pic: 3/4" Plywood Frame

[,4lex S.]

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[MrForbes]

We built a plywood chassis last year, it was a different design, as the wood was used to support the axles directly, and it was based on the "box" concept. Not much twisting going on with a box!

http://www.chiefdelphi.com/forums/sh...ad.php?t=71902

The strange overal design was due to having to harvest balls from the floor, and the trailer let us use a wide 4wd design instead of the narrow 6wd that most games seem to require.

[Jared Russell]

Without some "3D" supports, I'd worry about warping in a chassis like this. It's looking good, though - you are almost there.

[AndyB]

Originally Posted by Jared341

Without some "3D" supports, I'd worry about warping in a chassis like this. It's looking good, though - you are almost there.

I might look into a design like this within Inventor and do some stress testing on it. Very interesting idea. I'd be most concerned with bending or warping between the gearboxes, but that could be pretty easily remedied with a couple bars of 1x1 aluminum. I like the idea though.

[gburlison]

Originally Posted by AndyB

I might look into a design like this within Inventor and do some stress testing on it. Very interesting idea. I'd be most concerned with bending or warping between the gearboxes, but that could be pretty easily remedied with a couple bars of 1x1 aluminum. I like the idea though.

A little warping in the right direction might help keep all 6 wheels on the ground if the floor is not completely flat. I would reinforce the long side first, to help keep chains between the wheels on the sprockets.

[DonRotolo]

There are many grades of plywood; you want aircraft plywood if possible. It uses many layers of light wood.

regular plywood, like used for house construction, uses only a few layers, and is not as strong (or light) as aircraft plywood. Marine plywood uses a few more layers, but isn't as light. You might consider making your own plywood, two 1/4" aircraft ply outer layers with foam and 1/4" spacers in-between - lighter and just as strong.

For stiffness, use pieces mounted 90 degrees to the plane - glue and screw.

It would be heavier than aluminum, but plenty strong. Use some aluminum U channel along the outer edge to give very good impact strength.

But nice concept!

[Bertman]

We have made several plywood frames over the years. If you use 3/8" plywood (I would use Baltic Birch which has at least 5 layers and no voids) as a top with a 1/4" Baltic Birch Ply bottom - sandwiching 1/2" -3/4" X 3/4" spacers around the perimeter, all glued and clamped, with solid blocks at mounting points for pillow blocks and super-structures you will create a hollow chassis which is light and incredibly strong and stiff. For inspiration look to light wieght, wooden boat construction. Go for it and good luck.

[Tristan Lall]

Originally Posted by AndyB

I might look into a design like this within Inventor and do some stress testing on it.

Does Inventor now have an FEA plugin that can do laminated composites? (Plywood is non-isotropic and non-homogenous, so a regular solid model simulation won't perform well except for very small stresses—where it probably wouldn't matter.)

[R.C.]

Just an idea, you may want to try making a chassis like 1771 or 1726.

-RC

[kramarczyk]

Originally Posted by Tristan Lall

Does Inventor now have an FEA plugin that can do laminated composites? (Plywood is non-isotropic and non-homogenous, so a regular solid model simulation won't perform well except for very small stresses—where it probably wouldn't matter.)

2009 does not. 2010 is supposed to have a substancially upgraded package, but I do not believe composites are included. It does open the door for analysis of assemblies.

[Cyberphil]

I dono if im missing something, but there is almost no clearance on that at all. I have always found that you should have some more clearance than that.

[Gdeaver]

Plywood is mother nature's composite. If you add in some epoxy and glass, Kevlar or carbon fiber cloth, you can make a very light and durable wood structure. Our team this year is contemplating making our bottom electronics board out of 5mm birch plywood laminated on both sides. The panel in our design is also a structural part of the frame. To keep the weight down requires vacuum bagging. We could buy other material for this part or buy pre made panels. I'm going to work with the students laminating the panel to give them some exposure to composite construction. There are many good tutorials on the web showing how to do this. However it does take some practice. It wood be a good off season project. You don't want to decide to do this during build season with out some practice. Allot of FRC teams are addicted to metal. They should get some fiber in their robot diet.