Twin-Stack 32-incher: 'Lady Jane Grey'

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larry cottrill
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Mounting Points, Intakes

Post by larry cottrill » Tue Mar 06, 2007 4:21 pm

Vern -

I think either mounting arrangement you show would work. What Eric pointed out is true, and would seem to argue against your second drawing; practically speaking, though, the expansion of the middle cone will be very small, and will be mitigated by the "heat sink" nature of the mount spades, which will tend to cool the cone by conduction and re-radiation (or conduction into the supporting device). Shown here is the "vise grab" rails I provided on the Lady Guinevere (they are parallel, NOT diverging aftward with the cone!!!). Your first drawing is a better plan, though, since it is longer for greater stability and provides a "sliding fit" at the rear end.

Theoretically, the no. 1 best place for a rigid thrust-bearing mount would be at the outer edge of the front dome. A close second is the center point of the dome, using the spark plug as the mounting bolt (the Steve Bukowsky mount). Of course, either way, you still need to provide lateral stability at the rear (the keeperfrumfloppen mount ;-).
For the intakes I am going to use 90 ells cut to fit as opposed to the angled units and keep the C/L length the same ...
That will work, IF you cut them really short. If you let too much of the transverse part of the ell remain, the direction of the intake air will be too much "inward" and not enough "forward" - you want to make sure the explosion center is developed as close up against the front dome as possible. If it's aft of that, the lengths of the design will be wrong in terms of the actual acoustic behaviour, i.e. the pressure antinode will not be at the dome end of the pipe.

Don't try to get the centerline length "around the bend" of the ell. You would need to do that if the ell had a long leg going into the chamber, but not if it is tightly trimmed as just suggested. Instead, get the design length from the rearmost inside edge of the cut face of the ell back to the flare edge, treating it as a straight pipe. That's how I lay out the dimensions on all my recent drawings (illustrated also in many different intake geometries on the "FWE Evolution" drawing published a few weeks ago).

Knowing what to do with that "transition" can be tricky, especially if you don't want to custom build it. Just keep in mind that in the FWE design you ideally want the fuel/air mix to enter, flow forward and come to rest with a slow splash against the front dome, just as it explodes. Getting that detail right was the total problem we had with our attempts at a "front loading" intake. I think my own best designs for the intake pipe were on the Smooth Lady and Sveldt Lady variations - both quasi-transitionless designs (almost like Thermojet intakes), with the "transition" reduced to a little turned down lip at the top front of the intake pipe.

L Cottrill
Attachments
Guinevere_engine_mounts_crop1_small.jpg
Lady Guinevere(TM) closeup of tubular steel "mounts" - simply rails to be grabbed in vise. These are set parallel - they do NOT diverge with the cone. Photo Copyright 2006 Larry Cottrill
Guinevere_engine_mounts_crop1_small.jpg (134.71 KiB) Viewed 5530 times

Vermin
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Post by Vermin » Wed Mar 07, 2007 11:02 am

Hi Guys
Thanks for the info so far, I believe I am going to utilize Eric's design for the mount as it is removable and will be for testing only.

Larry I was thinking if using a radius bend for a smoother directional transition of the flow in the intake as we know abrupt angular changes in direction create unwanted turbulance in flowstrems. My intent was not to reinvent the wheel as such and I was going try to maintain the original angles and placement...you guys know way more about this stuff than I do.

The r bends that are commonly available will not be able to be utilized due to their length .....unless I can find a way to produce the radius that is required (not at this time) it will take away from the fun part.

I would apriciate comments on the attached diag as an atttempt to smooth the flow as much as possible, this should be relativly easy to fabricate with the dia of the intake structure.

I am just throwing ideas out seeking direction, probably a lot of my thoughts have been tried before but who knows, concepts and mistakes can change many things.

I have not been able to work in the shop lately it has been -23C just to cold to try to warm the place up so...... next week back at it.

Thanks for all the assistance.
Attachments
LJG Intake.gif
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Vern
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Mounting Points, Intakes

Post by Mike Everman » Wed Mar 07, 2007 3:05 pm

I like it. Can't hurt, but it is a finer point to be sure. There's been a lot of success with simple mitre joints. I doubt you'd see a difference in performance one way or the other, but it looks nicer.
Mike
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Vermin
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Post by Vermin » Wed Mar 14, 2007 9:15 am

Hey Folks
I am about ready to cplt the LJG this week and can't wait to spark it up (and I know it will).

I was just thinking about slight intake changes for experimantal purposes and would like to just tack weld the intakes (heavy) on @ 3 or 4 points and seal the joint with a compound like stove cement or clay for the testing phaze, has anyone tried this? advise.

I have attached some diag of changes to test, comments please if these configs have been tried sucsesfully or otherwise on various units. (the inspiration was the LH), dimentions are just general to start.

I think I will make all exp intakes as linier pipes as in the file called intake for ease of manufacture. How much differance would this (if any) make?
Vern
Attachments
Intake.pdf
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Intake1.pdf
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Tapered Intakes

Post by larry cottrill » Wed Mar 14, 2007 12:28 pm

Vern -

Those slightly tapered designs will work, I'm sure. The effect of such a taper is that it creates a little "back pressure" in the outflow situation (in effect, a higher impedance pipe) and increases exit velocity, while in the inflow mode it will act as a diffuser, reducing the speed of influx into the chamber. These are not unworthy accomplishments - but probably unnecessary refinements for intakes in the locations specified. There is a tradeoff to any nozzle: you reduce massflow but increase flow velocity.

The other thing to consider is what happens to pressure pulses. Any nozzle will create a reflection of some kind back toward the source of the pulse. In the case of a long nozzle, the pulse relfection will be stretched way out over time and will be of small magnitude. In this case, the reflected energy will be small anyway because there's so little reduction in area between the entrance and exit.

