Wood Chassis vs. Kit Frame

[lynca]

Originally Posted by GUI

There are really two questions being debated here (one a little more so than the other), "Why use a custom chassis?" and "Why make your custom chassis out of wood?". We use a custom chassis because we can make our robot exactly how we want it, and it makes mounting everything easier for us. We use wood because it is light, inexpensive, readily available, and easy to use with the tools we have. We can also make as many mounting holes as we need in wood on the spot, or simply screw something on. A custom chassis, or a wood one at that, might not be best for your team, but with our resources and skills it is.

I think for Rookies the question should be "Why make a custom Chassis ?"

After mentoring a couple rookies, teams usually don't have great CAD abilities or prototyping experience.

Most rookies should stick with the Kit Frame and get a drivetrain working as soon as possible. If you can't do basic driving in this game you are going to really hurt your alliance score.

[huskyrobotics]

We are using Bamboo plywood for our frame this year. Our school has moved to a new location and we building a "green" campus. In the spirit our green movement we built a robot out of Bamboo poles last year. They were very difficult to work with but we pulled it off. We find the 3/4" and 1/2" Bamboo plywood to be a remarkably beautiful wood that we can easily manipulate. However, it is expensive. I guess being "green" has its price.

[Dick Linn]

Wow. Years ago, only Pine was allowed, and only in certain thicknesses. Plywood might have been 1/2" limit, I don't recall. But solid pine could only be a max of a nominal 1 x 4, so if you wanted bigger, you had to laminate it yourself. None of that designer stuff like Baltic Birch or bamboo or Bocote. We glued up our drive wheels from 1 x 4's (large aluminum sections were forbidden).

In our first year, we used wood because it was easier to saw in a wood shop, easier to glue and a whole lot cheaper than aluminum. And you could burn last year's 'bot in a wood stove to heat the shop for this year' build.

[sdcantrell56]

well it's official...1771 will be going with an all new okoume plywood, laser cut wood frame. We are definitely looking forward to the weight savings.

[gorrilla]

Originally Posted by sdcantrell56

well it's official...1771 will be going with an all new okoume plywood, laser cut wood frame. We are definitely looking forward to the weight savings.

laser cutter?

no fair, but we just got an awsome new bandsaw to play with


wait, Laser+wood=fire?

[s_forbes]

Originally Posted by sdcantrell56

well it's official...1771 will be going with an all new okoume plywood, laser cut wood frame. We are definitely looking forward to the weight savings.

ooooh.... can't wait to see that!

[sdcantrell56]

Yeah a laser chars the edges a tiny bit but being able to cut out enough pieces for 2 drivetrains in about 20 minutes is well worth it. I am so excited. Finally we get to play with wood.

O and for anyone that cares. Our new frame complete will weigh 15lbs, a comparable aluminum one would have been ~25 and still would not have been as stiff. Now we just have to figure out how we want to finish it...hmmmm...

[GUI]

Today we finished assembling the prototype (and possibly final) frame for our bot, weighs 16 lbs and is very strong and stiff. http://www.chiefdelphi.com/forums/sh...943#post799943

[dtengineering]

Why build out of wood?

Ask the makers of "Splinter", the all wood super car.

http://www.joeharmondesign.com/

I believe the answer is "because you CAN".

Jason

BTW, Lookin' good 1726!

[MrForbes]

The photo of 1501's dent (and Chris's description of the damage to their robot from the same collision) got me to thinking...and I found this thread, and am offering a status report. Our robot Major Tom has a wood chassis, turret and shooter assembly, and electronics box. We attended two regionals, first Los Angeles where we qualified 4th and lost in the semifinals, then Phoenix where we qualified first and won (with 39 and 1165). There is some slight damage to the robot on the front, above the ball intake, a 2" long crack is visible on the back of the plywood. This area is subject to those tough solid head on collisions in autonomous mode, and has taken a beating. Other than that, the robot has held up just fine, with no apparent problems with any of the wood parts.

