Alternative Materials

[AndyB]

I know of 2 teams in particular that use 4130 chromoly steel (269 and 1501). Its very very thin and still retains a lot of strength in comparison to 6061 aluminum.

It can be found here:

http://aircraftspruce.com/catalog/me...4130square.php

[ebarker]

A few years ago we used baltic birch. I think it was once used to build airplanes.

[IKE]

Aircraft-Spruce is an interesting site and a good place to check out neat materials.

[dtengineering]

Ever since we've started teaching the students to TIG weld, we've come to appreciate the beauty of thin walled aluminum tubing. It's hard to get much better than that for most structural applications when you can just stick it together with the TIG.

But that doesn't mean we don't have a passion for trying out "alternatives". Go to www.trobotics.ca and click on "robots" for a walk thought of some of our machines.

2004 - Plywood main chassis, fibreglass with urethane foam core on the top layer.

2005 - Arm 100% plywood, could support two judges jumping on it at the same time in a 3 point loading test (we brought a spare for the demo) and was lighter than most other arms. Main parts of the frame (sides and back) are urethane foam core fibreglass again. The materials helped us win Xerox Creativity in Portland.

2006 - Our first try with thin walled aluminum tubing, but note the use of plywood (baltic birch) for the turret and ball intake mechanism, as well as the nicely turned main drive wheel on the ball lift belt made of phillipine mahogany. Coroplast secured with velcro made for nice light side panels.

2007 - Wooden lift (using IGUS track in a rabbet) of baltic birch ply, tube gripper and mount of baltic birch.

2008 - Carbon fibre hockey stick ball lifters... the CF sticks replaced some plastic floor hockey sticks that didn't like hitting the field wall at full speed. The sticks were donated as they were from broken sticks sitting in the Portland Winterhawks' trash bin (we ran out of spare wooden and plastic sticks on practice day in Portland). The love affair with baltic birch ply continues with the main robot body. GM Industrial Design winner in Seattle.

In short, it is fun to use something other than aluminum, and -- when chosen for good engineering reasons -- can attract positive attention from the judges.

Jason

[qwertyuiop[]\]

for our ramps in 2007 we used thin sheet aluminum backed with foam.
recently we have been using gatorboard (corrugated plastic) in our robots for electronics boards

[EricH]

In 2007, 330 used corrugated plastic and thinwall aluminum tubing for their ramps. Their robot also featured a fiberglass arm. In previous years, they've experimented with fiberglass, thinwall, and nylon.

Also, there is that tubular plastic that any home improvement store carries: PVC. It's great for arms, rollers, and light-duty protection.

[Cyberphil]

Well this year, we started with aluminum arms. In Trenton, all 3 sets we made got completely destroyed. We needed an alternative, and we thought titanium. So we made titanium ones that worked 10 times better.

[dtengineering]

And, I meant to add, if you are looking for inspriation for what can be done with wood (above and beyond the Mosquito, that is) check out http://www.joeharmondesign.com/ for a wooden car.

Not just any car... a 300mph exotic... that almost fits the new "no metal" rule. Wooden springs, spokes, supension... wow!

Jason

[vivek16]

lexan/polycarbonate

You can get the stuff in this green house building stuff. It's ribbed and is incredibly light. 525 will attest to this, they used it on their arm last year. Crazy stuff.

-Vivek

[FourPenguins]

One of my favorite materials of all time for small parts is Acetal resin (Delrin). It is a good bushing/spacer material and some teams have even used it for gearbox plates.
Polycarbonate has reached the point of almost being mainstream, so I won't go into detail. However, keep in mind that it comes in tubing as well as sheets.
One of MORT's cooler innovations has been polyurethane foam. It's a two-part mixture (like an epoxy) that expands to fill whatever you pour it into. It's good for adding rigidity to tubes.
Also available is solid polyurethane, which can be used to cast parts. For example, if you have a small, low stress part, machine one out of aluminum, and then make a mold from it and cast the rest.
Aluminum is not nearly as one-dimensional as one may think. Different alloys have different properties and a little research will go a long way. Look into the 7075 and 7068 alloys for high strength options.

[R.C.]

Originally Posted by FourPenguins

Look into the 7075 and 7068 alloys for high strength options.

My favorite, better if it is donated.