This says nothing about the flares you show, which I think are OK, but could be a little larger, even for a pipe this size. On an intake, I always think hammered flares are better than welded-on cones, but that's just a "gut feel" kind of judgment - a well-crafted welded flare will probably be better than a poorly wrought hammered one of the same inner and outer dimensions. I just like the smooth, rounded "toroidal" contour of the hammered flare, in terms of what we're expecting incoming air to want to do.

L Cottrill

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Post by Vermin » Sat Mar 17, 2007 5:20 pm

Just shop lights, cheap camera and lots of action....OMG this thing is AWESOME shook the HELL out of the shop and me.... 2 layers of ear protection IS required......OMG...no thrust numbers yet but it sparked up instantly once the injectors were stationd well.....more to come...... it is 2mm mild and oxidizing after 3 short runs......all I can say is........"LARRY...dam nice stuff"
V
Attachments
1.36m.MPG
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996k.MPG
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length.JPG
length.JPG (100.93 KiB) Viewed 5337 times
LJG pic.JPG
LJG pic.JPG (95.9 KiB) Viewed 5339 times
Vern
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Post by Mike Everman » Sat Mar 17, 2007 10:05 pm

Wonderful! Fat little beast!
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Queen Jane Approximately

Post by larry cottrill » Sat Mar 17, 2007 11:12 pm

Congratulations, Vern! I really get a kick out of designing one that generates happiness right away. Now, aren't you kicking yourself for not doing her in 1mm stainless? Ha ha ...

Don't run her so much you burn a hole through her hide. Before too many hours, get her shipped off to Mike for the 32-inch Chinese bake-off! No one now living knows when it will happen ...

Great work, sir! Glad you enjoy it!

L Cottrill

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Post by Vermin » Sun Mar 18, 2007 12:24 am

Forum PIA at times...anyway injectors as such....
Thx Larry
Attachments
flare.JPG
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crimp.JPG
crimp.JPG (118.18 KiB) Viewed 5290 times
expand.JPG
expand.JPG (103.92 KiB) Viewed 5291 times
Vern
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Post by Vermin » Sun Mar 18, 2007 12:25 am

As such......
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full thr.MPG
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Lady Jane Injectors, Thrust Guess

Post by larry cottrill » Sun Mar 18, 2007 1:29 pm

Nice work on the fuel pipes! The lemniscate pattern works well in this configuration (I assume you're using a somewhat 'deep' fuel spout location). What's your starting procedure like? What can you tell us about throttling through its range?

The cross-section areas here are 4x the Lady Anne values, and the volumes of the cones are better than 5x. You should be able to get 20 lb (about 10kg) static thrust out of her (probably more) with no tweaking at all. Would make a good engine for a lightweight bike or something; not quite enough for a go-kart. Are you somewhere near a big lake? A nice big model hydroplane or v-hull speedboat would be a wonder to watch, and an ideal project to show off a propane-powered jet, in my opinion.

L Cottrill

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Chunky Lady.

Post by James D » Sun Mar 18, 2007 2:32 pm

Good work Vern, that thing sounds nasty, I felt sure you'd have to add some length to the intakes but it seems to work great.

I can't get over how fat that thing is;) if it makes good thrust it could become a popular build.

James D

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Augmentation

Post by Vermin » Sun Mar 18, 2007 4:13 pm

Vermin wrote:By the looks of the power coming from the intakes this is an excellent candidate for the augmentor you have designed for her.
A couple of things to consider: First, as already mentioned, it will be MUCH harder to apply the shell to a completed engine! You're obviously a good metalsmith, so I guess you can figure out how to get the job done ;-) Secondly, remember that the real value of this shell is not as a "normal" augmentor for static / low-speed operation, but rather as a "passive" ramjet at speed. Its performance in static operation could prove to be quite disappointing, at least in terms of the effort required. Of course, if you don't try it, how will we ever know?

As far as I know, no one has ever built one of my shell designs onto their engine - so if you want to do it, I'd strongly suggest just "tacking" it in place until you're sure that the engine will still actually start and run!
I was thinking of a slight restrictor cone on the exhaust to shape the flow. maybe 3" and at 4 to 6 deg ...comments.
Sorry - to comment meaningfully, I'll need a more "graphic" explanation of what you're proposing. Remember that to keep the engine in tune, anything you add on has to be well separated from the exit plane. This is why the entrance to the augmentor/ramjet shell is set so far back from the intake flare, for example. Just let me know what you have in mind, in more detail.

One other question: In the videos, there seem to be two entirely different "characters" to the engine noise. Is this humanly observable through your hearing protection as well? Or does it just seem to be some kind of distortion (like the mic of your camcorder being "overwhelmed" by the noise level or some such)? The video makes it seem like the engine runs in two different "modes" or something.

L Cottrill
Vern
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RATS !!!

Post by larry cottrill » Mon Mar 19, 2007 1:18 pm

Vern -

Man, I'm sorry - what I did there was destroy your last post. I thought I had clicked on "Quote" when I really clicked on "Edit" (which shows up for me as a moderator, and works beautifully, unfortunately - NUTS!!!). I didn't realize my mistake until I hit Submit (lesson: ALWAYS use your "Preview" function to see what you've done before you hit "Submit").

My apologies - I certainly hope that's the first - and last - time I ever do that. I hope people can get a sense of what you were saying, since there was a lot more than just the couple of details I was "quoting". Feel free to reconstruct it in an "As I was saying ..." type post if you can.

Man, you deserve better treatment than that from me!

L Cottrill

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Post by Mike Everman » Mon Mar 19, 2007 3:46 pm

I did that once to Bill. If Vern has the original text, it would be nice if he re-posted.
Mike
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