pic: WCD off season chassis from 2471


See “Chassis Tube Connector”

This was a point of much discussion while in the design phase. We thought gussets would be stronger, but using blocks would fit with the chain in tube solution better.

This is what we ended up going with, partly because the belly pan is adding a lot of corner to corner strength already.

We did not use these, but they look to be functionally equivalent. The plastic blocks ended up being a good project for younger students to get some training and experience in.

It would be interesting to see the FEA for the block vs gusset design. On my team the thought was that blocks were stronger because the blocks were pulling the frame members toward each other.

Does anyone know where to find a cad file forthis?
The half inch hex

Because I couldn’t find it, I just downloaded the round version, put a hex bore in it, re-saved it as a STEP file, and reopened it. That gave me the 1/2" hex 17t double sprocket.

I can not find the round version. Am I missing something on the website?

I emailed them about it last year. The file can be found here.

Wait, Mean Machine’s not doing swerve? :smiley:

Glad to see you’re having fun and building robustly for BunnyBots – should be a fun event.

What are you doing for center drop? Do the sprockets you’re using inside the tube have enough clearance with the walls of the tubing for a center drop? I haven’t seen that done before but since you’re using 1/16" tubing it could be possible.

Do you feel 1/16" walled tubing is strong enough for a traditional drive train?

Yep, I’m looking forward to it! :wink:

The bearing blocks we are using have their bearing holes drilled 1/16" off center. The center wheel has its block upside down compared to the outer wheels, so that gives us 0.125" drop. If it tips around too much or is too squirrely, we will flip one of the outside wheels for effectivly a 0.0625" drop. We are using 16t #25 chain sprockets.

Do you feel 1/16" walled tubing is strong enough for a traditional drive train?

I think so, but we’ll know for sure by the end of the month.
Anything that survives this BunnBot game will certainly be “strong enough for a traditional drive train”

Yes, 1/16 wall tubing is easily strong enough for a drivetrain.

This is not a safe general statement to make at all. There are multiple loading conditions to consider, and it entirely depends on how you build your frame, what loads it is exposed to, etc.

Generally, 1/8" wall (or .1" wall) tubing is used on the driveline in order to support the bearings or internal bearing blocks better. 1/16" is too thin for a drivetrain bearing fit not supported by anything else. So regardless of strength many teams run 1/8" wall on the driveline. This could be different for systems like the VersaBlock which don’t rely on the internal walls of the tube for support.

As for your cross members, I have heard in the past that teams have dealt with buckling cross members under very heavy defense when they used 1/16" 2x1 tubing. This obviously depends on the number of crossmembers used, any other cross-structural support from other mechanisms, etc. but I wouldn’t just say “1/16th is easily strong enough” as a general statement.