pic: WCD off season chassis from 2471



Recently completed the mechanical side of the drive train for our off season competition. Electrical is on its way. Team 2471 (Team Mean Machine) has never made a true WCD, so this has been a learning experience. Questions and comments are welcome.

I don’t see any chain. Is that chain-in-tube or are you just powering the middle wheels?

Are you going chain-in-tube to power the corner wheels?

Are the two vertical 2" x 1" tubing pieces on the left side (as pictured) corner wheels encoder mounts? Why do they stick up above the height of the frame?

Is see the question I was going to post has already been asked…

OP please to tell.

It’s a chain in tube design

They are encoder mounts. They stick up to accommodate the gears that run the encoders. I’m not sure why they were done that way, as I was not involved in their design.

What lead you to choose to use tensioners with your design?

One of the major benefits of the in-tube design is that it’s practically impossible for a chain to jump the sprocket, especially if the center-to-center distance between the sprockets is correct.

I was not involved in that decision, so I can’t say for sure. However, I do know that bearing blocks were used so that the the frame could use .0625in wall tubing.

Do I spy shock absorbers? Or is that black ABS for spacing?

for your chain in tube design, are you using 2"x1" tubing? if so, are you using COTS sprockets? I haven’t been able to fit 2 COTS sprockets into the tube. It would be great if anyone could tell me how everything was packaged together.

I can’t speak for team 2471, but these fit. A version broached for 1/2" hex is available in the drop down selection box.

I’m not sure how cots sprocket don’t fit? Do they not fit due to the diameter or the width of the sprocket or both?

Yes, and yes. They are plastic spacers. We designed the bumper mounts that way to help insulate the frame from impact. This year’s BunnyBots competition has no rule against high speed ramming, and looks to be highly violent.

It was designed to use standard vex spockets, but because they were out of stock, we ended up using steel sprockets with shortened hubs. I don’t know the exact layout.

Very nice, I was unaware that they were availible in hex.

Two 16 tooth vexpro sprockets do not sit next to each other inside the 2x1x1/8 (so width). This is true for both when bearings are press-fitted, and when I use a versa bearing block. The Sprocket with Chain attached to it has a total diameter of 0.491 inches. When I put 2 back to back it would be too wide to fit inside the boxtubing. Any solutions?

I haven’t looked into the 17 tooth double sprocket, but can you create a dropcenter with the larger diameter? I know the clearance is pretty slim already for 16t, but I don’t know for sure with 17t.

Very nice and clean drive base. I want our team to look into a chain-in-tube design this year but I’ve always wondered how you assemble the chain and sprockets in the tube :confused: Care to give me some insight on the procedure? Are there access hole on the underside? Has anyone ever done this with belts?

What we’ve done is loop the chains around the sprockets and then drop the entire thing down into the tube. Then slide the axles through the sprockets and the bearings over the axles. This is of course 100x easier if the tubes are not attached to the robot already.

If you are using 2 sprockets in the middle like we do we have a small piece of axle that we’ll put through the two sprockets to hold them together during the drop and push that piece out with the final axle.

Got it - thanks.

Are those 3" x 0.875" wheels? How are they kept from slipping off the hex shaft?

We chose to avoid this problem by using 2 x 1.5 x 1/8 tube.

The 17t sprocket works in the 2 x 1 x 1/8 because it has a large enough pitch diameter that the chain clears the 1.125 bearing OD.

External retaining rings: http://www.mcmaster.com/#97633a200/=102dny4

What are you using to hold the corners of the frame together? It’s not clear to me

There are blocks in the ladders with through bolts going through the rails.