50 lbF 'Lady Astor' Not For Beginners

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larry cottrill
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50 lbF 'Lady Astor' Not For Beginners

Post by larry cottrill » Thu Apr 05, 2007 4:48 pm

Vern, James, James and Graham -

(Sounds kind of like a law firm, doesn't it?)

Well, here's the basic recipe for the promised 50 pounder (25 kgF) - but the 'Lady Nancy Astor' is really in the 'Advanced Course' of valveless pulsejet building. Named for the longtime friend of T. E. Shaw (Lawrence of Arabia) and ofttimes arch-nemesis of Sir Winston Churchill, this one will require a lot of metalworking skill to get the front end right, not to mention forming and fitting the "passive ramjet" augmentor shell. If this thing actually runs, I'm about 99 percent certain that you'll get your 50 pounds on propane even without the shell. If you can build it as shown, should be a nice piece for the mantel or to hand down to your grandchildren as a rememberance, even if it never does run. UFLOW1D says it should really roll out, though.

This one, Revision 01, uses the Messerscmitt style intake that everyone's been talking about lately. If somebody wants to give it more "conventional" FWE construction with rear-pointing intakes, it will take two with about 70mm ID or three with about 57mm ID, depending on how good you think you are at building fuel pipe manifolds. I can provide the design for these intakes later on if there's any interest. The Messerschmitt intake will require very careful centering and alignment to work really well - in fact, there's an element of luck to this whole revision since it's my first crack at a "linear FWE" pattern design. Bear in mind that this will not run if you omit the outer shell around the gap - to make a simple "linear" intake, the pipe would have to be the full 300 mm "path length" shown folded over on the drawing!

Assuming good construction standards, probably the only tweaking needed will be lengthening or shortening that outer shell over the intake gap by a few mm, so you might want to make that easily replaceable to begin with. I will try to provide large scale design views of the "sombrero" recuperator cap and the fore and aft engine mount details in a few days. I show the sombrero as a smooth curve, but I'll detail it as a stacked bunch of short cones so it can be built in the conventional hobby pulsejet manner. There really isn't anything dreadfully difficult about this - just a lot of pieces to mess with, and some need for extra care in building and aligning the "concentric" front end.

So, what do you think, gentlemen?

L Cottrill

PS: Lady Astor and Sir Winston were renowned for their verbal sparring. Two famous examples:

At a dinner party:
"Sir, you are drunk."
"Madam, you are ugly - but tomorrow, I shall be sober."


After a bitter legislative battle in the House of Lords:
"Sir, if you were my husband, I would poison your tea."
"Madam, if I were your husband, I would drink it!"
Attachments
FWE_Lady_Astor_appearance.GIF
Lady Nancy Astor FWE Valveless Pulsejet - size and appearance. Drawing Copyright 2007 Larry Cottrill
FWE_Lady_Astor_appearance.GIF (7.23 KiB) Viewed 12058 times
FWE_Lady_Astor_Rev01.GIF
Lady Nancy Astor Rev01 FWE 50 lbF Valveless Pulsejet - basic construction dimensions. Drawing Copyright 2007 Larry Cottrill
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ZSartell
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Post by ZSartell » Thu Apr 05, 2007 5:47 pm

Larry, my favorite part is the sweatervest! But besides that the rest looks great. Do you think there are any large restrictions on top speed concerning the intake design?

larry cottrill
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Lady Astor

Post by larry cottrill » Thu Apr 05, 2007 6:08 pm

ZSartell wrote:Larry, my favorite part is the sweatervest! But besides that the rest looks great. Do you think there are any large restrictions on top speed concerning the intake design?
I really don't think so, since his original idea was supposedly for a very high-speed design. The flow past the gap won't be much different from standard pressure (except at high altitude, of course). But, it's all speculation until someone has the wherewithal to build it and check it out.

Yes, I still wear some of my old sweater vests from time to time in winter. It's a good look, I think - like a lot of guys in British movies from the 1940s and early 50s.

L Cottrill

Eric
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Post by Eric » Thu Apr 05, 2007 8:00 pm

What no full size .gif pattern layouts? :P

Hopefully the scaling will work out for you, I have a few suggestions from a construction stand point...

