pic: GBX-123 chassis example

[AdamHeard]

Originally Posted by asid61

Can't argue with that. However, it's going to be tricky to convince the team that plywood makes for a good bellypan.
Usually our issue is with weight/design, not money.

Why? Analayze it from an engineering sense and explain the tradeoffs.

Most teams are several orders of magnitude away from being optimized enough for bellypan choice to even matter much anyway.

I posted in a bellypan thread the tradeoffs between several options but am on mobile and can't hunt it down.

[Rachel Lim]

Originally Posted by asid61

What are the advantages over G10 though? Is it lighter?

Originally Posted by AdamHeard

I posted in a bellypan thread the tradeoffs between several options but am on mobile and can't hunt it down.

This one?

http://www.chiefdelphi.com/forums/sh...0&postcount=48

Originally Posted by AdamHeard

I'm going to toot my own horn for a moment....

We've done

1) 1/16" G-10/FR4 Garolitem (2009, 2009 offseason, 2010, 2012)
Pros
-Looks darn good (glossy black)
-Very Stiff/strong
-Easy enough to drill, but vacuum the mess!
Cons
-Expensive
-Waterjet delaminates it, so they pierce 3-4" away from final cut and feed over. We did some external slots to act as rivet holes, then match drill rest on robot.

2) 6mm (~1/4") 5 ply baltic Birch (2012 offseason, 2013 season, 2014 offseason, 2015 season)
Pros
-Easy to cut
-Cheap
-Very HIGH stiffness to weight
-Can thread fasteners right into it for components
-When painted, looks nice enough.
Cons
-Termites
-Ignorant teams look down on it. This is fine, it just points out their lack of understanding of material properties and basic math

3) .125 6061-T6 diamond pattern (Waterjetted/lasercut). (2011 season, 2011 offseason, 2014 season)
Pros
-Hypetrain
-Forces you to do layout
Cons
-Expensive resource wise
-Not as stiff as the other 3 items
-One and done, no mods

4) .25 ABS (if you count 294). This is similar enough to (2007 season)
-It's really just a heaver version of plywood. I'd use plywood over this.



I highly recommend the wood, no need to laminate or do anything to it. Just use it as is. If your frail ego can't handle the wood, garolite is a great option at 1/16" thick but requires more tools to work with.

The diamond bellypan is nice... but in nearly all cases is a huge resource waste. Many subsystem gearboxes and gussets could be cut in the same time.

[asid61]

Originally Posted by AdamHeard

Why? Analayze it from an engineering sense and explain the tradeoffs.

Most teams are several orders of magnitude away from being optimized enough for bellypan choice to even matter much anyway.

I posted in a bellypan thread the tradeoffs between several options but am on mobile and can't hunt it down.

We're usually somewhat of a tradition-led team. We recently changed officers, so I'll have to speak with the new officer team about their thoughts on plywood. Compared to the punched 1/8" 5052 we use now, pretty much anything is better.
Garolite makes it look more "professional" compared to plywood, but I feel like we could just paint over it.

I've seen your bellypan threads, and I thought they were very helpful. It's also reassuring to know that your team has tried many different options and optimized.

As long as we don't have a game like this year's and we don't build too big, we're probably okay weight-wise. Both Garolite and plywood are so easy to use that I'm reasonably certain we can swap it out on one robot if the need is dire.

[chrisfl]

Another really lightweight pption is 1/2in or3/16in corrugated plastic. That stuff is sure light and great for electronics boards. We've used it the past few years and have seen many teams using it before. You can even get it in colors to look good

[philso]

Originally Posted by asid61

We're usually somewhat of a tradition-led team. We recently changed officers, so I'll have to speak with the new officer team about their thoughts on plywood. Compared to the punched 1/8" 5052 we use now, pretty much anything is better.
Garolite makes it look more "professional" compared to plywood, but I feel like we could just paint over it.

You and your team should define what "look more professional" really means, what your teams overall values are and how much priority and resource your team is willing to put into building a professional looking robot. You should also look around CD for the various threads about wood robots. If done right, they can look just as professional as a robot made from metal. While it is great that your team has a history of tradition to build on, FRC requires that teams think outside of the box (and sometimes inside of the box).

How good the robot looks depends more on how you use the material and your workmanship. There was a mostly wood robot in the Tesla Division that exhibited better workmanship and looked more professional than 80% of the other robots in Tesla. Of course, there were metal robots that also looked better than 80% of the other robots in Tesla.

