pic: WCD off season chassis from 2471

[R.C.]

Originally Posted by RobotsThatWork

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'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?

[RobotsThatWork]

Originally Posted by R.C.

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?

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.

[pribusin]

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 Care to give me some insight on the procedure? Are there access hole on the underside? Has anyone ever done this with belts?

[notmattlythgoe]

Originally Posted by pribusin

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 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.

[pribusin]

Got it - thanks.

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

[jman4747]

Originally Posted by pribusin

Got it - thanks.

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

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

[Nebster]

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

[notmattlythgoe]

Originally Posted by Nebster

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.

[Ty Tremblay]

Originally Posted by Nebster

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

http://www.team221.com/order.php?cat=15

See "Chassis Tube Connector"

[Bryce2471]

Originally Posted by Nebster

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

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.

Originally Posted by notmattlythgoe

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

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

Originally Posted by Ty Tremblay

http://www.team221.com/order.php?cat=15

See "Chassis Tube Connector"

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.

[cxcad]

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.

[zinthorne]

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

[asid61]

Originally Posted by zinthorne

Does anyone know where to find a cad file for this?
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.

[Nate Laverdure]

Originally Posted by RobotsThatWork

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?

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.