pic: FRC 5332 First ever WCD pics

[Jay Burnett]

loading photo ...

[AlecMataloni]

Looks good! Just one thing though.

You'll want to make the spacing between the middle sets of wheels larger. One of the benefits of a properly made 8WD is the ability to turn about the center of your robot without rocking back and forth like a 6WD. With how close your middle wheels are to eachother, I can imagine your drive doing a lot of rocking back and forth, which is undesirable.

Unless, of course, there's no dropped wheels in this design. If that's the case, ignore what I just said.

It's definitely a start, and the best place to begin is at a start, so you're on the right track. Now, judging by this model. it appears you may be slightly confused about some of the core design aspects of a west cost drive. Not a problem though - we're gonna get that cleared up and make sure you know how to design the drive train style that has become the best in the west.

I'll start with the frame. Forgo the pocketing for now and wait until you have a solid drive base to take out material. You also do not need those center 2x1 extrusions. A correctly built frame will be plenty strong without them, and that's what you're gonna be making. The plates you seem to mount your bumpers to don't look too strong. Generally I'd say using a piece of 1x1 for the mounting is one of the most simple solutions here (though it certainly is not the only one). That example is one of my earlier CAD models. I'd like to point out that the diagonals in this model that support the 1x1 the bumpers are mounted to are not necessary, and more complex than the solution needs to be. Something more like this, with the 1x1 attached to some vertical tubing off the frame rail similar to your method is probably the simplest and the easiest.

Next I wanna touch on your drive system. I'm totally digging the 8wd, however it appears that you have no transmission system to drive your wheels and your sprockets are all aligned so that only one chain can go between them. That's a big no no dude, since if the one chain breaks you lose all the other wheels (aside from the directly driven wheel, but you'd still rather have all wheel drive). Have you seen the WCP WCD bearing blocks, or the VEXPro VersaBlocks? In a WCD, the bearings for the live axle system are put in bearing blocks that can move in slots in the tube to tension the chain. I'll grab some examples of them in a bit and post them here.

I'll edit this post with updates as I think of them. Keep up the good CAD work, man. You'll be making fly drives in no time.

[Jay Burnett]

Originally Posted by Andrew Lawrence

I'll start with the frame. Forgo the pocketing for now and wait until you have a solid drive base to take out material. You also do not need those center 2x1 extrusions. A correctly built frame will be plenty strong without them, and that's what you're gonna be making.

I know that this base would be strong enough without the center 2x1's, but a priority for our mechanical team was to have the drive train sides be completely removable using a couple bolts. With a normal WCD design that would mean relying on the super structure to hold the remaining drive tubes together with the help of the belly pan. To avoid this, we decided to add those tubes to retain structural rigidity when repairs are being made.

Originally Posted by Andrew Lawrence

The plates you seem to mount your bumpers to don't look too strong. Generally I'd say using a piece of 1x1 for the mounting is one of the most simple solutions here (though it certainly is not the only one). That example is one of my earlier CAD models. I'd like to point out that the diagonals in this model that support the 1x1 the bumpers are mounted to are not necessary, and more complex than the solution needs to be. Something more like this, with the 1x1 attached to some vertical tubing off the frame rail similar to your method is probably the simplest and the easiest.

The bumpers are also attached to 1/8 angle that fits snugly on the inside of the corner 2x1" tubing. So not all, maybe not even most, of the force of hits is transferred into the rail. If you still think that its to weak, I can make the change.

Originally Posted by Andrew Lawrence

Next I wanna touch on your drive system. I'm totally digging the 8wd, however it appears that you have no transmission system to drive your wheels and your sprockets are all aligned so that only one chain can go between them. That's a big no no dude, since if the one chain breaks you lose all the other wheels (aside from the directly driven wheel, but you'd still rather have all wheel drive). Have you seen the WCP WCD bearing blocks, or the VEXPro VersaBlocks? In a WCD, the bearings for the live axle system are put in bearing blocks that can move in slots in the tube to tension the chain. I'll grab some examples of them in a bit and post them here.

Lol, I'm sorry it seems so unfinished. I'm in the process of making all those changes, once i finish the gearbox, I will change all the distances to make it workable. I haven;'t really put that much effort into that yet. I have custom bearing blocks in there right now. And instead of internal tension, there will be a plastic spacer attached to the 2x1 and a 1/8 plate with holes that will allow it to be moved up and down between the sprockets. Thanks for your feedback!

[Jay Burnett]

Originally Posted by AlecMataloni

Looks good! Just one thing though.

You'll want to make the spacing between the middle sets of wheels larger. One of the benefits of a properly made 8WD is the ability to turn about the center of your robot without rocking back and forth like a 6WD. With how close your middle wheels are to eachother, I can imagine your drive doing a lot of rocking back and forth, which is undesirable.

Unless, of course, there's no dropped wheels in this design. If that's the case, ignore what I just said.

All right! I was wondering if the space was large enough. And just out of curiosity, how would having no drop work?

[Arpan]

Originally Posted by Jay Burnett

All right! I was wondering if the space was large enough. And just out of curiosity, how would having no drop work?

There's a good white paper somewhere that explains the physics, but basically a square or wider robot with 6 or 8 wheels and a well centered cg can turn okay (not as well) without a drop. Personally I don't like drops on square robots; maximizing traction by increasing contact area can help a lot