First off, 2 mm stainless is going to be extremely heavy, impossible to cut with any practical cutting tool, and a boat load of fun to form. I would go with 20 gauge stainless with 1/4" round rod support rings at the critical areas for extra support against implosion. With the shroud the engine will also run a lot cooler.

The shell at 1 mm is even way too thick, 24 gauge would cut down on the weight, I would go with something like 24 gauge, or aluminum if you think the shroud is going to increase thrust, you dont want to make it weigh 12 lbs do you?

From a material, and fabrication stand point, the shroud about as much work as building an entire other engine. I think a single cone or just a tube would be much more economical and theres not going to be enough of a thrust increase to justify a constant expansion rate layout made up of many cones.

From the looks of it, the engine would weigh about 25 lbs and the shroud 12, just quick visual guestimation, so the total weight is going to be up there. And stainless isnt cheap, you are probably looking at around $200 in 304 sheet stock just for the engine.

20 gauge aluminum shroud and 20 gauge stainless engine would cut the weight by more than half, along with the material cost.

With the thrust reversal at the intake, the engine is going to get a lot of air flowing around it which will likely make it run quite cool even static even without the shroud, if the TSFC is reasonable 20 gauge stainless should be more than enough.

Eric
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Talking like a pirate does not qualify as experience, this should be common sense, as pirates have little real life experience in anything other than smelling bad, and contracting venereal diseases

larry cottrill
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Heavy Lady

Post by larry cottrill » Thu Apr 05, 2007 8:33 pm

Eric -

Good points! That's exactly the kind of feedback in the early stages that I enjoy getting!

Thanks!

L Cottrill

Berry
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Larry

Post by Berry » Thu Apr 05, 2007 9:19 pm

Larry i think its a beautifull machine to see and if you expect it to run i think it can be made by making pipes smaller that are very close to the measurements you want them to have in your design.
It will be a lot of work but it can de done.

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Mega lady

Post by Irvine.J » Fri Apr 06, 2007 4:18 am

I'll have a crack at this in a few weeks :D :D :D
Doesn't look very "Nancy" to me if you know what I mean HA!
Nice work larry!
I'll even build it wearing that 1950's sweater if i can find one :-)
Few weeks away, but hell that would be so much fun!
(in 0.5mm stainless for me though)
James- Image KEEPING IT REAL SINCE 1982
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larry cottrill
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Go For It!

Post by larry cottrill » Fri Apr 06, 2007 12:29 pm

James I -

Sounds great. You already know from past experience where it is most likely to implode - the middle cone ahead of the choke cone. As Eric points out, you can use some reinforcing rings to help out there.

IF you go to the trouble of fitting the outer shell to it, things will be a lot different. The power of air passing over the engine shell to harvest heat is enormous. I'm one of the few people here who have actually flown a pulsejet (Dynajet) fully exposed to cooling air so it can be observed in flight at speed (90 MPH in my case) at dusk (i.e. the engine shell heat was clearly observable). James, the only part of that engine that got visibly red was the nozzle zone at the very front end of the tailpipe! The only reason that section remained hot was because of the inadequacy of flow around that point - if the engine had been properly shrouded around that area, I'm sure it would have stayed dark, too. The heat that can be picked up this way is just huge, and in this case (Lady Astor), the air is fully driven by the rearward blast from the intake, even in static operation. In the configuration shown here, you should have no implosion worries at all, even with an astoundingly lightweight build. The only real problem with such a light build is that you end up with an engine that has to be carefully handled to prevent accidental damage.

It's good that you have to hold off a little, since I need to develop the details of that intake shell and recuperator. I will try not to dawdle, however, and get it out here for all to see.

L Cottrill

larry cottrill
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Re: Larry

Post by larry cottrill » Fri Apr 06, 2007 12:33 pm

Berry wrote:Larry i think its a beautifull machine to see and if you expect it to run i think it can be made by making pipes smaller that are very close to the measurements you want them to have in your design.
It will be a lot of work but it can de done.
Thanks, Berry! Yes, in an engine this size, a few mm difference here or there is probably meaningless - the exception being the length and exact positioning of that shroud around the intake gap. I'm sure that's the most absolutely critical area to get right for this to work.

