pic: Wood Coast Drive V2

[Mr V]

Originally Posted by lewislongbottom

How does attaching stuff to the robot work? It's probably a naive question, but I was wondering if using pop rivets is as easy as fastening them to metal? (I ask because I've never seen pop rivets used on wood before)

Yes pop rivets can be used with wood successfully. That is the way that all the angle aluminum, handles and latches are attached to the road cases that transport the fields and materials are made. Now when we made them for the PNW district we put a back up washer on them but the ones that FIRST made that I have looked at closely did not use back up washers.

Of course nuts, bolts and washers are also a option.

For the potential problem of bearing holes wanting to wallow out VEX makes these. http://content.vexrobotics.com/vexpr...g-20141111.PDF Cut the hole for the bearing place a bearing in this mount and into the hole and then rivet then match drill and rivet the plate in place.

[dtengineering]

Originally Posted by KohKohPuffs

Interesting design. Really like it.

Just one thing, why did you choose wood over aluminum for the drive chassis material? Is it for the weight benefits? I always thought that wood for a drive chassis is not preferable because when, say, you get hit by another robot, then the wood may break, or something like that. Really not sure of this, since I've never done so much woodwork in the past.

In 2005 we built a wooden arm for our robot... we kept a spare in the pit so that when the judges came by they could jump on it. Nobody with aluminum or steel arms was inviting judges to jump on their arms. They were either too valuable, or too flexible to demo this way. We had the arm in a three point bend test with the two largest judges bouncing up and down on it... and came away with the first of several design awards for working with wood.

In 2010 we went "all in" with a complete plywood chassis. No laser cutter, just a tablesaw, drill press and some baltic birch plywood. We tested it against some 1" aluminum tubing we had sitting around the shop, and all I've got to say is that the aluminum robots were lucky that we all had (wooden) bumpers on!

The teams with the lasers have since gone well above and beyond anything we did, achieving both lighter weights and more rigid frames. I believe it was 1899, from Seattle, that had a spare chassis in their pit one year and would invite judges to stand on it, taking our "just try and destroy it" schtick to a new level.

One way of looking at it is that wood is nature's carbon fiber. The lower density allows for great cross sectional structures and enhanced stiffness. As structures often fail by buckling or bending, the extra strength of metals is offset by the enhanced specific stiffness of wood. Add to that the low cost and ease of working with wood, and it can solve problems that metals cannot.

Oh... and should wood need repair, rather than running to the machine shop to get something welded, you can just grab some fiberglass cloth and 5 minute epoxy and have it rebuilt stronger than it was before your next match.

Please don't interpret this as saying that aluminum is no good... there are plenty of beautiful aluminum, steel, and composite drive trains and components out there... but wood is a very, very competitive material choice for teams that want to consider it.

Jason

[LuukVoesten4481]

Realy nice design!

Can you do a predication of the weight without the battery?
Keep on the good work guys .

[z_beeblebrox]

Originally Posted by Necroterra

Will there be a top plate or any cross beams? Also, about how many individual parts are there here? It looks like a lot less.
Are you planning to build one before build season for practice?

No top plate or cross beams should be needed.

There are 27 plywood parts in the chassis, 5 in each gearbox and 7 in each wheel.

Not sure; we'll see how much time we have. We will at least be prototyping the wooden wheels and experimenting with laser-cutting larger parts.

Originally Posted by LuukVoesten4481

Can you do a predication of the weight without the battery?

With electronics, no battery, ~34.7lbs. The wood chassis, including gearbox structure and bumper mounts, weighs ~10.2lbs.

[z_beeblebrox]

I added the superstructure mount. It weighs only ~3 lbs and can be tilted by removing two quick-release pins. I also moved the bumper mounts to the superstructure mount to facilitate access.

Images

[asid61]

Originally Posted by z_beeblebrox

I added the superstructure mount. It weighs only ~3 lbs and can be tilted by removing two quick-release pins. I also moved the bumper mounts to the superstructure mount to facilitate access.

Images

Very interesting design.
I might swap the pins for bolts, because the added stiffness is probably worth the extra 30 seconds to undo the bolts IMO.
It also might be a little weak due to the small contact area; bolting it down, rather than to the side, could be stronger.

[GeeTwo]

Originally Posted by Mr V

Yes pop rivets can be used with wood successfully. That is the way that all the angle aluminum, handles and latches are attached to the road cases that transport the fields and materials are made. Now when we made them for the PNW district we put a back up washer on them but the ones that FIRST made that I have looked at closely did not use back up washers.

It will also matter which direction you insert the rivet. You are less likely to need a back up washer if you have the mandrel/tool on the wooden side than on the metal side, though it may not look as neat if the metal is on the outside. We had this issue this week with riveting plastic to aluminum, in which this difference is probably greater.

[mrnoble]

I love your design, and I know from a good deal of experience that wood is a great choice for most things on an FRC robot. You've got me all nostalgic now; we've built three robots that were primarily made of wood, including one that was cabinet-grade solid Cherry. Don't succumb to feelings of inadequacy if anyone says wood is a second rate material. It definitely is not.

[s_forbes]

Originally Posted by z_beeblebrox

I added the superstructure mount. It weighs only ~3 lbs and can be tilted by removing two quick-release pins. I also moved the bumper mounts to the superstructure mount to facilitate access.

Images

Solid looking concept! Make sure the aluminum posts in the corners are mounted securely, since they'll take a big impact load when you run into stuff. How are they attached to the frame?
EDIT: just realized that the frame itself will still take the bulk of the impact loads, as the bumpers are contacting it

Also, good luck getting the bumpers on and off... the c-channel mounting hardware at the ends of the bumpers runs into your superstructure mounts in the process. Maybe just need angles instead of c-channels for those.

[z_beeblebrox]

Here's CAD for the drivetrain. It includes the CNC Wood wheel posted earlier, as well as improvements to the frame and bumper mount.