Fun with ballistics

I’m writing some software to control the welly wanger, and am having to do some nasty ballistic calculations.
I’ve got some code that implements some of the equations, but not everything is straightforward. I need to determine a pair of variables (rpm and launch angle) from the desired distance – the competition is not just about throwing it as far as you can, but hitting targets, so being able to calculate desired parameters is vital. Of course, solving this way will not result in a single pair, but in multiple value pairs, so my initial guess is to fix the RPM as close as possible to the maximum, so we don’t have to control the motor directly, and just alter the release angle.
We do intend to have some form of PWM control of the motor driving the rotor, but I’m not sure how well the starter motor will react to rapid switching from the microcontroller.

The other issue that I have is solving for release angle, as the release angle determines the release height, as well as the trajectory, which confuses the issue somewhat, and is making my head hurt somewhat. I’m going to have to consult a proper mathematician to help me with the algebra.

Scrapheap challenge roadshow again

I had a phone call from RDF media last week, informing me that our team for the second scrapheap challenge roadshow had been accepted, and that we could start building our welly wanger.


This is a different team that entered the Sofa Speedway, and I’m the team captain this time, together with Andy Shaw and Ian Izett, we are building a computer controlled welly chucker, that will have an on-board microcontroller, witha USB interface to a laptop that will perform all the complex calculations that are required to be able to control the distance that the welly will be thrown.

It’s all taking place at The Great Dorset Steam Fair on the 30th August, so we’ve got to get busy with the building and programming, so that we can have enough time to train the artificial intelligence in the control software to the physical aspects of the machine.