pic: Wood Coast Drive V2

[z_beeblebrox]

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[nuclearnerd]

I love the laser-cut plywood bases you guys build. I hope this works well for you, because I want to try it myself some year!

What size bed do you need for this one? ~3 ft squareish?

[Mr V]

Very cool, however one point, everyone knows that you need to make it red to make it faster

[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.

[asid61]

Really digging the black. Are you just staining black, or will anything be green?
What made you go with 12 fps single speed over something faster like 16-17fps or a shifting gearbox?
What is the overall weight for this model, minus electronics?
That battery mount is gorgeous.
Cound you post screenshots of the plywood wheel in detail? That in particular looks really interesting.

[TheOtherGuy]

Looking good, Cal!

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.

It's mostly for convenience. We have a Trotec Speedy 300 (~29" x 17") laser cutter in our workspace that can cut up to 1/4" plywood. Since we have no CNC metal-working tools, the laser cutter is by far the fastest method to turn an idea into reality.

It's an excellent material, though, and surprisingly cheap. There are drawbacks (widening of side-loaded bearing and bolt holes, chipping, attachment method, etc) but we feel the benefits outweigh the issues. We may experiment with wooden gussets and aluminum tubing for the interface between the drive base and mechanisms, as well as the mechanisms themselves. While laser cut plywood is great, we like to stress that it's not always the right material for the job.

[z_beeblebrox]

Originally Posted by nuclearnerd

What size bed do you need for this one? ~3 ft squareish?

Our laser cutter bed is 29x17", but parts up to 29x34" can be cut in two operations, one for each end, by opening the machine's door so the material can stick out.

Originally Posted by asid61

Really digging the black. Are you just staining black, or will anything be green?
What made you go with 12 fps single speed over something faster like 16-17fps or a shifting gearbox?
What is the overall weight for this model, minus electronics?
That battery mount is gorgeous.
Cound you post screenshots of the plywood wheel in detail? That in particular looks really interesting.

-Our final color scheme is TBD.
-Gearbox ratios can be easily changed for free speeds from ~9 ft/s to >20 ft/s, depending on the distances normally traveled in the game. The chassis could easily be modified to use ball shifters, mounted like this.
-Excluding electronics and hardware not shown in the model and including motors and belts, the drivetrain weighs ~28.4 lbs.
-Images of the wheel can be found here. The only difference is that 6 dowel pins are used in each wheel in the album, as opposed to 3 in the robot's wheels.

[nuclearnerd]

When you decide to use plywood, do you do any calculations to guide your design? Do you use any of the formulas that civil engineers use for plywood (such as http://www.canply.org/pdf/main/plywood_designfund.pdf), do you use rules of thumb you can share, or do you just iterate until it works?

Are the captured nuts the only way you fasten the sheets, or do you glue them as well? Do you find the structure fails at the fastener typically, or some other way?

Thanks again for sharing

[Sperkowsky]

Does the plywood ever warp over time?

[TheOtherGuy]

Originally Posted by nuclearnerd

When you decide to use plywood, do you do any calculations to guide your design? Do you use any of the formulas that civil engineers use for plywood (such as http://www.canply.org/pdf/main/plywood_designfund.pdf), do you use rules of thumb you can share, or do you just iterate until it works?

Are the captured nuts the only way you fasten the sheets, or do you glue them as well? Do you find the structure fails at the fastener typically, or some other way?

Thanks again for sharing

Mostly we iterate Last year was the first with primarily plywood, so there was little worry about strength (no defense). We'll see if this year is different. Typically we just try to use good judgement on the placement of sheets. We didn't glue much on our last robot, but we're looking at gluing for tight spaces this year where we can't fit a captive nut. We have seen a few breaks near the slots in a recent side project.. better to learn that now than in 2 months.

Originally Posted by Sperkowsky

Does the plywood ever warp over time?

It does, our space doesn't have much protection from the environment, so we get occasional warping after a few weeks. We're going to develop a jig to flatten the sheets in the cutter before build season. On the robot it doesn't matter much - if it's designed right, the warping disappears when constructed.

[BBray_T1296]

Originally Posted by z_beeblebrox

Our laser cutter bed is 29x17", but parts up to 29x34" can be cut in two operations, one for each end, by opening the machine's door so the material can stick out.

How well do these two operations line up? It must be virtually impossible to get a perfect seam with this, but I am guessing you can get them good enough?

I would not be concerned so much with X/Y lineup as much as Z rotation when re-jigging the part. Could lead to some wonky wheel misalignment

[Necroterra]

This looks great. Looks much cleaner and more open than last year's. 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?

EDIT:

Originally Posted by BBray_T1296

How well do these two operations line up?

I can't speak for the team, seeing as I graduated last year, but I would assume that the flattening jig that Kevin mentioned would be a big part of making sure they line up. Additionally, plywood sheets are cheap, so if they can always cut another.

[s_forbes]

Originally Posted by Necroterra

(...) Additionally, plywood sheets are cheap, so if they can always cut another.

If a CIM costs more than all of your combined drivetrain raw material, I guess you can afford to make mistakes.

[GeeTwo]

Originally Posted by Mr V

Very cool, however one point, everyone knows that you need to make it red to make it faster

Everybody should know by now that red robots are unlucky, unless fielded by 1114.

Originally Posted by s_forbes

If a CIM costs more than all of your combined drivetrain raw material, I guess you can afford to make mistakes.

Amen to that!

[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)