Last Saturday we started working on the frame of the kart, using the steel that had arrived from McMaster a few days prior. We're using 1 inch square tubing with a thickness of .083" that comes in lengths of 6 feet.
6 foot lengths of steel, still in their shipping tube.
We had to go through a few different cutting experiments to find the best way to cut the steel at right angles. We started with a circular saw, then tried a hacksaw, and finally settled on a table saw. Unfortunately, the grinding blade we have is a bit too small for our table saw, so each cut required the steel to be turned twice (a total of 3 cuts). As a result, most of Saturday was spent cutting the steel.
On Sunday we started construction of the frame. We did most of our work in our garage, which was very hot (probably about 95 degrees). The first hour or so was spent trying to align the frame so that it had relatively right angles. We finally managed to get the frame clamped down into the correct position with large clamps and some dumbbells and we tack welded it into place. Below is a picture of the setup that held the frame together for the initial welds.
After the setup phase things went relatively smoothly. We spent most of the day welding the primary assembly pictured above, as well as the T structure at the front end of the kart. We also messed around with a wire brush drill bit, which helped us clean our welds so we could assess their strength. Below are some pictures of a weld before and after being cleaned with the brush (the after photo is a bit out of focus).
We're hoping to have the rest of the frame finished this week and to have a rolling frame some time next week.
All of the go kart seats that are sold online seem to be at least $40 plus shipping--clearly a ripoff. So, over the last couple of days, I have been keeping an eye out for junk that I would be able to use for a go kart seat. This included looking through the local dumps and recycling centers for discarded chairs. Today I finally went to Walmart and was surprised to find a perfectly suitable chair for about $7. The mounting bracket, which I did not purchase, was sold separately for about $20. As far as I can tell, the seat is meant to be mounted to the deck of a boat (I found it in the boating section).
It made sense to mount the seat to the kart so that it is removable. This way, the seat can be placed on the kart to provide its dimensions (avoiding design conflicts), but can be taken off while welding. I screwed the seat into a piece of plywood with the screws that came with the seat. The screws go directly into the plastic.
Next, I welded three tabs onto the frame of the kart. The tabs were actually recycled from the 45 degree angles cut to make two of the battery boxes. I just drilled a holes in them and welded them on.
The plywood was bolted to the frame.
The battery fits snuggly behind the seat.
After testing out the seat, I can't say I'm entirely pleased with the its rigidity. I will probably weld a forth tab to the frame at some point and might use a less flexible piece of wood for the "bracket." In reality, it probably doesn't matter how well the wood is attached to the frame, since the strength of the entire seat mount is limited by the strength of the junction between the screws and the plastic sockets.
