Wood vs Aluminum

[ThomasP]

If you had to choose between wood and aluminum where both would cost the same and have the robot ready within the same period of time, which would you choose and why?

Please don't vote for either and just say "because it looks cooler", I'd really like some technical answers to this to give the team all the information they need to make a good decision.

[Zoheb N]

I would personally go with aluminum from the stand point that if your robot does get rammed alot during competition you have the ability to beat it back into shape where as if you have it made out of wood it will chip away and become irreplaceable

[Mike Starke]

Originally Posted by Zoheb N

that if your robot does get rammed alot during competition you have the ability to beat it back into shape where as if you have it made out of wood it will chip away and become irreplaceable

^Totally agreed.
I have to lean towards trusting welds more than trusting screws or nails, when it comes to either assembling the lower flame, or when it comes to attaching upper frame pieces. Also, if you made it so the two frames would way the same, that would be some awfully thin and unstable wood. 3/4 inch square aluminum is plenty strong for most frames, and is very light.

[Mike Norton]

I have used wood on 10 of the 12 robots built. The right wood works great. Due to the high impact it will take without breaking. Team 61 robot has been know to hit a lot of robots. But the robot frame has never failed. A wood frame works great to start from due to you can place any part on it with out a lot of work. Just pick a spot and put it there. where the Aluminum you need to do a little more work to make it fit.


Wood and the parts it take to put on different devices are cheap. The hardest thing with wood is knowing how to use it in the best way to get the most from it.

[Tom Bottiglieri]

This is my first year NOT working with wood for a drive base, and I must say I don't really have a favorite.

Wood is, for the most part, easier to work with. With little to no resources you can cook up a pretty solid base in less than a day. Electronics mount up nicely to it, and you can even give it a slick automotive paint job. Beyond that, with the proper reinforcement you can slam the thing into walls all day and not have to worry about it bending or breaking.

Aluminum is a bit lighter, and more customizable. You can get some pretty unique shapes and work motor mounts directly into your parts.

I don't really see a big difference in terms of strength (for the purpose of a drive base) between wood and aluminum. Wood has the tendency to gouge, which isnt all that pretty, but for the most part it holds up quite well.

So, I guess its all a matter of personal preference and experience. YMTC.

[travis]

Here are some useful properties of Birch (home depot grade plywood material, aircraft grade is void free with superior propeties at about 3X the cost) and 6061-T6 aluminum (all in KSI):

aluminum wood
tensile load at failure 45 10
modulus of elesticity 10,000 2,000

Here is that same table adjusted for density:

tensile load at failure 16.7 16.7 (ahhh perfection)
modulus of elesticity 3703 3333

Price of a clamp = $5, price of a square wave TIG machine = $1500. Home depot grade wood glue can acheive 80% parent material strength with much less skill then welding, and you don't have to heat treat glue joints for full parent properties. Anyone want to race me to install a new limit switch with 2 wood screws vs tapping holes? How about hand jigsawing 10 linear feet? With a rookie team (3rd in a row for me), 6 weeks, and no money, I got wood on the brain.

[MrForbes]

Originally Posted by travis

Price of a clamp = $5

Nice comparison!

although you can use a $1.50 clamp to hold an aluminum bracket on to an aluminum structural part too, if you design it right....no welding needed.

[John Gutmann]

Originally Posted by squirrel

Nice comparison!

although you can use a $1.50 clamp to hold an aluminum bracket on to an aluminum structural part too, if you design it right....no welding needed.

Well then you can use a 1 cent woodscrew to hold the wood inplace! Beat that!

[MrForbes]

Originally Posted by sparksandtabs

Well then you can use a 1 cent woodscrew to hold the wood inplace! Beat that!

No need to beat that, I was just trying to make the point that you can build a robot with aluminum with only hand tools, if you really want to. There is no need for a TIG welder.

[Pavan Dave]

Aluminum is much easier to work with in my opinion and it is much lighter and comes in many more different shapes. Also in some tight situations, if you really need to, you can feed your wires through aluminum if you are using box aluminum. It is also a little more flexible from my experience.

The only downside is that on wood you get splinters and with aluminum you get huge slices on your fingers with sharp parts if you aren't that careful but overall aluminum wins by a landslide.

Pavan.

[Lil' Lavery]

Aluminum provides much greater flexibility in your design. Aluminum comes in many stock shapes and varieties, and can be used for just about anything (frame, axles, gears, rivets, bolts, sprockets, wheels, etc.). Aluminum can also be bent and re-shaped, while wood breaks. Aluminum also provides more options for mounting, such as welding and riveting.

[underwood]

aluminum



ever tried to make a wooden sprocket?

[ThomasP]

Originally Posted by underwood

aluminum



ever tried to make a wooden sprocket?

Well, I'm sure someone has, I was mostly referring to the robot frame and arm though.

[Gabe]

The only use I can think of for wood in robotics is to offer a noncunductive surface for mounting electronics.

For everything else, aluminum. (2024, 7075, and 7068 are hard to beat, as well as the alloy everyone loves, 6061)

[Kevin Sevcik]

Gabe, my welder hates you. Seriously, any of the aircraft grades are nigh impossible to weld well. Thus we use 6061 for the majority of our parts. We're actually looking at thin wall steel for next year to make the welding even easier.

At any rate, on topic, wood is just too fracture prone under shock loading for my taste. Aluminum will bend, but might be usable or salvageable after it yields. Wood doesn't yield, it breaks. That said, it can have its uses in structural parts of the robot. Contrary to the prevailing opinion here, I think wood is a rather lot easier to work with than aluminum, as it is amenable to all sorts of hand tools and, well, woodworking tools. The strength to weight ratio of wood is more or less comparable to aluminum as well. So understanding the main limitations of wood, there are still places on a robot where it might be preferable to other materials.