Thursday, July 17, 2008

Designing a balloon basket

I've been spending a fair bit of time trying to design a new basket for my balloon.

Originally, I wanted to make a rounded bottom on the basket. Basically, a 6" quarter circle arc on the bottom. That led to so many complications, I gave up on it.

The next question is how to frame the basket. Baskets can be susceptible to 'sag'. Unless something in the basket design works against shearing stress, this can be a problem.

My Balloon Works basket has six vertical wooden rods about 1.25" in diameter. This has worked OK, but it there are no cross pieces to really prevent shearing. Head Balloons appears to use an aluminum top bar, with some extensions that go down.

I'm thinking of the design below. It uses a 2" wide ash board, 13/16" thick. The vertical pieces would be woven into the wicker, but not the cross beams. The cross beams would be on the inside.

The frame should be about 30.2 pounds. If I use boards 1.5" wide instead, it takes the weight down to 22.6 pounds. I used Google Sketchup and this table for wood weights. The basket will be a lot heavier than a going with a composite basket. I need to do a final calculation and see if it will be close to my current Balloon Works.

For the wicker, I'm figuring 3/8" nylon rod every 2". I note that Head uses two 1/4" nylon rods.

I'm not sure about the load cables yet. Wire cables would conduct electricity. Rope might give way in a fire. Nylon webbing definitely would. I'd like the cables connected somehow so if one side fails, the opposite side doesn't go with it.

I also have to plan out how to mount the burners. I'm thinking semi-rigid with a commercial burner that uses a liquid pilot light.

The jury's still out to lunch on what I'll do, but I hope to start Monday.