LVL1 has a new rocketeering group. This rocket engine testing platform is the first project to come out of the fledgling club. The purpose of the tool is to gather empirical data from model rocket engines. Having reliable numbers on thrust over time will allow the team to get their designs right before the physical build even starts.
The rig uses a pine base, with a PVC frame, threaded bolts, and a PVC cuff for mounting the engine in place. It is set to fire up in the air, directing the thrust down onto a scale. The flex sensor in the scale is monitored by an Arduino, and should be able to hold up to the 5000
pounds grams of thrust max which this type of engines can put out. The data is pushed via USB to a laptop computer where it is stored in a spreadsheet.
Calibration would be an issue here. But as long as they’re always using the same strain sensor the numbers will be accurate enough relative to each other.
[David Steeman] sent us this project. He uses a consumer scale to measure rocket engine thrust. He wanted to be able to map the thrust curve of his homemade rocket motors to determine whether they are meeting the design goals. It does this by measuring the force applied by the rocket engine via a microcontroller that records it in a text file on a computer. He then analyzes this data in an Excel spreadsheet.
The sensors were harvested from a consumer scale while the rest of the electronics were built by hand. He’s using a PIC 18F2550 microcontroller which has a built in USB interface. He has breakdowns of each piece with detailed information on how it works as well as some nice pictures. There is also a list of future improvements that he would like to do such as increasing sample speed, integrating it with the ignition, and decreasing the physical size. Files for the schematic, firmware, and excel spreadsheet are available for download at the bottom of the page, so keep scrolling down.