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

larry cottrill · Post by **larry cottrill** » Fri Feb 16, 2007 7:38 pm

A fellow who is soon to join these forums was asking me about a 2X scale-up of the Lady Anne Boleyn, which I thought would make an excellent entry into Mike's "32 Inch Chinese" competition - so, here she is, the 'Lady Jane Grey'. Diameters are scaled 2-to-1, longitudinal points are scaled to bring her out to 32 inches physical length. According to UFLOW1D, this one runs out beautifully.

The preliminary design was for a single large intake, but due to the re-scaling of the engine lengths (far shorter than 2:1), the intake produced was short: a 55mm ID pipe only 100mm long! That's not good in terms of pipe Q, so I divided it up into two smaller and slightly shorter elements, exactly the way James D did on his last Lady Anne build. I also added a dimensioned view of the simple 'flattened cone' augmentor shell I recently suggested (rear end circular, front end flattened to a narrow oval). I even included cross-sections at the critical points in the 'heat recovery ramjet' style augmentor to show the approximate values of the net areas I calculated at those stations. This (I hope) illustrates the 'ramjet' characteristic of this augmentor geometry.

If you want to build this with the optional augmentor shell, be SURE to build the basic engine shell in two "halves" - the combustion chamber / intake assembly as the front section and everything else as the rear section. That way, you can easily get the rear section into the augmentor shell after it's formed and flattened, and weld them together. Then, align and weld on the chamber section as the final step. You'll need to provide three or four little webs at the rear to maintain uniform separation.

As usual, you should probably provide a little sliding adjustment to the intake pipes just to make sure you can tune it in. It shouldn't be far from what's shown on the drawing, though.

Have fun!

L Cottrill

Vermin · Post by **Vermin** » Sat Feb 17, 2007 11:31 am

Hi Larry
Wow that was quick...I have downloaded them and will start construction as soon as I have finished the 2X FWE. The dual fuel prototype system worked fine I tried it last eve...some what ugly in its current form but functional nonetheless. As soon as i figure out how to add an image I will place the draft sketch for the system.
Thanks Vern......Oh and Hi Eric

Vermin · Post by **Vermin** » Mon Feb 19, 2007 7:45 pm

I dont know if anyone has tried this format before but the prototype worked well on one of Erics TPC4.25 units. It ran full wack on liquid (50/50 kerosene / methanol) with a poormand injector. I am waiting until Eric gets his lathe fixed for a real one. Larry I can't upload the video here as it is 2.5 megs so I will email it to you (if you would like) advise.
Thanks Vern
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larry cottrill · Post by **larry cottrill** » Mon Feb 19, 2007 8:04 pm

Vern -

Yes, by all means try to send that to me. I actually have no idea whether a file that size will be blocked or not, but we'll hope for the best. I'd certainly like to see it.

I like the combination propane/liquid setup very much. Looks quite sensible to me. And, it features the all-important "quick shutoff" valve at the top. Very nice, I think.

L Cottrill

Vermin · Post by **Vermin** » Wed Feb 28, 2007 10:50 am

Hello Larry and All others.
I have compleated (finally) my 4th unit a TP180 6lb it works excelent although a little ugly with the welds unfinished. And it is time to start this project.

Reading through the other blogs pertaining to similar units there seems to be a bit of an issue (if that is the proper term) with operating frequencys I was just curious if that was because of the choke cone exhaust side angle. The point of reflection appears to be in the center + -of the difuser section. Should (could) the angle be adjusted so the point of reflection is at the widest diameter of the difusser cone. Just curious and maybe I am out to lunch with this concept being a newbie.

Larry if you get a chance can you check this out on your UFlow and see what differance it will make The exhaust will also have to be adjusted and I havent done the math on that yet.

Eric · Post by **Eric** » Wed Feb 28, 2007 12:45 pm

Hey whats up? Nice to see you on the forum here! Thats another nice little engine, keep up the good work.

Was the 180 exactly to dimensions or did you have to use tubing that was a little bit bigger?

If you can make an advanced injector for it, you will have it roaring like you would not believe. I dont know when Im going to be able to get a new lathe.

The wave-flow-thermodynamics of the engine arent really well represented in Uflow.

Any ideas of what your 5th engine is going to be? Interested in building a prototype design? :)

Eric

Irvine.J · Post by **Irvine.J** » Wed Feb 28, 2007 1:14 pm

Nice work Vermin! Great looking engine, I don't think its ugly at all. The 180 is a good choice and looks like you've done really well to get it running. If this is your 4th engine, i'm very impressed :)

Vermin · Post by **Vermin** » Wed Feb 28, 2007 7:08 pm

Hello All
First Larry sorry about the miscalc on the pont of reflection for the choke cone exhaust side, my math sucks at times thats why I have redo it to check, the mean point of reflection is 118.5mm +- and this should put the reflection right at the end of the CC where it should be.

