Lignin fiber matrix (wood) as a chassis material

[dtengineering]

Originally Posted by slijin

I'll never be as confident in a wooden one as an aluminum one (we've experienced too much chassis damage and warping for me to be comfortable with wood), but that's just me.

I see several posts here from my fellow long-time "wood evangelists" here on CD. I'd be happy to put our baltic birch breakaway 'bot up against pretty much any aluminum frame and see which one comes away damaged and warped. We've built aluminum frames for years, but we've never built one as stiff and sturdy as this 100% wooden one.

Wood has turned out to be a very appropriate material for students to use, for many of the reasons listed above... and you don't need a laser cutter to do a nice job of it. Although we do have a CNC router, which makes some tasks easier, the majority of our construction is carred out using traditional wood shop power tools. Check out the guts of the machine here, and you'll see that there are no fancy joinery, tabs, or epoxy... just a bit of carpenter's glue and some screws. Our practice bot didn't even have the carpenter's glue... it was just screwed together, and held up just fine (although it was considerably weaker than the glued competition frame). On a related note, I'd question the need to use epoxy... my lab tests confirm these made by Fine Woodworking Magazine, that standard white or yellow PVA glue actually outperforms epoxy as an adhesive for wooden joints. Not to mention it is cheaper, easier to clean, and much less messy to work with. The only time we use epoxy is for the occasional quick repair at an event. (Hmm... another advantage of wood... no trips to the machine shop.)

I am really surprised that you got a negative reaction to a wooden frame. We've received outstandingly positive reactions to our use of wood since we used it for our "unbreakable" three pound arm in 2005. I have to say that a clear coat of laquer (with perhaps http://www.chiefdelphi.com/media/photos/32608) gives it that finishing touch. We've had our use of wood cited as a contributing factor in three design awards and one judge's award over the course of six years at three different events.

Even when we don't do the whole chassis or frame or drive module out of wood, we still made it a prominent part of our lifts and mechanisms. We are very proud of our use of wood, and recognize that their will be "doubters". That's why when we built our three pound arm, we brought along a spare for the judges to JUMP ON. That was a key to our very first FRC award, and the beginning of our team's minor reputation for using wood.

Equally significant from the point of view of myself and the other mentors is the outstandingly positive feedback that we have received from other teams, and the knowledge that we have inspired others to consider using a biodegradable, low cost, environmentally-friendly material as part of their design. It is especially cool to see that now that our team is no longer around that others are doing an even more impressive job of creating wooden wonders. Check out 1899's arm if it had been clear-coated instead of painted it might have been the single most beautiful arm I've ever seen at an FRC event. (It's still up there, though... I just like to see the grain.)

Wood is good. Go for it!

Jason

[timmmoore]

Jason, we should have shown you our spare arm at Seattle, it had a clear coat finish. We used that version at St Louis, see
http://www.popularmechanics.com/tech...c=rss#fbIndex5

We used wood glue except when glueing to non-wood, for the same reasons you stated.
We took a major hit on the arm in St Louis, a rough estimate was a bot hitting our arm moved our bot ~12" sideways, a bit of glue and we were good to go for our next match.

[Gdeaver]

Good. First teams have had a metal addiction for years. I've been trying to get teams I've work with to vary their robot diet to include some fiber. Plywood is a very viable construction material for first robotics. But, mentors should not stop there. Our students do not get a traditional shop education any more. Tech Ed has turned into an arts and craft experience. We need to expose students to the many material choices we have available and teach them how to work with them. Why don't you over the summer put together a white paper on wood and robots construction techniques. Your design and joining methods are why the robot holds up. Share your design methods. This year we used some Birch 5mm plywood and laminated it with 5.7 oz. carbon. We have several students that are now proficient in vacuum bagging. It's not that hard. We also use thermoplastics that are thermo formed and vacuum formed. ( polycarbonate and polypropylene). Fiberglass pultrustions were used for the 4 bar arm. I'm very happy that in a 6 week period our students received the shop education that they should have had in school.

[FrankJ]

Wood is well used in small boats & small airplanes were weight & strength is important. Lots of good information can be found by Google. West marine is one source among many. It is amazing how strong a joint is made by laying over a strip of fiberglass & epoxy.

