Wood Chassis vs. Kit Frame
 

Several teams are posting and discussing wood frames for their robots.

With the frame kit included in the kit of parts, i am just curious as to what is driving you to a wood frame?

(PS - I am absolutely NOT being critical of the decision at all - I am just wondering.)

Re: Wood Chassis vs. Kit Frame
 

its cheaper for one thing

and easier to work with(sometimes)

Re: Wood Chassis vs. Kit Frame
 

You get the kit frame with your kit that you pay for, so why not use what you already paid for?

Re: Wood Chassis vs. Kit Frame
 

We are going with a wood chassis because we want a custom chassis for ease of mounting mechanisms, adaptable design (the kitbot design is not very conducive to harvester mechanisms in its standard form), strength, and modularity. We chose to us wood for the custom chassis because it is available locally (no shipping time, errors aren't as expensive), inexpensive, is great for structural applications (houses are a great example), easy to use, and very light (the baltic birch plywood we are using for our frame has a density of about .016 pounds per cubic inch). For our team, with limited funding and machinig abilities, wood is the best candidate for a lightweight custom chassis. And it builds much quicker than designs we've used in the past.

Re: Wood Chassis vs. Kit Frame
 

Our very first chassis (2004, prior to the introduction of the KoP frame) was made of 3/4" plywood, and... well... not particularly elegant.

Since then we've used the KoP frame each year, although never in the "out of the box" configuration. We've always chopped it, flipped it over, machined it out (slots for chain tensioning, etc.) and always, always, welded it up. You get extra stiffness and save the weight of all those bolts.

This year, though, we're thinking of going back to wood just because we've built just about everything we can out of wood (manipulators to motor mounts), except the chassis. Mind you, aluminum will still play a big part in our design, and we certainly could use the KoP frame if we wanted to, but this year we wanted to do something a bit different and show how much we've learned since that first plywood chassis.

Jason

Re: Wood Chassis vs. Kit Frame
 

I think we've made too many vEx robots :)

The kit chassis is universal, which means that it's not really "right" for any specific design. The parts are designed with primary emphasis on being able to bolt it together, rather than being strong in the directions it needs to be strong, not having extra material where it doesn't need it, etc. Many parts you want to attach to it need to be mounted with a bracket to adapt it.

With a custom designed chassis, the parts can be placed where they need to be, with strength where you want. The side rails can be made the right size to attach the transmissions and bumpers to directly. The electronics board or a mechanism anchoring part can be an integral structural part of the chassis.

It's sort of like the change in cars over the past 50 years to being unibody design, where the body and chassis are mostly one piece.

As for the choice of wood...it's relatively easy to work with if you have limited shop equipment, it's easier to find folks with woodworking tools than with metalworking tools. It's readily available, and it's inexpensive. Cutting and drilling wood takes less time because it's soft. It provides good stiffness for the weight, since it is not dense, you can use thicker pieces with the same weight as metal.

There are disadvantages, such as the low bearing load it can take, so attaching points might need to be reinforced. It will break relatively easily, instead of bending as metal would.

It's also quite a paradigm shift...we all know robots are fancy machined aluminum things, not piles of lumber!

Re: Wood Chassis vs. Kit Frame
 

I know of a certain team :rolleyes: that is using the kit frame with an intake, and so far there has been no structural issues with the frame after altering it for the intake system. Also, there are hundreds of holes to mount to on the kit frame.

Re: Wood Chassis vs. Kit Frame
 

My team has been lucky enough to have a metalworking company help modify metal and give us metal in any shape or form we may need. They have a full aluminum shop and every piece of equiptment for metalworking you can imagine. We use plywood to make a model of the design we want and they help us turn that into metal. We love these guys "Walsdorf Metal Works"

Re: Wood Chassis vs. Kit Frame
 

I agree with the many mounting holes being nice.

You're awesome shooter tower that scores 5 balls as second is somehow 3/4" out of the size box in the back? just scoot it forward a set of holes.

Not always as simple as that, but if you have a hole pattern on the frame, you should build around it and really take advantage of it (we like it so much, we made jigs to put .201 holes every 1/2" of any structural member).

Re: Wood Chassis vs. Kit Frame
 

i know that this year, the C-BASE chassis probobly wont work for us, without some modifications.... and the holes are nice and all, but they arent always what teams need(say you needed a "large" hole inbetween) which has happened to us a couple times....

Re: Wood Chassis vs. Kit Frame
 

You can make the kit frame work, for sure! That doesn't stop all those teams from milling frames out of thick sheet aluminum :)

One thing I've learned over the past few years is that there are many far more important aspects of robot design, than how the chassis is made. Chassis design is a great area for teams to do things how they want to....whether it's to save money by using a kit frame, show off their CNC design abilities, try out different materials or construction methods, or whatever.

Re: Wood Chassis vs. Kit Frame
 

I'm not sure what my team's final decision on chassis material this year will be, but last year we used a plywood chassis because... well, have you ever tried to make those nice straight pieces of kitbot frame be round?
The wood construction was lighter than an equivalent metal frame would have been, and didn't impair the bot's driving and performance.
We use the kit frame whenever we want a more conventionally shaped robot, though.

Here's a pic from last build season of a prototype bot with basically the same construction its better-decorated descendant who played at the Oregon regional.

http://www.team847.com/uploads/image...d/DSCN0052.JPG

Re: Wood Chassis vs. Kit Frame
 

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 obot 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.

Re: Wood Chassis vs. Kit Frame
 

Baltic Birch is awesome,

pictures from our with Baltic Birch Aim High 2006 machine

Re: Wood Chassis vs. Kit Frame
 

Team 173 (Rage) has used a somewhat "standard" (for them) design wood frame every year I've seen them play. Always a nice, robust chassis.

Re: Wood Chassis vs. Kit Frame
 

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.

Re: Wood Chassis vs. Kit Frame
 

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.

Re: Wood Chassis vs. Kit Frame
 

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. :D

Re: Wood Chassis vs. Kit Frame
 

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.

Re: Wood Chassis vs. Kit Frame
 

laser cutter?

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


wait, Laser+wood=fire?

Re: Wood Chassis vs. Kit Frame
 

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

Re: Wood Chassis vs. Kit Frame
 

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...

Re: Wood Chassis vs. Kit Frame
 

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

Re: Wood Chassis vs. Kit Frame
 

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!

Re: Wood Chassis vs. Kit Frame
 

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

Re: Wood Chassis vs. Kit Frame
 

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.

Re: Wood Chassis vs. Kit Frame
 

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.)

Re: Wood Chassis vs. Kit Frame
 

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.

Re: Wood Chassis vs. Kit Frame
 

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

Re: Wood Chassis vs. Kit Frame
 

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.

Re: Wood Chassis vs. Kit Frame
 

I think the use of wood this season has really helped us build a better robot. Not necessarily structurally better, but in the sense that we got more prototyping done and had enough time to go through several revisions before building the finished product.

In the past we would take a lot of time to go through a full drivetrain design and then build it over several days once our parts came in, but since plywood is so easy to work with and cheap (sorta) we were able to build a mockup chassis fairly quickly and put our prototype scoring mechanism on top. Playing with it a whole bunch revealed some issues that we couldn't have predicted beforehand, but construction time with wood was short enough that we were able to redesign and rebuild most of the robot.

Also, the old chassis made a neat display in the pits, and also served as a nice chair when people got tired of walking. Strong enough to support two judges. :)