I'm back again, and this time I have some interesting results for the HR-1A engine. I did more testing and the engine literally came apart at the seams! You would think this is a bad thing, but I'm pretty happy about it actually. The thrust was more than I expected, and other efficiencies were good as well. This engine is really putting a smile on my face!

Nozzle on engine for thrust testing

The first thing I wanted to do was reinstall the thrust nozzle on the engine so that I would have a better chance of seeing some usable thrust in the testing. Using a few small tack welds, I attached the nozzle to the jet pipe on the back of the engine.

Business end of the nozzle

The nozzle is not that much smaller than the jet pipe itself, but it should make more thrust for the engine by accelerating the gasses to an even higher velocity as they leave the pipe. I wasn't really prepared for the results when I fired up the engine again, and I assure you that this nozzle makes a big difference!

The outside of the combustor casing

Firstly, this is the outside of the combustor casing. The paint bubbled up a bit during testing, on this spot right here. It's pretty obvious that my weld did not penetrate as good as I had originally thought. The hot gasses from the combustor were seeping right through the bad weld and getting under the paint causing it to bubble. As the engine was shut off, the paint and combustor cooled and the paint settled back down to look like this. Hmmm, I didn't notice this after the first test runs I showed in the video?!?

Weld split on the combustor

Whoa! I certainly didn't expect this! While running the engine, everything seemed fine and pressure was good with a very good thrust output. All of a sudden I heard a loud hissing noise. After checking the combustor I found the culprit. It was this area in the photo above which actually measured out to be a little over an inch long and about 1/32nd of an inch wide. It is one of the welds of the combustor that had split open! It isn't a big problem and will be an easy fix. This happened at 35 PSI of pressure on my combustor boost gauge. The engine never slowed down, didn't heat up, and only lost about 5 pounds of thrust when this happened.

Flame tube after the test runs

After the test runs, I disassembled the combustor to check for wear and heat marks. As you can see on the picture of the flame tube above, the burn is happening right in the primary to secondary zone.

Other side of the flame tube

Flipping the flame tube over shows that we have the same pattern all the way around. Whoo hoo! This is good news for the engine! Low exhaust temperatures, plenty of boost, the nozzle on the jet pipe was whizzing away making a high pitched squeal that tells me it was choking the flow just right, and to top it all off it was burning 10 gallons per hour as figured by the nozzle size, fuel pressure, and consumption from the tank! This engine is a winner for sure. But what about thrust you ask? Well read on!

The scale after testing

This is my trusty scale I use for thrust testing. It has never let me down, and I check the calibration regularly to make sure it is still going to give good results. As you can see, it wouldn't give very good results now! The needle is buried at 42.5 pounds, but that is after it came all the way around and back down after the run! Here is what happened. The engine pulled the needle all the way to 50 lbs of thrust, and the scale kept up. The engine then took it on past 50 lbs on the scale and stopped reading at 5 lbs (technically at 55 lbs and holding). What is surprising is that the engine pulled so hard that it stripped the mechanism inside, since it went over the 55 lbs of thrust! You see, the scale needle is limited to 55 lbs total, but the mechanics just kept going round and the gears popped over each other. This is why the scale would return to a lower point than 0 when removing all tension from it!. If you take that the scale must have gone over 55 lbs, then you can calculate how far by seeing how far it went backwards when returning to zero. It must have gone over by at least 7.5 pounds! I hope this is making sense so far to you. Just add the 7.5 lbs to the 55 lbs we know we produced, and you will get 62.5 pounds of thrust! Not bad for an engine of this size, especially on only 10 gallons of fuel per hour!

So now the combustor is being patched, a new scale is on order, and I am getting everything ready for even more testing. I already know for sure that the engine is much better than it was before, and here are the number to prove it!

As you can see, the difference is like night and day. As soon as I get more results, I will post them here along with more video if I get some.

Check back soon for the newest testing results. As you leave the site, please remember to support us as the builds are partially funded by your contributions. Thanks again for stopping by!

Gary Richards

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