[MichaelBick]

The biggest negative (performance wise) to plywood over G10 is that it is thicker. If ground clearance is important it can make a difference. Otherwise its much easier to manufacture and secure components into(pre drill and then self tapping screws). The extra weight is negligible because it is so low to the ground.

[highlander]

Originally Posted by philso

There was a mostly wood robot in the Tesla Division that exhibited better workmanship and looked more professional than 80% of the other robots in Tesla.

I have to address a pet peeve here: anecdotal evidence. Stating a random example doesn't prove or disprove anything.

Has anyone actually performed a statistical test on how wooden robots perform vs how metal robots do? I don't know or suspect an answer, it just would be interesting to know.

[PAR_WIG1350]

Originally Posted by highlander

I have to address a pet peeve here: anecdotal evidence. Stating a random example doesn't prove or disprove anything.

Has anyone actually performed a statistical test on how wooden robots perform vs how metal robots do? I don't know or suspect an answer, it just would be interesting to know.

I'm not sure there is large enough sample of wooden robots to draw any conclusions. Does anybody have a list of wooden robots?

[asid61]

Originally Posted by highlander

I have to address a pet peeve here: anecdotal evidence. Stating a random example doesn't prove or disprove anything.

Has anyone actually performed a statistical test on how wooden robots perform vs how metal robots do? I don't know or suspect an answer, it just would be interesting to know.

You would need a massive sample size of wooden robotcs IMO. I mean, done right (like the Bit Buckets), you can have a robot as competitive or more competitive than a metal one. It really comes down to strategy, because I haven't seen any significant differences in capability between the two yet.

[MichaelBick]

Originally Posted by highlander

I have to address a pet peeve here: anecdotal evidence. Stating a random example doesn't prove or disprove anything.

Has anyone actually performed a statistical test on how wooden robots perform vs how metal robots do? I don't know or suspect an answer, it just would be interesting to know.

Anecdotal evidence does prove that something is possible.

Statistical evidence can only prove a correlation. It cannot prove causation. Therefore there could be statistical evidence that wood robots perform better than metal robots, but the evidence could not show that robots perform better because they are made out of wood. For all we know wood robots could perform better because they are made by better teams.

[Jared]

Originally Posted by highlander

I have to address a pet peeve here: anecdotal evidence. Stating a random example doesn't prove or disprove anything.

Has anyone actually performed a statistical test on how wooden robots perform vs how metal robots do? I don't know or suspect an answer, it just would be interesting to know.

Stating an anecdotal example does prove something in this case - that it's possible to build a wooden robot that looks professional, which is what another poster was questioning. It does not prove that wooden robots tend to be good robots or that a good wooden robot is even possible. He only said that there was a professional looking wooden robot in Tesla this year.

[AdamHeard]

A plywood bellypan is easily rattle-canned black, and no one would ever know it's wood.

The wood we use is a 5 ply baltic birch at 6mm thick. It's density is .025 lb/in^3.

For a structural bellypan two things are happening load wise.

1) Shear loads are being transferred corner to corner.
2) frame torsionally loads are reacted.

Most reasonable materials easily satisfy #1 if attached properly. The second is harder, and is one of the advantages of the plywood (over the garolite) due to stiffness. The increase in stiffness mainly comes from the much greater thickness.

We like the wood because it's so easy to work with, and meets the performance specs we need. The garolite works, but is much harder to get cut how we need and costs far more.

[evanperryg]

We use perforated aluminum sheet like this stuff. It's surprisingly strong, and offers plenty of pre-made spots for zipties and other cable management hardware. It's not particularly heavy, either. The one thing I hate about it is that the holes don't line up with component holes, but some precision drilling can make up for that.

Anyway, cool gearboxes. I couldn't tell what you meant by a dropped swerve until I saw the modules in a base.

[asid61]

Originally Posted by evanperryg

We use perforated aluminum sheet like this stuff. It's surprisingly strong, and offers plenty of pre-made spots for zipties and other cable management hardware. It's not particularly heavy, either. The one thing I hate about it is that the holes don't line up with component holes, but some precision drilling can make up for that.

Anyway, cool gearboxes. I couldn't tell what you meant by a dropped swerve until I saw the modules in a base.

I've found that aluminum bellypans tend to be heavier than wooden ones, especially when just perforated with a hole pattern vs. putting in a diamod cutout. In order for aluminum to compete, is have to be very thin (around 1/16").