L Cottrill

Graham C. Williams
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Post by Graham C. Williams » Sat Apr 07, 2007 12:16 am

Dear Larry.
The original Type07 induction cone is in part designed to create a shock from the tip of the plug to the outer cone edge (when running M>1). This partly pre-compresses the induction air and reduces its velocity. Unfortunately it also increases the losses - I'm sure you know all this stuff.
The motor looks very short to me and the induction pipe looks a little short but again I'm sure you've done the path length sums. Have you run this through NUDiS or just UFLOW? If not I'll have a go.
We noted when running our small Type07 that we could have quite a large main induction pipe dia. provided that the open end was at the correct dia. and the flow was subsonic most of the time (as predicted by the model), this all links back to the work Mike did with his motors when he applied pinches just behind the induction bell mouth. Saying this you may gain some advantage by using 100mm as the main induction dia. and moving the plug a little to restrict the flow thus bringing it all back into tune (I have a notion that that is what was done on the original Type07).
You’ve increased the exhaust dia. beyond the CC dia. what was your rational or have you found another resonance point?

Best
Graham.
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light. Productions begin.
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larry cottrill
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Means and Methods

Post by larry cottrill » Sat Apr 07, 2007 2:27 am

Graham C. Williams wrote:The original Type07 induction cone is in part designed to create a shock from the tip of the plug to the outer cone edge (when running M>1). This partly pre-compresses the induction air and reduces its velocity. Unfortunately it also increases the losses - I'm sure you know all this stuff.
Well, I know more now than I did before ;-) The thing to keep in mind here is that I'm not trying to duplicate the purported high speed performance of the ME engine - I'm just offering this kind of intake because it looks like a really interesting idea. I've always liked this recuperator geometry a lot better than using a big, draggy 180-degree pipe bend. That's all.

Because of this (very non-scientific) motivation, the design is simplified, to a degree. I carefully worked out the curve of the sombrero and its spacing to the intake lip (and the sizing of the lip) to try to provide a roughly constant area path. This is in line with the usual 'straight pipe' intake I modeled in UFLOW.
The motor looks very short to me and the induction pipe looks a little short but again I'm sure you've done the path length sums.
It is short, but so was the Lady Jane Grey. Perhaps I am on too much of a 'compactness' kick. If this results in poor operating efficiencies or other difficulties, I will gladly take all admonishment due. So far, the only problem I personally have with it is that it looks like the cone angles of the chamber and mid cone are getting uncomfortably "blunt", especially the chamber cone.
Have you run this through NUDiS or just UFLOW? If not I'll have a go.
This is simply another re-scaling, with my usual application of UFLOW1D. I do a basic layout that "looks right", then run it in UFLOW to get its idea of the operating frequency and how well it runs out. Then, I split the engine into "mortar" and "flask" quarter-wave resonators, going back and forth with little adjustments until they both resonate at precisely the same frequency (usually a little higher than the original open pipe). Then, I re-combine them to verify that the whole still runs out well. This sounds like it would take days of work, but it doesn't - three or four passes and I've usually got it. I simply have not been able to play with NUDiS enough yet to feel comfortable with it - I need to re-read some of your discussion and so forth.

If I had to divide the intake up into multiple pipes, that would take a lot longer, but in this case, it's just modeled as a single straight intake. Then, a little calculation was done to try to get the 'constant area' geometry worked out between the shortened intake and the sombrero.

