Tube Versus Channel

[George C]

We used 3 x 4 x 1/8 rectangular aluminum tube for side rails with wheels and chain runs mostly inside the tube. It wasn't easy to find but Metals Depot (metalsdepot.com) stock it and ship to Canada with no problem. By the time we finished with the tube there wasn't a whole lot left so it was light and very strong. Cross members were 1 x 2 x 1/8 rectangular tube with loads of lightening holes. The chassis is tig welded. 1 x 1 x .090 square tube was used for the superstructure. Here's a photo.

http://www.othsrobotics.ca/images/isabella.jpg

Rivnuts are great but do strip out easily if installed by the inexperienced. They also don't allow for two pieces to be tight together as there's a flange on the nut. Rivnut kits are available from Princess Auto for about $35 (http://www.princessauto.com/pal/prod...ting-Tool-Kit). That gives you the tool and then you can buy more rivets from McMaster Carr. Unfortunately the kit doesn't include 10-32. Making a 10-32 mandrel was straightforward once we bought a 10-32 LH die and much cheaper than buying a kit from McMaster Carr.