pic: FRC488 - Six Wheel Drive Chassis

[DanDon]

WATCH OUT!!! WE'VE GOT A DAVE ON THE LOOSE!!! SOS...SOS...SOS

[Rich Kressly]

Originally Posted by dlavery

M -
Just out of curiosity, what is the spacing between the wheel sets? Is it sufficient to cross a 20-inch wide, 16-inch deep, water-filled moat, should that capability ever be necessary?
-dave

Who keeps letting him in? Security!!!

I love the simple approach to the 6-wheel drive. I'll be follwing up later if you use this to see what additional stiffening was used/needed. Good luck.

[Madison]

Originally Posted by Rich Kressly

Who keeps letting him in? Security!!!

I love the simple approach to the 6-wheel drive. I'll be follwing up later if you use this to see what additional stiffening was used/needed. Good luck.

I took Dave's advice and added the fourth wall to the front and rear cross members as a start. Because these drivetrains are almost never operating absent some additional mechanism or superstructure, I try to incorporate those future additions into the design and allow for them to be used as support for the drive in the same way that the drive supports the mechanisms, if that makes sense. I try to design such that the finished robot appears organic -- not as if it was designed in pieces that were smashed together later.

Because of the holidays primarly, we haven't really done much of anything with our mecanum drive prototype. It still has no feedback system installed and remains difficult to drive. Most of the team agrees that, unless it appears to be a perfect solution for the new game, we'll stick with something more traditional like this drive, so there's a good chance you'll be seeing it somewhere.

[Andrew Blair]

Madison, I know that you have no broach capability, so I'm curious- where do you buy your #25 sprockets? I can't find any finished ones online, or in the Browning catalog.

[Dan Petrovic]

Originally Posted by Cody C

Not necessarily more maneuverable, But I bet it is nice to have the 'bot spin around it's center set of wheels instead of whichever four happen to be touching the ground

Wouldn't the spinning of the robot automatically lift the front and back wheels up and equal distance from the floor? Kind of like when your arms raise up when you spin around.

[Cody Carey]

Originally Posted by InfernoX14

Wouldn't the spinning of the robot automatically lift the front and back wheels up and equal distance from the floor? Kind of like when your arms raise up when you spin around.

Maybe on a perfectly 4-way symmetrical robot, but in My team's experience, It stays on 4 wheels and rocks back and forth... Whichever four wheels happen to be touching are the ones the bot spins around. Kinda messes up high-speed maneuvering.

[Madison]

Originally Posted by Andrew Blair

Madison, I know that you have no broach capability, so I'm curious- where do you buy your #25 sprockets? I can't find any finished ones online, or in the Browning catalog.

For this, we'll be ordering from McMaster-Carr -- part no. 2737T123. 5/8" bore was the smallest I found with a keyway for this particular sprocket. I didn't take a comprehensive look at many teeth counts, though, so I'm not sure how consistent the keyways are in 5/8" bore sprockets -- but I can't imagine why they all don't have one.

[Andrew Blair]

Ah, I see. We were going to be using 1/2" bore, and for some reason, no one on earth carries broached 1/2" bore sprockets. Thanks though!

[Rick TYler]

Originally Posted by InfernoX14

Wouldn't the spinning of the robot automatically lift the front and back wheels up and equal distance from the floor? Kind of like when your arms raise up when you spin around.

The last two years I worked on center-drive, 6-wheel robots and both times we purposely loaded one end of the 'bot with a LOT more weight for game reasons. This also had the effect of having the same four wheels on the ground most of the time. We had little fore-and-aft rocking and the robot wasn't tricky to steer at all. Having said that, Madison makes nice chassises -- er, chasses -- er, chassisses -- what IS the plural of chassis anyway? I'd hire her to consult on our chassis, but since I'm now on a VEX-only team, I think we'd be wasting her skills.

[CE Mexican]

Originally Posted by dlavery

M -

Looks quite nice, and you have obviously put a lot of work and thought into the design. The efforts to minimize the total weight are obvious. The biggest concern you may have is strength in the event of an impact or collision. You might consider making the frame members out of rectangular tube instead of channel. Given the amount of material you are removing, the additional weight from the fourth side of the tube will be minimal, but there will a considerable increase in stiffness of the frame assembly.

Just out of curiosity, what is the spacing between the wheel sets? Is it sufficient to cross a 20-inch wide, 16-inch deep, water-filled moat, should that capability ever be necessary?

-dave

I agree wiht what dave said about strenght, but on the contrary our team used aluminum channel for our frame and we didnt seem to have and problem with strength, and our frame took quite a beating during aim high this year

[dfukuba]

That looks very nice and pretty well engineered. My suggestions are that you only use one set of omni wheels. You have to admit that you will be getting in to conflict no matter what you do.
The frame does look pretty sound, but with all that material taken out, are you worried about bending at all? these bots go through some pretty hard hits.
But i am very impressed by your design and i look forward to seeing the end product after the next hectic 6 weeks =)
--Dan

[CE Mexican]

team 1783, which is my schools team, used a different drivetrain set up, we had designed a setup where each side had indepent suspension, and two wheels for each side. and this year (depending on the game) i have designed a three speed gear box that would be incorperated into our original design. also i was thinking about trying out a four whee drive design that would be built by me and a local shop. how many of you guys know about the xmods remote control cars at radio shack? well i got one for christmas (god only knows why) but i was looking at upgrades for it and i saw that they have a four wheel drive kit for them. and after hours of configuring, and designing i think that i can build the 4 wheel drive suspension and drivetrain for our robot.

[Fred Sayre]

Originally Posted by Rick TYler

The last two years I worked on center-drive, 6-wheel robots and both times we purposely loaded one end of the 'bot with a LOT more weight for game reasons. This also had the effect of having the same four wheels on the ground most of the time. We had little fore-and-aft rocking and the robot wasn't tricky to steer at all. Having said that, Madison makes nice chassises -- er, chasses -- er, chassisses -- what IS the plural of chassis anyway? I'd hire her to consult on our chassis, but since I'm now on a VEX-only team, I think we'd be wasting her skills.

And you of course, are welcome to come consult on our team any time Stop by if you feel you are missing out on the hectic 6 weeks that is FRC this season!

[JaneYoung]

Originally Posted by Rick TYler

what IS the plural of chassis anyway?

chassis, singular = chassis, plural
the plural would have a wee different pronunciation though

[Richard Wallace]

Originally Posted by Jane

chassis, singular = chassis, plural
the plural would have a wee different pronunciation though

One chass-ee, two chass-ease.