Team 3397 started our first off-season build project about 4 and a half weeks ago. We meet Tuesdays and Thursdays from 7-9, resulting in us having somewhat of a limited time to work on this. We decided we wanted to build something we had never built in the past, something that would challenge us. We decided we were going to build an octagonal H drive chassis with omni wheels. We will lay the electronics board across the top (you can see 2 of the 4 vertical supports we have on so far that will hold it). We will also add cross braces that will be for support and yo hold the battery.
I couldn’t help immediately thinking of this.
Great work! Are you planning on putting any mechanisms on top of this later on?
Hah! I remember seeing that, After building the support braces and applying electronics we will decide what will happen next. Since our team has used the kop chassis the last two seasons we’ve decided that we want to be more competitive and challenge ourselves, because of that there’s been some talk of rebuilding it in January to be used on our 2016 bot (depending on the specs of the game). Regardless It is our team’s first holonomic drive (and might be the first we ever use in competition!). I’m proud of my team and I’m super excited for 2016!
Looks good. Why did you stuff wood into the vertical electronics board supports? The aluminum tubing should be strong enough to hold an electronics board, especially if you add a cross brace.
Btw, H-drive describes 5 omniwheels in a H shape, and this is not a H-drive. I’m not sure what it would be called though (omnidrive?).
Good luck, and I hope to see a video of this moving soon!
Poor man’s mecanum?
I think this could be called a kiwi drive, or maybe just a holonomic drive if it turns out that kiwi drive only refers to drives with three omni wheels.
Kiwi refers to 3 IIRC. Holonomic drive or omni drive is enough to describe it I think.
Nice work! What drove your design to put electronics up top? Even if you do that, I recommend putting the battery down low to lower the center of the mass.
Being from the team that coined the name “kiwi”, I really only consider it for 3 wheels. (Though since this chassis is approximately round and not a rectangle, I can see the case being made that it’s a 4-wheel kiwi)
We stuffed wood inside the aluminum supports to make it easy for us to attach it to the chassis, of course it could have been done a different way. (the supports sit directly on top of the chassis, we put a small metal plate across the side and drove one self tapper into the chassis and another through the aluminum and into the wood which holds the two together just fine. It definitely will hold our electronics board (which is a sheet of lexan cut into an octagon shape, the electronics are screwed and zip-tied on through the holes that are already applied to the lexan before we buy it). I’ve known the “H” in “H-drive” to stand for holonomic, which is why I labeled it is as an “H-drive” I apologize if I have it wrong.
Coincidentally, we actually officially named our project the “poor man’s swerve drive” because of its ability to drive in any direction and because of our limited budget in which we had to go over by an amount in which will remain undisclosed :yikes:
Our electronics captain decided to put the electronics at the top simply because the project was originally to build just a chassis. We’re actually integrating a battery holder/tray/bracket (whatever you want to call it) into our cross supports, along with that we are going to cut a rectangular hole into the center of our lexan electronics board that will be large enough for the battery to slide through and down into the holder tray. The battery will sit in the middle of the robot.
On several threads, I’ve seen this layout referred to on CD as a Killough drive, named after the man who invented holonomic drive. His drive had three ball wheels, and more closely resembled kiwi.
I was reminded of this, from late 2005 / early 2006.
It is difficult to overstate the impact that AndyMark and VexPro have made on the FRC community, by enabling teams without extensive fabrication means to explore and test design concepts at (relatively) modest cost.
wow times have changed.
Quite literally everyone and their Dog in FTC used a similar drivetrain like this to achieve holonomic motion. This could be the first time I’ve seen someone build an FRC version, but I haven’t looked too hard either.
I hope you post some video of how it drives sometime!
My team considered using a holonomic drivetrain last year, but never went further than a prototype. we stopped and ended up using a normal mecanum system about half way through the second week. Not quite sure why we stopped though…
Just wanted to say great job on the off-season project 3397! This team has a lot of great students that are very easy to interact with.
Let us know how the cantilevered omni wheels hold up. I know you probably won’t be putting any significant kind of weight on it but it may be a good test to load it up and see how much the shafts flex.
Post up a video once you have it running!
I agree this is a great project – kudos to U City for taking it on!
Re: cantilevered omniwheels, 3620 ran them in 2015. You can see them by zooming in on the linked picture (our TBA beauty shot). The wheels and shafts held up very well through 69 competition matches at five events (two districts, DCMP, CMP, and one off-season).
The plastic clamping bearing blocks did not fare as well – we broke a couple of them on the competition robot and one on a demonstration robot also. We will not be using them cantilevered in a drive train for a full-contact game, but will definitely consider them for some mechanisms.