One wood bot is kinda weird.
Two wood bots is a cult.
Three wood bots is a revolution
Vivia la Revolution

[AdamHeard]

I agree with all of your points except for the lightweight aspect.

If aluminum is used properly in efficient frame design, it is definitely coming in lighter than wood. No doubts.

The past two seasons, the sum total weight of all frame members (upper and lower) was around 15 pounds. this includes bellypan and bumpermount.

[MrForbes]

You might be right Adam, but I will point out that most aluminum robots do not have very efficient frame designs.

Designing a light, strong, robust wood robot takes some effort. Building it can be relatively quick and easy, but only if you put in the time designing it well.

I wouldn't build a wood robot just to have a wood robot. There are many considerations when choosing a material. I like to use the "best" material for each part. That could be plastic, wood, aluminum, steel, fiberglass, lexan, titanium, etc. My idea of what's "best" usually is based on obscure factors such as material availability, tools, working knowledge, cost, toughness, etc. Ultimate tensile strength is pretty low on the list for most parts of the robot.

[Dick Linn]

Team 975's first robot was wood, even the drive wheels. Only cheap 1/2" plywood and 1" x 4" Pine (max) was allowed by the rules that year, IIRC.

We painted "Team 975 featuring W-Fiber" on a large piece of cedar siding. The field announcer would wave that around when our team was announced, LOL. I still have that sign hanging in the garage.

Thereafter, we had a saying, "Wood is Good". We tried to incorporate at least some wooden elements whenever possible.

[EricH]

Adam, have you ever seen an R/C aircraft built mostly out of aluminum? (I have, but it was a custom build for SAE Aero Design--and that particular airplane was still about 1/2 balsa.)

My contention is that it's not about what material you use, it's how you use it. Build the robot out of steel, but mess up something, and it will break. You could also build out of mainly plastic, and have it never break (1714, for example), because you did it right.

[AdamHeard]

I wasn't criticizing wood, just clarifying a point. Too often I see students on here catching onto phrases/ideas they've seen and repeating them without ever questioning their validity (the drop on 6wd is awful, etc...).

Personally, when I look at a team the thing I admire most is that team using their unique resources as best they can to create the best machine they can. If a team can build a better robot out of wood, cool! Just because aluminum is the best choice for my team (and I'd wager a good deal of teams), does not mean I'd claim it's the best choice for all teams.

I'd stress that young designers focus more on GOOD design than material choice. There is no magic material out there; every material has a useful application, and what will determine success of a design far more than material, is the quality of the design itself.

330 and 1726 have both made machines and mechanisms I thought were awesome out of wood; and it was what their resources dictated. Good move!

Originally Posted by EricH

Adam, have you ever seen an R/C aircraft built mostly out of aluminum? (I have, but it was a custom build for SAE Aero Design--and that particular airplane was still about 1/2 balsa.)

My contention is that it's not about what material you use, it's how you use it. Build the robot out of steel, but mess up something, and it will break. You could also build out of mainly plastic, and have it never break (1714, for example), because you did it right.

That's comparing apples to oranges. It's just as inaccurate as me asking if you have ever seen modern fighterjets or spacecraft made of balsa.

[Mark Sheridan]

Originally Posted by AdamHeard

I wasn't criticizing wood, just clarifying a point. Too often I see students on here catching onto phrases/ideas they've seen and repeating them without ever questioning their validity (the drop on 6wd is awful, etc...).

Personally, when I look at a team the thing I admire most is that team using their unique resources as best they can to create the best machine they can. If a team can build a better robot out of wood, cool! Just because aluminum is the best choice for my team (and I'd wager a good deal of teams), does not mean I'd claim it's the best choice for all teams.

I'd stress that young designers focus more on GOOD design than material choice. There is no magic material out there; every material has a useful application, and what will determine success of a design far more than material, is the quality of the design itself.

Just to elaborate on your point. If two frames that are perfectly designed, the aluminum one will be lighter than the wood one.

Now for teams, like mine, who don't have ideally designed frames, will have ones that are not lighter or stronger than the wood frame. This whole topic fascinates me because we build aluminum frames without a metal shop; yet we work in a fully equipped wood shop. We weld our own frames without a welding table, so there are quality issues. I realize that our woodshop is a powerful unused resource.

