because of the nature of the wheels, these robots don't have great traction and aren't made for pushing matches. That being said, did that influence your decision on gearing, such that you are going for speed over power?

12-09-2016 12:30 PM

Chris is me

Re: pic: Holo

I've heard this stated many times over the years, and it intuitively makes sense, and I believe(d) it. And then in 2015 my team built a mecanum WCD with a super rigid metal frame, that drove over obstacles and ramps without really any problem. A good gyro and good software, which you already want if you're pursuing this kind of drive, should help compensate for varying loads on different wheels, and if you built the chassis square enough, all wheels should touch the ground on a flat floor.

12-09-2016 12:56 PM

SerpentEagle

Re: pic: Holo

Thank you! Yeah, the 1x1 was 1/16 wall. The superstructure is designed to hold up to 200lbs. It has a minimum safety factor of 40. We used roloc pads for the surface finish, it works great!

Thanks! This is actually supposed to be a display robot at a certain event (we're not allowed to talk about it until then). The upper structure is supposed to hold up to 200lbs.

Its very stiff for a holonomic drive, especially with all the weldments across the frame. It pretty much doesn't drive on anything that isnt perfectly flat haha.. unless someones sitting on it! With the 200 lbs on the chassis, we have no problem driving it around on a bumpy floor. Check out the original post for some videos!

Cool!

We havn't had any experience using BAGs for drivetrains. Our CIMs actually didn't get very hot at all.. In fact, the wheels got hotter than the CIMs due to all the friction! We have heatsinks on there because this thing will be driving around for 8 hours with up to 200 lbs on this thing! So we're just planning for the worst.

We would never use this kind of drivetrain in a real game! (unless its 2015 lol). We had to gear very low (16:1) so we wouldn't trip the breakers every other minute (since its supposed to carry up to 20lbs).

Even if we did gear low for defence, it would be almost useless since we would get pushed all over the place anyways!

12-09-2016 01:39 PM

GeeTwo

Re: pic: Holo

Oh, an indoor powered holonomic furniture dolly. Looks like you nailed riveted it!

12-09-2016 08:51 PM

SerpentEagle

Re: pic: Holo

: D

12-09-2016 11:01 PM

cscottm

Re: pic: Holo

In the Gearbox picture I noticed that there are 14 tooth 3/8 inch hex gears in the gearbox. Just letting you know that there was a manufacturing error in the ones that were sold during 2016 season (the way they machined them made them weak or something) and over the course of our season we managed to shear all of the teeth off. I doubt that you will have problems as this isn't exactly for brutal play, but I would recommend having spares.

After our issues, we replaced them with the steel versions and they were fine.

(I'm not looking to blame vex or start a war, just sharing information)

Otherwise, it looks great!

12-10-2016 01:40 PM

SerpentEagle

Re: pic: Holo

ALL your teeth? Wow, thats crazy. Do you know if vexpro has solved this issue yet? Anyways, thanks for letting us know!

12-10-2016 03:17 PM

cscottm

Re: pic: Holo

I have no idea, sorry!

But yeah, all of the teeth on them. (we assume one sheared, and then it's only a matter of time.)