If you want to run it in NUDiS, go ahead. You sure haven't hurt my feelings yet ;-) I really need to get used to using that - our friend James I is WAY ahead of me now - he can actually formulate intelligent questions about it ...
We noted when running our small Type07 that we could have quite a large main induction pipe dia. provided that the open end was at the correct dia. and the flow was subsonic most of the time (as predicted by the model), this all links back to the work Mike did with his motors when he applied pinches just behind the induction bell mouth. Saying this you may gain some advantage by using 100mm as the main induction dia. and moving the plug a little to restrict the flow thus bringing it all back into tune (I have a notion that that is what was done on the original Type07).
Again, I hope the flow here is always subsonic and the constant area intake adjustment works well. I realize I am not using Messerscmitt's design to really do what he wanted it to do, but I had no delusions about designing a really high-speed engine.
You’ve increased the exhaust dia. beyond the CC dia. what was your rationale or have you found another resonance point?
The increase is slight, but it bumped the tail volume up enough to significantly improve tail-end massflow without screwing up the basic running out of the motor. Just something I tried at the last minute to see what it would do, and kept it. These severely shortened engines don't end up with any surplus of tail-end volume, so it seemed like an obvious tweak, and I didn't observe any ill effects, just a lot better massflow without a severe velocity penalty, or any skewing of the pressurization. That's all there is to it. It's entirely possible that lengthening the cone slightly would have done the same kind of thing, maybe better, but I didn't want any length increases at this point.

L Cottrill

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Easter

Post by Vermin » Sun Apr 08, 2007 11:27 am

Vern, James, James and Graham -

(Sounds kind of like a law firm, doesn't it?)
NOT LAWYERS that is almost insulting........LOL just hackin on ya
Soooooooo I see the easter Jackalope was here "fast as fast can be"
this is going to be FUN.

A kwik thought, if you place an enclosed shroud over the intake as opposed to the open sided sombrero and duct assy,(the directional inner cone would have to stay for symetrical distrubution) you could increase the initial dia of the augmentor shroud to capture this and still utilize the latent heat for augmentation!

I am not sure what velocity may this configuration be aplicable to without starving the eng, I am assuming that there would be an acceptable positive pressure in this area due to the initial expansion cone of the CC up to 250KPH and probably higher if the shroud was configured correctly?

I will start on the main portions soonest less the intake duct and cone I am really considering 3 "Classic" rear facing intakes for my prortotype (just habit).
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jacklope.gif
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Vern
A desire to destroy as many man made hydrocarbon compounds as possible in one lifetime.

larry cottrill
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Re: Easter

Post by larry cottrill » Mon Apr 09, 2007 12:40 pm

Vermin wrote:A kwik thought, if you place an enclosed shroud over the intake as opposed to the open sided sombrero and duct assy,(the directional inner cone would have to stay for symetrical distrubution) you could increase the initial dia of the augmentor shroud to capture this and still utilize the latent heat for augmentation!
Quite true. It would not be quite as "easy breathing" at speed - but, that is one of the criticisms of all rear-facing intake designs.
I will start on the main portions soonest less the intake duct and cone I am really considering 3 "Classic" rear facing intakes for my prortotype (just habit).
I'll work out what I think that should look like in terms of lengths and sizes. Graham has suggested that the intake area could be increased - that may be based on his observation that the original worked around a narrowed passage area at the lip, though. It looked to me like the 90mm ID pipe was pretty good, though it is a rather long pipe in relation to the chamber cone. Let me see what I can come up with for a three-piper.

L Cottrill

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Post by Graham C. Williams » Mon Apr 09, 2007 1:10 pm

Hi.
I have a combustion run going at the moment. Not much to report so far.
Induction dia.:
I've looked at 90mm dia. induction pipes and 100mm dia induction pipes. Not much difference.
Induction Length:
I started with a model that assumed the whole induction pipe length was equal to the induction pipe path as shown in the drawing. So, the induction pipe was 300mm long. This was way too long; the cold air was not making it into the combustion chamber.
Next, 200mm induction pipe length but 210mm seems to be better.
Rebound Pressure:
The standard rebound pressure is a little bit lower than that reported for the James D.motor.
Location of first Pinch:
I've made a very slight change to the location of the first pinch, thus bringing it into exact alignment with the James D. motor.
I'll report the results in full when the combustion run is over.

Graham.
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Post by Graham C. Williams » Mon Apr 09, 2007 5:06 pm

Thrust>80Lbs when run under the conditions as attached.
If this motor hits this value I'll eat my hat.
Why? I know the system is not very good when the motors are very short.
I'll set-up some more runs and report results.

Graham.
Attachments
Lady Nancy Astor Rev02 Run Conditions.doc
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