With more time in the garage, I proceeded to finish the main combustor housing and flame tube for the new HR-1A engine. I had a few setbacks during the construction process, but I think that it important to show mistakes as well as triumphs. Only by making mistakes can we ever really learn. Let me tell you though, that I learned a lot this time around!

Flame tube

The new flame tube for the engine was laid out using hole patterns recommended by Jet Spec designer. The holes were then center punched and drilled to the appropriate sizes.

Squared flame tube

To make sure that the hot exhaust gasses could flow freely from the flame tube and make a swift exit from the combustor, the ends of the flame tube were squared up. This was accomplished using a vise, and anvil, and a hammer. Sometimes beating metal into submission is the best way to deal with it, and it surely helps to burn off the days frustration as well. The squared end will now be able to fit into the funnel that leads to the turbine, and the gasses will make the transition smoothly.

Flame tube in exit funnel

The flame tube is now a perfect fit into the exit funnel, and the engine can be assembled further. It is little things like taking the time to provide smooth transitions for the hot gasses that will allow these engines to produce the most power.

Flame tube in combustor

With the flame tube and combustor housing almost complete, the parts were assembled for a test fit. Everything seemed to be in order, so the next part of the project was undertaken. There must be an air inlet to the combustor housing that will provide the air from the compressor to the flame tube. I could have used a round tubing section, but to try to further slow the gasses down I decided to use a tapered pipe instead.

Inlet diffuser

To slow the air down before it enters the combustor, I made the inlet to act as a diffuser. Why this is necessary, is because the air will compress further as it is allowed to slow down. The slight taper in the diffuser will accomplish this for the engine. To fabricate the diffuser I started with a piece of round tubing and cut it down the middle lengthwise. I then cut two triangular pieces to fill the gaps between the tubing halves. The triangular pieces have a 3 degree taper that will give a gradual widening of the tube. The entire assembly was then welded together and the flap disc was used to finish the outside to a nice look. If the diffuser works as planned, the P2 pressure should have an increase that is noticeable, and will produce more thrust output from the engine.

Diffuser test fit

The diffuser was test fit to the engine by checking how it would fit going from the outlet of the compressor to the far end of the combustion chamber. The length was acceptable to start welding it into place.

Marking the combustor inlet

With the diffuser in place, the outer combustor housing was marked for the hole that needed to be cut. The diffuser would then be shaped to fit against this hole and finally welded into place.

Warped combustor housing

With the hole in the outside combustor housing cut, stainless wire was loaded into the Mig welder and the diffuser was tack welded into place. As this combustor was my first attempt to weld stainless, I took my time and made sure that everything was lined up and fitting properly. Once everything was tacked and seemed to be fitting good, I made the final weld passes. This is where the real trouble began. The stainless warped badly while welding and I could no longer get the parts to line up as they should. I made cuts in the inlet and tried to realign the parts, but nothing I did seemed to help. The heat had twisted the body of the outer combustor shell and there was nothing that could be done to save it.

My very expensive and nice looking combustor was in ruin. I decided to have another combustor housing rolled for me, but the new one would be regular steel instead of stainless. I am not happy about the stainless housing being destroyed, but this is a learning process. While I could have went about my way with the new mild steel combustor housing and only shown the parts that turned out right, it would not do justice to the amount of time and effort that goes into the creation of one of these engines. Sometimes it is easier to appreciate the final product when you know what goes into making it.

In the big picture, I am sure that major engine manufacturers spend far more time and money getting this right. I will still call the new engine the HR-1A, as I really don't see much of a need to make a change in name based on this one incident. Lets just hope that the omelet gets done before I break too many more eggs!

Attempt to fix stainless combustor

This picture is just to give you an idea of some of the things I tried to get the stainless combustor working again. You can see where I had cut the end of the diffuser pipe and adjusted the angle to try to make things line up again. With the warping in the outer combustor shell, the new angles in the pie and all the other problems, it was better off to be scrapped.

I have a new combustor housing being rolled and plan on being back in the shop for more construction very soon so be sure to check back with us. We are always interested to hear from those that enjoy viewing our projects, and welcome parties interested in sponsoring our builds to contact us. If you manufacture pumps, fittings, tires, or anything else you think we could use please drop us a line and see how a sponsorship program can be beneficial to both of us. Until next time,

Gary Richards

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