I am hoping to start the LJG unit this weekend..and Eric sure I would be willing to take on another unit to prototype.

Eric I ended up using 1.5OD heavy wall exhaust tube that was bent on an exhaust forming unit, no where near as good as mandrel but close enough, it sort of compresses and draws the tube so the ID eneded up at just under 1.3". and I had to use 2 X 90 and join them for the 180..just part of using what is available.

So the lathe is totaly frigged?? dam ...does anyone out there have a small injector they are willing to part with?

Thanks for the compliments folks ...this is the most fun since designing, building and racing Drag Bikes .... will keep all informed with progress.

larry cottrill · Post by **larry cottrill** » Thu Mar 01, 2007 2:11 pm

Vermin wrote:First Larry sorry about the miscalc on the pont of reflection for the choke cone exhaust side, my math sucks at times thats why I have redo it to check, the mean point of reflection is 118.5mm +- and this should put the reflection right at the end of the CC where it should be.

No problem ... I wasn't worried ;-) The thing that always makes pulsejets tricky is the wide gas temperature gradients along the length. And of course, that's where possible errors in guestimating come into play, adversely affecting any design calculation. This wide temperature range is the reason I consider the "half wave open pipe" model so inadequate - sure, it's "technically" correct, but doesn't logically lead to the right conclusion as to how the pressure wave behaves (or the resulting gas speeds, for that matter). Naturally, I consider my synchronized quarter-wave 'flask and mortar' model to be vastly superior in every way ;-) At least this model is a (presumably) logical way to isolate the engine into its two basic functional parts: A small cold section (slow wave transit, low mass) that "fully" purges the combustion product, and a large hot section (fast wave transit, high mass) that does not. I think that once that concept is understood, a lot of the basic internal action (especially the wave mechanics) becomes clear.

I am hoping to start the LJG unit this weekend...

Man - I can't wait to see it happen! Good luck with her!

L Cottrill

Vermin · Post by **Vermin** » Fri Mar 02, 2007 3:23 am

Better pics and vid's
Thanks All

Vermin · Post by **Vermin** » Sat Mar 03, 2007 4:16 pm

OK folks the trial by fire is over..
0730hrs Sat, parts laying arround 2" chrome pipe, old dispoable propane tank 3/4" emt radius 90....hmmmmmmmmm

cut weld cut weld

0930 test fire the PT100 (I had to call it something) no spark plug just air and a propane torch....game over

1000hrs, aluminum augmentor time..... works fine. whoohooo

If I can do this I can build Larrys prototype..confidence builds.

Larry I used the theory for scavenging 2 cycle engine cylinders for placement and angles of the 2 intakes @ 90 seems to work OK by the looks of the heat patterns...I will send a vid for you to check out..Thanks and.....

Thanks to all for info on this site......

PS The dam rivets in the augmentor laste about 10min....thas OK just a trial.

Vermin · Post by **Vermin** » Mon Mar 05, 2007 1:33 am

OK folks Here She is ..or what is done so far......shaping up nicely... Oh the beer was to quench the parched portion after all the welding and cutting and such.......

larry cottrill · Post by **larry cottrill** » Mon Mar 05, 2007 5:16 pm

Vern -

Well ... she looks mighty nice to me!

Good luck with those intakes! Also, however you want to do them, make sure your engine mounts are good and solid ... lots of shear area distributed in the longitudinal direction.

L Cottrill

Vermin · Post by **Vermin** » Tue Mar 06, 2007 10:44 am

Larry
I have used 2mm MS for this unit quite a bit tougher to form but weight is not a concern, although dimensions may suffer slightly.

I have attached a couple of sketches of mounts, I prefer the angle unit as it provides more support, sugestions please.

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, I dont think this should be an issue! I will place them @ 180 as per plans.

I will have to come up with a test stand soon...more shade tree eng...ahhhh but it works.
Take care

Eric · Post by **Eric** » Tue Mar 06, 2007 2:37 pm

I would make a cone section so that when the engine pushes forward, it pushes evenly around the whole cone distributing all the force evenly, and then from that point have two arms with sliding suport brackets. Dont make more than one rigid mounting point or the engine will bend itself.

Eric

www.pulse-jets.com