05-02-2009 00:18

s_forbes

Re: pic: Team 973 Upper Frame

Nice! We're using the same stuff for the top structure on our bot; 3/4" 13 ply baltic birch. I have to say... after using wood a whole bunch this season it is now my favorite building material.

05-02-2009 01:03

R30

Re: pic: Team 973 Upper Frame

Its nice stuff.
I like OSB though for indoor use. OSB and 2 by 4 studs is what I build everything out of

05-02-2009 02:27

Michael Corsetto

Re: pic: Team 973 Upper Frame

Are those holes supposed to be for rollers going the width of the robot, and if so, do I see a diagonal conveyor belt going from the lower right to upper left, with a dumping exit point on the upper right hand corner of the plywood? Looks like a solid frame design, post a final pic soon!

05-02-2009 02:50

dtengineering

Re: pic: Team 973 Upper Frame

Aniline dye... then lacquer, makes it look REALLY good. If you can CNC a hole ten thou under (in diameter) and press a bearing into that stuff... well, we haven't had one come out yet.

Jason

(okay... we did GET one to come out by pounding on it with a hammer from the back side....)

Edit... I meant to add that for a solid material (as opposed to hollow tubes, or foam cored composites) wood has one of the highest stiffness to weight ratios of ANY material, including carbon fibre. In architectural applications large wooden beams are actually more fire resistant than steel. (The outside chars forming an insulating layer, but the inside maintains strength, while steel transmits heat throughout and goes soft.)

05-02-2009 09:36

sdcantrell56

Re: pic: Team 973 Upper Frame

I am a convert as well. After building with wood this year I don't see any reason to build a drivetrain from metal again. We have used both 12mm okoume which is much lighter than baltic birch, and now we are using 3/4" baltic birch on our turret mount and bumpers. Our wood frame has helped us achieve a drivetrain with electronics and battery under 45lbs.

05-02-2009 09:57

Rick TYler

Re: pic: Team 973 Upper Frame

sdcantrell56 beat me to it -- Baltic birch is great for furniture and other applications where weight doesn't matter too much, but for boats -- er, I mean robots -- Okoume is the kind. Here's a link to a project I did with 4mm Okoume: http://www.jemwatercraft.com/images/...ahPictures.htm.

05-02-2009 10:04

sdcantrell56

Re: pic: Team 973 Upper Frame

The only negative to okoume is cost. A sheet of okoume is approximately 2.5 times more expensive than baltic birch, but the weight savings is quite significant. The other nice thing about okoume is if you buy the marine grade bs1088, it will be the most consistent, highest quality wood you will ever find.

O and PS it cuts wonderfully with a laser

05-02-2009 10:11

MrForbes

Re: pic: Team 973 Upper Frame

Another is availability. We found nice 5 x 5 sheets of 1/4, 1/2 and 3/4 (actually the metric equivalent) Baltic Birch at our local Ace hardware store. I haven't seen any okoume in town.

Perhaps another could be crushing strength....I'm just guessing, but usually a less dense wood will crush more easily than a denser wood. This affects how fasteners are used.

05-02-2009 10:16

sdcantrell56

Re: pic: Team 973 Upper Frame

Yes okoume is quite difficult to find. In fact there is only one dealer of okoume in all of Atlanta and we actually got very lucky that they had any in stock. Okoume will gouge slightly easier than baltic birch or meranti, but when bumpers are required, this negative is completely negated.

I would not hesitate to build with baltic birch, and actually if we use wood in future seasons, probably will go with baltic birch due to availability and cost but if you can find okoume and can afford it, the weight savings is quite noticeable.

05-02-2009 10:19

Rick TYler

Re: pic: Team 973 Upper Frame

Availability of Okoume isn't very good outside of areas with a marine industry, and it is really pricey. It's also softer than Baltic birch. BS1088 is really nice, but if you can find it the second-quality 6566 is just as strong and fine for robots. The difference is that 6566 is allowed to have more surface imperfections than 1088. I can't say that I've noticed any other differences in building boats.

To some extent I was having fun here -- baltic birch should be fine in this application.

Occasionally I've seen references on CD to using various hardwood plywoods on robots. Don't do it. Hardwood plywood (oak, maple, cherry, etc.) is a thin veneer of hardwood over a softwood core, and that core can and does have gaps, voids, splits and other horrid imperfections. OK for cabinets, but not for uses where you count on its strength.

Regardless of wood species you want a plywood with an odd number of layers where every layer (including the surface) is the same thickness, and the core is made of the same species as the face.

Maybe our team needs to add FRC to our program just so we can build a WoodyBot. The name would certainly fit in with FIRST.

05-02-2009 10:22

MrForbes

Re: pic: Team 973 Upper Frame

Apparently the cabinet grade Birch plywood sold at the building supply places, is actually a veneer plywood like you describe.

We noticed quite a difference between genuine Baltic Birch plywood and the cabinet Birch veneer plywood. Unfortunately the good stuff is noticably heavier...

05-02-2009 11:18

Elgin Clock

Re: pic: Team 973 Upper Frame

Ever get that OSB stuff wet? It's not fun to deal with then.
It basically turns into a sponge faster than any wood product I've ever seen. Not good.