We shipped the robot to Atlanta, and hope to see many of you there....you are invited to stop by and take a look and say Hi

[big1boom]

I prefer an angle aluminum robot,

1) It looks cool
2) Its stronger than wood
3) Its fully customizable
4) Its easy to machine, (our entire robot frame was made with a miter saw and a drill)
5) Its more forgiving
6) Its relatively lightweight (the entire robot weighed in at 117, and that is with a lot of #35 chain.

After two regionals, the robot has no dents, scrapes, or any problems from collisions.



People that are able to pull off a wood chassis that is strong enough have my applause.

I would recommend that teams try and design a custom chassis, then build it out of angle aluminum if they do not have much machining capability.

[EricH]

Originally Posted by big1boom

I prefer an angle aluminum robot,

1) It looks cool
2) Its stronger than wood
3) Its fully customizable
4) Its easy to machine, (our entire robot frame was made with a miter saw and a drill)
5) Its more forgiving
6) Its relatively lightweight (the entire robot weighed in at 117, and that is with a lot of #35 chain.

I'm going to have to call you on some of those.

2) You'll have to define the strength. Tensile, compression, shear, torsion, or bending? Elastic or not? How is it supported?
3) So is wood. You may need gussets, but it is fully customizable, and said gussets add some strength.
4) Guess what else can be made with only a miter saw and a drill? Yep, a wood frame. I might even say it's easier to machine, as it's softer.
5) Really? Wood is pretty darn forgiving. It's also cheaper, so if you do make a mistake, and you can't fix it on that piece, you can get another piece much more cheaply (and easily) than metal. Home Depot and Lowe's don't exactly carry much structural aluminum--but you can sure get some pine or fir!
6) Depends on your wood. Balsa or spruce is pretty light, for example. (Though I can break thin sheet balsa barehanded, but that isn't saying much.)

[big1boom]

I guess that I prefer aluminum because of my lack of knowledge about wood, sorry.

I know that if wood is done correctly, it can be strong, and lightweight.

[sdcantrell56]

As someone who has now designed and built 2 wooden drivetrains, I will have to refute almost all of your claims.

A wooden chassis is without a doubt lighter than a similarly strong aluminum chassis. The plywood we used had a density of .016lb/in^3 and baltic birch has a density of .023lb/in^3 in comparison aluminum has a density of .098lb/in.^3. This alone means that our chassis can have 7 times the material of an aluminum chassis for the same weight. Our chassis did not have 7 times the material but it did have significantly more which made the frame much stiffer than a comparable aluminum frame. Also the way it was constructed, with no screws and all tongue and groove joints, completely joined with epoxy creates a much more rigid structure. The one property that wood suffers in is the resistance of dents, aluminum being much denser will be able to take more direct hits without gouging. However in a game with required bumpers this is a non factor. Just as an example, our complete drivetrain this year with 6 wheels, 4 chains, and 2 cims plus transmissions only weighs ~33lbs.

Wood is much easier to machine, it is softer and easier to cut and drill, it is also readily available and much cheaper than aluminum (with the exception of exotic woods).

You can customize a frame out of any material you want. All that customizing requires is a design to suit your goals. Our frame this year was completely designed in CAD and then laser cut and epoxied.

Another nice property of wood is that it does have some inherent "give" in it. When wood is impacted it will flex slightly and return to its original shape. Aluminum does not share this trait. Also aluminum has a very finite life cycle, after being bent enough aluminum will snap. Wood has a nearly infinite life cycle.

As far as being cool looking, I will let these pictures dispute that claim.

Needless to say I along with the students on our team have fully embraced wood and really do not see any reason not to use wood in the future.

http://picasaweb.google.com/lh/photo...eat=directlink

http://picasaweb.google.com/lh/photo...eat=directlink

http://picasaweb.google.com/lh/photo...eat=directlink

[Jetweb]

This year we went half way to wood, there is an aluminum angle/1x1 box tube exo-skeleton, but everything is mounted to the wood base (painted green green in the picture) including our crab modules. So far it has worked out great.