Re: Input On Steel chassis w/wood inset
 

Oh yeah, structural foam is the bomb. We also put wooden dowels inside tubes - the REALLY SMALL bit of added weight is nothing compared to the massively increased structural stability; I swear RaPHael (our robot last year) would have had its tube-based arm destroyed many times over if it wasn't for the wooden inserts!

And Henry, unless you know something I don't know (I won't discount it, I didn't go to the drive train meeting), we've always had our aluminum frames TIG welded by Randy Baden - remember "Randy the Welder"? :D

Also I want to give a shout-out to team 456, it's always a joy to see what you guys come up with every year - so far "Captain Hook" has been my favorite. Can't wait to see you again at Lone Star!

-Danny

Re: Input On Steel chassis w/wood inset
 

Hey Danny, a big shout-out back to 418! Unfortunately, we are going to miss you guys and everyone else at Lone Star this year. We let the team vote on what regional they would like to attend and we decided to try somewhere new this year just for fun. We are heading to DENVER! I have a feeling it may be a bit colder than Houston. We will miss everyone at Lone Star but are looking forward to meeting some new faces in Denver. Best of luck to you guys in Houston! Your bot ROCKED last year!

-Chuck

Re: Input On Steel chassis w/wood inset
 

I know it has been mentioned before, but I haven't seen much about teams using carbon fiber in frame construction. The way I see it, carbon fiber tubing from McMaster is reasonably priced, but has very thin walls, perfect for some filling with aforementioned structural foam. Combine it with some bullet resistant polycarb, maybe a little Kevlar or Ti, silver conductor wiring, and you'd have plenty of shock value... no money though. Seriously, that carbon fiber tubing looks great for arms, and if only I could find a good sorce of silver wiring I'd be pushing that through on my team at this very moment.

Re: Input On Steel chassis w/wood inset
 

the problem with carbon fiber on McMaster-Carr is that it is sold in very small amounts; the tubes are 1 ft long, and the sheets and plates are 2 ft or less. besides, where's the fun in using composites if you're not making monocoque, high temperature, vacuum bagged-parts?;)

Re: Input On Steel chassis w/wood inset
 

In 2004 Team 1114 used carbon fiber tubing for our gripper.

http://www.firstrobotics.uwaterloo.c...rms/arms83.jpg

It wasn't called for in our initial design, but after a couple iterations, we soon realized that weight was a huge issue for our team. We needed a lightweight gripper to ensure we fell within the weight limit, and to lower our center of gravity.

The carbon fiber tubing solved our weight problem, but we quickly realized that it wasn't going to be rugged enough to last for many matches. Knowing this, we designed the gripper so that individual portions of carbon tubing could be swapped out very quickly. This modular design allowed us to deal with the frequent breaks. (IIRC, a certain college team from somewhere in NY state snapped our gripper during a practice match... ;))

So, if you're going to use carbon fiber tubing, consider filling the tube with some sort of structural support, and be prepared with spares.
We ordered our tubing from Aerospace Composite Products. They have a variety of thickness, diameters and lengths when it comes to tubes. I believe we ordered the 60" sections. They shipped to us overnight (yes, across the border!), and were a pleasure to deal with.

Re: Input On Steel chassis w/wood inset
 

The price of true structure carbon fiber can be a budget buster. Mcmaster carries a selection of fiberglass pultrusions that are more budget friendly. Instead of thick wall material. Try tube in tube construction with 2lb expanding foam between the tubes. As this post was about wood and steel, I'll stress again that birch plywood is tough and can be reinforced with fiberglass. You find that the end result is a material that has better properties that polycarb and is lighter. Make sure the plywood is solid birch ply's and not a filler in the center.

Re: Input On Steel chassis w/wood inset
 

4130 steel is a great structural material. Alot of smaller planes have this chromoly frames. OOOh ya and planes have to be light right??

Welding aluminum frames is not very good. When you weld Aluminum the T6 hardness goes to T0 in the welded areas losing most of its strengh.

The bolt together extrusion is a very good way to go. easy to cut and bolt together Very Very strong.

The way my team(Rage 173) is has been going for the last 6 years is using 1/2 cabinet grade plywood. Really nice to work with. When its painted up it doesn't look like some structural monster.

I've been doing this for almost 11 years I've tried all these paths.
And the best 2 are the bolt together 80-20 extrusion and the plywood bases.
I would stay away from the welding its not necessary.
theres lots of manufactures of the extruded aluminum 80-20, bocsh profile, its pretty good. Its just grown up legos.

A first time team should either use the kit frame of go for the extrusion frame which is more stiff.

The plywood is nice but you have to know what your doing.

I have seen alot of welded frames in the competition do well but they really have to be over built to survive the punishment. They'll probably be someone that goes against my statement but the fact is the weld goes to Tzero!!! and the weld turns out to be the weakest spot. They might say they reage the welds by solution heat treat. but most likely not because the heat treat will warp and twist the frame.

The carbin fiber idea is all cool and fancy sounding but its really to brittle.

So if your a beginer go with the profile (extrusion) or if you have a really good carpenter take the leap and go with the 1/2 cabinet grade plywood.