pic: Wood Coast Drive

[z_beeblebrox]

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[rutzman]

I heard at World's that you were limited in the size of the pieces that you could cut by the size of your laser cutter. Can you handle larger pieces now, or is this more of a theoretical design?

[z_beeblebrox]

Originally Posted by rutzman

I heard at World's that you were limited in the size of the pieces that you could cut by the size of your laser cutter. Can you handle larger pieces now, or is this more of a theoretical design?

All the pieces fit within our laser.

[AdamHeard]

I would remove all the diamond pocketing in the mock "rails". It cuts the fiber up so much, and it'd be hard to justify the weight it saves for the decrease in strength for a more traditional FRC game with contact.

[Necroterra]

Yeah, taking a second look at it, the belly pan definitely wouldn't survive a contact game. I think you could design the gearbox crossbrace to handle that though.

[z_beeblebrox]

Originally Posted by AdamHeard

I would remove all the diamond pocketing in the mock "rails". It cuts the fiber up so much, and it'd be hard to justify the weight it saves for the decrease in strength for a more traditional FRC game with contact.

That makes sense; will do. Edit: Removing the holes only cost ~.5lbs; not that big a deal, given how light the chassis is anyway.

Originally Posted by Necroterra

Yeah, taking a second look at it, the belly pan definitely wouldn't survive a contact game. I think you could design the gearbox crossbrace to handle that though.

The intent is to epoxy 1/8" plywood plates to the center of the belly pan, making it one piece. I'm planning on adding a brace between the gearboxes.

[asid61]

Very cool. 31lbs with a 6-cim drive is very impressive, too.

[dtengineering]

When you take a thin layer of fiberglass and epoxy it over wood the strength and stiffness goes off the chart... you'd have to figure out a way to fillet the corners a bit to allow the glass to flow smoothly over the edges.

Actually, once you got good at glassing you could replace the plywood with balsa and go for...

Oh, wait. You said this weighs 6.5 lbs? Yeah, I don't think the weight savings will be worth it. Wood is pretty amazing on it's own.

Jason

[carpedav000]

I'm new to the idea of wood construction, would it be worth it to replace the front and side panels with polycarbonate?

[Scott Kozutsky]

Originally Posted by carpedav000

I'm new to the idea of wood construction, would it be worth it to replace the front and side panels with polycarbonate?

The main advantages of wood (IMO) are that it's dirt cheap and can be laser cut very quickly and easily. Polycarbonate is neither.

[carpedav000]

Originally Posted by Scott Kozutsky

The main advantages of wood (IMO) are that it's dirt cheap and can be laser cut very quickly and easily. Polycarbonate is neither.

While both are true, I saw that someone was concerned about cutting the fiber up too much. I don't necessarily understand what that is, so I was guessing that is was something to do with structural integrity. Polycarbonate is (IMO) much more suited to take impact than plywood is, hence me asking the question in the first place.

[mman1506]

Originally Posted by carpedav000

While both are true, I saw that someone was concerned about cutting the fiber up too much. I don't necessarily understand what that is, so I was guessing that is was something to do with structural integrity. Polycarbonate is (IMO) much more suited to take impact than plywood is, hence me asking the question in the first place.

Polycarbonate cannot be cut on commercial laser cutter. It releases dangerous fumes when melted.

[z_beeblebrox]

Originally Posted by carpedav000

Polycarbonate is (IMO) much more suited to take impact than plywood is, hence me asking the question in the first place.

Plywood's not bad at impacts; it's springy and returns to shape when metal dents. Until our safety captain forbade it, I demonstrated that by hitting our demo swerve module with a hammer. We also ran over our prototype drivetrain with a car, with only minor damage.

We also use wood since it's so fast to make; we get turnaround times less than half an hour on our laser, while we'd have to cut Lexan by hand.

[Sperkowsky]

Originally Posted by EricH

Ah. (Makes me wonder why acrylic is found with FRC teams--and their "unskilled" drillers--around, but that's beside the point.)


Now, for the impact resistance: polycarb vs birch. Polycarb deflects, birch absorbs. They're about the same, but I'm going to have to give that to the plywood on strength-to-weight ratio. The main issue with birch ply is that it absorbs by getting dented or, eventually, splintering. (Acrylic never even enters this discussion, as the "standard" test for identifying unknown clear plastic is to clamp firmly and hit with the biggest hammer in the area--if it doesn't break, use the polycarb, otherwise it was acrylic.)

Plywood loses to poly on strength to weight. Lexan is crazy strong. I stood on a freely Standing peice of 1/16 lexan and it just bent I stepped off bent right back into shape no problem. I can't say the same for a piece of 1/16 plywood.

[Ether]

Originally Posted by Sperkowsky

Plywood loses to poly on strength to weight. ... 1/16 lexan ... 1/16 plywood.

FWIW: That's strength to volume, not weight.