Kraken

[PyroJoe]

Started construction on the Kraken. Two (ported) 6.75"dia. CCs pushing a 4.25"dia main tailpipe. The intakes are 3"dia. Total length 67.5"

Tail cone in progress, not shown in the photos. Looks like a fun one.

[Kool]

well, that looks impressive
Why do you put two straight tubes behind the inlet?

For an even more compact engine you would combine the combustion chambers, like Mike's triple-piper!

What is the thrust you expected?

I'll certainly gonna follow your building process

[hinote]

Started construction on the Kraken. Two (ported) 6.75"dia. CCs pusing a 4.25"dia main tailpipe.

Looks like a fun and challenging project. Good luck with it!

Maybe I can pass along some tips and save you some grief, with the following:

1. You really need to flare the intakes and both ends of the intake augmenters.

2. The intake augmenters will resonate on their own--and must be a multiple of the intake resonant frequency. Sizing by physical length is useless because of the difference in gas temps. Your best bet is to make sure the engine is running properly without the intake augmenters, and then add them later. They can interfere with the core engine's running enough to keep it from self-sustaining. OTOH if you add them to a good-running engine and tune them properly they will give you a notable increase in power when properly tuned.

Hope this helps.

Bill

[PyroJoe]

Hi poech,

Why do you put two straight tubes behind the inlet?

This was borrowed from recuperator of the Escopette, Since there is no need to bend the pipe with this engine, it is straight.
The way I see it, it stacks more air in front of the intake and creates a higher/longer pressure peak within the CC, also a lower peak on the low pressure cycle. That's the the theory I have for now. It can be shorter in length, but I started with that length so it can be trimmed.

"For an even more compact engine you would combine the combustion chambers, like Mike's triple-piper!"

It is better In my opinion to keep the CCs mostly seperated. This is something I picked up approx. a year ago from the school of Cronje. Basically what I took from the idea is not to let the flame front expand into a large diameter/volume. If possible, it is better for the flame front to travel within smaller diameters. This is also the basis for creating half the CC volume as a cone. I think this becomes more important as the size of the engine increases.



Hi and thanks Bill,

It will get flares. Still have some experimenting to do with this one, the fueling system will need the intake flares to work in a particular way, drawing the highest quantity of fuel. Will attempt a non-pressurized fuel system after startup, have my doubts, but need to try.

These aren't exactly augmenters, but more to the dimensions of Escopette recuperator, will flare the intakes of the recuperator slightly, the tail end will remain sharp. I've noticed on the midway engines they nearly double the thrust, running like a quasi-valved engine.

Have had very few problems with sizing, this one may prove me wrong, but am reasonably confident after seeing the 4.5"dia. CC engine run well. One problem that is difficult to compensate for is dual CCs and intakes, adding a slight bit more resistance to flow, and require a slightly longer unexpanded tail length.

Joe

[PyroJoe]

My apologies Bill,
Of course you know about the recuperator stuff, I just remembered you had four of them on the Kentfield.
Looks like the tails of those were left sharp also.
Joe

As a side note/fun fact, a valved version would look about like what is in the picture, with the exception that a valve head would replace the intakes. The CCs are nearly a match to a scaled up Atom Jet, with just a slight more length in the CC cylinder.

[PyroJoe]

Constructed and welded the tail. Adorned with some paint to prevent rust, it may take some time to build a stand and fueling system.
A few more inches and she would be about my height. ha

[WebPilot]

 
 Perhaps you should look into fabricating medieval (or mediæval) armour as a home business?

 From one Kraken lover to another



 BTW, nice work.

[PyroJoe]

Thanks Forrest,
Working on propane injection (temporary) just to see if she starts OK. Will test this weekend from a fresh tank. It may require two tanks with this monster.

[PyroJoe]

After hauling the propane tanks out of the shop I started looking for a method to secure the engine. Quickly became apparent that a robust stand was needed.

Test Stand construction underway.

[PyroJoe]

It Runs! (Happy dance, happy dance),
Constructed it with a slightly longer intake than the smaller midway engines, (about 10% longer). It was sputtering and going rich easily, so started trimming the intake and adjusting the 3-point injectors with each trim. It finally locked in after removing the extra 10%. The stand performed well keeping everything where it should.

Spent a reasonable amount of time prior to the runs adjusting the flow of the injectors, assuring they matched closely. Added a equallizer line between the two fuel lines to insure the pressure was nearly equal. This clearly paid off as there was no imbalance in the chambers, sounded as if there was only one chamber. At no time did one overpower the other. They both locked in, and came out of lock in at the same moment. Complete lock-step.

Wasn't able to push it hard as both tanks were cold after fiddling with the intakes over the course of the afternoon. What little I did push, she climbed to a beautiful roar.

The low end was still very much present, at low throttle was able to remove the ear muffs (without pain) and walk around it, even with the two 6.75"dia. CCs firing away!

The local radio 101.3F.M. inadvertently provided a theme song by playing "Sound of Madness" by Shinedown throughout the days of this build.

Will be working on adding a thrust scale to the stand, and start on a liquid fuel setup, will post what I have sketched up if anyone is interested. See what I can do about putting together some video next weekend, my camera tech was away shooting prom pics this weekend.


It has been good to see the success of Anders and metiz, each finding a recipe that fits their needs.

[metiz]

Yes! well done
Keeping with tradition: we want a video and we want it now!

[Johansson]

Great work!

I second on Metiz comment about the video.

[PyroJoe]

Ha, as soon as the rain stops will get a video.

[PyroJoe]

Dragged it out and made a quick run last night,
tanks are less than half full, and must have bumped an injector as, the CC on the left appears hotter than the right. At this stage there is almost no flare on the intakes. Had to keep the vids short, the original vid was 75Meg!

Barely at an idle with both tanks opened up, only had enough pressure to bring it up to red heat before the tanks frosted. Time to move on to liquids and shake the "cold propane tank blues"

Ha, that paint held up fairly well

[metiz]

That's a nice roar you've got there, good work!

Time to move on to liquids and shake the "cold propane tank blues"

Don't forget to meticulously document your methods *cough*