Another thing a rocket scientist can't live without is a working engine tester! :-)
In order to make good dependable engines you must find consistency. To find consistency you need to know what kind of power your engines are producing. If you make a change in the fuel or any part of the engine design you need a way to test it so you will have some idea if that change was a good idea, or not.
Once again I woke up one morning and realized simple is better and less is more. I didn't want to spend a lot of money on an engine tester but I wanted something that worked. My solution was a steel bar with two springs a few pipes and a scale which I calibrated and marked according to another scale by pressing down on the engine holder at the top and marking the pounds on the white segment you see here.
At the top I have adapters that are used to fit the engines and by changing the adapter I can fit 1/2', 3/4" to 1" engines that I currently make. The tester goes all the way to 20 pounds and could be used on 1.5" to 2" engines I'm fairly sure. If the engine was so powerful it put out more than 20 lbs of thrust all you need to do is change to a more powerful spring set. The design is simple enough it would be very easy to build a tester for just about any engine size a hobbyist might want.
I drive or push the bottom of the steel shaft into the ground, put the engine in the top pointing down and light'er up. I use two cameras one focused on the scale and the other I wear on my head, it's a GoPro. Then I can watch the video and can see what my engines do.
The one thing I want to add to this is a analog to digital (USB) interface. I've found some IC chips that might work but I don't have any programming software for my PC to create a program that would read the sensor.
A simple potentiometer connected to the digital interface then being read by a computer program would be the way to go. If anyone has any idea where I can get something like that please E-mail me.