I feel there are a lot of teams that work out of a wood shop instead of a metal shop that ought to take a look at these teams.

[jvriezen]

Our bot had a plywood eboard and a plywood elevator. We painted it green and many thought it was aluminum. Finalists at Duluth MN as well as judges award.

[jwfoss]

I've always been interested in using wood as the primary building material for a robot. However after kickoff the designs almost always go to aluminum.

Though you might be interested in this:

Splinter - Supercar made mostly from wood.
http://www.joeharmondesign.com/index.html

[Ian Curtis]

Originally Posted by EricH

Adam, have you ever seen an R/C aircraft built mostly out of aluminum? (I have, but it was a custom build for SAE Aero Design--and that particular airplane was still about 1/2 balsa.)

Have you ever seen an R/C plane with even *close* to the same structural requirements of an FRC chassis? NO!

The great thing about aircraft is that most of the loads are pretty specific. An FRC base is going to get hit -- hard. An airplane is not. You build a nice sturdy spar (balsa is a great material, but there are many others) and then you put lots of ribs who mostly serve as a surface to attach a covering to. You build a nice sturdy wingbox, and hang a lightweight fuselage off it to put your payload in. You have a sturdy motor mount tied in somewhere, and a sturdy tailboom to hang a lightweight tail off of. You put in a couple of mounting holes for servos that weight less than a 1/10th of a pound, stick a receiver somewhere and you have an airplane.

When a balsa structure suffers an impact event, it is typically a total loss.

(I'd love to build a tabbed wooden FRC chassis though)

[Zflash]

We have used the tabbed base construction method since 2006 on 1319. When I was on team 507 we used it on our robots in 2001, 2002, and 2003. It is a great method of construction no matter the material. As many have mentioned it comes down mostly to design techniques and putting the effort there more than anything else. The chassis' have never had any failures we make them out of aluminum and weld up the tabs, this is most likely lighter than wood constructed in this manner however it requires a skilled welder.

As far as judges and awards. We have won many technical awards, a few events and always at least make the dance. Up until 2009 we have always spray painted our parts with paint purchased from Wal-Mart or Lowe's. We still paint some of our parts however our chassis' since 2009 have been powder coated by a gracious sponsor.

I have not seen 1771's robot this year however I have always admired your team's work since we first competed with you at Peachtree in 08. I am sure your team has something to be proud of but understand you wanting the validation a technical award can bring. We to did not score a technical award this year and we had several unique features that worked well. We wonder if we possibly looked to good with our powder coat and painted parts.

Hope to see the 1771 machine at GRITS and keep on with the wood since it is obviously working on the field for you where it matters most.

[Tristan Lall]

Originally Posted by Ian Curtis

Have you ever seen an R/C plane with even *close* to the same structural requirements of an FRC chassis? NO!

There's always an exception...I have.

Actually, I had a significant part in building one for a project as an undergrad. I had a less significant part in originally designing it, so I can freely concede that it could have been lighter. Nevertheless, it was a 14 ft span, 12 ft long, 80 lb operating empty weight/100 lb loaded weight aircraft, designed for a strange combination of aerial reconnaissance and parachute-based payload delivery.

It was built with a tabbed plywood truss fuselage (basically, a long box, tapered at the ends), with foam-cored, balsa-skinned wings with an aluminum spar.

And although it could have been lighter, one of the practical objectives of overbuilding was to minimize the impact of unusual conditions. It was one aircraft filled with thousands of dollars of stuff, and we were somewhat risk averse. Possible scenarios included payload failures (you wouldn't want a tangled chute to foul the aircraft and break an elevator off), rough landings (mostly avoided), and even being able to recover from skidding off of an iced runway (the taxi tests were harrowing: we didn't have any excursions, but we did manage to bend the landing gear). And yes, since this was the first time scratchbuilding an aircraft for just about everyone, nobody wanted the wings to come off in flight.

Ultimately, it's a convenient counterexample, but I do of course agree that ordinary aircraft don't need to be built to withstand FRC chassis loads.