Wood vs Aluminum

[=Martin=Taylor=]

Which is better? What I think you should be asking is "what am I building"

There are plenty of good uses for wood, and if used correctly it can offer comparable strength and durability to aluminum.

Our team needs to make a fairly large 5/8" thick plate this year for our tube grabber. After extensive discussion we determined that Baltic birch plywood (a marine grade plywood) would be perfect for this application. The wooden plate would be lighter then the aluminum and would offer reasonable strength and rigidity.

[artdutra04]

For many applications, aluminum can and should be the preferred choice.

However, I can think of several circumstances where high-quanity wood can be successfully used on the robot, and might even be a much better choice than aluminum. I can think of a few prominent teams who use wood chassis' with great success.

[dtengineering]

Each has their uses, but if we had to choose just one then I would go with aluminum for many of the reasons listed above.

Fortunately I don't and we have used wood for everything from a chassis (2004) to an arm (2005) that was 5' long, weighed 3 pounds and supported two PNW regional judges as well as the Xerox Creativity award they gave us for it, to the CNC machined turret, hand-turned 8" loader pulley, and maple bearing blocks and mini-bike motor mounts we used last year.

This year... well.... it is definitely coming back in our lift and end effector... but now that the challenge has been raised... hmmm... wooden sprockets... where can we fit one of those in to the design?

Don't be too quick to write off wood... when dealing with solid circular or rectangualar cross sections (no hollow tubes, etc.) it has one of the highest stiffness to weight ratios of any material, and in structural applications it is more fire-resistant than steel. (Uninsulated steel, that is... it gets hot and goes soft while the outside of the wood chars to form an insulating jacket.)

But yeah... for the robots... Aluminum if I had to choose.

Jason

P.S. Why, YES... my favorite airplane IS the Mosquito! How did you guess?

[zander_108]

Originally Posted by Hachiban VIII

Which is better? What I think you should be asking is "what am I building"

There are plenty of good uses for wood, and if used correctly it can offer comparable strength and durability to aluminum.

Our team needs to make a fairly large 5/8" thick plate this year for our tube grabber. After extensive discussion we determined that Baltic birch plywood (a marine grade plywood) would be perfect for this application. The wooden plate would be lighter then the aluminum and would offer reasonable strength and rigidity.

execpt honey-come aluminum...

[=Martin=Taylor=]

Originally Posted by zander_108

execpt honey-come aluminum...

My team actually has several peices of honey-comb almunium and I assure you it is far easily bent then wood.

We also have some honey-comb carbon-fiber, but its a real dog to work with...
Given the right grade and the correct tools you can make quality parts out of wood.

[Cody Carey]

We've used wood on our robots before... It has just been hidden from the public eye.

[AdamHeard]

Originally Posted by Hachiban VIII

My team actually has several peices of honey-comb almunium and I assure you it is far easily bent then wood.

We also have some honey-comb carbon-fiber, but its a real dog to work with...
Given the right grade and the correct tools you can make quality parts out of wood.

I've worked with honeycomb as well. If the cells are unprotected or the face sheets aren't up to part, the cells can easily damaged, or distorted and bent.

From what I've learned (2 years interning in the satellite part of Northrop Grumman). You want to make the honeycomb and face sheets the right size the first time, and never try to cut or reshape it. But then again, my background is where they make every part custom and remake parts rather than adjust an error in a current one.

One time, I had to scrap a whole bunch of panels and once the face became distorted or bent, they lost all their strength. Sure was a fun day.


Back to Al vs. Wood. There doesn't seem to be a universal right or wrong, it all depends on the application. I tend to prefer Aluminum because my team has been able to beg and borrow resources to deal with it, but if we had less we would probably use wood a lot more.

[waiakea2024]

aluminum is a lot stronger than wood is. also it doesnt swell when wet. (aluminum comes in handy here in hawaii)

[efoote868]

i can tell you that one of our key parts this year is being made out of wood..... i'll post pictures of it after the season is over.

[Rick-906]

Im a Lexan man myself, its fairly easy to work with and bends nicely.
this year we're playing with honeycomb carbon fibre, we havnt done a lot with it yet but we're loving the weight advantage it gives

if i had to chose, id go with aluminum.
when in comes down to picking an alliance partner, if both are the same in terms of ability, ill take the aluminum bot.

[Cody Carey]

Originally Posted by underwood

aluminum



ever tried to make a wooden sprocket?

http://www.chiefdelphi.com/media/photos/26540?

[Andy A.]

There have been many highly successful robots that are made primarily out of wood. Contrary to popular opinion, the wood doesn't 'just break'. It will flex a great deal before deforming. When it does deform, it is typically a very localized thing. Imagine ramming an aluminum bar hard enough to plasticly deform it. The entire bar is now bent. Ramming a piece of plywood might dent, even break through, the area that was hit, but the rest of the wood will not be affected.

Is it the right material for every application? Of course not. But it does have it's uses, and for the team with limited tooling it's a godsend.

Team 95 has been using wood, mostly 1/2" Baltic plywood for years with great success. Heres a sample of four 95 robots, 1998 through 2004 that used at least some wood.

http://www.lrt-uppervalleyrobotics.c...es/page_1.html

http://www.lrt-uppervalleyrobotics.c...s/page_17.html

http://www.lrt-uppervalleyrobotics.c...es/page_3.html

http://www.lrt-uppervalleyrobotics.c...es/page_2.html

http://www.lrt-uppervalleyrobotics.c...es/page_1.html

Many of those robots all preformed a similar task; picking up up balls off the ground. Rather then reinventing the wheel, the team chose to adapt an old design. By 2002, it had been pretty well perfected and the 'popcorn popper' was the result. A few more similar robots have been made since, all with the same frame layout and materials. The wood allows for a frame that is quick to produce, protective and just the right amount of flex. It could have been done with aluminum, sure, but plywood did everything just as well.

Use the material you are most comfortable with and best able to manipulate.

-Andy A.

[Liz Smith]

I heard what you said about not just saying "it looks cooler", but I do consider that to be a factor as well. Both aluminum and wood can make sucessful robots, but I think that most people think of metal as being stronger than wood. With this in mind, I think that if two robots had the same skills, and the same W-L record, an aluminum bot would be picked for an alliance over a wood bot.

[Lil' Lavery]

Originally Posted by Pika1579

I heard what you said about not just saying "it looks cooler", but I do consider that to be a factor as well. Both aluminum and wood can make sucessful robots, but I think that most people think of metal as being stronger than wood. With this in mind, I think that if two robots had the same skills, and the same W-L record, an aluminum bot would be picked for an alliance over a wood bot.

Wood doesn't always look worse though. As Tom posted earlier, it can be painted quite easily.
Plus, some wood bots can look quite slick even without paint

[MrForbes]

Aluminum is usually a better choice, as you can do more with it. An aluminum tube can withstand a very large load, and weigh very little compared to a solid wood board of the same strength.

Wood may be easier to work with if you have few machine tools, although clever design can get you very far with sheet, angle and tubular aluminum and a few hand tools. Rivets are strong, light and inexpensive. If you have access to a sheet metal shear and brake, you can make many aluminum parts that are strong, light, and rigid. As an example, we made a prototype ramp section that would weight less than a pound per linear foot, and can support 400 lbs over a two foot span.

Both wood and aluminum have been used very successfully to build airplanes, so it should be obvious that they both can be used to build strong, light structures, if the necessary design work is done.