pic: FRC488 - Six Wheel Drive Chassis

[Rick TYler]

Ah, jeez, I know that the plural of chassis is chassis, I was just funnin' around.

For the record, in 2005 our bot had six wheels with 2WD, but last year our very heavy, very strong chassis had six wheels with 6WD. In case anyone cared.

I AM going through FRC withdrawal now that kickoff is near, but I also fell asleep last night thinking about softballs, so maybe I'm becoming a VEXer, too.

I would like to bring our new, nearly-all-rookie team to visit an FRC team during build, so maybe I will take 488 up on their offer. We also have had friendly comments from team members at 1318 and 492. I think the "F" in FIRST really stands for "friendly."

[artdutra04]

Originally Posted by Rick TYler

Having said that, Madison makes nice chassises -- er, chasses -- er, chassisses -- what IS the plural of chassis anyway?

One can only venerate the intrinsic quagmires of the lexicon of the English language.

[foundbobby]

Originally Posted by M. Krass

The wheels are all in line -- there's no 'rock' at all. The chain is #25.



Because the center wheel is not lowered at all, at least one outside set of wheels should be omniwheels to alleviate friction while turning. I chose to put a set on each end because there's no penalty to in line pushing force, generally, and I like to subtley encourage our drivers to avoid conflict.



I'm now looking at a mounting scheme that will accept bumpers and protect the wheels from impact. I've never put bumpers on a robot before, so I'm looking at examples of others' work to get an idea how to best accomodate the additional weight of the bumper assembly.



Our 2005 robot had a lowered center wheel and the tipping action drove me and our drivers crazy. It's an impact to the system each time the robot's inertia shifts and that starts to lead to annoying things like loosened bolts and the like. Practically, it's cheaper and easier for me to make omniwheels than it is to make traction wheels and it's certainly cheaper than buying them.



As shown -- which includes everything but stiffening gussets and a base upon which to mount electronics, it's 29.5 lbs.

The omniwheels are riding on 5/8" keyed shaft, while the AndyMark performance wheel is broached for a 1/2" hex shaft. It'd be relatively easy to change out a set of omniwheels for a set of traction wheels with a little bit of forethought. Namely, I'd need to make some shafts that are 5/8" diameter with keyway on one end and 1/2" hex on the other.



I'm waiting on the game before adding cross-bracing since I'm not sure if I'll need a scoop or something on one or both ends. I'd like to, if weight allows, put an aluminum plate (1/16" or so) across the bottom to add rigidity.

Nice design. What about having the wheels on the outside? Don't they need be protected some to avoid bent shafts and broken wheels?

[foundbobby]

Originally Posted by M. Krass

Thread created automatically to discuss this image in CD-Media.

Nice picture! We'll see you at SVR

[Richard Wallace]

Based on pictures in another thread I think this is probably FRC Team 488's robot. Madison is a member of that team, and her team role is mentor.

Maybe I didn't understand your question?

[Dominicano0519]

Originally Posted by 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.

uhh did you just say suspension, as in springs and dampners suspension??

this is a carpeted field were talking about

[VEN]

Do you guys have a shaft coming out of the tranny for the middle wheel as well as 2 sprockets on the inside leading to the front and rear wheels? Are the sprockets inline? Wouldn't you need gears on the same axle as the sprocket to drive the sprockets in that case? Are the sprockets on the same axle? In that case how can your wheels be inline? Are the sprockets on the wheels on an offset?

Alright no more questions just curious.

[Madison]

Originally Posted by foundbobby

Nice design. What about having the wheels on the outside? Don't they need be protected some to avoid bent shafts and broken wheels?

Teams have had success with similar designs in the past and our experience with the completed chassis yesterday indicates that, though we may want to protect the wheels, it's not a paramount concern given our strategy and design. In another game, or on another robot, it may be very important that the wheels are protected from damage and from the sort of wedging effect impedes motion that other teams with similar drives have seen in past seasons.

Originally Posted by foundbobby

Nice picture! We'll see you at SVR

We hope you'll take a minute and stop by our pit to talk to the team. I'd be happy to talk more about our robot and answer any questions you might have -- as would anyone else on our team. We're proud of the work we do.

Originally Posted by VEN

Do you guys have a shaft coming out of the tranny for the middle wheel as well as 2 sprockets on the inside leading to the front and rear wheels? Are the sprockets inline? Wouldn't you need gears on the same axle as the sprocket to drive the sprockets in that case? Are the sprockets on the same axle? In that case how can your wheels be inline? Are the sprockets on the wheels on an offset?

Alright no more questions just curious.

The gearbox at the center of each side has an output shaft that drives the center wheel. Two 18 tooth sprockets are coupled to that shaft and, via chain, drive the wheels at the front and back of the robot. Those sprockets are not in line -- they are offset 1/4". Our wheels remain in line because the sprockets on either end mimic the offset of their corresponding center sprocket.

Attached to this post is a cross-section of the gearbox that may help make the gearing arrangement a bit more clear. Excuse that the gears aren't meshed properly, please.

[Brian Mocci]

My favorite part about this design, something that no one has mentioned yet supprisingly, is the way that you extended your front and rear rails in order to protect the cantilevered wheels. Excellent design all around!