pic: Klein Bots 3735 2015 Offseason Drivetrain Project CAD Rendering

[lewislongbottom]

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[kyle_hamblett]

Looks nice! It looks like 148 was a bit of an inspiration (correct me if I'm wrong). Does it use chain-in-tube or are the chains just not shown?

[lewislongbottom]

This offseason, the Klein Bots decided to design a WCD Chain-In Tube drivetrain. We wanted to experiment with different options and features, so we went with a modular design strategy.

We wanted to have a versatile drive-base configuration; so we now have options to test an 8WD, 6WD, and 4WD drivetrain just by changing the configuration of the drive-tubes.

We also have pockets in the bellypan to move the position of the gearboxes; which are the VexPro 2 CIM Ball Shifters, this function just gives us more options if we decide to change positions to accommodate different drive configs.

We also designed what we call the "Wings", they were inspired by FRC Team 148 on their experimental drivetrains. We aren't getting these fabricated right now, this will be a future addition (hopefully).

This will be our first WCD (and Chain-In Tube) so we hope to learn some things before the coming build-season if we do decide to go ahead with this design.

[Kevin Ainsworth]

What type of wheel drop do you plan on running?

[lewislongbottom]

We don't have a drop in the CAD, however I believe the plan is to use traction wheels and rivet an extra layer of tread on top of the existing tread. It should give us enough lift on the center wheels to avoid wheel scrub.

[Ari423]

Originally Posted by lewislongbottom

We don't have a drop in the CAD, however I believe the plan is to use traction wheels and rivet an extra layer of tread on top of the existing tread. It should give us enough lift on the center wheels to avoid wheel scrub.

Just be careful: that means the edge of your center wheels will be moving faster than the edge of your outside wheels. This could cause some weird driving experiences as the bot "rocks" slightly, putting more weight on the front, back, or center wheels.


Also, what are the giant holes in your bellypan for? Is there a mechanism being designed to go there?

[notmattlythgoe]

Originally Posted by Ari423

Just be careful: that means the edge of your center wheels will be moving faster than the edge of your outside wheels. This could cause some weird driving experiences as the bot "rocks" slightly, putting more weight on the front, back, or center wheels.


Also, what are the giant holes in your bellypan for? Is there a mechanism being designed to go there?

Several other teams are currently doing this already. The speed difference tends to be negligible.

[lewislongbottom]

We will keep that in mind.

"We also have pockets in the bellypan to move the position of the gearboxes; which are the VexPro 2 CIM Ball Shifters, this function just gives us more options if we decide to change positions to accommodate different drive configs."

[Kevin Ainsworth]

I'm curious about the short length verses wide width when the center wheels are touching the carpet but the outside wheels aren't. During acceleration the four back wheels are the only ones touching and that scares me also. Our experience is that this makes for a twitchy bot when turning and an unstable bot when trying to drive fast in a straight line. Anyone have experience with this?

[fargus111111111]

Why not go with omniwheels on the corners so that there is no need for a drop. It seems like that would result in a more stable robot than any drop center and it eliminates the need for different diameter wheels.

[notmattlythgoe]

Originally Posted by Kevin Ainsworth

I'm curious about the short length verses wide width when the center wheels are touching the carpet but the outside wheels aren't. During acceleration the four back wheels are the only ones touching and that scares me also. Our experience is that this makes for a twitchy bot when turning and an unstable bot when trying to drive fast in a straight line. Anyone have experience with this?

Teams have been running 8WD robots in this configuration for years without issue. The same could be said about 6WD drop center robots only running on 4 wheels at a time and yet it is probably the most popular setup in FRC.

[Jay Burnett]

Just for thought's sake, what would be the trade-offs of switching the 4 corner wheels out for omnis? Did you guys think about doing this at all? And if so, why did you decide against omnis?

[notmattlythgoe]

Originally Posted by Jay Burnett

Just for thought's sake, what would be the trade-offs of switching the 4 corner wheels out for omnis? Did you guys think about doing this at all? And if so, why did you decide against omnis?

I believe you'd be lowering the amount of traction you have because you'd be taking some of the weight off of the center traction wheels and moving it to the omni wheels.